Positive electrode material for lithium-ion battery and preparation method therefor, positive electrode sheet, and lithium-ion battery

Abstract

A positive electrode material for a lithium-ion battery and a preparation method therefor, a positive electrode sheet, and a lithium-ion battery. The positive electrode material has a chemical formula of LiNi1-x-yCoxMyM'bO2, wherein 0<x≤0.3, 0<y≤0.4, 0≤b≤0.05, M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga and Al, and M' is selected from one or more of Zr, Ti, Zn, Mg, Mo, V, Ga and Al. An X-ray diffraction pattern of the positive electrode material has a diffraction peak (108) at a diffraction angle 2θ of 64±0.5° and a diffraction peak (110) at a diffraction angle 2θ of 65±0.5°; and the diffraction peak (108) and the diffraction peak (110) satisfy: formula (I).

Description

A positive electrode material for lithium ion battery and preparation method thereof, positive electrode sheet, and lithium ion battery Technical Field

[0001] The present application belongs to the field of energy storage technology, and specifically relates to a positive electrode material for a lithium-ion battery and a preparation method thereof, a positive electrode sheet, and a lithium-ion battery. Background Art

[0002] As the main material of lithium-ion batteries, the performance of lithium-ion battery positive electrode materials is one of the key factors affecting the energy density of lithium-ion batteries. Lithium-ion battery positive electrode materials are generally lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide and lithium nickel cobalt manganese oxide (ternary materials). Among them, lithium nickel cobalt manganese oxide combines the advantages of lithium manganese oxide, lithium cobalt oxide and lithium nickel oxide, with high specific capacity, good discharge rate and excellent cycle performance. It is one of the main directions of positive electrode material technology development and is also a core material that affects the performance, application scenarios and market potential of lithium-ion batteries.

[0003] To meet market demand for lithium-ion batteries and further enhance the specific capacity and cycle performance of ternary materials, existing technologies typically optimize ternary materials through surface coating, element doping, and increasing nickel content. The introduction of new elements or changes in the atomic ratios within a ternary material will affect its internal atomic arrangement and layered order, and the atomic arrangement and layered order within the ternary material's crystal structure will affect its lithium storage performance. Therefore, rationally controlling the atomic arrangement and layered order of ternary materials to prepare high-performance ternary materials is of great research significance and value.

[0004] Summary of the Invention

[0005] The purpose of this application is to provide a positive electrode material for lithium ion batteries and a preparation method thereof, a positive electrode sheet, and a lithium ion battery, so as to obtain a high-performance positive electrode material for lithium ion batteries by rationally controlling the atomic arrangement and layered order inside the positive electrode material.

[0006] In order to solve the above problems, the present application provides a positive electrode material for lithium ion batteries, the positive electrode material chemical formula of which is LiNi 1-x-y Co x M y M' b O2, wherein 0 < x ≤ 0.3, 0 < y ≤ 0.4, 0 ≤ b ≤ 0.05, M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga and Al, and M' is selected from one or more of Zr, Ti, Zn, Mg, Mo, V, Ga and Al;

[0007] In the X-ray diffraction spectrum of the positive electrode material, there are a (108) diffraction peak at a diffraction angle 2θ of (64±0.5)° and a (110) diffraction peak at a diffraction angle 2θ of (65±0.5)°;

[0008] The (108) diffraction peak and the (110) diffraction peak satisfy:

[0009] Wherein, FWHM(108) is the half-maximum width of the (108) diffraction peak at a diffraction angle of 2θ = (64 ± 0.5)°;

[0010] FWHM(110) is the half-maximum width of the (110) diffraction peak at a diffraction angle of 2θ=(65±0.5)°.

[0011] In some embodiments, the positive electrode material is a polycrystalline ternary material; the positive electrode material chemical formula is LiNi 1-x-y Co x M y M' b O2, wherein 0.1≤x≤0.2, 0.1≤y≤0.35, 0<b≤0.05, M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga and Al; M' is selected from one or more of Zr, Ti, Zn, Mg, Mo, V, Ga and Al.

[0012] In some embodiments, the (108) diffraction peak and the (110) diffraction peak satisfy:

[0013] In some embodiments, the (108) diffraction peak and the (110) diffraction peak satisfy:

[0014] In some embodiments, in the X-ray diffraction spectrum of the positive electrode material, the half-maximum width FWHM (108) of the (108) diffraction peak at a diffraction angle 2θ of (64±0.5)° ranges from 0.1 to 0.3.

[0015] In some embodiments, in the X-ray diffraction spectrum of the positive electrode material, the half maximum width FWHM (110) of the (110) diffraction peak at a diffraction angle 2θ of (65±0.5)° is in the range of 0.1 to 0.3.

[0016] In some embodiments, the positive electrode material has an α-NaFeO2 layered structure.

[0017] In a second aspect, the present application provides a method for preparing the above-mentioned positive electrode material for lithium-ion batteries, comprising the following steps:

[0018] Dispersing a lithium-containing compound, a soluble metal salt, cobalt acetate, nickel acetate, and a doping metal salt in a solvent to obtain a dispersed solution, adding a pH adjuster to the dispersed solution to adjust the pH of the dispersed solution to 7-8, and drying to obtain a precursor material; sequentially subjecting the precursor material to a first sintering, a first cooling, a second sintering, and a second cooling to obtain the positive electrode material;

[0019] The first sintering comprises the following steps: sintering the precursor material in an air atmosphere at a first sintering temperature of 300° C. to 600° C. for a first sintering time of 3 h to 6 h, and performing a first cooling after the first sintering is completed;

[0020] The second sintering comprises the following steps: after the first cooling is completed, performing a second sintering in a pure oxygen atmosphere, the second sintering temperature is 700° C. to 950° C., the second sintering time is 8 hours to 15 hours, and performing a second cooling after the second sintering is completed.

[0021] In some embodiments, the soluble metal salt and the doping metal salt both include one or more of manganese acetate, titanium acetate, zinc acetate, magnesium acetate, molybdenum acetate, vanadium acetate, germanium acetate, aluminum acetate, zirconium acetate, manganese nitrate, titanium nitrate, zinc nitrate, magnesium nitrate, molybdenum nitrate, vanadium nitrate, germanium nitrate, aluminum nitrate, zirconium nitrate, manganese hydroxide, titanium hydroxide, zinc hydroxide, magnesium hydroxide, molybdenum hydroxide, vanadium hydroxide, germanium hydroxide, aluminum hydroxide, and zirconium hydroxide;

[0022] The lithium-containing compound includes one or more of lithium hydroxide, lithium nitrate, lithium carbonate, lithium acetate, lithium chloride, lithium fluoride, and lithium iodide;

[0023] The solvent includes one or more of deionized water, ethanol, methanol, isopropanol, n-butanol, octanol, and decanol.

