WO2025077631A1 - 正极材料前驱体、单晶正极材料及制备方法、锂离子电池 - Google Patents

正极材料前驱体、单晶正极材料及制备方法、锂离子电池 Download PDF

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WO2025077631A1
WO2025077631A1 PCT/CN2024/122465 CN2024122465W WO2025077631A1 WO 2025077631 A1 WO2025077631 A1 WO 2025077631A1 CN 2024122465 W CN2024122465 W CN 2024122465W WO 2025077631 A1 WO2025077631 A1 WO 2025077631A1
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positive electrode
electrode material
single crystal
precursor
material precursor
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English (en)
French (fr)
Inventor
刘国学
万基平
郑玉
饶响响
吴小珍
杨顺毅
黄友元
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BTR Nano Tech Co Ltd
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BTR Nano Tech Co Ltd
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Priority to EP24863834.8A priority Critical patent/EP4576259A4/en
Priority to CN202480006708.XA priority patent/CN120604355A/zh
Priority to KR1020257008414A priority patent/KR20250044788A/ko
Priority to US19/033,218 priority patent/US20250163611A1/en
Priority to MA71202A priority patent/MA71202A1/fr
Publication of WO2025077631A1 publication Critical patent/WO2025077631A1/zh
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Definitions

  • the present application relates to the technical field of positive electrode materials, and in particular to positive electrode material precursors, single crystal positive electrode materials and preparation methods, and lithium-ion batteries.
  • Lithium-ion cathode materials are mainly divided into lithium iron phosphate and ternary materials.
  • Lithium iron phosphate is superior to ternary materials in cost, cycle life and thermal stability, and is suitable for commercial vehicles, low-end and mid-range passenger cars, energy storage and other fields.
  • Ternary materials have high energy density and good low-temperature performance, and are suitable for mid-end and high-end passenger cars.
  • Traditional polycrystalline ternary cathode materials are composed of primary particles (hundreds of nanometers) tightly agglomerated into spherical secondary particles (particle size is usually >10 ⁇ m). During the charge and discharge process, as the lattice shrinks, local stress is easily generated along the grain boundary, causing the material structure to collapse, forming microcracks, and causing the capacity of the cathode material to decay rapidly. Single crystalization is a method to improve the cycle performance of ternary materials. Single crystal ternary materials are composed of dispersed primary particles (the particle size is generally a few microns, and most of the particles are single grains with the same orientation), and there are no secondary spherical particles.
  • single crystal ternary materials Due to the elimination of grain boundaries, the cracking of the cathode material during the charge and discharge process can be suppressed, showing excellent stability.
  • single crystal ternary materials also face other problems. The diffusion path of Li in single crystal ternary materials is long, resulting in slow Li transmission power, and the performance is manifested as large DC internal resistance (DCR) and poor rate performance.
  • DCR DC internal resistance
  • single crystal particles can suppress particle cracking, crystal plane slip and dislocation still occur during the cycle, further generating microcracks.
  • Ternary single crystal cathode materials are generally prepared by high-temperature sintering of Ni/Co/Mn-containing precursor compounds and lithium salts. During the sintering process, the formation of cathode materials is usually very slow, and the growth rate is uneven, resulting in stress concentration inside the cathode materials formed; in addition, due to the limitation of ion diffusion, there are concentration differences in the distribution of elements in the ternary materials, resulting in mismatched lattice parameters inside the materials.
  • the purpose of the present application is to provide a cathode material precursor, a single crystal cathode material and a preparation method, and a lithium ion battery.
  • the single crystal cathode material provided by the present application has low lattice strain, which can reduce the diffusion energy barrier of lithium ions between microcrystals and improve the Li ion diffusion coefficient, so that the single crystal cathode material exhibits a lower DCR and has good rate performance; it can also reduce the occurrence of crystal plane slip, dislocation and the like, thereby inhibiting the generation of microcracks and improving the structural stability of the single crystal cathode material. properties, thereby improving the cycle performance of single crystal positive electrode materials.
  • the single crystal positive electrode material When observing the single crystal positive electrode material with a scanning electron microscope, at a magnification of 3K, 10 points of the single crystal positive electrode material are randomly selected for EDS point scanning to test the Ni, Co, and Mn contents.
  • the standard deviation of the mass content of each element of Ni, Co, and Mn in the single crystal positive electrode material is ⁇ 0.03;
  • the lattice strain of the single crystal positive electrode material is ⁇ , and ⁇ is less than 0.2%.
  • the single crystal positive electrode material includes SO 4 2 ⁇ , and the content of SO 4 2 ⁇ is ⁇ , wherein 0 ppm ⁇ 800 ppm.
  • the single crystal positive electrode material contains at least one single grain with the same orientation, wherein the average grain size of the single grain is 1 ⁇ m to 5 ⁇ m.
  • the grain size of the single crystal positive electrode material is D, 150nm ⁇ D ⁇ 250nm.
  • the average particle size D 50 of the single crystal positive electrode material is 1.5 ⁇ m to 5 ⁇ m.
  • the tap density of the single crystal positive electrode material is greater than 1.5 g/cm 3 .
  • the range of the mass content of each element Ni, Co and Mn in the single crystal positive electrode material is ⁇ 0.08.
  • the surface area weighted average particle size D[3, 2] of the positive electrode material precursor is less than 2.0 ⁇ m, and the standard deviation of the mass content of each element Ni, Co and Mn in the positive electrode material precursor is less than or equal to 0.05.
  • the range of the mass content of each element Ni, Co and Mn in the positive electrode material precursor is ⁇ 0.12.
  • the cathode material precursor includes secondary particles, and the secondary particles include a plurality of agglomerated primary particles.
  • the cathode material precursor includes secondary particles, the secondary particles include a plurality of agglomerated primary particles, and the primary particles are spherical.
  • the cathode material precursor includes secondary particles, the secondary particles include a plurality of agglomerated primary particles, and the particle size of the primary particles is 20 nm to 1000 nm.
  • the average particle size D 50 of the cathode material precursor is less than 3.5 ⁇ m.
  • the specific surface area of the cathode material precursor is greater than 5 m 2 /g.
  • the tap density of the cathode material precursor is greater than 1 g/cm 3 .
  • the present application provides a method for preparing a single crystal positive electrode material, comprising the following steps:
  • a mixed solution containing nickel salt, cobalt salt and manganese salt is atomized and then thermally decomposed to obtain a positive electrode material precursor, wherein the surface area weighted average particle size D[3,2] of the positive electrode material precursor is less than 2.0 ⁇ m, and the standard deviation of the mass content of each element Ni, Co and Mn in the positive electrode material precursor is ⁇ 0.05; the positive electrode material precursor is mixed with a lithium source and then sintered in an oxygen-containing atmosphere to obtain a single crystal positive electrode material, wherein the standard deviation of the mass content of each element Ni, Co and Mn in the single crystal positive electrode material is ⁇ 0.03; the lattice strain of the single crystal positive electrode material is ⁇ , and ⁇ is less than 0.2%.
  • the cathode material precursor includes SO 4 2 ⁇ , and the content of SO 4 2 ⁇ is ⁇ , wherein 0ppm ⁇ 1800ppm.
  • the nickel salt includes at least one of nickel chloride, nickel sulfate, nickel nitrate, nickel carbonate, nickel oxalate, and nickel acetate.
  • the cobalt salt includes at least one of cobalt chloride, cobalt oxalate, cobalt carbonate, cobalt sulfate, cobalt nitrate, and cobalt acetate.
  • the manganese salt includes at least one of manganese chloride, manganese carbonate, manganese sulfate, manganese oxalate, manganese nitrate, and manganese acetate.
  • the molar ratio of Ni, Co and Mn in the mixed solution is (50-98):(0-20):(0-30), and the content of Co and Mn in the mixed solution is not zero.
  • the total metal concentration in the mixed solution is 200 g/L to 500 g/L.
  • the mixed solution further includes a dopant containing an N element, wherein N includes at least one of Al, Ti, Zr, Mg, Sr, Ba, Ca, Nb, W, Sb, Ta, Sn, and Y.
  • N includes at least one of Al, Ti, Zr, Mg, Sr, Ba, Ca, Nb, W, Sb, Ta, Sn, and Y.
  • the range of the mass content of each element Ni, Co and Mn in the positive electrode material precursor is ⁇ 0.12.
  • the flow rate of the mixed solution is 100 L/h to 900 L/h.
  • the pressure of the atomization treatment is 0.4 MPa to 0.8 MPa.
  • the primary sintering temperature is 500°C to 850°C.
  • the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium acetate, lithium sulfate, lithium chloride, lithium nitrate and lithium oxalate.
  • the molar ratio of lithium in the lithium source to the sum of nickel, cobalt and manganese in the positive electrode material precursor is 0.98 to 1.10.
  • the sintering temperature is 750°C to 950°C.
  • the sintering time is 10 h to 30 h.
  • an embodiment of the present application provides a lithium-ion battery, wherein the lithium-ion battery comprises the single crystal positive electrode material described in the first aspect or the single crystal positive electrode material prepared by the method for preparing the single crystal positive electrode material described in the third aspect.
  • the single crystal positive electrode material provided in the present application randomly selects 10 points of the single crystal positive electrode material for EDS point scanning to test the Ni, Co, and Mn contents.
  • the standard deviation of the mass content of each element Ni, Co and Mn in the single crystal positive electrode material is ⁇ 0.03, indicating that the distribution uniformity of Ni, Co, and Mn elements inside the single crystal positive electrode material is good, which is conducive to reducing the crystal structure defects of the single crystal positive electrode material;
  • the lattice strain ⁇ of the single crystal positive electrode material is less than 0.2%, which can reduce the diffusion energy barrier of lithium ions between crystallites and increase the Li ion diffusion coefficient, so that the single crystal positive electrode material exhibits good rate performance and low DCR; at the same time, low lattice strain can also inhibit the generation of microcracks in the single crystal positive electrode material, thereby improving the cycle performance of the single crystal positive electrode material.
  • the positive electrode material precursor provided by the present application has a surface area weighted average particle size D[3,2] ⁇ 2.0 ⁇ m, has high reaction activity, and is beneficial to improving the reaction efficiency and mass transfer efficiency in the subsequent preparation process of the positive electrode material from the positive electrode material precursor; at the same time, the standard deviation of the mass content of each element Ni, Co and Mn in the positive electrode material precursor obtained by the above preparation method is ⁇ 0.05, indicating that the distribution uniformity of Ni, Co and Mn elements in the positive electrode material precursor is good; using the positive electrode material precursor The positive electrode material is prepared, and the distribution uniformity of the Ni, Co, and Mn elements in the positive electrode material can be improved, so that the positive electrode material prepared by the positive electrode material precursor has fewer crystal structure defects and smaller lattice stress.
  • the single crystal positive electrode material preparation method provided in the present application is to obtain a positive electrode material precursor by atomizing a mixed solution containing nickel salt, cobalt salt and manganese salt and then thermally decomposing it.
  • the surface area weighted average particle size D[3,2] of the positive electrode material precursor is less than 2.0 ⁇ m, and the reaction activity is high, which is beneficial to improve the reaction efficiency and mass transfer efficiency of the positive electrode material precursor and the lithium source in the subsequent high-temperature sintering process; at the same time, the standard deviation of the mass content of each element Ni, Co and Mn in the positive electrode material precursor obtained by the above preparation method is ⁇ 0.05, indicating that the distribution uniformity of Ni, Co and Mn in the positive electrode material precursor is good; and then the single crystal positive electrode material prepared by the above positive electrode material precursor after subsequent sintering with the lithium source is The standard deviation of the mass content of the elements is ⁇ 0.03, and the distribution uniformity of Ni, Co, and Mn elements inside the single crystal positive electrode material is good, which is conduc
  • FIG1 is a SEM morphology of the cathode material precursor prepared in Example 1 of the present application.
  • FIG2 is another SEM morphology image of the cathode material precursor prepared in Example 1 of the present application.
  • FIG3 is an EDS spectrum result of the cathode material precursor prepared in Example 1 of the present application.
  • FIG. 4 is a Williamsone-Hall analysis fitting curve of the single crystal positive electrode material prepared in Example 1 of the present application.
  • the single crystal positive electrode material When observing the single crystal positive electrode material with a scanning electron microscope, at a magnification of 3K, 10 points of the single crystal positive electrode material are randomly selected for EDS point scanning to test the Ni, Co, and Mn contents.
  • the standard deviation of the mass content of each element of Ni, Co, and Mn in the single crystal positive electrode material is ⁇ 0.03;
  • the lattice strain of the single crystal positive electrode material is ⁇ , and ⁇ is less than 0.2%.
  • the single crystal positive electrode material provided in the present application randomly selects 10 points of the single crystal positive electrode material for EDS point scanning to test the Ni, Co, and Mn contents.
  • the standard deviation of the mass content of each element Ni, Co and Mn in the single crystal positive electrode material is ⁇ 0.03, indicating that the distribution uniformity of Ni, Co, and Mn elements inside the single crystal positive electrode material is good, which is conducive to reducing the crystal structure defects of the single crystal positive electrode material;
  • the lattice strain ⁇ of the single crystal positive electrode material is less than 0.2%, which can reduce the diffusion energy barrier of lithium ions between crystallites and increase the Li ion diffusion coefficient, so that the single crystal positive electrode material exhibits good rate performance and low DCR; at the same time, low lattice strain can also inhibit the generation of microcracks in the single crystal positive electrode material, thereby improving the cycle performance of the single crystal positive electrode material.
  • the value of x can be 0.98, 0.99, 1.0, 1.01, 1.03, 1.05, 1.08, 1.09 or 1.1, etc., and is not limited here.
  • a can be 0.50, 0.55, 0.60, 0.63, 0.70, 0.75, 0.80, 0.85, 0.88, 0.90, 0.95 or 0.98;
  • the value of b can be 0.01, 0.05, 0.08, 0.10, 0.11, 0.13, 0.15, 0.18 or 0.20;
  • the value of c can be 0.01, 0.05, 0.10, 0.15, 0.18, 0.20, 0.23, 0.27 or 0.30;
  • the value of d can be 0, 0.01, 0.03, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.10, etc., and is not limited here.
  • the standard deviation of the mass content of each element Ni, Co and Mn in the single crystal positive electrode material can be 0.01, 0.015, 0.02, 0.025, 0.026, 0.028 or 0.03, etc., which is not limited here.
  • the range of the mass content of each element Ni, Co and Mn in the single crystal positive electrode material is ⁇ 0.08, and can be specifically 0.01, 0.02, 0.028, 0.03, 0.05, 0.057, 0.06, 0.07, 0.075 or 0.08, etc. Of course, it can also be other values within the above range, which are not limited here.
  • the standard deviation and range of the mass content of each element Ni, Co and Mn in the single crystal positive electrode material in the present application are within the above range, indicating that the Ni, Co and Mn elements in the single crystal positive electrode material of the present application are evenly distributed, which is conducive to reducing the lattice defects of the single crystal positive electrode material, reducing the lattice stress, and improving the cycle performance and rate performance of the single crystal positive electrode material.
  • the lattice strain of the single crystal positive electrode material can specifically be 0.01%, 0.03%, 0.05%, 0.08%, 0.10%, 0.11%, 0.12%, 0.15%, 0.18% or 0.19%, etc., which is not limited here.
  • the single crystal positive electrode material further includes a coating layer, the coating layer includes a metal oxide or a lithium ion conductor, wherein the metal in the metal oxide includes at least one of Al, Ti, Zr, Y, Nb, Mg, W, B, Ce, Co and Mn.
  • the coating layer can reduce the direct contact between the single crystal positive electrode material and the electrolyte, reduce the occurrence of side reactions between the material and the electrolyte, and further improve the electrochemical performance of the single crystal positive electrode material.
  • the content of free SO 4 2- on the surface of the single crystal positive electrode material is less than or equal to 1000ppm, preferably ⁇ 800ppm.
  • the content of SO 4 2- in the single crystal positive electrode material can be specifically 0ppm, 5ppm, 10ppm, 50ppm, 100ppm, 200ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm or 1000ppm, etc.
  • the free SO 4 2- content is within the above range, the positive electrode material has better rate and cycle performance.
  • the co-precipitated precursor will have a relatively high content of sulfate ions remaining. Sulfate ions are difficult to decompose, so the sulfate ion content on the surface of the corresponding positive electrode material formed by subsequent sintering is relatively high (usually >1000ppm). Free sulfate ions will have an adverse effect on the electrochemical properties of the positive electrode material. When the content of free SO 4 2- on the surface is high, SO 4 2- combines with Li ions, binding some Li ions, causing the material capacity and rate to deteriorate; in addition, free SO 4 2- on the surface will also affect the stability of the SEI film.
  • the free SO 4 2- content on the surface of the single crystal positive electrode material is highly inherited from the free SO 4 2- content on the surface of the positive electrode material precursor.
  • the content of free SO 4 2- on the surface of the provided positive electrode material precursor is ⁇ 1000ppm, which is more conducive to preparing a positive electrode material with a content of free SO 4 2- on the surface of ⁇ 800ppm.
  • Ni salt, Mn salt, Co salt and N salt each independently include at least one of chloride, nitrate, oxalate and acetate.
  • Nitrate, chloride, oxalate and acetate of nickel, cobalt and manganese are very easy to decompose at high temperature, and there will be no obvious residue, so there is basically no effect on the performance of the positive electrode material.
