Multi-level structured cobalt-containing positive electrode material, preparation method therefor, and lithium ion battery

Abstract

Provided are a multi-level structured cobalt-containing positive electrode material, a preparation method therefor, and a lithium ion battery. The preparation method comprises: (1) mixing an active substance raw material, a lithium source and a chelating agent to react with each other so as to obtain a sol precursor; (2) mixing cobalt-containing material A, cobalt-containing material B and the sol precursor, and heating same until the sol precursor forms a powdered active substance, so as to obtain a mixture of cobalt-containing material A, cobalt-containing material B and the powdered active substance; and (3) mixing the mixture and a coating sol precursor, and sintering same to obtain the multi-level structured cobalt-containing positive electrode material. Using the method can solve the problem of uneven distribution of large and small-sized particles, and improve tap density, capacity and coating uniformity.

Description

A multi-level structure cobalt-containing positive electrode material, preparation method thereof, and lithium-ion battery Technical Field

[0001] The present application belongs to the field of battery technology and relates to a multi-level structure cobalt-containing positive electrode material, a preparation method thereof, and a lithium-ion battery. Background Art

[0002] In recent years, with the vigorous development of various portable electronic devices and electric vehicles, people's demand for the performance of lithium-ion batteries has continued to increase. Therefore, it has become increasingly important to develop lithium-ion batteries with high capacity, high rate and cycle stability for different application scenarios to meet the market needs of different segments. Among the lithium-ion battery positive electrode materials currently used in 3C products, lithium cobalt oxide still occupies a large share due to its excellent theoretical capacity and tap density. However, in order to meet the iterative needs of consumer-end products, the energy density and cycle life of lithium cobalt oxide positive electrode materials have ushered in higher challenges. There are two most direct ways to improve the energy density of lithium cobalt oxide: one is to increase its tap density, and the other is to increase its operating voltage.

[0003] Large-grain lithium cobalt oxide particles are typically used to achieve good tap density, but excessively large grains can affect the material's electrical performance. Therefore, in practical applications, a two-particle gradation approach, large and small, can be used to achieve better electrical performance and energy density. This approach can lead to small particle agglomeration and compaction in the finished product, affecting the material's uniformity and, in turn, impairing its electrical performance. Furthermore, the irregular size of the particles leads to large and uneven interparticle gaps, hindering further improvement in tap density.

[0004] Increasing the operating voltage of lithium cobalt oxide can further delithiate and improve its capacity. However, higher operating voltages can lead to more side reactions and irreversible phase transitions, accelerating the degradation of its electrical properties. Solid-phase doping and solid-phase coating are often used to suppress the failure of lithium cobalt oxide. For lithium cobalt oxide with a large and small particle size distribution, solid-phase coating methods are difficult to achieve uniform coating due to kinetic factors. At high voltages, defects caused by uneven material coating can accelerate side reactions and reduce its cycling performance.

[0005] Due to the above reasons, how to further improve the tap density of lithium cobalt oxide positive electrode materials, improve the dispersion of graded particles and the uniformity of coating is a technical issue that needs to be studied urgently.

[0006] Summary of the Invention

[0007] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0008] In view of the shortcomings of the prior art, the purpose of this application is to provide a multi-level structure cobalt-containing positive electrode material and its preparation method and lithium-ion battery. This application uses a sol method to perform particle grading. The organic skeleton provided by the sol precursor can hinder the migration of grain boundaries during the sintering process, effectively inhibiting the agglomeration of small particles, thereby solving the problem of uneven gradation and dispersion of large and small particles, so that the powdered active material formed after the sol precursor is heated can be evenly distributed on the surface and gaps of the cobalt-containing material A and the cobalt-containing material B. The particles with uniform gradation and dispersion can increase the tap density and compaction density, thereby increasing the capacity; at the same time, the sol method is used for coating, and the coated sol precursor and the mixed material are mixed and sintered to improve the uniformity of the coating.

[0009] To achieve this goal, this application adopts the following technical solutions:

[0010] In a first aspect, the present application provides a method for preparing a multi-level structured cobalt-containing positive electrode material, the preparation method comprising:

[0011] (1) mixing an active material raw material, a lithium source, and a chelating agent, and reacting the mixture to obtain a sol precursor;

[0012] (2) mixing the cobalt-containing material A, the cobalt-containing material B, and the sol precursor described in step (1), and heating the sol precursor until the sol precursor forms a powdered active substance, thereby obtaining a mixture of the cobalt-containing material A, the cobalt-containing material B, and the powdered active substance;

[0013] (3) The mixed material of step (2) and the coating sol precursor are mixed and sintered to obtain the multi-level structure cobalt-containing positive electrode material.

[0014] The present application provides a method for preparing a multi-level structured cobalt-containing positive electrode material, in which particle grading is performed by a sol method. The organic skeleton provided by the sol precursor can hinder the migration of grain boundaries during the sintering process, effectively inhibiting the agglomeration of small particles, thereby solving the problem of uneven gradation and dispersion of large and small particles, so that the powdered active material formed after heating the sol precursor can be evenly distributed on the surface and gaps of the cobalt-containing material A and the cobalt-containing material B. The particles with uniform gradation and dispersion can increase the tap density and compaction density, thereby increasing the capacity; at the same time, the sol method is used for coating, and the coated sol precursor and the mixed material are mixed and sintered, which can improve the uniformity of the coating.

