Multi-stage cobalt-containing positive electrode material, its preparation method, 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] The present application belongs to the technical field of batteries and relates to a multi-stage cobalt-containing positive electrode material and a preparation method thereof, and a lithium ion battery. [Background technology]

[0002] In recent years, with the rapid development of various portable electronic devices and electric vehicles, people's demands for lithium-ion battery performance have increased. Therefore, to meet the needs of different segments of the market, it is becoming increasingly important to develop lithium-ion batteries with high capacity, high power conversion, and cycle stability for various application scenarios. Currently, lithium cobalt oxide still accounts for a large share of the lithium-ion battery cathode materials used in 3C products due to its excellent theoretical capacity and tap density. However, to meet the recurring needs of consumer products, the energy density and cycle life of lithium cobalt oxide cathode materials are facing increasing challenges. There are two most straightforward ways to improve the energy density of lithium cobalt oxide: improving its tap density and its operating voltage.

[0003] While good tap density can be achieved using lithium cobalt oxide particles with large crystal grain sizes, excessively large crystal grain sizes can affect the electrical performance of the material. Therefore, in practical applications, a two-particle size grating method (large and small) can be used to achieve good electrical performance and energy density. The small particles in the resulting finished product tend to aggregate and form clumps, which can affect the uniformity of the material and further impair its electrical performance. At the same time, the irregular distribution of large and small particles results in large, uneven gaps between the particles, making it difficult to further improve the tap density.

[0004] Increasing the operating voltage of lithium cobalt oxide can further release lithium and improve the capacity of the lithium cobalt oxide. However, higher operating voltages can lead to more side reactions and irreversible phase transitions, which can accelerate the decay of the lithium cobalt oxide's electrical performance. Typically, solid-state doping and solid-state coating can be used to prevent lithium cobalt oxide from losing its effectiveness. For lithium cobalt oxide with particle size grading, solid-state coating is limited by kinetic factors, making it difficult to achieve a uniform coating effect. Defects due to uneven coating of the material can accelerate the occurrence of side reactions at high voltages, reducing its cycle performance.

[0005] Therefore, how to further improve the tap density of lithium cobalt oxide positive electrode materials, the dispersion of grading particles, and the uniformity of coating have become technical problems that require urgent research. Summary of the Invention [Problem to be solved by the invention]

[0006] The following is a general summary of the subject matter described in detail herein, which is not intended to limit the scope of the claims.

[0007] In response to the deficiencies of the prior art, the present application provides a multi-layered cobalt-containing positive electrode material, a preparation method thereof, and a lithium-ion battery. By grading the particle size using a sol method, the organic framework of the sol precursor can inhibit grain boundary transition during sintering, effectively suppressing the aggregation of small particles, thereby solving the problem of uneven particle size grading distribution between large and small particles. The powdered active material formed after heating the sol precursor can be uniformly distributed on the surfaces and between the cobalt-containing materials A and B. The uniformly graded particles improve tap density and press density, thereby improving capacity. At the same time, coating using a sol method and mixing and sintering the coated sol precursor and the mixed material can improve the uniformity of the coating. [Means for solving the problem]

[0008] To achieve this goal, the present application adopts the following technical solutions.

[0009] In a first aspect, the present application provides: Step (1) of mixing and reacting an active material raw material, a lithium source, and a chelating agent to obtain a sol precursor; Step (2) of mixing the cobalt-containing material A, the cobalt-containing material B, and the sol precursor described in step (1) and heating the mixture until the sol precursor forms a powdered active material, thereby obtaining a mixed material of the cobalt-containing material A, the cobalt-containing material B, and the powdered active material; and step (3) mixing the mixed material and the coated sol precursor according to step (2) and sintering the mixture to obtain a multi-stage cobalt-containing cathode material.

