WO2024065286A1 - 正极活性材料、正极极片、电化学储能装置、二次电池、用电装置和制备方法 - Google Patents

正极活性材料、正极极片、电化学储能装置、二次电池、用电装置和制备方法 Download PDF

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WO2024065286A1
WO2024065286A1 PCT/CN2022/122177 CN2022122177W WO2024065286A1 WO 2024065286 A1 WO2024065286 A1 WO 2024065286A1 CN 2022122177 W CN2022122177 W CN 2022122177W WO 2024065286 A1 WO2024065286 A1 WO 2024065286A1
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particles
optionally
positive electrode
electrode active
active material
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French (fr)
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李圣
倪欢
钟华
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to PCT/CN2022/122177 priority Critical patent/WO2024065286A1/zh
Priority to EP22959932.9A priority patent/EP4481852A4/en
Priority to CN202280088165.1A priority patent/CN118511321B/zh
Publication of WO2024065286A1 publication Critical patent/WO2024065286A1/zh
Priority to US18/941,737 priority patent/US20250070155A1/en
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    • C01G53/502—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2 containing lithium and cobalt
    • C01G53/504—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2 containing lithium and cobalt with the molar ratio of nickel with respect to all the metals other than alkali metals higher than or equal to 0.5, e.g. Li(MzNixCoyMn1-x-y-z)O2 with x ≥ 0.5
    • C01G53/506—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2 containing lithium and cobalt with the molar ratio of nickel with respect to all the metals other than alkali metals higher than or equal to 0.5, e.g. Li(MzNixCoyMn1-x-y-z)O2 with x ≥ 0.5 with the molar ratio of nickel with respect to all the metals other than alkali metals higher than or equal to 0.8, e.g. Li(MzNixCoyMn1-x-y-z)O2 with x ≥ 0.8
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Definitions

  • the present application relates to the fields of energy technology and secondary battery technology, and further to positive electrode active materials, positive electrode plates, electrochemical energy storage devices, secondary batteries, electrical devices and preparation methods.
  • High-nickel materials (such as high-nickel ternary materials, etc.) have the characteristics of high capacity and low cycle attenuation, and have attracted widespread attention in the industry. However, the high watt-hour cost of high-nickel materials currently restricts their promotion and application.
  • the present application provides a positive electrode active material, a positive electrode plate, an electrochemical energy storage device, a secondary battery, an electrical device and a preparation method.
  • the positive electrode active material is a high-nickel positive electrode material, having small particles and large particles with a specific structure, and the content of small particles is higher than that of large particles.
  • the prepared positive electrode plate has a high mass specific capacity and excellent structural stability. Furthermore, at the battery cell level, the mass energy density and cycle life of the battery cell can be significantly improved, and the side reactions with the electrolyte can be reduced, thereby reducing the gas production of the battery cell.
  • the present application provides a positive electrode active material, comprising A particles and B particles, wherein the molar ratio of nickel element to lithium element in the A particles and the B particles R Ni/Li is independently ⁇ 0.33; wherein the A particles have a single crystal or a quasi-single crystal structure, and the B particles are secondary particles including a plurality of primary particles, wherein the D v 50 of the A particles is less than the D v 50 of the B particles, and the mass proportion of the A particles is greater than or equal to the mass proportion of the B particles;
  • D v N represents the particle size corresponding to when the cumulative volume distribution percentage of the material reaches N%, and N is a value selected from 0 to 100.
  • the positive electrode active material includes high-nickel positive electrode materials of different particle sizes, wherein D v 50 Small particles and large particles are distinguished, A particles with a single crystal or quasi-single crystal structure are used as small particles, and B particles formed by the aggregation of primary particles are used as large particles, and the mass content of A particles is controlled to be higher than that of B particles; A particles with a special crystal phase structure have a homogeneous system or a nearly homogeneous phase.
  • B particles are formed by the aggregation of primary particles, which is conducive to improving power performance and compaction density.
  • the stress caused by the contraction and expansion of the large particle lattice can be reduced, thereby avoiding the positive electrode material from cracking under high voltage conditions, avoiding the formation of new interfaces due to the rupture of the material, and then avoiding the new interface from reacting with the electrolyte to cause the deterioration of the battery cell performance and the increase of gas production, thereby enhancing the cycle stability under high voltage conditions and extending the service life of the battery cell;
  • the increase in the content of small-sized A particles is also conducive to improving the storage capacity retention rate of the battery cell and increasing the storage calendar life of the material.
  • the small-sized A particles adopt a pure single crystal system. Compared with the mixed system, the material's electrode density and battery cell power performance will be significantly reduced.
  • the increase in the compaction density of the electrode can increase the material's volumetric capacity, allowing the battery cell to have a longer battery life in a smaller volume.
  • the particle size of the A particles satisfies 2 ⁇ m ⁇ D v 50 ⁇ 5 ⁇ m, and the particle size of the B particles satisfies 5 ⁇ m ⁇ D v 50 ⁇ 25 ⁇ m;
  • the Span value of the A particles is selected from 0.1 to 3.0; the Span value of the B particles is selected from 0.1 to 3.0;
  • the particle size of the B particles satisfies 8 ⁇ m ⁇ D v 50 ⁇ 20 ⁇ m.
  • each of the A particles and the B particles By controlling the particle size of each of the A particles and the B particles within a more appropriate range, it is beneficial to better improve the high-voltage tolerance of the positive electrode material, reduce the stress caused by large particles, and thus better avoid the cracking of the positive electrode material under high voltage conditions, enhance the cycle stability under high voltage conditions, avoid the aggravation of gas production, and extend the service life of the battery cell. Further, it is also more conducive to improving the specific capacity and mass energy density of the positive electrode plate.
  • the wider the particle distribution of the material is in terms of distribution.
  • the compaction density of the material plate can be made higher, which is more conducive to improving the volume specific capacity of the material, so that the battery cell has a longer endurance in a smaller volume.
  • the B particles include B1 particles and B2 particles, wherein the particle size of the B1 particles satisfies 5 ⁇ m ⁇ D v 50 ⁇ 10 ⁇ m, and the particle size of the B2 particles satisfies 10 ⁇ m ⁇ D v 50 ⁇ 25 ⁇ m;
  • the weight proportion of the B1 particles in the B particles is selected from 50% to 100%;
  • the weight proportion of the B2 particles in the B particles is selected from 0% to 50%;
  • B particles are further divided into B1 particles and B2 particles, so that the D v 50 of B1 particles is smaller than the D v 50 of B2 particles.
  • the positive electrode active material can include particles of three size grades, and the particle size of larger-sized particles can be more finely controlled; further, by reasonably controlling the proportion of particles of different sizes and the widening coefficient Span, while improving the compaction density and enhancing the specific capacity and mass energy density of the positive electrode plate, the power performance can be better improved by reasonably controlling the content of intermediate-sized B1 particles, avoiding excessive dense stacking that affects the wettability of the electrolyte, avoiding the electrolyte from being unable to contact the internal active material of the plate to cause concentration difference and thereby adversely restricting lithium ion transmission.
  • the B particles include B1' particles, B2' particles and B3' particles, wherein the particle size of the B1' particles satisfies 8 ⁇ m ⁇ D v 50 ⁇ 12 ⁇ m, the particle size of the B2' particles satisfies 12 ⁇ m ⁇ D v 50 ⁇ 15 ⁇ m, and the particle size of the B3' particles satisfies 15 ⁇ m ⁇ D v 50 ⁇ 20 ⁇ m;
  • the weight proportion of the B1' particles in the B particles is selected from 40% to 80%;
  • the weight proportion of the B2' particles in the B particles is selected from 20% to 30%;
  • the weight proportion of the B3' particles in the B particles is selected from 0% to 30%;
  • the Span value of the A particles is selected from 0.1 to 2.0
  • the Span value of the B1' particles is selected from 0.1 to 2.0
  • the Span value of the B2' particles is selected from 0.1 to 2.0
  • B particles are further divided into B1' particles, B2' particles and B3' particles with increasing D v 50 in sequence, so that the positive electrode active material includes four size-graded particles, and the particle size of larger-sized particles is more finely controlled; further, by reasonably controlling the proportions of the four and the widening coefficient Span, the power performance can be better improved by reasonably controlling the content of B1' particles and B2' particles of intermediate sizes, which can avoid excessive dense stacking that affects the wettability of the electrolyte, avoid the electrolyte from being unable to contact the internal active materials of the electrode to produce concentration differences, and thus avoid adverse restrictions on lithium ion transmission.
  • the A particles and the B particles each independently comprise the following element combination Ni x Co y M 1-xy , wherein x ⁇ 0.4, y ⁇ 0, (1-xy) ⁇ 0; the M element comprises one or both of Mn and Al;
  • the A particles and the B particles each independently include a material with a chemical formula of Li ka Q a (Ni x Co y M 1-xy ) 1-z N z O 2-c X c , wherein 0.9 ⁇ k ⁇ 1.1, 0 ⁇ a ⁇ 0.2, 0.60 ⁇ x ⁇ 1.00, 0 ⁇ y ⁇ 0.15, 0 ⁇ (1-xy), 0 ⁇ z ⁇ 0.5, 0 ⁇ c ⁇ 1, the M element includes one or both of Mn and Al, the Q element includes one or more of Na, K, Rb and Ca, the N element includes one or more of Al, Ti, Zr, Nb, Sr, Sb, Y, Ba, Co, Mn, Mg, W, Si, Mo, P and C, and the X element includes one or more of B, F, S and Cl;
  • the nickel-lithium molar ratio R Ni/Li in the A particles and the B particles is independently ⁇ 0.4;
  • the nickel-lithium molar ratio R Ni/Li in the A particles and the B particles is independently ⁇ 0.5;
  • the nickel-lithium molar ratio R Ni/Li in the A particles and the B particles is independently ⁇ 0.6;
  • the nickel-lithium molar ratio R Ni/Li in the A particles and the B particles is independently ⁇ 0.7;
  • the nickel-lithium molar ratio R Ni/Li in the A particles and the B particles is independently ⁇ 0.8;
  • the nickel-lithium molar ratio R Ni/Li in the A particles is selected from 0.7 to 1.0;
  • the nickel-lithium molar ratio R Ni/Li in the B particles is selected from 0.8 to 1.0;
  • the nickel-lithium molar ratio R Ni/Li in the B particles is selected from 0.8 to 0.96.
  • the unit cell parameters of traditional nickel-rich positive electrode materials (such as nickel-rich ternary positive electrode materials, etc.) will change with the occurrence of lithium intercalation and deintercalation.
  • the change of unit cell parameters will cause internal stress in the material.
  • the internal stress of the material continues to accumulate, which in turn causes the material to undergo structural phase change and particle cracking, which will greatly damage the reversible cycle of the material.
  • the degree of lithium intercalation and deintercalation of nickel-rich materials (such as nickel-rich ternary materials, etc.) will be further deepened.
  • the positive electrode active material can adopt a traditional nickel-rich ternary positive electrode material.
  • the doping of N elements can also be introduced into the ternary positive electrode active material, which can reduce the degree of lattice change of the material and play a role in stabilizing the lattice, thereby improving the cycle performance of the nickel-rich ternary material.
  • the true density of the A particles and the B particles is independently greater than 4.0 g/cc;
  • the true density of the A particles and the B particles are each independently selected from 4.0 g/cc to 4.8 g/cc;
  • the true density of the A particles is independently selected from 4.6 g/cc to 4.8 g/cc;
  • the true density of the B particles is each independently selected from 4.5 g/cc to 4.8 g/cc.
  • true density is one of the main factors that determine the compaction density of the positive electrode material.
  • the A particles and the B particles each independently include a body structure and an oxide layer covering at least a portion of a surface of the body structure;
  • the bulk structure includes a material having a chemical formula of Li k1-a1 Q a1 (Ni x1 Co y1 M 1-x1-y1 ) 1-z1 N z1 O 2 , wherein 0.9 ⁇ k1 ⁇ 1.1, 0 ⁇ a1 ⁇ 0.20, 0.40 ⁇ x1 ⁇ 1.00, 0 ⁇ y1 ⁇ 0.15, 0 ⁇ (1-x1-y1), 0 ⁇ z1 ⁇ 0.5, and the Q element includes one or more of Na, K, Rb and Ca, the M element includes one or two of Mn and Al, and the N element includes one or more of Al, Ti, Zr, Nb, Sr, Sb, Y, Ba, Co, Mn, Mg, Si, P, Mo, C and W;
  • k1 is equal to 1;
  • the N element includes one or more of Al, Ti, Zr, Nb, Sr, Sb, Y, Mg and W;
  • the oxide layer includes a material with a chemical formula of Li k2-a2 Q' a2 (Ni x2 Co y2 M' 1-x2-y2 ) 1-z2 N' z2 O 2-c2 X c2 , wherein 0 ⁇ a2 ⁇ 0.20, 0.40 ⁇ x2 ⁇ 1.00, 0 ⁇ y2 ⁇ 0.15, 0 ⁇ (1-x2-y2), 0 ⁇ z2 ⁇ 0.5, 0 ⁇ c2 ⁇ 1, and the Q' element includes one or more of Na, K, Rb and Ca, the M' element includes one or two of Mn and Al, the N' element includes one or more of Al, Ti, Zr, Nb, Sr, Sb, Y, Ba, Co, Mn, Mg, W, Mo, Si, C and P, and the X element includes one or more of B, Cl, S and F;
  • k2 is equal to 1;
  • Q'a2Nix2Coy2M'1 -xy is the same as Qa1Nix1Coy1M1 - x1 -y1 ;
  • the N' element includes one or more of Al, Ti, Zr, Sr, Sb, Mo, Nb, Mg, Y and W;
  • Q' elements can be doped in the bulk structure of the positive active material to increase the lithium ion diffusion coefficient and reduce the lithium nickel mixing. It is also possible to coat the surface of the positive active material to form an oxide layer doped with a specific N' element on the surface of the particle, which can reduce the surface reactivity of the material with the electrolyte, reduce the oxygen release of the material, improve the structural stability of the active material, improve the ionic conductivity, and also improve the material capacity.
  • the oxide layer by doping Zr, Al, Mg, W, Mo, Co, Sr, Sb, Nb and other elements in the oxide layer, among which Mg, Ti, Al and Mo and other elements can reduce the amount of lattice deformation of the material during the charge and discharge cycle, thereby improving the structural stability of the material; for example, elements such as B, F and Cl can also be doped into the oxide layer to improve the capacity and rate performance.
  • the material can also have a higher specific capacity, and at the same time reduce the degree of side reactions and phase changes between the positive electrode material and the electrolyte, so that the battery has a lower watt-hour cost and a higher cycle life.
  • the material interface without a coating is likely to undergo a large number of side reactions with the electrolyte, causing the electrolyte to be oxidized to produce gases such as carbon dioxide and oxygen; moreover, when there is no coating, the layered structure on the surface of the positive electrode active material is more likely to transform into a rock salt structure, causing the material surface to lose its chemical reactivity.
  • the thickness of the oxide layer is 0 to 100 nm
  • the thickness of the oxide layer is 1 nm to 100 nm;
  • the oxide layer has a thickness of 1 nm to 20 nm.
  • the mass percentage of the oxide layer relative to the bulk structure is 0.01% to 5%
  • the mass percentage of the oxide layer relative to the main structure is 0.05% to 4%.
  • the mass proportion of the N element in the oxide layer in the positive electrode active material is 0.01% to 4%;
  • the mass proportion of the N element in the oxide layer in the positive electrode active material is 0.05% to 4%.
  • the aforementioned doping and coating purposes can be better achieved, the chemical reaction activity and structural stability of the material can be better adjusted, the particle size design of the material can be better combined with the structural design, and at the same time, the material can be given a higher specific capacity, the degree of side reactions and phase changes between the positive electrode material and the electrolyte can be reduced, and the battery can have a lower watt-hour cost and a higher cycle life.
  • the average specific surface area of the positive electrode active material is 0.3 cm 2 /g to 1.5 cm 2 /g.
  • the free lithium content in the positive electrode active material is less than 3000 ppm, calculated by mass ratio.
  • the free lithium (such as lithium carbonate, lithium hydroxide, etc.) content in the positive electrode active material can be reasonably controlled to avoid excessive gas production during the cycle under high voltage conditions. If the free lithium is too high, it will react with the hydrofluoric acid produced by the decomposition of the electrolyte during the cycle under high voltage conditions to produce a large amount of gas, causing the battery cell to swell and bulge, affecting the battery cell and easily causing battery cell safety accidents.
  • the free lithium such as lithium carbonate, lithium hydroxide, etc.
  • the ratio of the I003 grain content to the I104 grain content of the positive electrode active material is I003/I104 ⁇ 1.2, measured as the ratio of the characteristic peak area of the I003 crystal plane to the I104 crystal plane in the XRD spectrum;
  • I003/I104 is selected from 1.2 to 2;
  • I003/I104 is selected from 1.3 to 2;
  • I003/I104 is selected from 1.3 to 1.6.
  • the degree of lithium-nickel mixing can be better controlled to avoid excessive nickel elements occupying the lithium lattice position, which leads to a decrease in reversible capacity and a decrease in the diffusion coefficient of lithium ions.
  • the B particles in the B particles, at least a portion of the primary particles are oriented and arranged along the radial direction.
  • the primary particles can be arranged in a certain direction in the radial direction, thereby suppressing the shrinkage and expansion that may occur under high voltage, avoiding the increase of internal stress, and better preventing the material from breaking under high voltage.
  • the cycle performance can be improved. The higher the degree of radial directional arrangement, the lower the degree of random arrangement, and the more obvious the improvement of the effect.
  • the present application provides a positive electrode plate, which includes a positive electrode collector and a positive electrode active material layer located on at least one surface of the positive electrode collector, wherein the positive electrode active material layer includes the positive electrode active material described in the first aspect of the present application.
  • the positive electrode active material of the first aspect of the present application can be used to prepare positive electrode plates with a high nickel content.
  • the particle size and content of the positive electrode active material can be designed to avoid cracking of the material under high voltage, thereby improving the battery cell cycle and storage performance under high voltage conditions.
  • the chemical reaction activity and structural stability of the material can be further adjusted by doping and/or coating structure design, so that the material has a higher specific capacity, while reducing the degree of side reactions and phase changes between the positive electrode material and the electrolyte, so that the battery has a lower watt-hour cost and a higher cycle life.
  • the compaction density of the positive electrode sheet is 3.3 g/cm 3 to 3.7 g/cm 3 .
  • the compaction density of the positive electrode sheet is also limited by the true density of the A particles and B particles contained therein.
  • the improvement of the compaction density of the electrode sheet can increase the volumetric specific capacity of the material, so that the battery cell has a longer battery life in a smaller volume.
  • the present application provides an electrochemical energy storage device, which includes the positive electrode plate, the negative electrode plate and the isolation membrane described in the second aspect of the present application, wherein the isolation membrane is arranged between the positive electrode plate and the negative electrode plate.
  • the present application provides a secondary battery comprising at least one of the positive electrode plate described in the second aspect of the present application and the electrochemical energy storage device described in the third aspect of the present application.
  • the present application provides an electrical device, which includes at least one of the positive electrode plate described in the second aspect of the present application, the electrochemical energy storage device described in the third aspect of the present application, and the secondary battery described in the fourth aspect of the present application.
  • the positive electrode active material of the first aspect of the present application is used to prepare a positive electrode plate with a high nickel content, and then to prepare an electrochemical energy storage device, a secondary battery, and an electrical device.
  • the particle size and content of the positive electrode active material can be designed to avoid cracking of the material under high voltage, improve the battery cell cycle and storage performance under high voltage conditions, and further use the doping and/or coating structure design to adjust the chemical reaction activity and structural stability of the material, so that the material has a higher specific capacity, while reducing the degree of side reactions and phase changes between the positive electrode material and the electrolyte, so that the battery has a lower watt-hour cost and a higher cycle life.
  • a method for preparing a positive electrode active material comprising the following steps: mixing the A particles and the B particles according to a preset mass ratio to prepare the positive electrode active material; the A particles and the B particles are as defined in the first aspect of the present application;
  • the A particles are prepared by a method comprising the following steps: lithium hydroxide, a nickel-cobalt M-body precursor material Ni x Co y M 1-xy (OH) 2 , and an optional Q additive and an optional N additive are mixed, and a primary sintering is performed in the presence of oxygen and at a temperature T1; optionally, at least one of an X additive and an N additive is added to the primary sintered product, mixed, and a secondary sintering is performed in the presence of oxygen;
  • the B particles are prepared by a method comprising the following steps: lithium hydroxide, a nickel-cobalt M-body precursor material Ni x Co y M 1-xy (OH) 2 , and an optional Q additive and an optional N additive are mixed, and a primary sintering is performed in the presence of oxygen and at a temperature T2; optionally, at least one of an X additive and an N additive is added to the primary sintered product, mixed, and a secondary sintering is performed in the presence of oxygen;
  • the Q additive, N additive, and X additive are additives containing Q element, N element, and X element, respectively;
  • x, y, M element, Q element, X element and N element are as defined in the first aspect of the present application;
  • the temperature T1 is higher than the temperature T2;
  • the primary sintering temperature is 700°C to 950°C, optionally 750°C to 900°C, and the secondary sintering temperature is 300°C to 600°C, optionally 350°C to 550°C;
  • the primary sintering temperature is 700°C to 900°C, optionally 750°C to 850°C, and the secondary sintering temperature is 300°C to 600°C, optionally 350°C to 550°C.
  • the precursor of the main structure is sintered in an oxidizing atmosphere and at a relatively high temperature (such as A particles at 700°C to 950°C, and B particles at 700°C to 900°C) to form a main structure, and then mixed with the coating layer additive in an oxidizing atmosphere and sintered at a relatively low temperature (such as 300°C to 600°C) to form an oxide layer, thereby preparing A particles or B particles with a coating layer.
  • a relatively high temperature such as A particles at 700°C to 950°C, and B particles at 700°C to 900°C
  • a relatively low temperature such as 300°C to 600°C
  • the particles inside the particles are easily connected. Therefore, at a relatively high primary sintering temperature (T1), the particles can be fully connected to prepare large-sized single crystals or quasi-single crystal particles (A particles), and small-sized secondary particles (B particles) can be prepared at a relatively low primary sintering temperature (T2). At this time, the fine particles in the secondary particles are not connected or only partially connected.
  • FIG1 is a schematic diagram of the structure of particles A and B in one embodiment of the present application, wherein particles A have a single crystal or quasi-single crystal structure, and particles B are secondary particles including a plurality of primary particles; particles A and B in (a) have no coating layer, and particles A and B in (b) have coating layers;
  • FIG2 is a SEM image (displayed at 1000 times) of the A particle material in one embodiment of the present application, where the scale bar is 20 ⁇ m;
  • FIG3 is a SEM image (displayed at 10,000 times magnification) of the A particle material in one embodiment of the present application, where the scale bar is 2 ⁇ m;
  • FIG4 is a SEM image (displayed at 1000 times) of the B particle material in one embodiment of the present application, where the scale bar is 20 ⁇ m;
  • FIG5 is a SEM image (displayed at 10,000 times magnification) of the B particle material in one embodiment of the present application, where the scale bar is 2 ⁇ m;
  • FIG6 is a cross-sectional SEM image of a B particle raw material in an embodiment of the present application, where the scale is 3 ⁇ m;
  • FIG. 7 is a schematic diagram of the structure of a positive electrode sheet in an embodiment of the present application, wherein the D v 50 of particles A is less than the D v 50 of particles B, and the mass proportion of particles A is greater than or equal to the mass proportion of particles B;
  • FIG. 8 is a schematic diagram of the structure of a positive electrode sheet in an embodiment of the present application, which includes A particles, B1 particles and B2 particles, the D v 50 of A particles, B1 particles and B2 particles increase in sequence, and the mass proportion of A particles is greater than or equal to the sum of the mass proportions of B1 particles and B2 particles;
  • FIG9 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG10 is an exploded view of the secondary battery of one embodiment of the present application shown in FIG9 ;
  • FIG. 11 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application.
  • range disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range.
  • the range defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60-120 and 80-110 is listed for a specific parameter, it is understood that the range of 60-110 and 80-120 is also expected.
  • the numerical range "a-b" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers.
  • the numerical range "0-5" represents that all real numbers between "0-5" have been fully listed herein, and "0-5" is just the abbreviation of these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • the method may further include step (c), which means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
  • the “include” and “comprising” mentioned in this application represent open-ended or closed-ended expressions.
  • the “include” and “comprising” may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.
  • the term "or” is inclusive.
  • the phrase “A or B” means “A, B, or both A and B”.
  • any of the following conditions satisfies the condition "A or B”: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).
  • first”, “second”, “third”, “fourth”, etc. in “the first aspect”, “the second aspect”, “the third aspect”, “the fourth aspect”, etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features.
  • first”, “second”, “third”, “fourth”, etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.
  • room temperature generally refers to 4°C to 35°C, preferably 20°C ⁇ 5°C. In some embodiments of the present application, room temperature refers to 20°C to 30°C.
