A high-nickel ternary positive electrode material, a preparation method and application thereof

Abstract

The application provides a high-nickel ternary positive electrode material and a preparation method and application thereof, and the preparation method of the high-nickel ternary positive electrode material comprises the following steps: S1: mixing a ternary precursor and a lithium source, first sintering, crushing, and obtaining a first sintered material; S2: mixing the first sintered material, a metal M source and a metal N source, second sintering, crushing, and obtaining a second sintered material; S3: mixing the second sintered material and a spinel material, third sintering, crushing, and obtaining a high-nickel ternary positive electrode material; and the spinel material has a chemical general formula of MN2O4. The preparation method of the high-nickel ternary positive electrode material provided by the application has excellent stability, and the prepared high-nickel ternary positive electrode material has a good cycle capacity retention rate in a long cycle process in a high-voltage working environment.

Description

Technical Field

[0001] This invention relates to the field of secondary battery technology, specifically to a high-nickel ternary cathode material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries are commonly used secondary batteries in energy storage systems and transportation electrification, boasting theoretically high energy conversion efficiency and high capacity. A lithium-ion battery typically consists of a positive electrode, a negative electrode, a separator, and an electrolyte. Common negative electrode active materials for lithium-ion batteries include carbon-based and silicon-based materials, while positive electrode active materials include lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, NCM (nickel-cobalt-manganese) ternary cathode materials, NFM (nickel-iron-manganese) ternary cathode materials, and NCA (nickel-cobalt-aluminum) ternary cathode materials.

[0003] The capacity and other performance characteristics of lithium-ion batteries are closely related to the type of active materials. For example, among negative electrode active materials, silicon-based materials have a theoretical capacity far exceeding that of carbon-based materials; among positive electrode active materials, high-nickel ternary cathode materials (with a nickel content ≥80% based on the total molar amount of metal elements in the ternary material) have theoretically higher capacity, higher operating voltage, and relatively lower manufacturing costs. However, in practical applications, in addition to high capacity and high operating voltage, users also have high demands for the lifespan of secondary batteries. When high-nickel ternary cathode materials undergo long-term cycling under high operating voltage conditions, they inevitably face problems such as continuous capacity decay, which limits the lifespan of high-nickel ternary cathode materials.

[0004] Existing technologies include methods for coating the surface of high-nickel ternary cathode materials to improve their performance, such as coating with MgO. However, there is a risk of lattice mismatch between the coating layer and the high-nickel ternary cathode material, which still cannot stably improve the service life of the material. Summary of the Invention

[0005] This invention provides a high-nickel ternary cathode material, its preparation method, and its application, in order to solve the capacity decay problem that occurs in high-nickel ternary materials during long-cycle processes in the prior art.

[0006] In a first aspect, the present invention provides a method for preparing a high-nickel ternary cathode material, comprising the following steps: S1: Mix the ternary precursor and lithium source, sinter for the first time, crush, and obtain a sintered material; S2: Mix the first sintering material, metal M source, and metal N source, sinter for the second time, and crush to obtain the second sintering material; S3: Mix the second sintering material and spinel-type material, sinter for the third time, and crush to obtain high-nickel ternary cathode material; The general chemical formula of the spinel-type material is MN2O4.

[0007] In one optional embodiment, the temperature of the first sintering is 400~550℃, the holding time is 6~10h, the heating rate is 1~5℃ / min, and the first sintering is carried out in an oxygen-containing atmosphere.

[0008] In one optional embodiment, the second sintering temperature is 650~800℃, the holding time is 8~14h, the heating rate is 1.5~5℃ / min, and the second sintering is carried out in an oxygen-containing atmosphere.

[0009] In one optional embodiment, the temperature of the third sintering is 400~600℃, the holding time is 4~6h, the heating rate is 1.5~5℃ / min, and the third sintering is carried out in an oxygen-containing atmosphere.

[0010] In one optional embodiment, the temperature of the first sintering is 430~480℃, the holding time is 7~9h, and the heating rate is 1.5~3℃ / min.

[0011] In one optional embodiment, the temperature of the second sintering is 720~780℃, the holding time is 9~11h, and the heating rate is 1.5~3℃ / min.

[0012] In one optional embodiment, the temperature of the third sintering is 450~550℃, the holding time is 4.5~5.5h, and the heating rate is 1.5~3℃ / min.

[0013] In one optional embodiment, the oxygen-containing atmosphere has an oxygen volume percentage of ≥90%.

[0014] In one optional embodiment, the metal M includes at least one of Mg and Zn; in the spinel-type material and the metal M source, the metal M exists in the state of divalent metal ions; in a further optional embodiment, the metal M is Zn.

[0015] In one optional embodiment, the metal N includes at least one of Al and Cr; in the spinel-type material and the metal N source, the metal N exists in the state of trivalent metal ions; in a further optional embodiment, the metal N is Al.

[0016] In one optional embodiment, in step S1, the molar ratio of the ternary precursor to lithium in the lithium source is 1:1.02~1.08.