[0010] This application provides a method for preparing a multi-stage cobalt-containing positive electrode material, in which particle size grading is performed using a sol method. The organic framework of the sol precursor inhibits grain boundary transition during sintering, effectively suppressing aggregation of small particles, thereby solving the problem of uneven particle size grading distribution between large and small particles. The powdered active material formed after heating the sol precursor can be uniformly distributed on the surfaces and between cobalt-containing materials A and B. The particles with uniform grading distribution can improve tap density and press density, thereby improving capacity. At the same time, coating is performed using a sol method, and the coated sol precursor and mixed material are mixed and sintered, thereby improving coating uniformity.

[0011] In a preferred technical solution of the present application, the raw active material described in step (1) contains at least one of a cobalt salt, a nickel salt, a manganese salt, an iron salt, and a phosphorus source, and is preferably a cobalt salt.

[0012] In the present application, the active material raw material in step (1) may be selected solely from a cobalt salt, which is one of the raw materials for the lithium cobaltate active material. At the same time, the active material raw material typically includes, but is not limited to, a combination of a cobalt salt, a nickel salt, and a manganese salt, a combination of a cobalt salt and a nickel salt, a combination of a cobalt salt and a manganese salt, a combination of a nickel salt and a manganese salt, or a combination of an iron salt and a phosphorus source. The combination of a cobalt salt, a nickel salt, and a manganese salt may be a mixture of a cobalt salt, a nickel salt, and a manganese salt, or a ternary complex salt of cobalt, nickel, and manganese. The combination of a cobalt salt and a nickel salt may be a mixture of a cobalt salt and a nickel salt, or a binary complex salt of cobalt and nickel, and the rest are similar.

[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 comprises at least one of phosphoric acid, iron phosphate, and iron ammonium 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 in step (1) is alcohol and alcohol contains ethanol and / or ethylene glycol.

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

[0021] In one embodiment, the doping elements in the dopant include 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, when the doping element in the dopant is present as a cation, the corresponding anion comprises an oxalate, phosphate, acetate, nitrate, sulfate, or chloride ion, or the like.

[0023] In one embodiment, the content of the doping element in the sol precursor described in step (1) is 300 to 30,000 ppm, such as 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 listed values, and other values ​​within the range not listed also apply.

[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 various polymerization degrees.

[0025] In one embodiment, the temperature of the reaction 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 listed values, and other values ​​not listed within the range of values ​​also apply.

[0026] In one embodiment, the reaction time described in step (1) 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 listed values, and other values ​​within the range not listed also apply.

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

[0028] In one embodiment, the cobalt-containing material A described in step (2) comprises lithium cobalt oxide 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, 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 listed values, and other values ​​within the range that are not listed also apply.

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

[0031] In one embodiment, the content of the doping element in the cobalt-containing material A 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 listed values, and other values ​​not listed within the range of the values ​​also apply.

[0032] In one embodiment, the method for preparing the cobalt-containing material A includes mixing tricobalt tetroxide and lithium carbonate, sintering the mixture in stages, and then pulverizing and sieving the mixture to obtain the cobalt-containing material A. The temperature range for the staged 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] In the preferred technical solution of the present application, the cobalt-containing material B 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 nickel cobalt 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 listed values, and other values ​​not listed within the range of the values ​​also apply.

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

[0038] In one embodiment, the content of the doping element 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 listed values, and other values ​​not listed within the range of the values ​​also apply.

[0039] In this application, the doping element is gradient distributed in the multi-stage 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 the mixture stepwise, and then pulverizing 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 the cobalt-containing material A, the cobalt-containing material B, and the solid content in the sol precursor in step (2) is 8:(0.9-1.7):(0.3-1.1). The selected range (0.9-1.7) for the cobalt-containing material B may be, for example, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, or 1.7, and the selected range (0.3-1.1) for the solid content in the sol precursor 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 listed values, and other unlisted values ​​within the ranges also apply.

[0042] In this application, if the solids content in the sol precursor is too low, the capacity and press density will decrease, and if the solids content in the sol precursor is too high, the cycle performance and press density will decrease.

[0043] In a preferred technical solution of the present application, the mixing process in step (2) involves stirring. The stirring speed is 1000 to 2000 r / min, such as 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, such as 5 min, 7 min, 9 min, 10 min, 12 min, or 15 min, but is not limited to these values, and other values ​​within the ranges not specified also apply.