  • By controlling the content of SO 4 2- in the metal salt mixed solution it is even possible to prepare a positive electrode material precursor with a content of SO 4 2- close to 0. However, this will require a high purity of the raw materials and will cause an increase in the cost of raw materials. It is more economical to use Ni source, Co source, Mn source and N source in the ternary recycled material containing SO 4 2- impurities as metal sources and to prepare the positive electrode material precursor by controlling the content of SO 4 2- in the metal source.
  • the content of SO 4 2- is ⁇ 800 ppm, which is more conducive to preparing a single crystal positive electrode material with a lower content of free SO 4 2- on the surface, further improving the capacity and rate performance of the single crystal positive electrode material.
  • the single crystal positive electrode material contains at least one single grain with the same orientation, wherein the average grain size of the single grain is 1 ⁇ m to 5 ⁇ m, such as 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, etc.
  • the single crystal particles of the positive electrode material of the present application are particles containing at least one single grain with the same orientation, and the average particle size of the single particles that meet the above conditions is 1 to 5um when measured under the EBSD test. It can stably achieve its own high filling while preventing the occurrence of cracks due to extrusion and other reasons after the particles reach their densest packing.
  • the particles have the same orientation, which can relieve the stress and strain of the positive electrode particles during the charge and discharge cycle, greatly reduce the cracking of the particles during the cycle, and thus greatly improve the structural stability of the positive electrode particles.
  • the grain orientation of the positive electrode material can at least be tested by electron backscatter diffraction (EBSD), and 100 single grains with the same orientation are randomly selected to measure the particle size of each grain, and the arithmetic mean is taken as the average particle size of the above single grains.
  • EBSD electron backscatter diffraction
  • single crystal positive electrode materials and polycrystalline ternary positive electrode materials (i.e., polycrystalline secondary particles)
  • polycrystalline secondary particles the difference between single crystal positive electrode materials and polycrystalline ternary positive electrode materials is that the smallest particle of polycrystalline secondary particles is a secondary particle formed by the agglomeration of primary particles.
  • the smallest particle is usually a monomer primary particle of micrometer size.
  • characterization methods such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD).
  • SEM scanning electron microscopy
  • TEM transmission electron microscopy
  • XRD X-ray diffraction
  • TEM is an auxiliary second characterization method, which observes whether the crystal plane orientation of the obtained product is consistent, and is further characterized in combination with selected area electron diffraction (SAED).
  • SAED selected area electron diffraction
  • the above methods can be used to determine whether it is a single crystal positive electrode material.
  • the single crystal positive electrode material of the present application can be understood as a positive electrode material particle containing at least one single grain with the same orientation, and the average particle size of the above single grain is 1 ⁇ m-5 ⁇ m.
  • a single grain in the present application can be a single particle composed of a primary particle.
  • the above-mentioned single crystal positive electrode material may also contain a small amount of "quasi-secondary particles” formed by the adhesion of several single particles.
  • Primary particle refers to the smallest particle unit identified when observing the positive electrode active material through a scanning electron microscope
  • secondary particle refers to a secondary structure formed by the agglomeration of multiple primary particles, showing a relatively rounded spherical morphology.
  • Quasi-secondary particles refer to those formed by the adhesion of several single particles.
  • the particle size of a single particle in the above-mentioned quasi-secondary particles is usually between 1um-5um.
  • the roundness of the particles of the "quasi-secondary particles" is lower than that of the above-mentioned conventional "secondary particles".
  • the "single crystal cathode material" known to those skilled in the art is not a “single crystal” in the strict sense.
  • an ideal single crystal refers to a crystal with completely the same arrangement and orientation.
  • ideal single crystals are very rare and difficult to produce in the laboratory. Therefore, the single crystal cathode materials known in the art are not single crystals.
  • the material is actually more of a "single crystal morphology" positive electrode material, which only exhibits large single crystal-like particle size in size, as distinguished from polycrystalline composed of numerous small primary particles.
  • the grain size of the single crystal positive electrode material is D, 150nm ⁇ D ⁇ 250nm.
  • the grain size of the single crystal positive electrode material can specifically be 151nm, 155nm, 160nm, 170nm, 185nm, 190nm, 200nm, 205nm, 230nm or 245nm, etc., which is not limited here. If the grain size of the single crystal positive electrode material is less than 150nm, the cycle stability of the single crystal positive electrode material is poor; if the grain size of the single crystal positive electrode material is greater than 250nm, the capacity and rate performance of the single crystal positive electrode material are poor. Controlling the grain size of the single crystal positive electrode material within the above range is beneficial to improving the electrochemical performance of the single crystal positive electrode material.
  • the calculation method of grain size is generally calculated by Scherrer formula using half-width.
  • This method has a premise assumption, that is, the lattice stress is 0, and the broadening of the diffraction peak is entirely caused by the grain size.
  • the lattice stress inside the single crystal positive electrode material cannot be completely ignored, and many factors cause stress concentration inside the single crystal positive electrode material. Therefore, the grain size calculated using the Scherrer formula has its inherent limitations.
  • This application uses the Williamsone-Hall method to separate the diffraction peak broadening caused by the crystallite size and the diffraction peak broadening caused by the lattice stress, so the calculated grain size can better reflect the electrochemical properties of the material.
  • the average particle size D50 of the single crystal positive electrode material is 1.5 ⁇ m to 5 ⁇ m, specifically 1.5 ⁇ m, 1.8 ⁇ m, 2 ⁇ m, 2.5 ⁇ m, 3 ⁇ m, 3.5 ⁇ m, 4 ⁇ m, 4.5 ⁇ m or 5 ⁇ m, etc., and of course, other values within the above range are also possible, which are not limited here. Controlling the particle size of the single crystal positive electrode material within the above range is conducive to improving the structural stability, thermal stability and long cycle stability of the single crystal positive electrode material.
  • the tap density of the single crystal positive electrode material is greater than 1.5 g/cm 3 , and can be specifically 1.55 g/cm 3 , 1.58 g/cm 3 , 1.62 g/cm 3 , 1.63 g/cm 3 , 1.65 g/cm 3 , 1.70 g/cm 3 or 1.75 g/cm 3 , etc., and can also be other values within the above range, which is not limited here.
  • the tap density of the single crystal positive electrode material is controlled within the above range, it is beneficial to improve the energy density of the battery made of the single crystal positive electrode material.
  • the compaction density of the single crystal positive electrode material is greater than 3.0 g/cm 3 , and may be 3.1 g/cm 3 , 3.2 g/cm 3 , 3.3 g/cm 3 , 3.5 g/cm 3 , 3.7 g/cm 3 , 3.9 g/cm 3 or 4.1 g/cm 3 , etc. Of course, it may also be other values within the above range, which is not limited here.
  • the surface area weighted average particle size D[3, 2] of the positive electrode material precursor is less than 2.0 ⁇ m, and the standard deviation of the mass content of each element Ni, Co and Mn in the positive electrode material precursor is less than or equal to 0.05.
  • the crystal growth rate of each micro-region inside the material is different due to the limitation of ion diffusion rate and temperature gradient, and the unit cell parameters are different, which will cause the accumulation of lattice stress inside the material; lattice stress will increase the diffusion energy barrier of Li ions between each crystal plane/grain boundary, reduce the Li ion diffusion coefficient, and finally increase the DCR of the material.
  • the morphology and structural characteristics of the cathode material precursor have good inheritance for the cathode material, so the composition and structure of the cathode material precursor have a direct impact on the performance of the final cathode material.
  • the positive electrode material precursor provided by the present application has a surface area weighted average particle size D[3, 2] ⁇ 2.0 ⁇ m, high reaction activity, and is beneficial to improving the reaction efficiency and mass transfer efficiency in the subsequent preparation process of the positive electrode material from the positive electrode material precursor; at the same time, the standard deviation of the mass content of each element Ni, Co and Mn in the positive electrode material precursor obtained by the above preparation method is ⁇ 0.05, indicating that the distribution uniformity of Ni, Co and Mn elements in the positive electrode material precursor is good; the positive electrode material is prepared by using the positive electrode material precursor, which can improve the distribution uniformity of Ni, Co and Mn elements in the positive electrode material, so that the crystal structure of the positive electrode material prepared by the positive electrode material precursor is Fewer defects and less lattice stress.
  • the cathode material precursor includes SO 4 2 ⁇ , and the content of SO 4 2 ⁇ is ⁇ , wherein 0ppm ⁇ 1800ppm.
  • the free SO 4 2- content on the surface of the positive electrode material may have a certain inheritance with the free SO 4 2- content in the precursor.
  • the higher the SO 4 2- content in the precursor the higher the free SO 4 2- content on the surface of the ternary positive electrode material.
  • the free SO 4 2- content on the surface of the positive electrode material precursor provided in the present application is ⁇ 1800ppm, which is more conducive to the preparation of a positive electrode material with a free SO 4 2- content on the surface ⁇ 800ppm.
  • the Ni salt, the Mn salt, the Co salt and the N salt each independently include at least one of chloride, nitrate, oxalate and acetate, and avoid the use of nickel sulfate, cobalt sulfate and manganese sulfate.
  • Nitrates, chlorides, oxalates, and acetates of nickel, cobalt, and manganese are very easy to decompose at high temperatures, and no obvious residues will remain, so they have little effect on the performance of the positive electrode material.
  • the content of SO4 2- in the metal salt mixed solution is ⁇ 1800ppm based on the total mass of Ni, Co and Mn. Specifically, it can be 500ppm, 800ppm, 1200ppm, 1600ppm, 1700ppm or 1800ppm, etc., which is not limited here.
  • the average particle size D50 is generally used to characterize the particle size of the cathode material precursor.
  • the reaction between the cathode material precursor and the lithium salt is a process related to the contact area, so the Sauter average particle size, that is, the surface area weighted average particle size D[3,2] is actually more suitable for characterizing the particle size of the cathode material precursor.
  • the larger D[3,2] is, the smaller the surface activity of the cathode material precursor is, and the slower the reaction rate with the lithium salt is.
  • the surface area weighted average particle size D[3,2] of the positive electrode material precursor can be 1.98 ⁇ m, 1.95 ⁇ m, 1.8 ⁇ m, 1.75 ⁇ m, 1.64 ⁇ m, 1.5 ⁇ m, 1.3 ⁇ m, 1.2 ⁇ m, 1.1 ⁇ m, 0.8 ⁇ m, 0.9 ⁇ m or 0.5 ⁇ m, etc., which is not limited here.
  • the surface area weighted average particle size D[3,2] of the positive electrode material precursor is controlled within the above range, the reaction activity of the positive electrode material precursor is high, which is beneficial to improving the reaction efficiency and mass transfer efficiency of the positive electrode material precursor in the subsequent sintering process with the lithium source.
  • the standard deviation of the mass content of each element Ni, Co and Mn in the positive electrode material precursor can be 0.001, 0.005, 0.009, 0.01, 0.013, 0.02, 0.025, 0.03, 0.036, 0.04, 0.044, 0.045, 0.047 or 0.049, etc., which is not limited here.
  • the range of the mass content of each element Ni, Co and Mn in the positive electrode material precursor is ⁇ 0.12, and can be specifically 0.01, 0.015, 0.018, 0.02, 0.029, 0.03, 0.035, 0.048, 0.059, 0.06, 0.08, 0.097, 0.10, 0.105, 0.11, 0.112, 0.115 or 0.119, etc., and of course, it can also be other values within the above range, which are not limited here.
  • the standard deviation and range of the mass content of each element Ni, Co and Mn in the positive electrode material can reflect the uniformity of the distribution of Ni, Co and Mn elements in the positive electrode material precursor.
  • the lower the standard deviation and range of the mass content of each element Ni, Co and Mn the more uniform the distribution of Ni, Co and Mn elements in the positive electrode material precursor.
  • the distribution uniformity of Ni, Co and Mn elements in the positive electrode material precursor and the distribution uniformity of Ni, Co and Mn elements in the single crystal positive electrode material are There is a good inheritance between them.
  • controlling the standard deviation and range of the mass content of each element Ni, Co and Mn in the positive electrode material precursor within the above range is beneficial to improving the distribution uniformity of Ni, Co and Mn elements in the single crystal positive electrode material, so that the distribution uniformity of Ni, Co and Mn elements in the single crystal positive electrode material is good, the single crystal positive electrode material has fewer crystal structure defects and low lattice strain.
  • the cathode material precursor includes secondary particles, and the secondary particles include a plurality of agglomerated primary particles.
  • the cathode material precursor includes secondary particles, the secondary particles include a plurality of agglomerated primary particles, and the primary particles are spherical.
  • the positive electrode material precursor includes secondary particles, and the secondary particles include a plurality of agglomerated primary particles, and the particle size of the primary particles is 20nm to 1000nm, specifically 20nm, 50nm, 80nm, 100nm, 150nm, 200nm, 500nm, 800nm or 1000nm, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.
  • the particle size of the primary particles is greater than 1000nm, the reaction activity on the surface of the positive electrode material precursor is poor, the lattice strain of the prepared single crystal positive electrode material is large, and the cycle performance and rate performance of the single crystal positive electrode material are poor.
  • the tap density of the positive electrode material precursor is low, resulting in a low tap density of the prepared single crystal positive electrode material. Controlling the particle size of the primary particles within the above range is conducive to improving the cycle performance and rate performance of the single crystal positive electrode material made from the positive electrode material precursor.
  • the average particle size D 50 of the positive electrode material precursor is less than 3.5 ⁇ m, specifically, it can be 0.5 ⁇ m, 0.8 ⁇ m, 1.2 ⁇ m, 1.5 ⁇ m, 2 ⁇ m, 2.5 ⁇ m, 3 ⁇ m, 3.2 ⁇ m or 3.5 ⁇ m, etc., and of course, it can also be other values within the above range, which is not limited here.
  • the particle size D 50 of the positive electrode material precursor is controlled within the above range, it is beneficial to improve the reaction activity of the positive electrode material precursor.
  • the specific surface area of the positive electrode material precursor is ⁇ 5m 2 /g, specifically 5m 2 /g, 6m 2 /g, 8m 2 /g, 10m 2 /g, 12m 2 /g, 15m 2 /g, 20m 2 /g, 25m 2 /g, 50m 2 /g or 100m 2 / g, etc., and of course, it can also be other values within the above range, which is not limited here.
  • the larger the specific surface area of the positive electrode material precursor the higher the reaction activity of the positive electrode material precursor, which is conducive to the reaction of the lithium source and the positive electrode material precursor, and can reduce the lattice defects of the single crystal positive electrode material prepared from the positive electrode material precursor.
  • the tap density of the cathode material precursor>1g/ cm3 may be 1.1g/ cm3 , 1.2g/cm3, 1.3g/ cm3 , 1.8g/ cm3 , 2.3g/ cm3 , 2.5g/ cm3 or 3g/ cm3 , etc., and of course, it may also be other values within the above range, which is not limited here.
  • the tap density of the cathode material precursor is controlled within the above range, it is beneficial to improve the tap density of the prepared single crystal cathode material, thereby improving the energy density of the battery.
  • the present application provides a method for preparing a single crystal positive electrode material, comprising the following steps:
  • Step S100 atomizing a mixed solution containing nickel salt, cobalt salt and manganese salt, and then thermally decomposing it to obtain a positive electrode material precursor, wherein the surface area weighted average particle size D[3,2] of the positive electrode material precursor is less than 2.0 ⁇ m, and the standard deviation of the mass content of each element Ni, Co and Mn in the positive electrode material precursor is ⁇ 0.05;
  • Step S200 after mixing the positive electrode material precursor with a lithium source, sintering in an oxygen-containing atmosphere to obtain a positive electrode material, the standard deviation of the mass content of each element Ni, Co and Mn in the single crystal positive electrode material is ⁇ 0.03; the lattice strain of the single crystal positive electrode material is ⁇ , and ⁇ 0.2%.
  • the single crystal positive electrode material preparation method provided in the present application is to obtain a positive electrode material precursor by atomizing a mixed solution containing nickel salt, cobalt salt and manganese salt and then performing thermal decomposition.
  • the surface area weighted average particle size D[3,2] of the positive electrode material precursor is less than 2.0 ⁇ m, and the reaction activity is high, which is conducive to improving the reaction of the positive electrode material precursor and the lithium source in the subsequent high temperature sintering process.
  • the standard deviation of the mass content of each element Ni, Co and Mn in the positive electrode material precursor obtained by the above preparation method is ⁇ 0.05, indicating that the distribution uniformity of Ni, Co and Mn in the positive electrode material precursor is good; furthermore, the standard deviation of the mass content of each element Ni, Co and Mn in the single crystal positive electrode material prepared by subsequent sintering of the above positive electrode material precursor with a lithium source is ⁇ 0.03, and the distribution uniformity of Ni, Co and Mn elements inside the single crystal positive electrode material is good, which is conducive to reducing the crystal structure defects of the single crystal positive electrode material; and the lattice strain of the single crystal positive electrode material is low, and its lattice strain ⁇ is less than 0.2%, which can reduce the diffusion energy barrier of lithium ions between crystallites and improve the Li ion diffusion coefficient, so that the single crystal positive electrode material exhibits good rate performance and low DCR; at the same time, low lattice strain can also inhibit the generation of microcracks
  • Step S100 a mixed solution containing nickel salt, cobalt salt and manganese salt is atomized and then thermally decomposed to obtain a positive electrode material precursor, wherein the surface area weighted average particle size D[3, 2] of the positive electrode material precursor is less than 2.0 ⁇ m, and the standard deviation of the mass content of each element Ni, Co and Mn in the positive electrode material precursor is ⁇ 0.05.
