WO2025007438A1 - 正极活性材料及其制备方法、正极片和二次电池 - Google Patents

正极活性材料及其制备方法、正极片和二次电池 Download PDF

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Publication number
WO2025007438A1
WO2025007438A1 PCT/CN2023/122870 CN2023122870W WO2025007438A1 WO 2025007438 A1 WO2025007438 A1 WO 2025007438A1 CN 2023122870 W CN2023122870 W CN 2023122870W WO 2025007438 A1 WO2025007438 A1 WO 2025007438A1
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Prior art keywords
positive electrode
active material
electrode active
lithium
material according
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PCT/CN2023/122870
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English (en)
French (fr)
Inventor
董亮辰
张闻煦
尹充
刘磊磊
陈宇
冯道言
严旭丰
刘瑞
李琮熙
孙辉
刘相烈
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Ningbo Ronbay Lithium Battery Material Co Ltd
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Ningbo Ronbay Lithium Battery Material Co Ltd
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Priority to JP2024576693A priority Critical patent/JP2025525426A/ja
Priority to EP23941826.2A priority patent/EP4531142A4/en
Priority to KR1020247042728A priority patent/KR20250018525A/ko
Priority to US18/999,786 priority patent/US20250122099A1/en
Publication of WO2025007438A1 publication Critical patent/WO2025007438A1/zh
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    • C01G53/40—Complex oxides containing nickel and at least one other metal element
    • C01G53/42—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2
    • C01G53/44—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese
    • C01G53/50—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2
    • C01G53/51—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2 containing sodium
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    • C01G53/44—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese
    • C01G53/50—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2
    • C01G53/502—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2 containing lithium and cobalt
    • C01G53/504—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2 containing lithium and cobalt with the molar ratio of nickel with respect to all the metals other than alkali metals higher than or equal to 0.5, e.g. Li(MzNixCoyMn1-x-y-z)O2 with x ≥ 0.5
    • C01G53/506—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2 containing lithium and cobalt with the molar ratio of nickel with respect to all the metals other than alkali metals higher than or equal to 0.5, e.g. Li(MzNixCoyMn1-x-y-z)O2 with x ≥ 0.5 with the molar ratio of nickel with respect to all the metals other than alkali metals higher than or equal to 0.8, e.g. Li(MzNixCoyMn1-x-y-z)O2 with x ≥ 0.8
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    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
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Definitions

  • the present application relates to the technical field of lithium-ion batteries, and in particular to a positive electrode active material and a preparation method thereof, a positive electrode sheet and a secondary battery.
  • the main body of a lithium-ion battery is composed of four major parts: positive electrode, negative electrode, separator, and electrolyte.
  • the performance of the positive electrode material plays a decisive role in the battery performance. Improving the performance of the positive electrode material, such as specific capacity, power performance, and voltage, and trying to reduce its cost are the eternal themes of positive electrode material development.
  • the positive electrode materials of lithium-ion batteries mainly include olivine-structured phosphate systems and layered transition metal oxide systems.
  • the phosphate system is represented by lithium iron phosphate positive electrode, which has low cost, but limited energy density and power performance; although the layered transition metal oxide system has high energy density and excellent power performance, the cost is relatively high.
  • the positive electrode active material not only has high specific capacity and high cycle stability in a high voltage window, but also has low cost, so that the secondary battery prepared therefrom has high cost performance.
  • a positive electrode active material the chemical formula of which is Li x Na 1-x A y B 1-y O 2-n D n , wherein A is selected from a combination of Ni and Mn, and B is selected from at least one non-alkali metal positive valence metal other than Ni, Mn, Co, and S.
  • the element, D is selected from F and/or S, 0.8 ⁇ x ⁇ 0.92, 0.90 ⁇ y ⁇ 1.0, 0 ⁇ n ⁇ 0.2, and the peak position difference between the Ni-O bond and the Mn-O bond of the positive electrode active material in the Raman spectrum is greater than 80cm -1 and less than 110cm -1 .
  • the molar ratio of Ni to Mn is 3:7-1:1.
  • B is selected from at least one of Mg, Al, Zr, Ce, Cr, La, P, Ti, Ta, Nb, W, Mo, and Te.
  • B includes at least Nb or Mo
  • D includes at least F.
  • the crystal structure of the positive electrode active material is a lithiated spinel-layered composite crystal structure.
  • the surface of the crystal structure of the positive electrode active material further has a coating layer, and the coating layer is selected from at least one of an inert oxide coating layer, a lithium-containing transition metal oxide coating layer, a phosphate coating layer, and a fluoride coating layer.
  • the coating layer is selected from at least one of an inert oxide coating layer, a phosphate coating layer, and a fluoride coating layer.
  • the coating layer is selected from a lithium-containing transition metal oxide coating layer.
  • the coating amount of the coating layer is 0.5wt%-1wt% of the mass of the positive electrode active material
  • the inert oxide coating layer is selected from a composite of Al 2 O 3 and TiO 2 ;
  • the lithium-containing transition metal oxide coating layer is selected from Li 1+a ZrO 2+a , wherein 0 ⁇ a ⁇ 1.0;
  • the fluoride coating layer is selected from MgF 2 .
  • a method for preparing the positive electrode active material as described above comprises the following steps:
  • the Ni, Mn composite metal salt precursor is mixed with a lithium salt, a sodium salt and an inorganic salt containing any one non-alkali metal positive element except Ni, Mn, Co and S to obtain a mixture, wherein at least one of the lithium salt, the sodium salt and the inorganic salt contains a negative element D, and D is selected from F and/or S;
  • the mixture is sintered at 300° C.-500° C. to obtain a positive electrode active material.
  • the molar ratio of Ni to Mn in the Ni, Mn composite metal salt precursor is The ratio is 3:7-1:1;
  • the molar amount of lithium in the lithium salt is within 5 mol% excess relative to the reference;
  • the sintering time is 10h-30h.
  • the lithium salt is selected from at least two of lithium carbonate, lithium hydroxide, lithium oxalate, lithium nitrate, and lithium fluoride;
  • the sodium salt is selected from at least one of sodium carbonate, sodium oxalate and sodium sulfide.
  • the lithium salt when the lithium salt is selected from a combination of lithium carbonate and lithium oxalate, the molar ratio of the lithium carbonate to the lithium oxalate is 1:2-2:1.
  • a coating treatment is further included, and the coating treatment temperature is 300°C-400°C.
  • a positive electrode sheet comprises a positive electrode current collector and a positive electrode material layer arranged on the surface of the positive electrode current collector, wherein the positive electrode material layer comprises the positive electrode active material as described above.
  • a secondary battery comprises the positive electrode sheet as described above.
  • the positive electrode active material described in the present application achieves 1:1 by adjusting the sum of the atomic weights of Li and Na to be the same as the sum of the atomic weights of A and B. At the same time, it can be seen from the peak position difference between the Ni-O bond and the Mn-O bond that is greater than 80 cm -1 and less than 110 cm -1 that under the synergistic effect of the specific ratio of A, B, oxygen element, and negative valence element D, the positive electrode active material can have local cation disorder characteristics.
  • the positive electrode active material can have functional characteristics such as high specific capacity and high rate performance; on the other hand, the structural stability of the positive electrode active material can be improved, the effect of the interface side reaction can be reduced, the ionic conductivity can be improved, and the cycle stability of the positive electrode active material can be improved, so that the specific capacity and stability of the positive electrode active material can achieve a performance balance, so that the positive electrode active material can have both high specific capacity and high cycle stability in the high voltage window.
  • the positive electrode active material can also reduce the watt-hour cost by about 5%.
  • the positive electrode active material described in the present application shows high energy density and high cost performance. Using it to prepare positive electrode sheets and compose secondary batteries can make the secondary batteries have better electrical properties and higher cost performance, which is conducive to improving the market competitiveness of the positive electrode active material.
  • FIG1 is an EDS spectrum of the positive electrode active material prepared in Example 1;
  • FIG2 is a Raman spectrum comparison diagram of the positive electrode active material prepared in Example 1 and a typical spinel-type LiNi 0.5 Mn 1.5 O 4 , wherein a is a Raman spectrum diagram of the positive electrode active material prepared in Example 1, b is This is the Raman spectrum of a typical spinel LiNi 0.5 Mn 1.5 O 4 ;
  • FIG3 is an XRD spectrum of the positive electrode active materials prepared in Example 1, Example 2 and Example 12, wherein a is the diffraction spectrum of the positive electrode active material prepared in Example 1, b is the diffraction spectrum of the positive electrode active material prepared in Example 2, and c is the diffraction spectrum of the positive electrode active material prepared in Example 12;
  • FIG4 is a comparison of the charge-discharge curves of the positive electrode active material prepared in Example 1, typical ternary layered LiNi 0.5 Mn 0.5 O 2 , and typical spinel LiNi 0.5 Mn 1.5 O 4 at the first cycle current of 40 mA g -1 , wherein a is the positive electrode active material prepared in Example 1, b is the typical ternary layered LiNi 0.5 Mn 0.5 O 2 , and c is the typical spinel LiNi 0.5 Mn 1.5 O 4 ;
  • Figure 5 is the charge and discharge curve of sample 1, where a is the first cycle 2.5V-4.7V, 0.2C charge and discharge curve, b is the 2.5V-4.7V, 0.5C charge and discharge curve;
  • FIG6 is a charge and discharge curve of sample 2, wherein a is the first cycle 2.5V-4.7V, 0.2C charge and discharge curve, and b is the 2.5V-4.7V, 0.5C charge and discharge curve;
  • FIG7 is a charge and discharge curve of sample 16, wherein a is the first cycle 2.5V-4.7V, 0.2C charge and discharge curve, and b is the 2.5V-4.7V, 0.5C charge and discharge curve;
  • FIG8 is the charge and discharge curve of sample 17, where a is the first cycle 2.5V-4.7V, 0.2C charge and discharge curve, and b is the 2.5V-4.7V, 0.5C charge and discharge curve.
  • the present application provides a positive electrode active material, the composition chemical formula of which is Li x Na 1-x A y B 1-y O 2-n D n , wherein A is selected from a combination of Ni and Mn, B is selected from at least one non-alkali metal positive element other than Ni, Mn, Co, and S, D is selected from F and/or S, 0.8 ⁇ x ⁇ 0.92, 0.90 ⁇ y ⁇ 1.0, 0 ⁇ n ⁇ 0.2, and the peak position difference between the Ni-O bond and the Mn-O bond of the positive electrode active material in the Raman spectrum is greater than 80 cm -1 and less than 110cm -1 .
  • the positive electrode active material by adjusting the sum of the atomic weights of Li and Na to be the same as the sum of the atomic weights of A and B, reaches 1:1. At the same time, from the peak position difference between the Ni-O bond and the Mn-O bond being greater than 80cm -1 and less than 110cm -1 , it can be seen that under the synergistic effect of the specific ratio of A, B, oxygen element, and negative valence element D, the positive electrode active material can have local cation disorder characteristics.
  • the positive electrode active material can have functional characteristics such as high specific capacity and high rate performance; on the other hand, the structural stability of the positive electrode active material can be improved, the effect of the interface side reaction can be reduced, the ionic conductivity can be improved, and the cycle stability of the positive electrode active material can be improved, so that the specific capacity and stability of the positive electrode active material can achieve a performance balance, so that the positive electrode active material can have both high specific capacity and high cycle stability in the high voltage window.
  • the positive electrode active material can also reduce the watt-hour cost by about 5%. Therefore, the positive electrode active material described in the present application shows high energy density and high cost performance.
  • the molar ratio of Ni to Mn in the positive electrode active material is 3:7-1:1, which can not only make the nickel content of the positive electrode active material lower than that of the traditional ternary material, thereby making the positive electrode active material safer and lower in cost, but also ensure the voltage platform and rate performance of the positive electrode active material and inhibit its voltage attenuation.