  • the mass or weight of the relevant components mentioned in the specification of the embodiments of the present application may not only refer to the content of each component, but also indicate the proportional relationship of the mass or weight between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the specification of the embodiments of the present application, it is within the scope disclosed in the specification of the embodiments of the present application.
  • the mass or weight described in the specification of the embodiments of the present application may be a mass or weight unit known in the chemical industry such as ⁇ g, mg, g, kg, etc.
  • high nickel materials such as high nickel ternary materials, etc.
  • the current high nickel material has a high watt-hour cost, which restricts its promotion and application.
  • One of the effective means to reduce the watt-hour cost of materials is to improve the mass energy density of materials.
  • the commonly used methods to improve the mass energy density of high nickel materials mainly include increasing the charge and discharge voltage and increasing the nickel content in the positive electrode material. Due to the extremely high price of positive electrode raw materials, increasing the charge and discharge voltage of the material has become the most attractive way to improve the mass energy density of the material.
  • the nickel-rich positive electrode material (such as nickel-rich ternary positive electrode material, etc.) embeds and extracts lithium ions during the cycle, causing the material lattice to shrink and expand, especially under high voltage conditions, the degree of material shrinkage and expansion deepens, the material is prone to rupture, and the fresh interface positive electrode produced by the rupture has a side reaction with the electrolyte, causing the performance of the battery cell to deteriorate.
  • the positive electrode is more oxidizing, and it is easy to oxidize the organic solvent in the electrolyte to generate gases such as carbon dioxide and oxygen, resulting in an increase in the gas production of the battery cell.
  • a high voltage condition refers to a voltage ⁇ 4.3V.
  • the present application provides a positive electrode active material, which includes A particles and B particles, wherein the molar ratio of nickel element to lithium element in the A particles and the B particles (which can be recorded as the nickel-lithium molar ratio R Ni/Li ) is independently ⁇ 0.33; wherein the A particles have a single crystal or a quasi-single crystal structure, and the B particles are secondary particles including a plurality of primary particles, wherein the D v 50 of the A particles is less than the D v 50 of the B particles, and the mass proportion of the A particles is greater than or equal to the mass proportion of the B particles;
  • D v N represents the particle size corresponding to when the cumulative volume distribution percentage of the material reaches N%, and N is a value selected from 0 to 100.
  • FIG. 1( a ) The structures of the A particles and the B particles in the aforementioned positive electrode active material can be seen in FIG. 1( a ).
  • nickel-rich and “high nickel” have the same meaning and can be used interchangeably, referring to a high proportion of nickel in the positive electrode active material.
  • the molar ratio of nickel, cobalt and manganese is 80:10:10.
  • Increasing the nickel content in the positive electrode active material is beneficial to improving energy density and battery capacity.
  • the molar ratio of nickel element to lithium element can be used to characterize the nickel content, and the molar ratio can be called the nickel-lithium molar ratio, which can be recorded as R Ni/Li .
  • each occurrence of R Ni/Li can be independently greater than or equal to 0.33, further can be independently greater than or equal to 0.4, further can be independently greater than or equal to 0.5, further can be independently greater than or equal to 0.6, further can be independently greater than or equal to 0.7, and further can be independently greater than or equal to 0.8.
  • the nickel-lithium molar ratio R Ni/Li can also be selected from any of the following values or an interval consisting of any two values: 0.33, 1/3, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.02, 0.05, 0.9, 0.95, 1, etc.
  • the nickel-lithium molar ratio R Ni/Li can also be selected from any of the following numerical ranges (any numerical endpoints here may be independently included or excluded): 0.4-1, 0.5-1, 0.6-1, 0.7-1, 0.8-1, 0.8-0.96, etc.
  • the volume cumulative distribution particle size D v N (wherein N represents any value selected from 0 to 100) can be used to characterize the particle size of the material, which refers to the particle size corresponding to the cumulative volume distribution percentage of the material reaching N%, and the volume proportion of the particle size less than or equal to D v N is N%.
  • D v N can be obtained from the volume cumulative distribution curve of the material particle size. Unless otherwise specified, the volume cumulative distribution curve starts from zero from the small particle size side.
  • D v 99 refers to the particle size corresponding to the cumulative volume distribution percentage of the material reaching 99%
  • D v 90 refers to the particle size corresponding to the cumulative volume distribution percentage of the material reaching 90%
  • D v 50 refers to the particle size corresponding to the cumulative volume distribution percentage of the material reaching 50%
  • D v 10 refers to the particle size corresponding to the cumulative volume distribution percentage of the material reaching 10%.
  • D v 50 it means that the particle size of particles accounting for 50% of the volume of the material is less than or equal to D v 50, and the particle size of particles accounting for 50% of the volume of the material is greater than D v 50.
  • D v 90 it means that the particle size of particles accounting for 90% of the volume of the material is less than or equal to D v 90, and the particle size of particles accounting for 10% of the volume of the material is greater than D v 90.
  • D v 10 it means that the particle size of particles accounting for 10% of the volume of the material is less than or equal to D v 10, and the particle size of particles accounting for 90% of the volume of the material is greater than D v 10.
  • the particle size distribution laser diffraction method according to GB/T 19077-2016 can be referred to, and the particle size distribution can be conveniently measured using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer and the LS-909 laser particle size analyzer (OMEC) from Malvern Instruments Ltd., UK.
  • a laser particle size analyzer such as the Mastersizer 2000E laser particle size analyzer and the LS-909 laser particle size analyzer (OMEC) from Malvern Instruments Ltd., UK.
  • quasi-single crystals generally refer to primary particles with a size greater than 1 ⁇ m, but with some agglomeration of the primary particles; single crystals generally refer to primary particles with a size greater than 1 ⁇ m and without obvious agglomeration.
  • primary particles and “secondary particles” are terms well known in the art.
  • Primary particles refer to single crystal grains.
  • Secondary particles refer to particles in agglomerated form by aggregation of two or more primary particles. Primary particles and secondary particles can be easily distinguished by taking SEM images using a scanning electron microscope.
  • the positive electrode active material includes high-nickel positive electrode materials of different particle sizes, wherein D v 50 Small particles and large particles are distinguished, A particles with a single crystal or quasi-single crystal structure are used as small particles, and B particles formed by the aggregation of primary particles are used as large particles, and the mass content of A particles is controlled to be higher than that of B particles; A particles with a special crystal phase structure have a homogeneous system or a nearly homogeneous phase.
  • B particles are formed by the aggregation of primary particles, which is conducive to improving power performance and compaction density.
  • the stress caused by the contraction and expansion of the large particle lattice can be reduced, thereby avoiding the positive electrode material from cracking under high voltage conditions, avoiding the formation of new interfaces due to the rupture of the material, and then avoiding the new interface from reacting with the electrolyte to cause the deterioration of the battery cell performance and the increase of gas production, thereby enhancing the cycle stability under high voltage conditions and extending the service life of the battery cell;
  • the increase in the content of small-sized A particles is also conducive to improving the storage capacity retention rate of the battery cell and increasing the storage calendar life of the material.
  • the small-sized A particles adopt a pure single crystal system. Compared with the mixed system, the material's electrode density and battery cell power performance will be significantly reduced.
  • the increase in the compaction density of the electrode can increase the material's volumetric capacity, allowing the battery cell to have a longer battery life in a smaller volume.
  • the particle size of the A particles satisfies 2 ⁇ m ⁇ D v 50 ⁇ 5 ⁇ m
  • the D v 50 of the A particles can also be selected from any one or two of the following particle sizes: 2 ⁇ m, 2.5 ⁇ m, 3 ⁇ m, 3.5 ⁇ m, 4 ⁇ m, 4.5 ⁇ m, 5 ⁇ m, etc.
  • the particle size of the B particles satisfies 5 ⁇ m ⁇ D v 50 ⁇ 25 ⁇ m
  • the D v 50 of the B particles can also be selected from any one of the following particle sizes or any two intervals: 5.1 ⁇ m, 5.2 ⁇ m, 5.3 ⁇ m, 5.4 ⁇ m, 5.5 ⁇ m, 6 ⁇ m, 6.5 ⁇ m, 7 ⁇ m, 7.5 ⁇ m, 8 ⁇ m, 8.5 ⁇ m, 9 ⁇ m, 9.5 ⁇ m, 10 ⁇ m, 10.5 ⁇ m, 11 ⁇ m, 11.5 ⁇ m, 12 ⁇ m, 12.5 ⁇ m, 13 ⁇ m, 13.5 ⁇ m m, 14 ⁇ m, 14.5 ⁇ m, 15 ⁇ m, 15.5 ⁇ m, 16 ⁇ m, 16.5 ⁇ m, 17 ⁇ m, 17.5 ⁇ m, 18 ⁇ m, 18.5 ⁇ m, 19 ⁇ m, 19.5 ⁇ m, 20 ⁇ m, 20.5 ⁇ m, 21 ⁇ m, 21.5 ⁇ m, 22 ⁇ m, 22.5 ⁇ m, 23 ⁇ m, 23.5 ⁇ m, 24 ⁇ m, 24.5 ⁇ m
  • the particle size of the A particles satisfies 2 ⁇ m ⁇ D v 50 ⁇ 5 ⁇ m, and the particle size of the B particles satisfies 5 ⁇ m ⁇ D v 50 ⁇ 25 ⁇ m.
  • the broadening coefficient Span of the multi-particle system material is also defined as (D v 90-D v 10)/D v 50.
  • the broadening coefficient Span can represent the dispersion degree of particle size. The larger the broadening coefficient Span is, the wider the particle distribution of the material is.
  • the Span value of the A particles is greater than the Span value of the B particles.
  • the Span value of the A particles is selected from 0.1 to 3.0, and can be further selected from 0.1 to 2.0, and non-limiting examples include 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, etc.
  • the Span value of the B particles is selected from 0.1 to 3.0, further selected from 0.1 to 2.0, and further selected from 1.1 to 2.0, and non-limiting examples include 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2. etc.
  • the Span value of the A particles is selected from 0.1 to 2.0; the Span value of the B particles is selected from 0.1 to 2.0.
  • the particle size of the B particles satisfies 8 ⁇ m ⁇ D v 50 ⁇ 20 ⁇ m.
  • the particle sizes of A particles and B particles are beneficial to better improve the high-voltage tolerance of the positive electrode material, reduce the stress caused by large particles, and thus better avoid the cracking of the positive electrode material under high voltage conditions, enhance the cycle stability under high voltage conditions, avoid the increase of gas production, and extend the service life of the battery cell. Furthermore, it is also more conducive to improving the specific capacity and mass energy density of the positive electrode sheet. By reasonably matching the particle size grading and widening coefficient combination of large and small particles, the higher the compaction density of the material electrode sheet, the more conducive it is to improve the volume specific capacity of the material, so that the battery cell has a longer battery life in a smaller volume.
  • the B particles include B1 particles and B2 particles, and the D v 50 of the B1 particles is smaller than the D v 50 of the B2 particles.
  • the particle size of the B1 particles satisfies 5 ⁇ m ⁇ D v 50 ⁇ 10 ⁇ m, and the particle size of the B2 particles satisfies 10 ⁇ m ⁇ D v 50 ⁇ 25 ⁇ m.
  • the particle size of the B1 particles satisfies 5 ⁇ m ⁇ D v 50 ⁇ 10 ⁇ m
  • the D v 50 of the B1 particles can also be selected from any one of the following particle sizes or an interval consisting of any two of them: 5.1 ⁇ m, 5.2 ⁇ m, 5.3 ⁇ m, 5.4 ⁇ m, 5.5 ⁇ m, 6 ⁇ m, 6.5 ⁇ m, 7 ⁇ m, 7.5 ⁇ m, 8 ⁇ m, 8.5 ⁇ m, 9 ⁇ m, 9.5 ⁇ m, 10 ⁇ m, etc.
  • the particle size of the B2 particles satisfies 10 ⁇ m ⁇ D v 50 ⁇ 25 ⁇ m
  • the D v 50 can also be selected from any one of the following particle sizes or an interval consisting of any two of them: 10.1 ⁇ m, 10.2 ⁇ m, 10.3 ⁇ m, 10.4 ⁇ m, 10.5 ⁇ m, 11 ⁇ m, 11.5 ⁇ m, 12 ⁇ m, 12.5 ⁇ m, 13 ⁇ m, 13.5 ⁇ m, 14 ⁇ m, 14.5 ⁇ m, 15 ⁇ m, 15.5 ⁇ m, 16 ⁇ m, 16.5 ⁇ m, 17 ⁇ m, 17.5 ⁇ m, 18 ⁇ m, 18.5 ⁇ m, 19 ⁇ m, 19.5 ⁇ m, 20 ⁇ m, 20.5 ⁇ m, 21 ⁇ m, 21.5 ⁇ m, 22 ⁇ m, 22.5 ⁇ m, 23 ⁇ m, 23.5 ⁇ m, 24 ⁇ m, 24.5 ⁇ m, 25 ⁇ m, etc.
  • the weight proportion of the B1 particles in the B particles can be selected from 50% to 100%, and can also be selected from any one or two of the following percentages: 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, etc.
  • the weight proportion of the B2 particles in the B particles can be selected from 0% to 50%, and can also be selected from any one or two of the following percentages: 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc.
  • the Span value of the A particles can be selected from 0.1 to 2.0, such as, for example, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0, etc.
  • the Span value of the B1 particles can be selected from 0.1 to 2.0, such as, for example, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0, etc.
  • the Span value of the B2 particles can be selected from 0.1 to 2.0, such as, for example, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0, etc.
  • B particles are further divided into B1 particles and B2 particles, so that the D v 50 of B1 particles is smaller than the D v 50 of B2 particles.
  • the positive electrode active material can include particles of three size grades, and the particle size of larger-sized particles can be more finely controlled; further, by reasonably controlling the proportion of particles of different sizes and the widening coefficient Span, while improving the compaction density and enhancing the specific capacity and mass energy density of the positive electrode plate, the power performance can be better improved by reasonably controlling the content of intermediate-sized B1 particles, avoiding excessive dense stacking that affects the wettability of the electrolyte, avoiding the electrolyte from being unable to contact the internal active material of the plate to cause concentration difference and thereby adversely restricting lithium ion transmission.
  • the B particles include B1' particles, B2' particles, and B3' particles, and the D v 50 of the B1' particles, the B2' particles, and the B3' particles increase in sequence.
  • the particle size of the B1' particle satisfies 8 ⁇ m ⁇ D v 50 ⁇ 12 ⁇ m
  • the particle size of the B2' particle satisfies 12 ⁇ m ⁇ D v 50 ⁇ 15 ⁇ m
  • the particle size of the B3' particle satisfies 15 ⁇ m ⁇ D v 50 ⁇ 20 ⁇ m.
  • the particle size of the B1' particle satisfies 8 ⁇ m ⁇ D v 50 ⁇ 12 ⁇ m
  • the D v 50 of the B1 particle can also be selected from any one of the following particle sizes or an interval consisting of any two of them: 8.1 ⁇ m, 8.2 ⁇ m, 8.3 ⁇ m, 8.4 ⁇ m, 8.5 ⁇ m, 9 ⁇ m, 9.5 ⁇ m, 10 ⁇ m, 10.5 ⁇ m, 11 ⁇ m, 11.5 ⁇ m, 12 ⁇ m, etc.
  • the particle size of the B2' particle satisfies 12 ⁇ m ⁇ D v 50 ⁇ 15 ⁇ m
  • the D v 50 of the B2 particle can also be selected from any one or two of the following particle sizes: 12.1 ⁇ m, 12.2 ⁇ m, 12.3 ⁇ m, 12.4 ⁇ m, 12.5 ⁇ m, 13 ⁇ m, 13.5 ⁇ m, 14 ⁇ m, 14.5 ⁇ m, 15 ⁇ m, etc.
  • the particle size of the B3' particles satisfies 15 ⁇ m ⁇ D v 50 ⁇ 20 ⁇ m
  • the D v 50 of the B2 particles can also be selected from any one of the following particle sizes or an interval consisting of any two of them: 15.1 ⁇ m, 15.2 ⁇ m, 15.3 ⁇ m, 15.4 ⁇ m, 15.5 ⁇ m, 16 ⁇ m, 16.5 ⁇ m, 17 ⁇ m, 17.5 ⁇ m, 18 ⁇ m, 18.5 ⁇ m, 19 ⁇ m, 19.5 ⁇ m, 20 ⁇ m, etc.
  • the weight proportion of the B1' particles in the B particles is selected from 40% to 80%, and can also be selected from any one or two of the following percentages: 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, etc.
  • the weight proportion of the B2' particles in the B particles is selected from 20% to 30%, and can also be selected from any one of the following percentages or an interval consisting of any two percentages: 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 8%, 9%, 30%, etc.
  • the weight proportion of the B3' particles in the B particles is selected from 0% to 30%, and can also be selected from any one of the following percentages or an interval consisting of any two percentages: 2%, 4%, 5%, 6%, 8%, 10%, 12%, 15%, 16%, 18%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 8%, 9%, 30%, etc.
  • the Span value of the A particles can be selected from 0.1 to 2.0, such as, for example, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0, etc.
  • the Span value of the B1' particles can be selected from 0.1 to 2.0, such as, for example, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0, etc.
  • the Span value of the B2' particles can be selected from 0.1 to 2.0, such as, for example, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0, etc.
  • the Span value of the B3' particles can be selected from 0.1 to 2.0, and can be further selected from 0.1 to 1.4, with non-limiting examples such as 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0, etc.
  • the Span value of the A particles is selected from 0.1 to 1.5
  • the Span value of the B1' particles is selected from 0.1 to 1.5
  • the Span value of the B2' particles is selected from 0.1 to 1.4
  • B particles are further divided into B1' particles, B2' particles and B3' particles with increasing D v 50 in sequence, so that the positive electrode active material includes four size-graded particles, and the particle size of larger-sized particles is more finely controlled; further, by reasonably controlling the proportions of the four and the widening coefficient Span, while better improving the compaction density and enhancing the specific capacity and mass energy density of the positive electrode plate, the power performance can be better improved by reasonably controlling the content of intermediate-sized B1' particles and B2' particles, avoiding excessive dense stacking that affects the wettability of the electrolyte, avoiding the electrolyte from being unable to contact the internal active material of the plate to cause concentration difference and thereby adversely restricting lithium ion transmission.
  • the A particles and the B particles each independently contain the following element combination Ni x Co y M 1-xy , wherein x ⁇ 0.4, y ⁇ 0, (1-xy) ⁇ 0; the M element includes one or both of Mn and Al.
  • the aforementioned x can be independently selected from any suitable value described above.
  • y>0; further, 0 ⁇ y ⁇ 0.15 can be satisfied.
  • the presence of cobalt can increase the battery cycle and rate performance, and can also inhibit cation mixing (including lithium nickel mixing) to improve material stability.
  • (1-xy)>0 at this time, one or both of manganese and aluminum can be present; wherein, the introduction of manganese can improve the safety of the battery; the introduction of aluminum can inhibit cation mixing and improve the cycle performance.
  • the positive electrode active material does not contain cobalt, which is beneficial to reduce costs.
  • M is exemplified by at least one of manganese and aluminum, and further by manganese or aluminum.
  • the A particles and the B particles each independently include a material with a chemical formula of Li ka Q a (Ni x Co y M 1-xy ) 1-z N z O 2-c X c , wherein 0.9 ⁇ k ⁇ 1.1, 0 ⁇ a ⁇ 0.2, 0.60 ⁇ x ⁇ 1.00, 0 ⁇ y ⁇ 0.15, 0 ⁇ (1-xy), 0 ⁇ z ⁇ 0.5, 0 ⁇ c ⁇ 1,
  • the M element may include one or both of Mn and Al
  • the Q element may include one or more of Na, K, Rb and Ca
  • the N element may include one or more of Al, Ti, Zr, Nb, Sr, Sb, Y, Ba, Co, Mn, Mg, W, Si, Mo, P and C
  • the X element may include one or more of B, F, S and Cl.
  • 0.92 ⁇ k ⁇ 1.08; alternatively, 0.95 ⁇ k ⁇ 1.05; alternatively, 0.96 ⁇ k ⁇ 1.04; alternatively, 0.98 ⁇ k ⁇ 1.02; alternatively, 0.99 ⁇ k ⁇ 1.01; alternatively, k 1.
  • the material chemical formula of the A particles is Li(Ni 0.8 Co 0.1 Mn 0.1 ) 0.95 Zr 0.03 Al 0.02 O 2 , and the nickel-lithium molar ratio R Ni/Li is 0.76.
  • the molar ratio R Ni/Li of the nickel element to the lithium element in the A particles and the B particles is independently ⁇ 0.33.
  • the nickel-lithium molar ratio R Ni /Li in the A particles is independently ⁇ 0.3, and can also be independently ⁇ 0.4, and can also be independently ⁇ 0.5, and can also be independently ⁇ 0.6, and can also be independently ⁇ 0.7, and can also be independently ⁇ 0.8.
  • the nickel-lithium molar ratio R Ni/Li in the B particles is independently ⁇ 0.3, and can also be independently ⁇ 0.4, and can also be independently ⁇ 0.5, and can also be independently ⁇ 0.6, and can also be independently ⁇ 0.7, and can also be independently ⁇ 0.8.
  • the nickel-lithium molar ratio R Ni/Li in the A particles and the B particles can also be independently selected from any one of the following values or an interval consisting of any two values: 0.33, 1/3, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.02, 0.05, 0.9, 0.95, 1, etc.
  • the nickel-lithium molar ratio R Ni/Li in the A particles and the B particles can also be independently selected from any one of the following numerical intervals (any numerical endpoint here can be independently included or not included): 0.4-1, 0.5-1, 0.6-1, 0.7-1, 0.8-1, 0.8-0.96, etc.
  • the nickel-lithium molar ratio R Ni/Li in the A particles is selected from 0.7-1.0. In some embodiments, the nickel-lithium molar ratio R Ni/Li in the B particles is selected from 0.8-1.0. In some embodiments, the nickel-to-lithium molar ratio R Ni/Li in the B particles is selected from 0.8 to 0.96.
  • the unit cell parameters of traditional nickel-rich positive electrode materials (such as nickel-rich ternary positive electrode materials) will change with the occurrence of lithium intercalation and deintercalation.
  • the change of unit cell parameters will cause internal stress in the material.
  • the internal stress of the material continues to accumulate, which in turn causes the material to undergo structural phase changes and particle cracking, which will greatly damage the reversible cycle of the material.
  • the degree of lithium intercalation and deintercalation of nickel-rich materials (such as nickel-rich ternary materials) will be further deepened.
  • the positive electrode active material can adopt a traditional nickel-rich ternary positive electrode material.
  • the doping of N elements can also be introduced into the ternary positive electrode active material, which can reduce the degree of lattice change of the material and play a role in stabilizing the lattice, thereby improving the cycle performance of the nickel-rich ternary material.
  • the A particles and the B particles may use positive electrode active materials for batteries known in the art.
  • the positive electrode active materials applicable to the A particles and the B particles of the present application may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds.
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used.
  • These positive electrode active materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO 2 ), lithium nickel oxide (such as LiNiO 2 ), lithium manganese oxide (such as LiMnO 2 , LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), and the like.
  • lithium cobalt oxide such as LiCoO 2
  • lithium nickel oxide such as LiNiO
  • lithium-containing phosphates with an olivine structure may include, but are not limited to, one or more of lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate and carbon
  • the positive electrode active material is any suitable ternary positive electrode material.
  • suitable ternary positive electrode material include NCM (nickel cobalt manganese ternary material), NCA (nickel cobalt aluminum ternary material), etc.
  • NCM materials include NCM 523 , NCM 622 , NCM 811 , etc.
  • the molar ratio of nickel, cobalt, and aluminum elements in the NCA material is usually controlled according to the theoretical value of 80:15:5.
  • the true density of the A particles and the B particles may be each independently greater than 4.0 g/cc.
  • the true density of the A particles and the B particles are each independently selected from 4.0 g/cc to 4.8 g/cc.
  • the true density of the A particles is each independently selected from 4.6 g/cc to 4.8 g/cc.
  • the true density of the B particles is each independently selected from 4.5 g/cc to 4.8 g/cc.
  • the true density of the A particles is 4.6 g/cc to 4.8 g/cc
  • the true density of the B particles is selected from 4.6 g/cc to 4.8 g/cc.
  • true density used in this application has a well-known meaning in the art, and refers to the ratio of the mass of the positive electrode active material or positive electrode active particles to its true volume, where the true volume is the actual volume of the solid substance, excluding the volume corresponding to the pores existing inside the particles.
  • the unit can be g/cc, for example, the ratio of the mass in g to the corresponding true volume in cm3 can obtain the true density value.
  • true density is one of the main factors that determine the compaction density of the positive electrode material.