[0017] In one optional implementation, in step S2, the sum of the masses of metal M and metal N in the metal M source and the metal N source is 0.1% to 0.6% of the mass of the sintered material.

[0018] In one optional embodiment, in step S3, the sum of the masses of metal M and metal N in the spinel-type material is 0.1% to 0.6% of the mass of the two sintered materials.

[0019] In one optional embodiment, in step S2, the molar ratio of metal M in the metal M source to metal N in the metal N source is 1:1.5~2.5.

[0020] In one optional implementation, in step S2, the sum of the masses of metal M and metal N in the metal M source and the metal N source is 0.1% to 0.3% of the mass of the sintered material.

[0021] In one optional embodiment, in step S3, the sum of the masses of metal M and metal N in the spinel-type material is 0.1% to 0.3% of the mass of the two sintered materials.

[0022] In one optional embodiment, the particle size D50 of the sintered material is 9.0~11.0 μm.

[0023] In one optional embodiment, the particle size D50 of the secondary sintered material is 10.0~12.0 μm.

[0024] In one optional embodiment, the particle size D50 of the high-nickel ternary cathode material is 10.0~12.0 μm.

[0025] In one optional embodiment, the ternary precursor has the chemical formula Ni. x Co y Mn z (OH)2, where x+y+z=1, 0.8≤x<0.95, 0.05≤y<0.2.

[0026] In one alternative embodiment, the lithium source comprises lithium hydroxide.

[0027] In one optional embodiment, the metal M source includes at least one of an oxide of metal M and a hydroxide of metal M; in a further optional embodiment, the metal M source includes at least one of zinc oxide, zinc hydroxide, magnesium oxide, and magnesium hydroxide.

[0028] In one optional embodiment, the metal N source includes at least one of metal N oxide and metal N hydroxide; in a further optional embodiment, the metal N source includes at least one of aluminum oxide, aluminum hydroxide, chromium oxide, and chromium hydroxide.

[0029] In one alternative embodiment, the spinel-type material includes at least one of Al2ZnO4, MgAl2O4, MgCr2O4, and ZnCr2O4.

[0030] Secondly, the present invention also provides a high-nickel ternary cathode material, which is prepared by the above-described preparation method.

[0031] Thirdly, the present invention also provides a positive electrode sheet comprising the above-mentioned high-nickel ternary positive electrode material.

[0032] Fourthly, the present invention also provides a secondary battery, including the above-mentioned positive electrode, and further including a negative electrode, a separator, and an electrolyte.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a method for preparing high-nickel ternary cathode materials. In the preparation process, a ternary precursor and a lithium source are first mixed and sintered for pre-lithiation to obtain a cathode active material with nanoscale primary particles, thereby improving the mechanical stability of the material and suppressing intergranular cracks. Then, the first precursor is mixed with a metal M source and a metal N source, and sintered a second time, allowing the bulk phases of metal M and metal N to be incorporated into the high-nickel ternary cathode material. Finally, the second precursor is mixed with a spinel-type material and sintered a third time, forming a coating layer of spinel-type material on the material surface. The spinel-type material coating layer can alleviate interfacial stress and side reactions, and the metal M and metal N within it can stabilize lattice oxygen and suppress lattice collapse, thereby improving the stability of the material. Furthermore, the metals M and N in the spinel-type coating layer possess both chemical stability and structural compatibility, and can match the lattice of the bulk-doped metals M and N to achieve synergistic modification of the high-nickel ternary cathode material. This effectively suppresses interfacial side reactions, lattice oxygen release, and Li / Ni mixing in the high-nickel ternary cathode material, significantly improving the material's cycle stability and kinetic performance, especially enhancing the material's cycle stability under high-voltage operating conditions. Attached Figure Description

[0034] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0035] Figure 1 This is a cross-sectional SEM image of the high-nickel ternary cathode material obtained in Example 1 of this invention; Figure 2 This is a cross-sectional SEM image of the high-nickel ternary cathode material obtained in Comparative Example 1 of this invention. Detailed Implementation

[0036] The following embodiments are provided to better understand the present invention, but the following embodiments do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the scope of protection of the present invention.

[0037] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0038] In lithium-ion batteries, in order to improve the capacity retention of high-nickel ternary cathode materials during long-term cycling under high operating voltage, existing technologies include coating the surface of high-nickel ternary cathode materials to improve their performance, such as coating with MgO. However, there is a risk of lattice mismatch between the coating layer and the high-nickel ternary cathode material, which still cannot stably improve the service life of the material.

[0039] Therefore, in a first aspect, the present invention provides a method for preparing a high-nickel ternary cathode material, comprising the following steps: S1: Mix the ternary precursor and lithium source, sinter for the first time, crush, and obtain a sintered material; S2: Mix the first sintering material, metal M source, and metal N source, sinter for the second time, and crush to obtain the second sintering material; S3: Mix the second sintering material and spinel-type material, sinter for the third time, and crush to obtain high-nickel ternary cathode material; The general chemical formula of the spinel-type material is MN2O4.