  • the surface area weighted average particle size D[3,2] of the positive electrode material precursor can be 1.98 ⁇ m, 1.95 ⁇ m, 1.8 ⁇ m, 1.75 ⁇ m, 1.64 ⁇ m, 1.5 ⁇ m, 1.3 ⁇ m, 1.2 ⁇ m, 1.1 ⁇ m, 0.8 ⁇ m, 0.9 ⁇ m or 0.5 ⁇ m, etc., which is not limited here.
  • the surface area weighted average particle size D[3,2] of the positive electrode material precursor is controlled within the above range, the reaction activity of the positive electrode material precursor is high, which is beneficial to improve the reaction efficiency and mass transfer efficiency of the positive electrode material precursor in the subsequent sintering process with the lithium source.
  • the surface area weighted average particle size D[3,2] of the precursor is mainly related to the pyrolysis temperature. As the pyrolysis temperature increases, the surface area weighted average particle size D[3,2] increases, and the reaction activity of the precursor decreases.
  • the standard deviation of the mass content of each element Ni, Co and Mn in the positive electrode material precursor can be 0.001, 0.005, 0.009, 0.01, 0.013, 0.02, 0.025, 0.03, 0.036, 0.01, 0.044, 0.045, 0.047 or 0.049, etc., which is not limited here.
  • the nickel salt includes at least one of nickel chloride, nickel sulfate, nickel nitrate, nickel carbonate, nickel oxalate, and nickel acetate.
  • the cobalt salt includes at least one of cobalt chloride, cobalt oxalate, cobalt carbonate, cobalt sulfate, cobalt nitrate, and cobalt acetate.
  • the manganese salt includes at least one of manganese chloride, manganese carbonate, manganese sulfate, manganese oxalate, manganese nitrate, and manganese acetate.
  • the molar ratio of Ni, Co and Mn in the mixed solution is (50-98): (0-20): (0-30), and the content of Co and Mn in the mixed solution is not 0.
  • the molar ratio of Ni, Co and Mn in the mixed solution can be 50:0.1:0.1, 60:10:30, 65:15:20, 65:5:30, 70:5:25, 70:10:20, 80:5:15, 85:10:5 or 98:1:1, etc., which is not limited here.
  • the total metal concentration in the mixed solution is 200 g/L to 500 g/L, specifically 200 g/L, 220 g/L, 260 g/L, 300 g/L, 350 g/L, 400 g/L, 450 g/L, 480 g/L or 500 g/L, etc., and of course, other values within the above range are also possible, which are not limited here.
  • the applicant has found that the metal concentration in the mixed solution can affect the preparation efficiency of the precursor and the degree of thermal decomposition reaction. When the metal concentration of the mixed liquid is too high, it may lead to incomplete precursor reaction, which will not only cause structural instability but also make the uniformity of particle element distribution unsatisfactory.
  • the mixed solution further includes a dopant containing an N element, wherein N includes at least one of Al, Ti, Zr, Mg, Sr, Ba, Ca, Nb, W, Sb, Ta, Sn, and Y.
  • N includes at least one of Al, Ti, Zr, Mg, Sr, Ba, Ca, Nb, W, Sb, Ta, Sn, and Y.
  • the mixed solution further includes an ultrasonic stirring step before the atomization treatment, and the ultrasonic stirring includes placing the mixed solution in a reactor with ultrasonic stirring function for heating and ultrasonic stirring.
  • the ultrasonic stirring temperature is 50°C to 70°C.
  • the ultrasonic stirring has an ultrasonic frequency of 30 KHz-50 KHz, and an ultrasonic stirring time of 0.5 h-2 h.
  • Heating and ultrasonic stirring before atomization can further fully mix the chemical elements in the mixed liquid and quickly obtain more uniform droplets, so that the distribution of elements on the surface of the precursor particles is more uniform during thermal decomposition, with a smaller standard deviation mean value of the mass content.
  • a surfactant is added to the mixed solution before atomization, and the surfactant includes polyethylene glycol.
  • the surfactant accounts for 0.5%-5% of the total mass of the mixed solution.
  • the surfactant within the above range can stably obtain precursor particles with smooth morphology, uniformity and good dispersion. If the concentration is too low, the surfactant will not play a significant role, and if it is too high, it will not only affect the overall concentration of the mixture, but also cause the precipitation of Ni, Co, and Mn metal ions.
  • the mixed solution further includes an ultrasonic stirring step before atomization treatment, wherein the mixed solution is placed in a reactor with ultrasonic stirring function and heated to 50°C to 70°C, and the ultrasonic stirring frequency is adjusted to 30-50KHz. After ultrasonic stirring in the reactor for 0.5h-2h, the heating function is turned off and 0.5%-5% of the total mass of polyethylene glycol is added to the mixed solution, and then ultrasonic stirring is performed for 0.5h-1h.
  • an ultrasonic stirring step before atomization treatment wherein the mixed solution is placed in a reactor with ultrasonic stirring function and heated to 50°C to 70°C, and the ultrasonic stirring frequency is adjusted to 30-50KHz. After ultrasonic stirring in the reactor for 0.5h-2h, the heating function is turned off and 0.5%-5% of the total mass of polyethylene glycol is added to the mixed solution, and then ultrasonic stirring is performed for 0.5h-1h.
  • the range of the mass content of each element Ni, Co and Mn in the positive electrode material precursor is ⁇ 0.12, and can be specifically 0.01, 0.015, 0.018, 0.02, 0.029, 0.03, 0.035, 0.048, 0.059, 0.06, 0.08, 0.097, 0.10, 0.105, 0.11, 0.112, 0.115 or 0.119, etc., and of course, it can also be other values within the above range, which are not limited here.
  • the standard deviation and range of the mass content of each element Ni, Co and Mn in the positive electrode material can reflect the uniformity of the distribution of Ni, Co and Mn elements in the positive electrode material precursor.
  • the lower the standard deviation and range of the mass content of each element Ni, Co and Mn the more uniform the distribution of Ni, Co and Mn elements in the positive electrode material precursor.
  • the more uniform the distribution of Ni, Co and Mn elements in the positive electrode material precursor the more uniform the distribution of Ni, Co and Mn elements in the single crystal positive electrode material made from the positive electrode material precursor.
  • Controlling the standard deviation and range of the mass content of each element Ni, Co and Mn in the positive electrode material precursor within the above range is beneficial to improving the distribution uniformity of Ni, Co and Mn elements in the single crystal positive electrode material, so that the distribution uniformity of Ni, Co and Mn elements in the single crystal positive electrode material is good, the single crystal positive electrode material has fewer crystal structure defects and low lattice strain.
  • the flow rate of the mixed solution is 100L/h to 900L/h, specifically 100L/h, 200L/h, 300L/h, 400L/h, 500L/h, 600L/h, 700L/h, 800L/h or 900L/h, etc., which are not limited here.
  • the higher the flow rate of the mixed solution the faster the synthesis speed of the precursor, but the uniformity of the Ni/Co/Mn distribution deteriorates.
  • the pressure of the atomization treatment is 0.4 MPa to 0.8 MPa, specifically 0.4 MPa, 0.5 MPa, 0.6MPa, 0.7MPa, 0.75MPa or 0.8MPa, etc., of course, it can also be other values within the above range, which is not limited here.
  • the temperature of the thermal decomposition is 500°C to 850°C, specifically 500°C, 550°C, 600°C, 650°C, 700°C, 750°C or 800°C, etc., but is not limited to the listed values, and other values not listed in the numerical range are also applicable.
  • the thermal decomposition temperature increases, the surface area weighted average particle size D[3,2] of the positive electrode material precursor will decrease, resulting in a decrease in the activity of the precursor.
  • the thermal decomposition temperature is higher than 850°C, the surface area weighted average particle size D[3,2] of the positive electrode material precursor is greater than 2.0 ⁇ m; at this time, the reaction activity of the positive electrode material precursor is poor, resulting in more defects in the single crystal positive electrode material prepared subsequently, and the lattice strain ⁇ exceeds 0.2%, so that the single crystal positive electrode material exhibits poor rate performance, higher DCR and lower cycle performance. Therefore, appropriately reducing the thermal decomposition temperature of the precursor is conducive to improving the reaction activity of the precursor and improving the rate and DCR of the positive electrode material.
  • the metal salts of Ni, Co and Mn are not completely decomposed, resulting in excessive anion content of precursors such as Cl- , NO3- , and CO32- .
  • these residual anions will inhibit the formation of single crystals and corrode the sintering furnace.
  • Step S200 after mixing the positive electrode material precursor with a lithium source, sintering in an oxygen-containing atmosphere to obtain a positive electrode material, the standard deviation of the mass content of each element Ni, Co and Mn in the single crystal positive electrode material is ⁇ 0.03; the lattice strain of the single crystal positive electrode material is ⁇ , and ⁇ 0.2%.
  • the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium acetate, lithium sulfate, lithium chloride, lithium nitrate and lithium oxalate.
  • the molar ratio of lithium in the lithium source to the sum of nickel, cobalt and manganese in the positive electrode material precursor is 0.98-1.10, specifically 0.98, 0.99, 1.01, 1.03, 1.05, 1.06, 1.08, 1.09 or 1.10, etc., and of course it can also be other values within the above range, which is not limited here.
  • the temperature of the sintering reaction is 750°C to 950°C, specifically 750°C, 760°C, 780°C, 800°C, 850°C, 900°C, 920°C or 950°C, etc.
  • the sintering temperature is closely related to the Ni content. The higher the Ni content, the lower the sintering temperature.
  • a suitable sintering temperature is conducive to reducing crystal structure defects and lattice strain, thereby improving the electrochemical performance of single crystal positive electrode materials.
  • the sintering reaction time is 10 h to 30 h, specifically 10 h, 12 h, 15 h, 16 h, 18 h, 20 h, 24 h, 28 h or 30 h, etc.
  • 10 h to 30 h specifically 10 h, 12 h, 15 h, 16 h, 18 h, 20 h, 24 h, 28 h or 30 h, etc.
  • it can also be other values within the above range, which is not limited here.
  • an embodiment of the present application provides a lithium-ion battery, wherein the lithium-ion battery comprises a positive electrode material prepared by the single crystal positive electrode material described in the first aspect or the single crystal positive electrode material preparation method described in the third aspect.
  • the total metal concentration in the mixed solution was controlled to be 300 g/L.
  • the mixed solution was placed in a reactor with ultrasonic stirring function and heated to 60°C.
  • the ultrasonic stirring frequency was adjusted to 33 kHz. After ultrasonic stirring in the reactor for 1 hour, the heating function was turned off and polyethylene glycol accounting for 1% of the total mass of the mixed solution was added.
  • the mixture was ultrasonically stirred for another 0.5 hour.
  • the content of SO42- was 900 ppm based on the total mass of Ni, Co and Mn elements.
  • the mixed solution After the mixed solution is atomized into droplets, it is placed in an air atmosphere in a roasting furnace for thermal decomposition at 650° C.; the flow rate of the mixed solution is controlled to be 200 L/h and the atomization pressure is controlled to be 0.6 MPa.
  • the thermal decomposition product is subjected to air flow pulverization to obtain a positive electrode material precursor (Ni 0.67 Co 0.05 Mn 0.28 O).
  • the single crystal positive electrode material prepared in this embodiment has a general chemical formula of LiNi 0.67 Co 0.05 Mn 0.28 O 2 , an average particle size D 50 of 3.8 ⁇ m, and a tap density of 1.95 g/cm 3 .
  • Figure 1 is a SEM morphology image of the positive electrode material precursor prepared in Example 1 of the present application
  • Figure 2 is another SEM morphology image of the positive electrode material precursor prepared in Example 1 of the present application.
  • the positive electrode material precursor includes secondary particles, and the secondary particles include multiple agglomerated primary particles.
  • the cathode material precursor prepared in Example 1 of the present application When observing the cathode material precursor prepared in Example 1 of the present application with a scanning electron microscope, 10 points of the cathode material precursor were randomly selected for EDS point scanning to test the Ni, Co, and Mn contents at a magnification of 3K.
  • the range of the Ni content in the cathode material precursor is 0.095, and the standard deviation is 0.036; the range of the Co content is 0.029, and the standard deviation is 0.009; the range of the Mn content is 0.081, and the standard deviation is 0.030.
  • the cathode material precursor prepared in Example 1 has good distribution uniformity of Ni, Co, and Mn.
  • the content of free SO4 2- on the surface of the precursor was 504ppm as detected by ion chromatography.
  • FIG4 is a Williamsone-Hall analysis fitting curve of the single crystal positive electrode material prepared in Example 1 of the present application. As shown in FIG4, by analyzing and calculating the data in FIG4, it can be obtained that the lattice strain of the single crystal positive electrode material is 0.11%. Other performance parameters of the positive electrode material precursor and the single crystal positive electrode material are detailed in Table 1 and Table 2.
  • Example 2 The difference from Example 1 is that (2) after the mixed solution is atomized into droplets, it is placed in an air atmosphere in a roasting furnace for thermal decomposition at 750°C; the flow rate of the mixed solution is controlled to be 200L/h and the atomization pressure is 0.6MPa.
  • the single crystal positive electrode material prepared in this embodiment has a general chemical formula of LiNi 0.67 Co 0.05 Mn 0.28 O 2 , an average particle size D50 of the single crystal positive electrode material is 3.7 ⁇ m, and a tap density of 1.85 g/cm 3 .
  • Example 2 The difference from Example 1 is that (2) after the mixed solution is atomized into droplets, it is placed in an air atmosphere in a roasting furnace for thermal decomposition at 650° C.; the flow rate of the mixed solution is controlled to be 100 L/h and the atomization pressure is 0.6 MPa.
  • the single crystal positive electrode material prepared in this embodiment has a general chemical formula of LiNi 0.67 Co 0.05 Mn 0.28 O 2 , an average particle size D50 of the single crystal positive electrode material is 4.0 ⁇ m, and a tap density of 2.12 g/cm 3 .
  • Example 2 The difference from Example 1 is that (2) after the mixed solution is atomized into droplets, it is placed in an air atmosphere in a roasting furnace for thermal decomposition at 500°C; the flow rate of the mixed solution is controlled to be 500L/h and the atomization pressure is 0.6MPa.
  • the single crystal positive electrode material prepared in this embodiment has a general chemical formula of LiNi 0.67 Co 0.05 Mn 0.28 O 2 , an average particle size D50 of the single crystal positive electrode material is 3.8 ⁇ m, and a tap density of 1.90 g/cm 3 .
  • the single crystal positive electrode material prepared in this embodiment has a general chemical formula of LiNi 0.67 Co 0.05 Mn 0.28 O 2 , an average particle size D50 of the single crystal positive electrode material is 4.5 ⁇ m, and a tap density of 2.2 g/cm 3 .
  • the single crystal positive electrode material prepared in this embodiment has a general chemical formula of LiNi 0.67 Co 0.05 Mn 0.28 O 2 , an average particle size D50 of 3.0 ⁇ m, and a tap density of 1.68 g/cm 3 .
  • the total metal concentration in the mixed solution was controlled to be 300 g/L.
  • the content of SO42- was ⁇ 1780 ppm based on the total mass of Ni, Co and Mn elements.
  • the mixed solution After the mixed solution is atomized into droplets, it is placed in a calcining furnace under air atmosphere and thermally decomposed at 600° C.; the flow rate of the mixed solution is controlled to be 200 L/h and the atomization pressure is controlled to be 0.6 MPa.
  • the single crystal positive electrode material prepared in this embodiment has a general chemical formula of LiNi 0.88 Co 0.06 Mn 0.04 O 2 , an average particle size D50 of the single crystal positive electrode material is 3.2 ⁇ m, and a tap density of 1.77 g/cm 3 .
  • the total metal concentration in the mixed solution was controlled to be 300 g/L.
  • the mixed solution After the mixed solution is atomized into droplets, it is placed in a calcining furnace under air atmosphere and thermally decomposed at 600° C.; the flow rate of the mixed solution is controlled to be 200 L/h and the atomization pressure is controlled to be 0.6 MPa.
  • the thermal decomposition product is subjected to air flow pulverization to obtain a positive electrode material precursor (Ni 0.88 Co 0.06 Mn 0.03 Al 0.03 O).
  • the single crystal positive electrode material prepared in this embodiment has a general chemical formula of LiNi 0.88 Co 0.06 Mn 0.03 Al 0.03 O 2 , an average particle size D50 of 3.2 ⁇ m, and a tap density of 1.78 g/cm 3 .
  • Example 2 The difference from Example 1 is that (1) based on the total mass of Ni, Co, and Mn elements, the content of SO4 2- is 200ppm. Through ion chromatography detection, the content of free SO4 2- on the surface of the precursor prepared in this example is 100ppm.
  • the single crystal positive electrode material prepared in this example has a chemical formula of LiNi 0.67 Co 0.05 Mn 0.28 O 2 , an average particle size D 50 of the single crystal positive electrode material is 3.8 ⁇ m, and a tap density of 1.95g/cm 3 .
  • Other performance parameters of the positive electrode material precursor and the single crystal positive electrode material are detailed in Table 1 and Table 2.
  • the single crystal positive electrode material prepared in this embodiment has a chemical formula of LiNi 0.67 Co 0.05 Mn 0.28 O 2 , an average particle size D50 of 3.8 ⁇ m, and a tap density of 1.83 g/cm 3 .
  • the performance parameters are detailed in Table 1 and Table 2.
  • the single crystal positive electrode material prepared in this embodiment has a chemical formula of LiNi 0.67 Co 0.05 Mn 0.28 O 2 , an average particle size D50 of 4.1 ⁇ m, and a tap density of 1.82 g/cm 3 .
  • Other performance parameters of the positive electrode material precursor and the single crystal positive electrode material are shown in Tables 1 and 2.
