Multi-stage cobalt-containing cathode material, method for preparing the same, and lithium-ion battery

Abstract

The present application provides a multi-stage cobalt-containing positive electrode material and a method for preparing the same, and a lithium-ion battery. The preparation method includes the following steps: (1) mixing and reacting an active material raw material, a lithium source, and a chelating agent to obtain a sol precursor; (2) mixing a cobalt-containing material A, a cobalt-containing material B, and the sol precursor and heating the mixture until the sol precursor forms a powdered active material to obtain a mixture of the cobalt-containing material A, the cobalt-containing material B, and the powdered active material; and (3) mixing and sintering the mixture and the coated sol precursor to obtain the multi-stage cobalt-containing positive electrode material. The method according to the present application solves the problem of uneven particle size grading distribution between large and small particles, improves tap density and capacity, and further improves coating uniformity.

Description

Technical Field

[0001] This application belongs to the technical field of batteries, and relates to a cobalt-containing cathode material with a multi-stage structure, a preparation method thereof, and a lithium-ion battery.

Background Art

[0002] In recent years, with the rapid development of various portable electronic devices and electric vehicles, people's needs for the performance of lithium-ion batteries have been increasing. Therefore, in order to meet the market needs of different sub-fields, it has become increasingly important to develop lithium-ion batteries with characteristics such as high capacity, high rate, and cycle stability for different application scenarios. Currently, in the lithium-ion battery cathode materials used in 3C products, lithium cobaltate still occupies a large share due to its excellent theoretical capacity and tap density. However, in order to meet the repeated needs of consumer-side products, higher challenges are faced in terms of the energy density and cycle life of lithium cobaltate cathode materials. To improve the energy density of lithium cobaltate, there are two most direct methods: improving its tap density and improving its operating voltage.

[0003] Generally, good tap density can be obtained by using lithium cobaltate particles with large crystal particle sizes. However, if the crystal particle size is too large, it may affect the effect of the electrical performance of the material. Therefore, in actual applications, the particle size grading method of two types of particles, large particles and small particles, can be used to obtain good electrical performance effects and energy density. The finished product obtained in this way is prone to aggregation and condensation of small particles, which affects the uniformity of the material and may further damage its electrical performance effect. At the same time, due to the irregularity of large and small particles, the gaps between particles become large and uneven, which is disadvantageous for further improvement of its tap density.

[0004] Increasing the operating voltage of lithium cobalt oxide can release more lithium and improve the capacitance effect of lithium cobalt oxide. However, higher operating voltages can lead to more side reactions and irreversible phase transitions, accelerating the decay of the electrical performance of lithium cobalt oxide. Typically, solid-phase doping and solid-phase coating can suppress the loss of lithium cobalt oxide. For lithium cobalt oxide using particle size grading of large and small particles, solid-phase coating is difficult to achieve due to limitations imposed by kinetic factors. Under high voltage, defects due to uneven coating can accelerate the occurrence of side reactions, reducing the effectiveness of its cycle performance.

[0005] Therefore, improving the tap density of lithium cobalt oxide cathode materials, as well as enhancing the dispersibility of grading particles and the uniformity of the coating, is an urgent technical issue that requires further research. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The following is an overview of the subject matter described in detail in this specification. This overview is not intended to limit the scope of the claims.

[0007] To address the shortcomings of the prior art, this application aims to provide a multi-stage cobalt-containing cathode material, a method for preparing the same, and a lithium-ion battery. By performing particle size grading using the sol method, the organic framework related to the sol precursor can inhibit grain boundary transitions during the sintering process, effectively suppressing the aggregation of small particles and thus solving the problem of uneven dispersion of particle size grading between large and small particles. The powdery active material formed after heating the sol precursor can be uniformly distributed on the surfaces and in the gaps between cobalt-containing material A and cobalt-containing material B, and particles with a uniform grading distribution can improve tap density and press density, thereby improving capacity. At the same time, by performing coating using the sol method, and mixing and sintering the coating sol precursor and mixed material, the uniformity of the coating can be improved. [Means for solving the problem]

[0008] To achieve this objective, this application adopts the following technical solution.

[0009] In its first aspect, the present application is: Step (1) involves mixing the active material raw material, lithium source, and chelating agent, reacting them, and then obtaining a sol precursor. Step (2) involves mixing cobalt-containing material A, cobalt-containing material B, and the sol precursor described in step (1), and heating until the sol precursor forms a powdery active material to obtain a mixed material of cobalt-containing material A, cobalt-containing material B, and powdery active material. The present invention provides a method for preparing a multi-stage cobalt-containing cathode material, comprising step (3) mixing the mixed material and coating sol precursor described in step (2), sintering them, and obtaining a multi-stage cobalt-containing cathode material.

[0010] This invention provides a method for preparing a multi-stage cobalt-containing cathode material. By performing particle size grading using the sol method, the organic framework related to the sol precursor can inhibit grain boundary transitions during the sintering process, effectively suppressing the aggregation of small particles. This solves the problem of uneven dispersion of particle size grading between large and small particles. The powdery active material formed after heating the sol precursor can be uniformly distributed on the surfaces and in the gaps between cobalt-containing material A and cobalt-containing material B. Particles with uniform grading distribution can improve tap density and press density, thereby improving capacity. Simultaneously, by performing coating using the sol method, mixing the coating sol precursor and mixed material, and sintering, the uniformity of the coating can be improved.

[0011] As a preferred technical solution of the present invention, the active material raw material described in step (1) comprises at least one of cobalt salts, nickel salts, manganese salts, iron salts, and phosphorus sources, and is preferably a cobalt salt.