[0024] In some embodiments, the lithium compound, soluble metal salt, nickel acetate, cobalt acetate and doping metal salt are in a metal element molar ratio of (1-1.2):y:1-xy:x:b, wherein 0<x≤0.3, 0<y≤0.4, 0<b≤0.05.

[0025] In some embodiments, the concentration of the pH adjuster is 1 mol / L to 3 mol / L, and the pH adjuster includes one or more of citric acid, acetic acid, oxalic acid, benzoic acid, acrylic acid, carboxylated graphene, and carboxylated graphite.

[0026] In some embodiments, in the step of drying to obtain the precursor material, the drying method is one or more of spray drying, flash evaporation, stirring drying, and dynamic drying.

[0027] In some embodiments, the heating rate in the first sintering is 1-8°C / min, the first cooling temperature is 20-30°C, and the cooling method is quenching, and the material after the first sintering is directly transferred to room temperature;

[0028] The heating rate in the second sintering is 1-8°C / min, the second cooling temperature is 20-30°C, and the cooling method is quenching, and the material after the second sintering is directly transferred to room temperature.

[0029] In a third aspect, the present application provides a positive electrode sheet, comprising the positive electrode material for lithium-ion batteries described above, or the positive electrode material prepared by the method for preparing the positive electrode material for lithium-ion batteries described above.

[0030] In some embodiments, the compaction density of the positive electrode sheet is 3 to 3.7 g / cm 3 .

[0031] In a fourth aspect, the present application provides a positive electrode sheet, comprising a positive electrode material, wherein the chemical formula of the positive electrode material is Li z Ni 1-x-y Co x M y M' b O2, wherein 0 < x ≤ 0.3, 0 < y ≤ 0.4, 0 ≤ b ≤ 0.05, M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga and Al, and M' is selected from one or more of Zr, Ti, Zn, Mg, Mo, V and Ga;

[0032] The X-ray diffraction spectrum of the positive electrode sheet has a (108) diffraction peak at a diffraction angle 2θ of (64±0.5)° and a (110) diffraction peak at a diffraction angle 2θ of (65±0.5)°;

[0033] The (108) diffraction peak and the (110) diffraction peak satisfy:

[0034] Wherein, FWHM(108) is the half-maximum width of the (108) diffraction peak at a diffraction angle of 2θ = (64±0.5)°; FWHM(110) is the half-maximum width of the (110) diffraction peak at a diffraction angle of 2θ = (65±0.5)°.

[0035] In a fifth aspect, the present application provides a lithium-ion battery comprising the positive electrode sheet described above.

[0036] The lithium-ion battery positive electrode material provided in the present application has an X-ray diffraction spectrum in which a diffraction angle 2θ of (65±0.5)° and a diffraction peak (110) and a diffraction angle 2θ of (64±0.5)° respectively satisfy the following conditions: Satisfying this relationship can ensure that the material has good layered structural order and reasonable atomic arrangement, so that the prepared positive electrode material has higher mass specific capacity and cycle performance.

[0037] The lithium-ion battery positive electrode sheet provided in the present application has a positive electrode material structure that remains intact during the rolling process. That is, the positive electrode sheet has a (110) diffraction peak at a diffraction angle 2θ of (65±0.5)° and a (108) diffraction peak at a diffraction angle 2θ of (64±0.5)°, which satisfies: A lithium-ion battery containing the positive electrode sheet has a higher cycle life. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG1 is an XRD pattern of the positive electrode material prepared in Example 1;

[0039] FIG2 is an XRD pattern of the positive electrode material prepared in Example 2;

[0040] FIG3 is an XRD pattern of the positive electrode material prepared in Example 3;

[0041] FIG4 is an XRD pattern of the positive electrode material prepared in Example 4;

[0042] FIG5 is a comparison of XRD patterns of positive electrode materials of Example 1 and Example 1; DETAILED DESCRIPTION

[0043] In order to make the technical problems, technical solutions and beneficial effects solved by this application more clearly understood, this application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0044] As shown in Figures 1-4, the present invention provides a positive electrode material for lithium-ion batteries. The positive electrode material has the chemical formula LiNi 1-x-y Co x M y M' b O2, wherein 0<x≤0.3, 0<y≤0.4, 0≤b≤0.05, M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga and Al, and M' is selected from one or more of Zr, Ti, Zn, Mg, Mo, V, Ga and Al; in the X-ray diffraction spectrum of the positive electrode material, there is a (108) diffraction peak at a diffraction angle 2θ of (64±0.5)° and a (110) diffraction peak at a diffraction angle 2θ of (65±0.5)°;

[0045] The (108) diffraction peak and the (110) diffraction peak satisfy:

[0046] Wherein, FWHM(108) is the half-maximum width of the (108) diffraction peak at a diffraction angle of 2θ = (64 ± 0.5)°;

[0047] FWHM(110) is the half-maximum width of the (110) diffraction peak at a diffraction angle of 2θ=(65±0.5)°.

[0048] Lithium nickel cobalt manganese oxide (ternary material) combines the advantages of lithium manganese oxide, lithium cobalt oxide, and lithium nickel oxide, and is widely used as a positive electrode material in lithium-ion batteries. Ternary materials have a hexagonal layered structure, with transition metal ions and lithium ions alternately occupying their octahedral voids in a layered arrangement. This atomic arrangement gives ternary materials superior electrochemical properties. Lithium ions can freely intercalate and deintercalate between layers to achieve energy storage. However, during the intercalation and deintercalation process of lithium ions, the crystal structure inside the ternary material will change to varying degrees. For example, the interlayer atoms will be rearranged, and changes in the order of the layered structure will have a direct impact on the performance of the material.