  • the molar ratio of Ni to Mn includes but is not limited to 3:7, 2:3, 9:11 or 1:1.
  • B is beneficial to stabilizing the structure and reducing the interface side reactions, thereby improving the cycle stability of the positive electrode active material, reducing battery gas production, reducing the growth of direct current internal resistance (DCIR), and increasing the high temperature storage life.
  • DCIR direct current internal resistance
  • B is selected from at least one of Mg, Al, Zr, Ce, Cr, La, P, Ti, Ta, Nb, W, Mo and Te.
  • B includes various forms of doping, coating, or coexistence of doping and coating, and the present application does not limit this.
  • B is preferably at least one of Al, Cr, and Ti, which can more easily enter the crystal lattice and is beneficial to strengthening the Ni-O bond and the Mn-O bond; B is preferably at least one of Zr, La, and P, which can more easily be enriched in the subsurface layer and is beneficial to resisting electrolyte corrosion; B is preferably at least one of Ta, Nb, W, Mo, Te, and Ce, which can more easily be enriched at the grain boundary and is beneficial to improving its interface stability.
  • the positive electrode active material is a secondary particle structure composed of primary particles agglomerated, B will be more enriched on the surface of the secondary particles, which is beneficial to improving the interface stability and the ion conductivity.
  • B is preferably a high-valent element with a valence of +5 or more.
  • the high-valent element and oxygen have Higher binding energy is beneficial to enhance the stability of the anion framework during charge and discharge; on the other hand, it can reduce the valence of the Mn element, so that Mn can also provide part of the capacity, thereby compensating for the capacity loss caused by the reduction of oxygen ion activity.
  • high-valent elements are also beneficial to control the size of primary particles, thereby improving the microstructure of the positive electrode active material.
  • F and S also include various forms of existence such as doping and coating, among which F doping can reduce the energy barrier and disorder of the reaction process, and because the electronegativity of F is stronger than that of oxygen ions, its binding energy with cations is higher, and F doping can also improve the material interface stability, thereby enhancing the material framework stability; F coating can prevent the invasion of F ions in the electrolyte to a certain extent, and improve the stability of the battery long cycle system; although S doping has limited effect on the disorder of the material, since S can provide electrons for oxygen ions at high voltage, it inhibits excessive oxidation of oxygen ions to form oxygen, thereby avoiding the degradation of the positive electrode material and the oxidative decomposition of the electrolyte, so S doping and coating can also stabilize the anion framework.
  • doping can reduce the energy barrier and disorder of the reaction process, and because the electronegativity of F is stronger than that of oxygen ions, its binding energy with cations is higher, and F doping can also improve the material interface stability,
  • B includes at least Nb or Mo
  • D includes at least F, which is more conducive to improving its interface stability and making the positive electrode active material have better cycle stability under a high voltage window.
  • the crystal structure of the positive electrode active material is a lithiated spinel-layered composite crystal structure.
  • the surface of the crystal structure of the positive electrode active material also has a coating layer, and the coating layer is selected from at least one of an inert oxide coating layer, a lithium-containing transition metal oxide coating layer, a phosphate coating layer, and a fluoride coating layer, which is beneficial to reduce the electrolyte corrosion of the positive electrode active material during the cycle process, protect the surface structure from damage, and thus improve the long-cycle stability.
  • the coating layer is preferably at least one of an inert oxide coating layer, a phosphate coating layer, and a fluoride coating layer, which can effectively reduce the interfacial side reactions caused by the corrosion of the material surface by the electrolyte, thereby improving the stability of the battery system.
  • the coating layer preferably contains a lithium transition metal oxide coating layer, which is beneficial to improve the interface stability, reduce the interface side reaction, effectively improve the lithium ion transport capacity of the material, and further improve the capacity and rate performance.
  • the coating amount of the coating layer is 0.5wt%-1wt% of the mass of the positive electrode active material.
  • the inert oxide coating layer is preferably a composite of Al2O3 and TiO2 ; and/or, the lithium-containing transition metal oxide coating layer is preferably Li1+ aZrO2+a , wherein 0 ⁇ a ⁇ 1.0; and/or, the fluoride coating layer is preferably MgF2 .
  • the positive electrode active material not only has high specific capacity and high cycle stability in a high voltage window, but also has low cost, showing high energy density and high cost performance, making the positive electrode active material more competitive in the market.
  • the present application provides a method for preparing the positive electrode active material as described above, comprising the following steps:
  • step S1 the method for preparing the Ni, Mn composite metal salt precursor adopts the existing preparation process, including but not limited to the co-precipitation method, which will not be described in detail in this application, and those skilled in the art can choose according to actual preparation requirements.
  • the molar ratio of Ni to Mn in the Ni, Mn composite metal salt precursor is 3:7-1:1.
  • step S2 the use of lithium salt and sodium salt as a composite of two alkali metal salts can not only reduce the melting temperature of the system, but also promote the full fusion and reaction of alkali metals and transition metal salts under low temperature conditions, improve structural consistency and stability, but also ensure that the system has a certain degree of local cation disorder at a sintering temperature of 300°C-500°C, thereby ensuring its high capacity and high voltage stability characteristics.
  • the molar amount of lithium in the lithium salt is within 5 mol% excess relative to the benchmark.
  • the lithium salt is selected from at least two of lithium carbonate, lithium hydroxide, lithium oxalate, lithium nitrate, and lithium fluoride.
  • the eutectic system composed of different types of lithium salts has a lower melting point than a single lithium salt. On the one hand, it helps to shorten the sintering time. On the other hand, the flexible combination of multiple lithium salts to obtain a mixed lithium salt system with different melting points can achieve the effect of regulating the disorder of the material.
  • lithium carbonate When lithium carbonate is used as the main lithium salt, the decomposition of lithium carbonate is slow at a sintering temperature of 300°C-500°C, and the decomposition energy is high.
  • the energy of the reaction system is insufficient to drive the cations to rapidly transform from a disordered state to a Therefore, a sintering time of 10h-30h can make the lithium carbonate react completely without reducing the cation disorder, thereby ensuring that the prepared positive electrode active material has a high disorder.
  • the lithium salt is selected from a combination of lithium carbonate and lithium oxalate, and the molar ratio of the lithium carbonate to the lithium oxalate is 1:2-2:1, which can make the performance of the positive electrode active material better.
  • the sodium salt is selected from at least one of sodium carbonate, sodium oxalate, and sodium sulfide, preferably sodium oxalate. Since lithium salt and sodium salt have low melting points, they can effectively reduce the sintering temperature, increase the disorder of the material, and promote the rapid penetration of alkali metals, effectively reducing the residual alkali on the surface of the once sintered sample, so that it meets the requirements of industrial application and eliminates processing problems such as uniform jelly.
  • step S3 by adjusting the sintering temperature, not only can the Li and Na alkali metals completely penetrate into the Ni and Mn composite metal salt precursors and react evenly, thereby reducing lithium loss, but also can ensure that the cations have a certain degree of disorder, making the local cations in the positive electrode active material disordered, thereby improving the performance of the positive electrode active material.
  • the sintering temperature is 350°C-400°C or 400°C-450°C.
  • the sintering time is 10 h to 30 h, more preferably 15 h to 25 h, so that the positive electrode active material can have a more suitable disorder degree.
  • the mixture is sintered at 300° C. to 500° C. for 10 h to 30 h, it is washed with water and/or sintered twice to remove alkaline impurities remaining on the surface of the sintered product.
  • a coating treatment is further included, and the coating treatment temperature is 300°C-400°C.
  • the residual lithium can be directly coated with a lithium-containing transition metal oxide through coating treatment, thereby achieving direct conversion and utilization of the residual lithium.
  • the mixture can be washed with water or fired twice after sintering and then coated, or the mixture can be directly coated after sintering, which is not limited in the present application.
  • the ratio of the sum of the atomic weights of LiNa, the sum of the atomic weights of AB, and the sum of the atomic weights of negative valence atoms fluctuates within ⁇ 3% compared with the theoretical value of 1:1:2.
  • the present application also provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode material layer disposed on the surface of the positive electrode current collector, wherein the positive electrode material layer comprises the positive electrode active material as described above.
  • the positive electrode material layer further includes a conductive agent and a binder.
  • the present application also provides a secondary battery, comprising the positive electrode sheet as described above.
  • the secondary battery further includes a negative electrode sheet, a separator and an electrolyte.
  • the composite metal salt precursor Ni 0.3 Mn 0.7 (OH) 2 was prepared by coprecipitation method.
  • Ni 0.3 Mn 0.7 (OH) 2 is fully mixed with Li 2 CO 3 , LiF, Na 2 C 2 O 4 , and Nb 2 O 5 to obtain a mixture, wherein the total molar amount of Li in Li 2 CO 3 and LiF is 3 mol% in excess of the standard.
  • the mixture was placed in an air atmosphere and sintered at 425°C for 25 hours. After sintering, the sintered material was washed with water to remove alkaline impurities remaining on the surface, and then dried in an air atmosphere. The washed material was then mixed with Al2O3 for coating treatment at a temperature of 350°C to obtain a positive electrode active material having an Al2O3 coating layer, and the coating amount of Al2O3 was 0.5wt% of the mass of the positive electrode active material.
  • the prepared positive electrode active material was subjected to EDS energy spectrum analysis, and the results are shown in Figure 1. Since EDS cannot accurately quantify the mass proportion of the lithium element, it is further combined with the ICP element analysis in Table 1 (it should be noted that there is a difference in the calculation method of the mass proportion of EDS and ICP elements. EDS takes the mass proportion of the selected element as 100%, while ICP takes the total mass of the entire sample shown in the molecular formula as 100%). The mass proportion of each element is used to convert the corresponding atomic weight proportion.
  • the prepared positive electrode active material is Li 0.9 Na 0.1 (Ni 0.3 Mn 0.7 ) 0.98 Nb 0.02 O 1.8 F 0.2 with an Al 2 O 3 coating layer, which is consistent with the design value.
  • the prepared positive electrode active material was subjected to Raman spectrum comparison analysis with the typical spinel LiNi 0.5 Mn 1.5 O 4 , and the results are shown in FIG2 , wherein a is the Raman spectrum of the prepared positive electrode active material, and b is the Raman spectrum of the typical spinel LiNi 0.5 Mn 1.5 O 4 .
  • the Ni-O bond peak in the prepared positive electrode active material is 475cm -1 .
  • the Ni-O bond peak has almost no change; while the Mn-O bond peak is 567cm -1 , showing an obvious shift.
  • the peak position difference between the Ni-O bond and the Mn-O bond is about 90cm -1 , which is about 50cm -1 lower than that of the typical spinel -type LiNi0.5Mn1.5O4 , so as to distinguish it from traditional spinel materials.
  • nickel and manganese are alternately arranged in the transition metal layer, and there is no significant difference in their relative arrangement with lithium.
  • the Ni-O bond and the Mn-O bond outside the nucleus are usually a single peak, which is difficult to distinguish.
  • the peak position difference between the Ni-O bond and the Mn-O bond of the positive electrode active material prepared in this embodiment is about 90 cm -1 , which is distinguished from the traditional ordered layered materials.
  • this embodiment is a lithiated spinel-layered composite structure material with partial cation disorder characteristics, which can simultaneously provide the high stability of the spinel structure and the high capacity characteristics of the layered structure.
  • the prepared positive electrode active material was subjected to an X-ray diffraction test, and the result is shown in FIG3 .
  • the charge and discharge performance of the prepared positive electrode active material was compared with that of typical ternary layered LiNi 0.5 Mn 0.5 O 2 and typical spinel LiNi 0.5 Mn 1.5 O 4. The results are shown in FIG4 .