[0012] In this application, the active material raw material described in step (1) may be a cobalt salt alone, and may be one of the raw materials for lithium cobalt oxide active material. At the same time, the active material raw material typically includes, but is not limited to, combinations of cobalt salt, nickel salt and manganese salt, combination of cobalt salt and nickel salt, combination of cobalt salt and manganese salt, combination of nickel salt and manganese salt, or combination of iron salt and phosphorus source. Of these, the combination of cobalt salt, nickel salt and manganese salt may be a mixture of cobalt salt, nickel salt and manganese salt, or a ternary composite salt of cobalt, nickel and manganese. The combination of cobalt salt and nickel salt may be a mixture of cobalt salt and nickel salt, or a binary composite salt of cobalt and nickel, and so on.

[0013] In one embodiment, the cobalt salt comprises at least one of cobalt oxalate, cobalt citrate dihydrate, cobalt nitrate, cobalt sulfate, and cobalt chloride.

[0014] In one embodiment, the nickel salt comprises at least one of nickel nitrate, nickel sulfate, and nickel chloride.

[0015] In one embodiment, the manganese salt comprises at least one of manganese nitrate, manganese sulfate, and manganese chloride.

[0016] In one embodiment, the iron salt comprises at least one of iron nitrate, iron sulfate, and iron chloride.

[0017] In one embodiment, the phosphorus source includes at least one of phosphoric acid, iron phosphate, and ammonium iron phosphate.

[0018] In one embodiment, the lithium source described in step (1) includes at least one of lithium nitrate, lithium oxalate, lithium citrate, and lithium chloride.

[0019] In one embodiment, the chelating agent described in step (1) alcohol Including the above alcohol It contains ethanol and / or ethylene glycol.

[0020] In one embodiment, the raw materials of the mixture described in step (1) further comprise a dopant and / or a dispersant.

[0021] In one embodiment, the doping element in the dopant includes at least one of the elements Al, Mg, Ti, Ce, Nb, Sb, Cr, F, La, W, V, Zr, Ni, and Mn.

[0022] In one embodiment, if the doping element in the dopant is present as a cation, the corresponding anion includes oxalate ions, phosphate ions, acetate ions, nitrate ions, sulfate ions, or chloride ions.

[0023] In one embodiment, the doping element content in the sol precursor described in step (1) is 300 to 30000 ppm, and may be, for example, 300 ppm, 400 ppm, 500 ppm, 1000 ppm, 1500 ppm, 3000 ppm, 5000 ppm, 10000 ppm, 20000 ppm, or 30000 ppm, but is not limited to the values ​​listed, and other values ​​within that range that are not listed are also applicable.

[0024] In one embodiment, the dispersant includes an anionic dispersant and / or a cationic dispersant, such as polyvinylpyrrolidone (PVP) and / or polyoxyethylene polyoxypropylene ether (P123) of each degree of polymerization.

[0025] In one embodiment, the reaction temperature described in step (1) is 100 to 150°C, and may be, for example, 100°C, 110°C, 120°C, 130°C, 140°C, or 150°C, but is not limited to the values ​​listed above, and other values ​​within that range that are not listed are also applicable.

[0026] In one embodiment, the reaction time described in step (1) is 1 to 3 h. For example, it may be 1 h, 1.5 h, 2 h, 2.5 h, or 3 h, etc., but it is not limited to the listed numerical values, and other unlisted numerical values within the range of the numerical values are equally applicable.

[0027] As a preferred technical solution of the present application, the cobalt-containing material A described in step (2) is a single crystal material.

[0028] In one embodiment, the cobalt-containing material A described in step (2) contains lithium cobaltate and / or lithium nickel cobalt manganese oxide.

[0029] In one embodiment, the particle size D50 of the cobalt-containing material A described in step (2) is 15 to 21 μm. For example, it may be 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, or 21 μm, etc., but it is not limited to the listed numerical values, and other unlisted numerical values within the range of the numerical values are equally applicable.

[0030] In one embodiment, the cobalt-containing material A described in step (2) contains doping elements, and the doping elements include at least one of the elements Al, Mg, Ce, Nb, Sb, Cr, F, La, W, V, Zr, Ni, and Mn.

[0031] In one embodiment, the content of the doping elements in the cobalt-containing material A described in step (2) is 300 to 30,ooo ppm. For example, it may be 300 ppm, a 400 ppm, 500 ppm, 10o0 ppm, 1500 ppm, 3000 ppm, 5000 ppm, 10000 ppm, 20000 ppm, or 30000 ppm, etc., but it is not limited to the listed numerical values, and other unlisted numerical values within the range of the numerical values are equally applicable.

[0032] In one embodiment, the method for preparing the cobalt-containing material A includes mixing tricobalt tetroxide and lithium carbonate, sintering them stepwise, then grinding and sieving the mixture to obtain the cobalt-containing material A. The temperature range for the stepwise sintering is 900 to 1200°C, and may be, for example, 900°C, 950°C, 1000°C, 1100°C, or 1200°C. Preferably, the tricobalt tetroxide contains a doping element.

[0033] As a preferred technical solution of this application, the cobalt-containing material B described in step (2) is a single-crystal material.

[0034] In one embodiment, the cobalt-containing material B described in step (2) comprises lithium cobalt oxide and / or lithium nickelcobalt manganese oxide.

[0035] In one embodiment, the particle size D50 of the cobalt-containing material B described in step (2) is smaller than the particle size D50 of the cobalt-containing material A.

[0036] In one embodiment, the particle size D50 of the cobalt-containing material B described in step (2) is 3 to 9 μm, and may be, for example, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, or 9 μm, but is not limited to the values ​​listed, and other values ​​within that range that are not listed are also applicable.