[0049] Since the ternary material is a hexagonal crystal system, and the (110) crystal plane is related to the a and b axes, the unit cell parameter a is related to the (110) crystal plane spacing; while the (108) crystal plane spacing is strongly correlated with the unit cell parameter c; and thus the distance relationship between the (110) crystal plane and the (108) crystal plane will affect the layered order of the ternary material. At the same time, the half-peak width in the XRD spectrum of the (110) crystal plane and the (108) crystal plane will also directly or indirectly reflect the arrangement order of the atoms in the corresponding layered lattice. After extensive research, the inventors found that when the diffraction peak corresponding to the (108) crystal plane of the ternary material and the diffraction peak corresponding to the (110) crystal plane meet the following conditions: It can not only determine the orderliness of the layered structure of ternary materials, but also evaluate the rationality of the atomic arrangement between layers. At the same time, it can ensure that the positive electrode material (i.e., ternary material) has good layered structural order and reasonable atomic arrangement, so that the positive electrode material has a higher specific capacity and improves the battery cycle life.

[0050] Specifically, in the relationship, 2θ(110) refers to the specific position of the (110) diffraction peak at a diffraction angle 2θ of (65±0.5)° in the X-ray diffraction spectrum actually obtained when the positive electrode material is subjected to XRD testing. Generally, the value range of 2θ(110) is (65±0.5)°. Similarly, 2θ(108) refers to the specific position of the (108) diffraction peak at a diffraction angle 2θ of (64±0.5)° in the X-ray diffraction spectrum actually obtained when the positive electrode material powder is subjected to XRD testing.

[0051] In some embodiments, the positive electrode material is a polycrystalline ternary material; the positive electrode material chemical formula is LiNi 1-x-y Co x M y M' b O2, wherein 0.1≤x≤0.2, 0.1≤y≤0.35, 0<b≤0.05, M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga and Al; M' is selected from one or more of Zr, Ti, Zn, Mg, Mo, V, Ga and Al.

[0052] In some embodiments, the positive electrode material chemical formula is LiNi 1-x-y Co x M y M' b O2, wherein 0.1≤x≤0.2, 0.1≤y≤0.3, 0<b≤0.05, M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga and Al; M' is selected from one or more of Zr, Ti, Zn, Mg, Mo, V, Ga and Al.

[0053] As the Ni content in the positive electrode material increases, the mass specific capacity of the ternary material will increase significantly; however, as the Ni content in the positive electrode material increases, the content of each atom in the ternary material changes, and the risk of lithium-nickel mixing also increases, resulting in a decrease in its cycle life. Therefore, when the above relationship is met, the layered structure of the high-nickel positive electrode material can be guaranteed to have a high degree of order, and the positive electrode material has a high specific capacity and cycle life.

[0054] In some embodiments, the positive electrode material chemical formula is LiNi 1-x-y Co x M y M' b O2, wherein 0.1≤x≤0.3, 0.1≤y≤0.3, 0<b≤0.05, M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga and Al; M' is selected from one or more of Zr, Ti, Zn, Mg, Mo, V, Ga and Al.

[0055] In some embodiments, the (108) diffraction peak and the (110) diffraction peak satisfy:

[0056] In some embodiments, the (108) diffraction peak and the (110) diffraction peak satisfy:

[0057] When the relationship is within the above preferred range, the layered structure of the positive electrode material layer is highly ordered, the atomic arrangement between the layers is also highly stable, the specific capacity of the positive electrode material is high, and the cycle performance of the lithium-ion battery is better.

[0058] In some embodiments, in the X-ray diffraction spectrum of the positive electrode material, the half maximum width FWHM (108) of the (108) diffraction peak at a diffraction angle 2θ of (64±0.5)° is in the range of 0.1 to 0.3.

[0059] Specifically, the half-maximum width (FWHM) (108) of the (108) diffraction peak at a diffraction angle 2θ of (64±0.5)° refers to the half-maximum width of the (108) diffraction peak at the half-maximum height position of the (108) diffraction peak, which is parallel to the horizontal axis of the diffraction angle 2θ in the X-ray diffraction spectrum. The FWHM (108) range is between 0.1 and 0.3 and satisfies: The positive electrode material has good layered structure order and high specific capacity.

[0060] In some embodiments, in the X-ray diffraction spectrum of the positive electrode material, the half maximum width FWHM (110) of the (110) diffraction peak at a diffraction angle 2θ of (65±0.5)° is in the range of 0.1 to 0.3.

[0061] Specifically, the half-maximum width (FWHM) (110) of the (110) diffraction peak at a diffraction angle 2θ of (65±0.5)° refers to the half-maximum width of the (110) diffraction peak at the half-maximum height position of the (110) diffraction peak, which is parallel to the horizontal axis of the diffraction angle 2θ in the X-ray diffraction spectrum. The FWHM (110) range is between 0.1 and 0.3 and satisfies the following conditions: The positive electrode material has good layered structure order and high specific capacity.

[0062] In some embodiments, the positive electrode material has an α-NaFeO2 layered structure.

[0063] It is understood that the X-ray diffraction spectrum of the positive electrode material in the present application can be obtained by scanning with a copper target X-ray generator at 10° to 80° at a scanning rate of 6° / min.

[0064] In a second aspect, the present application provides a method for preparing a positive electrode material for a lithium-ion battery, comprising the following steps: dispersing a lithium-containing compound, a soluble metal salt, cobalt acetate, nickel acetate, and a doping metal salt in a solvent to obtain a dispersed solution; adding a pH adjuster to the dispersed solution to adjust the pH of the dispersed solution to 7 to 8; and drying to obtain a precursor material; the spherical precursor material is sequentially subjected to a first sintering, a first cooling, a second sintering, and a second cooling to obtain the positive electrode material;

[0065] The first sintering comprises the following steps: sintering the precursor material in an air atmosphere at a first sintering temperature of 300° C. to 600° C. for a first sintering time of 3 h to 6 h, and performing a first cooling after the first sintering is completed;

[0066] The second sintering comprises the following steps: after the first cooling is completed, performing a second sintering in a pure oxygen atmosphere, the second sintering temperature is 700° C. to 950° C., the second sintering time is 8 hours to 15 hours, and performing a second cooling after the second sintering is completed.