  • Example 2 The difference between Example 2 and Example 1 is that a composite metal salt precursor Ni 0.4 Mn 0.6 (OH) 2 is prepared, and the positive electrode active material is prepared based on the stoichiometric ratio of Li 0.9 Na 0.1 (Ni 0.4 Mn 0.6 ) 0.98 Nb 0.02 O 1.8 F 0.2 .
  • the prepared positive electrode active material is Li 0.9 Na 0.1 (Ni 0.4 Mn 0.6 ) 0.98 Nb 0.02 O 1.8 F 0.2 with an Al 2 O 3 coating layer.
  • the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 106 cm -1 .
  • the prepared positive electrode active material was subjected to an X-ray diffraction test, and the result is shown in FIG3 .
  • Example 3 The difference between Example 3 and Example 1 is that a composite metal salt precursor Ni 0.45 Mn 0.55 (OH) 2 is prepared, and the positive electrode active material is prepared based on the stoichiometric ratio of Li 0.9 Na 0.1 (Ni 0.45 Mn 0.55 ) 0.98 Nb 0.02 O 1.8 F 0.2 .
  • the prepared positive electrode active material is Li 0.9 Na 0.1 (Ni 0.45 Mn 0.55 ) 0.98 Nb 0.02 O 1.8 F 0.2 with an Al 2 O 3 coating layer.
  • the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 103 cm -1 .
  • Example 4 The difference between Example 4 and Example 1 is that a composite metal salt precursor Ni 0.5 Mn 0.5 (OH) 2 is prepared, and the positive electrode active material is prepared based on the stoichiometric ratio of Li 0.9 Na 0.1 (Ni 0.5 Mn 0.5 ) 0.98 Nb 0.02 O 1.8 F 0.2 .
  • the prepared positive electrode active material is Li 0.9 Na 0.1 (Ni 0.5 Mn 0.5 ) 0.98 Nb 0.02 O 1.8 F 0.2 with an Al 2 O 3 coating layer.
  • the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 105 cm -1 .
  • the composite metal salt precursor Ni 0.4 Mn 0.6 (OH) 2 was prepared by coprecipitation method.
  • Ni 0.4 Mn 0.6 (OH) 2 is fully mixed with Li 2 CO 3 , Li 2 C 2 O 4 , LiF, Na 2 C 2 O 4 , and Nb 2 O 5 to obtain a mixture, wherein the total molar amount of Li in Li 2 CO 3 , Li 2 C 2 O 4 and LiF is 3 mol% in excess of the standard, and the molar ratio of Li 2 CO 3 to Li 2 C 2 O 4 is 2:1.
  • the mixture was placed in an air atmosphere and sintered at 425°C for 20 hours. After sintering, the sintered material was washed with water to remove alkaline impurities remaining on the surface, and then dried in an air atmosphere. The washed material was then mixed with Al2O3 for coating treatment at a temperature of 350°C to obtain a positive electrode active material having an Al2O3 coating layer, and the coating amount of Al2O3 was 0.5wt% of the mass of the positive electrode active material.
  • the prepared positive electrode active material is Li 0.9 Na 0.1 (Ni 0.4 Mn 0.6 ) 0.98 Nb 0.02 O 1.8 F 0.2 with an Al 2 O 3 coating layer.
  • the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 101 cm -1 .
  • the composite metal salt precursor Ni 0.4 Mn 0.6 (OH) 2 was prepared by coprecipitation method.
  • Ni 0.4 Mn 0.6 (OH) 2 is fully mixed with Li 2 CO 3 , LiF, Na 2 C 2 O 4 , Nb 2 O 5 , and Na 2 S to obtain a mixture, wherein the total molar amount of Li in Li 2 CO 3 and LiF is 3 mol% in excess of the standard.
  • the mixture was placed in an air atmosphere and sintered at 425°C for 20 hours. After sintering, the sintered material was washed with water to remove alkaline impurities remaining on the surface, and then dried in an air atmosphere. The washed material was then mixed with Al2O3 for coating treatment at a temperature of 350°C to obtain a positive electrode active material having an Al2O3 coating layer, and the coating amount of Al2O3 was 0.5wt% of the mass of the positive electrode active material.
  • the prepared positive electrode active material is Li 0.9 Na 0.1 (Ni 0.4 Mn 0.6 ) 0.98 Nb 0.02 O 1.8 F 0.1 S 0.1 with an Al 2 O 3 coating layer.
  • the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 102 cm -1 .
  • the composite metal salt precursor Ni 0.4 Mn 0.6 (OH) 2 was prepared by coprecipitation method.
  • Ni 0.4 Mn 0.6 (OH) 2 is fully mixed with Li 2 CO 3 , LiF, Na 2 C 2 O 4 , and Mo 2 O 5 to obtain a mixture in which the total molar amount of Li in Li 2 CO 3 and LiF is 3 mol% in excess of the standard.
  • the mixture was placed in an air atmosphere and sintered at 425°C for 20 hours. After sintering, the sintered material was washed with water to remove alkaline impurities remaining on the surface, and then dried in an air atmosphere. The washed material was then mixed with Al2O3 for coating treatment at a temperature of 350°C to obtain a positive electrode active material having an Al2O3 coating layer, and the coating amount of Al2O3 was 0.5wt% of the mass of the positive electrode active material.
  • the prepared positive electrode active material is Li 0.9 Na 0.1 (Ni 0.4 Mn 0.6 ) 0.98 Mo 0.02 O 1.8 F 0.2 with an Al 2 O 3 coating layer.
  • the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 103 cm -1 .
  • the composite metal salt precursor Ni 0.4 Mn 0.6 (OH) 2 was prepared by coprecipitation method.
  • Ni 0.4 Mn 0.6 (OH) 2 is fully mixed with Li 2 CO 3 , LiF, Na 2 C 2 O 4 , Mo 2 O 5 , Nb 2 O 5 , TeO 2 , and TiO 2 to obtain a mixture, wherein the total molar amount of Li in Li 2 CO 3 and LiF is 3 mol% in excess of the standard.
  • the mixture was placed in an air atmosphere and sintered at 425°C for 22 hours. After sintering, the sintered material was washed with water to remove alkaline impurities remaining on the surface, and then dried in an air atmosphere. The washed material was then mixed with Al2O3 for coating treatment at a temperature of 350°C to obtain a positive electrode active material having an Al2O3 coating layer, and the coating amount of Al2O3 was 0.5wt% of the mass of the positive electrode active material.
  • the prepared positive electrode active material is Li 0.9 Na 0.1 (Ni 0.4 Mn 0.6 ) 0.9 Mo 0.02 Nb 0.02 Te 0.02 Ti 0.02 Al 0.02 O 1.8 F 0.2 with an Al 2 O 3 coating layer.
  • the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 106 cm -1 .
  • the composite metal salt precursor Ni 0.4 Mn 0.6 (OH) 2 was prepared by coprecipitation method.
  • Ni 0.4 Mn 0.6 (OH) 2 is fully mixed with Li 2 CO 3 , LiF, Na 2 C 2 O 4 , and Nb 2 O 5 to obtain a mixture, wherein the total molar amount of Li in Li 2 CO 3 and LiF is 3 mol% in excess of the standard.
  • the mixture was placed in an air atmosphere and sintered at 425° C. for 22 hours. After sintering, the sintered material was washed with water to remove alkaline impurities remaining on the surface, dried in an air atmosphere, and sintered at 350° C. to obtain a positive electrode active material.
  • the prepared positive electrode active material is Li 0.9 Na 0.1 (Ni 0.4 Mn 0.6 ) 0.98 Nb 0.02 O 1.8 F 0.2 .
  • the peak position difference between Ni-O bond and Mn-O bond in the prepared positive electrode active material is about 96 cm -1 .
  • the composite metal salt precursor Ni 0.4 Mn 0.6 (OH) 2 was prepared by coprecipitation method.
  • Ni 0.4 Mn 0.6 (OH) 2 is thoroughly mixed with Li 2 CO 3 , LiF, Na 2 C 2 O 4 , and Nb 2 O 5 to obtain a mixture in which the total molar amount of Li in Li 2 CO 3 and LiF is in excess of 3 mol% relative to the standard.
  • the mixture was placed in an air atmosphere and sintered at 425°C for 20 hours. After sintering, the sintered material was washed with water to remove alkaline impurities remaining on the surface, and then dried in an air atmosphere.
  • the washed material was then mixed with Al2O3 and MgF2 for coating treatment at a temperature of 350°C to obtain a positive electrode active material, the positive electrode active material having an Al2O3 coating layer and a MgF2 coating layer, the coating amount of Al2O3 being 0.5wt% of the mass of the positive electrode active material, and the coating amount of MgF2 being 0.5wt% of the mass of the positive electrode active material.
  • the prepared positive electrode active material is Li 0.9 Na 0.1 (Ni 0.4 Mn 0.6 ) 0.98 Nb 0.02 O 1.8 F 0.2 with Al 2 O 3 and MgF 2 coating layers. According to Raman spectrum analysis, the peak position difference between Ni-O bond and Mn-O bond in the prepared positive electrode active material is about 103 cm -1 .
  • the composite metal salt precursor Ni 0.4 Mn 0.6 (OH) 2 was prepared by coprecipitation method.
  • Ni 0.4 Mn 0.6 (OH) 2 is fully mixed with Li 2 CO 3 , LiF, Na 2 C 2 O 4 , and Nb 2 O 5 to obtain a mixture, wherein the total molar amount of Li in Li 2 CO 3 and LiF is 3 mol% in excess of the standard.
  • the mixture is placed in an air atmosphere and sintered at 425°C for 20 hours. After sintering, the sintered material is washed with water to remove alkaline impurities remaining on the surface, and then dried in an air atmosphere.
  • the washed material is then mixed with MgF2 and Li2ZrO3 for coating treatment at a temperature of 350°C to obtain a positive electrode active material having a MgF2 coating layer and a Li2ZrO3 coating layer, wherein the coating amount of MgF2 is 0.5wt% of the mass of the positive electrode active material, and the coating amount of Li2ZrO3 is 0.5wt% of the mass of the positive electrode active material.
  • the prepared positive electrode active material is Li 0.9 Na 0.1 (Ni 0.4 Mn 0.6 ) 0.98 Nb 0.02 O 1.8 F 0.2 with MgF 2 and Li 2 ZrO 3 coating layers. According to Raman spectrum analysis, the peak position difference between Ni-O bond and Mn-O bond in the prepared positive electrode active material is about 100 cm -1 .
  • the composite metal salt precursor Ni 0.4 Mn 0.6 (OH) 2 was prepared by coprecipitation method.
  • Ni 0.4 Mn 0.6 (OH) 2 is fully mixed with Li 2 CO 3 , LiF, Na 2 C 2 O 4 , and Nb 2 O 5 to obtain a mixture, wherein the total molar amount of Li in Li 2 CO 3 and LiF is 3 mol% in excess of the standard.
  • the mixture was placed in an air atmosphere and sintered at 425°C for 22 hours.
  • the material is washed with water to remove alkaline impurities remaining on the surface, and then dried in air atmosphere.
  • the washed material is then mixed with Al2O3 for coating treatment at a temperature of 350°C to obtain a positive electrode active material having an Al2O3 coating layer, and the coating amount of Al2O3 is 0.5wt% of the mass of the positive electrode active material.
  • the prepared positive electrode active material is Li 0.8 Na 0.2 (Ni 0.4 Mn 0.6 ) 0.98 Nb 0.02 O 1.8 F 0.2 with an Al 2 O 3 coating layer. According to Raman spectroscopy analysis, the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 101 cm -1 .
  • the prepared positive electrode active material was subjected to an X-ray diffraction test, and the result is shown in FIG3 .
  • Example 13 The difference between Example 13 and Example 2 is that the sintering temperature is 450°C.
  • the chemical formula of the prepared positive electrode active material is Li 0.9 Na 0.1 (Ni 0.4 Mn 0.6 ) 0.98 Nb 0.02 O 1.8 F 0.2 .
  • the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 106 cm -1 .