[0040] Typically, without limitation, the pulverization includes at least one of mechanical pulverization and air jet pulverization.

[0041] In one optional embodiment, the first sintering temperature is 400-550℃, the holding time is 6-10h, and the heating rate is 1-5℃ / min. The first sintering is carried out in an oxygen-containing atmosphere. For example, the first sintering temperature can be one or any two of the following: 400℃, 430℃, 450℃, 460℃, 480℃, 500℃, 530℃, and 550℃; the holding time can be one or any two of the following: 6h, 7h, 8h, 9h, and 10h; and the heating rate can be one or any two of the following: 1℃ / min, 1.5℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, and 5℃ / min. Sintering the ternary precursor and lithium source mixture at a lower temperature for pre-lithiation allows for a more reasonable degree of grain refinement, further assisting in improving material performance.

[0042] In one optional embodiment, the second sintering temperature is 650~800℃, the holding time is 8~14h, the heating rate is 1.5~5℃ / min, and the second sintering is carried out in an oxygen-containing atmosphere. For example, the second sintering temperature can be one or any two of the following: 650℃, 680℃, 700℃, 720℃, 750℃, 780℃, 790℃, 800℃; the holding time can be one or any two of the following: 8h, 9h, 10h, 11h, 12h, 14h; and the heating rate can be one or any two of the following: 1.5℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min.

[0043] In one optional embodiment, the third sintering temperature is 400~600℃, the holding time is 4~6h, the heating rate is 1.5~5℃ / min, and the third sintering is carried out in an oxygen-containing atmosphere. For example, the third sintering temperature can be one or any two of the following: 400℃, 430℃, 450℃, 470℃, 490℃, 500℃, 530℃, 550℃, 580℃, 600℃; the holding time can be one or any two of the following: 4h, 4.5h, 5h, 5.5h, 6h; and the heating rate can be one or any two of the following: 1.5℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min.

[0044] In a further optional embodiment, the temperature of the first sintering is 430~480℃, the holding time is 7~9h, and the heating rate is 1.5~3℃ / min.

[0045] In a further optional embodiment, the second sintering temperature is 720~780℃, the holding time is 9~11h, and the heating rate is 1.5~3℃ / min.

[0046] In a further optional embodiment, the temperature of the third sintering is 450~550℃, the holding time is 4.5~5.5h, and the heating rate is 1.5~3℃ / min.

[0047] In one optional embodiment, the oxygen-containing atmosphere has a volume percentage of ≥90%. For example, the volume percentage of oxygen in the oxygen-containing atmosphere can be one or any two of the following: 90%, 93%, 95%, 97%, 99%, 100%. The non-oxygen components can be inert gases such as nitrogen or argon. Using an atmosphere with a higher oxygen content during sintering is beneficial for reducing the residual alkali in the resulting high-nickel ternary cathode material.

[0048] In one optional embodiment, metal M includes at least one of Mg and Zn; in the spinel-type material and the metal M source, metal M exists in the state of divalent metal ions; in a further optional embodiment, metal M is Zn. Metal M existing in the state of divalent metal ions mainly functions to suppress lattice collapse in the material.

[0049] In one optional embodiment, the metallic N includes at least one of Al and Cr; in the spinel-type material and the metallic N source, the metallic N exists in the state of trivalent metal ions; in a further optional embodiment, the metallic N is Al. The metallic N existing in the state of trivalent metal ions primarily acts to stabilize the lattice oxygen in the material.

[0050] In one optional embodiment, in step S1, the molar ratio of the ternary precursor to lithium in the lithium source is 1:1.02~1.08.

[0051] In one optional implementation, in step S2, the sum of the masses of metal M and metal N in the metal M source and the metal N source is 0.1% to 0.6% of the mass of the burnt material. For example, the sum of the masses of metal M and metal N in the metal M source and the metal N source can be a range of 0.1%, 0.2%, 0.3%, 0.5%, 0.6% of the mass of the burnt material, or any two of these ranges.

[0052] In one optional embodiment, in step S3, the sum of the masses of metal M and metal N in the spinel-type material is 0.1% to 0.6% of the mass of the two sintered materials. For example, the sum of the masses of metal M and metal N in the spinel-type material can be a value within the range of one or any two of 0.1%, 0.2%, 0.3%, 0.5%, and 0.6% of the mass of the two sintered materials.

[0053] In an optional embodiment, in step S2, the molar ratio of metal M in the metal M source to metal N in the metal N source is 1:1.5 to 2.5. For example, the molar ratio of metal M in the metal M source to metal N in the metal N source can be one of 1:1.5, 1:1.8, 1:2, 1:2.2, 1:2.5, or any combination thereof. Controlling the molar ratio of metal M in the metal M source to metal N in the metal N source at 1:1.5 to 2.5 can achieve better charge balance and lattice matching with the coated spinel-type material, further reducing the formation of impurity phases and improving the electrical properties of the high-nickel ternary material, especially its cycle stability.