  • the A particles and the B particles each independently include a body structure and an oxide layer covering at least a portion of a surface of the body structure;
  • the bulk structure includes a material with a chemical formula of Li k1-a1 Q a1 (Ni x1 Co y1 M 1-x1-y1 ) 1-z1 N z1 O2, wherein 0.9 ⁇ k1 ⁇ 1.1 (optionally, 0.92 ⁇ k1 ⁇ 1.08; optionally, 0.95 ⁇ k1 ⁇ 1.05; optionally, 0.96 ⁇ k1 ⁇ 1.04; optionally, 0.98 ⁇ k1 ⁇ 1.02; optionally, 0.99 ⁇ k1 ⁇ 1.01; optionally, k1 equals 1), 0 ⁇ a1 ⁇ 0.20, 0.40 ⁇ x1 ⁇ 1.00 (optionally, 0.50 ⁇ x1 ⁇ 1.00; optionally, 0.60 ⁇ x1 ⁇ 1.00; optionally, 0.70 ⁇ x1 ⁇ 1.00), 0 ⁇ y1 ⁇ 0.15, 0 ⁇ (1-x1-y1), 0 ⁇ z1 ⁇ 0.5, and the Q element includes one or more of Na, K, Rb and Ca, the M element includes one or two of Mn and Al, and the N element includes
  • the N element includes one or more of Al, Ti, Zr, Nb, Sr, Sb, Y, Mg and W;
  • the oxide layer comprises a material having a chemical formula of Li k2-a2 Q' a2 (Ni x2 Co y2 M' 1-x2-y2 ) 1-z2 N' z2 O 2-c2 X c2 , wherein .9 ⁇ k2 ⁇ 1.1 (optionally, 0.92 ⁇ k2 ⁇ 1.08; optionally, 0.95 ⁇ k2 ⁇ 1.05; optionally, 0.96 ⁇ k2 ⁇ 1.04; optionally, 0.98 ⁇ k2 ⁇ 1.02; optionally, 0.99 ⁇ k2 ⁇ 1.01; optionally, k2 is equal to 1), 0 ⁇ a2 ⁇ 0.20, 0.40 ⁇ x2 ⁇ 1.00 (optionally, 0.50 ⁇ x2 ⁇ 1.00; optionally, 0.60 ⁇ x2 ⁇ 1.00; optionally , 0.70 ⁇ x2 ⁇ 1.00), 0 ⁇ y2 ⁇ 0.15, 0 ⁇ (1-x2-y2), 0 ⁇ z2 ⁇ 0.5, 0 ⁇ c2 ⁇ 1, and the Q' element includes one or more of Na, K, Rb and
  • both the A particles and the B particles have an oxide layer (coating layer), as shown in FIG. 1( b ).
  • the chemical formulas of the A particles and the B particles can be measured by inductively coupled plasma optical emission spectroscopy.
  • Q' elements can be doped in the bulk structure of the positive electrode active material to increase the lithium ion diffusion coefficient and reduce the lithium nickel mixing. It is also possible to coat the surface of the positive electrode active material to form an oxide layer doped with a specific N' element on the surface of the particle, which can reduce the reactivity of the surface of the material with the electrolyte, reduce the oxygen release of the material, improve the structural stability of the active material, improve the ionic conductivity, and also improve the material capacity.
  • the material can also have a higher specific capacity, and at the same time reduce the degree of side reactions and phase changes between the positive electrode material and the electrolyte, so that the battery has a lower watt-hour cost and a higher cycle life.
  • the material interface without the coating layer is likely to have a large number of side reactions with the electrolyte, resulting in the oxidation of the electrolyte to generate gases such as carbon dioxide and oxygen; moreover, when there is no coating layer, the layered structure on the surface of the positive electrode active material is more likely to transform into a rock salt structure, resulting in the loss of chemical reactivity on the surface of the material.
  • the structural stability of the material can be better improved, the intensification of surface side reactions can be better suppressed, and the material cycle life can be better extended.
  • the content of the oxide layer is too small, the above effect is not obvious.
  • the content of the oxide layer is too large, the capacity of the material may decrease.
  • Q'b2Nix2Coy2M'1 -xy is the same as Qb1Nix1Coy1M1 -x1-y1 .
  • the same process can be used to prepare them , and A particles and B particles can be obtained by screening.
  • the N’ element includes one or more of Al, Ti, Zr, Sr, Sb, Mo, Nb, Mg, Y and W.
  • the N' element includes one or more of Al, Ti, Zr, Sr, Sb, W, C, P and Mo.
  • the N' element includes at least one of Al, Zr, Nb, Sr, Sb, Co, Mg, W, and Mo.
  • elements such as Zr, Al, Mg, W, Mo, Co, Sr, Sb, Nb, etc., among which elements such as Mg, Ti, Al, and Mo can reduce the lattice deformation of the material during the charge and discharge cycle, thereby improving the structural stability of the material.
  • the X element includes at least one of B, Cl, S, and F.
  • Elements such as B, Cl, S, and F are doped into the oxide layer to improve capacity and rate performance.
  • the thickness of the oxide layer may be 0 to 100 nm, further may be 1 nm to 100 nm, and may also be 1 nm to 20 nm.
  • the thickness of the oxide layer may also be selected from any one or any two of the following intervals: 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 12 nm, 15 nm, 16 nm, 18 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, etc.
  • the mass percentage of the oxide layer relative to the main structure may be 0.01% to 5%, further 0.01% to 4%, and further 0.05% to 4%.
  • the mass percentage of the oxide layer relative to the main structure may also be selected from any one of the following percentages or an interval consisting of any two percentages: 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.08%, 0.9%, 1%, 1.2%, 1.5%, 1.6%, 1.8%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.
  • the mass proportion of the N element in the oxide layer in the positive electrode active material can be 0.01%-4%, further can be 0.05%-4%, and further can be 0.1%-4%.
  • the mass proportion of the N element in the oxide layer in the positive electrode active material can also be selected from any one of the following percentages or any two percentages: 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.08%, 0.9%, 1%, 1.2%, 1.5%, 1.6%, 1.8%, 2%, 2.5%, 3%, 3.5%, 4%, etc.
  • the thickness of the coating layer in the A particles and the B particles can be measured by a transmission electron microscopy method.
  • the mass content of the coating layer in the A particles and the B particles can be measured by inductively coupled plasma optical emission spectroscopy.
  • the mass proportion of the N element in the A particles and the B particles in the positive electrode active material described in the present application can be measured by inductively coupled plasma optical emission spectroscopy.
  • the aforementioned doping and coating purposes can be better achieved (through doping, the doping source can be evenly introduced into the bulk phase of the material, reducing shrinkage and expansion and improving structural stability; through coating, the nickel content can be reduced, the interface can be passivated, and the reactivity with the electrolyte can be reduced), the chemical reaction activity and structural stability of the material can be better adjusted, the particle size design of the material can be better combined with the structural design, and at the same time, the material can be given a higher specific capacity, the degree of side reactions and phase changes between the positive electrode material and the electrolyte can be reduced, and the battery has a lower watt-hour cost and a higher cycle life.
  • the free lithium content in the positive electrode active material is less than 3000 ppm, calculated by mass ratio.
  • the content of lithium carbonate in the positive electrode active material described in the present application is less than 3500 ppm, calculated by mass ratio.
  • the content of lithium hydroxide in the positive electrode active material described in the present application is less than 3000 ppm, by mass ratio. Further, the content of lithium carbonate is less than 3500 ppm, by mass ratio.
  • the mass proportion of free lithium in particles A and particles B in the positive electrode active material described in the present application can be measured by a free lithium potentiometric titration method.
  • the free lithium (such as lithium carbonate, lithium hydroxide, etc.) content in the positive electrode active material can be reasonably controlled to avoid excessive gas production during the cycle under high voltage conditions. If the free lithium is too high, it will react with the hydrofluoric acid produced by the decomposition of the electrolyte during the cycle under high voltage conditions to produce a large amount of gas, causing the battery cell to swell and bulge, affecting the battery cell and easily causing battery cell safety accidents.
  • the free lithium such as lithium carbonate, lithium hydroxide, etc.
  • the ratio of the I003 grain content to the I104 grain content of the positive electrode active material is I003/I104 ⁇ 1.2, measured as the ratio of the characteristic peak area of the I003 crystal plane to the I104 crystal plane in the XRD spectrum;
  • I003/I104 is selected from 1.2 to 2;
  • I003/I104 is selected from 1.3 to 2;
  • I003/I104 is selected from 1.3 to 1.6.
  • the grain size of the positive electrode active material can be tested by X-ray diffraction (XRD) method. Further, the following test parameters are adopted: the sample is prepared by flat plate sample preparation method, and the test angle is 15° to 70°.
  • the degree of lithium-nickel mixing can be better controlled to avoid excessive nickel elements occupying the lithium element lattice position, which leads to a decrease in reversible capacity and a decrease in the diffusion coefficient of lithium ions. If lithium ions and divalent nickel undergo cation mixing, the divalent nickel enters the lithium ions, which will reduce the lithium ion diffusion coefficient, increase impedance, lead to a decrease in capacity, and damage the cycle performance and storage performance. Generally speaking, the lower the degree of mixing, the more regular the arrangement, and the better the battery performance.
  • the B particles in the B particles, at least a portion of the primary particles are oriented in the radial direction.
  • the primary particles can be oriented in a certain radial direction (as shown in the cross-sectional morphology of the B particle SEM test in Figure 6), thereby inhibiting the shrinkage and expansion that may occur under high voltage, avoiding the increase of internal stress, and better preventing the material from breaking under high voltage.
  • the cycle performance can be improved. The higher the degree of oriented arrangement in the radial direction, the lower the degree of random arrangement without orientation, and the more obvious the degree of improvement in effect.
  • the positive electrode active material provided in the first aspect of the present application is a high-nickel positive electrode material having small particles and large particles of a specific structure, and the content of small particles is higher than that of large particles.
  • the prepared positive electrode plate has a high mass specific capacity and excellent structural stability. Furthermore, at the battery cell level, the mass energy density and cycle life of the battery cell can be significantly improved, and the side reactions with the electrolyte can be reduced, thereby reducing the gas production of the battery cell.
  • the present application provides a positive electrode plate, which includes a positive electrode collector and a positive electrode active material layer located on at least one surface of the positive electrode collector, wherein the positive electrode active material layer includes the positive electrode active material described in the first aspect of the present application.
  • the positive electrode active material of the first aspect of the present application can be used to prepare positive electrode plates with a high nickel content.
  • the particle size and content of the positive electrode active material can be designed to avoid cracking of the material under high voltage, thereby improving the battery cell cycle and storage performance under high voltage conditions.
  • the chemical reaction activity and structural stability of the material can be further adjusted by doping and/or coating structure design, so that the material has a higher specific capacity, while reducing the degree of side reactions and phase changes between the positive electrode material and the electrolyte, so that the battery has a lower watt-hour cost and a higher cycle life.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector. See Figures 7 and 8.
  • the positive electrode active material in Figure 7 includes A particles and B particles.
  • the positive electrode active material in Figure 8 includes A particles, B1 particles and B2 particles.
  • the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil may be used.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode film layer may also optionally include a binder.
  • the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene terpolymer vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer
  • the positive electrode film layer may further optionally include a conductive agent.
  • the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N-methylpyrrolidone
  • the compaction density of the positive electrode sheet is 3.3 g/cm 3 to 3.7 g/cm 3 , and some non-limiting examples include 3.3 g/cm 3 , 3.4 g/cm 3 , 3.5 g/cm 3 , 3.6 g/cm 3 , 3.7 g/cm 3 and the like.
  • the “compacted density” used in this application has a well-known meaning in the art, and refers to the ratio of the mass of the positive electrode active material to its volume.
  • the material cracking under high voltage conditions can be better avoided while giving the electrode sheet a better specific capacity and energy density.
  • the compaction density of the positive electrode sheet is also limited by the true density of the A particles and B particles contained therein.
  • the improvement of the compaction density of the electrode sheet can increase the volume specific capacity of the material, so that the battery cell has a longer battery life in a smaller volume.
  • the present application provides an electrochemical energy storage device, which includes the positive electrode plate, the negative electrode plate and the isolation membrane described in the second aspect of the present application, wherein the isolation membrane is arranged between the positive electrode plate and the negative electrode plate.
  • the present application provides a secondary battery comprising at least one of the positive electrode plate described in the second aspect of the present application and the electrochemical energy storage device described in the third aspect of the present application.
  • the present application provides an electrical device, which includes at least one of the positive electrode plate described in the second aspect of the present application, the electrochemical energy storage device described in the third aspect of the present application, and the secondary battery described in the fourth aspect of the present application.
  • the positive electrode active material of the first aspect of the present application is used to prepare a positive electrode plate with a high nickel content, and then to prepare an electrochemical energy storage device, a secondary battery, and an electrical device.
  • the particle size and content of the positive electrode active material can be designed to avoid cracking of the material under high voltage, improve the battery cell cycle and storage performance under high voltage conditions, and further use the doping and/or coating structure design to adjust the chemical reaction activity and structural stability of the material, so that the material has a higher specific capacity, while reducing the degree of side reactions and phase changes between the positive electrode material and the electrolyte, so that the battery has a lower watt-hour cost and a higher cycle life.
  • the secondary battery includes a positive electrode sheet (provided in the second aspect of the present application), a negative electrode sheet, an electrolyte and a separator.
  • a positive electrode sheet provided in the second aspect of the present application
  • a negative electrode sheet a negative electrode sheet
  • an electrolyte a separator.
  • the electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet.
  • the separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing lithium ions to pass through.
  • the positive electrode sheet in the third and fourth aspects of the present application may adopt the positive electrode sheet provided in the second aspect of the present application.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the metal foil copper foil may be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate.
  • the composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative electrode active material may be a negative electrode active material for a battery known in the art.
  • the negative electrode active material may include the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc.
  • the silicon-based material may be selected from elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may be selected from elemental tin, tin oxide compounds, and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the negative electrode film layer may further include a binder.
  • the binder may be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer may further include a conductive agent, which may be selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • a conductive agent which may be selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).
  • a thickener eg, sodium carboxymethyl cellulose (CMC-Na)
  • the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the present application has no particular restrictions on the type of electrolyte, which can be selected according to needs.
  • the electrolyte can be liquid, gel or all-solid.
  • the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorobisoxalatophosphate, and lithium tetrafluorooxalatophosphate.
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • LiClO 4 lithium perchlorate
  • LiClO 4 lithium hexafluoroarsenate
  • LiFSI lithium bisfluoros
  • the solvent can be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • EC ethylene carbonate
  • PC propylene carbonate
  • EMC diethyl carbonate
  • DMC dimethyl carbonate
  • DPC diprop
  • the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • additives such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • the secondary battery further includes a separator.
  • the present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane can be selected from glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation.
  • the materials of each layer can be the same or different, without particular limitation.
  • Electrode assembly electrochemical energy storage device, secondary battery, power device
  • the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.
  • the electrochemical energy storage device may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.
  • the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package.
  • the material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • FIG9 is a secondary battery 5 of a square structure as an example.
  • the outer package may include a shell 51 and a cover plate 53.
  • the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is encapsulated in the receiving cavity.
  • the electrolyte is infiltrated in the electrode assembly 52.
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to actual needs.
  • the present application also provides an electrical device, which includes a secondary battery provided in the present application.
  • the secondary battery can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device.
  • the electrical device may include mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.
  • the mobile device may be, for example, a mobile phone, a laptop computer, etc.;
  • the electric vehicle may be, for example, a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., but are not limited thereto.
  • a secondary battery can be selected according to its usage requirements.
  • Fig. 11 is an example of an electric device 6.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack or a battery module may be used.
  • a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a secondary battery may be used as a power source.
  • a method for preparing a positive electrode active material comprises the following steps: mixing the A particles and the B particles according to a preset mass ratio to prepare the positive electrode active material; the A particles and the B particles are as defined in the first aspect of the present application;
  • the A particles can be prepared by a method comprising the following steps: mixing lithium hydroxide, a nickel-cobalt M-body precursor material Ni x Co y M 1-xy (OH) 2 , and an optional Q additive and an optional N additive, and performing a primary sintering in the presence of oxygen and at a temperature T1; optionally, adding at least one of an X additive and an N additive to the primary sintering product, mixing, and performing a secondary sintering in the presence of oxygen;
  • the B particles can be prepared by a method comprising the following steps: mixing lithium hydroxide, a nickel-cobalt M-body precursor material Ni x Co y M 1-xy (OH) 2 , and an optional Q additive and an optional N additive, and performing a primary sintering in the presence of oxygen and at a temperature T2; optionally, adding at least one of an X additive and an N additive to the primary sintering product, mixing, and performing a secondary sintering in the presence of oxygen;
  • the Q additive, N additive, and X additive are additives containing Q element, N element, and X element, respectively;
  • the temperature T1 is higher than the temperature T2;
  • x, y, M element, Q element and N element are as defined in the first aspect of the present application;.
  • the primary sintering temperature (T1) in the step of preparing the A particles, in the step of sintering in the presence of oxygen, is 700°C to 950°C, optionally 750°C to 900°C, and the secondary sintering temperature is 300°C to 600°C, optionally 350°C to 550°C.
  • the primary sintering temperature T1 of the A particles can also be any one of the following temperatures or any two of the intervals: 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, etc.
  • the secondary sintering temperature can also be any one of the following temperatures or any two of the intervals: 350°C, 400°C, 450°C, 500°C, 550°C, etc.
  • the primary sintering temperature in the step of preparing the B particles, in the step of sintering in the presence of oxygen, is 700°C to 900°C, optionally 750°C to 850°C, and the secondary sintering temperature is 300°C to 600°C, optionally 350°C to 550°C.
  • the primary sintering temperature may also be any one of the following temperatures or any two of the following intervals: 700°C, 750°C, 800°C, 850°C, 900°C, etc.
  • the secondary sintering temperature may also be any one of the following temperatures or any two of the following intervals: 350°C, 400°C, 450°C, 500°C, 550°C, etc.
  • the positive electrode active particles (A particles or B particles) provided in the first aspect of the present application have no surface coating layer, they can be prepared by a single sintering method using corresponding precursors in an oxidizing atmosphere.
  • the precursor of the main structure is sintered in an oxidizing atmosphere and at a relatively high temperature (such as A particles at 700°C to 950°C, and B particles at 700°C to 900°C) to form a main structure, and then mixed with the coating layer precursor and sintered in an oxidizing atmosphere and at a relatively low temperature (such as 300°C to 600°C) to form an oxide layer, thereby preparing A particles or B particles with a coating layer.
  • a relatively high temperature such as A particles at 700°C to 950°C, and B particles at 700°C to 900°C
  • a relatively low temperature such as 300°C to 600°C
  • the particles inside the particles are easily connected. Therefore, at a relatively high first sintering temperature (T1), the particles can be fully connected to prepare large-sized single crystals or quasi-single crystal particles (A particles), and small-sized secondary particles (B particles) can be prepared at a relatively low first sintering temperature (T2). At this time, the fine particles in the secondary particles are not connected or only partially connected.
  • the present application provides a method for preparing a positive electrode slurry, comprising the following steps: mixing A particles, B particles and an optional auxiliary agent to prepare the positive electrode slurry; wherein the A particles and the B particles are as defined in the first aspect of the present application;
  • the preparation method satisfies one or more of the following characteristics:
  • the pH of the positive electrode slurry is 11 to 12;
  • the step of mixing the A particles, the B particles and the optional auxiliary agent is carried out under stirring conditions, with a stirring speed of 500 to 2000 r/min and a stirring time of 0.5 h to 5 h.
  • the viscosity of the positive electrode slurry can be better controlled and the processing performance can be improved.
  • room temperature refers to 20°C to 30°C, and further, may be 25°C.
  • a single-sided coating method is used when the positive electrode slurry is coated on the positive electrode current collector, and a double-sided coating method is used when the negative electrode slurry is coated on the negative electrode current collector.
  • the positive electrode plates of each example use substantially the same single-sided coating amount
  • the negative electrode plates of each example use substantially the same single-sided coating amount.
  • the coating amount of the slurry can be regulated by the coating mass per unit area. It should be understood that the single-sided and double-sided coating methods in each example are used for exemplary explanation.
  • the preparation of the positive pole pieces and the negative pole pieces can each independently adopt a single-sided coating or a double-sided coating method.
  • substantially the same in relation to the preparation method means that except for the specially specified parameters, the other parameters remain unchanged, but it is understood that adaptive adjustments based on the specified changed parameters are acceptable. For example, when the composition and content of the target product are changed, the composition and amount of the raw materials are allowed to be adaptively adjusted.
  • the particle size of the precursor determines the particle size of the positive electrode material, and the size and distribution of particles A and B can be controlled by regulating the size and distribution of the precursor.
  • the means of regulating the size and distribution of the precursor are known.
  • the A particles prepared in sequence are mixed with the B particles in a certain mass ratio (see Table 1 and Table 2) to prepare a positive electrode active material for standby use.
  • the positive electrode active material, polyvinylidene fluoride and conductive carbon black are mixed in a mass ratio of 90:5:5, and then N-methylpyrrolidone (NMP) is added and stirred for 2 hours. Then, it is stirred in a homogenizer at 1000r/min until it is evenly mixed, and then evenly coated on the single side surface of a 13-micron thick aluminum foil current collector. After coating, it is dried in a drying oven at 100°C, cold pressed, and cut to obtain positive electrode sheets.
  • NMP N-methylpyrrolidone
  • a mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) was mixed in a volume ratio of 1:2 to obtain a mixed solvent. Then, in an argon atmosphere glove box, fully dried lithium hexafluorophosphate was dissolved in the mixed solvent and mixed evenly to obtain an electrolyte.
  • the lithium salt concentration in the electrolyte was 1 mol/L.
  • the negative electrode active material graphite, sodium carboxymethyl cellulose, styrene butadiene rubber and acetylene black are mixed in a mass ratio of 96:1:1:2, deionized water is added, and the mixture is stirred evenly in a blender. The slurry is then coated on both sides of an 8-micron thick copper foil, dried in an oven at 100°C, cold pressed, and cut to obtain negative electrode sheets.
  • the positive electrode sheet, isolation film, and negative electrode sheet are stacked from top to bottom, ensuring that the positive and negative electrode sheets cannot touch each other. Then they are wound into bare cells through a winding needle, placed in a square aluminum shell, and injected with electrolyte. The cells are prepared by steps of standing, forming, and capacity.
  • Example 2 adopts a method substantially the same as that of Example 1, except that the preparation steps of the positive electrode active material are different and the additives of the positive electrode active material are different.
  • the ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH 2 (particle size D v 50 about 4 ⁇ m), LiOH ⁇ H 2 O, ZrO 2 , Al 2 O 3 and B 2 O 3 were mixed in a mixer at a molar ratio of 0.95:1.04:0.03:0.01:0.01, and then sintered at 860°C in an oxygen atmosphere to obtain A particles.
  • the prepared A particles and B particles are mixed in a certain mass ratio (see Table 1 and Table 2) to prepare a positive electrode active material for standby use.
  • Example 3 adopts a method substantially the same as that of Example 1, except that the preparation steps of the positive electrode active material are different and the additives of the positive electrode active material are different.
  • the prepared A particles and B particles are mixed in a certain mass ratio (see Table 1 and Table 2) to prepare a positive electrode active material for standby use.
  • Embodiment 1a to embodiment 1d Using ternary positive electrode materials
  • Example 1a, Example 1b, Example 1c and Example 1d all adopt a method basically the same as Example 1, the difference is that the composition of the positive electrode active material is different, and the A particles and the B particles are both made of homemade NCM ternary positive electrode material.
  • Example 1a, Example 1b, Example 1c and Example 1d use different nickel contents (refer to Table 1), use ternary precursors with different nickel contents, and the other preparation parameters are the same.
  • the ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH 2 (particle size D v 50 of about 4 ⁇ m) and LiOH ⁇ H 2 O were mixed in a mixer at a molar ratio of 1:1.04, and then sintered at 860° C. in an oxygen atmosphere to obtain A particles.
  • the ternary precursor (Ni 0.8 Co 0.1 Mn 0.1 )OH 2 (particle size D v 50 of about 10 ⁇ m) and LiOH ⁇ H 2 O were mixed in a mixer at a molar ratio of 1:1.04, and then sintered at 820° C. in an oxygen atmosphere to obtain B particles.
  • Example 4 The prepared A particles and B particles were mixed in a certain mass ratio (refer to Table 1 and Table 2) to prepare a positive electrode active material (Example 4-1) for standby use.
  • the D v 10, D v 50, D v 90 and Span values of the A particles and B particles in Example 1b, Example 1c and Example 1d were similar to those in Example 1a.
  • Comparative Example 1 A method substantially the same as that of Example 1 is adopted, except that particles A of equal mass are used instead of particles B to prepare the positive electrode sheet.
  • Comparative Example 2 A method substantially the same as that of Example 1 is adopted, except that B particles of equal mass are used instead of A particles to prepare the positive electrode sheet.
  • Comparative Example 3 A method substantially the same as that of Example 1 is adopted, except that the mass content of the A particles is less than that of the B particles, and further, the mass content of the A particles in the positive electrode active material is 20%.
  • Comparative Example 4a A method substantially the same as that of Example 1a was adopted, except that an equal mass of A particles (NCM811) was used instead of B particles to prepare the positive electrode sheet.