  • Example 2 The difference from Example 1 is that (2) after the mixed solution is atomized into droplets, it is placed in an air atmosphere in a roasting furnace for thermal decomposition at 880°C; the flow rate of the mixed solution is controlled to be 200L/h and the atomization pressure is 0.6MPa.
  • the single crystal positive electrode material prepared in this comparative example has a general chemical formula of LiNi 0.67 Co 0.05 Mn 0.28 O 2 , an average particle size D50 of the positive electrode material is 3.82 ⁇ m, and a tap density of 1.86 g/cm 3 .
  • Example 2 The difference from Example 1 is that (2) after the mixed solution is atomized into droplets, it is placed in an air atmosphere in a roasting furnace for thermal decomposition at 650°C; the flow rate of the mixed solution is controlled to be 1000L/h and the atomization pressure is 0.6MPa.
  • the single crystal positive electrode material prepared in this comparative example has a general chemical formula of LiNi 0.67 Co 0.05 Mn 0.28 O 2 , an average particle size D50 of the single crystal positive electrode material is 3.72 ⁇ m, and a tap density of 1.90 g/cm 3 .
  • the positive electrode material prepared in this comparative example is a polycrystalline positive electrode material, and its general chemical formula is LiNi 0.67 Co 0.05 Mn 0.28 O 2 .
  • the average particle size D50 of the polycrystalline positive electrode material is 3.2 ⁇ m, and the tap density is 1.8 g/cm 3 .
  • Example 2 of CN113488642A to prepare Ni 0.88 Co 0.06 Mn 0.03 Al 0.03 (OH) 2 quaternary precursor and corresponding positive electrode materials.
  • (1) preparing a first solution: nickel sulfate hexahydrate, manganese sulfate monohydrate, and cobalt sulfate heptahydrate were weighed according to a molar ratio of nickel:cobalt:manganese 0.88:0.06:0.03, and dissolved in deionized water to prepare a transition metal salt solution with a mass concentration of 2 mol/L, referred to as the first solution;
  • hydroxide precursor and lithium hydroxide were uniformly mixed in a molar ratio of 1:1.05, sintered at 500°C for 3 h and 850°C for 15 h in an oxygen atmosphere, and after cooling, the product was crushed and sieved to a D50 of 12 ⁇ m to obtain a single crystal positive electrode material LiNi 0.88 Co 0.06 Mn 0.03 Al 0.03 O 2 .
  • Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 precursor and corresponding positive electrode materials Refer to CN116230922A to prepare Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 precursor and corresponding positive electrode materials.
  • NiSO 4 , CoSO 4 , and MnSO 4 were mixed in a Ni/Co/Mn molar ratio of 0.8:0.1:0.1 to prepare a solution.
  • Example 1 The difference from Example 1 is that (1) based on the total mass of Ni, Co and Mn elements, the content of SO4 2- is 2000 ppm.
  • the content of free SO4 2- on the surface of the precursor prepared in this embodiment is 1200ppm.
  • the single crystal positive electrode material prepared in this embodiment has a chemical formula of LiNi 0.67 Co 0.05 Mn 0.28 O 2 , an average particle size D 50 of 3.8 ⁇ m, and a tap density of 1.95 g/cm 3 .
  • Other performance parameters of the positive electrode material precursor and the single crystal positive electrode material are shown in Table 1 and Table 2.
  • an energy dispersive X-ray spectrometer (EDS) attached to a scanning electron microscope was used to randomly select 10 points on the surface of an untreated cathode material precursor or a single crystal cathode material to scan and test the Ni, Co, and Mn contents of the cathode material precursor or the single crystal cathode material.
  • the standard deviation and range of the mass content of each element Ni, Co, and Mn were statistically analyzed to characterize the uniformity of the distribution of Ni, Co, and Mn elements.
  • the surface area weighted average particle size D[3, 2] of the cathode material precursor was obtained by using a Malvern 3000 laser particle size analyzer.
  • the specific method is: use Japan Rigaku X-ray diffractometer to measure, specific conditions: 0.75 degrees / minute, step size 0.02, continuous scanning within the 2 ⁇ range of 10 to 90 degrees.
  • a curve is drawn and linearly fitted, and the strain ⁇ and grain size D can be calculated by the slope and intercept.
  • ⁇ total is the half-width value of the actual test
  • ⁇ instrument is the half-width widening caused by the instrument.
  • This value can be obtained by XRD calculation of testing standard silicon wafers.
  • the ⁇ instrument of the test equipment is 0.000103.
  • the data of the seven strong diffraction peaks (003), (101), (102), (104), (015), (107), and (113) are selected for fitting to improve the degree of linear fitting and reduce the actual test error.
  • ⁇ is the half-peak width, ⁇ is the diffraction angle, both in radians; k is a constant, which is 0.89; ⁇ is the X-ray wavelength, which is 0.154nm; D is the grain size, in nm; ⁇ is the lattice strain, which is dimensionless.
  • the electrochemical performance of the material was evaluated using a button half-cell.
  • the specific steps were as follows: single crystal positive electrode material, conductive carbon black, and PVDF were weighed in a mass ratio of 93:5:2, N-methyl-2-pyrrolidone (NMP) was added at a solid content of 50%, and a high-speed disperser was used to adjust the viscous slurry.
  • NMP N-methyl-2-pyrrolidone
  • the slurry was evenly coated on aluminum foil with a scraper, dried in an oven at 80°C, rolled, and cut into positive electrode sheets with a diameter of 14 mm.
  • a 16 mm lithium sheet was used as the negative electrode sheet, a Celgard polypropylene film was used as the diaphragm, and a carbonate solution of LiPF6 with a concentration of 1 mol/L was used as the electrolyte.
  • the assembly was performed in an argon-filled glove box to obtain a button half-cell.
  • the capacity and cycle performance tests were performed at 25°C and 3.0-4.3V using the LAND battery test system, and the nominal capacity 1C was set to 200 mAh/g.
  • the cathode material sample was first embedded in a carbon paint (PELCO) graphite block, and then the cross section of the block was polished with an argon ion beam.
  • Electron backscatter diffraction (EBSD) imaging was performed using a JEOL JSM-7000F scanning electron microscope. The step size of the EBSD image was set to 250nm (each pixel was 250nm ⁇ 250nm).
  • the standard deviation of the mass content of each element Ni, Co and Mn in the single crystal positive electrode materials prepared in Examples 1 to 8 is ⁇ 0.03, and the range of the mass content of each element Ni, Co and Mn is ⁇ 0.08, indicating that the distribution uniformity of Ni, Co and Mn elements inside the single crystal positive electrode material is good, which is conducive to reducing the crystal structure defects of the single crystal positive electrode material;
  • the lattice strain ⁇ of the single crystal positive electrode material is less than 0.2%, which can reduce the diffusion energy barrier of lithium ions between crystallites and increase the Li ion diffusion coefficient, so that the single crystal positive electrode material exhibits good rate performance and low DCR; at the same time, low lattice strain can also inhibit the generation of microcracks in the single crystal positive electrode material, thereby improving the cycle performance of the single crystal positive electrode material.
  • the single crystal positive electrode material prepared in Example 1 has the best comprehensive performance.
  • the single crystal positive electrode material of Example 1 exhibits good rate performance, lower impedance, and higher cycle performance. This is because when the positive electrode material precursor is prepared in Example 1, the temperature of the atomized mixed solution for thermal decomposition is appropriate, so that the surface area weighted average particle size D[3,2] of the positive electrode material precursor is low, the positive electrode material precursor has high reactivity, the crystal structure defects of the single crystal positive electrode material are reduced, and the lattice strain of the single crystal positive electrode material is low. Therefore, the single crystal positive electrode material prepared in Example 1 exhibits better rate performance, lower impedance, and better cycle performance.