[0015] As an optional technical solution of the present application, the active material raw material in step (1) includes at least one of cobalt salt, nickel salt, manganese salt, iron salt and phosphorus source, and can be cobalt salt.

[0016] In the present application, the active material raw material of step (1) can only select cobalt salt, which is one of the raw materials of lithium cobaltate active material. At the same time, typical but non-limiting combinations of the active material raw materials include cobalt salt, nickel salt and manganese salt combination, cobalt salt and nickel salt combination, cobalt salt and manganese salt combination, nickel salt and manganese salt combination or iron salt and phosphorus source combination, etc., wherein the combination of cobalt salt, nickel salt and manganese salt can 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 can be a mixture of cobalt salt and nickel salt, or a binary composite salt of cobalt and nickel, and the rest are similar.

[0017] In one embodiment, the cobalt salt comprises at least one of cobalt oxalate, cobalt citrate dihydrate, cobalt nitrate, cobalt sulfate and cobalt chloride.

[0018] In one embodiment, the nickel salt includes at least one of nickel nitrate, nickel sulfate, and nickel chloride.

[0019] In one embodiment, the manganese salt includes at least one of manganese nitrate, manganese sulfate, and manganese chloride.

[0020] In one embodiment, the iron salt includes at least one of ferric nitrate, ferric sulfate, and ferric chloride.

[0021] In one embodiment, the phosphorus source includes at least one of phosphoric acid, ferric phosphate, and ammonium ferric phosphate.

[0022] In one embodiment, the lithium source in step (1) includes at least one of lithium nitrate, lithium oxalate, lithium citrate and lithium chloride.

[0023] In one embodiment, the chelating agent in step (1) comprises a polyol, and the polyol comprises ethanol and / or ethylene glycol.

[0024] In one embodiment, the mixed raw materials in step (1) further include a dopant and / or a dispersant.

[0025] In one embodiment, the doping element in the dopant includes at least one of Al, Mg, Ti, Ce, Nb, Sb, Cr, F, La, W, V, Zr, Ni and Mn.

[0026] In one embodiment, when the doping element in the dopant exists as a cation, the corresponding anion includes oxalate, phosphate, acetate, nitrate, sulfate or chloride ion.

[0027] In one embodiment, the content of the doping element in the sol precursor in step (1) is 300 to 30,000 ppm, 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. However, the content is not limited to the values ​​listed above, and other values ​​not listed within the numerical range are also applicable.

[0028] In one embodiment, the dispersant includes an anionic dispersant and / or a cationic dispersant, such as polyvinyl pyrrolidone (PVP) of various polymerization degrees and / or polyoxyethylene polyoxypropylene ether (P123).

[0029] In one embodiment, the reaction temperature in step (1) is 100-150° C., for example, 100° C., 110° C., 120° C., 130° C., 140° C., or 150° C. However, this is not limited to the values ​​listed, and other values ​​not listed within this range are also applicable.

[0030] In one embodiment, the reaction time of step (1) is 1 to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours, etc. However, the reaction time is not limited to the values ​​listed above, and other values ​​not listed within the range are also applicable.

[0031] As an optional technical solution of the present application, the cobalt-containing material A in step (2) is a single crystal material.

[0032] In one embodiment, the cobalt-containing material A in step (2) includes lithium cobaltate and / or lithium nickel cobalt manganeseate.

[0033] In one embodiment, the particle size D50 of the cobalt-containing material A in step (2) is 15 to 21 μm, for example, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, or 21 μm. However, this is not limited to the values ​​listed above, and other values ​​not listed within this range are also applicable.

[0034] In one embodiment, the cobalt-containing material A in step (2) contains doping elements, and the doping elements include at least one of Al, Mg, Ce, Nb, Sb, Cr, F, La, W, V, Zr, Ni and Mn.

[0035] In one embodiment, the content of the doping element in the cobalt-containing material A in step (2) is 300 to 30,000 ppm, 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. However, the content is not limited to the values ​​listed above, and other values ​​not listed within this range are also applicable.

[0036] In one embodiment, a method for preparing the cobalt-containing material A includes mixing cobalt trioxide and lithium carbonate, sintering the mixture in steps, and then crushing and screening the mixture to obtain the cobalt-containing material A; the step-by-step sintering temperature range is 900-1200°C, for example, 900°C, 950°C, 1000°C, 1100°C, or 1200°C. Optionally, the cobalt trioxide contains a doping element.

[0037] As an optional technical solution of the present application, the cobalt-containing material B in step (2) is a single crystal material.

[0038] In one embodiment, the cobalt-containing material B in step (2) includes lithium cobaltate and / or lithium nickel cobalt manganese oxide.

[0039] In one embodiment, the particle size D50 of the cobalt-containing material B in step (2) is smaller than the particle size D50 of the cobalt-containing material A.

[0040] In one embodiment, the particle size D50 of the cobalt-containing material B in step (2) is 3 to 9 μm, for example, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, or 9 μm. However, this is not limited to the values ​​listed above, and other values ​​not listed within this range are also applicable.