[0044] In one embodiment, the heating temperature 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 listed values, and other values ​​not listed within the range of values ​​also apply.

[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 listed values, and other values ​​not listed within the range of the values ​​also apply.

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

[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 listed values, and other values ​​within the range not listed also apply.

[0049] In the present application, if the particle diameter D50 of the powdered active material is small, the cycle performance and press density decrease, and if the particle diameter D50 of the powdered active material is too large, the cycle performance and press density decrease.

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

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

[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 an oxalate ion, a phosphate ion, an acetate ion, a nitrate ion, a sulfate ion, or a chloride ion, or the like.

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

[0055] In one embodiment, in the method for preparing a coated sol precursor, the reaction temperature is 100 to 150°C, and may be, for example, 100°C, 110°C, 120°C, 130°C, 140°C, or 150°C, and the reaction time 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 listed values, and other values ​​within the ranges not listed also apply.

[0056] In one embodiment, the mass ratio of the mixed material to the coating sol precursor described in step (3) is (7 to 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 listed values, and other unlisted values ​​within the range of the values ​​also apply.

[0057] In a preferred technical solution of the present application, the mixing process in step (3) involves 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 these numerical values, and other unspecified numerical values ​​within the numerical ranges also apply.

[0058] In one embodiment, the sintering temperature 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 listed values, and other values ​​not listed within the range of the values ​​also apply.

[0059] In one embodiment, the sintering time described in step (3) is 8 to 12 hours, for example, 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours, but is not limited to the listed values, and other values ​​not listed within the range of the values ​​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] In the preferred technical solution of the present application, the multi-stage cobalt-containing positive electrode material includes a cobalt-containing material A1, a cobalt-containing material B1 and an active material.

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

[0064] In this application, the cobalt-containing material A1, the cobalt-containing material B1, and the active material each independently include a substrate and an oxide coating layer coated on the substrate. This specifically means that the cobalt-containing material A1 includes a cobalt-containing material A substrate and an oxide coating layer coated on the substrate's surface, the cobalt-containing material B1 includes a cobalt-containing material B substrate and an oxide coating layer coated on the substrate's surface, and the active material includes a powdered active material substrate and an oxide coating layer coated on the substrate's surface. The oxide coating layers of the cobalt-containing material A1, the cobalt-containing material B1, and the active material are the same in terms of type and content. The coating elements in the oxide coating layer include at least one of 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 listed values, and other values ​​within the range that are not listed also apply.

[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 listed values, and other values ​​within the range that are not listed also apply.

[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 listed values, and other unlisted values ​​within the range also apply.

[0068] In one embodiment, the mass content of the cobalt-containing material A1 is 50 to 90% relative to the total mass of the multi-stage cobalt-containing positive electrode material, and may be, for example, 50%, 60%, 70%, 80%, or 90%, but is not limited to the listed values, and any other unlisted values ​​within the range of the values ​​also apply.

[0069] In one embodiment, the mass content of the cobalt-containing material B1 is 10 to 30% relative to the total mass of the multi-stage cobalt-containing positive electrode material, and may be, for example, 10%, 12%, 15%, 17%, 20%, 25%, 27%, or 30%, but is not limited to the listed values, and any other unlisted values ​​within the range of the values ​​also apply.

[0070] In one embodiment, the mass content of the active material is 5 to 20%, for example, 5%, 7%, 10%, 12%, 15%, 17%, or 20%, based on the total mass of the multi-stage cobalt-containing positive electrode material being 100%, but is not limited to the listed values, and any other unlisted values ​​within the range also apply.

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

[0072] In the present application, the doping elements in the cobalt-containing material A1 and the cobalt-containing material A are the same, the doping elements in the cobalt-containing material B1 and the cobalt-containing material B are the same, and the doping elements in the active material and the powdery 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 comprises the multi-staged cobalt-containing positive electrode material according to the second aspect.