[0067] The preparation method of the positive electrode material for lithium-ion batteries provided by the present application has the following effects compared with the existing technology: (1) The present application is a one-step method for preparing a spherical precursor material. The mixing process is uniform, no waste liquid is generated, it is green and clean, and the preparation process is simple and controllable. The spherical precursor material obtained after drying is evenly dispersed and has a regular surface morphology. Compared with other synthesis methods, the precursor material prepared by the present application can improve the compaction density of the positive electrode sheet. (2) The pH regulator added during the precursor preparation process makes the obtained precursor have an organic coating, and no secondary coating is required. The residual carbon content of the finished positive electrode material obtained after sintering is 0.1%wt~3%wt. (3) Two sintering steps are used to crystallize the finished product and carbonize the coating layer. Two cooling steps are used to control the grain size of the intermediate product so that the grains of the material can quickly stabilize at a fixed size, which is beneficial to improving the compaction density of the positive electrode material. At the same time, it can also avoid the generation of other impurities and improve the orderliness of the layered structure of the positive electrode material. The two-step sintering and cooling method saves the cooling time of the sintering equipment, shortens the process time, and is also beneficial to obtaining a highly ordered layered structure positive electrode material, so that the positive electrode material has a higher specific capacity.

[0068] In some embodiments, the soluble metal salt and the doping metal salt both include one or more of manganese acetate, titanium acetate, zinc acetate, magnesium acetate, platinum acetate, vanadium acetate, germanium acetate, aluminum acetate, zirconium acetate, manganese nitrate, titanium nitrate, zinc nitrate, magnesium nitrate, molybdenum nitrate, vanadium nitrate, germanium nitrate, aluminum nitrate, zirconium nitrate, manganese hydroxide, titanium hydroxide, zinc hydroxide, magnesium hydroxide, molybdenum hydroxide, vanadium hydroxide, germanium hydroxide, zirconium hydroxide, and aluminum hydroxide;

[0069] The lithium-containing compound includes one or more of lithium hydroxide, lithium nitrate, lithium carbonate, lithium acetate, lithium chloride, lithium fluoride, and lithium iodide;

[0070] The solvent includes one or more of deionized water, ethanol, methanol, isopropanol, n-butanol, octanol, and decanol.

[0071] In the process of preparing the spherical precursor material, adding a soluble metal salt is conducive to dissolving in the solvent, accelerating the dispersion speed and improving the mixing uniformity of the mixture.

[0072] For example, when the solvent is water, soluble metal salts such as manganese acetate, aluminum acetate, aluminum nitrate, etc. can all be dissolved in water.

[0073] In some embodiments, the lithium-containing compound is lithium hydroxide.

[0074] In some embodiments, the lithium-containing compound, soluble metal salt, nickel acetate, cobalt acetate and doping metal salt are in a metal element molar ratio of (1-1.2):y:1-xy:x:b, wherein 0<x≤0.3, 0<y≤0.4, 0≤b≤0.05.

[0075] Specifically, the lithium-containing compound, the soluble metal salt, the nickel acetate and the cobalt acetate are controlled in a metal element molar ratio of (1-1.2):y:1-xy:x to prepare a LiNi 1-x-y Co x M y O2 positive electrode material, wherein 0<x≤0.3, 0<y≤0.4, M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga and Al. The lithium compound, soluble metal salt, nickel acetate, cobalt acetate and doping metal salt are controlled to contain the metal element molar ratio of (1~1.2):y:1-xy:x:b, and the positive electrode material doped with the metal element M' can be prepared, that is, the chemical formula is LiNi 1-x-y Co x M y M' b O2, wherein 0<x≤0.3, 0<y≤0.4, 0≤b≤0.05, M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga and Al, and M' is selected from one or more of Zr, Ti, Zn, Mg, Mo, V, Ga and Al.

[0076] In some embodiments, the concentration of the pH adjuster is 1 mol / L to 3 mol / L, and the pH adjuster includes but is not limited to one or more of citric acid, acetic acid, oxalic acid, benzoic acid, acrylic acid, carboxylated graphene, and carboxylated graphite.

[0077] Specifically, a pH regulator is added during the preparation of the spherical precursor material. The obtained spherical precursor material is an organic coating and does not require a second coating, thereby saving costs and shortening process time. At the same time, the residual carbon content of the finished positive electrode material after sintering the spherical precursor material is in the range of 0.1%wt to 3%wt.

[0078] In some embodiments, the regulator is citric acid. Citric acid is a carbon-containing compound. By using citric acid to adjust the pH of the solution, the resulting quasi-spherical precursor material is also an organic coating, eliminating the need for a second coating, saving costs and shortening process time. Furthermore, the residual carbon content of the finished cathode material after sintering the quasi-spherical precursor material ranges from 0.1% wt to 3% wt.

[0079] If the residual carbon content of the positive electrode material is too low, the conductivity of the positive electrode material will decrease, increasing the battery impedance; if the residual carbon content of the positive electrode material is higher than 3%wt, the carbon content per unit mass of the positive electrode material is too high, the active lithium ion content is relatively reduced, and the energy density of the battery is reduced.

[0080] In some embodiments, the lithium hydroxide, manganese acetate, nickel acetate, and cobalt acetate are in a metal element molar ratio of 1.02:y:1-xy:x, wherein 0<x≤0.3, 0<y≤0.4.

[0081] In some embodiments, the lithium hydroxide, manganese acetate, nickel acetate, and cobalt acetate are in a metal element molar ratio of 1.02:y:1-xy:x, wherein 0<x≤0.2, 0<y≤0.2.

[0082] In some embodiments, the lithium hydroxide, manganese acetate, nickel acetate, cobalt acetate, and zirconium acetate are in a metal element molar ratio of 1.02:y:1-xy:x:b, wherein 0<x≤0.3, 0<y≤0.4, and 0≤b≤0.05.

[0083] In some embodiments, the molar ratio of the metal elements of lithium hydroxide, manganese acetate, nickel acetate, and cobalt acetate is 1.02:0.2:0.6:0.2.

[0084] In some embodiments, the molar ratio of the metal elements of lithium hydroxide, manganese acetate, nickel acetate, and cobalt acetate is 1.02:0.2:0.5:0.2.

[0085] In some embodiments, the molar ratio of the metal elements of lithium hydroxide, manganese acetate, nickel acetate, and cobalt acetate is 1.02:0.2:0.7:0.2.

[0086] In some embodiments, the molar ratio of the metal elements of lithium hydroxide, manganese acetate, nickel acetate, and cobalt acetate is 1.02:0.2:0.8:0.2.

[0087] In some embodiments, in the step of drying to obtain the spherical material precursor, the drying method is one or more of spray drying, flash evaporation, stirring drying, and dynamic drying. More preferably, the drying method is spray drying.

[0088] Specifically, dynamic drying includes reduced-pressure drying and freeze-drying. For example, when a precursor material prepared using drying methods such as spray drying and dynamic drying has a spherical or disc-like microstructure, it is considered a quasi-spherical precursor material. Furthermore, the precursor material can be uniformly dispersed and has a regular surface morphology.