[0041] In one embodiment, the cobalt-containing material B in step (2) contains doping elements, and the doping elements include at least one of Al, Mg, Ce, Nb, Sb, Cr, F, La, W, V, Zr, Ni and Mn.

[0042] In one embodiment, the content of the doping element in the cobalt-containing material B in step (2) is 300 to 30,000 ppm, 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. However, the content is not limited to the values ​​listed above, and other values ​​not listed within the numerical range are also applicable.

[0043] In the present application, the doping elements may be distributed in a gradient manner in the multi-level structured cobalt-containing positive electrode material.

[0044] In one embodiment, the method for preparing the cobalt-containing material B includes: mixing cobalt trioxide and lithium carbonate, sintering them step by step, and then crushing and screening to obtain the cobalt-containing material B; the step-by-step sintering temperature range is 800-1000°C, for example, 800°C, 850°C, 900°C, or 1000°C. Optionally, the cobalt trioxide contains a doping element.

[0045] In one embodiment, the mass ratio of the cobalt-containing material A, the cobalt-containing material B, and the solid component in the sol precursor in step (2) is 8:(0.9-1.7):(0.3-1.1), wherein the range of (0.9-1.7) for the cobalt-containing material B can be, for example, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, or 1.7, and the range of (0.3-1.1) for the solid component in the sol precursor can be, for example, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or 1.1. However, the above values ​​are not limited thereto, and other values ​​not listed within the above range are also applicable.

[0046] In the present application, if the solid component content in the sol precursor is too low, the capacity and compaction density will decrease; if the solid component content in the sol precursor is too high, the cycle performance and compaction density will decrease.

[0047] As an optional technical solution of the present application, the mixing process in step (2) is accompanied by stirring, and the stirring rate is 1000-2000 r / min, 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, etc., and the stirring time is 5-15 min, for example, 5 min, 7 min, 9 min, 10 min, 12 min or 15 min, etc. However, the above values ​​are not limited to the above values, and other values ​​not listed within the above range are also applicable.

[0048] In one embodiment, the heating temperature in step (2) is 100-150° C., for example, 100° C., 110° C., 120° C., 130° C., 140° C., or 150° C. However, this is not limited to the listed values, and other values ​​not listed within this range are also applicable.

[0049] In one embodiment, the heating time in step (2) is 1 to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours, etc. However, this is not limited to the listed values, and other values ​​not listed within this numerical range are also applicable.

[0050] In one embodiment, the powdered active material in step (2) includes any one of lithium cobalt oxide, lithium iron phosphate or lithium nickel cobalt manganese oxide, and lithium cobalt oxide can be selected.

[0051] In one embodiment, the particle size D50 of the powdered active substance in step (2) is smaller than the particle size D50 of the cobalt-containing material B.

[0052] In one embodiment, the particle size D50 of the powdered active substance in step (2) is 0.01 to 1.99 μm, 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, etc. However, this is not limited to the values ​​listed above, and other values ​​not listed within this range are also applicable.

[0053] In the present application, if the particle size D50 of the powdered active material is too small, the cycle performance and the compaction density will be reduced; if the particle size D50 of the powdered active material is too large, the cycle performance and the compaction density will be reduced.

[0054] As an optional technical solution of the present application, the method for preparing the coating sol precursor in step (3) includes: mixing a compound containing a coating element and a chelating agent, and reacting to obtain the coating sol precursor;

[0055] In one embodiment, the coating element includes at least one of Ti, Zr, Y, Ce, Nb, Sb, Cr, F, La, W and V elements.

[0056] In one embodiment, the compound containing the coating element may be a salt containing the coating element, or an oxide containing the coating element.

[0057] In one embodiment, when the coating element in the salt containing the coating element exists as a cation, the corresponding anion includes oxalate, phosphate, acetate, nitrate, sulfate or chloride, etc.

[0058] In one embodiment, in the method for preparing a coating sol precursor, the chelating agent includes a polyol, and the polyol includes ethanol and / or ethylene glycol.

[0059] In one embodiment, in the method for preparing a coating sol precursor, the reaction temperature is 100-150° C., for example, 100° C., 110° C., 120° C., 130° C., 140° C., or 150° C., and the reaction time is 1-3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours. However, these values ​​are not limited to the values ​​listed, and other values ​​not listed within this numerical range are also applicable.

[0060] In one embodiment, the mass ratio of the mixed material to the coating sol precursor in step (3) is (7-27):3, for example, 7:3, 9:3, 10:3, 12:3, 15:3, 17:3, 20:3, 25:3 or 27:3, etc. However, the above values ​​are not limited thereto, and other values ​​not listed within the above range are also applicable.

[0061] As an optional technical solution of the present application, the mixing process in step (3) is accompanied by stirring, and the stirring rate is 600-1000 r / min, for example, 600 r / min, 700 r / min, 800 r / min, 800 r / min or 1000 r / min, and the stirring time is 20-40 min, for example, 20 min, 25 min, 30 min, 35 min or 40 min, etc. However, the values ​​listed are not limited to the values ​​listed, and other values ​​not listed within the numerical range are also applicable.