[0074] The ranges of values ​​described herein include not only the recited point values ​​but also any point values ​​between the recited point values. For reasons of space and clarity, the present application does not exhaustively exemplify specific point values ​​included in the ranges. [Effects of the Invention]

[0075] Compared with the prior art, the present application has the following beneficial effects:

[0076] (1) This application provides a method for preparing a multi-stage cobalt-containing positive electrode material. By using a sol method to perform particle size grading, the organic framework of the sol precursor can inhibit grain boundary transition during sintering, effectively suppressing the aggregation of small particles, thereby solving the problem of uneven particle size grading distribution between large and small particles. The powdered active material formed after heating the sol precursor can be uniformly distributed on the surfaces and in the gaps of cobalt-containing material A and cobalt-containing material B. The uniformly distributed particles can improve tap density and capacity. At the same time, coating is performed using a sol method, and the coated sol precursor and mixed material are mixed and sintered, thereby improving the uniformity of the coating.

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

[0078] Other aspects may be appreciated after reading and understanding the detailed description. DETAILED DESCRIPTION OF THE INVENTION

[0079] The technical solution of the present application will be further described below through specific embodiments.

[0080] Example 1 This example provides a method for preparing a multi-stage cobalt-containing positive electrode material, specifically including:

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

[0082] (2) 600 g of Co3O4 and 290 g of lithium carbonate were taken, with the Co3O4 doped with 9500 ppm Al and 2000 ppm Mg, and the particle size D50 was 4 μm. The mixture was mixed in a mixer at 800 r / min for 30 minutes to obtain a uniform mixture. The mixture was then placed in a muffle furnace, heated to 750°C at a rate of 4°C / min, maintained at this temperature for 120 minutes, then heated to 1060°C at a rate of 4°C / min, maintained at this temperature for 10 hours, and then naturally cooled with an airflow rate of 30 L / min. The mixture was then crushed using a jaw crusher, roller mill, and jet mill. Finally, the mixture was sieved through a 200-mesh sieve to obtain micron-order small particles of lithium cobalt oxide B, which were single-crystal small particles with a particle size D50 of 6 μm.

[0083] (3) Cobalt oxalate and lithium nitrate were added at a Li / Co ratio of 1.05, and a chelating agent (i.e., ethanol) and a dopant were added. The mixture was stirred 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, an Mg content of 2,000 ppm, and an Ti content of 2,000 ppm. The suspension was heated to 120°C under external reflux conditions and reacted for 2 hours. The solids were completely reacted and dissolved, resulting in a clear solution, forming a highly crosslinked sol precursor Cp1.

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

[0085] (5) The coating element-containing salt and the chelating agent (i.e., ethanol) were stirred to form a suspension. 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 under conditions with an external condensation reflux device and reacted for 2 hours. The solids had completely reacted and dissolved, resulting in a clear solution, forming a highly crosslinked coating sol precursor P.

[0086] (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 minutes to obtain a uniform mixture. The mixture was heated to 700°C at a heating rate of 4°C / min in an air atmosphere and maintained at that temperature for 3 hours. After that, the mixture was crushed and sieved sequentially to obtain the multi-stage cobalt-containing positive electrode material.

[0087] The multi-stage cobalt-containing positive electrode material is a mixed grade 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 substrate surface, 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 coated on the substrate surface, with a particle size D50 of 6.5 μm. Active material Cp3 includes a lithium cobalt oxide substrate (corresponding to powder Cp2) and an oxide coating layer coated on the substrate surface. Active material Cp3 is uniformly distributed on the surfaces and in the gaps between cobalt-containing material A1 and cobalt-containing material B1. The particle size D50 of the entire multi-stage cobalt-containing positive electrode material is 15.5 μm. With the total mass of the multi-stage cobalt-containing positive electrode material being 100%, the mass contents of the cobalt-containing material A1, the cobalt-containing material B1 and the active material Cp3 are 80%, 15% and 5%, respectively.