[0089] In some embodiments, the specific steps of obtaining a spherical material precursor by spray drying are: spray drying the dispersion to obtain a spherical precursor material, and the specific parameters of spray drying are: feed rate 35 mL / min, air inlet temperature 150°C, and nozzle speed 240 rpm.

[0090] In some embodiments, the first sintering includes the following steps: sintering the spherical material precursor for the first time in an air atmosphere environment, the heating rate during the first sintering is 1-8°C / min, the first sintering temperature is 300°C~600°C, the first sintering time (or the first insulation time) is 3h~6h, and the first cooling is performed after the first sintering is completed. The first cooling temperature is 20-30°C, and the cooling method adopts sudden cooling, and the sintered material is directly transferred to room temperature.

[0091] Specifically, the air atmosphere environment refers to the atmospheric environment. The first sintering operation of the spherical precursor material helps to form a positive electrode material with good crystallinity, and at the same time carbonizes the organic coating layer of the spherical precursor material, improves the true density of the material, and adjusts the specific surface area of ​​the material. After the first sintering, the first cooling operation is carried out, the purpose of which is to control the grain size of the intermediate product, so that the grains of the material quickly stabilize at a fixed size, ensure the rapid crystallization of the material, avoid the generation of other miscellaneous products, and improve the orderliness of the layered structure of the material. Specifically, the first sintering temperature can be 300℃, 350℃, 380℃, 400℃, 430℃, 460℃, 500℃, 530℃, 550℃, 580℃, 600℃, etc., as long as the first sintering temperature is between 300℃ and 600℃.

[0092] In some embodiments, the spherical material precursor is sintered in an air atmosphere at a first sintering temperature of 300° C. for 3 hours, followed by a first cooling step.

[0093] In some embodiments, the second sintering includes the following steps: after the first sintering is completed, the second sintering is carried out in a pure oxygen atmosphere, the heating rate in the second sintering is 1-8°C / min, the second sintering temperature is 700°C~950°C, the second sintering time (or second insulation time) is 8h~15h, and the second cooling is carried out after the second sintering is completed. The second cooling temperature is 20-30°C, and the cooling method adopts sudden cooling, and the sintered material is directly transferred to room temperature.

[0094] Specifically, the pure oxygen atmosphere refers to a space filled with pure oxygen, and the second sintering is carried out in a space filled with pure oxygen. The first and second sintering processes have the same function, both of which help to form a positive electrode material with better crystallinity, while carbonizing the organic coating layer of the spherical precursor material, improving the material's density, and increasing the material's specific surface area. The first and second cooling processes also have the same function, which is to control the grain size of the intermediate product, so that the material grains quickly stabilize at a fixed size, increase the compaction density when the positive electrode material is prepared into a pole piece, and at the same time, ensure rapid crystallization of the material, avoid the generation of other impurities, and improve the orderliness of the material's layered structure. Specifically, the second sintering temperature can be 700°C, 730°C, 750°C, 790°C, 800°C, 820°C, 850°C, 870°C, 900°C, 930°C, 950°C, etc., as long as the second sintering temperature is between 700°C and 950°C.

[0095] In some embodiments, the spherical material precursor is sintered in a pure oxygen atmosphere at a second sintering temperature of 950° C. for 10 hours, followed by a second cooling step.

[0096] If the first sintering temperature is lower than 300°C, or the second sintering temperature is lower than 700°C, the crystallinity of the positive electrode material is low and the crystallization is not perfect, which affects the battery cycle performance. If the sintering temperature is too low, it is easy to cause incomplete material reaction and easily produce impurity phases; if the first sintering temperature is higher than 600°C, or the second sintering temperature is higher than 950°C, the particle size of the finished material particles is large, the lithium ion conduction path is too long, which affects the battery discharge capacity and internal resistance, and easily leads to too low carbon content.

[0097] It is understandable that the equipment selected for the first sintering and the second sintering includes one of a tube furnace, a box furnace, a fluidized bed, a rotary kiln, a microwave oven, and a tunnel furnace.

[0098] In some embodiments, the step of dispersing the lithium-containing compound, the soluble metal salt, the cobalt acetate and the nickel acetate in the solvent comprises at least one of ultrasound, mechanical stirring, magnetic stirring, high-energy ball milling, jar milling, high shear dispersion and high-pressure dispersion.

[0099] In a third aspect, the present application provides a positive electrode sheet, comprising the positive electrode material for lithium-ion batteries described above, or the positive electrode material prepared by the method for preparing the positive electrode material for lithium-ion batteries described above.

[0100] The positive electrode sheet provided in the present application contains the above-mentioned positive electrode material, has a high specific capacity, and the prepared battery has a good cycle life.

[0101] In some embodiments, the positive electrode sheet includes a positive electrode material having a chemical formula of LiNi 1-x-y Co x M y O2, wherein 0<x≤0.3, 0<y≤0.3, M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga and Al;

[0102] Or the positive electrode material chemical formula is LiNi 1-x-y Co x M y M' b O2, wherein 0<x≤0.3, 0<y≤0.4, 0<b≤0.05, M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga and Al; M' includes one or more of Zr, Ti, Zn, Mg, Mo, V, Ga.

[0103] The positive electrode sheet prepared by using the above positive electrode material is used in a battery, and the battery has high energy density, capacity and cycle life.

[0104] In some embodiments, the compaction density of the positive electrode sheet is 3 g / cm 3 ~3.7g / cm 3 .

[0105] Compared with the prior art, the positive electrode sheet prepared using the positive electrode material prepared in this application has a relatively complete layered structure and a high compaction density. When used in batteries, it can improve the cycle life of the battery.

[0106] In a fourth aspect, the present application provides a positive electrode sheet, comprising a positive electrode material, wherein the chemical formula of the positive electrode material is Li z Ni 1-x-y Co x M y M' b O2, wherein 0 < x ≤ 0.3, 0 < y ≤ 0.4, 0 < b ≤ 0.05, M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga and Al, and M' is selected from one or more of Zr, Ti, Zn, Mg, Mo, V and Ga;

[0107] The X-ray diffraction spectrum of the positive electrode sheet has a (108) diffraction peak at a diffraction angle 2θ of (64±0.5)° and a (110) diffraction peak at a diffraction angle 2θ of (65±0.5)°;

[0108] The (108) diffraction peak and the (110) diffraction peak satisfy:

[0109] Wherein, FWHM(108) is the half-maximum width of the (108) diffraction peak at a diffraction angle of 2θ = (64±0.5)°; FWHM(110) is the half-maximum width of the (110) diffraction peak at a diffraction angle of 2θ = (65±0.5)°.