[0062] In one embodiment, the sintering temperature in step (3) is 600-800° C., for example, 600° C., 620° C., 650° C., 670° C., 700° C., 720° C., 750° C., 770° C., or 800° C. However, the temperature is not limited to the values ​​listed, and other values ​​not listed within the numerical range are also applicable.

[0063] In one embodiment, the sintering time in step (3) is 8 to 12 hours, for example, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours, etc. However, this is not limited to the listed values, and other values ​​not listed within this range are also applicable.

[0064] Optionally, the sintering atmosphere in step (3) is an air atmosphere or a mixed atmosphere of air and inert gas.

[0065] In a second aspect, the present application provides a multi-level structure cobalt-containing positive electrode material, which is prepared by the preparation method described in the first aspect.

[0066] As an optional technical solution of the present application, the multi-level structure cobalt-containing positive electrode material includes cobalt-containing material A1, cobalt-containing material B1 and active material.

[0067] The cobalt-containing material A1, the cobalt-containing material B1 and the active material independently include a matrix and an oxide coating layer coated on the surface of the matrix; the active material is uniformly distributed on the surface and gaps of the cobalt-containing material A1 and the cobalt-containing material B1.

[0068] In the present application, the cobalt-containing material A1, the cobalt-containing material B1 and the active material independently include a matrix and an oxide coating layer coated on the surface of the matrix, specifically referring to: the cobalt-containing material A1 includes a cobalt-containing material A matrix and an oxide coating layer coated on the surface of the matrix, the cobalt-containing material B1 includes a cobalt-containing material B matrix and an oxide coating layer coated on the surface of the matrix, and the active material includes a powdered active material matrix and an oxide coating layer coated on the surface of the matrix; the cobalt-containing material A1, the cobalt-containing material B1 and the oxide coating layer of the active material have the same material type and proportion content, and the coating element in the oxide coating layer includes at least one of Ti, Zr, Y, Ce, Nb, Sb, Cr, F, La, W and V elements.

[0069] In one embodiment, the particle size of the cobalt-containing material A1 is 15 to 21 μm, for example, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, or 21 μm, etc. However, the particle size is not limited to the values ​​listed above, and other values ​​not listed within the range are also applicable.

[0070] In one embodiment, the particle size of the cobalt-containing material B1 is 3 to 9 μm, for example, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, or 9 μm, etc. However, the particle size is not limited to the values ​​listed above, and other values ​​not listed within the range are also applicable.

[0071] In one embodiment, the particle size of the active material is 0.01 to 1.99 μm, 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, etc. However, the particle size is not limited to the values ​​listed above, and other values ​​not listed within the range are also applicable.

[0072] In one embodiment, based on the total mass of the multi-level structure cobalt-containing positive electrode material being 100%, the mass content of the cobalt-containing material A1 is 50% to 90%. For example, the mass content may be 50%, 60%, 70%, 80%, or 90%, but is not limited to the values ​​listed above. Other values ​​not listed within this range are also applicable.

[0073] In one embodiment, based on the total mass of the multi-level structure cobalt-containing positive electrode material being 100%, the mass content of the cobalt-containing material B1 is 10-30%. For example, the mass content may be 10%, 12%, 15%, 17%, 20%, 25%, 27%, or 30%, etc., but is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable.

[0074] In one embodiment, based on the total mass of the multi-level structure cobalt-containing positive electrode material being 100%, the mass content of the active material is 5-20%. For example, the mass content may be 5%, 7%, 10%, 12%, 15%, 17%, or 20%, but is not limited to the values ​​listed above. Other values ​​not listed within this range are also applicable.

[0075] In one embodiment, the cobalt-containing material A1, the cobalt-containing material B1 and the active material independently include doping elements.

[0076] In the present application, the cobalt-containing material A1 has the same doping element as the cobalt-containing material A, the cobalt-containing material B1 has the same doping element as the cobalt-containing material B, and the active material has the same doping element as the powdered active substance.

[0077] In a third aspect, the present application provides a lithium-ion battery, wherein the positive electrode of the lithium-ion battery comprises the multi-level structure cobalt-containing positive electrode material described in the second aspect.

[0078] The numerical range described in this application includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0079] Compared with the prior art, the present invention has the following advantages:

[0080] (1) The present application provides a method for preparing a multi-level structure cobalt-containing positive electrode material, wherein the particle grading is performed by a sol method, and the organic skeleton provided by the sol precursor can hinder the migration of grain boundaries during the sintering process, effectively inhibiting the agglomeration of small particles, thereby solving the problem of uneven gradation and dispersion of large and small particles, so that the powdered active material formed after the sol precursor is heated can be evenly distributed on the surface and gaps of the cobalt-containing material A and the cobalt-containing material B. The particles with uniform gradation and dispersion can increase the tap density and increase the capacity; at the same time, the sol method is used for coating, and the coated sol precursor and the mixed material are mixed and sintered, which can improve the uniformity of the coating;

[0081] (2) The multi-level structure cobalt-containing positive electrode material prepared by the method of the present application has a high compaction density, good crystallinity and uniformity of the material, and excellent capacity and cycle performance at high voltage.

[0082] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0083] The technical solution of this application is further explained below through specific implementation methods.