[0037] In one embodiment, the cobalt-containing material B described in step (2) contains a doping element, the doping element comprising at least one of the elements Al, Mg, Ce, Nb, Sb, Cr, F, La, W, V, Zr, Ni, and Mn.

[0038] In one embodiment, the doping element content in the cobalt-containing material B described in step (2) is 300 to 30,000 ppm, and may be, for example, 300 ppm, 400 ppm, 500 ppm, 1,000 ppm, 1,500 ppm, 3,000 ppm, 5,000 ppm, 10,000 ppm, 20,000 ppm, or 30,000 ppm, but is not limited to the values ​​listed, and other values ​​within that range that are not listed are also applicable.

[0039] In this application, the doping element exhibits a gradient distribution in the multi-layered cobalt-containing cathode material.

[0040] In one embodiment, the method for preparing the cobalt-containing material B includes mixing tricobalt tetroxide and lithium carbonate, sintering them stepwise, then grinding and sieving the mixture to obtain the cobalt-containing material B. The temperature range for the stepwise sintering is 800 to 1000°C, and may be, for example, 800°C, 850°C, 900°C, or 1000°C. Preferably, the tricobalt tetroxide contains a doping element.

[0041] In one embodiment, the mass ratio of solid content in cobalt-containing material A, cobalt-containing material B, and sol precursor described in step (2) is 8:(0.9~1.7):(0.3~1.1). Of these, the selectable range for cobalt-containing material B (0.9~1.7) may be, for example, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, or 1.7, and the selectable range for solid content in the sol precursor (0.3~1.1) may be, for example, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or 1.1, but is not limited to the values ​​listed, and other values ​​within the range not listed may also be applied.

[0042] In this invention, if the solid content in the sol precursor is too low, the volume and press density decrease, and if the solid content in the sol precursor is too high, the cycle performance and press density decrease.

[0043] A preferred technical method of this application is that the mixing process described in step (2) is accompanied by stirring. The stirring speed is 1000 to 2000 r / min, and may be, for example, 1000 r / min, 1100 r / min, 1200 r / min, 1400 r / min, 1500 r / min, 1600 r / min, 1800 r / min or 2000 r / min, and the stirring time is 5 to 15 min, and may be, for example, 5 min, 7 min, 9 min, 10 min, 12 min or 15 min, but is not limited to the values ​​listed, and other values ​​within that range that are not listed are also applicable.

[0044] In one embodiment, the heating temperature described in step (2) is 100 to 150°C, and may be, for example, 100°C, 110°C, 120°C, 130°C, 140°C, or 150°C, but is not limited to the values ​​listed, and other values ​​within that range that are not listed may also be applied.

[0045] In one embodiment, the heating time described in step (2) is 1 to 3 hours, and may be, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours, but is not limited to the given values, and other values ​​within that range that are not listed may also apply.

[0046] In one embodiment, the powdered active material described in step (2) comprises one of lithium cobaltate, lithium iron phosphate, or lithium nickel cobalt manganese, and is preferably lithium cobaltate.

[0047] In one embodiment, the particle size D50 of the powdered active material described in step (2) is smaller than the particle size D50 of the cobalt-containing material B.

[0048] In one embodiment, the particle size D50 of the powdered active material described in step (2) is 0.01 to 1.99 μm, and may be, for example, 0.01 μm, 0.02 μm, 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, or 1.9 μm, but is not limited to the values ​​listed, and other values ​​within that range that are not listed are also applicable.

[0049] In this invention, if the particle size D50 of the powdered active material is small, the cycle performance and press density will decrease, and if the particle size D50 of the powdered active material is too large, the cycle performance and press density will also decrease.

[0050] As a preferred technical example of the present invention, the method for preparing a coated sol precursor described in step (3) includes mixing a coating element-containing compound and a chelating agent, reacting them, and then obtaining the coated sol precursor.

[0051] In one embodiment, the coating element includes at least one of the elements Ti, Zr, Y, Ce, Nb, Sb, Cr, F, La, W, and V.

[0052] In one embodiment, the coating element-containing compound may be a coating element-containing salt or a coating element-containing oxide.

[0053] In one embodiment, when the coating element in the coating element-containing salt is present as a cation, the corresponding anion includes oxalate ions, phosphate ions, acetate ions, nitrate ions, sulfate ions, or chloride ions.

[0054] In one embodiment, in a method for preparing a coated sol precursor, the chelating agent is alcohol Including the above alcohol It contains ethanol and / or ethylene glycol.

[0055] In one embodiment, in a method for preparing a coated sol precursor, the reaction temperature is 100 to 150°C, for example, 100°C, 110°C, 120°C, 130°C, 140°C, or 150°C, and the reaction time is 1 to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours, but is not limited to the values ​​listed, and other values ​​within that range that are not listed are also applicable.

[0056] In one embodiment, the mass ratio of the mixed material to the coating sol precursor described in step (3) is (7-27):3, and may be, for example, 7:3, 9:3, 10:3, 12:3, 15:3, 17:3, 20:3, 25:3, or 27:3, but is not limited to the values ​​listed above, and other values ​​within that range that are not listed are also applicable.

[0057] A preferred technical method of this application is that the mixing process described in step (3) is accompanied by stirring. The stirring speed is 600 to 1000 r / min, and may be, for example, 600 r / min, 700 r / min, 800 r / min, 800 r / min or 1000 r / min, and the stirring time is 20 to 40 min, and may be, for example, 20 min, 25 min, 30 min, 35 min or 40 min, but is not limited to the values ​​listed, and other values ​​within that range that are not listed are also applicable.