[0110] The positive electrode sheet provided in the present application, in the X-ray diffraction spectrum of the positive electrode sheet, the (108) diffraction peak and the (110) diffraction peak satisfy: It not only ensures the integrity of the crystal structure of the positive electrode material in the positive electrode sheet and prevents damage to the positive electrode material during the production process, but also the lithium-ion battery with the positive electrode sheet that satisfies this relationship has better specific capacity and cycle life.

[0111] In a fifth aspect, the present application provides a lithium-ion battery comprising the positive electrode sheet described above.

[0112] The lithium-ion battery prepared using the positive electrode material of the present application or the positive electrode sheet obtained has a relatively complete layered structure of the positive electrode material and has a high specific capacity and cycle life.

[0113] The present application is further described in detail below through examples.

[0114] Example 1

[0115] This embodiment is used to illustrate the positive electrode material for lithium ion batteries and the preparation method thereof disclosed in this application, comprising the following steps:

[0116] Lithium hydroxide, manganese acetate, nickel acetate, cobalt acetate, and zirconium nitrate (dopant) were weighed at a metal element molar ratio of 1.03:0.35:0.50:0.15:0.003 and dispersed and dissolved using mechanical stirring to obtain a dispersed solution. A 1 mol / L citric acid solution was then added dropwise to the dispersed solution until the pH reached 8. The solution was then passed into a spray dryer at a feed rate of 35 mL / min, an air inlet temperature of 150°C, and a nozzle speed of 240 rpm. The dried powder was collected to obtain a spherical precursor material. The spherical precursor material is then sintered for the first time in an air atmosphere using a tube furnace, with a heating rate of 3°C / min, the temperature is raised to 300°C, and sintered at 300°C for 3 hours. It is then cooled for the first time, which is a sudden cooling, that is, the sintered material is directly placed at room temperature and cooled by air exchange, or the material is cooled by a rapid cooling program (the cooling rate is 50°C / min, cooling to 25°C); then the second sintering is carried out in a pure oxygen atmosphere, with a heating rate of 5°C / min, The temperature was raised to 950°C, and the material was sintered at a second sintering temperature of 950°C for 10 hours, followed by a second cooling, that is, the sintered material was directly placed at room temperature for cooling by air exchange, or the material was cooled by a rapid cooling program (cooling rate of 50°C / min, cooling to 25°C), to obtain a finished positive electrode material. The finished positive electrode material was subjected to XRD testing, using a copper target X-ray generator, scanning at a scanning rate of 6° / min from 10° to 80°, and finally obtaining the XRD spectrum shown in Figure 1.

[0117] Example 2

[0118] The difference between Example 2 and Example 1 is that the second sintering temperature is different, specifically as follows: the second sintering temperature is 850° C., and the rest of the preparation method is the same as that of Example 1.

[0119] Example 3

[0120] The difference between Example 3 and Example 1 is that the second sintering temperature and time in Example 3 are different. Specifically, the second sintering temperature is 950° C. and the sintering is carried out for 15 hours. The rest of the preparation method is the same as that of Example 1.

[0121] Example 4

[0122] The difference between Example 4 and Example 1 is that the second sintering temperature and time in Example 4 are different. Specifically, the second sintering temperature is 950° C. and the sintering is carried out for 6 hours. The rest of the preparation method is the same as that of Example 1.

[0123] Example 5

[0124] The difference between Example 5 and Example 1 is that the first sintering temperature is different. The first sintering temperature is 600° C. and the sintering is carried out for 3 hours. The rest is the same as Example 1.

[0125] Example 6

[0126] The difference between Example 6 and Example 1 is that the first sintering time is different. The first sintering temperature is 300° C. and the sintering is carried out for 6 hours. The rest is the same as Example 1.

[0127] Example 7

[0128] The difference between Example 7 and Example 1 is that the second sintering temperature is different. The second sintering temperature is 700° C. and the sintering is carried out for 10 hours. The rest is the same as Example 1.

[0129] Example 8

[0130] The difference between Example 8 and Example 1 is that no doping metal salt (zirconium acetate) is added to the reactants, the molar ratio of lithium hydroxide, manganese acetate, nickel acetate, and cobalt acetate metal elements is 1.03:0.35:0.50:0.15, and the rest are the same.

[0131] Example 9

[0132] The difference between Example 9 and Example 1 is that the molar ratio of the reactants is different, specifically, the molar ratio of the metal elements of lithium hydroxide, manganese acetate, nickel acetate, cobalt acetate, and zirconium acetate is 1.03:0.35:0.50:0.15:0.045, and the rest are the same.

[0133] Example 10

[0134] The difference between Example 10 and Example 1 is that the molar ratio of the reactants is different, specifically, the molar ratio of the metal elements of lithium hydroxide, manganese acetate, nickel acetate, cobalt acetate, and zirconium acetate is 1.03:0.35:0.50:0.15:0.02, and the rest are the same.

[0135] Example 11

[0136] The difference between Example 11 and Example 1 is that the molar ratio of the reactants is different, specifically, the molar ratio of the metal elements of lithium hydroxide, manganese acetate, nickel acetate, cobalt acetate, and zirconium acetate is 1.03:0.35:0.50:0.15:0.001, and the rest are the same.

[0137] Example 12

[0138] The difference between Example 12 and Example 1 is that the molar ratio of the reactants is different, specifically, the molar ratio of the metal elements of lithium hydroxide, manganese acetate, nickel acetate, cobalt acetate, and zirconium acetate is 1.02:0.28:0.60:0.22:0.01, and the rest are the same.

[0139] Comparative Example 1

[0140] The difference between Comparative Example 1 and Example 1 is that the second sintering conditions are different, specifically as follows: the second sintering is carried out in a pure air atmosphere, and the second sintering temperature is kept at 650° C. for 10 hours. The rest of the preparation method is the same as that of Example 1.

[0141] Comparative Example 2

[0142] The difference between Comparative Example 2 and Example 1 is that the first sintering temperature and time are different, specifically as follows: The first sintering temperature is 250° C. and the sintering is carried out for 3 hours. The rest of the preparation method is the same as that of Example 1.