[0088] Example 2 This example provides a method for preparing a multi-stage cobalt-containing positive electrode material, specifically including:

[0089] (1) Using the same method as in Example 1, lithium cobalt oxide A having large particles on the order of microns was prepared.

[0090] (2) Using the same method as in Example 1, micron-order small particle lithium cobalt oxide B was prepared.

[0091] (3) Cobalt acetate and lithium nitrate were added at a Li / Co ratio of 1.05, and a chelating agent (i.e., ethanol) and a dopant were added. The mixture was stirred 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 under external reflux conditions and reacted for 2 hours. The solids were completely reacted and dissolved, resulting in a clear solution, forming a highly crosslinked sol precursor Cp1.

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

[0093] (5) The coating element-containing salt and chelating agent (i.e., ethanol) were mixed by stirring to form a suspension. The coating element-containing salt was a mixture of nickel nitrate, manganese nitrate, magnesium nitrate, zirconium nitrate, aluminum nitrate, and titanium nitrate, with a 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 under conditions with an external condensation reflux device and reacted for 2 hours. The solids had completely reacted and dissolved, resulting in a clear solution, forming a highly crosslinked coating sol precursor P.

[0094] (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 minutes to obtain a uniform mixture. The mixture was heated to 700°C at a rate of 4°C / min in an air atmosphere and maintained at that temperature for 10 hours. After that, the mixture was crushed and sieved sequentially to obtain the multi-stage cobalt-containing positive electrode material.

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

[0096] Example 3 This example provides a method for preparing a multi-stage cobalt-containing positive electrode material, specifically including:

[0097] (1) Using the same method as in Example 1, lithium cobalt oxide A having large particles on the order of microns was prepared.

[0098] (2) Using the same method as in Example 1, micron-order small particle lithium cobalt oxide B was prepared.

[0099] (3) Nickel nitrate, cobalt nitrate, manganese nitrate, and lithium nitrate were added in a ratio of 5:2:3, and a chelating agent (i.e., ethanol) and dopant were added. The mixture was stirred 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 under external reflux conditions and reacted for 2 hours. The solids were completely reacted and dissolved, resulting in a clear solution, forming a highly crosslinked sol precursor Cp1.

[0100] (4) The coating element-containing salt and the chelating agent (i.e., ethanol) were stirred to form a suspension. 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 under conditions with an external condensation reflux device and reacted for 2 hours. The solids had completely reacted and dissolved, resulting in a clear solution, forming a highly crosslinked coating sol precursor P.

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

[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 minutes to obtain a uniform mixture. The mixture was heated to 900°C at a rate of 4°C / min in an air atmosphere and maintained at that temperature for 10 hours. After that, the mixture was crushed and sieved sequentially to obtain the multi-stage cobalt-containing positive electrode material.

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

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

[0105] Example 5 The only difference between this example and Example 1 is that in step (4), the mass ratio of the solid contents 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 powder 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 powder 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 directly heated to form powder Cp2 from the sol precursor Cp1. The sol precursor Cp1 was then heated to 1000°C at a heating rate of 4°C / min and maintained at that temperature for 10 hours, after which it was naturally cooled to obtain small single-crystal particles of lithium cobalt oxide C with a particle size D50 of 0.5μm and an aeration rate of 30L / min. The lithium cobalt oxides A, B, and C were then mixed at 800 r / min for 30 minutes, with the cobalt content ratio of A, B, and C being 8:1.5:0.5, and thoroughly mixed 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 cobalt oxide A and lithium cobalt oxide B were mixed at 800 r / min for 30 minutes, and the particulate materials A and B were thoroughly mixed at a cobalt content ratio of 8:2 between A and B 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 cobalt oxide B was omitted, and lithium cobalt oxides A and C were thoroughly mixed at a cobalt content ratio of 8:2 to obtain a second-sintered precursor.

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

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

[0113] (1) Press density test: A press density test was performed on the powder using a press powder resistivity meter, model PRCD3100, developed by China Yuan Neng Technology Co., Ltd. Test parameters: The upper indenter applied pressure to the powder in 20 MPa increments from 10 to 200 MPa, and the pressure was maintained for 10 seconds. The value at a pressure of 150 MPa was read and calculated to obtain the press density results.