  • Example 14 The difference between Example 14 and Example 2 is that the prepared composite metal salt precursor is Ni 0.2 Mn 0.8 (OH) 2 .
  • the prepared positive electrode active material is Li 0.9 Na 0.1 (Ni 0.2 Mn 0.8 ) 0.98 Nb 0.02 O 1.8 F 0.2 with an Al 2 O 3 coating layer.
  • the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 102 cm -1 .
  • the composite metal salt precursor Ni 0.4 Mn 0.6 (OH) 2 was prepared by coprecipitation method.
  • Ni 0.4 Mn 0.6 (OH) 2 is fully mixed with Li 2 CO 3 , Li 2 C 2 O 4 , LiF, Na 2 C 2 O 4 , and Nb 2 O 5 to obtain a mixture, wherein the total molar amount of Li in Li 2 CO 3 , Li 2 C 2 O 4 and LiF is 5 mol% in excess of the standard, and the molar ratio of Li 2 CO 3 to Li 2 C 2 O 4 is 1:2.
  • the mixture was placed in an air atmosphere and sintered at 350°C for 30 hours. After sintering, the sintered material was washed with water to remove alkaline impurities remaining on the surface, and then dried in an air atmosphere. The washed material was then mixed with Al2O3 for coating treatment at a temperature of 300°C to obtain a positive electrode active material having an Al2O3 coating layer, and the coating amount of Al2O3 was 0.5wt% of the mass of the positive electrode active material.
  • the prepared positive electrode active material is Al 2 O 3 coated
  • the layer is Li 0.92 Na 0.02 (Ni 0.4 Mn 0.6 ) 0.9 Nb 0.05 Al 0.05 O 1.9 F 0.1 .
  • the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 103 cm -1 .
  • the diffraction peak position of the positive electrode active material obtained in Example 1 is consistent with that of the traditional spinel structure positive electrode material, but the crystallinity is much lower than that of the traditional spinel obtained by high temperature sintering, and the half-height width of the characteristic peak is significantly wider, indicating that it has the characteristics of the spinel structure.
  • FIG3 can prove that the positive electrode active material provided by this scheme has local cation disorder characteristics.
  • the first cycle is charged and discharged at 40mAg -1 , and the positive electrode active material prepared in Example 1 has a significantly higher capacity than the ordinary non-lithium-rich layered positive electrode ( ⁇ 3mAhg -1 ) at a discharge voltage of 3.0V-2.5V, and its capacity is >8mAhg -1 , indicating that the material has the electrochemical characteristics of Mn 4+ reduction to low-valent Mn ions in the spinel structure and providing capacity.
  • FIG. 4 can further prove that the positive electrode active material provided by this scheme has local cation disorder characteristics.
  • Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that no Na 2 C 2 O 4 is added for sintering.
  • the prepared positive electrode active material is Li(Ni 0.3 Mn 0.7 ) 0.98 Nb 0.02 O 1.8 F 0.2 with an Al 2 O 3 coating layer.
  • the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 116 cm -1 .
  • Comparative Example 2 The difference between Comparative Example 2 and Example 2 is that no Na 2 C 2 O 4 is added for sintering.
  • the prepared positive electrode active material is Li(Ni 0.4 Mn 0.6 ) 0.98 Nb 0.02 O 1.8 F 0.2 with an Al 2 O 3 coating layer.
  • the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 118 cm -1 .
  • Comparative Example 3 The difference between Comparative Example 3 and Example 4 is that no Na 2 C 2 O 4 is added for sintering.
  • the prepared positive electrode active material is Li(Ni 0.5 Mn 0.5 ) 0.98 Nb 0.02 O 1.8 F 0.2 with an Al 2 O 3 coating layer.
  • the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 126 cm -1 .
  • Comparative Example 4 The difference between Comparative Example 4 and Example 2 is that the sintering temperature is 600°C.
  • the prepared positive electrode active material is Li 0.9 Na 0.1 (Ni 0.4 Mn 0.6 ) 0.98 Nb 0.02 O 1.8 F 0.2 with an Al 2 O 3 coating layer.
  • the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 65 cm -1 .
  • Comparative Example 5 The difference between Comparative Example 5 and Example 2 is that LiF is not added during sintering.
  • the prepared positive electrode active material is Li 0.9 Na 0.1 (Ni 0.4 Mn 0.6 ) 0.98 Nb 0.02 O 2 with an Al 2 O 3 coating layer. According to Raman spectroscopy analysis, the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 121 cm -1 .
  • Comparative Example 6 The difference between Comparative Example 6 and Example 2 is that no Nb 2 O 5 is added during sintering.
  • the prepared positive electrode active material is Li 0.9 Na 0.1 Ni 0.4 Mn 0.6 O 1.8 F 0.2 with an Al 2 O 3 coating layer. According to Raman spectrum analysis, the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 125 cm -1 .
  • Comparative Example 7 The difference between Comparative Example 7 and Example 2 is that Ni 0.4 Mn 0.6 (OH) 2 is mixed and sintered with Li 2 CO 3 , LiF , Na 2 C 2 O 4 , and Nb 2 O 5 based on the stoichiometric ratio of Li 0.9 Na 0.1 (Ni 0.4 Mn 0.6 ) 0.8 Nb 0.1 Al 0.1 O 1.8 F 0.2.
  • the prepared positive electrode active material is Li 0.9 Na 0.1 (Ni 0.4 Mn 0.6 ) 0.8 Nb 0.1 Al 0.1 O 1.8 F 0.2 with an Al 2 O 3 coating layer.
  • the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 128 cm -1 .
  • Comparative Example 8 The difference between Comparative Example 8 and Example 2 is that Ni 0.4 Mn 0.6 (OH) 2 is mixed with Li 2 CO 3 , LiF , Na 2 C 2 O 4 , and Nb 2 O 5 and sintered based on the stoichiometric ratio of Li 0.7 Na 0.3 (Ni 0.4 Mn 0.6 ) 0.98 Nb 0.02 O 1.8 F 0.2.
  • the prepared positive electrode active material is Li 0.7 Na 0.3 (Ni 0.4 Mn 0.6 ) 0.98 Nb 0.02 O 1.8 F 0.2 with an Al 2 O 3 coating layer. According to Raman spectroscopy analysis, the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 126 cm -1 .
  • Comparative Example 9 The difference between Comparative Example 9 and Example 2 is that Ni 0.4 Mn 0.6 (OH) 2 is mixed with Li 2 CO 3 , LiF , Na 2 C 2 O 4 , and Nb 2 O 5 and sintered based on the stoichiometric ratio of Li 0.98 Na 0.02 (Ni 0.4 Mn 0.6 ) 0.98 Nb 0.02 O 1.8 F 0.2.
  • the prepared positive electrode active material is Li 0.98 Na 0.02 (Ni 0.4 Mn 0.6 ) 0.98 Nb 0.02 O 1.8 F 0.2 with an Al 2 O 3 coating layer.
  • the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 118 cm -1 .
  • Comparative Example 10 The difference between Comparative Example 10 and Example 2 is that Ni 0.4 Mn 0.6 (OH) 2 is mixed with Li 2 CO 3 , LiF , Na 2 C 2 O 4 , and Nb 2 O 5 and sintered based on the stoichiometric ratio of Li 0.9 Na 0.1 (Ni 0.4 Mn 0.6 ) 0.98 Nb 0.02 O 1.5 F 0.5.
  • the prepared positive electrode active material is Li 0.9 Na 0.1 (Ni 0.4 Mn 0.6 ) 0.98 Nb 0.02 O 1.5 F 0.5 with an Al 2 O 3 coating layer.
  • the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 116 cm -1 .
  • Comparative Example 11 The difference between Comparative Example 11 and Example 2 is that Ni 0.4 Mn 0.6 (OH) 2 is mixed with Li 2 CO 3 , LiF , Na 2 C 2 O 4 , and Nb 2 O 5 and sintered based on the stoichiometric ratio of Li 1.1 Na 0.1 (Ni 0.4 Mn 0.6 ) 0.98 Nb 0.02 O 1.8 F 0.2.
  • the prepared positive electrode active material is Li 1.1 Na 0.1 (Ni 0.4 Mn 0.6 ) 0.98 Nb 0.02 O 1.8 F 0.2 with an Al 2 O 3 coating layer.
  • the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 73 cm -1 . This is because the lithium ratio is too high, which causes the material to transition from disorder to order more quickly. Therefore, under the same sintering conditions, the disorder is significantly reduced.
  • Comparative Example 12 Li 0.9 Na 0.1 (Ni 0.4 Mn 0.6 ) 1 Nb 0.02 O 1.8 F 0.2 Based on the stoichiometric ratio of , Ni 0.4 Mn 0.6 (OH) 2 , Li 2 CO 3 , LiF, Na 2 C 2 O 4 , and Nb 2 O 5 were mixed and sintered.
  • the prepared positive electrode active material is Li 0.9 Na 0.1 (Ni 0.4 Mn 0.6 ) 1 Nb 0.02 O 1.8 F 0.2 with an Al 2 O 3 coating layer.
  • the peak position difference between the Ni-O bond and the Mn-O bond in the prepared positive electrode active material is about 116 cm -1 .
  • the ICP analysis results of the positive electrode active materials prepared in Examples 1 to 15 and Comparative Examples 1 to 12 are shown in Table 1, which shows the mass fraction of each element in the positive electrode active material (the rest is the mass fraction of the oxygen element), and the sum of the mass fraction of each element and the mass fraction of the oxygen element is 100%.
  • the corresponding atomic weight ratio is converted through the mass ratio of each element. Based on the fact that the atomic weight ratio of each element in the positive electrode active material is within ⁇ 3% of the theoretical finished product element, it can be proved that the prepared positive electrode active material is consistent with the design value.
  • the positive electrode active materials prepared in Examples 1 to 15 were used to prepare secondary battery samples 1 to 15 in sequence.
  • the positive electrode active materials prepared in Comparative Examples 1 to 12 were used to prepare secondary battery samples 16 to 27 in sequence.
  • the test results are shown in Table 2, where the first coulomb efficiency: one of the performance indicators used to quantify the negative electrode material of lithium-ion batteries, defined as the ratio of the discharge capacity to the charging capacity of a lithium-ion battery in the first charge and discharge cycle; battery capacity: the amount of electricity discharged by the battery under certain conditions (discharge rate, temperature, termination voltage, etc.).
  • the secondary battery made of the positive electrode active material provided in the present application not only has high specific capacity and high cycle stability in the high voltage window, but also has a capacity retention rate of more than about 91% after 100 cycles at 2.5V-4.7V and 0.5C, and has a low cost, making the secondary battery made therefrom highly cost-effective.