[0143] Comparative Example 3

[0144] The difference between Comparative Example 3 and Example 1 is that the first sintering conditions are different, specifically as follows: the first sintering is carried out in a pure air atmosphere, and the first sintering temperature is kept at 650° C. for 3 hours. The rest of the preparation method is the same as that of Example 1.

[0145] Comparative Example 4

[0146] The difference between Comparative Example 4 and Example 1 is that the second sintering conditions are different, specifically as follows: the second sintering is carried out in a pure oxygen atmosphere, and the second sintering temperature is kept at 1100° C. for 10 hours. The rest of the preparation method is the same as that of Example 1.

[0147] Comparative Example 5

[0148] The difference between Comparative Example 5 and Example 1 is that the first cooling is not performed, and the atmosphere is directly changed to perform the second sintering in a pure oxygen atmosphere. The rest of the preparation method is the same as that of Example 1.

[0149] Comparative Example 6

[0150] The difference between Comparative Example 6 and Example 12 is that the second sintering conditions are different, specifically as follows: the second sintering is carried out in a pure oxygen atmosphere, and the second sintering temperature is kept at 650°C for 10 hours. The rest is the same as the preparation method of Example 12.

[0151] The carbon residue data of the positive electrode materials prepared in the above Examples 1-12 and Comparative Examples 1-6 were tested using a CS analyzer.

[0152] The specific data of FWHM(108), FWHM(110), 2θ(108), and 2θ(110) in the XRD spectra obtained after XRD testing of the positive electrode materials prepared in Examples 1-12 and Comparative Examples 1-6 are recorded in Table 1. The XRD half-peak width and peak position data are derived from the analysis of the XRD original test file by the processing software MDIJade 6. The specific data are shown in Table 1. The XRD spectra of the positive electrode materials prepared in Examples 1-4 are shown in Figures 1-4, and the XRD spectra comparison of the positive electrode materials prepared in Example 1 and Comparative Example 1 is shown in Figure 5.

[0153] Table 1 Partial data of positive electrode materials of Examples 1-16 and Comparative Examples 1-8

[0154] A positive electrode sheet S comprising the positive electrode materials of Examples 1, 4, 7, 10 and Comparative Examples 1 and 3 was selected, and the specific data of FWHM(108), FWHM(110), 2θ(108), and 2θ(110) in the XRD spectrum obtained after XRD testing of the above positive electrode sheet were recorded in Table 2. The XRD half-peak width and peak position data were derived from the analysis of the XRD original test file by the processing software MDIJade 6. The specific data are shown in Table 2.

[0155] Table 2 Positive electrode part data table

[0156] Performance testing:

[0157] The positive electrode materials prepared in the above Examples 1-12 and Comparative Examples 1-6 were used to prepare positive electrode sheets and batteries, and the following tests were performed.

[0158] Specific capacity test: The above cathode materials were mixed with PVDF and SP in a ratio of 96:3:1 using NMP as solvent for 2 hours to form a stable and uniform cathode slurry. The cathode slurry was coated on aluminum foil using a coating machine, dried, and cold pressed to obtain a compaction density of 3.0-3.70 g / cm 3 The positive electrode sheet was dried at 120°C for 24 hours. A lithium sheet was used as the negative electrode, a Cellgard 2300 porous membrane was used as the separator, and a 1 mol / L LiPF6 + DMC (volume ratio 1:1) mixed electrolyte was used as the electrolyte. A button cell 2032 was assembled and tested. Charge and discharge tests were performed at a 0.2C rate. The specific capacity of the third discharge test was taken as the specific capacity of the positive electrode material.

[0159] The positive electrode sheet compaction density test adopts the test method commonly used in this field.

[0160] Cycling performance test: Using deionized water as solvent, 95wt% of negative electrode active material graphite, 2wt% of binder SBR, 2wt% of conductive agent graphite and 1wt% of thickener CMC were added to deionized water to prepare negative electrode slurry. The negative electrode slurry was coated on copper foil, dried and cold pressed to obtain a compaction density of 1.6-1.7g / cm 3 .

[0161] Preparation of the battery: The positive electrode sheet, negative electrode sheet and separator prepared above are made into bare cells according to conventional preparation processes, and the bare cells are dried, injected with electrolyte, and packaged to finally make a battery.

[0162] Room temperature cycle performance test: The formed cells were subjected to a room temperature 25°C cycle test, with charge and discharge tests performed at 0.5C / 0.5C, and the number of charge and discharge cycles when the discharge capacity was maintained at 80% was recorded.

[0163] Table 2 Performance data of Examples 1-12 and Comparative Examples 1-6

[0164] By comparing Tables 1, 2, and Figures 1-5, it can be seen that when comparing Examples 1-12 with Comparative Examples 1-6, the X-ray diffraction spectra of the positive electrode materials in Comparative Examples 1-6 are: The value is greater than 0.75 or less than 0.5, the prepared positive electrode material has a low specific capacity and a short battery cycle life, indicating that the positive electrode material of the present application has a (108) diffraction peak at a diffraction angle 2θ of 64±0.5° and a (110) diffraction peak at a diffraction angle 2θ of 65±0.5° in its X-ray diffraction spectrum, and the (108) diffraction peak and the (110) diffraction peak meet The layered structure of the positive electrode material layer is highly ordered, the specific capacity of the positive electrode material is high, and the prepared battery has a long cycle life at room temperature.

[0165] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A cathode material for a lithium-ion battery, characterized in that The chemical formula of the positive electrode material is LiNi 1-x-y Co x M y M' b O2, where 0 < x ≤ 0.3, 0 < y ≤ 0.4, 0 ≤ b ≤ 0.05, M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga, and Al, and M' is selected from one or more of Zr, Ti, Zn, Mg, Mo, V, Ga, and Al; In the X-ray diffraction spectrum of the cathode material, there are (108) diffraction peaks at a diffraction angle 2θ of (64 ± 0.5)° and (110) diffraction peaks at a diffraction angle 2θ of (65 ± 0.5)°; The (108) diffraction peak and the (110) diffraction peak satisfy: wherein, FWHM(108) is the full width at half maximum of the (108) diffraction peak at a diffraction angle 2θ = (64 ± 0.5)°; FWHM(110) is the full width at half maximum of the (110) diffraction peak at a diffraction angle 2θ = (65 ± 0.5)°.