[0084] Example 1

[0085] This embodiment provides a method for preparing a multi-level structure cobalt-containing positive electrode material, which specifically includes:

[0086] (1) 600 g of Co3O4 and 290 g of lithium carbonate were taken, wherein the Co3O4 was doped with 9000 ppm of Al and 1000 ppm of Mg, and had a particle size of D50 = 17 μm. The mixture was mixed in a mixer at 800 r / min for 30 min 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, kept warm for 120 min, and then heated to 1060°C at a heating rate of 4°C / min, kept warm for 10 h, and then cooled naturally. The mixture was then crushed by a jaw crusher, a roller mill, and a jet mill, and finally passed through a 200 mesh sieve to obtain single crystal large particles with a particle size of D50 = 18 μm, i.e., micron-sized large particles of lithium cobalt oxide A.

[0087] (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 had a particle size of D50 = 4 μm. The mixture was mixed in a mixer at 800 r / min for 30 min 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, kept warm for 120 min, and then heated to 1060°C at a heating rate of 4°C / min, kept warm for 10 h, and then cooled naturally with a ventilation rate of 30 L / min. The mixture was then crushed by a jaw crusher, a roller mill, and a jet mill, and finally passed through a 200 mesh sieve to obtain single crystal small particles with a particle size of D50 = 6 μm, i.e., micron-sized small particles of lithium cobalt oxide B.

[0088] (3) Cobalt oxalate and lithium nitrate were added according to a Li / Co ratio of 1.05, a chelating agent (i.e., ethanol) was added, and a dopant was added and stirred to form a suspension. The dopant was a mixture of aluminum nitrate, magnesium nitrate, and titanium nitrate, so that the Al content was 10,000 ppm, the Mg content was 2,000 ppm, and the Ti content was 2,000 ppm. The suspension was heated to 120 degrees Celsius under the condition of an external condensation reflux device for 2 hours. The solid was completely reacted and dissolved, and the solution was clarified to form a highly cross-linked sol precursor Cp1.

[0089] (4) Lithium cobalt oxide A and lithium cobalt oxide B were added to the sol precursor Cp1 in a stoichiometric ratio of 8:1.5:0.5 based on the mass ratio of the solid components of A, B, and Cp1. The mixture was stirred at 1500 r / min for 10 min to fully disperse the particles of A and B in the sol precursor. The mixture was heated at 200°C for 2 h until the sol precursor Cp1 formed a powder Cp2 and was fully dispersed on the surface and gaps of the semi-finished products A and B. The particle size D50 of Cp2 was 0.5±0.4 μm. The mixture of A, B, and Cp2 was the di-sintered precursor D.

[0090] (5) A salt containing a coating element and a chelating agent (i.e., ethanol) are stirred and mixed to form a suspension, wherein the salt containing the coating element is a mixture of titanium nitrate, zirconium nitrate, and yttrium nitrate, so that the Ti element content is 500 ppm, the Zr element content is 300 ppm, and the Y element content is 500 ppm; the suspension is heated to 120 degrees Celsius under the condition of an external condensation reflux device and reacted for 2 hours, and the solid is completely reacted and dissolved, and the solution is clarified to form a highly cross-linked coating sol precursor P;

[0091] (6) adding the coated sol precursor P to the calcined precursor D, mixing in a mixer at 800 r / min for 30 min to obtain a uniform mixture, heating the mixture to 700°C at a heating rate of 4°C / min in an air atmosphere and maintaining the temperature for 3 h, and then crushing and sieving the mixture in sequence to obtain the multi-level structure cobalt-containing positive electrode material;

[0092] The multi-level structure cobalt-containing positive electrode material is a mixed graded material of cobalt-containing material A1, cobalt-containing material B1 and active material Cp3, wherein the cobalt-containing material A1 includes a lithium cobaltate A matrix and an oxide coating layer coated on the surface of the matrix, and its particle size D50 is 18.5 μm; the cobalt-containing material B1 includes a lithium cobaltate B matrix and an oxide coating layer coated on the surface of the matrix, and its particle size D50 is 6.5 μm; the active material Cp3 includes a lithium cobaltate matrix (corresponding to the powder Cp2) and an oxide coating layer coated on the surface of the matrix; the active material Cp3 is uniformly distributed on the surface and gaps of the cobalt-containing material A1 and the cobalt-containing material B1; the overall particle size D50 of the multi-level structure cobalt-containing positive electrode material is 15.5 μm; based on the total mass of the multi-level structure cobalt-containing positive electrode material as 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.

[0093] Example 2

[0094] This embodiment provides a method for preparing a multi-level structure cobalt-containing positive electrode material, which specifically includes:

[0095] (1) Using the same method as in Example 1, micron-sized large-particle lithium cobalt oxide A was prepared;

[0096] (2) Using the same method as in Example 1, micron-sized particles of lithium cobalt oxide B were prepared;

[0097] (3) Cobalt acetate and lithium nitrate were added according to a Li / Co ratio of 1.05, a chelating agent (i.e., ethanol) was added, and a dopant was added and stirred to form a suspension. The dopant was a mixture of zirconium nitrate, nickel nitrate, and manganese nitrate, such that the Zr content was 1000 ppm, the Ni content was 2000 ppm, and the Mn content was 2000 ppm. The suspension was heated to 120 degrees Celsius under the condition of an external condensation reflux device for 2 hours. The solid was completely reacted and dissolved, and the solution was clarified to form a highly cross-linked sol precursor Cp1.