[0058] In one embodiment, the sintering temperature described in step (3) is 600 to 800°C, and may be, for example, 600°C, 620°C, 650°C, 670°C, 700°C, 720°C, 750°C, 770°C, or 800°C, but is not limited to the values ​​listed, and other values ​​within that range that are not listed are also applicable.

[0059] In one embodiment, the sintering time described in step (3) is 8 to 12 hours, and may be, for example, 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours, but is not limited to the given values, and other values ​​within that range that are not listed may also apply.

[0060] Preferably, the sintering atmosphere described in step (3) is an air atmosphere or a mixed atmosphere of air and an inert gas.

[0061] In a second aspect, the present application provides a multi-stage cobalt-containing cathode material prepared by the preparation method described in the first aspect.

[0062] As a preferred technical solution of the present invention, the multi-stage cobalt-containing cathode material comprises a cobalt-containing material A1, a cobalt-containing material B1, and an active material.

[0063] The cobalt-containing material A1, cobalt-containing material B1, and active material each independently include a substrate and an oxide coating layer applied to the surface of the substrate. The active material is uniformly distributed on the surfaces and in the gaps of cobalt-containing material A1 and cobalt-containing material B1.

[0064] In this application, the statement that the cobalt-containing material A1, cobalt-containing material B1, and active material independently comprise a substrate and an oxide coating layer coated on the surface of the substrate means, specifically, that the cobalt-containing material A1 comprises a cobalt-containing material A substrate and an oxide coating layer coated on the surface of the substrate, the cobalt-containing material B1 comprises a cobalt-containing material B substrate and an oxide coating layer coated on the surface of the substrate, and the active material comprises a powdery active material substrate and an oxide coating layer coated on the surface of the substrate. The types and ratios of materials in the oxide coating layers of the cobalt-containing material A1, cobalt-containing material B1, and active material are the same. The coating elements in the oxide coating layer include at least one of the elements Ti, Zr, Y, Ce, Nb, Sb, Cr, F, La, W, and V.

[0065] In one embodiment, the particle size of the cobalt-containing material A1 is 15 to 21 μm, and may be, for example, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, or 21 μm, but is not limited to the values ​​listed, and other values ​​within that range that are not listed are also applicable.

[0066] In one embodiment, the particle size of the cobalt-containing material B1 is 3 to 9 μm, and may be, for example, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, or 9 μm, but is not limited to the values ​​listed, and other values ​​within that range that are not listed are also applicable.

[0067] In one embodiment, the particle size of the active material is 0.01 to 1.99 μm, and may be, for example, 0.01 μm, 0.02 μm, 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, or 1.9 μm, but is not limited to the values ​​listed, and other values ​​within that range that are not listed are also applicable.

[0068] In one embodiment, with the total mass of the multi-stage cobalt-containing positive electrode material being 100%, the mass content of the cobalt-containing material A1 is 50-90%. For example, it may be 50%, 60%, 70%, 80%, or 90%, but is not limited to the values ​​listed, and other values ​​within that range that are not listed are also applicable.

[0069] In one embodiment, with the total mass of the multi-stage cobalt-containing positive electrode material being 100%, the mass content of the cobalt-containing material B1 is 10-30%. For example, it may be 10%, 12%, 15%, 17%, 20%, 25%, 27%, or 30%, but is not limited to the values ​​listed, and other values ​​within that range that are not listed are also applicable.

[0070] In one embodiment, with the total mass of the multi-stage cobalt-containing cathode material being 100%, the mass content of the active material is 5-20%. For example, it may be 5%, 7%, 10%, 12%, 15%, 17%, or 20%, but is not limited to the values ​​listed, and other values ​​within that range that are not listed are also applicable.

[0071] In one embodiment, the cobalt-containing material A1, the cobalt-containing material B1, and the active material each independently contain a doping element.

[0072] In this application, the doping elements in cobalt-containing material A1 and cobalt-containing material A are the same, the doping elements in cobalt-containing material B1 and cobalt-containing material B are the same, and the doping elements in the active material and the powdered active material are the same.

[0073] In a third aspect, the present application provides a lithium-ion battery wherein the positive electrode of the lithium-ion battery includes a multi-stage cobalt-containing positive electrode material as described in the second aspect.

[0074] The range of numerical values ​​described in this application includes not only the point values ​​listed above, but also any point values ​​between the ranges of numerical values ​​not listed above. For the sake of space and simplicity, specific point values ​​included in the range are not comprehensively illustrated in this application. [Effects of the Invention]

[0075] Compared to conventional technology, this invention offers the following beneficial effects.

[0076] (1) The present invention provides a method for preparing a multi-stage cobalt-containing cathode material. By performing particle size grading using the sol method, the organic framework related to the sol precursor can inhibit grain boundary transitions during the sintering process, effectively suppressing the aggregation of small particles. This solves the problem of uneven dispersion in particle size grading between large and small particles. The powdery active material formed after heating the sol precursor can be uniformly distributed on the surfaces and in the gaps between cobalt-containing material A and cobalt-containing material B. Particles with uniform grading dispersion can improve tap density and volume. Simultaneously, by performing coating using the sol method and mixing the coated sol precursor with the mixed material and sintering, the uniformity of the coating can be improved.

[0077] (2) The multi-stage cobalt-containing cathode material prepared by the method of the present invention has a high press density, good material crystallinity and uniformity, and excellent capacitance and cycle performance under high voltage.

[0078] After reading and understanding the detailed explanation, other aspects can be understood. [Modes for carrying out the invention]

[0079] The technical proposal of this application will be further described below with reference to specific embodiments.