  • Example 5 Compared with Example 1, in Example 5, during the sintering process of the cathode material precursor and the lithium source, the sintering temperature is increased, the range and standard deviation of the mass content of each element of Ni, Co and Mn in the single crystal cathode material are lower, and the lattice strain ⁇ of the single crystal cathode material is reduced, so the cycle performance is improved. However, since the grain size of the single crystal cathode material is significantly larger and the Li ion diffusion path is longer, the rate performance of the single crystal cathode material prepared in Example 5 is lower than that in Example 1.
  • Example 6 Compared with Example 1, in Example 6, during the sintering process of the positive electrode material precursor and the lithium source, the sintering temperature is reduced, which makes the grain size of the single crystal positive electrode material smaller and the lattice strain ⁇ increases. Therefore, the cycle stability of the single crystal positive electrode material of Example 6 is lower than that of the single crystal positive electrode material of Example 1.
  • Example 9 Compared with Example 1, the free SO 4 2- content of the precursor and the positive electrode material in Example 9 is reduced, showing better rate and cycle performance.
  • Example 10 does not perform ultrasonic stirring before atomizing the single crystal positive electrode material precursor mixed liquid, and the range and standard deviation of the mass content of each element Ni, Co and Mn in the single crystal positive electrode precursor are higher, which affects its circulation and internal resistance.
  • Example 11 Compared with Example 1, in Example 11, polyethylene glycol is not added for ultrasonic stirring before the single crystal positive electrode material precursor mixed liquid is atomized, and the surface area weighted average particle size D[3, 2] of the single crystal positive electrode material is relatively large, and large agglomerated particles may appear. In addition, the range and standard deviation of the mass content of each element Ni, Co and Mn in the single crystal positive electrode precursor are higher, which affects its circulation and internal resistance.
  • Example 1 Compared with Example 1, the free SO4 2- in the positive electrode material of Comparative Example 6 exceeds 1000 ppm. Excessive SO4 2- leads to deterioration of the material capacity, rate and cycle performance.
  • Comparative Example 1 increases the thermal decomposition temperature of the positive electrode material precursor during the preparation process, so that the surface area weighted average particle size D[3, 2] of the positive electrode material precursor is greater than 2.0 ⁇ m; the positive electrode material precursor has poor reactivity, resulting in more defects in the subsequently prepared single crystal positive electrode material, and the lattice strain ⁇ exceeds 0.2%, so that the single crystal positive electrode material exhibits poor rate performance, high DCR and low cycle performance.
  • Example 1 Compared with Example 1, the atomization flow rate is increased during the preparation of the precursor of the positive electrode material of Comparative Example 2, and the standard deviation and variance of the mass content of each element Ni, Co and Mn in the prepared positive electrode material precursor are significantly increased, resulting in a decrease in the distribution uniformity of Ni, Co and Mn elements in the prepared single crystal positive electrode material, an increase in the lattice strain, and the lattice strain ⁇ exceeds 0.2%. Therefore, the rate performance and cycle performance of the single crystal positive electrode material prepared in Comparative Example 2 are reduced.
  • the sintering temperature of the positive electrode material in Comparative Example 3 is too low during the sintering of the precursor and the lithium source, and the obtained positive electrode material is a polycrystalline structure.
  • the grain size of the positive electrode material is less than 150nm, and it has good rate performance; but the lattice strain exceeds 0.2%, and it is easy to crack and pulverize during the cycle process, which reduces the structural stability of the positive electrode material and causes a significant attenuation of the cycle capacity of the positive electrode material.
  • Example 1 Compared with Example 1, the standard deviation and variance of the mass content of each element Ni, Co and Mn in the positive electrode material precursor of Comparative Example 4 are significantly greater than those of Example 1. Therefore, the lattice strain of the prepared single crystal positive electrode material is significantly increased, and the lattice strain exceeds 0.2%, resulting in a significant decrease in the rate performance and cycle performance of the single crystal positive electrode material.
  • the surface area weighted average particle size D[3, 2] of the positive electrode material precursor is too large, and the standard deviation and variance of the mass content of each element Ni, Co and Mn in the positive electrode material precursor are significantly greater than those in Example 1. Therefore, the lattice strain of the prepared single crystal positive electrode material is significantly increased, and the lattice strain exceeds 0.2%, which leads to a significant decrease in the rate performance and cycle performance of the positive electrode material.

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Abstract

一种正极材料前驱体、单晶正极材料及制备方法、锂离子电池，单晶正极材料的化学通式为Li xNi aCo bMn cN dO 2，其中，0.98≤x≤1.1，0.50≤a≤0.98，0＜b≤0.20，0＜c≤0.30，0≤d≤0.10，a+b+c+d＝1，N包括Al、Ti、Zr、Mg、Sr、Ba、Ca、Nb、W、Sb、Ta、Sn和Y中的至少一种；单晶正极材料中Ni、Co和Mn每种元素的质量含量的标准差均≤0.03；晶格应变ε＜0.2％。所述单晶正极材料，其晶格应变低，能够降低锂离子在微晶之间的扩散能垒，使得材料表现出较低的DCR，倍率性能好；还能抑制微裂纹的产生，提升材料的循环性能。

Description

正极材料前驱体、单晶正极材料及制备方法、锂离子电池
相关申请的交叉引用
本申请要求在2023年10月13日提交中国专利局、申请号为“202311331910.3”，申请名称为“正极材料前驱体、单晶正极材料及制备方法、锂离子电池”中国专利申请的优先权，全部内容通过引用结合在本申请中。
技术领域
本申请涉及正极材料技术领域，尤其涉及正极材料前驱体、单晶正极材料及制备方法、锂离子电池。
背景技术
锂离子正极材料主要分为磷酸铁锂和三元材料。磷酸铁锂因成本、循环寿命和热稳定性优于三元材料，适合于商用车、中低端乘用车、储能等领域。三元材料能量密度高，低温性能好，适合于中高端乘用车。
传统的多晶三元正极材料由一次颗粒(几百纳米)紧密团聚成球形二次颗粒(粒径通常＞10μm)所组成，在充放电过程中，随着晶格的收缩，容易沿晶界产生局部应力，造成材料结构塌缩，形成微裂纹，使正极材料容量快速衰减。单晶化是提高三元材料循环性能的一种方法。单晶三元材料由分散的一次颗粒组成(颗粒粒径一般在几微米，且绝大多数颗粒为取向相同的单个晶粒)，没有二次球形颗粒存在。由于消除了晶界，能够抑制正极材料在充放电过程中的开裂，表现出优异的稳定性。然而单晶三元材料也面临其他问题。单晶三元材料Li的扩散路径长，导致Li传输动力缓慢，性能上表现为直流内阻(DCR)大、倍率性能差。此外，尽管单晶颗粒能够抑制颗粒开裂，但是循环过程中依然会出现晶面滑移、错位等现象，进一步产生微裂纹。
三元单晶正极材料一般是由含Ni/Co/Mn的前驱体化合物和锂盐通过高温烧结而制备。烧结过程中，正极材料的形成通常是很缓慢的，且生长速度不均匀，导致所形成的正极材料内部存在应力集中；此外，受离子扩散的限制，三元材料中元素的分布存在浓度差异，使材料内部晶格参数不匹配。这一方面会阻碍锂离子的传输，从而增加正极材料的阻抗，降低正极材料的倍率性能；另一方面，内部晶格微应力使正极材料在循环的过程中开裂、粉化，降低正极材料的循环性能。
因此如何提升单晶正极材料的倍率性能、降低阻抗、并进一步提升循环性能是目前仍需解决的技术问题。
发明内容
本申请的目的在于提供正极材料前驱体、单晶正极材料及制备方法、锂离子电池，本申请提供的单晶正极材料，其晶格应变低，能够降低锂离子在微晶之间的扩散能垒，提升Li离子扩散系数，从而使得单晶正极材料表现出较低的DCR，单晶正极材料的倍率性能好；还可以减少出现晶面滑移、错位等现象，从而抑制微裂纹的产生，提高单晶正极材料的结构稳定 性，进而提升单晶正极材料的循环性能。
第一方面，本申请实施例提供了一种单晶正极材料，所述单晶正极材料的化学通式为LixNiaCobMncNdO2，其中，0.98≤x≤1.1，0.50≤a≤0.98，0＜b≤0.20，0＜c≤0.30，0≤d≤0.10，a+b+c+d＝1，N包括Al、Ti、Zr、Mg、Sr、Ba、Ca、Nb、W、Sb、Ta、Sn和Y中的至少一种；
在用扫描电子显微镜观察所述单晶正极材料的情况下，在3K放大倍数下，对所述单晶正极材料随机选取10个点进行EDS点扫描测试Ni、Co、Mn含量，在所述单晶正极材料的EDS谱图结果中，所述单晶正极材料中Ni、Co和Mn每种元素的质量含量的标准差均≤0.03；
所述单晶正极材料的晶格应变为ε，且ε＜0.2％。
在一些实施方式中，单晶正极材料中包括SO4 2-，SO4 2-的含量为δ，其中，0ppm≤δ≤800ppm。
在一些实施方式中，单晶正极材料含有至少一个取向相同的单个晶粒，其中，单个晶粒的平均粒径为1μm～5μm。
在一些实施方式中，所述单晶正极材料的晶粒尺寸为D，150nm＜D＜250nm。
在一些实施方式中，所述单晶正极材料的平均粒径D50为1.5μm～5μm。
在一些实施方式中，所述单晶正极材料的百特振实密度＞1.5g/cm3。
在一些实施方式中，所述单晶正极材料中Ni、Co和Mn每种元素的质量含量的极差均≤0.08。
第二方面，本申请实施例提供了一种正极材料前驱体，所述正极材料前驱体的化学通式为NiaCobMncNdOe，其中，0.50≤a≤0.98，0＜b≤0.20，0＜c≤0.30，0≤d≤0.10，a+b+c+d＝1，1≤e≤1.15，N包括Al、Ti、Zr、Mg、Sr、Ba、Ca、Nb、W、Sb、Ta、Sn和Y中的至少一种；
所述正极材料前驱体的表面积加权平均粒径D[3，2]＜2.0μm，所述正极材料前驱体中Ni、Co和Mn每种元素的质量含量的标准差均≤0.05。
在一些实施方式中，所述正极材料前驱体中Ni、Co和Mn每种元素的质量含量的极差均≤0.12。
在一些实施方式中，所述正极材料前驱体包括二次颗粒，所述二次颗粒包括多个团聚的一次颗粒。
在一些实施方式中，所述正极材料前驱体包括二次颗粒，所述二次颗粒包括多个团聚的一次颗粒，所述一次颗粒呈球状。
在一些实施方式中，所述正极材料前驱体包括二次颗粒，所述二次颗粒包括多个团聚的一次颗粒，所述一次颗粒的粒径为20nm～1000nm。
在一些实施方式中，所述正极材料前驱体的平均粒径D50＜3.5μm。
在一些实施方式中，所述正极材料前驱体的比表面积＞5m2/g。
在一些实施方式中，所述正极材料前驱体的百特振实密度＞1g/cm3。
第三方面，本申请实施例提供了一种单晶正极材料的制备方法，包括以下步骤：
将含有镍盐、钴盐和锰盐的混合溶液进行雾化处理后，进行热分解，得到正极材料前驱体，所述正极材料前驱体的表面积加权平均粒径D[3，2]＜2.0μm，所述正极材料前驱体中Ni、Co和Mn每种元素的质量含量的标准差均≤0.05；将所述正极材料前驱体与锂源混合后，置于含氧气氛下进行烧结，得到单晶正极材料，所述单晶正极材料中Ni、Co和Mn每种元素的质量含量的标准差均≤0.03；所述单晶正极材料的晶格应变为ε，且ε＜0.2％。
在一些实施方式中，正极材料前驱体中包括SO4 2-，所述SO4 2-的含量为η，其中，0ppm≤η≤1800ppm。
在一些实施方式中，所述镍盐包括氯化镍、硫酸镍、硝酸镍、碳酸镍、草酸镍和醋酸镍中的至少一种。
在一些实施方式中，所述钴盐包括氯化钴、草酸钴、碳酸钴、硫酸钴、硝酸钴和醋酸钴中的至少一种。
在一些实施方式中，所述锰盐包括氯化锰、碳酸锰、硫酸锰、草酸锰、硝酸锰和醋酸锰中的至少一种。
在一些实施方式中，所述混合溶液中Ni、Co与Mn的摩尔比为(50～98)：(0～20)：(0～30)，且所述混合溶液中Co与Mn的含量不为0。
在一些实施方式中，所述混合溶液中总的金属浓度为200g/L～500g/L。
在一些实施方式中，所述混合溶液还包括含N元素的掺杂剂，N包括Al、Ti、Zr、Mg、Sr、Ba、Ca、Nb、W、Sb、Ta、Sn和Y中的至少一种。
在一些实施方式中，所述正极材料前驱体的化学通式为NiaCobMncNdOe，其中，0.50≤a≤0.98，0＜b≤0.20，0＜c≤0.30，0≤d≤0.10，a+b+c+d＝1，1≤e≤1.15，N包括Al、Ti、Zr、Mg、Sr、Ba、Ca、Nb、W、Sb、Ta、Sn和Y中的至少一种。
在一些实施方式中，所述正极材料前驱体中Ni、Co和Mn每种元素的质量含量的极差均≤0.12。
在一些实施方式中，所述混合溶液的流量为100L/h～900L/h。
在一些实施方式中，所述雾化处理的压力为0.4MPa～0.8MPa。