[0098] (4) Lithium cobalt oxide A and lithium cobalt oxide B were added to the sol precursor Cp1 in a stoichiometric ratio of 8:1.5:0.5 based on the mass ratio of the solid components of A, B, and Cp1. The mixture was stirred at 1500 r / min for 10 min to fully disperse the particles of A and B in the sol precursor. The mixture was heated at 200°C for 2 h until the sol precursor Cp1 formed a powder Cp2 and was fully dispersed on the surface and gaps of the semi-finished products A and B. The mixture of A, B, and Cp2 was the sintered precursor D.

[0099] (5) A salt containing a coating element and a chelating agent (i.e., ethanol) are stirred and mixed to form a suspension, wherein the salt containing the coating element is a mixture of nickel nitrate, manganese nitrate, magnesium nitrate, zirconium nitrate, aluminum nitrate, and titanium nitrate, so that the Ni element content is 500 ppm, the Mn element content is 800 ppm, the Mg element content is 300 ppm, the Zr element content is 700 ppm, the Al element content is 500 ppm, and the Ti element content is 400 ppm; the suspension is heated to 120 degrees Celsius under the condition of an external condensation reflux device for reaction for 2 hours, and the solid is completely reacted and dissolved, and the solution is clarified to form a highly cross-linked coating sol precursor P;

[0100] (6) adding the coated sol precursor P to the calcined precursor D, mixing in a mixer at 800 r / min for 30 min to obtain a uniform mixture, heating the mixture to 700°C at a heating rate of 4°C / min in an air atmosphere and keeping the temperature for 10 h, and then crushing and sieving the mixture in sequence to obtain the multi-level structure cobalt-containing positive electrode material;

[0101] The multi-level structure cobalt-containing positive electrode material is a mixed graded material of cobalt-containing material A1, cobalt-containing material B1 and active material Cp3, wherein the cobalt-containing material A1 includes a lithium cobaltate A matrix and an oxide coating layer coated on the surface of the matrix; the cobalt-containing material B1 includes a lithium cobaltate B matrix and an oxide coating layer coated on the surface of the matrix; the active material Cp3 includes a lithium cobaltate matrix (corresponding to the powder Cp2) and an oxide coating layer coated on the surface of the matrix; the active material Cp3 is uniformly distributed on the surface and gaps of the cobalt-containing material A1 and the cobalt-containing material B1; the overall particle size D50 of the multi-level structure cobalt-containing positive electrode material is 15.5 μm; based on the total mass of the multi-level structure cobalt-containing positive electrode material as 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.

[0102] Example 3

[0103] This embodiment provides a method for preparing a multi-level structure cobalt-containing positive electrode material, which specifically includes:

[0104] (1) Using the same method as in Example 1, micron-sized large-particle lithium cobalt oxide A was prepared;

[0105] (2) Using the same method as in Example 1, micron-sized particles of lithium cobalt oxide B were prepared;

[0106] (3) adding nickel nitrate, cobalt nitrate, manganese nitrate and lithium nitrate in a ratio of 5:2:3, adding a chelating agent (i.e., ethanol), and adding a dopant and stirring to form a suspension, wherein the dopant is a mixture of titanium nitrate, magnesium nitrate and zirconium nitrate, so that the Ti element content is 600 ppm, the Zr element content is 400 ppm, and the Mg element content is 800 ppm; heating the suspension to 120 degrees Celsius under the condition of an external condensation reflux device for 2 hours, and the solid is completely reacted and dissolved, and the solution is clarified to form a highly cross-linked sol precursor Cp1;

[0107] (4) A salt containing a coating element and a chelating agent (i.e., ethanol) are stirred and mixed to form a suspension, wherein the salt containing the coating element is a mixture of titanium nitrate, zirconium nitrate, and yttrium nitrate, such that the Ti content is 500 ppm, the Zr content is 300 ppm, and the Y content is 500 ppm; the suspension is heated to 120 degrees Celsius under the condition of an external condensation reflux device and reacted for 2 hours, and the solid is completely reacted and dissolved, and the solution is clarified to form a highly cross-linked coating sol precursor P;

[0108] (5) Lithium cobalt oxide A and lithium cobalt oxide B were added to the sol precursor Cp1 in a stoichiometric ratio of 8:1.5:0.5 based on the mass ratio of the solid components of A, B, and Cp1. The mixture was stirred at 1500 r / min for 10 min to fully disperse the particles of A and B in the sol precursor. The mixture was heated at 120°C for 2 h until the sol precursor Cp1 formed a powder Cp2 and was fully dispersed on the surface and gaps of the semi-finished products A and B. The mixture of A, B, and Cp2 was the sintered precursor D.