[0080] Example 1 This embodiment provides a method for preparing a multi-stage cobalt-containing cathode material. Specifically, it includes the following:

[0081] (1) 600 g of Co3O4 and 290 g of lithium carbonate were taken, provided that the Co3O4 was doped with 9000 ppm of Al and 1000 ppm of Mg, and its particle size D50 = 17 μm. The mixture was mixed in a mixer at 800 r / min for 30 min to obtain a homogeneous mixture. The mixture was placed in a muffle furnace and heated to 750°C at a heating rate of 4°C / min and held for 120 min, then heated to 1060°C at a heating rate of 4°C / min and held for 10 h, after which it was allowed to cool naturally. After that, it was crushed using a jaw crusher, rollers, and a jet mill. Finally, it was sieved through a 200 mesh to obtain micron-order large particle lithium cobalt oxide A, which is a single crystal with a particle size D50 = 18 μm.

[0082] (2) 600 g of Co3O4 and 290 g of lithium carbonate were taken, wherein the Co3O4 was doped with 9500 ppm of Al and 2000 ppm of Mg, and its particle size D50 = 4 μm. The mixture was mixed in a mixer at 800 r / min for 30 min to obtain a homogeneous mixture. The above mixture was placed in a muffle furnace and heated to 750°C at a heating rate of 4°C / min and held for 120 min, then heated to 1060°C at a heating rate of 4°C / min and held for 10 h, after which it was allowed to cool naturally with an airflow rate of 30 L / min. After that, it was crushed using a jaw crusher, rollers and a jet mill. Finally, it was sieved through a 200 mesh to obtain micron-order small particles of lithium cobalt oxide B, which are single crystal small particles with a particle size D50 = 6 μm.

[0083] (3) Cobalt oxalate and lithium nitrate were added to a Li / Co ratio of 1.05, a chelating agent (i.e., ethanol) was added, and a dopant was added. The mixture was stirred and mixed to form a suspension. The dopant was a mixture of aluminum nitrate, magnesium nitrate, and titanium nitrate, with an Al content of 10,000 ppm, a Mg content of 2,000 ppm, and a Ti content of 2,000 ppm. The suspension was heated to 120°C for 2 hours under conditions with an external condensation reflux apparatus. The solid reacted completely and dissolved, and the solution became clear, forming a highly crosslinked sol precursor Cp1.

[0084] (4) Lithium cobaltate A and lithium cobaltate B are added to sol precursor Cp1, and the mixture is stirred at high speed at 1500 r / min for 10 min with a solid mass ratio of 8:1.5:0.5 in A, B, and Cp1 to thoroughly disperse the particulate matter of A and B in the sol precursor. The mixture is then heated at 200°C for 2 hours until the sol precursor Cp1 forms powder Cp2 and is thoroughly dispersed on the surface and in the gaps of semi-finished products A and B. The particle size D50 of Cp2 is 0.5 ± 0.4 μm, and the mixture of A, B, and Cp2 is the second sintered precursor D.

[0085] (5) A suspension was formed by stirring and mixing a coating element-containing salt with a chelating agent (i.e., ethanol). The coating element-containing salt was a mixture of titanium nitrate, zirconium nitrate, and yttrium nitrate, with a Ti content of 500 ppm, a Zr content of 300 ppm, and a Y content of 500 ppm. The suspension was heated to 120°C for 2 hours under conditions where a condensation reflux apparatus was attached externally. The solid reacted completely and dissolved, and the solution became clear, forming a highly crosslinked coating sol precursor P.

[0086] (6) The coating sol precursor P was added to the second sintered precursor D and mixed in a mixer at 800 r / min for 30 min to obtain a homogeneous mixture. The mixture was heated to 700°C at a heating rate of 4°C / min under an air atmosphere and held at this temperature for 3 hours. Subsequently, crushing and sieving processes were carried out sequentially to obtain the multi-stage cobalt-containing cathode material.

[0087] The multi-stage cobalt-containing cathode material is a mixed grading material of cobalt-containing material A1, cobalt-containing material B1, and active material Cp3. Cobalt-containing material A1 includes a lithium cobalt oxide A substrate and an oxide coating layer applied to the surface of the substrate, with a particle size D50 of 18.5 μm. Cobalt-containing material B1 includes a lithium cobalt oxide B substrate and an oxide coating layer applied to the surface of the substrate, with a particle size D50 of 6.5 μm. Active material Cp3 includes a lithium cobalt oxide substrate (corresponding to powdered material Cp2) and an oxide coating layer applied to the surface of the substrate. Active material Cp3 is uniformly distributed on the surfaces and in the gaps between cobalt-containing material A1 and cobalt-containing material B1. The total particle size D50 of the multi-stage cobalt-containing cathode material is 15.5 μm. With the total mass of the multi-stage cobalt-containing cathode material being taken as 100%, the mass contents of cobalt-containing material A1, cobalt-containing material B1, and active material Cp3 are 80%, 15%, and 5%, respectively.

[0088] Example 2 This embodiment provides a method for preparing a multi-stage cobalt-containing cathode material. Specifically, it includes the following:

[0089] (1) Micron-sized lithium cobalt oxide A was prepared using the same method as in Example 1.

[0090] (2) Micron-order small particles of lithium cobalt oxide B were prepared using the same method as in Example 1.

[0091] (3) Cobalt acetate and lithium nitrate were added to a Li / Co ratio of 1.05, a chelating agent (i.e., ethanol) was added, and a dopant was added. The mixture was stirred and mixed to form a suspension. The dopant was a mixture of zirconium nitrate, nickel nitrate, and manganese nitrate, with a Zr content of 1000 ppm, a Ni content of 2000 ppm, and a Mn content of 2000 ppm. The suspension was heated to 120°C for 2 hours under conditions with an external condensation reflux apparatus. The solid reacted completely and dissolved, and the solution became clear, forming a highly crosslinked sol precursor Cp1.