在一些实施方式中，所述一次烧结的温度为500℃～850℃。
在一些实施方式中，所述锂源包括碳酸锂、氢氧化锂、乙酸锂、硫酸锂、氯化锂、硝酸锂及草酸锂中的至少一种。
在一些实施方式中，所述锂源中的锂与所述正极材料前驱体中的镍、钴和锰总和的摩尔比为0.98～1.10。
在一些实施方式中，所述烧结的温度为750℃～950℃。
在一些实施方式中，所述烧结的时间为10h～30h。
第四方面，本申请实施例提供了一种锂离子电池，所述锂离子电池包括第一方面所述的单晶正极材料或第三方面所述的单晶正极材料的制备方法制备得到的单晶正极材料。
与现有技术相比，本申请的技术方案至少具有以下有益效果：
本申请提供的单晶正极材料，对单晶正极材料随机选取10个点进行EDS点扫描测试Ni、Co、Mn含量，在单晶正极材料的EDS谱图结果中，单晶正极材料中Ni、Co和Mn每种元素的质量含量的标准差均≤0.03，说明单晶正极材料内部Ni、Co、Mn元素分布均匀性较好，这有利于减少单晶正极材料的晶体结构缺陷；单晶正极材料的晶格应变ε＜0.2％，这能够降低锂离子在微晶之间的扩散能垒，提升Li离子扩散系数，使得单晶正极材料表现出良好的倍率性能、较低的DCR；同时，晶格应变低还可以抑制单晶正极材料内微裂纹的产生，进而提升单晶正极材料的循环性能。
本申请提供的正极材料前驱体，该正极材料前驱体的表面积加权平均粒径D[3，2]＜2.0μm，反应活性高，有利于提高正极材料前驱体后续制备正极材料过程中的反应效率和传质效率；同时，上述制备方法得到的正极材料前驱体中Ni、Co和Mn每种元素的质量含量的标准差均≤0.05，说明正极材料前驱体中Ni、Co、Mn元素分布均匀性较好；利用该正极材料前驱体 制备正极材料，可以提高正极材料中Ni、Co、Mn元素的分布均匀性，使得通过该正极材料前驱体制备的正极材料晶体结构缺陷少，晶格应力小。
本申请提供的单晶正极材料制备方法，通过将含有镍盐、钴盐和锰盐的混合溶液进行雾化处理后，进行热分解后得到正极材料前驱体。该正极材料前驱体的表面积加权平均粒径D[3，2]＜2.0μm，反应活性高，有利于提高正极材料前驱体和锂源在后续高温烧结过程中的反应效率和传质效率；同时，上述制备方法得到的正极材料前驱体中Ni、Co和Mn每种元素的质量含量的标准差均≤0.05，说明正极材料前驱体中Ni、Co、Mn分布均匀性较好；进而上述正极材料前驱体在后续与锂源进行烧结所制备的单晶正极材料中Ni、Co和Mn每种元素的质量含量的标准差均≤0.03，单晶正极材料内部Ni、Co、Mn元素分布均匀性好，这有利于减少单晶正极材料的晶体结构缺陷；且单晶正极材料的晶格应变低，其晶格应变ε＜0.2％，能够降低锂离子在微晶之间的扩散能垒，提升Li离子扩散系数，使得单晶正极材料表现出良好的倍率性能、较低的DCR；同时，晶格应变低还可以抑制单晶正极材料内微裂纹的产生，进而提升单晶正极材料的循环性能。
附图说明
下面结合附图和实施例对本申请进一步说明。
图1为本申请实施例1制备的正极材料前驱体的SEM形貌图；
图2为本申请实施例1制备的正极材料前驱体的另一SEM形貌图；
图3为本申请实施例1制备的正极材料前驱体的EDS谱图结果；
图4为本申请实施例1制备的单晶正极材料的Williamsone-Hall分析拟合曲线。
具体实施方式
为了更好的理解本申请的技术方案，下面结合附图对本申请实施例进行详细描述。
应当明确，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其它实施例，都属于本申请保护的范围。
在本申请实施例中使用的术语是仅仅出于描述特定实施例的目的，而非旨在限制本申请。在本申请实施例和所附权利要求书中所使用的单数形式的“一种”、“所述”和“该”也旨在包括多数形式，除非上下文清楚地表示其它含义。
应当理解，本文中使用的术语“和/或”仅仅是一种描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。另外，本文中字符“/”，一般表示前后关联对象是一种“或”的关系。
第一方面，本申请实施例提供了一种单晶正极材料，所述单晶正极材料的化学通式为LixNiaCobMncNdO2，其中，0.98≤x≤1.1，0.50≤a≤0.98，0＜b≤0.20，0＜c≤0.30，0≤d≤0.10，a+b+c+d＝1，N包括Al、Ti、Zr、Mg、Sr、Ba、Ca、Nb、W、Sb、Ta、Sn和Y中的至少一种；
在用扫描电子显微镜观察所述单晶正极材料的情况下，在3K放大倍数下，对所述单晶正极材料随机选取10个点进行EDS点扫描测试Ni、Co、Mn含量，在所述单晶正极材料的EDS谱图结果中，所述单晶正极材料中Ni、Co和Mn每种元素的质量含量的标准差均≤0.03；
所述单晶正极材料的晶格应变为ε，且ε＜0.2％。
本申请提供的单晶正极材料，对单晶正极材料随机选取10个点进行EDS点扫描测试Ni、Co、Mn含量，在单晶正极材料的EDS谱图结果中，单晶正极材料中Ni、Co和Mn每种元素的质量含量的标准差均≤0.03，说明单晶正极材料内部Ni、Co、Mn元素分布均匀性较好，这有利于减少单晶正极材料的晶体结构缺陷；单晶正极材料的晶格应变ε＜0.2％，这能够降低锂离子在微晶之间的扩散能垒，提升Li离子扩散系数，使得单晶正极材料表现出良好的倍率性能、较低的DCR；同时，晶格应变低还可以抑制单晶正极材料内微裂纹的产生，进而提升单晶正极材料的循环性能。
具体地，x的取值可以是0.98、0.99、1.0、1.01、1.03、1.05、1.08、1.09或1.1等，在此不做限定。
a的取值具体可以是0.50、0.55、0.60、0.63、0.70、0.75、0.80、0.85、0.88、0.90、0.95或0.98等；b的取值可以是0.01、0.05、0.08、0.10、0.11、0.13、0.15、0.18或0.20等；c的取值可以是0.01、0.05、0.10、0.15、0.18、0.20、0.23、0.27或0.30等；d的取值可以是0、0.01、0.03、0.05、0.06、0.07、0.08、0.09或0.10等，在此不做限定。
具体地，单晶正极材料中Ni、Co和Mn每种元素的质量含量的标准差可以是0.01、0.015、0.02、0.025、0.026、0.028或0.03等，在此不做限定。
在一些实施方式中，所述单晶正极材料中Ni、Co和Mn每种元素的质量含量的极差均≤0.08，具体可以是0.01、0.02、0.028、0.03、0.05、0.057、0.06、0.07、0.075或0.08等，当然也还可以是上述范围内其他值，在此不做限定。
可以理解地，单晶正极材料中Ni、Co和Mn每种元素的质量含量的标准差和极差越低，则单晶正极材料中Ni、Co、Mn元素的分布均匀程度越高。本申请中单晶正极材料中Ni、Co和Mn每种元素的质量含量的标准差和极差在上述范围内，说明本申请的单晶正极材料中Ni、Co、Mn元素分布均匀，有利于减少单晶正极材料的晶格缺陷，降低晶格应力，提升单晶正极材料的循环性能和倍率性能。
单晶正极材料的晶格应变具体可以是0.01％、0.03％、0.05％、0.08％、0.10％、0.11％、0.12％、0.15％、0.18％或0.19％等，在此不做限定。
在一些实施方式中，所述单晶正极材料还包括包覆层，包覆层包括金属氧化物或锂离子导体，其中，金属氧化物中的金属包括Al、Ti、Zr、Y、Nb、Mg、W、B、Ce、Co和Mn中的至少一种。包覆层可以减少单晶正极材料与电解液之间的直接接触，减少材料与电解液之间副反应的发生，进一步提升单晶正极材料的电化学性能。
在一些实施方式中，所述单晶正极材料表面游离的SO4 2-的含量小于等于1000ppm，优选≤800ppm。单晶正极材料的SO4 2-的含量具体可以是0ppm、5ppm、10ppm、50ppm、100ppm、200ppm、300ppm、400ppm、500ppm、600ppm、700ppm、800ppm、900ppm或1000ppm等。当游离SO4 2-含量在上述范围时，正极材料具有更好的倍率和循环性能。传统的三元前驱体材料由于制备过程中使用了NiSO4、CoSO4、MnSO4作为原料，共沉淀前驱体会残留较高含量的硫酸根离子。硫酸根离子很难分解，因此后续烧结形成的相应正极材料表面的硫酸根离子含量较高(通常＞1000ppm)。游离的硫酸根离子会对正极材料的电化学性能造成不利影响。当表面游离的SO4 2-含量较高时，SO4 2-与Li离子结合，束缚部分Li离子，造成材料容量和倍率恶化；此外，表面游离的SO4 2-也会影响SEI膜的稳定性。
单晶正极材料表面游离的SO4 2-含量与正极材料前驱体中表面游离的SO4 2-含量具有很强的继承性，正极材料前驱体中SO4 2-含量越高，单晶正极材料表面游离的SO4 2-含量越高。本申请 提供的正极材料前驱体表面游离的SO4 2-的含量≤1000ppm，更利于制备得到表面游离的SO4 2-的含量≤800ppm的正极材料。
为了降低单晶正极材料前驱体中SO4 2-的含量，在一些实施例中，Ni盐、Mn盐、Co盐和N盐各自独立地包括氯化盐、硝酸盐、草酸盐和醋酸盐中的至少一种。镍、钴、锰的硝酸盐、氯化盐、草酸盐、醋酸盐在高温下极易分解，不会存在明显残留，故对正极材料性能基本没有影响。通过控制金属盐混合溶液中SO4 2-的含量，甚至可以制备得到SO4 2-的含量接近于0的正极材料前驱体。但这会对原料的纯度要求较高，会造成原材料成本的上升。而采用含有SO4 2-杂质的三元回收料中的Ni源、Co源、Mn源以及N源作为金属源，通过控制金属源的中SO4 2-的含量来制备正极材料前驱体更为经济。
在一些实施例中，所述金属盐混合溶液中，以Ni元素、Co元素、Mn元素的总质量为基准计，SO4 2-的含量≤800ppm，进而更利于制备得到表面游离的SO4 2-含量较低的单晶正极材料，进一步提高单晶正极材料的容量和倍率性能。
在一些实施方式中，所述单晶正极材料含有至少一个取向相同的单个晶粒，其中，所述单个晶粒的平均粒径为1μm～5μm，如1μm、2μm、3μm、4μm、5μm等。
本申请的正极材料单晶颗粒为含有至少一个取向相同的单个晶粒，且满足上述条件的单个颗粒在EBSD测试下测量读取的平均粒径为1～5um的颗粒且。它能够稳定实现自身高度填充的同时，又能预防因颗粒达自身最密堆积后，颗粒因受到挤压等原因而导致裂纹的出现。颗粒具有相同的取向，能够使缓解正极颗粒在充放电循环过程的应力应变，大幅减少循环过程中颗粒的开裂，从而极大提升正极颗粒的结构稳定性。
需要说明的是，正极材料的晶粒取向至少可以通过电子背散射衍射(EBSD)测试，并随机选取100个取向相同的单个晶粒测量每个晶粒的粒径，取算数平均值则为上述单个晶粒的平均粒径。
单晶正极材料与多晶三元正极材料(即多晶二次颗粒)的区别在于，多晶二次颗粒最小颗粒为一次颗粒团聚形成的二次颗粒。而单晶正极材料，最小颗粒通常为微米级的单体一次颗粒。一般而言，除了EBSD测试手段外，还可以通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)等表征手段判定所得正极产物是否为单晶材料。对于常规的单晶正极材料，SEM也是重要、可靠的表征方式，单晶颗粒外形一般表现为规则或不规则多面体状，且无显著颗粒团聚。TEM是辅助性的第二表征方式，观察所得产物晶面取向是否一致，并结合选区电子衍射(SAED)进行进一步表征，上述手段均可用来判断是否为单晶正极材料。为了方便理解，本申请的单晶正极材料可以理解为含有至少一个取向相同的单个晶粒，并且上述单个晶粒的平均粒径为1μm-5μm的正极材料颗粒。
可以理解的，本申请中的单个晶粒可以是由一个一次颗粒组成的单个颗粒。上述单晶正极材料也可以存在少量由几个单颗粒粘连形成的“类二次颗粒”。“一次颗粒”是指通过扫描电子显微镜观察正极活性材料时识别出的最小颗粒单位，“二次颗粒”是指通过多个一次颗粒团聚形成的二次结构，呈现出较为圆润的球形形貌。“类二次颗粒”是指由几个单颗粒粘连形成，通常上述类二次颗粒中的单个颗粒的粒径通常在1um-5um之间，一般情况下“类二次颗粒”的颗粒圆润程度低于上述常规的“二次颗粒”。
需要特意说明的是，本领域技术人员所公知的“单晶正极材料”并非严格意义上的“单晶”。晶体学上，理想的单晶是指完全具有相同排列和方向的晶体。但是受限于杂质、应变和晶体缺陷，理想的单晶是非常罕见的，也很难在实验室中生产。因此，本领域所公知的单晶正极 材料实际上更多是“类单晶形貌”正极材料，其仅在尺寸上表现出类单晶的大颗粒尺寸，区别于由众多小一次颗粒组成的多晶。
在一些实施方式中，所述单晶正极材料的晶粒尺寸为D，150nm＜D＜250nm。单晶正极材料的晶粒尺寸具体可以是151nm、155nm、160nm、170nm、185nm、190nm、200nm、205nm、230nm或245nm等，在此不做限定。单晶正极材料的晶粒尺寸小于150nm，则单晶正极材料的循环稳定性较差；单晶正极材料的晶粒尺寸大于250nm，则单晶正极材料的容量和倍率性能较差。控制单晶正极材料的晶粒尺寸在上述范围内，有利于提升单晶正极材料的电化学性能。
需要说明的是，晶粒尺寸的计算方法一般是利用半峰宽通过Scherrer公式计算得到。该方法有个前提假设，即晶格应力为0，衍射峰的展宽完全是由晶粒尺寸所引起的。然而事实上，单晶正极材料内部的晶格应力是无法被完全忽略的，很多因素都使单晶正极材料内部出现应力集中，因此使用Scherrer公式计算得到的晶粒尺寸有其固有的局限性。本申请通过Williamsone-Hall方法，将由微晶大小引起的衍射峰宽化和晶格应力引起的衍射峰宽化分离，因此所计算出来的晶粒尺寸能够更好的反应材料的电化学性能。
在一些实施方式中，所述单晶正极材料的平均粒径D50为1.5μm～5μm，具体可以是1.5μm、1.8μm、2μm、2.5μm、3μm、3.5μm、4μm、4.5μm或5μm等，当然也还可以是上述范围内其他值，在此不做限定。将单晶正极材料的粒径控制在上述范围内，有利于提高单晶正极材料的结构稳定性、热稳定性和长循环稳定性。
在一些实施方式中，所述单晶正极材料的百特振实密度＞1.5g/cm3，具体可以是1.55g/cm3、1.58g/cm3、1.62g/cm3、1.63g/cm3、1.65g/cm3、1.70g/cm3或1.75g/cm3等，当然也还可以是上述范围内其他值，在此不做限定。单晶正极材料的振实密度控制在上述范围内时，有利于提高由该单晶正极材料制成的电池的能量密度。
在一些实施方式中，所述单晶正极材料的压实密度＞3.0g/cm3，具体可以是3.1g/cm3、3.2g/cm3、3.3g/cm3、3.5g/cm3、3.7g/cm3、3.9g/cm3或4.1g/cm3等，当然也还可以是上述范围内其他值，在此不做限定。
第二方面，本申请实施例提供了一种正极材料前驱体，所述正极材料前驱体的化学通式为NiaCobMncNdOe，其中，0.50≤a≤0.98，0＜b≤0.20，0＜c≤0.30，0≤d≤0.10，a+b+c+d＝1，1≤e≤1.15，N包括Al、Ti、Zr、Mg、Sr、Ba、Ca、Nb、W、Sb、Ta、Sn和Y中的至少一种；
所述正极材料前驱体的表面积加权平均粒径D[3，2]＜2.0μm，所述正极材料前驱体中Ni、Co和Mn每种元素的质量含量的标准差均≤0.05。
现有技术中，正极材料前驱体和锂盐的反应过程中，受离子扩散速度和温度梯度的限制，材料内部各微区晶体生长速度有差异，且晶胞参数有差异，这会造成材料内部积累晶格应力；晶格应力会增加Li离子在各晶面/晶界之间的扩散能垒，降低Li离子扩散系数，最终使材料的DCR增大。正极材料前驱体形貌和结构特征对正极材料而言具有很好的继承性，因此正极材料前驱体的组成和结构对最终正极材料的性能有直接影响。本申请提供的正极材料前驱体，该正极材料前驱体的表面积加权平均粒径D[3，2]＜2.0μm，反应活性高，有利于提高正极材料前驱体后续制备正极材料过程中的反应效率和传质效率；同时，上述制备方法得到的正极材料前驱体中Ni、Co和Mn每种元素的质量含量的标准差均≤0.05，说明正极材料前驱体中Ni、Co、Mn元素分布均匀性较好；利用该正极材料前驱体制备正极材料，可以提高正极材料中Ni、Co、Mn元素的分布均匀性，使得通过该正极材料前驱体制备的正极材料晶体结构 缺陷少，晶格应力小。
在一些实施例方式中，正极材料前驱体中包括SO4 2-，所述SO4 2-的含量为η，其中，0ppm≤η≤1800ppm。
可以理解的，前驱体表面的SO4 2-很难分解，也很难掺杂进入正极材料内部，因此正极材料表面游离的SO4 2-含量与前驱体中游离的SO4 2-含量可能存在一定的继承性，前驱体中SO4 2-含量越高，三元正极材料表面游离的SO4 2-含量越高。本申请提供的正极材料前驱体表面游离的SO4 2-的含量≤1800ppm，更利于制备得到表面游离的SO4 2-的含量≤800ppm的正极材料。为了降低正极材料前驱体中SO4 2-的含量，在一些实施例中，Ni盐、Mn盐、Co盐和N盐各自独立地包括氯化盐、硝酸盐、草酸盐和醋酸盐中的至少一种，避免使用硫酸镍、硫酸钴、硫酸锰。镍、钴、锰的硝酸盐、氯化盐、草酸盐、醋酸盐在高温下极易分解，不会存在明显残留，故对正极材料性能基本没有影响。通过控制金属盐混合溶液中SO4 2-的含量，甚至可以制备得到SO4 2-的含量接近于0的正极材料前驱体。但这会对原料的纯度要求较高，会造成原材料成本的上升。采用含有SO4 2-杂质的三元回收料中的Ni源、Co源、Mn源以及N源作为金属源，通过控制金属源的中SO4 2-的含量来制备正极材料前驱体更为经济。
在一些实施例中，所述金属盐混合溶液中，以Ni元素、Co元素、Mn元素的总质量为基准计，SO42-的含量≤1800ppm。具体可以为500pp、800ppm、1200ppm、1600ppm、1700ppm或1800ppm等，在次不做限定。
工业上，一般使用平均粒径D50来表征正极材料前驱体的粒度。然而正极材料前驱体和锂盐的反应是一个与接触面积有关的过程，因此Sauter平均粒径，即表面积加权平均粒径D[3，2]实际上更适合用来表征正极材料前驱体的粒度。D[3，2]越大，正极材料前驱体的表面活性越小，和锂盐的反应速率越慢。
需要说明的是，本申请中正极材料前驱体的表面积加权平均粒径D[3，2]可以通过马尔文3000激光粒度仪直接测量得到。具体可以通过以下公式：D[3，2]＝(∑y3Nd)/(∑y2Nd)计算得出，其中，y为粒径；Nd为粒径y的粒子数量。
具体地，正极材料前驱体的表面积加权平均粒径D[3，2]可以是1.98μm、1.95μm、1.8μm、1.75μm、1.64μm、1.5μm、1.3μm、1.2μm、1.1μm、0.8μm、0.9μm或0.5μm等，在此不做限定。正极材料前驱体的表面积加权平均粒径D[3，2]控制在上述范围内，正极材料前驱体的反应活性高，有利于提高正极材料前驱体在后续与锂源进行烧结的过程中的反应效率和传质效率。
正极材料前驱体中Ni、Co和Mn每种元素的质量含量的标准差具体可以是0.001、0.005、0.009、0.01、0.013、0.02、0.025、0.03、0.036、0.04、0.044、0.045、0.047或0.049等，在此不做限定。
在一些实施方式中，所述正极材料前驱体中Ni、Co和Mn每种元素的质量含量的极差均≤0.12，具体可以是0.01、0.015、0.018、0.02、0.029、0.03、0.035、0.048、0.059、0.06、0.08、0.097、0.10、0.105、0.11、0.112、0.115或0.119等，当然也还可以是上述范围内其他值，在此不做限定。
可以理解地，正极材料中Ni、Co和Mn每种元素的质量含量的标准差与极差可以反映出正极材料前驱体中Ni、Co、Mn元素的分布均匀程度，其Ni、Co和Mn每种元素的质量含量的标准差与极差越低，则正极材料前驱体中Ni、Co、Mn元素分布越均匀。同时，正极材料前驱体中Ni、Co、Mn元素的分布均匀性和单晶正极材料中Ni、Co、Mn元素的分布均匀性 之间有很好的继承性，正极材料前驱体中Ni、Co、Mn元素的分布越均匀，由该正极材料前驱体制成的单晶正极材料中Ni、Co、Mn元素的分布也就越均匀。
因此，控制正极材料前驱体中Ni、Co和Mn每种元素的质量含量的标准差与极差在上述范围内，有利于提升单晶正极材料中Ni、Co、Mn元素的分布均匀性，使得单晶正极材料中Ni、Co、Mn元素的分布均匀性好，单晶正极材料的晶体结构缺陷少，晶格应变低。