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

[0115] (3) Cycle test: 30 cycles of charging and discharging at 45°C, 3.0 to 4.59 V, 1 C / 1 C, were performed, 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 uses a sol method to perform particle size grading, and the organic framework of the sol precursor can inhibit grain boundary transition during sintering, effectively suppressing the aggregation of small particles, thereby solving the problem of uneven distribution of particle size grading between large and small particles, and also improving the coating uniformity when coating using a sol method.The multi-stage cobalt-containing positive electrode material prepared by the present invention has a high press density, good crystallinity and uniformity of the material, and excellent capacity and cycle performance at high voltage.

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

[0120] As can be seen from the data results of Examples 1 and 5 to 6, when the particle diameter D50 of the powdered material Cp2 is small, the cycle performance and press density decrease, and when the particle diameter D50 of the powdered material Cp2 is large, the cycle performance and press density decrease.

[0121] As can be seen from the data results of Example 1 and Comparative Examples 1 to 4, grading using a typical mechanical mixing method reduces the capacity and cycle life of the particles, and grading using only two types of positive electrode materials reduces the pressed density of the particles.

[0122] The applicant declares that the above is only a specific embodiment of the present application, and the scope of protection of the present application is not limited thereto. It should be understood that any changes or substitutions that can be easily made by a person skilled in the art within the technical scope disclosed in the present application are within the scope of protection and disclosure of the present application.

Claims

1. Step (1) of mixing and reacting an active material raw material, a lithium source, and a chelating agent to obtain a sol precursor; Step (2) of mixing the cobalt-containing material A, the cobalt-containing material B, and the sol precursor described in step (1) and heating the mixture until the sol precursor forms a powdered active material, thereby obtaining a mixed material of the cobalt-containing material A, the cobalt-containing material B, and the powdered active material; and step (3) mixing the mixed material and the coated sol precursor according to step (2) and sintering the mixture to obtain a multi-stage cobalt-containing positive electrode material. A method for preparing a multi-stage cobalt-containing positive electrode material.

2. The active material raw material described in step (1) includes at least one of a cobalt salt, a nickel salt, a manganese salt, an iron salt, and a phosphorus source; Preferably, the lithium source described in step (1) comprises at least one of lithium nitrate, lithium oxalate, lithium citrate, and lithium chloride; Preferably, the chelating agent in step (1) comprises a polyhydric alcohol, wherein the polyhydric alcohol comprises ethanol and / or ethylene glycol; Preferably, the ingredients of the mixture described in step (1) further comprise a dopant and / or a dispersant; Preferably, the doping elements in said dopant comprise at least one of the elements Al, Mg, Ti, Ce, Nb, Sb, Cr, F, La, W, Y, V, Zr, Ni and Mn; Preferably, the content of the doping element in the sol precursor according to step (1) is 300-30000 ppm; Preferably, the temperature of the reaction described in step (1) is 100 to 150°C; Preferably, the reaction time described in step (1) is 1 to 3 h. The preparation method according to claim 1.

3. The cobalt-containing material A described in step (2) is a single crystal material, Preferably, the cobalt-containing material A described in step (2) comprises lithium cobalt oxide and / or lithium nickel cobalt manganese oxide; Preferably, the particle size D50 of the cobalt-containing material A described in step (2) is 15 to 21 μm; Preferably, the cobalt-containing material A described in step (2) contains a doping element, and the doping element includes at least one of Al, Mg, Ce, Nb, Sb, Cr, F, La, W, V, Zr, Ni and Mn elements; Preferably, the content of the doping element in the cobalt-containing material A described in step (2) is 300 to 30,000 ppm; 3. The preparation method according to claim 1 or 2.