[0054] In a further optional embodiment, in step S2, the sum of the masses of metal M and metal N in the metal M source and the metal N source is 0.1% to 0.3% of the mass of the sintered material.

[0055] In a further optional embodiment, in step S3, the sum of the masses of metal M and metal N in the spinel-type material is 0.1% to 0.3% of the mass of the two sintered materials.

[0056] In one optional embodiment, the particle size D50 of the sintered material is 9.0~11.0 μm.

[0057] In one optional embodiment, the particle size D50 of the secondary sintered material is 10.0~12.0 μm.

[0058] In one optional embodiment, the particle size D50 of the high-nickel ternary cathode material is 10.0~12.0 μm.

[0059] Typically, and not limited to, after the pulverization step, the desired particle size range of primary, secondary, and high-nickel ternary cathode materials can be obtained by sieving.

[0060] In one optional embodiment, the ternary precursor has the chemical formula Ni. x Co y Mn z (OH)2, where x+y+z=1, 0.8≤x<0.95, 0.05≤y<0.2.

[0061] In one alternative embodiment, the lithium source comprises lithium hydroxide. Lithium hydroxide is commonly used as the lithium source in high-nickel ternary cathode materials.

[0062] In one optional embodiment, the metal M source includes at least one of an oxide of metal M and a hydroxide of metal M; in a further optional embodiment, the metal M source includes at least one of zinc oxide, zinc hydroxide, magnesium oxide, and magnesium hydroxide.

[0063] In one optional embodiment, the metal N source includes at least one of metal N oxide and metal N hydroxide; in a further optional embodiment, the metal N source includes at least one of aluminum oxide, aluminum hydroxide, chromium oxide, and chromium hydroxide.

[0064] In one alternative embodiment, the spinel-type material includes at least one of Al2ZnO4, MgAl2O4, MgCr2O4, and ZnCr2O4.

[0065] Secondly, the present invention also provides a high-nickel ternary cathode material, which is prepared by the above-described preparation method.

[0066] Thirdly, the present invention also provides a positive electrode sheet comprising the above-mentioned high-nickel ternary positive electrode material.

[0067] Fourthly, the present invention also provides a secondary battery, including the above-mentioned positive electrode, and further including a negative electrode, a separator, and an electrolyte.

[0068] Example 1 This embodiment provides a high-nickel ternary cathode material and its preparation method, including the following steps: (1) The ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 and lithium hydroxide were mixed in a molar ratio of 1:1.05 and sintered at 500°C at a rate of 2.5°C / min in a pure oxygen atmosphere for the first sintering and holding for 6 hours. After that, the mixture was naturally cooled to room temperature, air-jet pulverized, sieved, and the particle size D50 was controlled to be 10.1 μm (the particle size D50 was measured using a laser particle size analyzer, the same below), to obtain a sintered material.

[0069] (2) Mix the first sintering material, alumina and zinc oxide evenly, wherein the sum of the mass of metallic aluminum and metallic zinc in alumina and zinc oxide is 0.3% of the mass of the first sintering material, and the molar ratio of metallic zinc in zinc oxide to metallic aluminum in alumina is 1:2; in a pure oxygen atmosphere, heat to 700℃ at a rate of 2℃ / min, perform a second sintering and hold for 10h, then cool naturally to room temperature, air-jet pulverize, sieve, and control the particle size D50 to 10.5μm to obtain the second sintering material.

[0070] (3) The two sintering materials and spinel-type material Al2ZnO4 are mixed evenly, wherein the sum of the mass of metallic aluminum and metallic zinc in Al2ZnO4 is 0.2% of the mass of the two sintering materials; in a pure oxygen atmosphere, the temperature is raised to 400℃ at a rate of 2℃ / min, and the third sintering is carried out and held for 5h. Then, it is naturally cooled to room temperature, air-jet pulverized, sieved, and its particle size D50 is controlled to be 10.9μm to obtain high nickel ternary cathode material.

[0071] Example 2 This embodiment provides a high-nickel ternary cathode material and its preparation method. Compared with Example 1, the only difference is that an equimolar amount of the ternary precursor Ni is used. 0.9 Co 0.05 Mn 0.05 (OH)2 replaces the ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2.

[0072] Example 3 This embodiment provides a high-nickel ternary cathode material and its preparation method, including the following steps: (1) The ternary precursor Ni 0.8 Co 0.1 Mn0.1 (OH)2 and lithium hydroxide were mixed in a molar ratio of 1:1.05 and heated to 450°C at a rate of 2°C / min in a pure oxygen atmosphere for the first sintering and holding for 8 hours. After natural cooling to room temperature, the mixture was air-jet pulverized, sieved, and its particle size D50 was controlled to be 10.1 μm to obtain a sintered material.