[0092] (4) Lithium cobalt oxide A and lithium cobalt oxide B are added to the sol precursor Cp1, and the mixture is stirred at high speed at 1500 r / min for 10 minutes with a solid content mass ratio of 8:1.5:0.5 in A, B, and Cp1 to thoroughly disperse the particulate matter of A and B in the sol precursor. The mixture is then heated at 200°C for 2 hours until the sol precursor Cp1 forms powder Cp2 and is thoroughly dispersed on the surface and in the gaps of semi-finished products A and B. The mixture of A, B, and Cp2 is the second sintered precursor D.

[0093] (5) A suspension was formed by stirring and mixing a coating element-containing salt with a chelating agent (i.e., ethanol). The coating element-containing salt was a mixture of nickel nitrate, manganese nitrate, magnesium nitrate, zirconium nitrate, aluminum nitrate, and titanium nitrate, with Ni content of 500 ppm, Mn content of 800 ppm, Mg content of 300 ppm, Zr content of 700 ppm, Al content of 500 ppm, and Ti content of 400 ppm. The suspension was heated to 120°C for 2 hours under conditions with an external condensation reflux apparatus. The solid reacted completely and dissolved, and the solution became clear, forming a highly crosslinked coating sol precursor P.

[0094] (6) The coating sol precursor P was added to the second sintered precursor D and mixed in a mixer at 800 r / min for 30 min to obtain a homogeneous mixture. The mixture was heated to 700°C at a heating rate of 4°C / min under an air atmosphere and maintained at that temperature for 10 hours. Subsequently, crushing and sieving processes were carried out sequentially to obtain the multi-stage cobalt-containing cathode material.

[0095] The multi-stage cobalt-containing cathode material is a mixed grading material of cobalt-containing material A1, cobalt-containing material B1, and active material Cp3. Cobalt-containing material A1 includes a lithium cobalt oxide A substrate and an oxide coating layer coated on the surface of the substrate; cobalt-containing material B1 includes a lithium cobalt oxide B substrate and an oxide coating layer coated on the surface of the substrate; and active material Cp3 includes a lithium cobalt oxide substrate (corresponding to powdered material Cp2) and an oxide coating layer coated on the surface of the substrate. Active material Cp3 is uniformly distributed on the surfaces and in the gaps between cobalt-containing material A1 and cobalt-containing material B1. The total particle size D50 of the multi-stage cobalt-containing cathode material is 15.5 μm. With the total mass of the multi-stage cobalt-containing cathode material being taken as 100%, the mass contents of cobalt-containing material A1, cobalt-containing material B1, and active material Cp3 are 85%, 15%, and 5%, respectively.

[0096] Example 3 This embodiment provides a method for preparing a multi-stage cobalt-containing cathode material. Specifically, it includes the following:

[0097] (1) Micron-sized lithium cobalt oxide A was prepared using the same method as in Example 1.

[0098] (2) Micron-order small particles of lithium cobalt oxide B were prepared using the same method as in Example 1.

[0099] (3) Nickel nitrate, cobalt nitrate, manganese nitrate, and lithium nitrate were added in a ratio of 5:2:3, a chelating agent (i.e., ethanol) was added, and a dopant was added. The mixture was stirred and mixed to form a suspension. The dopant was a mixture of titanium nitrate, magnesium nitrate, and zirconium nitrate, with a Ti content of 600 ppm, a Zr content of 400 ppm, and a Mg content of 800 ppm. The suspension was heated to 120°C for 2 hours under conditions with an external condensation reflux apparatus. The solid had completely reacted and dissolved, and the solution had become clear, forming a highly crosslinked sol precursor Cp1.

[0100] (4) A suspension was formed by stirring and mixing a coating element-containing salt with a chelating agent (i.e., ethanol). The coating element-containing salt was a mixture of titanium nitrate, zirconium nitrate, and yttrium nitrate, with a Ti content of 500 ppm, a Zr content of 300 ppm, and a Y content of 500 ppm. The suspension was heated to 120°C for 2 hours under conditions where a condensation reflux apparatus was attached externally. The solid reacted completely and dissolved, and the solution became clear, forming a highly crosslinked coating sol precursor P.

[0101] (5) Lithium cobalt oxide A and lithium cobalt oxide B are added to the sol precursor Cp1, and the mixture is stirred at high speed at 1500 r / min for 10 minutes with a solid content mass ratio of 8:1.5:0.5 in A, B, and Cp1 to thoroughly disperse the particulate matter of A and B in the sol precursor. The mixture is then heated at 120°C for 2 hours until the sol precursor Cp1 forms powder Cp2 and is thoroughly dispersed on the surface and in the gaps of semi-finished products A and B. The mixture of A, B, and Cp2 is the second sintered precursor D.

[0102] (6) The coated sol precursor P was added to the second sintered precursor D and mixed in a mixer at 800 r / min for 30 min to obtain a homogeneous mixture. The mixture was heated to 900°C at a heating rate of 4°C / min under an air atmosphere and maintained at that temperature for 10 hours. Subsequently, crushing and sieving processes were carried out sequentially to obtain the multi-stage cobalt-containing cathode material.