4. The cobalt-containing material B described in step (2) is a single crystal material; Preferably, the cobalt-containing material B described in step (2) comprises lithium cobalt oxide and / or lithium nickel cobalt manganese oxide; Preferably, 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; Preferably, the particle size D50 of the cobalt-containing material B described in step (2) is 3 to 9 μm; Preferably, the cobalt-containing material B described in step (2) contains a doping element, and the doping element includes at least one of Al, Mg, Ce, Nb, Sb, Cr, F, La, W, V, Zr, Ni and Mn elements; Preferably, the content of the doping element in the cobalt-containing material B described in step (2) is 300 to 30,000 ppm; Preferably, the mass ratio of the cobalt-containing material A, the cobalt-containing material B and the solid content in the sol precursor described in step (2) is 8:(0.9 to 1.7):(0.3 to 1.1). The preparation method according to any one of claims 1 to 3.

5. The mixing process described in step (2) is accompanied by stirring, the stirring speed is 1000 to 2000 r / min, and the stirring time is 5 to 15 min; Preferably, the temperature of the heating described in step (2) is 100 to 150°C; Preferably, the heating time in step (2) is 1 to 3 h; Preferably, the powdered active material described in step (2) includes any one of lithium cobalt oxide, lithium iron phosphate, and lithium nickel cobalt manganese oxide; Preferably, 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, Preferably, the particle size D50 of the powder active material described in step (2) is 0.01 to 1.99 μm. The preparation method according to any one of claims 1 to 4.

6. The powdered active material described in step (2) is lithium cobalt oxide. The preparation method according to any one of claims 1 to 5.

7. The method for preparing the coated sol precursor according to step (3) includes mixing and reacting a coating element-containing compound and a chelating agent, and then obtaining the coated sol precursor; Preferably, the coating elements include at least one of Ti, Zr, Y, Ce, Nb, Sb, Cr, F, La, W and V elements; Preferably, in the method for preparing a coating sol precursor, the chelating agent comprises a polyhydric alcohol, the polyhydric alcohol comprising ethanol and / or ethylene glycol; Preferably, in the method for preparing a coating sol precursor, the reaction temperature is 100 to 150°C, and the reaction time is 1 to 3 hours; Preferably, the mass ratio of the mixed material and the coating sol precursor in step (3) is (7-27):3; The preparation method according to any one of claims 1 to 6.

8. The mixing process described in step (3) is accompanied by stirring, the stirring speed is 600 to 1000 r / min, and the stirring time is 20 to 40 min; Preferably, the sintering temperature in step (3) is 600 to 800°C; Preferably, the sintering time described in step (3) is 8 to 12 h. The preparation method according to any one of claims 1 to 7.

9. A multi-stage cobalt-containing positive electrode material prepared by the method of any one of claims 1 to 8.

10. The multi-stage cobalt-containing positive electrode material is a cobalt-containing material A １ , cobalt-containing material B １ and an active ingredient, The cobalt-containing material A １ , cobalt-containing material B １ and the active material independently includes a substrate and an oxide coating layer coated on the surface of the substrate, the active material including a cobalt-containing material A. １ and cobalt-containing material B １ uniformly distributed on the surface and in the gaps, Preferably, the cobalt-containing material A １ The particle size is 15 to 21 μm, Preferably, the cobalt-containing material B １ The particle size is 3 to 9 μm, Preferably, the particle size of the active material is between 0.01 and 1.99 μm; Preferably, the total mass of the multi-stage cobalt-containing positive electrode material is 100%, and the cobalt-containing material A １ The mass content of is 50 to 90%, Preferably, the total mass of the multi-stage cobalt-containing positive electrode material is 100%, and the cobalt-containing material B １ The mass content of is 10 to 30%, Preferably, the mass content of the active material is 5 to 20%, based on the total mass of the multi-stage cobalt-containing positive electrode material being 100%; Preferably, the cobalt-containing material A １ , cobalt-containing material B １ and the active material independently comprises a doping element; 10. The multi-stage cobalt-containing positive electrode material of claim 9.

11. A lithium ion battery comprising the multi-stage cobalt-containing positive electrode material of claim 9 or 10.

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