[0073] (2) Mix the first sintering material, alumina and zinc oxide evenly, wherein the sum of the mass of metallic aluminum and metallic zinc in alumina and zinc oxide is 0.2% of the mass of the first sintering material, and the molar ratio of metallic zinc in zinc oxide to metallic aluminum in alumina is 1:2; in a pure oxygen atmosphere, heat to 750℃ at a rate of 2℃ / min, perform a second sintering and hold for 10h, then cool naturally to room temperature, air-jet pulverize, sieve, and control the particle size D50 to 10.8μm to obtain the second sintering material.

[0074] (3) The two sintering materials and spinel-type material Al2ZnO4 are mixed evenly, wherein the sum of the mass of metallic aluminum and metallic zinc in Al2ZnO4 is 0.2% of the mass of the two sintering materials; in a pure oxygen atmosphere, the temperature is raised to 500℃ at a rate of 2℃ / min, and the third sintering is carried out and held for 5h. Then, it is naturally cooled to room temperature, air-jet pulverized, sieved, and its particle size D50 is controlled to be 11.1μm to obtain high nickel ternary cathode material.

[0075] Example 4 This embodiment provides a high-nickel ternary cathode material and its preparation method, including the following steps: (1) The ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 and lithium hydroxide were mixed in a molar ratio of 1:1.05 and sintered at 430°C at a rate of 1.5°C / min in a pure oxygen atmosphere for the first sintering and holding for 9 hours. After that, the mixture was naturally cooled to room temperature, air-jet pulverized, and sieved to control the particle size D50 to 10.3 μm, thus obtaining a sintered material.

[0076] (2) Mix the first sintering material, alumina and zinc oxide evenly, wherein the sum of the mass of metallic aluminum and metallic zinc in alumina and zinc oxide is 0.1% of the mass of the first sintering material, and the molar ratio of metallic zinc in zinc oxide to metallic aluminum in alumina is 1:2; in a pure oxygen atmosphere, heat to 780℃ at a rate of 3℃ / min, perform a second sintering and hold for 9h, then cool naturally to room temperature, air-jet pulverize, sieve, and control its particle size D50 to 10.5μm to obtain the second sintering material.

[0077] (3) The two sintering materials and spinel-type material Al2ZnO4 are mixed evenly, wherein the sum of the mass of metallic aluminum and metallic zinc in Al2ZnO4 is 0.3% of the mass of the two sintering materials; in a pure oxygen atmosphere, the temperature is raised to 450℃ at a rate of 1.5℃ / min, and the temperature is held for 5.5h for the third sintering. Then, it is naturally cooled to room temperature, air-jet pulverized, sieved, and its particle size D50 is controlled to be 10.8μm to obtain high nickel ternary cathode material.

[0078] Example 5 This embodiment provides a high-nickel ternary cathode material and its preparation method, including the following steps: (1) The ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 and lithium hydroxide were mixed in a molar ratio of 1:1.05 and heated to 480°C at a rate of 3°C / min in a pure oxygen atmosphere for the first sintering and holding for 7 hours. After natural cooling to room temperature, the mixture was air-jet pulverized, sieved, and its particle size D50 was controlled to be 10.2 μm to obtain a sintered material.

[0079] (2) Mix the first sintering material, alumina and zinc oxide evenly, wherein the sum of the mass of metallic aluminum and metallic zinc in alumina and zinc oxide is 0.3% of the mass of the first sintering material, and the molar ratio of metallic zinc in zinc oxide to metallic aluminum in alumina is 1:2; in a pure oxygen atmosphere, heat to 720℃ at a rate of 1.5℃ / min, perform a second sintering and hold for 11h, then cool naturally to room temperature, air-jet pulverize, sieve, and control the particle size D50 to 11.1μm to obtain the second sintering material.

[0080] (3) The two sintering materials and spinel-type material Al2ZnO4 are mixed evenly, wherein the sum of the mass of metallic aluminum and metallic zinc in Al2ZnO4 is 0.1% of the mass of the two sintering materials; in a pure oxygen atmosphere, the temperature is raised to 550℃ at a rate of 3℃ / min, and the third sintering is carried out and held for 4.5h. Then, it is naturally cooled to room temperature, air-jet pulverized, sieved, and its particle size D50 is controlled to be 11.3μm to obtain high nickel ternary cathode material.

[0081] Example 6 This embodiment provides a high-nickel ternary cathode material and its preparation method, including the following steps: (1) The ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 and lithium hydroxide were mixed in a molar ratio of 1:1.02 and heated to 550°C at a rate of 5°C / min in a mixed oxygen atmosphere with a volume ratio of oxygen to nitrogen of 9.5:0.5. The mixture was then held at this temperature for 6 hours and allowed to cool naturally to room temperature. The mixture was then air-jet pulverized, sieved, and its particle size D50 was controlled to be 9.3 μm to obtain a sintered material.