在一些实施方式中，所述正极材料前驱体包括二次颗粒，所述二次颗粒包括多个团聚的一次颗粒。
在一些实施方式中，所述正极材料前驱体包括二次颗粒，所述二次颗粒包括多个团聚的一次颗粒，所述一次颗粒呈球状。
在一些实施方式中，所述正极材料前驱体包括二次颗粒，所述二次颗粒包括多个团聚的一次颗粒，所述一次颗粒的粒径为20nm～1000nm，具体可以是20nm、50nm、80nm、100nm、150nm、200nm、500nm、800nm或1000nm等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。一次颗粒的粒径大于1000nm时，正极材料前驱体表面的反应活性差，所制备的单晶正极材料的晶格应变大，单晶正极材料的循环性能和倍率性能差。一次颗粒小于20nm，正极材料前驱体的振实密度低，导致所制备的单晶正极材料的振实密度低。控制一次颗粒的粒径在上述范围内，有利于提升由该正极材料前驱体制成的单晶正极材料的循环性能和倍率性能。
在一些实施方式中，所述正极材料前驱体的平均粒径D50＜3.5μm，具体可以是0.5μm、0.8μm、1.2μm、1.5μm、2μm、2.5μm、3μm、3.2μm或3.5μm等，当然也还可以是上述范围内其他值，在此不做限定。正极材料前驱体的粒度D50控制在上述范围内时，有利于提高正极材料前驱体的反应活性。
在一些实施方式中，所述正极材料前驱体的比表面积≥5m2/g，具体可以是5m2/g、6m2/g、8m2/g、10m2/g、12m2/g、15m2/g、20m2/g、25m2/g、50m2/g或100m2/g等，当然也还可以是上述范围内其他值，在此不做限定。正极材料前驱体的比表面积越大，正极材料前驱体的反应活性越高，有利于锂源和正极材料前驱体的反应，能够减少由该正极材料前驱体制备的单晶正极材料的晶格缺陷。
在一些实施方式中，所述正极材料前驱体的百特振实密度＞1g/cm3具体可以是1.1g/cm3、1.2g/cm3、1.3g/cm3、1.8g/cm3、2.3g/cm3、2.5g/cm3或3g/cm3等，当然也还可以是上述范围内其他值，在此不做限定。正极材料前驱体的振实密度控制在上述范围内时，有利于提高所制备的单晶正极材料的振实密度，从而提高电池的能量密度。
第三方面，本申请实施例提供了一种单晶正极材料的制备方法，包括以下步骤：
步骤S100，将含有镍盐、钴盐和锰盐的混合溶液进行雾化处理后，进行热分解，得到正极材料前驱体，所述正极材料前驱体的表面积加权平均粒径D[3，2]＜2.0μm，所述正极材料前驱体中Ni、Co和Mn每种元素的质量含量的标准差均≤0.05；
步骤S200，将所述正极材料前驱体与锂源混合后，置于含氧气氛下进行烧结，得到正极材料，所述单晶正极材料中Ni、Co和Mn每种元素的质量含量的标准差均≤0.03；所述单晶正极材料的晶格应变为ε，且ε＜0.2％。
本申请提供的单晶正极材料制备方法，通过将含有镍盐、钴盐和锰盐的混合溶液进行雾化处理后，进行热分解后得到正极材料前驱体。该正极材料前驱体的表面积加权平均粒径D[3，2]＜2.0μm，反应活性高，有利于提高正极材料前驱体和锂源在后续高温烧结过程中的反应 效率和传质效率；同时，上述制备方法得到的正极材料前驱体中Ni、Co和Mn每种元素的质量含量的标准差均≤0.05，说明正极材料前驱体中Ni、Co、Mn分布均匀性较好；进而上述正极材料前驱体在后续与锂源进行烧结所制备的单晶正极材料中Ni、Co和Mn每种元素的质量含量的标准差均≤0.03，单晶正极材料内部Ni、Co、Mn元素分布均匀性好，这有利于减少单晶正极材料的晶体结构缺陷；且单晶正极材料的晶格应变低，其晶格应变ε＜0.2％，能够降低锂离子在微晶之间的扩散能垒，提升Li离子扩散系数，使得单晶正极材料表现出良好的倍率性能、较低的DCR；同时，晶格应变低还可以抑制单晶正极材料内微裂纹的产生，进而提升单晶正极材料的循环性能。
步骤S100，将含有镍盐、钴盐和锰盐的混合溶液进行雾化处理后，进行热分解，得到正极材料前驱体，所述正极材料前驱体的表面积加权平均粒径D[3，2]＜2.0μm，所述正极材料前驱体中Ni、Co和Mn每种元素的质量含量的标准差均≤0.05。
具体地，正极材料前驱体的表面积加权平均粒径D[3，2]可以是1.98μm、1.95μm、1.8μm、1.75μm、1.64μm、1.5μm、1.3μm、1.2μm、1.1μm、0.8μm、0.9μm或0.5μm等，在此不做限定。正极材料前驱体的表面积加权平均粒径D[3，2]控制在上述范围内，正极材料前驱体的反应活性高，有利于提高正极材料前驱体在后续与锂源进行烧结的过程中的反应效率和传质效率。前驱体的表面积加权平均粒径D[3，2]主要和热解温度有关，随着热解温度提高，表面积加权平均粒径D[3，2]增大，前驱体的反应活性降低。
正极材料前驱体中Ni、Co和Mn每种元素的质量含量的标准差具体可以是0.001、0.005、0.009、0.01、0.013、0.02、0.025、0.03、0.036、0.01、0.044、0.045、0.047或0.049等，在此不做限定。
在一些实施方式中，所述镍盐包括氯化镍、硫酸镍、硝酸镍、碳酸镍、草酸镍和醋酸镍中的至少一种。
在一些实施方式中，所述钴盐包括氯化钴、草酸钴、碳酸钴、硫酸钴、硝酸钴和醋酸钴中的至少一种。
在一些实施方式中，所述锰盐包括氯化锰、碳酸锰、硫酸锰、草酸锰、硝酸锰和醋酸锰中的至少一种。
在一些实施方式中，所述混合溶液中Ni、Co与Mn的摩尔比为(50～98)：(0～20)：(0～30)，且所述混合溶液中Co与Mn的含量不为0。混合溶液中Ni、Co与Mn的摩尔比具体可以是50:0.1:0.1、60:10:30、65:15:20、65:5:30、70:5:25、70:10:20、80:5:15、85:10:5或98:1:1等，在此不做限定。
在一些实施方式中，所述混合溶液中总的金属浓度为200g/L～500g/L，具体可以是200g/L、220g/L、260g/L、300g/L、350g/L、400g/L、450g/L、480g/L或500g/L等，当然也还可以是上述范围内其他值，在此不做限定。申请人发现，混合液中的金属浓度能够影响前驱体的制备效率和热分解反应程度。当混合液金属浓度过高时，可能导致前驱体反应不完全，不仅会导致结构不稳定，还会使颗粒元素分布均匀度不理想，当混合液金属浓度过低时，不仅制备效率低下，且混合液在高温下快速蒸发时容易出现较多中空球形颗粒和破碎的情况，进而导致粒径分布不理想，甚至出现较多影响材料性能发挥的微粉颗粒的同时也相对的产生少量大颗粒，而大颗粒更容易造成元素分布不均匀，同时影响单晶正极材料前驱体的表面积加权平均粒径D[3，2]。
在一些实施方式中，所述混合溶液还包括含N元素的掺杂剂，N包括Al、Ti、Zr、Mg、Sr、Ba、Ca、Nb、W、Sb、Ta、Sn和Y中的至少一种。
在一些实施方式中，混合液雾化处理前还包括超声分搅拌步骤，超声搅拌包括将所述混合溶液置于具有超声搅拌功能的反应釜中进行加热和超声搅拌。
在一些实施方式中，所述超声搅拌温度为50℃～70℃。
在一些实施方式中，所述超声搅拌超声频率为30KHz-50KHz，超声搅拌时间为0.5h-2h。
在雾化之前进行加热、超声搅拌能够进步充分混合均匀混合液中的化学元素，能够快速获得更加均匀的雾滴，从而是的热分解时前驱体颗粒表面元素分布更加均匀，具有更小的质量含量的标准差均数值。
在一些实施方式中，混合液雾化处理前加入表面活性剂，所述表面活性剂包括聚乙二醇。
可以理解地，聚乙二醇溶解在水中达到一定浓度时，会降低了体系的表面张力，使正极材料前驱体颗粒整体粒径较小，同时元素分布也更均匀，并降低单晶正极材料前驱体的表面积加权平均粒径D[3，2]。
在一些实施方式中，所述表面活性剂占所述混合液总质量的0.5％-5％。表面活性剂上述范围内能够稳定获得形貌光滑、均匀和分散性好的前驱体颗粒。浓度过低表面活性剂发挥作用不明显，过高不仅会影响混合物整体浓度，导致Ni、Co、Mn金属离子的析出。
在一些实施方式中，混合液雾化处理前还包括超声分搅拌步骤，将所述混合溶液置于具有超声搅拌功能的反应釜中加热至50℃～70℃，同时调节超声搅拌超声频率为30-50KHz，在反应釜中超声搅拌0.5h-2h后关闭加热功能并加入混合液总质量0.5％-5％的聚乙二醇，再超声搅拌0.5h-1h。在一些实施方式中，所述正极材料前驱体的化学通式为NiaCobMncNdOe，其中，0.50≤a≤0.98，0＜b≤0.20，0＜c≤0.30，0≤d≤0.10，a+b+c+d＝1，1≤e≤1.15，N包括Al、Ti、Zr、Mg、Sr、Ba、Ca、Nb、W、Sb、Ta、Sn和Y中的至少一种。
在一些实施方式中，所述正极材料前驱体中Ni、Co和Mn每种元素的质量含量的极差均≤0.12，具体可以是0.01、0.015、0.018、0.02、0.029、0.03、0.035、0.048、0.059、0.06、0.08、0.097、0.10、0.105、0.11、0.112、0.115或0.119等，当然也还可以是上述范围内其他值，在此不做限定。
可以理解地，正极材料中Ni、Co和Mn每种元素的质量含量的标准差与极差可以反映出正极材料前驱体中Ni、Co、Mn元素的分布均匀程度，其Ni、Co和Mn每种元素的质量含量的标准差与极差越低，则正极材料前驱体中Ni、Co、Mn元素分布越均匀。同时，正极材料前驱体中Ni、Co、Mn元素的分布均匀性和单晶正极材料中Ni、Co、Mn元素的分布均匀性之间有很好的继承性，正极材料前驱体中Ni、Co、Mn元素的分布越均匀，由该正极材料前驱体制成的单晶正极材料中Ni、Co、Mn元素的分布也就越均匀。
控制正极材料前驱体中Ni、Co和Mn每种元素的质量含量的标准差与极差在上述范围内，有利于提升单晶正极材料中Ni、Co、Mn元素的分布均匀性，使得单晶正极材料中Ni、Co、Mn元素的分布均匀性好，单晶正极材料的晶体结构缺陷少，晶格应变低。
在一些实施方式中，所述混合溶液的流量为100L/h～900L/h，具体可以是100L/h、200L/h、300L/h、400L/h、500L/h、600L/h、700L/h、800L/h或900L/h等，在此不做限定。混合溶液的流量越高，前驱体的合成速度越快，但是Ni/Co/Mn分布的均匀性变差。流量低于100L/h，前驱体的合成效率低，制备成本高；当混合溶液的流量高于900L/h，前驱体中Ni、Co和Mn每种元素的质量含量的标准差和方差显著增大，导致制备的单晶正极材料中Ni、Co、Mn元素的分布均匀性降低，晶格应变增大。
在一些实施方式中，所述雾化处理的压力为0.4MPa～0.8MPa，具体可以是0.4MPa、0.5 MPa、0.6MPa、0.7MPa、0.75MPa或0.8MPa等，当然也还可以是上述范围内其他值，在此不做限定。
在一些实施方式中，所述热分解的温度为500℃～850℃，具体可以是500℃、550℃、600℃、650℃、700℃、750℃或800℃等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。随着热分解温度的提高，正极材料前驱体的表面积加权平均粒径D[3，2]会减小，造成前驱体活性的降低。当热解温度高于850℃时，正极材料前驱体的表面积加权平均粒径D[3，2]大于2.0μm；此时正极材料前驱体反应活性差，导致后续制备的单晶正极材料缺陷较多，晶格应变ε超过0.2％，使得单晶正极材料表现出较差的倍率性能，较高的DCR以及较低的循环性能。因此适当降低前驱体的热分解温度，有利于提高前驱体的反应活性，改善正极材料的倍率和DCR。然而，制备得到当热解温度小于500℃时，Ni、Co、Mn的金属盐分解不完全，造成前驱体Cl-、NO3 -、CO3 2-等阴离子含量过高，在后续制备正极材料的过程中，这些残留阴离子会抑制单晶的形成，且腐蚀烧结窑炉。
步骤S200，将所述正极材料前驱体与锂源混合后，置于含氧气氛下进行烧结，得到正极材料，所述单晶正极材料中Ni、Co和Mn每种元素的质量含量的标准差均≤0.03；所述单晶正极材料的晶格应变为ε，且ε＜0.2％。
在一些实施方式中，所述锂源包括碳酸锂、氢氧化锂、乙酸锂、硫酸锂、氯化锂、硝酸锂及草酸锂中的至少一种。
在一些实施方式中，所述锂源中的锂与所述正极材料前驱体中的镍、钴和锰总和的摩尔比为0.98～1.10，具体可以是0.98、0.99、1.01、1.03、1.05、1.06、1.08、1.09或1.10等，当然也还可以是上述范围内其他值，在此不做限定。
在一些实施方式中，所述烧结反应的温度为750℃～950℃，具体可以是750℃、760℃、780℃、800℃、850℃、900℃、920℃或950℃等，当然也还可以是上述范围内其他值，在此不做限定。烧结温度和Ni含量密切相关，Ni含量越高，烧结温度越低；此外，合适的烧结温度，有利于减少晶体结构缺陷，降低晶格应变，从而提升单晶正极材料的电化学性能。
在一些实施方式中，所述烧结反应的时间为10h～30h，具体可以是10h、12h、15h、16h、18h、20h、24h、28h或30h等，当然也还可以是上述范围内其他值，在此不做限定。
第四方面，本申请实施例提供了一种锂离子电池所述锂离子电池包括第一方面所述的单晶正极材料或第三方面所述的单晶正极材料的制备方法制备得到的正极材料。
下面将结合实施例和对比例进一步说明本申请的有益效果。
实施例1
(1)按摩尔比(nNi:nCo:nMn＝0.67:0.05:0.28)称取氯化镍、氯化钴、氯化锰加入水中，配成混合溶液，控制混合溶液中总的金属浓度为300g/L，将混合溶液置于具有超声搅拌功能的反应釜中加热至60℃，同时调节超声搅拌超声频率为33KHz，在反应釜中超声搅拌1h后关闭加热功能并加入混合液总质量1％的聚乙二醇，再超声搅拌0.5h；以Ni、Co、Mn元素的总质量为基准计，SO42-的含量为900ppm。
(2)将上述混合溶液雾化成液滴之后，置于空气气氛下在焙烧炉中650℃进行热分解；控制混合溶液的流量为200L/h，雾化压力0.6MPa。
(3)将热分解产物进行气流粉碎，得到正极材料前驱体(Ni0.67Co0.05Mn0.28O)。
(4)按摩尔比(nNi+Co+Mn：nLi＝1:1)称取正极材料前驱体与碳酸锂混合均匀后，置于氧 气气氛下升温至920℃烧结20h，得到单晶正极材料。
本实施例制得的单晶正极材料，其化学通式为LiNi0.67Co0.05Mn0.28O2，单晶正极材料的平均粒径D50为3.8μm、百特振实密度为1.95g/cm3。
图1为本申请实施例1制备的正极材料前驱体的SEM形貌图，图2为本申请实施例1制备的正极材料前驱体的另一SEM形貌图，如图1及图2所示，正极材料前驱体包括二次颗粒，二次颗粒包括多个团聚的一次颗粒。
在用扫描电子显微镜观察本申请实施例1制备的正极材料前驱体的情况下，在3K放大倍数下，对所述正极材料前驱体随机选取10个点进行EDS点扫描测试Ni、Co、Mn含量，在所述正极材料前驱体的EDS谱图结果中，如图3所示，所述正极材料前驱体中Ni含量的极差为0.095，标准差为0.036；Co含量的极差为0.029，标准差为0.009；Mn含量的极差为0.081，标准差为0.030。说明本实施例1制备的正极材料前驱体中Ni、Co、Mn分布均匀性好。此外，通过离子色谱检测，前驱体表面游离的SO42-的含量为504ppm。
图4为本申请实施例1制备的单晶正极材料的Williamsone-Hall分析拟合曲线，如图4所示，通过对图4中的数据进行分析计算可以得到单晶正极材料的晶格应变为0.11％。正极材料前驱体及单晶正极材料的其它性能参数详见表1、表2。
实施例2
与实施例1不同的是，(2)将上述混合溶液雾化成液滴之后，置于空气气氛下在焙烧炉中750℃进行热分解；控制混合溶液的流量为200L/h，雾化压力0.6MPa。
本实施例制得的单晶正极材料，其化学通式为LiNi0.67Co0.05Mn0.28O2，单晶正极材料的平均粒径D50为3.7μm、百特振实密度为1.85g/cm3。
正极材料前驱体及单晶正极材料的其它性能参数详见表1、表2。
实施例3
与实施例1不同的是，(2)将上述混合溶液雾化成液滴之后，置于空气气氛下在焙烧炉中650℃进行热分解；控制混合溶液的流量为100L/h，雾化压力0.6MPa。
本实施例制得的单晶正极材料，其化学通式为LiNi0.67Co0.05Mn0.28O2，单晶正极材料的平均粒径D50为4.0μm、百特振实密度为2.12g/cm3。
正极材料前驱体及单晶正极材料的其它性能参数详见表1、表2。
实施例4
与实施例1不同的是，(2)将上述混合溶液雾化成液滴之后，置于空气气氛下在焙烧炉中500℃进行热分解；控制混合溶液的流量为500L/h，雾化压力0.6MPa。
本实施例制得的单晶正极材料，其化学通式为LiNi0.67Co0.05Mn0.28O2，单晶正极材料的平均粒径D50为3.8μm、百特振实密度为1.90g/cm3。
正极材料前驱体及单晶正极材料的其它性能参数详见表1、表2。
实施例5
与实施例1不同的是，(4)按摩尔比(nNi+Co+Mn：nLi＝1:1)称取正极材料前驱体与碳酸锂混合均匀后，置于氧气气氛下升温至950℃烧结20h，得到单晶正极材料。
本实施例制得的单晶正极材料，其化学通式为LiNi0.67Co0.05Mn0.28O2，单晶正极材料的平均粒径D50为4.5μm、百特振实密度为2.2g/cm3。
正极材料前驱体及单晶正极材料的其它性能参数详见表1、表2。
实施例6
与实施例1不同的是，(4)按摩尔比(nNi+Co+Mn：nLi＝1:1)称取正极材料前驱体与碳酸锂混合均匀后，置于氧气气氛下升温至900℃烧结20h，得到单晶正极材料。
本实施例制得的单晶正极材料，其化学通式为LiNi0.67Co0.05Mn0.28O2，单晶正极材料的平均粒径D50为3.0μm、百特振实密度为1.68g/cm3。
正极材料前驱体及单晶正极材料的其它性能参数详见表1、表2。
实施例7
(1)按摩尔比(nNi:nCo:nMn＝0.88:0.06:0.04)称取氯化镍、氯化钴、氯化锰加入水中，配成混合溶液，控制混合溶液中总的金属浓度为300g/L，以Ni、Co、Mn元素的总质量为基准计，SO42-的含量≤1780ppm。
(2)将上述混合溶液雾化成液滴之后，置于空气气氛下在焙烧炉中600℃进行热分解；控制混合溶液的流量为200L/h，雾化压力0.6MPa。
(3)将热分解产物进行气流粉碎，得到正极材料前驱体(Ni0.88Co0.06Mn0.04O)。
(4)按摩尔比(nNi+Co+Mn：nLi＝1:1)称取正极材料前驱体与碳酸锂混合均匀后，置于氧气气氛下升温至850℃烧结15h，得到单晶正极材料。
本实施例制得的单晶正极材料，其化学通式为LiNi0.88Co0.06Mn0.04O2，单晶正极材料的平均粒径D50为3.2μm、百特振实密度为1.77g/cm3。
正极材料前驱体及单晶正极材料的其它性能参数详见表1、表2。
实施例8
(1)按摩尔比(nNi:nCo:nMn:nAl＝0.88:0.06:0.03:0.03)称取氯化镍、氯化钴、氯化锰和氯化铝加入水中，配成混合溶液，控制混合溶液中总的金属浓度为300g/L。
(2)将上述混合溶液雾化成液滴之后，置于空气气氛下在焙烧炉中600℃进行热分解；控制混合溶液的流量为200L/h，雾化压力0.6MPa。
(3)将热分解产物进行气流粉碎，得到正极材料前驱体(Ni0.88Co0.06Mn0.03Al0.03O)。
(4)按摩尔比(nNi+Co+Mn+Al：nLi＝1:1)称取正极材料前驱体与氢氧化锂混合均匀后，置于氧气气氛下升温至850℃烧结15h，得到正极材料。
本实施例制得的单晶正极材料，其化学通式为LiNi0.88Co0.06Mn0.03Al0.03O2，单晶正极材料的平均粒径D50为3.2μm、百特振实密度为1.78g/cm3。
正极材料前驱体及单晶正极材料的其它性能参数详见表1、表2。
实施例9
与实施例1不同的是，(1)以Ni、Co、Mn元素的总质量为基准计，SO42-的含量200ppm。通过离子色谱检测，本实施例所制备的前驱体表面游离的SO42-的含量为100ppm。本实施例制得的单晶正极材料，其化学通式为LiNi0.67Co0.05Mn0.28O2，单晶正极材料的平均粒径D50为3.8μm、百特振实密度为1.95g/cm3。正极材料前驱体及单晶正极材料的其它性能参数详见表1、表2。
实施例10