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Abstract

本申请涉及一种正极活性材料及其制备方法、正极片和二次电池。所述正极活性材料的组成化学式为LixNa1-xAyB1-yO2-nDn，其中，A选自Ni和Mn的组合物，B选自除Ni、Mn、Co、S之外的至少一种非碱金属正价元素，D选自F和/或S，0.8≤x≤0.92，0.90≤y＜1.0，0＜n≤0.2，所述正极活性材料在拉曼光谱中Ni-O键与Mn-O键的峰位差大于80cm-1且小于110cm-1。所述正极活性材料不仅在高电压窗口兼具高比容量和高循环稳定性，而且成本较低，使其制得的二次电池具有高性价比。

Description

正极活性材料及其制备方法、正极片和二次电池
本申请要求于2023年07月04日提交中国专利局、申请号为CN202310809840.1、申请名称为“正极活性材料及其制备方法、正极片和二次电池”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及锂离子电池技术领域，特别是涉及一种正极活性材料及其制备方法、正极片和二次电池。
背景技术
锂离子电池主体由正极、负极、隔膜、电解液四大部分组成，其中正极材料性能对电池性能起着决定性作用，提高正极材料性能如比容量、功率性能、电压，并设法降低其成本是正极材料开发的永恒主题。
从晶体结构角度，锂离子电池正极材料主要包括橄榄石结构的磷酸盐体系和层状过渡金属氧化物体系，其中，磷酸盐体系以磷酸铁锂正极为代表，成本低廉，但能量密度及功率性能有限；虽然层状过渡金属氧化物体系能量密度高、功率性能优良，但成本相对较高。此外，还有以锰酸锂为代表的尖晶石正极材料，但其能量密度较低且高温性能较差。
从元素组成角度，传统的三元正极材料虽然具有良好的稳定性和倍率性能，但其成本难以进一步降低。因此，有必要持续开发新型高能量、低成本的用于锂离子电池的正极材料。
发明内容
基于此，有必要针对上述问题，提供一种正极活性材料及其制备方法、正极片和二次电池；所述正极活性材料不仅在高电压窗口兼具高比容量和高循环稳定性，而且成本较低，使其制得的二次电池具有高性价比。
一种正极活性材料，组成化学式为LixNa1-xAyB1-yO2-nDn，其中，A选自Ni和Mn的组合物，B选自除Ni、Mn、Co、S之外的至少一种非碱金属正价 元素，D选自F和/或S，0.8≤x≤0.92，0.90≤y＜1.0，0＜n≤0.2，所述正极活性材料在拉曼光谱中Ni-O键与Mn-O键的峰位差大于80cm-1且小于110cm-1。
在其中一个实施例中，Ni与Mn的摩尔比为3:7-1:1。
在其中一个实施例中，B选自Mg、Al、Zr、Ce、Cr、La、P、Ti、Ta、Nb、W、Mo、Te中的至少一种。
在其中一个实施例中，B至少包括Nb或者Mo，D至少包括F。
在其中一个实施例中，所述正极活性材料的晶体结构为锂化尖晶石-层状复合型晶体结构。
在其中一个实施例中，所述正极活性材料的晶体结构表面还具有包覆层，所述包覆层选自惰性氧化物包覆层、含锂过渡金属氧化物包覆层、磷酸盐包覆层、氟化物包覆层中的至少一种。
在其中一个实施例中，当所述正极活性材料在拉曼光谱中Ni-O键与Mn-O键的峰位差小于110cm-1且大于100cm-1时，所述包覆层选自惰性氧化物包覆层、磷酸盐包覆层、氟化物包覆层中的至少一种。
在其中一个实施例中，当所述正极活性材料在拉曼光谱中Ni-O键与Mn-O键的峰位差大于80cm-1，小于或等于100cm-1时，所述包覆层选自含锂过渡金属氧化物包覆层。
在其中一个实施例中，所述包覆层的包覆量为所述正极活性材料质量的0.5wt％-1wt％；
及/或，所述惰性氧化物包覆层选自Al2O3与TiO2的复合物；
及/或，所述含锂过渡金属氧化物包覆层选自Li1+aZrO2+a，其中，0＜a≤1.0；
及/或，所述氟化物包覆层选自MgF2。
一种如上所述的正极活性材料的制备方法，包括如下步骤：
制备Ni、Mn复合金属盐前驱体；
以LixNa1-xAyB1-yO2-nDn，0.8≤x≤0.92，0.90≤y＜1.0，0＜n≤0.2为基准，将所述Ni、Mn复合金属盐前驱体与锂盐、钠盐以及含有除Ni、Mn、Co、S之外任意一种非碱金属正价元素的无机盐混合，得到混合物，其中，所述锂盐、所述钠盐、所述无机盐中的至少一种含有负价元素D，D选自F和/或S；
将所述混合物于300℃-500℃进行烧结，得到正极活性材料。
在其中一个实施例中，所述Ni、Mn复合金属盐前驱体中Ni与Mn的摩 尔比为3:7-1:1；
及/或，所述锂盐中锂的摩尔量相对于基准过量5mol％以内；
及/或，所述烧结的时间为10h-30h。
在其中一个实施例中，所述锂盐选自碳酸锂、氢氧化锂、草酸锂、硝酸锂、氟化锂中的至少两种；
及/或，所述钠盐选自碳酸钠、草酸钠、硫化钠中的至少一种。
在其中一个实施例中，所述锂盐选自碳酸锂与草酸锂的组合物时，所述碳酸锂与所述草酸锂的摩尔比为1:2-2:1。
在其中一个实施例中，在将所述混合物于300℃-500℃烧结10h-30h之后，还包括包覆处理，所述包覆处理的温度为300℃-400℃。
一种正极片，包括正极集流体以及设置于所述正极集流体表面的正极材料层，所述正极材料层包括如上所述的正极活性材料。
一种二次电池，包括如上所述的正极片。
本申请所述的正极活性材料，通过调控Li、Na的原子量之和与A、B的原子量之和相同，达到了1:1，同时，从Ni-O键与Mn-O键的峰位差大于80cm-1且小于110cm-1可知，在特定配比的A、B以及氧元素、负价元素D的协同作用下，能够使正极活性材料具备局部阳离子无序特征，一方面，可以使正极活性材料兼具高比容量、高倍率性等功能特性；另一方面，可以提高正极活性材料的结构稳定性，降低界面副反应的作用，改善离子电导率，进而提高正极活性材料的循环稳定性，使正极活性材料的比容量和稳定性达到性能平衡，从而使正极活性材料能够在高电压窗口兼具高比容量和高循环稳定性。此外，所述正极活性材料还可以使瓦时成本降低5％左右。
因此，本申请所述的正极活性材料显示出高能量密度和高性价比，将其用于制备正极片，并组成二次电池，能够使二次电池具有更优异的电性能和更高的性价比，有利于提高所述正极活性材料的市场竞争力。
附图说明
图1为实施例1制得的正极活性材料的EDS能谱图；
图2为实施例1制得的正极活性材料与典型的尖晶石型LiNi0.5Mn1.5O4的拉曼光谱对比图，其中，a为实施例1制得的正极活性材料的拉曼光谱图，b 为典型的尖晶石型LiNi0.5Mn1.5O4的拉曼光谱图；
图3为实施例1、实施例2和实施例12制得的正极活性材料的XRD图谱，其中，a为实施例1制得的正极活性材料的衍射图谱，b为实施例2制得的正极活性材料的衍射图谱，c为实施例12制得的正极活性材料的衍射图谱；
图4为实施例1制得的正极活性材料与典型的三元层状LiNi0.5Mn0.5O2、典型的尖晶石型LiNi0.5Mn1.5O4在首圈40mAg-1电流下的充放电曲线对比图，其中，a为实施例1制得的正极活性材料，b为典型的三元层状LiNi0.5Mn0.5O2，c为典型的尖晶石型LiNi0.5Mn1.5O4；
图5为样品1的充放电曲线，其中，a为首圈2.5V-4.7V，0.2C充放电曲线，b为2.5V-4.7V，0.5C充放电曲线；
图6为样品2的充放电曲线，其中，a为首圈2.5V-4.7V，0.2C充放电曲线，b为2.5V-4.7V，0.5C充放电曲线；
图7为样品16的充放电曲线，其中，a为首圈2.5V-4.7V，0.2C充放电曲线，b为2.5V-4.7V，0.5C充放电曲线；
图8为样品17的充放电曲线，其中，a为首圈2.5V-4.7V，0.2C充放电曲线，b为2.5V-4.7V，0.5C充放电曲线。
具体实施方式
为了便于理解本申请，下面将对本申请进行更详细的描述。但是，应当理解，本申请可以以许多不同的形式来实现，并不限于本文所描述的实施方式或实施例。相反地，提供这些实施方式或实施例的目的是使对本申请的公开内容的理解更加透彻全面。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同。本文中在本申请的说明书中所使用的术语只是为了描述具体的实施方式或实施例的目的，不是旨在于限制本申请。
本申请提供一种正极活性材料，组成化学式为LixNa1-xAyB1-yO2-nDn，其中，A选自Ni和Mn的组合物，B选自除Ni、Mn、Co、S之外的至少一种非碱金属正价元素，D选自F和/或S，0.8≤x≤0.92，0.90≤y＜1.0，0＜n≤0.2，所述正极活性材料在拉曼光谱中Ni-O键与Mn-O键的峰位差大于80cm-1且小于 110cm-1。
所述正极活性材料，通过调控Li、Na的原子量之和与A、B的原子量之和相同，达到了1:1，同时，从Ni-O键与Mn-O键的峰位差大于80cm-1且小于110cm-1可知，在特定配比的A、B以及氧元素、负价元素D的协同作用下，能够使正极活性材料具备局部阳离子无序特征，一方面，可以使正极活性材料兼具高比容量、高倍率性等功能特性；另一方面，可以提高正极活性材料的结构稳定性，降低界面副反应的作用，改善离子电导率，进而提高正极活性材料的循环稳定性，使正极活性材料的比容量和稳定性达到性能平衡，从而使正极活性材料能够在高电压窗口兼具高比容量和高循环稳定性。此外，所述正极活性材料还可以使瓦时成本降低5％左右。因此，将本申请所述的正极活性材料显示出高能量密度和高性价比。
作为优选，所述正极活性材料中Ni与Mn的摩尔比为3:7-1:1，不仅可以使正极活性材料的镍含量低于传统三元材料，从而使正极活性材料的安全性更高、成本更低，而且能够保证正极活性材料的电压平台和倍率性能，抑制其电压衰减。
进一步优选，Ni与Mn的摩尔比包括但不限于3:7、2:3、9:11或者1:1。
在本申请中组成化学式的特定配比下，B有利于稳定结构，降低界面副反应，进而有利于提高正极活性材料的循环稳定性，减少电池产气、降低直流内阻(DCIR)增长、提高高温存储寿命。
作为优选，B选自Mg、Al、Zr、Ce、Cr、La、P、Ti、Ta、Nb、W、Mo、Te中的至少一种。
需要说明的是，所述正极活性材料中，B包括掺杂、包覆或者掺杂包覆共存等多种存在形式，本申请对此不做限定。
当B以掺杂的形式存在时，B优选Al、Cr、Ti中的至少一种，更容易进入晶格，有利于增强Ni-O键和Mn-O键；B优选Zr、La、P中的至少一种，更容易富集于亚表层，有利于抵御电解液侵蚀；B优选Ta、Nb、W、Mo、Te、Ce中的至少一种，更容易富集于晶界处，有利于提高其界面稳定性。
当B以包覆的形式存在时，由于所述正极活性材料为由一次粒子团聚构成的二次粒子结构，B将更多的富集于二次粒子表面，有利于提高界面稳定性，改善离子电导率。
进一步地，B优选+5价及以上的高价元素，一方面，高价元素与氧具有 较高的结合能，有利于增强充放电过程中阴离子框架稳定性；另一方面，可以降低Mn元素价态，使Mn同样可提供部分容量，从而补充氧离子活性降低带来的容量损失。此外，高价元素还有利于调控一次粒子的尺寸大小，进而改善正极活性材料的微观结构。
在本申请中组成化学式的特定配比下，F、S也分别包括掺杂、包覆等多种存在形式，其中，F掺杂可以降低反应过程能垒和无序度，并且由于F的电负性强于氧离子，其与阳离子结合能更高，F掺杂还可以提高材料界面稳定性，从而增强材料框架稳定性；F包覆可以一定程度防止电解液中F离子的侵入，提高电池长循环体系稳定性；S掺杂虽然对材料的无序度作用有限，但由于S于高电压下可以为氧离子提供电子，抑制氧离子过度氧化形成氧气，从而避免正极材料衰退及电解液氧化分解，因此S的掺杂和包覆同样可以稳定阴离子框架。
进一步优选，所述正极活性材料中，B至少包括Nb或者Mo，D至少包括F，更有利于提高其界面稳定性，使正极活性材料在高电压窗口下具有更优异的循环稳定性。
在一实施方式中，所述正极活性材料的晶体结构为锂化尖晶石-层状复合型晶体结构。
在另一实施方式中，所述正极活性材料的晶体结构表面还具有包覆层，所述包覆层选自惰性氧化物包覆层、含锂过渡金属氧化物包覆层、磷酸盐包覆层、氟化物包覆层中的至少一种，有利于降低正极活性材料在循环过程中的电解液侵蚀，保护表面结构不受破坏，从而提高长循环稳定性。
当所述正极活性材料在拉曼光谱中Ni-O键与Mn-O键的峰位差小于110cm-1且大于100cm-1时，无序度较高，结构稳定性较高，有利于容量发挥及倍率性能发挥，所述包覆层优选惰性氧化物包覆层、磷酸盐包覆层、氟化物包覆层中的至少一种，可以有效减弱材料表面被电解液侵蚀引起的界面副反应，从而提升电池体系稳定性。
当所述正极活性材料在拉曼光谱中Ni-O键与Mn-O键的峰位差大于80cm-1，小于或等于100cm-1时，无序度适中，同样具备较高的结构稳定性，所述包覆层优选含锂过渡金属氧化物包覆层，有利于在提高界面稳定性、减少界面副反应的同时，有效提升材料锂离子的输运能力，进一步提升容量和倍率性能的发挥。