[0103] The multi-stage cobalt-containing cathode material is a mixed grading material of cobalt-containing material A1, cobalt-containing material B1, and active material Cp3. Cobalt-containing material A1 includes a lithium cobalt oxide A substrate and an oxide coating layer coated on the surface of the substrate; cobalt-containing material B1 includes a lithium cobalt oxide B substrate and an oxide coating layer coated on the surface of the substrate; and active material Cp3 includes a lithium nickel cobalt manganese oxide substrate (corresponding to powdered material Cp2) and an oxide coating layer coated on the surface of the substrate. Active material Cp3 is uniformly distributed on the surfaces and in the gaps between cobalt-containing material A1 and cobalt-containing material B1. The total particle size D50 of the multi-stage cobalt-containing cathode material is 15.0 μm. With the total mass of the multi-stage cobalt-containing cathode material being taken as 100%, the mass contents of cobalt-containing material A1, cobalt-containing material B1, and active material Cp3 are 85%, 15%, and 5%, respectively.

[0104] Example 4 The only difference between this embodiment and Embodiment 1 is that in step (4), the mass ratio of solids in A, B, and Cp1 is adjusted to 8:1.8:0.2.

[0105] Example 5 The only difference between this embodiment and Embodiment 1 is that in step (4), the mass ratio of solids in A, B, and Cp1 is adjusted to 8:0.8:1.2.

[0106] Example 6 The only difference between this example and Example 1 is that the particle size D50 of the powdered material Cp2 is adjusted to 0.1 μm.

[0107] Example 7 The only difference between this example and Example 1 is that the particle size D50 of the powdered material Cp2 is adjusted to 5 μm.

[0108] Comparative Example 1 The only difference between this comparative example and Example 1 is that in step (4), lithium cobalt oxide A and lithium cobalt oxide B were not added to the sol precursor Cp1, but were heated directly to form powder Cp2 from the sol precursor Cp1, and then the temperature was raised to 1000°C at a heating rate of 4°C / min and maintained for 10 hours before being allowed to cool naturally, resulting in a single-crystal small particle lithium cobalt oxide C with an air permeability of 30 L / min and a particle size D50 = 0.5 μm. Lithium cobalt oxide A, B, and C were then mixed at 800 r / min for 30 minutes, and the three components A, B, and C were thoroughly mixed in a cobalt content ratio of 8:1.5:0.5 to obtain a second-sintered precursor.

[0109] Comparative Example 2 The only difference between this comparative example and Example 1 is that steps (3) and (4) are replaced with "Lithium cobaltate A and lithium cobaltate B were mixed at 800 r / min for 30 minutes, and the particulate matter of A and B was thoroughly mixed with a cobalt content ratio of 8:2 for each to obtain a second-sintered precursor D."

[0110] Comparative Example 3 The only difference between this comparative example and Comparative Example 1 is that in step (4), lithium cobaltate B was omitted, and lithium cobaltate A and C were thoroughly mixed with a cobalt content ratio of 8:2 for each of them, to obtain a precursor that was sintered a second time.

[0111] Comparative Example 4 The only difference between this comparative example and Comparative Example 1 is that in step (4), lithium cobaltate A was omitted, and lithium cobaltate B and C were thoroughly mixed with a cobalt content ratio of 8:2 for each of the lithium cobaltate B and C to obtain a precursor that was sintered a second time.

[0112] Performance testing Cobalt-containing cathode materials, Super P, and PVDF from Examples 1-7 and Comparative Examples 1-4 were dissolved in N-methylpyrrolidone in a mass ratio of 95:5:5, coated, and dried to obtain a cathode sheet. The cathode sheet, separator, and negative electrode lithium sheet were assembled into a lithium-ion battery. The electrolyte used was 1M LiPF6DMC+EMC+EC.

[0113] (1) Press Density Test: A press density test was performed on powder using a press powder resistance meter of model number PRCD3100 developed by China Yuanneng Technology Co., Ltd. Test parameters: The upper indenter applied pressure to the powder sequentially at 20 MPa intervals from 10 to 200 MPa, and the pressure was held for 10 seconds. The value at a pressure of 150 MPa was read and the press density result was calculated.

[0114] (2) Capacity test: The battery was charged and discharged at 3.0V to 4.55V and 0.2C / 0.2C, and the initial discharge capacity of the battery was recorded.

[0115] (3) Cycle test: At 45°C, the battery was charged and discharged at 3.0~4.59V and 1C / 1C for 30 cycles, and the capacity retention rate was recorded.

[0116] The test results are shown in Table 1.

[0117] [Table 1]

[0118] analysis: As can be seen from the data results of Examples 1 to 3, the present invention performs particle size grading using the sol method, and the organic framework related to the sol precursor can inhibit grain boundary transitions during the sintering process, effectively suppressing the aggregation of small particles, thereby solving the problem of non-uniform dispersion in particle size grading of large and small particles. At the same time, coating can be performed using the sol method to improve the uniformity of the coating. The multi-stage cobalt-containing cathode material prepared by the method of the present invention has a high press density, good material crystallinity and uniformity, and excellent capacitance and cycle performance under high voltage.

[0119] As can be seen from the data results of Examples 1 and 4-5, if the solid content at Cp1 is too low, the volume decreases and the press density decreases, and if the solid content at Cp1 is too high, the cycle performance decreases and the press density decreases.

[0120] Example 1 and Example 6~7 As can be seen from the data results, when the particle size D50 of the powdered material Cp2 is small, cycle performance and press density decrease, and when the particle size D50 of the powdered material Cp2 is large, cycle performance and press density also decrease.

[0121] As can be seen from the data results of Example 1 and Comparative Examples 1-4, grading using a general mechanical mixing method reduces particle volume and cycle. Grading using only two types of cathode materials reduces particle press density.

[0122] The above are merely specific embodiments of the present application, but the applicant declares that the scope of protection of the present application is not limited thereto. A person skilled in the art should understand that any changes or substitutions that are readily conceivable by a person skilled in the art within the scope of the art disclosed herein fall within the scope of protection and disclosure of the present application.