与实施例1不同的是，(1)按摩尔比(nNi:nCo:nMn＝0.67:0.05:0.28)称取氯化镍、氯化钴、氯化锰加入水中，配成混合溶液，控制混合溶液中总的金属浓度为500g/L，并加入混合液总质量5％的聚乙二醇；以Ni、Co、Mn元素的总质量为基准计，SO42-的含量为900ppm。
本实施例制得的单晶正极材料，其化学通式为LiNi0.67Co0.05Mn0.28O2，单晶正极材料的平均粒径D50为3.8μm、百特振实密度为1.83g/cm3。正极材料前驱体及单晶正极材料的其它 性能参数详见表1、表2。
实施例11
与实施例1不同的是，(1)按摩尔比(nNi:nCo:nMn＝0.67:0.05:0.28)称取氯化镍、氯化钴、氯化锰加入水中，配成混合溶液，控制混合溶液中总的金属浓度为200g/L，将混合溶液置于具有超声搅拌功能的反应釜中加热至60℃，同时调节超声搅拌超声频率为33KHz，在反应釜中超声搅拌1h；以Ni、Co、Mn元素的总质量为基准计，SO42-的含量为900ppm。
本实施例制得的单晶正极材料，其化学通式为LiNi0.67Co0.05Mn0.28O2，单晶正极材料的平均粒径D50为4.1μm、百特振实密度为1.82g/cm3。正极材料前驱体及单晶正极材料的其它性能参数详见表1、表2。
对比例1
与实施例1不同的是，(2)将上述混合溶液雾化成液滴之后，置于空气气氛下在焙烧炉中880℃进行热分解；控制混合溶液的流量为200L/h，雾化压力0.6MPa。
本对比例制得的单晶正极材料，其化学通式为LiNi0.67Co0.05Mn0.28O2，正极材料的平均粒径D50为3.82μm、百特振实密度为1.86g/cm3。
正极材料前驱体及单晶正极材料的其它性能参数详见表1、表2。
对比例2
与实施例1不同的是，(2)将上述混合溶液雾化成液滴之后，置于空气气氛下在焙烧炉中650℃进行热分解；控制混合溶液的流量为1000L/h，雾化压力0.6MPa。
本对比例制得的单晶正极材料，其化学通式为LiNi0.67Co0.05Mn0.28O2，单晶正极材料的平均粒径D50为3.72μm、百特振实密度为1.90g/cm3。
正极材料前驱体及单晶正极材料的其它性能参数详见表1、表2。
对比例3
与实施例1不同的是，(4)按摩尔比(nNi+Co+Mn：nLi＝1:1)称取正极材料前驱体与碳酸锂混合均匀后，置于氧气气氛下升温至700℃烧结20h，得到正极材料。
本对比例制得的正极材料为多晶正极材料，其化学通式为LiNi0.67Co0.05Mn0.28O2，多晶正极材料的平均粒径D50为3.2μm、百特振实密度为1.8g/cm3。
正极材料前驱体及单晶正极材料的其它性能参数详见表1、表2。
对比例4
参考CN113488642A实施例2制备Ni0.88Co0.06Mn0.03Al0.03(OH)2四元前驱体及相应正极材料。
(1)配置第一溶液：按照摩尔比镍:钴:锰＝0.88:0.06:0.03称取六水硫酸镍、一水硫酸锰、七水硫酸钴，利用去离子水溶解，配置得到质量浓度为2mol/L的过渡金属盐溶液，称为第一溶液；
(2)配置第二溶液：称取九水硝酸铝并溶解在去离子水中，然后将质量浓度为25％的浓氨水逐滴加入到铝盐溶液中，并不断搅拌，当pH＝8-9时停止滴加浓氨水，最后定容到氢氧化铝浓度为0.11mol/L，称为第二溶液；
(3)制备四元过渡金属氢氧化物前驱体：在反应釜中提前加入氨水底液，控制反应体系温度为55℃，并调节搅拌桨速度为1000rpm。利用1号计量泵将第一溶液按照35L/h的速度加入到反应釜中，利用2号计量泵将第二溶液按照20L/h的速度加入到反应釜中，利用3号 计量泵加入氨水溶液保持体系中氨水浓度为0.5mol/L，利用4号计量泵加入4mol/L的氢氧化钠溶液，控制反应体系的pH＝10.0±0.5。持续加料反应17h，并老化10h后，过滤并洗涤最终沉淀产物，在110℃烘箱中烘干12h，打碎过筛后得到Ni0.88Co0.06Mn0.03Al0.03(OH)2氢氧化物前驱体。
(4)将氢氧化物前驱体与氢氧化锂按照摩尔比1:1.05的比例混合均匀，在氧气气氛下500℃烧结3h，850℃烧结15h，降温后将产物粉碎过筛到D50为12μm，得到单晶正极材料LiNi0.88Co0.06Mn0.03Al0.03O2。
正极材料前驱体及单晶正极材料的其它性能参数详见表1、表2。
对比例5
参考CN116230922A制备Ni0.8Co0.1Mn0.1(OH)2前驱体及相应正极材料。
(1)按Ni/Co/Mn摩尔比0.8:0.1:0.1的比例混合NiSO4、CoSO4、MnSO4配成溶液。
(2)将所述溶液加入55℃的反应器中，并将NaOH和NH3·H2O用作沉淀剂和螯合剂进行共沉淀反应36小时，从而获得Ni0.8Co0.1Mn0.1(OH)2前驱体。
(3)将所述前体在80℃下干燥12小时，然后在110℃下再次干燥12小时。
(4)将所述前驱体与氢氧化锂按照摩尔比1:1.05的比例添加到干式高速混合机中混合5min。
(5)以2℃/分钟的升温速度升温至950℃，并在950℃下保持5小时，然后自然冷却至900℃并保持5小时。在升温和保持期间连续以10mL/min的流速通氧气。在完成煅烧后，自然冷却至室温，并经过粉碎和分级而制备LiNi0.8Co0.1Mn0.1O2的单晶正极材料。
正极材料前驱体及单晶正极材料的其它性能参数详见表1、表2。
对比例6
与实施例1不同的是，(1)以Ni、Co、Mn元素的总质量为基准计，SO42-的含量2000ppm。
本实施例所制备的前驱体表面游离的SO42-的含量为1200ppm。本实施例制得的单晶正极材料，其化学通式为LiNi0.67Co0.05Mn0.28O2，单晶正极材料的平均粒径D50为3.8μm、百特振实密度为1.95g/cm3。正极材料前驱体及单晶正极材料的其它性能参数详见表1、表2。
测试方法：
(1)在3K放大倍数下，采用扫描电子显微镜附带的能量色散X射线光谱仪(EDS)在未经处理的正极材料前驱体或单晶正极材料的表面随机选取10个点进行扫描测试正极材料前驱体或单晶正极材料的Ni、Co、Mn含量，统计Ni、Co和Mn每种元素的质量含量的标准差和极差来表征Ni、Co、Mn元素分布的均匀性。
(2)采用马尔文3000激光粒度仪测试得到正极材料前驱体的表面积加权平均粒径D[3，2]。
(3)由XRD数据通过Williamsone-Hall分析计算得到单晶正极材料的晶格应变和晶粒尺寸：
具体做法为：使用日本理学X射线衍射仪测量，具体条件：0.75度/分钟，步长0.02，在2θ范围内10至90度之间连续扫描。通过绘制以4sinθhkl为横坐标，βhklcosθhkl为纵坐标，绘制曲线并线性拟合，通过斜率和截距可以计算应变ε和晶粒尺寸D。值得一提的是，拟合所用的半峰宽βhkl需要剔除仪器的影响，即βhkl＝β总-β仪器，其中β总为实际测试的半峰宽值，β仪器为仪器所造成的半峰宽展宽，该数值可以通过测试标准硅片的XRD计算得到。本申请所 用测试设备的β仪器为0.000103。此外，选(003)、(101)、(102)、(104)、(015)、(107)、(113)这7个较强衍射峰的数据进行拟合，提高线性拟合程度，减少实测试误差。
其中β为半峰宽，θ是衍射角，单位均为弧度；k为常数，为0.89；λ为X射线波长，为0.154nm，D为晶粒尺寸，单位是nm。ε为晶格应变，无量纲。
(4)采用百特振实，称取一定量样品，以300times/min，振动3000次测试振实密度。
(5)电化学性能测试：
采用扣式半电池评估材料的电化学性能，具体做法如下：将单晶正极材料、导电炭黑、PVDF按照93:5:2质量比称取，按固含量50％加入N-甲基-2-吡咯烷酮(NMP)，高速分散机调成粘稠状浆料，用刮刀均匀涂覆在铝箔上，在80℃烘箱烘烤干后，进行辊压，并裁成直径14mm的正极片。以16mm的锂片为负极片，以Celgard聚丙烯膜为隔膜，以浓度为1mol/L的LiPF6的碳酸酯溶液为电解液，在充满氩气的手套箱内进行组装，得到扣式半电池。采用LAND电池测试系统，在25℃、3.0～4.3V下进行容量和循环性能测试，标称容量1C设置为200mAh/g。另外，记录每周放电初始时刻的电压UA和第60s的电压数据UB，放电电流IDis，直流内阻的计算公式为DCR＝(UA-UB)/IDis。
(6)SO42-含量测试：
取0.5克溶解于50ml水中，超声5min过滤后，滤液用离子色谱(赛默飞离子色谱ICS6000  HPIC)测量SO42-离子含量。
(7)电子背散射衍射(EBSD)测试：
将正极材料样品首先嵌入碳漆(PELCO)石墨块中，然后用氩离子束对块的横截面进行抛光。使用JEOL JSM-7000F型扫描电镜进行电子背散射衍射(EBSD)成像。设置EBSD图的步长为250nm(每个像素为250nm×250nm)。
上述测试结果详见表1～表3。
表1各实施例及对比例制备的正极材料前驱体性能参数结果

表2各实施例及对比例制备的单晶正极材料的性能参数结果
表3各实施例及对比例制备的单晶正极材料的电化学性能测试结果

根据表1～3的测试数据可知，实施例1～8制备的单晶正极材料，单晶正极材料中Ni、Co和Mn每种元素的质量含量的标准差均≤0.03，Ni、Co和Mn每种元素的质量含量的极差均≤0.08，说明单晶正极材料内部Ni、Co、Mn元素分布均匀性较好，这有利于减少单晶正极材料的晶体结构缺陷；单晶正极材料的晶格应变ε＜0.2％，这能够降低锂离子在微晶之间的扩散能垒，提升Li离子扩散系数，使得单晶正极材料表现出良好的倍率性能、较低的DCR；同时，晶格应变低还可以抑制单晶正极材料内微裂纹的产生，进而提升单晶正极材料的循环性能。
根据表1及表2的数据可知，正极材料前驱体中Ni、Co、Mn元素的分布均匀性和单晶正极材料中Ni、Co、Mn元素的分布均匀性之间有很好的继承性，正极材料前驱体中Ni、Co和Mn每种元素的质量含量的极差和标准差越小，单晶正极材料中Ni、Co和Mn每种元素的质量含量极差和标准差也越小；此外，单晶正极材料中Ni、Co、Mn含量的极差和标准差总是比前驱体的小，这是因为单晶正极材料制备过程中需要高温烧结，金属离子会进一步扩散，从而提高Ni、Co、Mn元素的分布均匀性。
根据表1～3的测试数据可知，实施例1制备的单晶正极材料的综合性能最佳。
比较实施例1和实施例2，实施例1的单晶正极材料表现出良好的倍率性能、较低的阻抗，以及较高的循环性能，这是因为实施例1制备正极材料前驱体时，雾化后的混合溶液进行热分解的温度合适，使得正极材料前驱体的表面积加权平均粒径D[3，2]低，正极材料前驱体反应活性高，减少了单晶正极材料的晶体结构缺陷，单晶正极材料晶格应变低。因此，实施例1制备的单晶正极材料表现出的倍率性能更好，阻抗更低，且循环性能也更好。
与实施例1相比，实施例5在正极材料前驱体与锂源进行烧结的过程中，烧结温度有所增加，单晶正极材料中Ni、Co和Mn每种元素的质量含量的极差和标准差更低，单晶正极材料的晶格应变ε有所降低，因此循环性能有所提升。但是由于单晶正极材料的晶粒尺寸明显偏大，Li离子扩散路径变长，因此实施例5制备的单晶正极材料的倍率性能较实施例1有所下降。
与实施例1相比，实施例6在正极材料前驱体与锂源进行烧结的过程中，烧结温度有所降低，使得单晶正极材料的晶粒尺寸偏小，且晶格应变ε有所增加，因此实施例6的单晶正极材料的循环稳定性较实施例1的单晶正极材料有所下降。
与实施例1相比，实施例9前驱体和正极材料的游离的SO4 2-含量降低，表现出更佳的倍率和循环性能。
与实施例1相比，实施例10在单晶正极材料前驱体混合液雾化前没有进行超声搅拌，单晶正极前驱体中Ni、Co和Mn每种元素的质量含量的极差和标准差更高，对其循环和内阻产生影响。
与实施例1相比，实施例11在单晶正极材料前驱体混合液雾化前没有加入聚乙二醇进行超声搅拌，单晶正极材料表面积加权平均粒径D[3，2]偏大，可能出现团聚大颗粒，且单晶正极前驱体中Ni、Co和Mn每种元素的质量含量的极差和标准差更高，对其循环和内阻产生影响。
与实施例1相比，对比例6正极材料的游离的SO42-超过1000ppm。过量的SO42-导致，造成材料容量和倍率、循环性能恶化。
与实施例1相比，对比例1提高了的正极材料前驱体制备过程中的热分解温度，从而使正极材料前驱体的表面积加权平均粒径D[3，2]大于2.0μm；该正极材料前驱体反应活性差，导致后续制备的单晶正极材料缺陷较多，晶格应变ε超过0.2％，使得单晶正极材料表现出较差的倍率性能，较高的DCR以及较低的循环性能。
与实施例1相比，对比例2的正极材料在前驱体的制备过程中，提高了雾化流量，制备得到的正极材料前驱体中Ni、Co和Mn每种元素的质量含量的标准差和方差显著增大，导致制备的单晶正极材料中Ni、Co、Mn元素的分布均匀性降低，晶格应变增大晶格应变ε超过0.2％，因此对比例2制备的单晶正极材料倍率性能和循环性能均下降。
与实施例1相比，对比例3的正极材料在前驱体与锂源进行烧结的过程中，烧结温度过低，得到的正极材料为多晶结构。该正极材料的晶粒尺寸低于150nm，具有良好的倍率性能；但晶格应变超过0.2％，在循环过程中容易出现开裂、粉化，降低正极材料结构稳定性，使得正极材料的循环容量出现大幅衰减。
与实施例1，对比例4正极材料前驱体中Ni、Co和Mn每种元素的质量含量的标准差和方差明显大于实施例1，因此制备得到的单晶正极材料晶格应变明显增大，晶格应变超过0.2％，从而导致单晶正极材料的倍率性能和循环性能显著下降。
同样地，对比例5制备的单晶正极材料，正极材料前驱体的表面积加权平均粒径D[3，2]过大，且正极材料前驱体中Ni、Co和Mn每种元素的质量含量的标准差和方差明显大于实施例1，因此制备得到的单晶正极材料晶格应变明显增大，晶格应变超过0.2％，从而导致正极材料的倍率性能和循环性能显著下降。
以上仅为本申请的较佳实施例而已，并不用以限制本申请，凡在本申请的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本申请保护的范围之内。

Claims (15)

  1. 一种单晶正极材料，其特征在于，所述单晶正极材料的化学通式为LixNiaCobMncNdO2，其中，0.98≤x≤1.1，0.50≤a≤0.98，0＜b≤0.20，0＜c≤0.30，0≤d≤0.10，a+b+c+d＝1，N包括Al、Ti、Zr、Mg、Sr、Ba、Ca、Nb、W、Sb、Ta、Sn和Y中的至少一种；
    在用扫描电子显微镜观察所述单晶正极材料的情况下，在3K放大倍数下，对所述单晶正极材料随机选取10个点进行EDS点扫描测试Ni、Co、Mn含量，在所述单晶正极材料的EDS谱图结果中，所述单晶正极材料中Ni、Co和Mn每种元素的质量含量的标准差均≤0.03；
    所述单晶正极材料的晶格应变为ε，且ε＜0.2％。
  2. 根据权利要求1所述的单晶正极材料，其特征在于，所述单晶正极材料中包括SO4 2-，所述SO4 2-的含量为δ，其中，0ppm≤δ≤800ppm。
  3. 根据权利要求1所述的单晶正极材料，其特征在于，所述单晶正极材料含有至少一个取向相同的单个晶粒，其中，所述单个晶粒的平均粒径为1μm～5μm。
  4. 根据权利要求1所述的单晶正极材料，其特征在于，所述单晶正极材料中Ni、Co和Mn每种元素的质量含量的极差均≤0.08。
  5. 根据权利要求1所述的单晶正极材料，其特征在于，所述单晶正极材料还包括包覆层，所述包覆层包括金属氧化物或锂离子导体，其中，所述金属氧化物中的金属包括Al、Ti、Zr、Y、Nb、Mg、W、B、Ce、Co和Mn中的至少一种。
  6. 根据权利要求1～5任一项所述的单晶正极材料，其特征在于，所述单晶正极材料满足如下特征中的至少一种：
    (1)所述单晶正极材料的晶粒尺寸为D，150nm＜D＜250nm；
    (2)所述单晶正极材料的平均粒径D50为1.5μm～5μm；
    (3)所述单晶正极材料的百特振实密度＞1.5g/cm3。
  7. 根据权利要求6所述的单晶正极材料，其特征在于，所述单晶正极材料满足如下特征中的至少一种：
    (1)所述单晶正极材料的平均粒径D50为3.0～4.5μm；
    (2)所述单晶正极材料的压实密度为1.68～2.2g/cm3；
    (3)所述单晶正极材料的化学通式包括LiNi0.67Co0.05Mn0.28O2、LiNi0.88Co0.06Mn0.04O2或LiNi0.88Co0.06Mn0.03Al0.03O2中的至少一种。
  8. 一种正极材料前驱体，其特征在于，所述正极材料前驱体的化学通式为NiaCobMncNdOe，其中，0.50≤a≤0.98，0＜b≤0.20，0＜c≤0.30，0≤d≤0.10，a+b+c+d＝1，1≤e≤1.15，N包括Al、Ti、Zr、Mg、Sr、Ba、Ca、Nb、W、Sb、Ta、Sn和Y中的至少一种；
    所述正极材料前驱体的表面积加权平均粒径D[3，2]＜2.0μm，所述正极材料前驱体中Ni、Co和Mn每种元素的质量含量的标准差均≤0.05。
  9. 根据权利要求8所述的正极材料前驱体，其特征在于，所述正极材料前驱体中包括SO4 2-，所述SO4 2-的含量为η，其中，0ppm≤η≤1800ppm。
  10. 根据权利要求8所述的正极材料前驱体，其特征在于，所述正极材料前驱体中Ni、Co和Mn每种元素的质量含量的极差均≤0.12。
  11. 根据权利要求8所述的正极材料前驱体，其特征在于，所述正极材料前驱体满足如下技术特征中的至少一种：
    (1)所述正极材料前驱体包括二次颗粒，所述二次颗粒包括多个团聚的一次颗粒；
    (2)所述正极材料前驱体包括二次颗粒，所述二次颗粒包括多个团聚的一次颗粒，所述一次颗粒呈球状；
    (3)所述正极材料前驱体包括二次颗粒，所述二次颗粒包括多个团聚的一次颗粒，所述一次颗粒的粒径为20nm～1000nm。
  12. 根据权利要求8所述的正极材料前驱体，其特征在于，所述正极材料前驱体满足如下技术特征中的至少一种：
    (1)所述正极材料前驱体的平均粒径D50＜3.5μm；
    (2)所述正极材料前驱体的比表面积＞5m2/g；
    (3)所述正极材料前驱体的百特振实密度＞1g/cm3。
  13. 一种单晶正极材料的制备方法，其特征在于，包括以下步骤：
    将含有镍盐、钴盐和锰盐的混合溶液进行雾化处理后，进行热分解，得到正极材料前驱体，所述正极材料前驱体的表面积加权平均粒径D[3，2]＜2.0μm，所述正极材料前驱体中Ni、Co和Mn每种元素的质量含量的标准差均≤0.05；
    将所述正极材料前驱体与锂源混合后，置于含氧气氛下进行烧结，得到单晶正极材料，所述单晶正极材料中Ni、Co和Mn每种元素的质量含量的标准差均≤0.03；所述单晶正极材料的晶格应变为ε，且ε＜0.2％。
  14. 根据权利要求13所述的制备方法，其特征在于，所述制备方法包括如下特征中的至少一种：
    (1)所述混合溶液中Ni、Co与Mn的摩尔比为(50～98)：(0～20)：(0～30)，且所述混合溶液中Co与Mn的含量不为0；
    (2)所述混合溶液中总的金属浓度为200g/L～500g/L；
    (3)所述混合溶液还包括含N元素的掺杂剂，N包括Al、Ti、Zr、Mg、Sr、Ba、Ca、Nb、W、Sb、Ta、Sn和Y中的至少一种；
    (4)所述正极材料前驱体的化学通式为NiaCobMncNdOe，其中，0.50≤a≤0.98，0＜b≤0.20，0＜c≤0.30，0≤d≤0.10，a+b+c+d＝1，1≤e≤1.15，N包括Al、Ti、Zr、Mg、Sr、Ba、Ca、Nb、W、Sb、Ta、Sn和Y中的至少一种；
    (5)所述混合溶液的流量为100L/h～900L/h；
    (6)所述雾化处理的压力为0.4MPa～0.8MPa；
    (7)所述热分解的温度为500℃～850℃。
  15. 一种锂离子电池，其特征在于，所述锂离子电池包括权利要求1～12任一项所述的单晶正极材料或权利要求13或14任一项所述的单晶正极材料的制备方法制备得到的单晶正极材料。
PCT/CN2024/122465 2023-10-13 2024-09-29 正极材料前驱体、单晶正极材料及制备方法、锂离子电池 Pending WO2025077631A1 (zh)

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