作为优选，所述包覆层的包覆量为所述正极活性材料质量的0.5wt％-1wt％。
具体地，所述惰性氧化物包覆层优选Al2O3与TiO2的复合物；及/或，所述含锂过渡金属氧化物包覆层优选Li1+aZrO2+a，其中，0＜a≤1.0；及/或，所述氟化物包覆层优选MgF2。
因此，所述正极活性材料不仅在高电压窗口兼具高比容量和高循环稳定性，而且成本较低，显示出高能量密度和高性价比，使所述正极活性材料具有更高市场竞争力。
本申请提供一种如上所述的正极活性材料的制备方法，包括如下步骤：
S1，制备Ni、Mn复合金属盐前驱体；
S2，以LixNa1-xAyB1-yO2-nDn，0.8≤x≤0.92，0.90≤y＜1.0，0＜n≤0.2为基准，将所述Ni、Mn复合金属盐前驱体与锂盐、钠盐以及含有除Ni、Mn、Co、S之外任意一种非碱金属正价元素的无机盐混合，得到混合物，其中，所述锂盐、所述钠盐、所述无机盐中的至少一种含有负价元素D，D选自F和/或S；
S3，将所述混合物于300℃-500℃进行烧结，得到正极活性材料。
步骤S1中，制备Ni、Mn复合金属盐前驱体的方法采用现有制备工艺，包括但不限于共沉淀法，本申请对此不再赘述，本领域技术人员可以根据实际制备需求自行选择。
作为优选，所述Ni、Mn复合金属盐前驱体中Ni与Mn的摩尔比为3:7-1:1。
步骤S2中，采用锂盐、钠盐两种碱金属盐复合，不仅可以降低体系的熔融温度，有利于促进低温条件下碱金属与过渡金属盐的充分融合与反应，提高结构一致性、稳定性，而且可以保证体系在300℃-500℃的烧结温度下具有一定的局部阳离子无序度，进而保证其高容量及高电压稳定的特性。
考虑到制备过程中存在一定的锂损失，优选所述锂盐中锂的摩尔量相对于基准过量5mol％以内。
具体地，所述锂盐选自碳酸锂、氢氧化锂、草酸锂、硝酸锂、氟化锂中的至少两种，不同种类的锂盐组成的共融体系，较单一锂盐熔点更低，一方面有助于减短烧结时间，另一方面，多种锂盐的灵活组合以获取具备不同熔点的混合锂盐体系，可以达到调控材料无序度的效果。
当优选碳酸锂作为主要锂盐时，由于碳酸锂在300℃-500℃的烧结温度下，分解较缓慢，分解能较高，反应体系能量不足以推动阳离子由无序态快速转 变为有序态，因此，配合10h-30h的烧结时间可以使碳酸锂反应完全但不会降低阳离子无序度，从而保证制得的正极活性材料具备较高的无序度。
进一步优选，所述锂盐选自碳酸锂与草酸锂的组合物，且所述碳酸锂与所述草酸锂的摩尔比为1:2-2:1，可以使正极活性材料的性能更佳。
所述钠盐选自碳酸钠、草酸钠、硫化钠中的至少一种，优选为草酸钠，由于锂盐和钠盐熔点较低，可以有效降低烧结温度，提高材料的无序度，并促进碱金属的快速渗入，有效降低一次烧结样品表面的残碱量，使其满足工业化应用要求，消除匀浆果冻等加工问题。
步骤S3中，通过调控烧结温度，不仅可以使Li、Na碱金属完全渗入Ni、Mn复合金属盐前驱体内部并且反应均匀，降低锂损失，而且能够确保阳离子具有一定的无序度，使正极活性材料中局部阳离子无序，从而提高正极活性材料的性能。作为优选，烧结温度为350℃-400℃或者400℃-450℃。
作为优选，所述烧结的时间为10h-30h，更优选为15h-25h，可以使正极活性材料具有更合适的无序度。
在一实施方式中，在将所述混合物于300℃-500℃烧结10h-30h之后，进行水洗和/或二次反烧，可以去除烧结物表面残留的碱性杂质，
在另一实施方式中，在将所述混合物于300℃-500℃烧结10h-30h之后，还包括包覆处理，所述包覆处理的温度为300℃-400℃。
当烧结物表面残留锂时，通过包覆处理可以将残锂直接进行含锂过渡金属氧化物的包覆，从而实现残锂的直接转化利用。
需要说明的是，可以将混合物烧结完先进行水洗或者二次反烧，再进行包覆处理，也可以将混合物烧结完直接进行包覆处理，本申请对此不做限定。
可以理解的是，制备得到的正极活性材料中，LiNa原子量之和、AB原子量之和、负价原子量之和的比值，与理论值1:1:2存在±3％以内的数据波动。
本申请还提供一种正极片，包括正极集流体以及设置于所述正极集流体表面的正极材料层，所述正极材料层包括如上所述的正极活性材料。
在一实施方式中，所述正极材料层还包括导电剂和粘结剂。
本申请还提供一种二次电池，包括如上所述的正极片。
在一实施方式中，所述二次电池还包括负极片、隔膜以及电解液。
以下，将通过以下具体实施例对所述正极活性材料及其制备方法、正极片和二次电池做进一步的说明。
实施例1
采用共沉淀法制备复合金属盐前驱体Ni0.3Mn0.7(OH)2。
以Li0.9Na0.1(Ni0.3Mn0.7)0.98Nb0.02O1.8F0.2的化学计量比为基准，将Ni0.3Mn0.7(OH)2与Li2CO3、LiF、Na2C2O4、Nb2O5充分混合，得到混合物，其中，Li2CO3和LiF中Li的总摩尔量相对于基准过量3mol％。
将混合物置于空气气氛于425℃进行烧结25h。烧结完成后，将烧结得到的材料进行水洗，以清除表面残留的碱性杂质，并于空气气氛进行烘干。然后将水洗后的材料与Al2O3混合进行包覆处理，包覆处理的温度为350℃，得到正极活性材料，所述正极活性材料具有Al2O3包覆层，Al2O3的包覆量为所述正极活性材料质量的0.5wt％。
将制得的正极活性材料进行EDS能谱分析，结果如图1所示，由于EDS无法对锂元素质量占比进行精确定量，进一步结合表1的ICP元素分析(需要说明的是，EDS与ICP元素质量占比计算方式存在差别，EDS以选定元素质量占比为100％，而ICP以分子式所示的整个样品质量总和为100％)，通过各元素质量占比进行相应的原子量占比换算，基于各元素组成与理论成品元素的原子量配比差距均在±3％以内，可以证明制得的正极活性材料为具有Al2O3包覆层的Li0.9Na0.1(Ni0.3Mn0.7)0.98Nb0.02O1.8F0.2，与设计值一致。
将制得的正极活性材料与典型的尖晶石型LiNi0.5Mn1.5O4进行拉曼光谱对比分析，结果如图2所示，其中，a为制得的正极活性材料的拉曼光谱图，b为典型的尖晶石型LiNi0.5Mn1.5O4的拉曼光谱图。根据图2可知，制得的正极活性材料中Ni-O键峰位是475cm-1，与典型的尖晶石型LiNi0.5Mn1.5O4相比，Ni-O键峰位几乎没有变化；而Mn-O键峰位是567cm-1，出现明显偏移，峰位显著左移靠近Ni-O键且几乎与Ni-O键峰形成一个大的胞峰，表明Mn、Ni与锂的相对位置差异减小，无序度降低，此时Ni-O键与Mn-O键的峰位差约为90cm-1，较典型的尖晶石型LiNi0.5Mn1.5O4降低了约50cm-1，以使其与尖晶石传统尖晶石材料进行区分。并且，在传统层状材料中，镍与锰交替排布在过渡金属层中，其与锂的相对排布无显著差别，因此其核外Ni-O键与Mn-O键通常为一个胞峰，难以区分，而本实施例制得的正极活性材料的Ni-O键与Mn-O键的峰位差约为90cm-1，与传统的有序层状材料进行区分，证明本实施例为具备部分阳离子无序特征的锂化尖晶石-层状复合结构材料，可同时提供尖晶石结构的高稳定性及层状结构的高容量特性。
将制得的正极活性材料进行X射线衍射测试，结果图3所示。
将制得的正极活性材料与典型的三元层状LiNi0.5Mn0.5O2、典型的尖晶石型LiNi0.5Mn1.5O4进行充放电性能对比分析，结果如图4所示。
实施例2
实施例2与实施例1的区别在于，制得复合金属盐前驱体Ni0.4Mn0.6(OH)2，以Li0.9Na0.1(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.2的化学计量比为基准，制备正极活性材料。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3包覆层的Li0.9Na0.1(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为106cm-1。
将制得的正极活性材料进行X射线衍射测试，结果图3所示。
实施例3
实施例3与实施例1的区别在于，制得复合金属盐前驱体Ni0.45Mn0.55(OH)2，以Li0.9Na0.1(Ni0.45Mn0.55)0.98Nb0.02O1.8F0.2的化学计量比为基准，制备正极活性材料。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3包覆层的Li0.9Na0.1(Ni0.45Mn0.55)0.98Nb0.02O1.8F0.2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为103cm-1。
实施例4
实施例4与实施例1的区别在于，制得复合金属盐前驱体Ni0.5Mn0.5(OH)2，以Li0.9Na0.1(Ni0.5Mn0.5)0.98Nb0.02O1.8F0.2的化学计量比为基准，制备正极活性材料。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3包覆层的Li0.9Na0.1(Ni0.5Mn0.5)0.98Nb0.02O1.8F0.2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为105cm-1。
实施例5
采用共沉淀法制备复合金属盐前驱体Ni0.4Mn0.6(OH)2。
以Li0.9Na0.1(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.2的化学计量比为基准，将Ni0.4Mn0.6(OH)2与Li2CO3、Li2C2O4、LiF、Na2C2O4、Nb2O5充分混合，得到混合物，其中，Li2CO3、Li2C2O4和LiF中Li的总摩尔量相对于基准过量3mol％，Li2CO3与Li2C2O4的摩尔比为2:1。
将混合物置于空气气氛于425℃进行烧结20h。烧结完成后，将烧结得到的材料进行水洗，以清除表面残留的碱性杂质，并于空气气氛进行烘干。然后将水洗后的材料与Al2O3混合进行包覆处理，包覆处理的温度为350℃，得到正极活性材料，所述正极活性材料具有Al2O3包覆层，Al2O3的包覆量为所述正极活性材料质量的0.5wt％。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3包覆层的Li0.9Na0.1(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为101cm-1。
实施例6
采用共沉淀法制备复合金属盐前驱体Ni0.4Mn0.6(OH)2。
以Li0.9Na0.1(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.1S0.1的化学计量比为基准，将Ni0.4Mn0.6(OH)2与Li2CO3、LiF、Na2C2O4、Nb2O5、Na2S充分混合，得到混合物，其中，Li2CO3和LiF中Li的总摩尔量相对于基准过量3mol％。
将混合物置于空气气氛于425℃进行烧结20h。烧结完成后，将烧结得到的材料进行水洗，以清除表面残留的碱性杂质，并于空气气氛进行烘干。然后将水洗后的材料与Al2O3混合进行包覆处理，包覆处理的温度为350℃，得到正极活性材料，所述正极活性材料具有Al2O3包覆层，Al2O3的包覆量为所述正极活性材料质量的0.5wt％。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3包覆层的Li0.9Na0.1(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.1S0.1。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为102cm-1。
实施例7
采用共沉淀法制备复合金属盐前驱体Ni0.4Mn0.6(OH)2。
以Li0.9Na0.1(Ni0.4Mn0.6)0.98Mo0.02O1.8F0.2的化学计量比为基准，将Ni0.4Mn0.6(OH)2与Li2CO3、LiF、Na2C2O4、Mo2O5充分混合，得到混合物，其中，Li2CO3和LiF中Li的总摩尔量相对于基准过量3mol％。
将混合物置于空气气氛于425℃进行烧结20h。烧结完成后，将烧结得到的材料进行水洗，以清除表面残留的碱性杂质，并于空气气氛进行烘干。然后将水洗后的材料与Al2O3混合进行包覆处理，包覆处理的温度为350℃，得到正极活性材料，所述正极活性材料具有Al2O3包覆层，Al2O3的包覆量为所述正极活性材料质量的0.5wt％。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3包覆层的Li0.9Na0.1(Ni0.4Mn0.6)0.98Mo0.02O1.8F0.2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为103cm-1。