2. The cathode material for lithium-ion batteries according to claim 1, characterized in that, The positive electrode material is a polycrystalline ternary material; the chemical formula of the positive electrode material is LiNi 1-x-y Co x M y M' b O2, where 0.1 ≤ x ≤ 0.2, 0.1 ≤ y ≤ 0.35, 0 < b ≤ 0.05, M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga, and Al; M' is selected from one or more of Zr, Ti, Zn, Mg, Mo, V, Ga, and Al.

3. The cathode material for a lithium-ion battery according to claim 1 or 2, characterized in that, The (108) diffraction peak and the (110) diffraction peak satisfy:

4. The cathode material for a lithium-ion battery according to any one of claims 1-3, characterized in that, The (108) diffraction peak and the (110) diffraction peak satisfy:

5. The cathode material for lithium-ion batteries according to any one of claims 1-4, characterized in that, In the X-ray diffraction spectrum of the cathode material, the full width at half maximum FWHM(108) of the (108) diffraction peak at a diffraction angle 2θ of (64 ± 0.5)° ranges from 0.1 to 0.

3.

6. The cathode material for a lithium-ion battery according to any one of claims 1-5, characterized in that, In the X-ray diffraction spectrum of the cathode material, the full width at half maximum FWHM(110) of the (110) diffraction peak at a diffraction angle 2θ of (65 ± 0.5)° ranges from 0.1 to 0.

3.

7. The cathode material for a lithium-ion battery according to any one of claims 1-6, characterized in that, The cathode material has an α-NaFeO2 layered structure.

8. A method for preparing a cathode material for a lithium-ion battery according to any one of claims 1-7, characterized in that, It includes the following steps: Disperse a lithium-containing compound, a soluble metal salt, cobalt acetate, nickel acetate, and a doped metal salt in a solvent to obtain a dispersion solution, add a pH regulator to the dispersion solution to make the pH of the dispersion solution 7 to 8, and dry to obtain a precursor material; the precursor material is successively subjected to a first sintering, a first cooling, a second sintering, and a second cooling to obtain the cathode material; wherein, the first sintering includes the following steps: perform the first sintering on the precursor material in an air atmosphere environment, the first sintering temperature is 300°C to 600°C, the first sintering time is 3h to 6h, and perform the first cooling after the first sintering ends; The second sintering includes the following steps: after the first cooling ends, perform the second sintering in a pure oxygen atmosphere environment, the second sintering temperature is 700°C to 950°C, the second sintering time is 8h to 15h, and perform the second cooling after the second sintering ends.

9. The preparation method of the cathode material for lithium-ion batteries according to claim 8, wherein The soluble metal salt and the doped metal salt each include one or more of manganese acetate, titanium acetate, zinc acetate, magnesium acetate, molybdenum acetate, vanadium acetate, germanium acetate, aluminum acetate, zirconium acetate, manganese nitrate, titanium nitrate, zinc nitrate, magnesium nitrate, molybdenum nitrate, vanadium nitrate, germanium nitrate, aluminum nitrate, zirconium nitrate, manganese hydroxide, titanium hydroxide, zinc hydroxide, magnesium hydroxide, molybdenum hydroxide, vanadium hydroxide, germanium hydroxide, aluminum hydroxide, zirconium hydroxide; The lithium-containing compound includes one or more of lithium hydroxide, lithium nitrate, lithium carbonate, lithium acetate, lithium chloride, lithium fluoride, lithium iodide; The solvent includes one or more of deionized water, ethanol, methanol, isopropanol, n-butanol, octanol, decanol.

10. The preparation method of the cathode material for lithium ion batteries according to claim 8 or 9, characterized in that, The molar ratio of the lithium-containing compound, soluble metal salt, nickel acetate, cobalt acetate, and doped metal salt by metal element is (1 to 1.2): y: 1 - x - y: x: b, where 0 < x ≤ 0.3, 0 < y ≤ 0.4, and 0 ≤ b ≤ 0.

05.

11. The preparation method of the cathode material for lithium ion batteries according to any one of claims 8-10, characterized in that, The concentration of the pH regulator is 1 mol / L to 3 mol / L, and the pH regulator includes one or more of citric acid, acetic acid, oxalic acid, benzoic acid, acrylic acid, carboxylated graphene, and carboxylated graphite.

12. The preparation method of the cathode material for lithium ion battery according to any one of claims 8-11, characterized in that, In the step of drying to obtain the precursor material, the drying method is one or more of spray drying, flash evaporation, stirring drying, and dynamic drying.

13. The preparation method of the cathode material for lithium-ion batteries according to any one of claims 8-12, characterized in that, In the first sintering, the heating rate is 1 - 8 °C / min, the first cooling temperature is 20 - 30 °C, and the cooling method is quenching. The material after the first sintering is directly transferred to room temperature. In the second sintering, the heating rate is 1 - 8 °C / min, the second cooling temperature is 20 - 30 °C, and the cooling method is quenching. The material after the second sintering is directly transferred to room temperature.

14. A positive electrode sheet, characterized in that, It includes the positive electrode material for a lithium-ion battery according to any one of claims 1 - 7, or the positive electrode material prepared by the preparation method of the positive electrode material for a lithium-ion battery according to any one of claims 8 - 13.

15. The positive electrode sheet according to claim 14, characterized in that, The tap density of the positive electrode sheet is 3 g / cm 3 to 3.7 g / cm 3 .

16. A positive electrode sheet, characterized in that, including a positive electrode material, the chemical formula of the positive electrode material being Li z Ni 1-x-y Co x M y M' b O2, where 0 < x ≤ 0.3, 0 < y ≤ 0.4, 0 ≤ b ≤ 0.05, M is selected from one or more of Mn, Ti, Zn, Mg, Mo, V, Ga, and Al, and M' is selected from one or more of Zr, Ti, Zn, Mg, Mo, V, and Ga; In the X-ray diffraction spectrum of the positive electrode sheet, there are (108) diffraction peaks at a diffraction angle 2θ of (64 ± 0.5)° and (110) diffraction peaks at a diffraction angle 2θ of (65 ± 0.5)°. The (108) diffraction peak and the (110) diffraction peak satisfy: Among them, FWHM(108) is the full width at half maximum of the (108) diffraction peak at a diffraction angle 2θ = (64 ± 0.5)°; FWHM(110) is the full width at half maximum of the (110) diffraction peak at a diffraction angle 2θ = (65 ± 0.5)°.

17. A lithium-ion battery, characterized in that, It includes the positive electrode sheet according to any one of claims 14 - 15 or the positive electrode sheet according to claim 16.

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