[0109] (6) adding the coated sol precursor P to the calcined precursor D, mixing in a mixer at 800 r / min for 30 min to obtain a uniform mixture, heating the mixture to 900°C at a heating rate of 4°C / min in an air atmosphere and maintaining the temperature for 10 h, and then crushing and sieving the mixture in sequence to obtain the multi-level structure cobalt-containing positive electrode material;

[0110] The multi-level structure cobalt-containing positive electrode material is a mixed graded material of cobalt-containing material A1, cobalt-containing material B1 and active material Cp3, wherein the cobalt-containing material A1 includes a lithium cobaltate A matrix and an oxide coating layer coated on the surface of the matrix; the cobalt-containing material B1 includes a lithium cobaltate B matrix and an oxide coating layer coated on the surface of the matrix; the active material Cp3 includes a lithium nickel cobalt manganese oxide matrix (corresponding to the powder Cp2) and an oxide coating layer coated on the surface of the matrix; the active material Cp3 is uniformly distributed on the surface and gaps of the cobalt-containing material A1 and the cobalt-containing material B1; the overall particle size D50 of the multi-level structure cobalt-containing positive electrode material is 15.0 μm; based on the total mass of the multi-level structure cobalt-containing positive electrode material as 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.

[0111] Example 4

[0112] The only difference between this embodiment and embodiment 1 is that in step (4), the mass ratio of the solid components in A, B and Cp1 is adjusted to 8:1.8:0.2.

[0113] Example 5

[0114] The only difference between this embodiment and embodiment 1 is that in step (4), the mass ratio of the solid components in A, B and Cp1 is adjusted to 8:0.8:1.2.

[0115] Example 6

[0116] The only difference between this embodiment and embodiment 1 is that the particle size D50 of the powdered material Cp2 is adjusted to 0.1 μm.

[0117] Example 7

[0118] The only difference between this embodiment and embodiment 1 is that the particle size D50 of the powdered material Cp2 is adjusted to 5 μm.

[0119] Comparative Example 1

[0120] The only difference between this comparative example and Example 1 is that in step (4), lithium cobalt oxide A and lithium cobalt oxide B are not added to the sol precursor Cp1, but are directly heated to form a powder Cp2 from the sol precursor Cp1, and then the temperature is raised to 1000°C at a heating rate of 4°C / min and kept for 10 hours, and then naturally cooled with a ventilation volume of 30 L / min to obtain single-crystalline small particles of lithium cobalt oxide C with a particle size D50 = 0.5 μm; lithium cobalt oxides A, B and C are mixed at 800 r / min for 30 minutes, and the three are fully mixed according to the cobalt content ratio of A, B and C being 8:1.5:0.5 to obtain a di-sintered precursor.

[0121] Comparative Example 2

[0122] The only difference between this comparative example and Example 1 is that steps (3) and (4) are replaced by "mixing lithium cobalt oxide A and lithium cobalt oxide B at 800 r / min for 30 min, with a metering ratio of 8:2 based on the cobalt content ratio of A and B respectively, so that the A and B particles are fully mixed to obtain a di-sintered precursor D".

[0123] Comparative Example 3

[0124] The only difference between this comparative example and comparative example 1 is that in step (4), lithium cobalt oxide B is omitted, and lithium cobalt oxide A and lithium cobalt oxide C are fully mixed according to the cobalt content ratio of each of lithium cobalt oxide A and lithium cobalt oxide C being 8:2 to obtain a di-sintered precursor.

[0125] Comparative Example 4

[0126] The only difference between this comparative example and comparative example 1 is that in step (4), lithium cobalt oxide A is omitted, and lithium cobalt oxide B and lithium cobalt oxide C are fully mixed according to the cobalt content ratio of each of lithium cobalt oxide B and lithium cobalt oxide C being 8:2 to obtain a di-sintered precursor.

[0127] Performance Testing

[0128] The cobalt-containing positive electrode materials provided in Examples 1-7 and Comparative Examples 1-4 were dissolved in N-methylpyrrolidone with Super P and PVDF at a mass ratio of 95:5:5, coated, and dried to obtain a positive electrode sheet; the positive electrode sheet, separator, and negative lithium sheet were assembled into a lithium-ion battery, in which the electrolyte was 1M LiPF6DMC+EMC+EC.

[0129] (1) Compaction density test: The powder was tested using a PRCD3100 compaction powder resistance meter developed by Yuanneng Technology. The test parameters were as follows: the upper indenter applied pressures of 10-200 MPa to the powder in sequence, with intervals of 20 MPa, and maintained at this pressure for 10 seconds. The compaction density result was calculated by reading the value at a pressure of 150 MPa.

[0130] (2) Capacity test: 3.0V-4.55V, 0.2C / 0.2C charge and discharge, record the battery's first discharge capacity.

[0131] (3) Cyclic test: at 45°C, 3.0-4.59V, 1C / 1C charge and discharge, 30 cycles, and record the capacity retention rate.

[0132] The test results are shown in Table 1.

[0133] Table 1

[0134] analyze:

[0135] As can be seen from the data results of Examples 1-3, the present application uses a sol-gel method for particle grading. The organic framework provided by the sol precursor can hinder the migration of grain boundaries during the sintering process, effectively inhibiting the agglomeration of small particles, thereby solving the problem of uneven dispersion of large and small particle gradations. At the same time, the use of a sol-gel method for coating can improve the uniformity of the coating. The multi-level structure cobalt-containing positive electrode material prepared by the method of the present application has a high compaction density, good crystallinity and uniformity of the material, and excellent capacity and cycle performance at high voltage.