实施例8
采用共沉淀法制备复合金属盐前驱体Ni0.4Mn0.6(OH)2。
以Li0.9Na0.1(Ni0.4Mn0.6)0.9Mo0.02Nb0.02Te0.02Ti0.02Al0.02O1.8F0.2的化学计量比为基准，将Ni0.4Mn0.6(OH)2与Li2CO3、LiF、Na2C2O4、Mo2O5、Nb2O5、TeO2、TiO2充分混合，得到混合物，其中，Li2CO3和LiF中Li的总摩尔量相对于基准过量3mol％。
将混合物置于空气气氛于425℃进行烧结22h。烧结完成后，将烧结得到的材料进行水洗，以清除表面残留的碱性杂质，并于空气气氛进行烘干。然后将水洗后的材料与Al2O3混合进行包覆处理，包覆处理的温度为350℃，得到正极活性材料，所述正极活性材料具有Al2O3包覆层，Al2O3的包覆量为所述正极活性材料质量的0.5wt％。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3包覆层的Li0.9Na0.1(Ni0.4Mn0.6)0.9Mo0.02Nb0.02Te0.02Ti0.02Al0.02O1.8F0.2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为106cm-1。
实施例9
采用共沉淀法制备复合金属盐前驱体Ni0.4Mn0.6(OH)2。
以Li0.9Na0.1(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.2的化学计量比为基准，将Ni0.4Mn0.6(OH)2与Li2CO3、LiF、Na2C2O4、Nb2O5充分混合，得到混合物，其中，Li2CO3和LiF中Li的总摩尔量相对于基准过量3mol％。
将混合物置于空气气氛于425℃进行烧结22h。烧结完成后，将烧结得到的材料进行水洗，以清除表面残留的碱性杂质，并于空气气氛进行烘干，并于350℃进行反烧，得到正极活性材料。
结合EDS能谱和ICP分析可知，制得的正极活性材料为Li0.9Na0.1(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为96cm-1。
实施例10
采用共沉淀法制备复合金属盐前驱体Ni0.4Mn0.6(OH)2。
以Li0.9Na0.1(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.2的化学计量比为基准，将 Ni0.4Mn0.6(OH)2与Li2CO3、LiF、Na2C2O4、Nb2O5充分混合，得到混合物，其中，Li2CO3和LiF中Li的总摩尔量相对于基准过量3mol％。
将混合物置于空气气氛于425℃进行烧结20h。烧结完成后，将烧结得到的材料进行水洗，以清除表面残留的碱性杂质，并于空气气氛进行烘干。然后将水洗后的材料与Al2O3、MgF2混合进行包覆处理，包覆处理的温度为350℃，得到正极活性材料，所述正极活性材料具有Al2O3包覆层和MgF2包覆层，Al2O3的包覆量为所述正极活性材料质量的0.5wt％，MgF2的包覆量为所述正极活性材料质量的0.5wt％。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3、MgF2包覆层的Li0.9Na0.1(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为103cm-1。
实施例11
采用共沉淀法制备复合金属盐前驱体Ni0.4Mn0.6(OH)2。
以Li0.9Na0.1(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.2的化学计量比为基准，将Ni0.4Mn0.6(OH)2与Li2CO3、LiF、Na2C2O4、Nb2O5充分混合，得到混合物，其中，Li2CO3和LiF中Li的总摩尔量相对于基准过量3mol％。
将混合物置于空气气氛于425℃进行烧结20h。烧结完成后，将烧结得到的材料进行水洗，以清除表面残留的碱性杂质，并于空气气氛进行烘干。然后将水洗后的材料与MgF2、Li2ZrO3混合进行包覆处理，包覆处理的温度为350℃，得到正极活性材料，所述正极活性材料具有MgF2包覆层和Li2ZrO3包覆层，MgF2的包覆量为所述正极活性材料质量的0.5wt％，Li2ZrO3的包覆量为所述正极活性材料质量的0.5wt％。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有MgF2、Li2ZrO3包覆层的Li0.9Na0.1(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为100cm-1。
实施例12
采用共沉淀法制备复合金属盐前驱体Ni0.4Mn0.6(OH)2。
以Li0.8Na0.2(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.2的化学计量比为基准，将Ni0.4Mn0.6(OH)2与Li2CO3、LiF、Na2C2O4、Nb2O5充分混合，得到混合物，其中，Li2CO3和LiF中Li的总摩尔量相对于基准过量3mol％。
将混合物置于空气气氛于425℃进行烧结22h。烧结完成后，将烧结得到 的材料进行水洗，以清除表面残留的碱性杂质，并于空气气氛进行烘干。然后将水洗后的材料与Al2O3混合进行包覆处理，包覆处理的温度为350℃，得到正极活性材料，所述正极活性材料具有Al2O3包覆层，Al2O3的包覆量为所述正极活性材料质量的0.5wt％。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3包覆层的Li0.8Na0.2(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为101cm-1。
将制得的正极活性材料进行X射线衍射测试，结果图3所示。
实施例13
实施例13与实施例2的区别在于，烧结温度为450℃。
结合EDS能谱和ICP分析可知，制得的正极活性材料的组成化学式为Li0.9Na0.1(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为106cm-1。
实施例14
实施例14与实施例2的区别在于，制备的复合金属盐前驱体为Ni0.2Mn0.8(OH)2。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3包覆层的Li0.9Na0.1(Ni0.2Mn0.8)0.98Nb0.02O1.8F0.2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为102cm-1。
实施例15
采用共沉淀法制备复合金属盐前驱体Ni0.4Mn0.6(OH)2。
以Li0.92Na0.02(Ni0.4Mn0.6)0.9Nb0.05Al0.05O1.9F0.1的化学计量比为基准，将Ni0.4Mn0.6(OH)2与Li2CO3、Li2C2O4、LiF、Na2C2O4、Nb2O5充分混合，得到混合物，其中，Li2CO3、Li2C2O4和LiF中Li的总摩尔量相对于基准过量5mol％，Li2CO3与Li2C2O4的摩尔比为1:2。
将混合物置于空气气氛于350℃进行烧结30h。烧结完成后，将烧结得到的材料进行水洗，以清除表面残留的碱性杂质，并于空气气氛进行烘干。然后将水洗后的材料与Al2O3混合进行包覆处理，包覆处理的温度为300℃，得到正极活性材料，所述正极活性材料具有Al2O3包覆层，Al2O3的包覆量为所述正极活性材料质量的0.5wt％。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3包覆 层的Li0.92Na0.02(Ni0.4Mn0.6)0.9Nb0.05Al0.05O1.9F0.1。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为103cm-1。
根据图3可知，实施例1制得的正极活性材料的衍射峰位置与传统尖晶石结构正极材料一致，但结晶度远低于高温烧结所得的传统尖晶石，特征峰的半高宽显著更宽，表明其具有尖晶石结构特征，同时，其主峰位置与层状正极一致，表明其同样具备层状正极的晶体结构，但其位于层状正极(006)/(102)与(108)/(110)两处分裂峰衍射角度的两处衍射峰并未显著分裂开来，表明其并非传统的阳离子高度有序的层状正极，阳离子无序导致该两处分裂峰表现为单一胞峰。因此，图3可以证明本方案提供的正极活性材料存在局部阳离子无序特征。
此外，对比图3中实施例1、实施例2和实施例12制得的正极活性材料的衍射图谱可知，实施例1、实施例2和实施例12制得的正极活性材料具有相近的特征峰位置及相对强度，并且，对比实施例2和实施例12制得的正极活性材料可知，当Na的比例由10mol％提升至20mol％时，出现位于15°-17°的特征峰，因此，本申请所述的正极活性材料中Na含量不同会呈现不同的Na相特征峰。
根据图4可知，于2.5V-4.7V vs Li/Li+，首圈以40mAg-1进行充放电，实施例1制得的正极活性材料于放电电压3.0V-2.5V具有显著高于普通非富锂层状正极(<3mAhg-1)的容量发挥，其容量>8mAhg-1，表明该材料具有尖晶石结构的Mn4+还原为低价Mn离子并提供容量的电化学特征，同时，其于首圈放电曲线于3.5V-4.5V之间表现为显著的类似层状的固溶体反应的向上开口抛物线型斜坡状放电曲线，而非尖晶石的平台状两相反应曲线，表明该材料兼具层状结构的特征。因此，图4能够进一步证明本方案提供的正极活性材料存在局部阳离子无序特征。
对比例1
对比例1与实施例1的区别在于，未加入Na2C2O4进行烧结。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3包覆层的Li(Ni0.3Mn0.7)0.98Nb0.02O1.8F0.2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为116cm-1。
对比例2
对比例2与实施例2的区别在于，未加入Na2C2O4进行烧结。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3包覆层的Li(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为118cm-1。
对比例3
对比例3与实施例4的区别在于，未加入Na2C2O4进行烧结。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3包覆层的Li(Ni0.5Mn0.5)0.98Nb0.02O1.8F0.2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为126cm-1。
对比例4
对比例4与实施例2的区别在于，烧结温度为600℃。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3包覆层的Li0.9Na0.1(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为65cm-1。
对比例5
对比例5与实施例2的区别在于，未加入LiF进行烧结。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3包覆层的Li0.9Na0.1(Ni0.4Mn0.6)0.98Nb0.02O2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为121cm-1。
对比例6
对比例6与实施例2的区别在于，未加入Nb2O5进行烧结。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3包覆层的Li0.9Na0.1Ni0.4Mn0.6O1.8F0.2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为125cm-1。
对比例7
对比例7与实施例2的区别在于，以Li0.9Na0.1(Ni0.4Mn0.6)0.8Nb0.1Al0.1O1.8F0.2的化学计量比为基准，将Ni0.4Mn0.6(OH)2与Li2CO3、LiF、Na2C2O4、Nb2O5进行混合烧结。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3包覆层的Li0.9Na0.1(Ni0.4Mn0.6)0.8Nb0.1Al0.1O1.8F0.2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为128cm-1。