  • Comparative Example 4b A method substantially the same as that of Example 1a was adopted, except that an equal mass of B particles (NCM811) was used instead of A particles to prepare the positive electrode sheet.
  • Example 4-6 The method is substantially the same as that of Example 1, except that the positive electrode active particles include B1 particles and B2 particles, and the D v 50, Span and content of the A, B1 and B2 particles are adjusted.
  • Comparative Example 5 A method substantially the same as that of Example 4 was adopted, except that the content of B1 particles was adjusted.
  • Comparative Example 6 The method is substantially the same as that of Example 6, except that the D v 50 of particles B1 and B2 is adjusted.
  • Comparative Example 7-8 The method is substantially the same as that of Example 6, except that the combination of D v 50 and Span of particles B1 and B2 is adjusted.
  • a particles, B1' particles, B2' particles and B3' particles are mixed uniformly in a mass ratio of 5:2:2:1 to prepare positive electrode active materials, and then the active materials are mixed with polyvinylidene fluoride: conductive carbon black in a mass ratio of 90:5:5, coated, cold pressed, and die-cut to prepare positive electrode sheets.
  • the chemical composition of A particles, B1' particles, B2' particles and B3' particles is Li(Ni 0.8 Co 0.1 Mn 0.1 ) 0.95 Zr 0.03 Al 0.02 O 2 .
  • the positive electrode sheet, isolation film, and negative electrode sheet are stacked from top to bottom, ensuring that the positive and negative electrode sheets cannot touch each other. Then they are wound into bare cells through a winding needle, placed in a square aluminum shell, and the electrolyte is injected. The cells are prepared by standing, forming, and charging.
  • Example 7a to Example 7m based on the aforementioned preparation method, the mass ratio of A particles, B1' particles, B2' particles and B3' particles is adjusted from 5:2:2:1 to different dosage ratios shown in Table 5, and the remaining preparation steps are the same as when the mass ratio is 5:2:2:1.
  • a particles, B1' particles, B2' particles and B3' particles are mixed uniformly in a mass ratio of 6:4:0.5:0.5 to prepare positive electrode active materials, and then the active materials are mixed with polyvinylidene fluoride: conductive carbon black in a mass ratio of 90:5:5, coated, cold pressed, and die-cut to prepare positive electrode sheets.
  • the chemical composition of A particles, B1' particles, B2' particles and B3' particles is Li(Ni 0.8 Co 0.1 Mn 0.1 ) 0.95 Zr 0.03 Al 0.02 O 2 .
  • the positive electrode sheet, isolation film, and negative electrode sheet are stacked from top to bottom, ensuring that the positive and negative electrode sheets cannot touch each other. Then they are wound into bare cells through a winding needle, placed in a square aluminum shell, and the electrolyte is injected. The cells are prepared by standing, forming, and charging.
  • Example 8 the inventors used the A particles, B1’ particles, B2’ particles and B3’ particles of Example 8, and adopted a method basically the same as Example 8, only adjusting the content of each particle (such as Example 8a to Example 8m shown in Table 9), to obtain different positive electrode sheets, and then prepared secondary batteries.
  • a particles, B1' particles, B2' particles and B3' particles are mixed in a mass ratio of 7:1:1:1 to prepare positive electrode active materials, and then the active materials are mixed with polyvinylidene fluoride: conductive carbon black in a mass ratio of 90:5:5, coated, cold pressed, and die-cut to prepare positive electrode sheets.
  • the chemical compositions of A particles, B1' particles, B2' particles and B3' particles are all Li(Ni 0.8 Co 0.1 Mn 0.1 ) 0.95 Zr 0.03 Al 0.02 O 2.
  • the positive electrode sheet, isolation film, and negative electrode sheet are stacked from top to bottom, ensuring that the positive and negative electrode sheets cannot touch each other. Then they are wound into bare cells through a winding needle, placed in a square aluminum shell, and the electrolyte is injected. The cells are prepared by standing, forming, and charging.
  • the chemical composition of the bulk structure of the positive electrode active particles of Examples 10-13 and Examples 11b, 12b, and 13b is Li(Ni 0.8 Co 0.1 Mn 0.1 ) 0.95 Zr 0.03 Al 0.02 O 2 .
  • Examples 10-12 The method is basically the same as that of Example 1, except that the active particles are provided with a coating layer, and the thickness, mass ratio, and N element content are changed. Please refer to Tables 6 and 7.
  • a particles and B particles are as follows:
  • a particles are prepared by a method comprising the following steps: mixing lithium hydroxide, nickel-cobalt M-body precursor material Ni x Co y M 1-xy (OH) 2 (D v 50 is about 4 ⁇ m), ZrO 2 and Al 2 O 3 , and sintering them once in the presence of oxygen at a temperature of 850°C; adding an additive of N" element (see Table 6) to the primary sintered product, and sintering them twice in the presence of oxygen at a temperature of 350°C;
  • the B particles are prepared by a method comprising the following steps: mixing lithium hydroxide, nickel-cobalt M-body precursor material Ni x Co y M 1-xy (OH) 2 (D v 50 is about 4 ⁇ m), ZrO 2 and Al 2 O 3 , and performing a primary sintering in the presence of oxygen at a sintering temperature of 820°C; optionally, adding an additive of N" element (refer to Table 6) to the primary sintered product, and performing a secondary sintering in the presence of oxygen at a sintering temperature of 350°C.
  • M is manganese
  • x is 0.8
  • y is 0.1
  • (1-x-y) is 0.1.
  • the N elements in the bulk structures of particles A and B both include Zr and Al, and the N' elements in the coating layers of particles A and B include Zr, Al and N" elements (see Table 6).
  • the N" elements in particles A and B are the same. When the N" element is the same as the N element, it leads to a change in content.
  • the N" element refers to other doping elements contained in the main structure.
  • the additives of the N" element when the N" element is Al, Mg, or B, the corresponding additives used in the secondary sintering are Al 2 O 3 , MgO, and B 2 O 3 , respectively.
  • Comparative Example 9 A method substantially the same as that of Example 11 is adopted, except that the thickness of the coating layer is different.
  • Example 12b A method substantially the same as that of Example 12 is adopted, except that the sintering temperature is different.
  • Example 13 A method substantially the same as that of Example 10 is adopted, except that the sintering temperature is different.
  • the “doping elements” in Table 6 include all doping elements in the bulk structure and the oxide layer, including N elements in the bulk structure and N’ elements in the oxide layer.
  • Examples 14-16 adopt a method substantially the same as that of Example 5, except that the material composition of the positive electrode active material is different.
  • Example 14-16 the combination of A particles + B1 particles + B2 particles, particle size parameters (D v 10, D v 50, D v 90 and Span control are similar to those in Example 5), and the types of doping elements of A particles + B1 particles + B2 particles are all the same.
  • Example 14 The bulk structure of Example 14 is LiNi 0.8 Co 0.1 Mn 0.1 O 2 , and its bulk phase is doped with Zr and Sr elements, and the coating layer contains Al and Mg elements.
  • Example 15 The bulk structure of Example 15 is LiNi 0.8 Co 0.1 Mn 0.1 O 2 , and its bulk phase is doped with Zr, Sr and Ti elements, and the coating layer contains Mg element.
  • Example 16 The bulk structure of Example 16 is LiNi 0.8 Co 0.1 Mn 0.1 O 2 , and its bulk phase is doped with Zr, Sr and W elements, and the cladding layer contains B element.
  • Example 2 The same active material components as in Example 1 are used, and the preparation method is basically the same, except that the primary particles of the precursor are arranged irregularly, so that the primary particles of the B particles are basically distributed irregularly.
  • Equipment model Malvern 2000 (MasterSizer 2000) laser particle size analyzer, reference standard process: GB/T19077-2016/ISO 13320:2009, detailed test process: Take an appropriate amount of the sample to be tested (the sample concentration is guaranteed to be 8% to 12% shading), add 20mL of anhydrous ethanol, and ultrasonically treat for 5min (53KHz/120W) to ensure that the sample is completely dispersed, and then measure the sample according to GB/T19077-2016/ISO 13320:2009 standard. In order to avoid the agglomeration of the drying process affecting the particle size test, take the washed wet sample for dispersion test.
  • the nitrogen adsorption specific surface area analysis test method is adopted and the result is calculated by BET (Brunauer Emmett Teller) method.
  • the nitrogen adsorption specific surface area analysis test can be carried out by Tri Star II specific surface and pore analyzer of Micromeritics Company of the United States. The test steps can refer to GB/T 19587-2004.
  • Sample to be tested positive electrode active material prepared in each example.
  • the detailed steps are as follows: dry the sample to be tested in a vacuum drying oven at 200°C for 2 hours; then use argon as the adsorption gas, and use a specific surface and pore analyzer to map the adsorption-desorption curve with a relative pressure P/ P0 of 0 to 0.99, where P is the equilibrium adsorption pressure and P0 is the saturated vapor pressure, and the specific surface area of the positive electrode active material is calculated by the BET method.
  • test was carried out using a true density tester, and the test steps were in accordance with GB/T 24586-2009.
  • the material was analyzed by TEM, and the thickness of the material coating layer was measured at multiple points to obtain the average value.
  • the positive electrode active material was analyzed by X-ray diffractometer according to JIS K 0131-1996.
  • the positive electrode active materials were analyzed using a free lithium potentiometric titrator in accordance with GB/T 9725-2007.
  • the positive electrode slurry is coated on the single-side surface of 13 ⁇ m aluminum foil with a single-side coating thickness of 110 ⁇ m. After drying, the compaction density and elongation data are collected by a cold press. The compaction density corresponding to the elongation of 0.8% is used as the test value of the compaction density of the positive electrode active material.
  • Gram capacity refers to the ratio of the electrical capacity that can be released by the active material inside the battery to the mass of the active material.
  • one cycle is defined as a constant current charge and discharge followed by a constant voltage charge and discharge at a current rate of 1C.
  • the first time is designated as C 0
  • the nth time is designated as Cn
  • the capacity retention rate of each cycle is Cn/C 0 .
  • the lithium-ion battery is first charged to 4.3V at a constant current of 1/3C, and then charged at a constant voltage with a current of 0.025C to 4.3V.
  • the volume of the lithium-ion battery is measured in deionized water by the drainage method as V0, and then stored at 70°C.
  • the volume change of the battery cell is obtained every six days, and the nth time is Vn.
  • the volume expansion rate (%) of the lithium-ion battery after storage at 70°C (Vn-V 0 )/V 0 ⁇ 100%.
  • the cell was charged at a constant current of 1C to 4.3V, then charged at a constant voltage with a current of 0.05C to 4.3V, then discharged at a constant current of 1C to 2.8V, and discharged at a constant voltage with a current of 0.05C.
  • the measured capacity was recorded as C0.
  • the battery cell is charged to 4.3V at 1C current, constant voltage charging, and current is 0.05C.
  • the fully charged battery cell is placed in a 60°C constant temperature oven for storage. Every 30 days, the battery cell is taken out and discharged to 2.8V at 25°C at 1C constant current, and then discharged at a constant voltage current of 0.05C.
  • Cycle number 25°C cycle number until the capacity retention rate reaches 80%
  • the lithium-ion battery is charged at 1C constant current to a voltage of 4.3V, then charged at 4.3V constant voltage, current of 0.05C, and then discharged at 1C constant current until the final voltage is 2.8V and the capacity is C1.
  • the capacity measured for the nth time is Cn
  • the capacity retention rate (%) (nth discharge capacity/first cycle discharge capacity) ⁇ 100%, and the cycle is continued until the cell capacity retention rate decays to 80%.
  • Example 1 the primary particles in the B particles are radially oriented and distributed, and the number of cycles at 25°C to a capacity retention rate of 80% is 2,600 cycles, and the calendar life is 40 days at 70°C and the gas production is 6 ml/ah.