[0136] It can be seen from the data results of Example 1 and Examples 4-5 that if the content of solid components in Cp1 is too low, the capacity will be reduced and the compaction density will be reduced; if the content of solid components in Cp1 is too high, the cycle performance will be reduced and the compaction density will be reduced.

[0137] It can be seen from the data results of Examples 1 and 5-6 that if the particle size D50 of the pulverized material Cp2 is too small, the cycle performance and compaction density will decrease; if the particle size D50 of the pulverized material Cp2 is too large, the cycle performance and compaction density will decrease.

[0138] The data results of Example 1 and Comparative Examples 1-4 show that using conventional mechanical mixing methods for grading will result in a decrease in particle capacity cycle, and using only two positive electrode materials for grading will result in a decrease in particle compaction density.

[0139] The applicant declares that the above is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Technical personnel in the relevant technical field should understand that any changes or substitutions that can be easily thought of by technical personnel in the relevant technical field within the technical scope disclosed in this application fall within the protection scope and disclosure scope of this application.

Claims

1. A method for preparing a multi-level structured cobalt-containing positive electrode material, comprising: (1) mixing an active material raw material, a lithium source and a chelating agent, and reacting them to obtain a sol precursor; (2) mixing the cobalt-containing material A, the cobalt-containing material B and the sol precursor described in step (1), and heating the sol precursor until the sol precursor forms a powdered active substance, thereby obtaining a mixture of the cobalt-containing material A, the cobalt-containing material B and the powdered active substance; (3) The mixed material of step (2) and the coating sol precursor are mixed and sintered to obtain the multi-level structure cobalt-containing positive electrode material.

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

3. The preparation method according to claim 1 or 2, wherein The cobalt-containing material A in step (2) is a single crystal material; Optionally, the cobalt-containing material A in step (2) includes lithium cobalt oxide and / or lithium nickel cobalt manganese oxide; Optionally, the particle size D50 of the cobalt-containing material A in step (2) is 15 to 21 μm; Optionally, the cobalt-containing material A 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; Optionally, the content of doping elements in the cobalt-containing material A in step (2) is 300 to 30,000 ppm.

4. The preparation method according to any one of claims 1 to 3, wherein: The cobalt-containing material B in step (2) is a single crystal material; Optionally, the cobalt-containing material B in step (2) includes lithium cobalt oxide and / or lithium nickel cobalt manganese oxide; Optionally, in step (2), the particle size D50 of the cobalt-containing material B is smaller than the particle size D50 of the cobalt-containing material A; Optionally, the particle size D50 of the cobalt-containing material B in step (2) is 3 to 9 μm; Optionally, the cobalt-containing material B 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; Optionally, the content of the doping element in the cobalt-containing material B in step (2) is 300 to 30000 ppm; Optionally, in step (2), the mass ratio of the cobalt-containing material A, the cobalt-containing material B and the solid component in the sol precursor is 8:(0.9-1.7):(0.3-1.1).

5. The preparation method according to any one of claims 1 to 4, wherein: The mixing process in step (2) is accompanied by stirring, the stirring rate is 1000-2000 r / min, and the stirring time is 5-15 min; Optionally, the heating temperature in step (2) is 100-150° C.; Optionally, the heating time in step (2) is 1 to 3 hours; Optionally, the powdered active material in step (2) includes any one of lithium cobalt oxide, lithium iron phosphate or lithium nickel cobalt manganese oxide; Optionally, the particle size D50 of the powdered active substance in step (2) is smaller than the particle size D50 of the cobalt-containing material B; Optionally, the particle size D50 of the powdered active substance in step (2) is 0.01 to 1.99 μm.

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

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

3.

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

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

10. The multi-level structure cobalt-containing positive electrode material according to claim 9, wherein: The multi-level structure cobalt-containing positive electrode material comprises a cobalt-containing material A1, a cobalt-containing material B1 and an active material; The cobalt-containing material A1, the cobalt-containing material B1 and the active material independently include a matrix and a The active material is evenly distributed on the surface and gaps of the cobalt-containing material A1 and the cobalt-containing material B1; Optionally, the particle size of the cobalt-containing material A1 is 15 to 21 μm; Optionally, the particle size of the cobalt-containing material B1 is 3 to 9 μm; Optionally, the particle size of the active material is 0.01 to 1.99 μm; Optionally, based on the total mass of the multi-level structure cobalt-containing positive electrode material being 100%, the mass content of the cobalt-containing material A1 is 50-90%; Optionally, based on the total mass of the multi-level structure cobalt-containing positive electrode material being 100%, the mass content of the cobalt-containing material B1 is 10-30%; Optionally, based on the total mass of the multi-level structure cobalt-containing positive electrode material being 100%, the mass content of the active material is 5 to 20%; Optionally, the cobalt-containing material A1, the cobalt-containing material B1 and the active material independently include doping elements.

11. A lithium ion battery comprising the multi-level structure cobalt-containing positive electrode material according to claim 9 or 10.

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