对比例8
对比例8与实施例2的区别在于，以Li0.7Na0.3(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.2的化学计量比为基准，将Ni0.4Mn0.6(OH)2与Li2CO3、LiF、Na2C2O4、Nb2O5进行混合烧结。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3包覆层的Li0.7Na0.3(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为126cm-1。
对比例9
对比例9与实施例2的区别在于，以Li0.98Na0.02(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.2的化学计量比为基准，将Ni0.4Mn0.6(OH)2与Li2CO3、LiF、Na2C2O4、Nb2O5进行混合烧结。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3包覆层的Li0.98Na0.02(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为118cm-1。
对比例10
对比例10与实施例2的区别在于，以Li0.9Na0.1(Ni0.4Mn0.6)0.98Nb0.02O1.5F0.5的化学计量比为基准，将Ni0.4Mn0.6(OH)2与Li2CO3、LiF、Na2C2O4、Nb2O5进行混合烧结。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3包覆层的Li0.9Na0.1(Ni0.4Mn0.6)0.98Nb0.02O1.5F0.5。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为116cm-1。
对比例11
对比例11与实施例2的区别在于，以Li1.1Na0.1(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.2的化学计量比为基准，将Ni0.4Mn0.6(OH)2与Li2CO3、LiF、Na2C2O4、Nb2O5进行混合烧结。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3包覆层的Li1.1Na0.1(Ni0.4Mn0.6)0.98Nb0.02O1.8F0.2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为73cm-1，这是由于锂配比过高，导致材料更快的由无序向有序态过度，因此在相同的烧结条件下，无序度显著降低。
对比例12
对比例12与实施例2的区别在于，以Li0.9Na0.1(Ni0.4Mn0.6)1Nb0.02O1.8F0.2 的化学计量比为基准，将Ni0.4Mn0.6(OH)2与Li2CO3、LiF、Na2C2O4、Nb2O5进行混合烧结。
结合EDS能谱和ICP分析可知，制得的正极活性材料为具有Al2O3包覆层的Li0.9Na0.1(Ni0.4Mn0.6)1Nb0.02O1.8F0.2。根据拉曼光谱分析可知，制得的正极活性材料中Ni-O键与Mn-O键的峰位差约为116cm-1。
其中，实施例1至实施例15和对比例1至对比例12制得的正极活性材料的ICP分析结果如表1所示，表1为正极活性材料中各元素的质量分数(其余为氧元素的质量分数)，且各元素的质量分数与氧元素的质量分数之和为100％。
表1
根据表1，通过各元素质量占比进行相应的原子量占比换算，基于正极活性材料中各元素组成与理论成品元素的原子量配比差距均在±3％以内，可以证明制得的正极活性材料与设计值一致。
应用实施例
将实施例1至实施例15制得的正极活性材料依次用于制备二次电池样品1至样品15。
应用对比例
将对比例1至对比例12制得的正极活性材料依次用于制备二次电池样品16至样品27。
上述样品均采用相同的制备方法，具体步骤包括：将正极活性材料与导电剂Super-P、粘结剂PVDF按照质量比92:4:4混合，加入适量NMP溶液形成浆料，将其涂敷于铝箔上，干燥后于真空烘箱150℃烘烤12h，然后在Ar气气氛手套箱中进行二次电池装配，以金属锂作为负极，以1mol/L的LiPF6溶于体积比EC:EMC＝3:7的混合有机溶剂中作为电解液，装配成扣式CR2032电池。
采用恒流恒压充电+恒流放电充放电模式，以1C＝200mAg-1电流密度，在0.2C及0.5C两种电流密度下，于电压窗口2.5V-4.7V分别对样品1、样品2、样品16和样品17进行性能测试，测试结果如图5至图8所示。根据图5至图8可知，样品1和样品2的放电容量分别显著高于样品16和样品17。
采用恒流恒压充电+恒流放电充放电模式，以1C＝200mAg-1电流密度，在0.2C倍率下，于电压窗口2.5V-4.7V对样品1至样品27进行首圈充放电激活并进行倍率测试，随后于2.5V-4.5V，以0.5C进行100周循环测试，测试结果如表2所示，其中，首次库伦效率：用于量化锂离子电池负极材料的性能指标之一，定义为锂离子电池在首次充放电循环中放电容量与充电容量的比值；电池容量：在一定条件下(放电率、温度、终止电压等)电池放出的电量。
表2
根据表2可知，本申请提供的正极活性材料制得的二次电池不仅在高电压窗口兼具高比容量和高循环稳定性，在2.5V-4.7V、0.5C下循环100圈容量保持率高达约91％以上，而且成本较低，使其制得的二次电池具有高性价比。
对比例1至对比例3、对比例5至对比例10以及对比例12，由于Ni-O键与Mn-O键的峰位差大于110cm-1，材料的无序度过高，导致其界面副反应加重，并且制备的电极片压实密度下降，因此电池的稳定性下降、实用性较差；对比例4和对比例11由于Ni-O键与Mn-O键的峰位差小于80cm-1，材料的无序度过低，导致材料在高电压下的结构稳定性较差，功率性能显著下 降，因此电池在高倍率下容量发挥不足。
以上所述实施例的各技术特征可以进行任意的组合，为使描述简洁，未对上述实施例中的各个技术特征所有可能的组合都进行描述，然而，只要这些技术特征的组合不存在矛盾，都应当认为是本说明书记载的范围。
以上所述实施例仅表达了本申请的几种实施方式，其描述较为具体和详细，但并不能因此而理解为对申请专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本申请构思的前提下，还可以做出若干变形和改进，这些都属于本申请的保护范围。因此，本申请专利的保护范围应以所附权利要求为准。

Claims (32)

  1. 一种正极活性材料，其中，所述正极活性材料的组成化学式为LixNa1-xAyB1-yO2-nDn，其中，A选自Ni和Mn的组合物，B选自除Ni、Mn、Co、S之外的至少一种非碱金属正价元素，D选自F和/或S，0.8≤x≤0.92，0.90≤y＜1.0，0＜n≤0.2，所述正极活性材料在拉曼光谱中Ni-O键与Mn-O键的峰位差大于80cm-1且小于110cm-1。
  2. 根据权利要求1所述的正极活性材料，其中，Ni与Mn的摩尔比为3:7-1:1。
  3. 根据权利要求1或权利要求2所述的正极活性材料，其中，B选自Mg、Al、Zr、Ce、Cr、La、P、Ti、Ta、Nb、W、Mo、Te中的至少一种。
  4. 根据权利要求1-3任一项所述的正极活性材料，其中，所述B以掺杂形式存在，选自Al、Cr、Ti中的至少一种。
  5. 根据权利要求1-3任一项所述的正极活性材料，其中，所述B以掺杂形式存在，选自Zr、La、P中的至少一种。
  6. 根据权利要求1-3任一项所述的正极活性材料，其中，所述B以掺杂形式存在，选自Ta、Nb、W、Mo、Te、Ce中的至少一种。
  7. 根据权利要求1-3任一项所述的正极活性材料，其中，所述B选自+5价及以上的高价元素。
  8. 根据权利要求1-7任一项所述的正极活性材料，其中，B至少包括Nb或者Mo，D至少包括F。
  9. 根据权利要求1-8任一项所述的正极活性材料，其中，所述正极活性材料的晶体结构为锂化尖晶石-层状复合型晶体结构。
  10. 根据权利要求9所述的正极活性材料，其中，所述正极活性材料的晶体结构表面还具有包覆层，所述包覆层选自惰性氧化物包覆层、含锂过渡金属氧化物包覆层、磷酸盐包覆层、氟化物包覆层中的至少一种。
  11. 根据权利要求10所述的正极活性材料，其中，当所述正极活性材料在拉曼光谱中Ni-O键与Mn-O键的峰位差小于110cm-1且大于100cm-1时，所述包覆层选自惰性氧化物包覆层、磷酸盐包覆层、氟化物包覆层中的至少一种。
  12. 根据权利要求10所述的正极活性材料，其中，当所述正极活性材料在拉曼光谱中Ni-O键与Mn-O键的峰位差大于80cm-1，小于或等于100cm-1时，所述包覆层选自含锂过渡金属氧化物包覆层。
  13. 根据权利要求10-12任一项所述的正极活性材料，其中，所述包覆层的包覆量为所述正极活性材料质量的0.5wt％-1wt％。
  14. 根据权利要求10-13任一项所述的正极活性材料，其中，所述惰性氧化物包覆层选自Al2O3与TiO2的复合物。
  15. 根据权利要求10所述的正极活性材料，其中，所述含锂过渡金属氧化物包覆层选自Li1+aZrO2+a，其中，0＜a≤1.0。
  16. 根据权利要求10-15任一项所述的正极活性材料，其中，所述氟化物包覆层选自MgF2。
  17. 一种如权利要求1至权利要求16任一项所述的正极活性材料的制备方法，其中，包括如下步骤：
    制备Ni、Mn复合金属盐前驱体；
    以LixNa1-xAyB1-yO2-nDn，0.8≤x≤0.92，0.90≤y＜1.0，0＜n≤0.2为基准，将所述Ni、Mn复合金属盐前驱体与锂盐、钠盐以及含有除Ni、Mn、Co、S之外任意一种非碱金属正价元素的无机盐混合，得到混合物，其中，所述锂盐、所述钠盐、所述无机盐中的至少一种含有负价元素D，D选自F和/或S；
    将所述混合物于300℃-500℃进行烧结，得到正极活性材料。
  18. 根据权利要求17所述的正极活性材料的制备方法，其中，所述Ni、Mn复合金属盐前驱体中Ni与Mn的摩尔比为3:7-1:1。
  19. 根据权利要求17或18所述的正极活性材料的制备方法，其中，所述锂盐中锂的摩尔量相对于基准过量5mol％以内。
  20. 根据权利要求17-19任一项所述的正极活性材料的制备方法，其中，所述烧结的时间为10h-30h。
  21. 根据权利要求17-20任一项所述的正极活性材料的制备方法，其中，所述锂盐选自碳酸锂、氢氧化锂、草酸锂、硝酸锂、氟化锂中的至少两种。
  22. 根据权利要求17-21任一项所述的正极活性材料的制备方法，其中，所述钠盐选自碳酸钠、草酸钠、硫化钠中的至少一种。
  23. 根据权利要求21所述的正极活性材料的制备方法，其中，所述锂盐选自碳酸锂与草酸锂的组合物时，所述碳酸锂与所述草酸锂的摩尔比为1:2-2:1。
  24. 根据权利要求17-23任一项所述的正极活性材料的制备方法，其中，在将所述混合物于300℃-500℃烧结10h-30h之后，还包括包覆处理，所述包覆处理的温度为300℃-400℃。
  25. 根据权利要求24所述的正极活性材料的制备方法，其中，所述烧结温度为350℃-400℃。
  26. 根据权利要求24所述的正极活性材料的制备方法，其中，所述烧结温度为400℃-450℃。
  27. 根据权利要求24-26任一项所述的正极活性材料的制备方法，其中，所述烧结时间为15h-25h。
  28. 根据权利要求24-26任一项所述的正极活性材料的制备方法，其中，当烧结物表面残留锂时，通过包覆处理将残锂直接进行含锂过渡金属氧化物的包覆。
  29. 一种正极片，其中，包括正极集流体以及设置于所述正极集流体表面的正极材料层，所述正极材料层包括如权利要求1至权利要求16任一项所述的正极活性材料。
  30. 根据权利要求29任一项所述的正极片，其中，所述正极材料层还包括导电剂和粘结剂。
  31. 一种二次电池，其中，包括如权利要求29或30所述的正极片。
  32. 根据权利要求31所述的二次电池，其中，还包括负极片、隔膜以及电解液。
PCT/CN2023/122870 2023-07-04 2023-09-28 正极活性材料及其制备方法、正极片和二次电池 Ceased WO2025007438A1 (zh)

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