  • the inventors speculate that this is because during the charge and discharge cycle, when the primary particles are radially oriented and distributed, stress concentration is not easily generated inside the material.
  • Example 17 the primary particles of the B particles were distributed roughly randomly, the number of cycles required to maintain the capacity of 80% at 25°C was 1,200, the calendar life was 40 days, and the gas production at 70°C was 36 ml/ah.
  • Comparative Example 1 includes only A particles but not B particles, and Comparative Example 2 includes only B particles but not A particles.
  • the results show that compared with Example 1, the cycle performance and storage performance of Comparative Example 1 and Comparative Example 2 are significantly reduced, and the gas production at 70°C for 40 days is significantly increased.
  • the effect comparison results of Comparative Example 4a and Comparative Example 4b are similar to those of Example 1a.
  • Comparative Example 3 the content of B particles is greater than that of A particles. Compared with Example 1, the cycle performance and storage performance of Comparative Example 3 are significantly reduced, and the gas production after 40 days of storage at 70°C is significantly increased.
  • Comparative Example 5 the content of B1 particles is relatively high. Compared with Example 4, the cycle performance and storage performance of Comparative Example 5 are significantly reduced, and the gas production during 40 days of storage at 70°C is significantly increased.
  • Comparative Example 6 the content of B1 particles is relatively high. Compared with Example 6, the cycle performance and storage performance of Comparative Example 6 are significantly reduced, and the gas production during 40 days of storage at 70°C is significantly increased.
  • Comparative Example 7 the content of B2 particles is relatively high, and the D v 50 of B1 particles is relatively high compared with Example 6, resulting in decreased cycle performance and storage performance and increased high-temperature gas production.
  • Comparative Example 8 the content of B1 and B2 particles is greater than that of A particles. Compared with Example 6, Comparative Example 8 leads to decreased cycle performance and storage performance, and increased high-temperature gas production.
  • Comparative Example 9 the coating layer thickness is relatively thick. Compared with Example 11, the cycle performance and storage performance of Comparative Example 9 are reduced, and the high-temperature gas production is increased.
  • Example 12b The cycle performance and storage performance of Example 12b were reduced compared with those of Example 12, and the high-temperature gas production was increased.
  • the cycle performance and storage performance of Example 13 were reduced compared with those of Example 10, and the high-temperature gas production was increased.
  • Examples 8a to 8m adjust the relative contents of A particles, B1’ particles, B2’ particles and B3’ particles, and all can achieve better cycle performance and lower storage gas production.
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are only examples.
  • the embodiments that have the same structure as the technical idea and play the same effect are all included in the technical scope of the present application.
  • the above-mentioned embodiments only express several embodiments of the present application, and the description is relatively detailed, but it cannot be understood as a limitation on the scope of the patent.
  • various deformations that can be thought of by those skilled in the art are applied to the embodiments, and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

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Abstract

本申请公开了一种正极活性材料，其包括A颗粒和B颗粒，其中，A颗粒具有单晶或类单晶的结构，B颗粒为包括多个一次颗粒的二次颗粒，其中，A颗粒的D v50小于B颗粒的D v50，A颗粒的质量占比大于等于B颗粒的质量占比，D v50表示材料的累计体积分布百分数达到50％时对应的粒径。

Description

正极活性材料、正极极片、电化学储能装置、二次电池、用电装置和制备方法 技术领域
本申请涉及能源技术领域以及二次电池技术领域，进一步涉及正极活性材料、正极极片、电化学储能装置、二次电池、用电装置和制备方法。
背景技术
这里的陈述仅提供与本申请有关的背景信息，而不必然构成现有技术。
随着碳中和与碳达峰战略目标的实施，新能源行业近年来迅猛发展。然而目前新能源车存在续航低和寿命差的问题，极大限制了新能源产业的发展，成为实现碳中和与碳达峰道路上的绊脚石。因此，开发高能量密度和长使用寿命的储能装置迫在眉睫。
高镍材料(如高镍三元材料等)具有高容量和循环衰减低的特点，受到行业的广泛关注。然而目前高镍材料瓦时成本高，制约了其推广应用。
发明内容
鉴于上述问题，本申请提供了一种正极活性材料、正极极片、电化学储能装置、二次电池、用电装置和制备方法，该正极活性材料为高镍正极材料，具有特定结构的小颗粒和大颗粒，且小颗粒的含量高于大颗粒，制备得到的正极极片具有较高的质量比容量和优异的结构稳定性，进一步地，在电芯层级中，可以明显提升电芯的质量能量密度和循环寿命，还能减少与电解液之间的副反应，降低电芯的产气。
第一方面，本申请提供了一种正极活性材料，其包括A颗粒和B颗粒，所述A颗粒和所述B颗粒中的镍元素相对于锂元素的摩尔比R Ni/Li各自独立地≥0.33；其中，所述A颗粒具有单晶或类单晶的结构，所述B颗粒为包括多个一次颗粒的二次颗粒，其中，所述A颗粒的D v50小于所述B颗粒的D v50，所述A颗粒的质量占比大于等于所述B颗粒的质量占比；
其中，D vN表示材料的累计体积分布百分数达到N％时对应的粒径，N为选自0～100的数值。
对于正极材料，传统的高镍材料(如高镍三元材料等)在循环过程中容易发生材料开裂，而且在高电压下开裂程度容易加深，导致循环寿命下降，而且存储过程中由于正极氧化活性增强，容易与电解液接触而发生剧烈化学反应造成电芯寿命下降，单位容量产气上升。在本申请中，该正极活性材料包括不同颗粒尺寸的高镍正极材料，其中，通过D v50区分小颗粒与大颗粒，以具有单晶或类单晶结构的A颗粒作为小颗粒，以一次颗粒团聚而成的B颗粒作为大颗粒，还控制A颗粒的质量含量高于B颗粒；特殊晶相结构的A颗粒具有均相体系或近均相体相，在材料脱嵌锂过程中，材料内部不容易产生应力，因而不易造成材料的应力作用下开裂，也因此更有利于改善高电压条件下的电芯循环和存储性能；B颗粒采用一次颗粒团聚而成，有利于提升功率性能和压实密度，通过控制A颗粒与B颗粒之间含量，控制B颗粒的含量小于A颗粒，能够降低大颗粒晶格发生收缩和膨胀而导致的应力，从而避免正极材料在高电压条件下开裂，避免因材料的破裂产生新界面，进而避免新界面与电解液发生副反应而导致的恶化电芯性能及产气加剧，从而增强高电压条件下的循环稳定性，延长电芯使用寿 命；进一步地，小尺寸的A颗粒含量的增加还有利于提升电芯的存储容量保持率，提高材料的存储日历寿命。此外，小尺寸的A颗粒采用纯单晶体系，相比混合体系，材料的极片压密和电芯功率性能会明显降低，而极片的压实密度的提升，可以提高材料的体积比容量，使得电芯在更小的体积具有更长的续航。
在本申请的一些实施方式中，所述A颗粒的粒径满足2μm≤D v50≤5μm，所述B颗粒的粒径满足5μm<D v50≤25μm；
可选地，所述A颗粒的Span值大于所述B颗粒的Span值；其中，Span＝(D v90-D v10)/D v50；
可选地，所述A颗粒的Span值选自0.1～3.0；所述B颗粒的Span值选自0.1～3.0；
可选地，所述B颗粒的粒径满足8μm<D v50≤20μm。
通过控制A颗粒和B颗粒各自的粒径在较合适的范围，有利于更好地提高正极材料的高压耐受性，降低大颗粒导致的应力，进而更好地避免正极材料在高电压条件下开裂，增强高电压条件下的循环稳定性，避免产气加剧，延长电芯使用寿命，进一步地，还更加有利于提升正极极片的比容量和质量能量密度。此外，进一步定义多颗粒体系的宽化系数Span(Span＝(D v90-D v10)/D v50)，可表示颗粒粒径的分散程度，宽化系数Span越大，从分布上表现材料的颗粒分布越宽，通过合理搭配大小颗粒的粒径级配及宽化系数组合，可使得材料极片的压实密度越高，越有利于提高材料的体积比容量，使得电芯在更小的体积具有更长的续航。
在本申请的一些实施方式中，所述B颗粒包括B1颗粒和B2颗粒，其中，所述B1颗粒的粒径满足5μm<D v50≤10μm，所述B2颗粒的粒径满足10μm<D v50≤25μm；
可选地，所述B1颗粒在所述B颗粒中的重量占比选自50％～100％；
可选地，所述B2颗粒在所述B颗粒中的重量占比选自0％～50％；
可选地，所述A颗粒的Span值选自0.1～2.0；所述B1颗粒的Span值选自0.1～2.0；所述B2颗粒的Span值选自0.1～2.0；其中，Span＝(D v90-D v10)/D v50。
在区分小颗粒(A颗粒)与大颗粒(B颗粒)的基础上，进一步将B颗粒区分为B1颗粒和B2颗粒，使B1颗粒的D v50小于B2颗粒的D v50，如此，可以使正极活性材料包括三种尺寸级配的颗粒，并更精细地控制较大尺寸颗粒的粒径；进一步地，通过合理控制不同粒径颗粒的比例及宽化系数Span，在改善压实密度、提升正极极片的比容量和质量能量密度的同时，还可通过合理控制中间尺寸的B1颗粒含量更好地改善功率性能，可避免过度密堆积而影响电解液的浸润性，避免电解液无法接触到极片的内部活性材料而产生浓差以及由此对锂离子传输产生不利限制。
在本申请的一些实施方式中，所述B颗粒包括B1’颗粒和B2’颗粒和B3’颗粒，其中，所述B1’颗粒的粒径满足8μm<D v50≤12μm，所述B2’颗粒的粒径满足12μm<D v50≤15μm，所述B3’颗粒的粒径满足15μm<D v50≤20μm；
可选地，所述B1’颗粒在所述B颗粒中的重量占比选自40％～80％；
可选地，所述B2’颗粒在所述B颗粒中的重量占比选自20％～30％；
可选地，所述B3’颗粒在所述B颗粒中的重量占比选自0％～30％；
可选地，所述A颗粒的Span值选自0.1～2.0，所述B1’颗粒的Span值选自0.1～2.0，所述B2’颗粒的Span值选自0.1～2.0，所述B3’颗粒的Span值选自0.1～2.0；其中，Span＝(D v90-D v10)/D v50。
在区分小颗粒(A颗粒)与大颗粒(B颗粒)的基础上，进一步将B颗粒区分为D v50依次递增的B1’颗粒、B2’颗粒和B3’颗粒，使正极活性材料包括四种尺寸级配的颗粒，并更精细地控制较大尺寸颗粒的粒径；进一步地，通过合理控制四者比例及宽化系数Span，还可通过合理控制中间尺寸的B1’颗粒、B2’颗粒含量更好地改善功率性能，可避免过度密堆积而影响电解液的浸润性，避免电解液无法接触到极片的内部活性材料而产生浓差以及由此对锂离子传输产生不利限制。
在本申请的一些实施方式中，所述A颗粒和所述B颗粒各自独立地包含如下的元素组合Ni xCo yM 1-x-y，其中，x≥0.4，y≥0，(1-x-y)≥0；M元素包括Mn和Al中的一种或两种；
可选地，0.40≤x≤1.00，0≤y≤0.15，(1-x-y)≥0；
可选地，0.50≤x≤1.00；可选地，0.60≤x≤1.00；
可选地，y>0；可选地，0<y≤0.15；
可选地，(1-x-y)>0；
可选地，y>0，且(1-x-y)>0；
可选地，所述A颗粒和所述B颗粒各自独立地包括化学式为Li k-aQ a(Ni xCo yM 1-x-y) 1-zN zO 2-cX c的材料，其中，0.9≤k≤1.1，0≤a≤0.2，0.60≤x≤1.00，0≤y≤0.15，0≤(1-x-y)，0≤z≤0.5，0≤c≤1，M元素包括Mn和Al中的一种或两种，Q元素包括Na、K、Rb和Ca中的一种或多种，N元素包括Al、Ti、Zr、Nb、Sr、Sb、Y、Ba、Co、Mn、Mg、W、Si、Mo、P和C中的一种或多种，X元素包括B、F、S和Cl中的一种或多种；
可选地，0.92≤k≤1.08；可选地，0.95≤k≤1.05；可选地，0.96≤k≤1.04；可选地，0.98≤k≤1.02；可选地，0.99≤k≤1.01；可选地，k＝1；
可选地，0.50≤x≤1.00；可选地，0.60≤x≤1.00；可选地，0.70≤x1≤1.00；
可选地，其中，0≤a≤0.2，0.60≤x<1.00，0<y≤0.15，0<(1-x-y)，0≤z≤0.5，0≤c≤1。
在本申请的一些实施方式中，所述A颗粒和所述B颗粒中的镍锂摩尔比R Ni/Li各自独立地≥0.4；
可选地，所述A颗粒和所述B颗粒中的镍锂摩尔比R Ni/Li各自独立地≥0.5；
可选地，所述A颗粒和所述B颗粒中的镍锂摩尔比R Ni/Li各自独立地≥0.6；
可选地，所述A颗粒和所述B颗粒中的镍锂摩尔比R Ni/Li各自独立地≥0.7；
可选地，所述A颗粒和所述B颗粒中的镍锂摩尔比R Ni/Li各自独立地≥0.8；
可选地，所述A颗粒中的镍锂摩尔比R Ni/Li选自0.7～1.0；
可选地，所述B颗粒中的镍锂摩尔比R Ni/Li选自0.8～1.0；
可选地，所述B颗粒中的镍锂摩尔比R Ni/Li选自0.8～0.96。
传统的富镍正极材料(如富镍三元正极材料等)在循环过程中，晶胞参数会随着 脱嵌锂的发生而发生改变，晶胞参数的变化会使得材料产生内应力，随着充放电循环次数的增加，材料内部应力不断累加，进而使得材料发生结构相变和颗粒开裂等现象，会极大地破坏材料的可逆循环。在高电压体系中，富镍材料(如富镍三元材料等)的脱嵌锂程度会进一步加深。本申请中，正极活性材料可以采用传统的富镍三元正极材料。本申请中，还可以向三元正极活性材料中引入N元素的掺杂，可以降低材料的晶格变化程度，起到稳定晶格的作用，从而可以改善富镍三元材料的循环性能。此外，还有利于避免开裂产生的新界面加速与电解液之间的副反应，从而有利于改善电芯产气。
在本申请的一些实施方式中，所述A颗粒和所述B颗粒的真密度各自独立地大于4.0g/cc；
可选地，所述A颗粒和所述B颗粒的真密度各自独立地选自4.0g/cc～4.8g/cc；
可选地，所述A颗粒的真密度各自独立地选自4.6g/cc～4.8g/cc；
可选地，所述B颗粒的真密度各自独立地选自4.5g/cc～4.8g/cc。
在本申请中，真密度是决定正极材料压实密度的主要因素之一。通过合理控制A颗粒与B颗粒的真密度，有利于提高正极极片的体积比容量和能量密度，从而在改善高电压下材料开裂问题的同时，更好地改善电芯性能。对于本申请的级配方式的多颗粒体系，材料的颗粒搭配越紧密，正极材料理论可实现的体积比容量就越高。
在本申请的一些实施方式中，所述A颗粒和所述B颗粒各自独立地包括本体结构以及包覆在所述本体结构表面至少一部分的氧化物层；
其中，
所述本体结构包括化学式为Li k1-a1Q a1(Ni x1Co y1M 1-x1-y1) 1-z1N z1O 2的材料，其中，0.9≤k1≤1.1，0≤a1≤0.20，0.40≤x1≤1.00，0≤y1≤0.15，0≤(1-x1-y1)，0≤z1≤0.5，且Q元素包括Na、K、Rb和Ca中的一种或多种，M元素包括Mn和Al中的一种或两种，N元素包括Al、Ti、Zr、Nb、Sr、Sb、Y、Ba、Co、Mn、Mg、Si、P、Mo、C和W中的一种或多种；
可选地，0.92≤k1≤1.08；可选地，0.95≤k1≤1.05；可选地，0.96≤k1≤1.04；可选地，0.98≤k1≤1.02；可选地，0.99≤k1≤1.01；可选地，k1等于1；
可选地，0.50≤x1≤1.00；可选地，0.60≤x1≤1.00；可选地，0.9≤k2≤1.1，0.70≤x1≤1.00；
可选地，N元素包括Al、Ti、Zr、Nb、Sr、Sb、Y、Mg和W中的一种或多种；
可选地，0≤a1≤0.20，0.60≤x1<1.00，0<y1≤0.15，0<(1-x1-y1)，0≤z1≤0.5；
所述氧化物层包括化学式为Li k2-a2Q’ a2(Ni x2Co y2M’ 1-x2-y2) 1-z2N’ z2O 2-c2X c2的材料，其中，0≤a2≤0.20，0.40≤x2≤1.00，0≤y2≤0.15，0≤(1-x2-y2)，0<z2≤0.5，0≤c2≤1，且Q’元素包括Na、K、Rb和Ca中的一种或多种，M’元素包括Mn和Al中的一种或两种，N’元素包括Al、Ti、Zr、Nb、Sr、Sb、Y、Ba、Co、Mn、Mg、W、Mo、Si、C和P中的一种或多种，X元素包括B、Cl、S和F中的一种或多种；
可选地，0.92≤k2≤1.08；可选地，0.95≤k2≤1.05；可选地，0.96≤k2 ≤1.04；可选地，0.98≤k2≤1.02；可选地，0.99≤k2≤1.01；可选地，k2等于1；
可选地，0.50≤x2≤1.00；可选地，0.60≤x2≤1.00；可选地，0.70≤x2≤1.00；
可选地，Q’ a2Ni x2Co y2M’ 1-x-y与Q a1Ni x1Co y1M 1-x1-y1相同；
可选地，N’元素包括Al、Ti、Zr、Sr、Sb、Mo、Nb、Mg、Y和W中的一种或多种；
可选地，0≤a2≤0.20，0.60≤x2<1.00，0<y2≤0.15，0<(1-x2-y2)，0<z2≤0.5，0≤c2≤1。
在本申请中，可以在正极活性材料的本体结构中掺杂Q’元素(如Na、K、Rb、Ca等)，从而提升锂离子扩散系数，降低锂镍混排。还可以在正极活性材料表面进行包覆，在颗粒表面形成掺杂特定N’元素的氧化物层，可降低材料的表面与电解液的反应活性，减少材料释氧，提高活性材料的结构稳定性，提高离子电导率，还可以提升材料容量。比如，通过在氧化物层掺杂Zr、Al、Mg、W、Mo、Co、Sr、Sb、Nb等元素，其中，Mg、Ti、Al和Mo等元素可以降低材料在充放电循环过程中晶格变形量，从而提高材料的结构稳定性；比如，还可以向氧化物层中掺杂B、F和Cl等元素，从而提升容量和倍率性能。此外，通过将材料的颗粒尺寸设计与结构设计相结合，可以还使材料具有更高的比容量，并同时降低正极材料与电解液之间的副反应和相变的程度，使电池具有更低的瓦时成本和更高的循环寿命。相对于包覆层结构设计，无包覆层的材料界面有可能与电解液发生的大量副反应，导致电解液被氧化而生成二氧化碳和氧气等气体；而且，无包覆层时，正极活性材料表面层状结构更容易向岩盐结构转变，导致材料表面失去化学反应活性。
在本申请的一些实施方式中，所述氧化物层的厚度为0～100nm；
可选地，所述氧化物层的厚度为1nm～100nm；
可选地，所述氧化物层的厚度为1nm～20nm。
在本申请的一些实施方式中，所述氧化物层相对于所述本体结构的质量百分比为0.01％～5％；
可选地，所述氧化物层相对于所述本体结构的质量百分比为0.05％～4％。
在本申请的一些实施方式中，所述氧化物层中的N元素在所述正极活性材料中的质量占比为0.01％～4％；
可选地，所述氧化物层中的N元素在所述正极活性材料中的质量占比为0.05％～4％。
通过合理控制表面氧化物层的量，比如氧化物层的厚度、氧化物层所占质量百分比、N元素掺杂量等参数，能够更好实现前述掺杂、包覆目的，更好地调节材料的化学反应活性和结构稳定性，更好地将材料的颗粒尺寸设计与结构设计相结合，还同时赋予材料更高比容量，降低正极材料与电解液之间的副反应和相变的程度，使电池具有更低的瓦时成本和更高的循环寿命。
在本申请的一些实施方式中，所述正极活性材料的比表面积平均值为0.3cm 2/g～1.5cm 2/g。
通过合理控制正极活性材料的整体比表面积，更有利于在提升正极材料压实密度的情况下尽可能提高能量密度。
在本申请的一些实施方式中，所述正极活性材料中的游离锂含量小于3000ppm，以质量比计。
在本申请中，可通过合理控制正极活性材料中的游离锂(如碳酸锂、氢氧化锂等)含量，从而避免在高电压条件下的循环过程中过多产气。如果游离锂偏高，在高电压条件下的循环过程中会与电解液分解产生的氢氟酸发生酸碱中和反应，并产生大量气体，使得电芯胀气和鼓包影响电芯，容易发生电芯安全事故。
在本申请的一些实施方式中，所述正极活性材料的I003晶粒含量与I104晶粒含量之比I003/I104≥1.2，以XRD图谱中I003晶面与I104晶面的特征峰面积之比计；
可选地，I003/I104选自1.2～2；
可选地，I003/I104选自1.3～2；
可选地，I003/I104选自1.3～1.6。
通过合理控制正极活性材料的I003晶粒含量与I104晶粒含量之比I003/I104(如≥1.2)，可以更好地控制锂镍混排的程度，避免过多镍元素占据锂元素晶格位置而导致可逆容量的降低和锂离子的扩散系数降低。
在本申请的一些实施方式中，在所述B颗粒中，至少一部分的一次颗粒沿径向方向定向排列。
对于本申请的二次球颗粒，可使一次颗粒沿径向方向产生一定的定向排列，从而抑制高电压下可能产生的收缩膨胀，避免内部应力增大，从而更好地防止材料在高电压下破碎，此外还可改善循环性能。沿径向的定向排列程度越高，无定向的无规排列程度越低，效果改善程度越明显。
第二方面，本申请提供一种正极极片，其包括正极集流体以及位于所述正极集流体至少一个表面上的正极活性材料层，所述正极活性材料层包含本申请第一方面所述的正极活性材料。
采用本申请第一方面的正极活性材料可制备高镍含量的正极极片，能够利用正极活性材料的颗粒尺寸及含量设计，避免材料在高电压下开裂，改善高电压条件下的电芯循环和存储性能，进一步还可利用掺杂和/或包覆结构设计调节材料的化学反应活性和结构稳定性，可以使材料具有更高的比容量，同时降低正极材料与电解液之间的副反应和相变的程度，使电池具有更低的瓦时成本和更高的循环寿命。
在本申请的一些实施方式中，所述正极极片的压实密度为3.3g/cm 3～3.7g/cm 3。
在本申请中，通过控制正极极片在较合适的压实密度，可以在赋予极片更好的比容量及能量密度的情况下，更好地避免高电压条件材料开裂。应当理解，正极极片的压实密度还受到其中包含的A颗粒及B颗粒的真密度的限制。极片的压实密度的提升，可以提高材料的体积比容量，使得电芯在更小的体积具有更长的续航。
第三方面，本申请提供一种电化学储能装置，其包括本申请第二方面所述正极极片、负极极片以及隔离膜，其中，所述隔离膜设置于所述正极极片和所述负极极片之间。
第四方面，本申请提供一种二次电池，其包括本申请第二方面所述正极极片以及本申请第三方面所述电化学储能装置中至少一种。
第五方面，本申请提供一种用电装置，其包括本申请第二方面所述正极极片，本申请第三方面所述电化学储能装置以及本申请第四方面所述二次电池中至少一种。
采用本申请第一方面的正极活性材料制备高镍含量的正极极片，进而制备电化学储能装置、二次电池、用电装置，能够利用正极活性材料的颗粒尺寸及含量设计，避免材料在高电压下开裂，改善高电压条件下的电芯循环和存储性能，进一步还可利用掺杂和/或包覆结构设计调节材料的化学反应活性和结构稳定性，可以使材料具有更高的比容量，同时降低正极材料与电解液之间的副反应和相变的程度，使电池具有更低的瓦时成本和更高的循环寿命。
本申请第六方面，提供一种正极活性材料的制备方法，其包括如下步骤：将所述A颗粒和所述B颗粒按照预设质量比进行混合，制备得到所述正极活性材料；所述A颗粒和B颗粒如本申请第一方面所定义；
其中，所述A颗粒采用包括如下步骤的方法制备得到：将氢氧化锂、镍钴M体前驱体材料Ni xCo yM 1-x-y(OH) 2以及可选的Q添加剂和可选的N添加剂混合，在氧气存在及温度T1条件下进行一次烧结；可选地，向一次烧结产物中加入X添加剂和N添加剂中至少一种，混合，在氧气存在下进行二次烧结；
其中，所述B颗粒采用包括如下步骤的方法制备得到：将氢氧化锂、镍钴M体前驱体材料Ni xCo yM 1-x-y(OH) 2以及可选的Q添加剂和可选的N添加剂混合，在氧气存在及温度T2条件下进行一次烧结；可选的，向一次烧结产物中加入X添加剂和N添加剂中至少一种，混合，在氧气存在下进行二次烧结；
其中，所述Q添加剂、N添加剂、X添加剂分别为含有Q元素的添加剂、含有N元素的添加剂、含有X元素的添加剂；
其中，x、y、M元素、Q元素、X元素和N元素如本申请第一方面所定义；
所述温度T1高于所述温度T2；
可选地，制备所述A颗粒的步骤中，在氧气存在条件下烧结的步骤中，一次烧结温度为700℃～950℃，可选地750℃～900℃，二次烧结温度为300℃～600℃，可选地350℃～550℃；
可选地，制备所述B颗粒的步骤中，在氧气存在条件下烧结的步骤中，一次烧结温度为700℃～900℃，可选地750℃～850℃，二次烧结温度为300℃～600℃，可选地350℃～550℃