[0082] (2) Mix the first sintering material, alumina and zinc oxide evenly, wherein the sum of the mass of metallic aluminum and metallic zinc in alumina and zinc oxide is 0.6% of the mass of the first sintering material, and the molar ratio of metallic zinc in zinc oxide to metallic aluminum in alumina is 1:1.5; in a mixed oxygen atmosphere with a volume ratio of oxygen to nitrogen of 9.5:0.5, the temperature is raised to 650℃ at a rate of 1.5℃ / min, and the second sintering is carried out and held for 14h. Then, it is naturally cooled to room temperature, air-jet pulverized, sieved, and its particle size D50 is controlled to be 10.1μm to obtain the second sintering material.

[0083] (3) The two sintering materials and spinel-type material Al2ZnO4 are mixed evenly, wherein the sum of the mass of metallic aluminum and metallic zinc in Al2ZnO4 is 0.1% of the mass of the two sintering materials; in a mixed oxygen atmosphere with a volume ratio of oxygen to nitrogen of 9.5:0.5, the temperature is raised to 600℃ at a rate of 5℃ / min, and the temperature is held for 4 hours for the third sintering. Then, it is naturally cooled to room temperature, air-jet pulverized, sieved, and its particle size D50 is controlled to be 10.3μm to obtain high nickel ternary cathode material.

[0084] Example 7 This embodiment provides a high-nickel ternary cathode material and its preparation method, including the following steps: (1) The ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 and lithium hydroxide were mixed in a molar ratio of 1:1.08 and heated to 400°C at a rate of 1°C / min in a mixed oxygen atmosphere with a volume ratio of oxygen to nitrogen of 9:1. The mixture was then held at this temperature for 10 hours and allowed to cool naturally to room temperature. The mixture was then air-jet pulverized, sieved, and its particle size D50 was controlled to be 10.9 μm to obtain a sintered material.

[0085] (2) Mix the first sintering material, alumina and zinc oxide evenly, wherein the sum of the mass of metallic aluminum and metallic zinc in alumina and zinc oxide is 0.1% of the mass of the first sintering material, and the molar ratio of metallic zinc in zinc oxide to metallic aluminum in alumina is 1:2.5; in a mixed oxygen atmosphere with a volume ratio of oxygen to nitrogen of 9:1, the temperature is raised to 800℃ at a rate of 5℃ / min, and the second sintering is carried out and held for 8h. Then, it is naturally cooled to room temperature, air-jet pulverized, sieved, and its particle size D50 is controlled to be 11.8μm to obtain the second sintering material.

[0086] (3) The two sintering materials and spinel-type material Al2ZnO4 are mixed evenly, wherein the sum of the mass of metallic aluminum and metallic zinc in Al2ZnO4 is 0.6% of the mass of the two sintering materials; in a mixed oxygen atmosphere with a volume ratio of oxygen to nitrogen of 9:1, the temperature is raised to 400℃ at a rate of 1.5℃ / min, and the temperature is held for 6 hours for the third sintering. Then, it is naturally cooled to room temperature, air-jet pulverized, sieved, and its particle size D50 is controlled to be 11.9μm to obtain high-nickel ternary cathode material.

[0087] Comparative Example 1 This comparative example provides a high-nickel ternary cathode material and its preparation method, including the following steps: (1) Use ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2, lithium hydroxide, aluminum oxide, and zinc oxide are mixed evenly, wherein the ternary precursor Ni 0.8 Co 0.1 Mn 0.1 The molar ratio of (OH)₂ to lithium hydroxide is 1:1.05. The sum of the masses of metallic aluminum and metallic zinc in alumina and zinc oxide is equal to the mass of the ternary precursor Ni. 0.8 Co 0.1 Mn 0.1 0.3% of the mass of (OH)2; in a pure oxygen atmosphere, the temperature is raised to 700℃ at a rate of 2℃ / min for the first sintering for 10h, then naturally cooled to room temperature, air-jet pulverized, sieved, and the particle size D50 is controlled to be 10.1μm to obtain the first sintered material.

[0088] (2) The first sintering material and spinel-type material Al2ZnO4 are mixed evenly, wherein the sum of the mass of metallic aluminum and metallic zinc in Al2ZnO4 is 0.2% of the mass of the first sintering material; in a pure oxygen atmosphere, the temperature is raised to 400℃ at a rate of 2℃ / min, and a second sintering is carried out for 5h. After that, it is naturally cooled to room temperature, air-jet pulverized, sieved, and its particle size D50 is controlled to be 10.9μm to obtain high nickel ternary cathode material.

[0089] Comparative Example 2 This comparative example provides a high-nickel ternary cathode material and its preparation method. Compared with Example 7, the only difference is that in step (2), aluminum oxide and zinc oxide are not added, and only one sintering material is carried out for a second time.

[0090] Comparative Example 3 This comparative example provides a high-nickel ternary cathode material and its preparation method. Compared with Example 7, the only difference is that in step (3), spinel-type material is not added, and the second sintering material is sintered for the third time.

[0091] Comparative Example 4 This comparative example provides a high-nickel ternary cathode material and its preparation method. Compared with Example 7, the only difference is that in step (2), magnesium oxide of equal mass is used instead of zinc oxide.