Claims

1. Step (1) involves mixing the active material raw material, lithium source, and chelating agent, reacting them, and then obtaining a sol precursor. Step (2) involves mixing cobalt-containing material A, cobalt-containing material B, and the sol precursor described in step (1), and heating until the sol precursor forms a powdery active material to obtain a mixed material of cobalt-containing material A, cobalt-containing material B, and powdery active material. Step (3) includes mixing the mixed material and coating sol precursor described in step (2), sintering them, and obtaining a multi-stage cobalt-containing cathode material. The mass ratio of solid content in cobalt-containing material A, cobalt-containing material B, and sol precursor described in step (2) is 8:(0.9-1.7):(0.3-1.1), The particle size D50 of the cobalt-containing material A described in step (2) is 15 to 21 μm. The particle size D50 of the cobalt-containing material B described in step (2) is 3 to 9 μm. The particle size D50 of the powdered active material described in step (2) is 0.5 to 1.99 μm. A method for preparing a multi-stage cobalt-containing cathode material.

2. The active material raw material described in step (1) includes at least one of cobalt salts, nickel salts, manganese salts, iron salts, and phosphorus sources. The lithium source described in step (1) comprises at least one of lithium nitrate, lithium oxalate, lithium citrate, and lithium chloride. The chelating agent described in step (1) comprises an alcohol, wherein the alcohol comprises ethanol and / or ethylene glycol. The reaction temperature described in step (1) is 100 to 150°C. The reaction time described in step (1) is 1 to 3 hours. The preparation method according to claim 1.

3. The raw materials for the mixture according to step (1) further comprises a dopant and / or a dispersant, The doping element in the dopant comprises at least one of the elements Al, Mg, Ti, Ce, Nb, Sb, Cr, F, La, W, Y, V, Zr, Ni, and Mn. The doping element content in the sol precursor described in step (1) is 300 to 30,000 ppm. The preparation method according to claim 1.

4. The cobalt-containing material A described in step (2) is a single-crystal material, The cobalt-containing material A described in step (2) comprises lithium cobalt oxide and / or lithium nickelcobalt manganese oxide. The cobalt-containing material A described in step (2) contains a doping element, the doping element comprising at least one of the elements Al, Mg, Ce, Nb, Sb, Cr, F, La, W, V, Zr, Ni, and Mn. The doping element content in the cobalt-containing material A described in step (2) is 300 to 30,000 ppm. The preparation method according to claim 1.

5. The cobalt-containing material B described in step (2) is a single-crystal material, The cobalt-containing material B described in step (2) comprises lithium cobalt oxide and / or lithium nickelcobalt manganese oxide. The cobalt-containing material B described in step (2) contains a doping element, the doping element comprising at least one of the elements Al, Mg, Ce, Nb, Sb, Cr, F, La, W, V, Zr, Ni, and Mn. The doping element content in the cobalt-containing material B described in step (2) is 300 to 30,000 ppm. The preparation method according to claim 1.

6. In the mixing process described in step (2), stirring is performed, the stirring speed is 1000 to 2000 r / min, and the stirring time is 5 to 15 min. The heating temperature described in step (2) is 100 to 150°C. The heating time described in step (2) is 1 to 3 hours. The powdered active material described in step (2) includes one of the following: lithium cobaltate, lithium iron phosphate, or lithium nickel cobalt manganese. The preparation method according to claim 1.

7. The powdered active material described in step (2) is lithium cobalt oxide. The preparation method according to claim 6.

8. The method for preparing the coated sol precursor described in step (3) includes mixing a coating element-containing compound and a chelating agent, reacting them, and then obtaining the coated sol precursor. The coating element comprises at least one of the elements Ti, Zr, Y, Ce, Nb, Sb, Cr, F, La, W, and V. In a method for preparing a coated sol precursor, the chelating agent comprises an alcohol, and the alcohol comprises ethanol and / or ethylene glycol. In a method for preparing a coated sol precursor, the reaction temperature is 100 to 150°C, and the reaction time is 1 to 3 hours. The mass ratio of the mixed material and the coating sol precursor described in step (3) is (7-27):

3. The preparation method according to claim 1.

9. In the mixing process described in step (3), stirring is performed, the stirring speed is 600 to 1000 r / min, and the stirring time is 20 to 40 min. The sintering temperature described in step (3) is 600 to 800°C. The sintering time described in step (3) is 8 to 12 hours. The preparation method according to claim 1.

10. The multi-stage cobalt-containing positive electrode material is cobalt-containing material A １ Cobalt-containing material B １ and includes active materials, The aforementioned cobalt-containing material A １ Cobalt-containing material B １ The active material independently comprises a substrate and an oxide coating layer coated on the surface of the substrate, wherein the active material is a cobalt-containing material A １ and cobalt-containing material B １ It is uniformly distributed on the surface and in the gaps, The aforementioned cobalt-containing material A １ The particle size is 15-21 μm. The aforementioned cobalt-containing material B １ The particle size is 3 to 9 μm. The particle size of the active material is 0.5 to 1.99 μm. Taking the total mass of the cobalt-containing cathode material with the multi-stage structure as 100%, the cobalt-containing material A １ has a mass content of 50 to 90%, The total mass of the cobalt-containing positive electrode material in the multi-stage structure is taken as 100%, and the cobalt-containing material B １ The mass content is 10-30%, With the total mass of the multi-stage cobalt-containing cathode material being taken as 100%, the mass content of the active material is 5 to 20%. The aforementioned cobalt-containing material A １ Cobalt-containing material B １ And the active material independently contains doping elements, The preparation method according to any one of claims 1 to 9.

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