本申请第一方面中提供的正极活性颗粒(A颗粒或B颗粒)表面包覆有氧化物层时，可以采用分步烧结方法，先将本体结构的前驱体在氧化氛围、较高温度条件下烧结(如A颗粒在700℃～950℃，又如B颗粒在700℃～900℃)形成本体结构，然后与包覆层添加剂混合在氧化氛围中、较低温度条件下进行烧结(如300℃～600℃)形成氧化物层，从而制备得到带有包覆层的A颗粒或B颗粒。一次烧结时，在较高烧结温度条件下，颗粒内部粒子容易连结。因此，可以在相对较高的一次烧结温度(T1)下，使粒子充分连结制备得到大尺寸的单晶或类单晶颗粒(A颗粒)，可以在相对较 低的一次烧结温度(T2)下制备得到小尺寸的二次颗粒(B颗粒)，此时，二次颗粒中的细小粒子未连结或仅部分连结。
本申请的一个或多个实施例的细节在下面的附图和描述中提出。本申请的其他特征、目的和优点将从说明书、附图以及权利要求书变得明显。
附图说明
为了更好地描述和说明这里公开的那些申请的实施例或示例，可以参考一幅或多幅附图。用于描述附图的附加细节或示例不应当被认为是对所公开的申请、目前描述的实施例或示例以及目前理解的这些申请的最佳模式中的任何一者的范围的限制。而且在全部附图中，用相同的附图标号表示相同的部件。在附图中：
图1是本申请一实施例中A颗粒和B颗粒的结构示意图，其中，A颗粒具有单晶或类单晶的结构，B颗粒为包括多个一次颗粒的二次颗粒；(a)中的A颗粒和B颗粒均无包覆层，(b)中的A颗粒和B颗粒均有包覆层；
图2是本申请一实施例中的A颗粒原料的SEM图(1000倍显示)，图中标尺为20μm；
图3是本申请一实施例中的A颗粒原料的SEM图(10000倍显示)，图中标尺为2μm；
图4是本申请一实施例中的B颗粒原料的SEM图(1000倍显示)，图中标尺为20μm；
图5是本申请一实施例中的B颗粒原料的SEM图(10000倍显示)，图中标尺为2μm；
图6是本申请一实施例中的B颗粒原料的截面SEM图，图中标尺为3μm；
图7是本申请一实施例中正极极片的结构示意图，其中A颗粒的D v50小于B颗粒的D v50，A颗粒的质量占比大于等于B颗粒的质量占比；
图8是本申请一实施例中正极极片的结构示意图，其包括A颗粒、B1颗粒和B2颗粒，A颗粒、B1颗粒和B2颗粒的D v50依次递增，A颗粒的质量占比大于等于B1颗粒和B2颗粒的质量占比之和；
图9是本申请一实施例的二次电池的示意图；
图10是图9所示的本申请一实施例的二次电池的分解图；
图11是本申请一实施例的二次电池用作电源的用电装置的示意图。
附图标记说明：
5，二次电池；51，壳体；52，电极组件；53，盖板；6，用电装置。
具体实施方式
以下，适当地参照附图详细说明公开了本申请的正极活性材料、正极极片、电化学储能装置、二次电池、用电装置和制备方法的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。进一步地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
本申请中涉及“多个”、“多种”、“多次”等，如无特别限定，指在数量上大于2或等于2。例如，“一种或多种”表示一种或大于等于两种。
本文中所使用的“其组合”、“其任意组合”、“其任意组合方式”等中包括所列项目中任两个或任两个以上项目的所有合适的组合方式。
本文中，“合适的组合方式”、“合适的方式”、“任意合适的方式”等中所述“合适”，以能够实施本申请的技术方案为准。
本文中，“优选”、“更好”、“更佳”、“为宜”仅为描述效果更好的实施方式或实施例，应当理解，并不构成对本申请保护范围的限制。如果一个技术方案中出现多处“优选”，如无特别说明，且无矛盾之处或相互制约关系，则每项“优选”各自独立。
本申请中，“进一步”、“更进一步”、“特别”等用于描述目的，表示内容上 的差异，但并不应理解为对本申请保护范围的限制。
本申请中，“第一方面”、“第二方面”、“第三方面”、“第四方面”等中，术语“第一”、“第二”、“第三”、“第四”等仅用于描述目的，不能理解为指示或暗示相对重要性或数量，也不能理解为隐含指明所指示的技术特征的重要性或数量。而且“第一”、“第二”、“第三”、“第四”等仅起到非穷举式的列举描述目的，应当理解并不构成对数量的封闭式限定。
本申请中，术语“室温”一般指4℃～35℃，较佳地指20℃±5℃。在本申请的一些实施例中，室温是指20℃～30℃。
在本申请中，涉及数据范围的单位，如果仅在右端点后带有单位，则表示左端点和右端点的单位是相同的。比如，3～5h或3-5h均表示左端点“3”和右端点“5”的单位都是h(小时)。
本申请实施例说明书中所提到的相关成分的质量或重量不仅仅可以指代各组分的含量，也可以表示各组分间质量或重量的比例关系，因此，只要是按照本申请实施例说明书相关组分的含量按比例放大或缩小均在本申请实施例说明书公开的范围之内。进一步地，本申请实施例说明书中所述的质量或重量可以是μg、mg、g、kg等化工领域公知的质量或重量单位。
随着碳中和与碳达峰战略目标的实施，新能源行业近年来迅猛发展。然而目前新能源车存在续航低和寿命差的问题，极大限制了新能源产业的发展，成为实现碳中和与碳达峰道路上的绊脚石。因此，开发高能量密度和长使用寿命的储能装置迫在眉睫。
对于正极材料，高镍材料(如高镍三元材料等)具有高容量和循环衰减低的特点，受到行业的广泛关注。然而目前高镍材料瓦时成本高，制约了其推广应用。降低材料瓦时成本的有效手段之一是提升材料的质量能量密度。目前提升高镍材料(如高镍三元材料等)质量能量密度常用的方式主要包括提高充放电电压和增加正极材料中镍含量。由于正极原材料的价格奇高，使得提升材料的充放电电压成为提升材料质量能量密度最具有吸引力的方式。然而，对于传统的高镍材料(如高镍三元材料等)，提升电压会造成材料循环过程中开裂程度加深，循环寿命下降，同时存储过程中由于正极氧化活性增强，容易与电解液发生剧烈化学反应造成电芯寿命下降，单位容量产气上升，综合导致高镍材料在高电压条件下不稳定，从而导致利用提高充放电电压改善质量能量密度存在应用障碍，据申请人调研，尚未见相关报道。
根据本申请发明人的大量实验探索发现，将传统的富镍材料(如富镍三元正极材料等)在高电压条件下(如无指4.3及以上电压时)进行充放电循环时，电芯性能会表现为循环过程中容量保持率随着循环圈数的增加快速衰减，同时电芯的直流电阻增长过大。在电芯日历寿命测试中，存储容量衰减和产气恶化。发明人推测，很可能是因为富镍正极材料(如富镍三元正极材料等)在循环过程中锂离子的嵌入和脱出，使得材料晶格发生收缩和膨胀，特别是高电压条件下，材料收缩和膨胀程度加深，材料易发生破裂，而破裂产生的新鲜界面正极于电解液发生副反应，造成电芯性能恶化。此外，高电压条件下，正极的氧化性更强，易将电解液中有机溶剂氧化生成二氧化碳、氧气等气体，导致电芯产气量增加。
在本申请的上下文中，如无特别说明，高电压条件指电压≥4.3V。
基于此，第一方面，本申请提供了一种正极活性材料，其包括A颗粒和B颗粒，所述A颗粒和所述B颗粒中的镍元素相对于锂元素的摩尔比(可记为镍锂摩尔比R Ni/Li)各自独立地≥0.33；其中，所述A颗粒具有单晶或类单晶的结构，所述B颗粒为包括多个一次颗粒的二次颗粒，其中，所述A颗粒的D v50小于所述B颗粒的D v50，所述A颗粒的质量占比大于等于所述B颗粒的质量占比；
其中，D vN表示材料的累计体积分布百分数达到N％时对应的粒径，N为选自0～100的数值。
前述正极活性材料中A颗粒和B颗粒的结构可参阅图1(a)。
在申请中，“富镍”、“高镍”具有相同含义，可以互换使用，指正极活性材料中的镍比例较高。以NCM811三元正极材料为例，其中的镍、钴、锰的摩尔比例为80：10：10。在正极活性材料中中提高镍含量有利于提升能量密度，可以改善电池容量。
在本申请中，对于正极活性材料、正极材料、正极极片而言，可以采用镍元素和锂元素的摩尔比来表征镍含量，该摩尔比可称为镍锂摩尔比，可记为R Ni/Li。在本申请中，R Ni/Li每次出现，可以独立地大于等于0.33，进一步地可以独立地大于等于0.4，更进一步地可以独立地大于等于0.5，更进一步地可以独立地大于等于0.6，更进一步地可以独立地大于等于0.7，更进一步地可以独立地大于等于0.8。在本申请的一些实施方式中，镍锂摩尔比R Ni/Li还可以选自如下任一种数值或任两种数值构成的区间：0.33、1/3、0.4、0.45、0.5、0.55、0.6、0.65、0.7、0.75、0.8、0.02、0.05、0.9、0.95、1等。在本申请的一些实施方式中，镍锂摩尔比R Ni/Li还可以选自如下的任一种数值区间(此处的任一个数值端点可以独立地包含或不包含)：0.4～1、0.5～1、0.6～1、0.7～1、0.8～1、0.8～0.96等。
在本申请的上下文中，可采用体积累计分布粒径D vN(其中，N表示选自0～100的任意数值)来表征材料的粒径尺寸，指材料的累计体积分布百分数达到N％时所对应的粒径，粒径小于等于D vN的体积占比为N％。D vN可以从材料粒径的体积累积分布曲线上获得，如无其他说明，体积累积分布曲线自小粒径侧从零开始累计。以D v99、D v90、D v50、D v10为例，D v99是指材料的累计体积分布百分数达到99％时所对应的粒径；D v90是指材料的累计体积分布百分数达到90％时所对应的粒径；D v50是指材料的累计体积分布百分数达到50％时所对应的粒径；D v10是指材料的累计体积分布百分数达到10％时所对应的粒径。以D v50为例，表示占材料体积50％的颗粒粒径小于等于D v50，且占材料体积50％的颗粒粒径大于D v50。以D v90为例，表示占材料体积90％的颗粒粒径小于等于D v90，且占材料体积10％的颗粒粒径大于D v90。以D v10为例，表示占材料体积10％的颗粒粒径小于等于D v10，且占材料体积90％的颗粒粒径大于D v10。本领域技术人员可以理解D v99、D v90、D v50、D v10的含义，而且可以采用本领域公知的仪器及方法进行测定。例如可以参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪方便地测定，如英国马尔文仪器有限公司的Mastersizer 2000E型激光粒度分析仪、LS-909激光粒度仪(欧美克)。
在本申请中，类单晶通常是指一次颗粒的尺寸大于1μm，但一次颗粒存在一定团 聚；单晶通常是指一次颗粒的尺寸大于1μm，且无明显团聚。
在本申请中，“一次颗粒”和“二次颗粒”为本领域所熟知的术语。“一次颗粒”指单晶晶粒。“二次颗粒”指由两个或两个以上一次颗粒聚集而成的团聚态的颗粒。一次颗粒和二次颗粒可以通过使用扫描电子显微镜拍摄SEM图像容易地区分。
传统的高镍材料(如高镍三元材料等)在循环过程中容易发生材料开裂，而且在高电压下开裂程度容易加深，导致循环寿命下降，而且存储过程中由于正极氧化活性增强，容易与电解液接触而发生剧烈化学反应造成电芯寿命下降，单位容量产气上升。在本申请中，该正极活性材料包括不同颗粒尺寸的高镍正极材料，其中，通过D v50区分小颗粒与大颗粒，以具有单晶或类单晶结构的A颗粒作为小颗粒，以一次颗粒团聚而成的B颗粒作为大颗粒，还控制A颗粒的质量含量高于B颗粒；特殊晶相结构的A颗粒具有均相体系或近均相体相，在材料脱嵌锂过程中，材料内部不容易产生应力，因而不易造成材料的应力作用下开裂，也因此更有利于改善高电压条件下的电芯循环和存储性能；B颗粒采用一次颗粒团聚而成，有利于提升功率性能和压实密度，通过控制A颗粒与B颗粒之间含量，控制B颗粒的含量小于A颗粒，能够降低大颗粒晶格发生收缩和膨胀而导致的应力，从而避免正极材料在高电压条件下开裂，避免因材料的破裂产生新界面，进而避免新界面与电解液发生副反应而导致的恶化电芯性能及产气加剧，从而增强高电压条件下的循环稳定性，延长电芯使用寿命；进一步地，小尺寸的A颗粒含量的增加还有利于提升电芯的存储容量保持率，提高材料的存储日历寿命。此外，小尺寸的A颗粒采用纯单晶体系，相比混合体系，材料的极片压密和电芯功率性能会明显降低，而极片的压实密度的提升，可以提高材料的体积比容量，使得电芯在更小的体积具有更长的续航。
在一些实施方式中，所述A颗粒的粒径满足2μm≤D v50≤5μm，所述A颗粒的D v50还可以选自如下任一种粒径或任两种构成的区间：2μm、2.5μm、3μm、3.5μm、4μm、4.5μm、5μm等。
在一些实施方式中，所述B颗粒的粒径满足5μm<D v50≤25μm，所述B颗粒的D v50还可以选自如下任一种粒径或任两种构成的区间：5.1μm、5.2μm、5.3μm、5.4μm、5.5μm、6μm、6.5μm、7μm、7.5μm、8μm、8.5μm、9μm、9.5μm、10μm、10.5μm、11μm、11.5μm、12μm、12.5μm、13μm、13.5μm、14μm、14.5μm、15μm、15.5μm、16μm、16.5μm、17μm、17.5μm、18μm、18.5μm、19μm、19.5μm、20μm、20.5μm、21μm、21.5μm、22μm、22.5μm、23μm、23.5μm、24μm、24.5μm、25μm等。
在一些实施方式中，所述A颗粒的粒径满足2μm≤D v50≤5μm，所述B颗粒的粒径满足5μm<D v50≤25μm。
在本申请中，还定义多颗粒体系材料的宽化系数Span＝(D v90-D v10)/D v50。宽化系数Span可表示颗粒粒径的分散程度，宽化系数Span越大，从分布上表现材料的颗粒分布越宽。
在一些实施方式中，所述A颗粒的Span值大于所述B颗粒的Span值。
在一些实施方式中，所述A颗粒的Span值选自0.1～3.0，进一步可以选自0.1～2.0，非限制性示例如0.1、0.15、0.2、0.25、0.3、0.35、0.4、0.45、0.5、0.55、0.6、0.65、 0.7、0.75、0.8、0.85、0.9、0.95、1.0、1.05、1.1、1.15、1.2、1.25、1.3、1.35、1.4、1.45、1.5、1.55、1.6、1.65、1.7、1.75、1.8、1.85、1.9、1.95、2.0、2.1、2.2、2.3、2.4、2.5、2.6、2.7、2.8、2.9等。
所述B颗粒的Span值选自0.1～3.0，进一步可以选自0.1～2.0，更进一步可以选自1.1～2.0，非限制性示例如0.1、0.15、0.2、0.25、0.3、0.35、0.4、0.45、0.5、0.55、0.6、0.65、0.7、0.75、0.8、0.85、0.9、0.95、1.0、1.05、1.1、1.15、1.2、1.25、1.3、1.35、1.4、1.45、1.5、1.55、1.6、1.65、1.7、1.75、1.8、1.85、1.9、1.95、2.0、2.1、2.2、2.3、2.4、2.5、2.6、2.7、2.8、2.等。
在一些实施方式中，所述A颗粒的Span值选自0.1～2.0；所述B颗粒的Span值选自0.1～2.0。
在一些实施方式中，所述B颗粒的粒径满足8μm<D v50≤20μm。
通过控制A颗粒和B颗粒各自的粒径在较合适的范围，有利于更好地提高正极材料的高压耐受性，降低大颗粒导致的应力，进而更好地避免正极材料在高电压条件下开裂，增强高电压条件下的循环稳定性，避免产气加剧，延长电芯使用寿命，进一步地，还更加有利于提升正极极片的比容量和质量能量密度。通过合理搭配大小颗粒的粒径级配及宽化系数组合，可使得材料极片的压实密度越高，越有利于提高材料的体积比容量，使得电芯在更小的体积具有更长的续航。
在一些实施方式中，所述B颗粒包括B1颗粒和B2颗粒，且所述B1颗粒的D v50小于所述B2颗粒的D v50。
进一步地，在一些实施方式中，所述B1颗粒的粒径满足5μm<D v50≤10μm，所述B2颗粒的粒径满足10μm<D v50≤25μm。
在一些实施方式中，所述B1颗粒的粒径满足5μm<D v50≤10μm，所述B1颗粒的D v50还可以选自如下任一种粒径或任两种构成的区间：5.1μm、5.2μm、5.3μm、5.4μm、5.5μm、6μm、6.5μm、7μm、7.5μm、8μm、8.5μm、9μm、9.5μm、10μm等。
在一些实施方式中，所述B2颗粒的粒径满足10μm<D v50≤25μm，所述B2颗粒的D v50还可以选自如下任一种粒径或任两种构成的区间：10.1μm、10.2μm、10.3μm、10.4μm、10.5μm、11μm、11.5μm、12μm、12.5μm、13μm、13.5μm、14μm、14.5μm、15μm、15.5μm、16μm、16.5μm、17μm、17.5μm、18μm、18.5μm、19μm、19.5μm、20μm、20.5μm、21μm、21.5μm、22μm、22.5μm、23μm、23.5μm、24μm、24.5μm、25μm等。
在一些实施方式中，所述B1颗粒在所述B颗粒中的重量占比可以选自50％～100％，还可以选自如下任一种百分数或任两种百分数构成的区间：50％、55％、60％、65％、70％、75％、80％、85％、90％、95％等。
在一些实施方式中，所述B2颗粒在所述B颗粒中的重量占比可以选自0％～50％，还可以选自如下任一种百分数或任两种百分数构成的区间：5％、10％、15％、20％、25％、30％、35％、40％、45％、50％等。
在一些实施方式中，所述A颗粒的Span值可以选自0.1～2.0，非限制性示例如0.1、 0.15、0.2、0.25、0.3、0.35、0.4、0.45、0.5、0.55、0.6、0.65、0.7、0.75、0.8、0.85、0.9、0.95、1.0、1.05、1.1、1.15、1.2、1.25、1.3、1.35、1.4、1.45、1.5、1.55、1.6、1.65、1.7、1.75、1.8、1.85、1.9、1.95、2.0等。
在一些实施方式中，所述B1颗粒的Span值可以选自0.1～2.0，非限制性示例如0.1、0.15、0.2、0.25、0.3、0.35、0.4、0.45、0.5、0.55、0.6、0.65、0.7、0.75、0.8、0.85、0.9、0.95、1.0、1.0、1.05、1.1、1.15、1.2、1.25、1.3、1.35、1.4、1.45、1.5、1.55、1.6、1.65、1.7、1.75、1.8、1.85、1.9、1.95、2.0等。
在一些实施方式中，所述B2颗粒的Span值可以选自0.1～2.0，非限制性示例如0.1、0.15、0.2、0.25、0.3、0.35、0.4、0.45、0.5、0.55、0.6、0.65、0.7、0.75、0.8、0.85、0.9、0.95、1.0、1.05、1.1、1.15、1.2、1.25、1.3、1.35、1.4、1.45、1.5、1.55、1.6、1.65、1.7、1.75、1.8、1.85、1.9、1.95、2.0等。
在一些实施方式中，所述A颗粒的Span值选自0.1～2.0；所述B1颗粒的Span值选自0.1～2.0；所述B2颗粒的Span值选自0.1～2.0；其中，Span的定义与前述一致，Span＝(D v90-D v10)/D v50。
在区分小颗粒(A颗粒)与大颗粒(B颗粒)的基础上，进一步将B颗粒区分为B1颗粒和B2颗粒，使B1颗粒的D v50小于B2颗粒的D v50，如此，可以使正极活性材料包括三种尺寸级配的颗粒，并更精细地控制较大尺寸颗粒的粒径；进一步地，通过合理控制不同粒径颗粒的比例及宽化系数Span，在改善压实密度、提升正极极片的比容量和质量能量密度的同时，还可通过合理控制中间尺寸的B1颗粒含量更好地改善功率性能，可避免过度密堆积而影响电解液的浸润性，避免电解液无法接触到极片的内部活性材料而产生浓差以及由此对锂离子传输产生不利限制。
在一些实施方式中，所述B颗粒包括B1’颗粒和B2’颗粒和B3’颗粒，且所述B1’颗粒、所述B2’颗粒和所述B3’颗粒D v50依次递增。
进一步地，在一些实施方式中，所述B1’颗粒的粒径满足8μm<D v50≤12μm，所述B2’颗粒的粒径满足12μm<D v50≤15μm，所述B3’颗粒的粒径满足15μm<D v50≤20μm。
在一些实施方式中，所述B1’颗粒的粒径满足8μm<D v50≤12μm，所述B1颗粒的D v50还可以选自如下任一种粒径或任两种构成的区间：8.1μm、8.2μm、8.3μm、8.4μm、8.5μm、9μm、9.5μm、10μm、10.5μm、11μm、11.5μm、12μm等。
在一些实施方式中，所述B2’颗粒的粒径满足12μm<D v50≤15μm，所述B2颗粒的D v50还可以选自如下任一种粒径或任两种构成的区间：12.1μm、12.2μm、12.3μm、12.4μm、12.5μm、13μm、13.5μm、14μm、14.5μm、15μm等。
在一些实施方式中，所述B3’颗粒的粒径满足15μm<D v50≤20μm，所述B2颗粒的D v50还可以选自如下任一种粒径或任两种构成的区间：15.1μm、15.2μm、15.3μm、15.4μm、15.5μm、16μm、16.5μm、17μm、17.5μm、18μm、18.5μm、19μm、19.5μm、20μm等。
在一些实施方式中，所述B1’颗粒在所述B颗粒中的重量占比选自40％～80％，还可以选自如下任一种百分数或任两种百分数构成的区间：40％、45％、50％、55％、60％、 65％、70％、75％、80％等。
在一些实施方式中，所述B2’颗粒在所述B颗粒中的重量占比选自20％～30％，还可以选自如下任一种百分数或任两种百分数构成的区间：20％、21％、22％、23％、24％、25％、26％、27％、8％、9％、30％等。
在一些实施方式中，所述B3’颗粒在所述B颗粒中的重量占比选自0％～30％，还可以选自如下任一种百分数或任两种百分数构成的区间：2％、4％、5％、6％、8％、10％、12％、15％、16％、18％、20％、21％、22％、23％、24％、25％、26％、27％、8％、9％、30％等。
在一些实施方式中，所述A颗粒的Span值可以选自0.1～2.0，非限制性示例如0.1、0.15、0.2、0.25、0.3、0.35、0.4、0.45、0.5、0.55、0.6、0.65、0.7、0.75、0.8、0.85、0.9、0.95、1.0、1.05、1.1、1.15、1.2、1.25、1.3、1.35、1.4、1.45、1.5、1.55、1.6、1.65、1.7、1.75、1.8、1.85、1.9、1.95、2.0等。
在一些实施方式中，所述B1’颗粒的Span值可以选自0.1～2.0，非限制性示例如0.1、0.15、0.2、0.25、0.3、0.35、0.4、0.45、0.5、0.55、0.6、0.65、0.7、0.75、0.8、0.85、0.9、0.95、1.0、1.05、1.1、1.15、1.2、1.25、1.3、1.35、1.4、1.45、1.5、1.55、1.6、1.65、1.7、1.75、1.8、1.85、1.9、1.95、2.0等。
在一些实施方式中，所述B2’颗粒的Span值可以选自0.1～2.0，非限制性示例如0.1、0.15、0.2、0.25、0.3、0.35、0.4、0.45、0.5、0.55、0.6、0.65、0.7、0.75、0.8、0.85、0.9、0.95、1.0、1.05、1.1、1.15、1.2、1.25、1.3、1.35、1.4、1.45、1.5、1.55、1.6、1.65、1.7、1.75、1.8、1.85、1.9、1.95、2.0等。
在一些实施方式中，所述B3’颗粒的Span值可以选自0.1～2.0，进一步可以选自0.1～1.4，非限制性示例如0.1、0.15、0.2、0.25、0.3、0.35、0.4、0.45、0.5、0.55、0.6、0.65、0.7、0.75、0.8、0.85、0.9、0.95、1.0、1.05、1.1、1.15、1.2、1.25、1.3、1.35、1.4、1.45、1.5、1.55、1.6、1.65、1.7、1.75、1.8、1.85、1.9、1.95、2.0等。
在一些实施方式中，所述A颗粒的Span值选自0.1～1.5，所述B1’颗粒的Span值选自0.1～1.5，所述B2’颗粒的Span值选自0.1～1.4，所述B3’颗粒的Span值选自0.1～1.4；其中，Span的定义与前述一致，Span＝(D v90-D v10)/D v50。
在区分小颗粒(A颗粒)与大颗粒(B颗粒)的基础上，进一步将B颗粒区分为D v50依次递增的B1’颗粒、B2’颗粒和B3’颗粒，使正极活性材料包括四种尺寸级配的颗粒，并更精细地控制较大尺寸颗粒的粒径；进一步地，通过合理控制四者比例及宽化系数Span，在更好地改善压实密度、提升正极极片的比容量和质量能量密度的同时，还可通过合理控制中间尺寸的B1’颗粒、B2’颗粒含量更好地改善功率性能，可避免过度密堆积而影响电解液的浸润性，避免电解液无法接触到极片的内部活性材料而产生浓差以及由此对锂离子传输产生不利限制。
在一些实施方式中，所述A颗粒和所述B颗粒各自独立地包含如下的元素组合Ni xCo yM 1-x-y，其中，x≥0.4，y≥0，(1-x-y)≥0；M元素包括Mn和Al中的一种或两种。在其中的一些实施例中，0.40≤x≤1.00，0≤y≤0.15，(1-x-y)≥0。前述的x可以独立地选自前文描述的任意合适值。在一些实施例中，0.50≤x≤1.00。在一些实施例 中，0.60≤x≤1.00。在一些实施例中，y>0；进一步地，可以满足0<y≤0.15，此时，存在钴，可以增加电池循环和倍率性能，还可以抑制阳离子混排(包括锂镍混排)从而提高材料稳定性。在一些实施例中，(1-x-y)>0，此时，可以存在锰和铝中的一种或两种；其中，引入锰可以其他改善电池安全性的作用；引入铝可以抑制阳离子混排，提高循环性能。在一些实施例中，所述正极活性材料中不含钴，有利于降低成本。
在一些实施方式中，y>0，且(1-x-y)>0，此时，可以存在镍、钴和M三元材料，其中，M的示例如锰和铝中至少一种，进一步地如锰或铝。此时，有利于实现能量密度、电池容量、倍率性能、循环性能、电池稳定性等方面优良综合性能。
在一些实施方式中，所述A颗粒和所述B颗粒各自独立地包括化学式为Li k-aQ a(Ni xCo yM 1-x-y) 1-zN zO 2-cX c的材料，其中，0.9≤k≤1.1，0≤a≤0.2，0.60≤x≤1.00，0≤y≤0.15，0≤(1-x-y)，0≤z≤0.5，0≤c≤1，M元素可以包括Mn和Al中的一种或两种，Q元素可以包括Na、K、Rb和Ca中的一种或多种，N元素可以包括Al、Ti、Zr、Nb、Sr、Sb、Y、Ba、Co、Mn、Mg、W、Si、Mo、P和C中的一种或多种，X元素可以包括B、F、S和Cl中的一种或多种。在一些实施方式中，0.92≤k≤1.08；可选地，0.95≤k≤1.05；可选地，0.96≤k≤1.04；可选地，0.98≤k≤1.02；可选地，0.99≤k≤1.01；可选地，k＝1。在其中的一些实施方式中，0.50≤x≤1.00；可选地，0.60≤x≤1.00；可选地，0.70≤x1≤1.00。在其中的另一些实施方式中，0≤a≤0.2，0.60≤x<1.00，0<y≤0.15(含钴)，0<(1-x-y)(可以含锰和铝中至少一种)，0≤z≤0.5，0≤c≤1。
在一些实施方式中，所述A颗粒(或B颗粒)的材料化学式为Li(Ni 0.8Co 0.1Mn 0.1) 0.95Zr 0.03Al 0.02O 2，此时，镍锂摩尔比R Ni/Li为0.76。
在一些实施方式中，所述A颗粒和所述B颗粒中的镍元素相对于锂元素的摩尔比R Ni/Li各自独立地≥0.33。在一些实施例中，所述A颗粒中的镍锂摩尔比R Ni/Li独立地≥0.3，还可以独立地≥0.4，还可以独立地≥0.5，还可以独立地≥0.6，还可以独立地≥0.7，还可以独立地≥0.8。在一些实施例中，所述B颗粒中的镍锂摩尔比R Ni/Li独立地≥0.3，还可以独立地≥0.4，还可以独立地≥0.5，还可以独立地≥0.6，还可以独立地≥0.7，还可以独立地≥0.8。在一些实施例中，所述A颗粒和所述B颗粒中的镍锂摩尔比R Ni/Li还可以各自独立地选自如下任一种数值或任两种数值构成的区间：0.33、1/3、0.4、0.45、0.5、0.55、0.6、0.65、0.7、0.75、0.8、0.02、0.05、0.9、0.95、1等。在本申请的一些实施方式中，所述A颗粒和所述B颗粒中的镍锂摩尔比R Ni/Li还可以各自独立地选自如下的任一种数值区间(此处的任一个数值端点可以独立地包含或不包含)：0.4～1、0.5～1、0.6～1、0.7～1、0.8～1、0.8～0.96等。在一些实施例中，所述A颗粒中的镍锂摩尔比R Ni/Li选自0.7～1.0。在一些实施例中，所述B颗粒中的镍锂摩尔比R Ni/Li选自0.8～1.0。在一些实施例中，所述B颗粒中的镍锂摩尔比R Ni/Li选自0.8～0.96。
传统的富镍正极材料(如富镍三元正极材料)在循环过程中，晶胞参数会随着脱嵌锂的发生而发生改变，晶胞参数的变化会使得材料产生内应力，随着充放电循环次数的增加，材料内部应力不断累加，进而使得材料发生结构相变和颗粒开裂等现象，会极大地破坏材料的可逆循环。在高电压体系中，富镍材料(如富镍三元材料)的脱 嵌锂程度会进一步加深。本申请中，正极活性材料可以采用传统的富镍三元正极材料。本申请中，还可以向三元正极活性材料中引入N元素的掺杂，可以降低材料的晶格变化程度，起到稳定晶格的作用，从而可以改善富镍三元材料的循环性能。此外，还有利于避免开裂产生的新界面加速与电解液之间的副反应，从而有利于改善电芯产气。
在一些实施方式中，A颗粒和B颗粒可采用本领域公知的用于电池的正极活性材料。可适用于本申请A颗粒和B颗粒的正极活性材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的非限制性示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的一种或多种。
在一些实施方式中，正极活性材料为任意合适的三元正极材料。非限制性示例包括NCM(镍钴锰三元材料)、NCA(镍钴铝三元材料)等。其中，NCM材料的非限制性示例如NCM 523、NCM 622、NCM 811等。NCA材料中的镍、钴、铝元素的摩尔比通常根据理论值80：15：5进行控制。
在本申请的一些实施方式中，所述A颗粒和所述B颗粒的真密度可以各自独立地大于4.0g/cc。
在一些实施例中，所述A颗粒和所述B颗粒的真密度各自独立地选自4.0g/cc～4.8g/cc。
在一些实施例中，所述A颗粒的真密度各自独立地选自4.6g/cc～4.8g/cc。
在一些实施例中，所述B颗粒的真密度各自独立地选自4.5g/cc～4.8g/cc。