[0092] Comparative Example 5 This comparative example provides a high-nickel ternary cathode material and its preparation method. The only difference from Example 7 is that, in step (3), an equal mass of MgAl2O4 is used to replace Al2ZnO4.

[0093] Experimental Example 1 The high-nickel ternary cathode materials prepared in Example 1 and Comparative Example 1 were used. These high-nickel ternary cathode materials are polycrystalline particles, i.e., secondary spherical particles formed by the agglomeration of primary particles. Single secondary spherical particles from each of Example 1 and Comparative Example 1 were used to prepare standard cross-sectional samples of the secondary spherical particles using argon ion polishing (CP). The cross-sectional SEM images of the secondary spherical particles were observed under a scanning electron microscope (SEM). The cross-sectional SEM image of the high-nickel ternary cathode material obtained in Example 1 is shown below. Figure 1 The cross-sectional SEM image of the high-nickel ternary cathode material obtained in Comparative Example 1 is shown below. Figure 2 .

[0094] from Figure 1 As can be seen from the above, in Example 1, the high-nickel ternary cathode material prepared using the preparation method provided in this application has relatively fine primary particles, sufficient fusion between particles, and fewer intergranular cracks. In Comparative Example 1, the preparation method provided in this application was not used; instead of first mixing and sintering the ternary precursor and lithium source, the ternary precursor, lithium source, and two other metal sources were directly mixed and sintered in one step. Figure 2 As can be seen, the high-nickel ternary cathode material obtained by this preparation method has relatively large primary particles, poor fusion between particles, and many intergranular cracks. In contrast, the preparation method provided in this application first mixes the ternary precursor and lithium source and performs a first sintering pre-lithiation, resulting in more uniform lithiation of the obtained high-nickel ternary cathode material, lower local stress, and effectively suppressing microcracks caused by anisotropic volume changes during subsequent high-temperature sintering.

[0095] Experiment Example 2 The high-nickel ternary cathode material, polyvinylidene fluoride (PVDF) binder, and conductive carbon black (SP) conductive agent prepared in the examples and comparative examples were mixed in a mass ratio of 97.2:1.3:1.5. Ethylene carbonate solvent was added to prepare a cathode slurry with a solid content of 49%. The cathode slurry was coated onto the current collector aluminum foil using a coating machine, with a coating surface density of 16 mg / cm³. 2After coating, the electrode is dried in a forced-air drying oven at 80°C for 2 hours to obtain the positive electrode sheet. The negative electrode sheet uses a lithium metal sheet, the separator uses a PE (polyethylene) separator, and the electrolyte uses a 1 mol / L LiPF6 electrolyte with a solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a mass ratio of 25:10:65. The positive electrode sheet, separator, negative electrode sheet, and electrolyte are combined and assembled into a CR2032 coin cell.

[0096] The obtained CR2032 button cell was connected to the Blue Electric test system. The charging cutoff voltage was 4.25V, the discharging cutoff voltage was 2.5V, and the charging rate and discharging rate were both 1C. The capacity retention rate after 100 cycles was tested, and the results are shown in Table 1.

[0097] After connecting the obtained CR2032 button cell to the Blue Electric testing system, the charging cutoff voltage was 4.25V, the discharging cutoff voltage was 2.5V, and the charging rate and discharging rate were both 0.2C. The first charge specific capacity (0.2CC) and the first discharge specific capacity (0.2CD) were tested, and the results are shown in Table 1.

[0098] Table 1

[0099] As can be seen from Table 1, the high-nickel ternary cathode materials prepared in the embodiments of this application all have high capacity retention rates after 100 cycles of 1C / 1C. The preparation method provided in this application improves the capacity retention rate of the high-nickel ternary cathode materials during long-cycle processes in high-voltage operating environments by combining three sintering processes and bulk doping of metal M and metal N with coating of spinel-type material MN2O4.

[0100] Specifically, compared to Example 1, Comparative Example 1 omits the step of mixing and sintering the ternary precursor and lithium source, resulting in coarser primary grains and ultimately a lower cycle capacity retention. Compared to Example 7, Comparative Example 2 does not dope Al or Zn in the bulk phase, but only coats the outer layer with a spinel-type material Al2ZnO4; Comparative Example 3 only coats the outer layer with a spinel-type material Al2ZnO4, without doping Al or Zn in the bulk phase. Both examples lack either bulk doping of metals M and N, or coating with spinel-type material MN2O4, failing to achieve a synergistic match between bulk doping and outer coating, resulting in a significantly lower cycle capacity retention compared to Example 7. Compared to Example 7, in Comparative Examples 4 and 5, the metals M and N in the bulk phase are inconsistent with the metal elements in the outer spinel-type coating, also failing to achieve a synergistic match between bulk doping and outer coating, ultimately leading to a lower cycle capacity retention.