在一些实施例中，所述A颗粒的真密度4.6g/cc～4.8g/cc，所述B颗粒的真密度选自4.6g/cc～4.8g/cc。
本申请所使用的“真密度”具有本领域公知的含义，指的是正极活性材料或正极活性颗粒的质量与其真体积的比值，其中真体积是固体物质的实际体积，不包括存在于颗内部的孔隙对应的体积。可以采用g/cc为单位，比如，以g为单位的质量与相应cm 3为单位的真体积的比值可以得到真密度数值。
在本申请中，真密度是决定正极材料压实密度的主要因素之一。通过合理控制A颗粒与B颗粒的真密度，有利于提高正极极片的体积比容量和能量密度，从而在改善高电压下材料开裂问题的同时，更好地改善电芯性能。对于本申请的级配方式的多颗粒体系，材料的颗粒搭配越紧密，正极材料理论可实现的体积比容量就越高。
在一些实施方式中，所述A颗粒和所述B颗粒各自独立地包括本体结构以及包覆在所述本体结构表面至少一部分的氧化物层；
其中，
在一些实施例中，所述本体结构包括化学式为Li k1-a1Q a1(Ni x1Co y1M 1-x1-y1) 1-z1N z1O2的材料，其中，0.9≤k1≤1.1(可选地，0.92≤k1≤1.08；可选地，0.95≤k1≤1.05；可选地，0.96≤k1≤1.04；可选地，0.98≤k1≤1.02；可选地，0.99≤k1≤1.01；可选地，k1等于1)，0≤a1≤0.20，0.40≤x1≤1.00(可选地，0.50≤x1≤1.00；可选地，0.60≤x1≤1.00；可选地，0.70≤x1≤1.00)，0≤y1≤0.15，0≤(1-x1-y1)，0≤z1≤0.5，且Q元素包括Na、K、Rb和Ca中的一种或多种，M元素包括Mn和Al中的一种或两种，N元素包括Al、Ti、Zr、Nb、Sr、Sb、Y、Ba、Co、Mn、Mg、Si、P、Mo、C和W中的一种或多种；
在其中的一些实施例中，0≤a1≤0.20，0.60≤x1<1.00，0<y1≤0.15，0<(1-x1-y1)，0≤z1≤0.5；
在其中的另一些实施例中，N元素包括Al、Ti、Zr、Nb、Sr、Sb、Y、Mg和W中的一种或多种；
在一些实施例中，所述氧化物层包括化学式为Li k2-a2Q’ a2(Ni x2Co y2M’ 1-x2-y2) 1-z2N’ z2O 2-c2X c2的材料，其中，.9≤k2≤1.1(可选地，0.92≤k2≤1.08；可选地，0.95≤k2≤1.05；可选地，0.96≤k2≤1.04；可选地，0.98≤k2≤1.02；可选地，0.99≤k2≤1.01；可选地，k2等于1)，0≤a2≤0.20，0.40≤x2≤1.00(可选地，0.50≤x2≤1.00；可选地，0.60≤x2≤1.00；可选地，0.70≤x2≤1.00)，0≤y2≤0.15，0≤(1-x2-y2)，0<z2≤0.5，0≤c2≤1，且Q’元素包括Na、K、Rb和Ca中的一种或多种，M’元素包括Mn和Al中的一种或两种，N’元素包括Al、Ti、Zr、Nb、Sr、Sb、Y、Ba、Co、Mn、Mg、W、Mo、Si、C和P中的一种或多种，X元素包括B、Cl、S和F中的一种或多种；
在其中的一些实施例中，0≤a2≤0.20，0.60≤x2<1.00，0<y2≤0.15，0<(1-x2-y2)，0<z2≤0.5，0≤c2≤1。
在一些实施例中，A颗粒和B颗粒均具有氧化物层(包覆层)，可参阅图1(b)。
在本申请中，A颗粒及B颗粒的化学式可通过电感耦合等离子体发射光谱法方法测得。
在本申请中，可以在正极活性材料的本体结构中掺杂Q’元素(如Na、K、Rb、Ca等)，从而提升锂离子扩散系数，降低锂镍混排。还可以在正极活性材料表面进行包覆，在颗粒表面形成掺杂特定N’元素的氧化物层，可降低材料的表面与电解液的反应活性，减少材料释氧，提高活性材料的结构稳定性，提高离子电导率，还可以提升材料容量。此外，通过将材料的颗粒尺寸设计与结构设计相结合，可以还使材料具有更高的比容量，并同时降低正极材料与电解液之间的副反应和相变的程度，使电池具有更低的瓦时成本和更高的循环寿命。相对于包覆层结构设计，无包覆层的材料界面有可能与电解液发生的大量副反应，导致电解液被氧化而生成二氧化碳和氧气等气体；而且，无包覆层时，正极活性材料表面层状结构更容易向岩盐结构转变，导致材料表 面失去化学反应活性。
通过控制氧化物层具有较合适的量，可以更好地改善材料的结构稳定性，更好地抑制表面副反应的加剧，更好地延长材料循环寿命。氧化物层的含量偏少时，前述效果不明显。氧化物层的含量偏多时，可能导致材料的容量下降。
在一些实施方式中，Q’ b2Ni x2Co y2M’ 1-x-y与Q b1Ni x1Co y1M 1-x1-y1相同，此时可采用相同的工艺制备，通过筛分而得到A颗粒及B颗粒。
在一些实施例中，N’元素包括Al、Ti、Zr、Sr、Sb、Mo、Nb、Mg、Y和W中的一种或多种。
在一些实施方式中，N’元素包括Al、Ti、Zr、Sr、Sb、W、C、P和Mo中的一种或多种。
在一些实施方式中，N’元素包括Al、Zr、Nb、Sr、Sb、Co、Mg、W和Mo中的至少一种。通过在氧化物层掺杂Zr、Al、Mg、W、Mo、Co、Sr、Sb、Nb等元素，其中，Mg、Ti、Al和Mo等元素可以降低材料在充放电循环过程中晶格变形量，从而提高材料的结构稳定性。
在一些实施方式中，X元素包括B、Cl、S和F中的至少一种。向氧化物层中掺杂B、Cl、S和F等元素，从而提升容量和倍率性能。
在本申请的一些实施方式中，所述氧化物层的厚度可以为0～100nm，进一步可以为1nm～100nm，还可以为1nm～20nm。所述氧化物层的厚度还可以选自如下任一种或任两种构成的区间：1nm、2nm、3nm、4nm、5nm、6nm、7nm、8nm、9nm、10nm、12nm、15nm、16nm、18nm、20nm、25nm、30nm、35nm、40nm、45nm、50nm、55nm、60nm、65nm、65nm、70nm、75nm、80nm、85nm、90nm、95nm、100nm等。
在本申请的一些实施方式中，所述氧化物层相对于所述本体结构的质量百分比可以为0.01％～5％，进一步可以为0.01％～4％，更进一步可以为0.05％～4％。所述氧化物层相对于所述本体结构的质量百分比还可以选自如下任一种百分比或者任两种百分比构成的区间：0.01％、0.02％、0.03％、0.04％、0.05％、0.06％、0.08％、0.9％、1％、1.2％、1.5％、1.6％、1.8％、2％、2.5％、3％、3.5％、4％、4.5％、5％等。
在本申请的一些实施方式中，所述氧化物层中的N元素在所述正极活性材料中的质量占比可以为0.01％-4％，进一步可以为0.05％-4％，更进一步可以为0.1％-4％。所述氧化物层中的N元素在所述正极活性材料中的质量占比还可以选自如下任一种百分比或者任两种百分比构成的区间：0.01％、0.02％、0.03％、0.04％、0.05％、0.06％、0.08％、0.9％、1％、1.2％、1.5％、1.6％、1.8％、2％、2.5％、3％、3.5％、4％等。
在本申请中，A颗粒及B颗粒中的包覆层厚度可通过透射电子显微镜方法测得。
在本申请中，A颗粒及B颗粒中的包覆层质量含量可通过电感耦合等离子体发射光谱法方法测得。
在本申请中，A颗粒及B颗粒中的N元素在本申请所述正极活性材料中的质量占比可通过电感耦合等离子体发射光谱法方法测得。
通过合理控制表面氧化物层的量，比如氧化物层的厚度、氧化物层所占质量百分 比、N元素掺杂量等参数，能够更好实现前述掺杂、包覆目的(通过掺杂，可使掺杂源均匀进入材料体相，降低收缩膨胀，提高结构稳定性；通过包覆，可降低到镍含量，钝化界面，降低与电解液的反应性)，更好地调节材料的化学反应活性和结构稳定性，更好地将材料的颗粒尺寸设计与结构设计相结合，还同时赋予材料更高比容量，降低正极材料与电解液之间的副反应和相变的程度，使电池具有更低的瓦时成本和更高的循环寿命。
在本申请的一些实施方式中，所述正极活性材料中的游离锂含量小于3000ppm，以质量比计。
在一些实施方式中，碳酸锂在本申请所述正极活性材料中的含量小于3500ppm，以质量比计。
在一些实施方式中，氢氧化锂在本申请所述正极活性材料中的含量小于3000ppm，以质量比计。进一步地，碳酸锂含量小于3500ppm，以质量比计。
在本申请中，A颗粒及B颗粒中的游离锂在本申请所述正极活性材料中的质量占比可通过游离锂电位滴定方法测得。
在本申请中，可通过合理控制正极活性材料中的游离锂(如碳酸锂、氢氧化锂等)含量，从而避免在高电压条件下的循环过程中过多产气。如果游离锂偏高，在高电压条件下的循环过程中会与电解液分解产生的氢氟酸发生酸碱中和反应，并产生大量气体，使得电芯胀气和鼓包影响电芯，容易发生电芯安全事故。
在本申请的一些实施方式中，所述正极活性材料的I003晶粒含量与I104晶粒含量之比I003/I104≥1.2，以XRD图谱中I003晶面与I104晶面的特征峰面积之比计；
可选地，I003/I104选自1.2～2；
可选地，I003/I104选自1.3～2；
可选地，I003/I104选自1.3～1.6。
在申请中，测试正极活性材料的晶粒尺寸，可采用X射线衍射(XRD)法。进一步地，采用如下的测试参数：采用平板制样法制样，测试角度15°～70°。
通过合理控制正极活性材料的I003晶粒含量与I104晶粒含量之比I003/I104(如≥1.2)，可以更好地控制锂镍混排的程度，避免过多镍元素占据锂元素晶格位置而导致可逆容量的降低和锂离子的扩散系数降低。如果锂离子和二价镍发生阳离子混排，此时二价镍进入锂离子中，会降低锂离子扩散系数，增加阻抗，导致容量下降，损害循环性能和存储性能。通常而言，混排程度越低，排列越规整，电芯性能越好。
在本申请的一些实施方式中，在所述B颗粒中，至少一部分的一次颗粒沿径向方向定向排列
对于本申请的二次球颗粒，通过控制反应体系的pH值，反应原料浓度，反应时间和反应温度等参数，可使一次颗粒沿径向方向产生一定的定向排列(如图6的B颗粒SEM测试截面形貌所示)，从而抑制高电压下可能产生的收缩膨胀，避免内部应力增大，从而更好地防止材料在高电压下破碎，此外还可改善循环性能。沿径向的定向排列程度越高，无定向的无规排列程度越低，效果改善程度越明显。
本申请第一方面提供的正极活性材料为高镍正极材料，具有特定结构的小颗粒和 大颗粒，且小颗粒的含量高于大颗粒，制备得到的正极极片具有较高的质量比容量和优异的结构稳定性，进一步地，在电芯层级中，可以明显提升电芯的质量能量密度和循环寿命，还能减少与电解液之间的副反应，降低电芯的产气。
第二方面，本申请提供一种正极极片，其包括正极集流体以及位于所述正极集流体至少一个表面上的正极活性材料层，所述正极活性材料层包含本申请第一方面所述的正极活性材料。
采用本申请第一方面的正极活性材料可制备高镍含量的正极极片，能够利用正极活性材料的颗粒尺寸及含量设计，避免材料在高电压下开裂，改善高电压条件下的电芯循环和存储性能，进一步还可利用掺杂和/或包覆结构设计调节材料的化学反应活性和结构稳定性，可以使材料具有更高的比容量，同时降低正极材料与电解液之间的副反应和相变的程度，使电池具有更低的瓦时成本和更高的循环寿命。
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层。可参阅图7和图8。图7中的正极活性材料包括A颗粒和B颗粒。图8中的正极活性材料包括A颗粒、B1颗粒和B2颗粒。
作为非限制性示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为非限制性示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的一种或多种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为非限制性示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的一种或多种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
在本申请的一些实施方式中，所述正极极片的压实密度为3.3g/cm 3～3.7g/cm 3，一些非限制性示例如3.3g/cm 3、3.4g/cm 3、3.5g/cm 3、3.6g/cm 3、3.7g/cm 3等。
本申请所使用的“压实密度”具有本领域公知的含义，指的是正极活性材料的质量与其体积的比值。
在本申请中，通过控制正极极片在较合适的压实密度，可以在赋予极片更好的比 容量及能量密度的情况下，更好地避免高电压条件材料开裂。应当理解，正极极片的压实密度还受到其中包含的A颗粒及B颗粒的真密度的限制。极片的压实密度的提升，可以提高材料的体积比容量，使得电芯在更小的体积具有更长的续航。
第三方面，本申请提供一种电化学储能装置，其包括本申请第二方面所述正极极片、负极极片以及隔离膜，其中，所述隔离膜设置于所述正极极片和所述负极极片之间。
第四方面，本申请提供一种二次电池，其包括本申请第二方面所述正极极片以及本申请第三方面所述电化学储能装置中至少一种。
第五方面，本申请提供一种用电装置，其包括本申请第二方面所述正极极片，本申请第三方面所述电化学储能装置以及本申请第四方面所述二次电池中至少一种。
采用本申请第一方面的正极活性材料制备高镍含量的正极极片，进而制备电化学储能装置、二次电池、用电装置，能够利用正极活性材料的颗粒尺寸及含量设计，避免材料在高电压下开裂，改善高电压条件下的电芯循环和存储性能，进一步还可利用掺杂和/或包覆结构设计调节材料的化学反应活性和结构稳定性，可以使材料具有更高的比容量，同时降低正极材料与电解液之间的副反应和相变的程度，使电池具有更低的瓦时成本和更高的循环寿命。
在本申请中，二次电池包括正极极片(本申请第二方面提供)、负极极片、电解质和隔离膜。在电池充放电过程中，锂离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使锂离子通过。
正极极片
本申请第三方面及第四方面中的正极极片可采用本申请第二方面提供的正极极片。
负极极片
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
作为非限制性示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为非限制性示例，负极活性材料可包括以下材料中的：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的。所述锡基材料可选自单质锡、锡氧化合物 以及锡合金中的。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
电解质
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有特别的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、高氯酸锂(LiClO 4)、六氟砷酸锂、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的。
在一些实施方式中，溶剂可选自碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的一种或多种。
在一些实施方式中，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
隔离膜
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
电极组件、电化学储能装置、二次电池、用电装置
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，电化学储能装置可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图9是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图10，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据实际需求进行选择。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池。所述二次电池可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备、电动车辆、电气列车、船舶及卫星、储能系统等，但不限于此。其中，移动设备例如可以是手机、笔记本电脑等；电动车辆例如可以是纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池。
图11是作为一个示例的用电装置6。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
本申请第六方面，一种正极活性材料的制备方法，其包括如下步骤：将所述A颗粒和所述B颗粒按照预设质量比进行混合，制备得到所述正极活性材料；所述A颗粒和B颗粒如本申请第一方面所定义；
其中，所述A颗粒可以采用包括如下步骤的方法制备得到：将氢氧化锂、镍钴M体前驱体材料Ni xCo yM 1-x-y(OH) 2以及可选的Q添加剂和可选的N添加剂混合，在氧气存在及温度T1条件下进行一次烧结；可选地，向一次烧结产物中加入X添加剂和N添加剂中至少一种，混合，在氧气存在下进行二次烧结；
其中，所述B颗粒可以采用包括如下步骤的方法制备得到：将氢氧化锂、镍钴M 体前驱体材料Ni xCo yM 1-x-y(OH) 2以及可选的Q添加剂和可选的N添加剂混合，在氧气存在及温度T2条件下进行一次烧结；可选的，向一次烧结产物中加入X添加剂和N添加剂中至少一种，混合，在氧气存在下进行二次烧结；
其中，所述Q添加剂、N添加剂、X添加剂分别为含有Q元素的添加剂、含有N元素的添加剂、含有X元素的添加剂；
进一步地，所述温度T1高于所述温度T2；
其中，x、y、M元素、Q元素和N元素如本申请第一方面所定义；。
在一些实施例中，制备所述A颗粒的步骤中，在氧气存在条件下烧结的步骤中，一次烧结温度(T1)为700℃～950℃，可选地750℃～900℃，二次烧结温度为300℃～600℃，可选地350℃～550℃。所述A颗粒的一次烧结温度T1还可以为如下任一种温度或任两种构成的区间：700℃、750℃、800℃、850℃、900℃、950℃等。二次烧结温度还可以为如下任一种温度或任两种构成的区间：350℃、400℃、450℃、500℃、550℃等。
在一些实施例中，制备所述B颗粒的步骤中，在氧气存在条件下烧结的步骤中，一次烧结温度为700℃～900℃，可选地750℃～850℃，二次烧结温度为300℃～600℃，可选地350℃～550℃。一次烧结温度还可以为如下任一种温度或任两种构成的区间：700℃、750℃、800℃、850℃、900℃等。二次烧结温度还可以为如下任一种温度或任两种构成的区间：350℃、400℃、450℃、500℃、550℃等。
本申请第一方面中提供的正极活性颗粒(A颗粒或B颗粒)无表面包覆层时，可以采用一次烧结方法，利用相应的前驱体在氧化氛围中制备得到。
本申请第一方面中提供的正极活性颗粒(A颗粒或B颗粒)表面包覆有氧化物层时，可以采用分步烧结方法，先将本体结构的前驱体在氧化氛围、较高温度条件下烧结(如A颗粒在700℃～950℃，又如B颗粒在700℃～900℃)形成本体结构，然后与包覆层前驱体混合在在氧化氛围中、较低温度条件下进行烧结(如300℃～600℃)形成氧化物层，从而制备得到带有包覆层的A颗粒或B颗粒。一次烧结时，在较高烧结温度条件下，颗粒内部粒子容易连结。因此，可以在相对较高的一次烧结温度(T1)下，使粒子充分连结从而制备得到大尺寸的单晶或类单晶颗粒(A颗粒)，可以在相对较低的一次烧结温度(T2)下制备得到小尺寸的二次颗粒(B颗粒)，此时，二次颗粒中的细小粒子未连结或仅部分连结。
第七方面，本申请提供一种正极浆料的制备方法，其包括如下步骤：将A颗粒、B颗粒和可选的助剂混合，制备得到所述正极浆料；其中，所述A颗粒和所述B颗粒如本申请第一方面所定义；
在本申请的一些实施方式中，所述的制备方法满足如下一种或多种特征：
(1)所述正极浆料的pH为11～12；
(2)将A颗粒、B颗粒和可选的助剂混合的步骤于室温(如25℃)条件下进行；和
(3)将A颗粒、B颗粒和可选的助剂混合的步骤于搅拌条件下进行，搅拌速度为500～2000r/min，搅拌时间为0.5h～5h。
通过协同控制正极浆料的制备参数，如pH、混合温度、搅拌速度、搅拌时间等，可以更好地控制正极浆料的黏度，改善加工性能。
以下，说明本申请的一些实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明技术或条件的详细细节的，按照上文中的描述进行，或者按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品，或者可通过市购产品按照常规方式合成。
下面的实施例中，室温是指20℃～30℃，进一步地，可以为25℃。
以下各例中，如无特别说明，将正极浆料涂覆在正极集流体时采用单侧涂覆的方式，将负极浆料涂覆在负极集流体时采用双侧涂覆的方式。进一步地，如无特别说明，各例的正极极片采用基本相同的单侧涂覆量，各例的负极极片采用基本相同的单侧涂覆量，浆料的涂覆量可以采用单位面积的涂覆质量进行调控。应当理解，各例中单侧、双侧涂覆的方式用于进行示例性阐述，制备本申请中的极片时，正极极片和负极极片的制备各自独立地可以采用单侧涂覆或双侧涂覆的方式。
以下各例中，涉及制备方法的“基本相同”表示除特别指明的参数进行改变外，其余参数保持不变，但可以理解的是，可接受基于指明改变的参数进行适应性调整。比如，目标产物的成分改变及含量改变时，允许适应性调节原料的成分及用量。
实施例1.
1.1.正极活性材料的制备(本体结构存在掺杂元素，无包覆层)
前驱体的粒度决定了对正极材料的颗粒大小，可通过调控前驱体的尺寸和分布实现对A颗粒和B颗粒的尺寸及分布控制。对本领域技术人员来说，调控前驱体的尺寸及分布的手段是已知的。
将三元前驱体(Ni 0.8Co 0.1Mn 0.1)OH 2(颗粒尺寸D v50约为4μm)、LiOH·H 2O、ZrO 2和Al 2O 3以摩尔比0.95：1.04：0.03：0.01在混料机中混合，然后在氧气氛中860℃烧结，获得A颗粒。
将三元前驱体(Ni 0.8Co 0.1Mn 0.1)OH 2(颗粒尺寸D v50约为10μm)、LiOH·H 2O、ZrO 2和Al 2O 3以摩尔比0.95：1.04：0.03：0.01在混料机中混合，然后在氧气氛中830℃烧结，得到B颗粒。将依次制备得到的A颗粒与B颗粒按照一定质量比(可参阅表1和表2)混合，制备得到正极活性材料，待用。
1.2.正极极片的制备
将正极活性材料、聚偏二氟乙烯和导电炭黑以质量比90：5：5进行混合，然后加入N-甲基吡咯烷酮(NMP)，搅拌2h，然后将其在匀浆机中搅拌以1000r/min搅拌直至混合均匀，然后均匀涂覆在13微米厚的铝箔集流体的单侧表面上，涂覆完成后，将其在100℃的干燥箱中烘干，冷压，分切得到正极极片。
1.3.电解液的制备
将碳酸乙烯酯(EC)和碳酸二乙酯(DEC)的混合液以体积比1：2混合，得到混合溶剂。然后在氩气气氛手套箱中，将充分干燥的六氟磷酸锂溶解在混合溶剂中，混合均匀获得电解液。电解液中锂盐浓度为1mol/L。
1.4.负极极片的制备
将负极活性材料石墨，羧甲基纤维素钠、丁苯橡胶和乙炔黑按照质量比96：1：1：2的比例混合，加入去离子水，在搅拌机中搅拌均匀，然后将浆料涂覆在8微米厚的铜箔的双侧表面上，在100℃烘箱中干燥，冷压，分切得到负极极片。
1.5.制备电芯
从上到下依次正极极片、隔离膜、负极极片叠好，确保正负极极片不能相互接触，然后将其通过卷针卷绕成裸电芯后，装入方形铝壳中，注入电解液，进行静置、化成、容量等步骤，制备出电芯。
实施例2.
实施例2采用与实施例1基本相同的方法，区别在于正极活性材料的制备步骤不同，正极活性材料的添加剂不同。
2.1.正极活性材料的制备
将三元前驱体(Ni 0.8Co 0.1Mn 0.1)OH 2(颗粒尺寸D v50约为4μm)、LiOH·H 2O、ZrO 2、Al 2O 3和B 2O 3以摩尔比0.95：1.04：0.03：0.01：0.01在混料机中混合，然后在氧气氛中860℃烧结，获得A颗粒。
将三元前驱体(Ni 0.8Co 0.1Mn 0.1)OH 2(颗粒尺寸D v50约为10μm)、LiOH·H 2O、ZrO 2、Al 2O 3和B 2O 3以摩尔比0.95：1.04：0.03：0.01：0.01在混料机中混合，然后在氧气氛中820℃烧结，得到B颗粒。
将制备得到的A颗粒与B颗粒按照一定质量比(可参阅表1和表2)混合，制备得到正极活性材料，待用。
实施例3.
实施例3采用与实施例1基本相同的方法，区别在于正极活性材料的制备步骤不同，正极活性材料的添加剂不同。
3.1.正极活性材料的制备
将三元前驱体(Ni 0.8Co 0.1Mn 0.1)OH 2(颗粒尺寸Dv50约为4μm)、LiOH·H 2O、ZrO 2、Sb 2O 5和Al 2O 3以摩尔比0.94：1.04：0.02：0.01：0.01在混料机中混合，然后在氧气氛中860℃烧结，获得A颗粒。
将三元前驱体(Ni 0.8Co 0.1Mn 0.1)OH 2(颗粒尺寸D v50约为10μm)、LiOH·H 2O、ZrO 2、Sb 2O 5和Al 2O 3以摩尔比0.94：1.04：0.02：0.01：0.01在混料机中混合，然后在氧气氛中820℃烧结，得到B颗粒。
将制备得到的A颗粒与B颗粒按照一定质量比(可参阅表1和表2)混合，制备得到正极活性材料，待用。
实施例1a至实施例1d.采用三元正极材料
实施例1a、实施例1b、实施例1c和实施例1d均采用与实施例1基本相同的方法，区别在于正极活性材料的组成成分不同，A颗粒和B颗粒均采用自制的NCM三元正极材料。
实施例1a、实施例1b、实施例1c和实施例1d采用不同的镍含量(参考表1)，采用不同镍含量的三元前驱体，其余制备参数相同。
实施例1a.
将三元前驱体(Ni 0.8Co 0.1Mn 0.1)OH 2(颗粒尺寸D v50约为4μm)和LiOH·H 2O以摩尔比1：1.04在混料机中混合，然后在氧气氛中860℃烧结，获得A颗粒。
将三元前驱体(Ni 0.8Co 0.1Mn 0.1)OH 2(颗粒尺寸D v50约为10μm)和LiOH·H 2O以摩尔比1：1.04在混料机中混合，然后在氧气氛中820℃烧结，获得B颗粒。
将制备得到的A颗粒与B颗粒按照一定质量比(参考表1和表2)混合，制备得到正极活性材料(实施例4-1)，待用。实施例1b、实施例1c和实施例1d中的A颗粒和B颗粒的各D v10、D v50、D v90及Span值分别与实施例1a类似。
对比例1.采用实施例1基本相同的方法，区别在于，以等质量的A颗粒代替B颗粒制备正极极片。
对比例2.采用实施例1基本相同的方法，区别在于，以等质量的B颗粒代替A颗粒制备正极极片。
对比例3.采用实施例1基本相同的方法，区别在于，A颗粒的质量含量少于B颗粒，进一步地，A颗粒在正极活性材料中质量含量为20％。
对比例4a.采用实施例1a基本相同的方法，区别在于，以等质量的A颗粒(NCM811)代替B颗粒制备正极极片。
对比例4b.采用实施例1a基本相同的方法，区别在于，以等质量的B颗粒(NCM811)代替A颗粒制备正极极片。
表1.
Figure PCTCN2022122177-appb-000001
表2.
Figure PCTCN2022122177-appb-000002
实施例4-6.采用与实施例1基本相同的方法，区别在于，正极活性颗粒包括B1颗粒和B2颗粒，调节A、B1、B2颗粒的D v50、Span及含量。
对比例5.采用与实施例4基本相同的方法，区别在于，调节B1颗粒含量。
对比例6.采用与实施例6基本相同的方法，区别在于，调节B1、B2颗粒的D v50。
对比例7-8.采用与实施例6基本相同的方法，区别在于，调节B1、B2颗粒的D v50、Span的组合。
实施例4-6和对比例5-8的相关参数可参阅表3。
表3.
Figure PCTCN2022122177-appb-000003
Figure PCTCN2022122177-appb-000004
实施例7.
正极极片的制备：将A颗粒、B1’颗粒、B2’颗粒和B3’颗粒以5：2：2：1的质量比例混合均匀，制备正极活性材料，然后将活性材料与聚偏二氟乙烯：导电炭黑以90：5：5的质量比例制备混合，涂敷，冷压，模切制备正极极片。A颗粒、B1’颗粒、B2’颗粒和B3’颗粒的化学组成均为Li(Ni 0.8Co 0.1Mn 0.1) 0.95Zr 0.03Al 0.02O 2。
其余制备参数及方法与实施例1一致。
从上到下依次正极极片、隔离膜、负极极片叠好，确保正负极极片不能相互接触，然后将其通过卷针卷绕成裸电芯后，装入方形铝壳中，注入电解液，静置、化成、容量等制备出电芯。
进一步地，实施例7a至实施例7m在前述制备方法基础上，将A颗粒、B1’颗粒、B2’颗粒和B3’颗粒的质量比例从5：2：2：1调节为表5所示的不同用量比，其余制备步骤与质量比例5：2：2：1时相同。
实施例8.
正极极片的制备：将A颗粒、B1’颗粒、B2’颗粒和B3’颗粒以6：4：0.5：0.5的质量比例混合均匀，制备正极活性材料，然后将活性材料与与聚偏二氟乙烯：导电炭黑以质量比90：5：5的比例制备混合，涂敷，冷压，模切制备正极极片。A颗粒、B1’颗粒、B2’颗粒和B3’颗粒的化学组成均为Li(Ni 0.8Co 0.1Mn 0.1) 0.95Zr 0.03Al 0.02O 2。
其余制备参数及方法与实施例1一致。
从上到下依次正极极片、隔离膜、负极极片叠好，确保正负极极片不能相互接触，然后将其通过卷针卷绕成裸电芯后，装入方形铝壳中，注入电解液，静置、化成、容量等制备出电芯。
此外，发明人采用实施例8的A颗粒、B1’颗粒、B2’颗粒和B3’颗粒，采用与实施例8基本相同的方法，仅调整各颗粒的含量(如表9所示的实施例8a至实施例8m)，得到了不同的正极极片，进而制备二次电池。
实施例9.