[0101] In the embodiments, Examples 3-5 used the preferred range values ​​of each preparation parameter, showing the best cycle capacity retention rate, reaching 95.5%-95.8%. In Example 1, compared to Examples 3-5, some preparation parameters were outside the preferred range, resulting in a slight decrease in cycle capacity retention rate to 95.4%. In Example 2, compared to Example 1, a ternary precursor with a higher nickel content was used, and the resulting battery still maintained a high cycle capacity retention rate of 92.1%, fully demonstrating that the preparation method provided in this application is suitable for preparing ternary cathode materials with higher nickel content. Examples 6 and 7 used the larger range values ​​of each preparation parameter, showing a slight decrease in cycle capacity retention rate compared to Examples 3-5, remaining at around 91%, but still showing a significant advantage compared to the comparative examples.

[0102] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a high-nickel ternary cathode material, characterized in that, Includes the following steps: S1: Mix the ternary precursor and lithium source, sinter for the first time, crush, and obtain a sintered material; S2: Mix the first sintering material, metal M source, and metal N source, sinter for the second time, and crush to obtain the second sintering material; S3: Mix the second sintering material and spinel-type material, sinter for the third time, and crush to obtain high-nickel ternary cathode material; The general chemical formula of the spinel-type material is MN2O4.

2. The preparation method according to claim 1, characterized in that, The temperature of the first sintering is 400~550℃, the holding time is 6~10h, the heating rate is 1~5℃ / min, and the first sintering is carried out in an oxygen-containing atmosphere. And / or, the temperature of the second sintering is 650~800℃, the holding time is 8~14h, the heating rate is 1.5~5℃ / min, and the second sintering is carried out in an oxygen-containing atmosphere; And / or, the temperature of the third sintering is 400~600℃, the holding time is 4~6h, the heating rate is 1.5~5℃ / min, and the third sintering is carried out in an oxygen-containing atmosphere.

3. The preparation method according to claim 2, characterized in that, The temperature of the first sintering is 430~480℃, the holding time is 7~9h, and the heating rate is 1.5~3℃ / min; And / or, the temperature of the second sintering is 720~780℃, the holding time is 9~11h, and the heating rate is 1.5~3℃ / min; And / or, the temperature of the third sintering is 450~550℃, the holding time is 4.5~5.5h, and the heating rate is 1.5~3℃ / min; And / or, in the oxygen-containing atmosphere, the volume percentage of oxygen is ≥90%.

4. The preparation method according to any one of claims 1 to 3, characterized in that, Metal M includes at least one of Mg and Zn; in the spinel-type material and the metal M source, metal M exists in the state of divalent metal ions; optionally, metal M is Zn; And / or, the metal N includes at least one of Al and Cr; in the spinel-type material and the metal N source, the metal N exists in the state of trivalent metal ions; optionally, the metal N is Al; And / or, in S1, the molar ratio of the ternary precursor to lithium in the lithium source is 1:1.02~1.08; And / or, in S2, the sum of the masses of metal M and metal N in the metal M source and the metal N source is 0.1% to 0.6% of the mass of the sintered material; And / or, in S3, the sum of the masses of metal M and metal N in the spinel-type material is 0.1% to 0.6% of the mass of the two sintered materials.

5. The preparation method according to claim 4, characterized in that, In step S2, the molar ratio of metal M in the metal M source to metal N in the metal N source is 1:1.5~2.5; And / or, in S2, the sum of the masses of metal M and metal N in the metal M source and the metal N source is 0.1% to 0.3% of the mass of the sintered material; And / or, in S3, the sum of the masses of metal M and metal N in the spinel-type material is 0.1% to 0.3% of the mass of the two sintered materials.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The particle size D50 of the sintered material is 9.0~11.0μm; And / or, the particle size D50 of the second sintered material is 10.0~12.0μm; And / or, the particle size D50 of the high-nickel ternary cathode material is 10.0~12.0 μm.

7. The preparation method according to any one of claims 1 to 6, characterized in that, The chemical formula of the ternary precursor is Ni x Co y Mn z (OH)2, where x+y+z=1, 0.8≤x<0.95, 0.05≤y<0.2; And / or, the lithium source includes lithium hydroxide; And / or, the metal M source includes at least one of an oxide of metal M and a hydroxide of metal M; optionally, the metal M source includes at least one of zinc oxide, zinc hydroxide, magnesium oxide, and magnesium hydroxide. And / or, the metal N source includes at least one of an oxide of metal N and a hydroxide of metal N; optionally, the metal N source includes at least one of aluminum oxide, aluminum hydroxide, chromium oxide, and chromium hydroxide. And / or, the spinel-type material includes at least one of Al2ZnO4, MgAl2O4, MgCr2O4, and ZnCr2O4.

8. A high-nickel ternary cathode material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

9. A positive electrode sheet, characterized in that, Including the high-nickel ternary cathode material as described in claim 8.

10. A secondary battery, characterized in that, It includes the positive electrode as described in claim 9, and also includes a negative electrode, a separator, and an electrolyte.

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