正极极片的制备：将A颗粒、B1’颗粒、B2’颗粒和B3’颗粒以7：1：1：1的质量比例混合制备正极活性材料，然后将活性材料与与聚偏二氟乙烯：导电炭黑以质量比90：5：5的比例制备混合，涂敷，冷压，模切制备正极极片。A颗粒、B1’颗粒、B2’颗粒和B3’颗粒的化学组成均为Li(Ni 0.8Co 0.1Mn 0.1) 0.95Zr 0.03Al 0.02O 2。
其余制备参数及方法与实施例1一致。
从上到下依次正极极片、隔离膜、负极极片叠好，确保正负极极片不能相互接触，然后将其通过卷针卷绕成裸电芯后，装入方形铝壳中，注入电解液，静置、化成、容量等制备出电芯。
实施例7-9的相关参数可参阅表4和表5。
表4.
Figure PCTCN2022122177-appb-000005
表5.
Figure PCTCN2022122177-appb-000006
实施例10-13和实施例11b、12b、13b的正极活性颗粒本体结构的化学组成均为Li(Ni 0.8Co 0.1Mn 0.1) 0.95Zr 0.03Al 0.02O 2。
实施例10-12.采用与实施例1基本相同的方法，区别在于：活性颗粒带有包覆层，并改变厚度、质量比、N元素含量，可参阅表6和表7。
其中A颗粒和B颗粒的制备方法分别如下：
A颗粒采用包括如下步骤的方法制备得到：将氢氧化锂、镍钴M体前驱体材料Ni xCo yM 1-x-y(OH) 2(D v50约为4μm)以及ZrO 2和Al 2O 3混合，在氧气存在条件下进行一次烧结，烧结温度在850℃；向一次烧结产物中加入N”元素的添加剂(参考表6)，在氧气存在下进行二次烧结，烧结温度在350℃；
其中，所述B颗粒采用包括如下步骤的方法制备得到：将氢氧化锂、镍钴M体前驱体材料Ni xCo yM 1-x-y(OH) 2(D v50约为4μm)以及ZrO 2和Al 2O 3混合，在氧气存在条件下进行一次烧结，烧结温度在820℃；可选的，向一次烧结产物中加入N”元素的添加剂(参考表6)，在氧气存在下进行二次烧结，烧结温度在350℃。
其中，M为锰，x为0.8，y为0.1，(1-x-y)为0.1。A颗粒和B颗粒的本体结构中的N元素均包括Zr和Al，A颗粒和B颗粒的包覆层中的N’元素包括Zr、Al和N”元素(参见表6)，A颗粒和B颗粒中的N”元素相同。当N”元素与N元素相同时，导致含量的改变。
其中，N”元素指相对于本体结构还包含的其他的掺杂元素。关于N”元素的添加剂，当N”元素为Al、Mg、B时，二次烧结时使用的相应添加剂分别为Al 2O 3、MgO、B 2O 3。
对比例9.采用与实施例11基本相同的方法，区别在于：包覆层厚度不同。
实施例12b.采用与实施例12基本相同的方法，区别在于：烧结温度不同。
实施例13.采用与实施例10基本相同的方法，区别在于：烧结温度不同。
表6.
Figure PCTCN2022122177-appb-000007
表6中的“掺杂元素”包括本体结构和氧化层中的所有掺杂元素，包括本体结构中的N元素和氧化层中的N’元素。
实施例14-16采用与实施例5基本相同的方法，区别之处在于：正极活性材料的材料成分不同。
实施例14-16中，A颗粒+B1颗粒+B2颗粒的组合方式，粒径参数(D v10、D v50、D v90和Span控制与实施例5类似)。A颗粒+B1颗粒+B2颗粒的掺杂元素的种类均相同。
实施例14的本体结构LiNi 0.8Co 0.1Mn 0.1O 2，其体相掺杂含有Zr和Sr元素，包覆层中含有Al和Mg元素。
实施例15的本体结构LiNi 0.8Co 0.1Mn 0.1O 2，其体相掺杂含有Zr、Sr和Ti元素，包覆层中含有Mg元素。
实施例16的本体结构LiNi 0.8Co 0.1Mn 0.1O 2，其体相掺杂含有Zr，Sr和W元素，包覆层中含有B元素。
表7.
编号 掺杂+包覆元素
实施例14 Zr/Sr+Al/Mg
实施例15 Zr/Sr/Ti+Mg
实施例16 Zr/Sr/W+B
实施例17.
采用与实施例1相同的活性材料成分，制备方法基本相同，区别在于：前驱体的一次颗粒无规则排布，使得B颗粒的一次颗粒基本无规分布。
测试例
1.A颗粒和B颗粒的成分测试
采用电感耦合等离子体发射光谱法。
2.粒径尺寸测试
(1)粒径测试
粒径尺寸类型：D v10、D v50和D v90测试。
设备型号：马尔文2000(MasterSizer 2000)激光粒度仪，参考标准流程：GB/T19077-2016/ISO 13320:2009，详细测试流程：取待测样品适量(样品浓度保证8％～12％遮光度即可)，加入20mL无水乙醇，超声处理5min(53KHz/120W)，确保样品完全分散，之后按照GB/T19077-2016/ISO 13320:2009标准对样品进行测定。为了避免干燥过程的团聚影响粒度的测试，取洗涤后湿润样品进行分散测试。
(2)正极活性材料的比表面积测试
采用氮气吸附比表面积分析测试方法测试，并用BET(Brunauer EmmettTeller)法计算得出，其中氮气吸附比表面积分析测试可以通过美国Micromeritics公司的Tri StarII型比表面与孔隙分析仪进行，测试步骤可以参照GB/T 19587-2004。
待测样品：各例制备的正极活性材料。
详细步骤如下：将待测样品在真空干燥箱200℃下干燥2小时；然后采用氩气作为吸附气体，通过比表面与孔隙分析仪测绘相对压力P/P 0为0～0.99的吸脱附曲线，P为平衡吸附压力，P 0为饱和蒸汽压，通过BET方法计算出正极活性材料的比表面积。
(3)真密度
采用真密度测试仪进行测试，测试步骤参照GB/T 24586-2009
待测样品：活性正极材料
步骤：前处理：取洁净干燥的样品杯放置在天平，清零，将粉末样品加入到样品杯中，约占样品杯体积的1/2，记录样品质量
将装有样品的样品杯，置于真密度测试仪，密闭测试系统，按程序通入氦气，通过检测样品室和膨胀室中的气体的压力，再根据玻尔定律(PV＝nRT)来计算真实体积，从而计算真密度
样品杯体积：3.5cm 3；分析气体：氦气。
(4)氧化物层的厚度(根据TEM)
采用TEM对材料进行分析，多点量取材料包覆层厚度取平均值。
(5)氧化物层含量
根据第一次烧结、第二次烧结的投料比换算得到。
(6)I003/I104测试
采用X射线衍射仪对正极活性材料进行分析，依据JIS K 0131-1996。
(7)游离锂(包括碳酸锂和氢氧化锂)含量测试
采用游离锂电位滴定仪对正极活性材料进行分析，依据GB/T 9725-2007。
3.极片
(1)压实密度
通过将正极浆料涂覆13μm的铝箔单侧表面上，单侧涂覆厚度为110μm，干燥后通过冷压机收集压实密度和延展率数据，在0.8％延展率下所对应的压实密度作为正极活性材料的极片压实密度的测试值。
延展率：(冷压后极片的长度-冷压前极片的长度)/冷压前极片的长度×100％
4.电芯
(1)比容量(mAh/g)
克容量是指电池内部活性物质所能释放出的电容量与活性物质的质量之比。
(2)循环性能：容量保持率
在25℃条件下，以1C倍率电流先恒流再恒压充放电一次为一次循环，第一次记为C 0，第n次为Cn，每次循环的容量保持率为Cn/C 0。
(3)产气测试(40天70℃存储产气)
在25℃条件下，先以1/3C恒定电流将锂离子电池充电至4.3V，然后恒压充电，电流为0.025C，充电至4.3V。用排水法将锂离子电池在去离子水中测量锂离子电池的体积为V0，然后再在70℃条件下存储每隔六天获取一次电芯体积变化，第n次为Vn。锂离子电池70℃存储后的体积膨胀率(％)＝(Vn-V 0)/V 0×100％。
(4)存储性能(60℃放置50天容量保持率)
在25℃，将电芯以1C电流恒流充电至4.3V，然后恒压充电，电流为0.05C，充电至4.3V，然后在1C电流恒流放电至2.8V，恒压放电，电流为0.05C，测得容量记为C0。
将电芯以1C电流充电至4.3V，恒压充电，电流为0.05C。把满充电芯置于60℃恒温炉中存放，每隔30天，取出电芯，在25℃，1C恒流放电至2.8V，然后恒压放电电流0.05C，测得容量为Cn，容量保持率＝Cn/C0。
重复第二步得到电池容量保持率随时间变化图。
(5)循环圈数(25℃循环至容量保持率80％的循环圈数)
在25℃下，将锂离子电池以1C恒流充电至电压为4.3V，然后以4.3V恒压充电，电流为0.05C，接着以1C恒流放电，直到最终电压为2.8V，容量为C1。依次重复上述步骤，第n次测得容量为Cn，容量保持率(％)＝(第n次放电容量/首次循环放电容量)×100％，一直进行循环直到电芯容量保持率衰减至80％为止。
表8.
Figure PCTCN2022122177-appb-000008
Figure PCTCN2022122177-appb-000009
图2至图6为实施例1的正极活性颗粒测试结果。
实施例与对比例的比较分析结果可参考下文。
实施例1中，B颗粒中的一次颗粒沿径向定向分布，在25℃循环至容量保持率80％的循环圈数为2600圈，日历寿命40天70℃产气6ml/ah。发明人推测是由于在充放电循环过程中，一次颗粒沿径向定向分布时，材料内部不容易产生应力集中。
实施例17中，B颗粒的一次颗粒基本无规分布，在25℃循环至容量保持率80％ 的循环圈数为1200圈，日历寿命40天70℃产气36ml/ah。
对比例1中仅包括A颗粒不包括B颗粒，对比例2中仅包括B颗粒不包括A颗粒，结果发现，相对于实施例1，对比例1和对比例2的循环性能、存储性能均明显下降，40天70℃存储产气均明显增大。对比例4a和对比例4b相对于实施例1a的效果对比结果类似。
对比例3中，B颗粒的含量大于A颗粒含量，相对于实施例1，对比例3的循环性能、存储性能都显著下降，40天70℃存储产气显著增大。
对比例5中，B1颗粒含量较高，相对于实施例4，对比例5的循环性能、存储性能都显著下降，40天70℃存储产气显著增大。
对比例6中，B1颗粒含量较高，相对于实施例6，对比例6的循环性能、存储性能都显著下降，40天70℃存储产气显著增大。
对比例7中，B2颗粒含量较高，相对于实施例6，B1颗粒的D v50偏高，导致循环性能、存储性能下降，高温产气量增大。
对比例8中，B1和B2颗粒含量大于A颗粒，相对于实施例6，对比例8的导致循环性能、存储性能下降，高温产气量增大。
对比例9中，包覆层厚度偏厚，相对于实施例11，对比例9的循环性能、存储性能下降，高温产气量增大。
实施例12b和实施例13调整了烧结工艺，实施例12b相对于实施例12的循环性能、存储性能下降，高温产气量增大，和实施例13相对于实施例10的循环性能、存储性能下降，高温产气量增大。
表9.
Figure PCTCN2022122177-appb-000010
表9中，实施例8a至实施例8m调整A颗粒、B1’颗粒、B2’颗粒和B3’颗粒的相对含量，均能实现较优的循环性能，存储产气量较低。
以上所述实施例的各技术特征可以进行任意的组合，为使描述简洁，未对上述实 施例中的各个技术特征所有可能的组合都进行描述，然而，只要这些技术特征的组合不存在矛盾，都应当认为是本说明书记载的范围。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。以上所述实施例仅表达了本申请的几种实施方式，其描述较为详细，但并不能因此而理解为对专利范围的限制。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。应当指出的是，对于本领域的普通技术人员来说，在不脱离本申请构思的前提下，还可以做出若干变形和改进，这些都属于本申请的保护范围。因此，本申请的保护范围应以所附权利要求为准，说明书及附图可用于解释权利要求的内容。

Claims (21)

  1. 一种正极活性材料，其包括A颗粒和B颗粒，所述A颗粒和所述B颗粒中的镍元素相对于锂元素的摩尔比R Ni/Li各自独立地大于等于0.33；
    其中，所述A颗粒具有单晶或类单晶的结构，所述B颗粒为包括多个一次颗粒的二次颗粒，其中，所述A颗粒的D v50小于所述B颗粒的D v50，所述A颗粒的质量占比大于等于所述B颗粒的质量占比；
    其中，D vN表示材料的累计体积分布百分数达到N％时对应的粒径，N为选自0～100的数值。
  2. 根据权利要求1所述的正极活性材料，其中，所述A颗粒的粒径满足2μm≤D v50≤5μm，所述B颗粒的粒径满足5μm<D v50≤25μm；
    可选地，所述A颗粒的Span值大于所述B颗粒的Span值；其中，Span＝(D v90-D v10)/D v50；其中，Span＝(D v90-D v10)/D v50；
    可选地，所述A颗粒的Span值选自0.1～3.0；所述B颗粒的Span值选自0.1～3.0；
    可选地，所述B颗粒的粒径满足8μm<D v50≤20μm。
  3. 根据权利要求1或2所述的正极活性材料，其中，所述B颗粒包括B1颗粒和B2颗粒，其中，所述B1颗粒的粒径满足5μm<D v50≤10μm，所述B2颗粒的粒径满足10μm<D v50≤25μm；
    可选地，所述B1颗粒在所述B颗粒中的重量占比选自50％～100％；
    可选地，所述B2颗粒在所述B颗粒中的重量占比选自0％～50％；
    可选地，所述A颗粒的Span值选自0.1～2.0；所述B1颗粒的Span值选自0.1～2.0；所述B2颗粒的Span值选自0.1～2.0；其中，Span＝(D v90-D v10)/D v50。
  4. 根据权利要求1或2所述的正极活性材料，其中，所述B颗粒包括B1’颗粒和B2’颗粒和B3’颗粒，其中，所述B1’颗粒的粒径满足8μm<D v50≤12μm，所述B2’颗粒的粒径满足12μm<D v50≤15μm，所述B3’颗粒的粒径满足15μm<D v50≤20μm；
    可选地，所述B1’颗粒在所述B颗粒中的重量占比选自40％～80％；
    可选地，所述B2’颗粒在所述B颗粒中的重量占比选自20％～30％；
    可选地，所述B3’颗粒在所述B颗粒中的重量占比选自0％～30％；
    可选地，所述A颗粒的Span值选自1.0～2.0，所述B1’颗粒的Span值选自0.1～2.0，所述B2’颗粒的Span值选自0.1～2.0，所述B3’颗粒的Span值选自0.1～2.0；其中，Span＝(D v90-D v10)/D v50。
  5. 根据权利要求1～4中任一项所述的正极活性材料，其中，所述A颗粒和所述B颗粒各自独立地包含如下的元素组合Ni xCo yM 1-x-y，其中，x≥0.4，y≥0，(1-x-y)≥0；M元素包括Mn和Al中的一种或两种；
    可选地，0.40≤x≤1.00，0≤y≤0.15，(1-x-y)≥0；
    可选地，0.50≤x≤1.00；可选地，0.60≤x≤1.00；
    可选地，y>0；可选地，0<y≤0.15；
    可选地，(1-x-y)>0；
    可选地，y>0，且(1-x-y)>0；
    可选地，所述A颗粒和所述B颗粒各自独立地包括化学式为Li k-aQ a(Ni xCo yM 1-x-y) 1-zN zO 2-cX c的材料，其中，0.9≤k≤1.1，0≤a≤0.2，0.40≤x≤1.00，0≤y≤0.15，0≤(1-x-y)，0≤z≤0.5，0≤c≤1，M元素包括Mn和Al中的一种或两种，Q元素包括Na、K、Rb和Ca中的一种或多种，N元素包括Al、Ti、Zr、Nb、Sr、Sb、Y、Ba、Co、Mn、Mg、W、Si、Mo、P和C中的一种或多种，X元素包括B、F、S和Cl中的一种或多种；
    可选地，0.92≤k≤1.08；可选地，0.95≤k≤1.05；可选地，0.96≤k≤1.04；可选地，0.98≤k≤1.02；可选地，0.99≤k≤1.01；可选地，k＝1；
    可选地，0.50≤x≤1.00；可选地，0.60≤x≤1.00；可选地，0.70≤x1≤1.00；
    可选地，其中，0≤a≤0.2，0.60≤x<1.00，0<y≤0.15，0<(1-x-y)，0≤z≤0.5，0≤c≤1。
  6. 根据权利要求1～5中任一项所述的正极活性材料，其中，所述A颗粒和所述B颗粒中的镍锂摩尔比R Ni/Li各自独立地≥0.4；
    可选地，所述A颗粒和所述B颗粒中的镍锂摩尔比R Ni/Li各自独立地≥0.5；
    可选地，所述A颗粒和所述B颗粒中的镍锂摩尔比R Ni/Li各自独立地≥0.6；
    可选地，所述A颗粒和所述B颗粒中的镍锂摩尔比R Ni/Li各自独立地≥0.7；
    可选地，所述A颗粒和所述B颗粒中的镍锂摩尔比R Ni/Li各自独立地≥0.8；
    可选地，所述A颗粒中的镍锂摩尔比R Ni/Li选自0.7～1.0；
    可选地，所述B颗粒中的镍锂摩尔比R Ni/Li选自0.8～1.0；
    可选地，所述B颗粒中的镍锂摩尔比R Ni/Li选自0.8～0.96。
  7. 根据权利要求1～6中任一项所述的正极活性材料，其中，所述A颗粒和所述B颗粒的真密度各自独立地大于4.0 g/cc；
    可选地，所述A颗粒和所述B颗粒的真密度各自独立地选自4.0 g/cc～4.8 g/cc；
    可选地，所述A颗粒的真密度各自独立地选自4.6 g/cc～4.8 g/cc；
    可选地，所述B颗粒的真密度各自独立地选自4.5 g/cc～4.8 g/cc。
  8. 根据权利要求1～6中任一项所述的正极活性材料，其中，所述A颗粒和所述B颗粒各自独立地包括本体结构以及包覆在所述本体结构表面至少一部分的氧化物层；
    其中，
    所述本体结构包括化学式为Li k1-a1Q a1(Ni x1Co y1M 1-x1-y1) 1-z1N z1O 2的材料，其中，0.9≤k1≤1.1，0≤a1≤0.20，0.40≤x1≤1.00，0≤y1≤0.15，0≤(1-x1-y1)，0≤z1≤0.5，且Q元素包括Na、K、Rb和Ca中的一种或多种，M元素包括Mn和Al中的一种或两种，N元素包括Al、Ti、Zr、Nb、Sr、Sb、Y、Ba、Co、Mn、Mg、Si、P、Mo、C和W中的一种或多种；
    可选地，0.92≤k1≤1.08；可选地，0.95≤k1≤1.05；可选地，0.96≤k1≤1.04；可选地，0.98≤k1≤1.02；可选地，0.99≤k1≤1.01；可选地，k1等于1；
    可选地，0.50≤x1≤1.00；可选地，0.60≤x1≤1.00；可选地，0.70≤x1≤1.00；
    可选地，N元素包括Al、Ti、Zr、Nb、Sr、Sb、Y、Mg和W中的一种或多种；
    可选地，0≤a1≤0.20，0.60≤x1<1.00，0<y1≤0.15，0<(1-x1-y1)，0≤z1≤0.5；
    所述氧化物层包括化学式为Li k2-a2Q’ a2(Ni x2Co y2M’ 1-x2-y2) 1-z2N’ z2O 2-c2X c2的材料，其中，0.9≤k2≤1.1，0≤a2≤0.20，0.40≤x2≤1.00，0≤y2≤0.15，0≤(1-x2-y2)，0<z2≤0.5，0≤c2≤1，且Q’元素包括Na、K、Rb和Ca中的一种或多种，M’元素包括Mn和Al中的一种或两种，N’元素包括Al、Ti、Zr、Nb、Sr、Sb、Y、Ba、Co、Mn、Mg、W、Mo、Si、C和P中的一种或多种，X元素包括B、Cl、S和F中的一种或多种；
    可选地，0.92≤k2≤1.08；可选地，0.95≤k2≤1.05；可选地，0.96≤k2≤1.04；可选地，0.98≤k2≤1.02；可选地，0.99≤k2≤1.01；可选地，k2等于1；
    可选地，0.50≤x2≤1.00；可选地，0.60≤x2≤1.00；可选地，0.70≤x2≤1.00；
    可选地，Q’ a2Ni x2Co y2M’ 1-x-y与Q a1Ni x1Co y1M 1-x1-y1相同；
    可选地，N’元素包括Al、Ti、Zr、Sr、Sb、Mo、Nb、Mg、Y和W中的一种或多种；
    可选地，0≤a2≤0.20，0.60≤x2<1.00，0<y2≤0.15，0<(1-x2-y2)，0<z2≤0.5，0≤c2≤1。
  9. 根据权利要求8所述的正极活性材料，其中，所述氧化物层的厚度为0～100nm；
    可选地，所述氧化物层的厚度为1 nm～100 nm；
    可选地，所述氧化物层的厚度为1 nm～20 nm。
  10. 根据权利要求8或9中任一项所述的正极活性材料，其中，所述氧化物层相对于所述本体结构的质量百分比为0.01％～5％；
    可选地，所述氧化物层相对于所述本体结构的质量百分比为0.05％～4％。
  11. 根据权利要求8～10中任一项所述的正极活性材料，其中，所述氧化物层中的N元素在所述正极活性材料中的质量占比为0.01％～4％；
    可选地，所述氧化物层中的N元素在所述正极活性材料中的质量占比为0.05％～4％。
  12. 根据权利要求1～11中任一项所述的正极活性材料，其中，所述正极活性材料的比表面积平均值为0.3 cm 2/g～1.5 cm 2/g。
  13. 根据权利要求1～12中任一项所述的正极活性材料，其中，所述正极活性材料中的游离锂含量小于3000 ppm，以质量比计。
  14. 根据权利要求1～13中任一项所述的正极活性材料，其中，所述正极活性材料的I003晶粒含量与I104晶粒含量之比I003/I104≥1.2，以XRD图谱中I003晶面与I104晶面的特征峰面积之比计；
    可选地，I003/I104选自1.2～2；
    可选地，I003/I104选自1.3～2；
    可选地，I003/I104选自1.3～1.6。
  15. 根据权利要求1～14中任一项所述的正极活性材料，其中，在所述B颗粒中，至少一部分的一次颗粒沿径向方向定向排列。
  16. 一种正极极片，其包括正极集流体以及位于所述正极集流体至少一个表面上的正极活性材料层，所述正极活性材料层包含权利要求1～15中任一项所述的正极活性材料。
  17. 根据权利要求16所述的正极极片，其中，所述正极极片的压实密度为3.3 g/cm 3～3.7 g/cm 3。
  18. 一种电化学储能装置，其包括权利要求16或17所述正极极片、负极极片以及隔离膜，其中，所述隔离膜设置于所述正极极片和所述负极极片之间。
  19. 一种二次电池，其包括权利要求16或17所述正极极片以及权利要求18所述电化学储能装置中至少一种。
  20. 一种用电装置，其包括权利要求16或17所述正极极片，权利要求18所述电化学储能装置以及权利要求19所述二次电池中至少一种。
  21. 一种正极活性材料的制备方法，其包括如下步骤：将所述A颗粒和所述B颗粒按照预设质量比进行混合，制备得到所述正极活性材料；所述A颗粒和B颗粒如权利要求1～15中任一项所定义；
    其中，所述A颗粒采用包括如下步骤的方法制备得到：将氢氧化锂、镍钴M体前驱体材料Ni xCo yM 1-x-y(OH) 2以及可选的Q添加剂和可选的N添加剂混合，在氧气存在及温度T1条件下进行一次烧结；可选地，向一次烧结产物中加入X添加剂和N添加剂中至少一种，混合，在氧气存在下进行二次烧结；
    其中，所述B颗粒采用包括如下步骤的方法制备得到：将氢氧化锂、镍钴M体前驱体材料Ni xCo yM 1-x-y(OH) 2以及可选的Q添加剂和可选的N添加剂混合，在氧气存在及温度T2条件下进行一次烧结；可选地，向一次烧结产物中加入X添加剂和N添加剂中至少一种，混合，在氧气存在下进行二次烧结；
    其中，所述Q添加剂、N添加剂、X添加剂分别为含有Q元素的添加剂、含有N元素的添加剂、含有X元素的添加剂；
    其中，x、y、M元素、Q元素、X元素和N元素如权利要求5所定义；
    所述温度T1高于所述温度T2；
    可选地，制备所述A颗粒的步骤中，在氧气存在条件下烧结的步骤中，一次烧结温度为700℃～950℃，可选地750℃～900℃，二次烧结温度为300℃～600℃，可选地350℃～550℃；
    可选地，制备所述B颗粒的步骤中，在氧气存在条件下烧结的步骤中，一次烧结温度为700℃～900℃，可选地750℃～850℃，二次烧结温度为300℃～600℃，可选地350℃～550℃。
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