Preparation method and application of nickel-manganese-magnesium-aluminum co-doped lithium cobalt oxide positive electrode material

Abstract

The present application relates to a kind of preparation method of nickel-manganese-magnesium-aluminum co-doped lithium cobaltate anode material and its application.The preparation method includes the following steps: under certain atmosphere, the cobalt salt solution, precipitant solution, aluminum salt, nickel salt, magnesium salt and manganese salt are added to complexing agent solution to carry out first mixing to obtain first mixed solution, after 45-55% of the precipitate in the first mixed solution is removed, second mixing is carried out to obtain second mixed solution, after 10-100% of the precipitate removed is added in the second mixed solution, third mixing is carried out to obtain third mixture with median particle size of 15-17 μm, and washing and drying are carried out to obtain nickel-manganese-magnesium-aluminum high-doped cobalt carbonate;After the nickel-manganese-magnesium-aluminum high-doped cobalt carbonate, lithium source and dopant are fourth mixed, sintering is carried out to obtain lithium cobaltate matrix;The lithium cobaltate matrix is coated to obtain lithium cobaltate anode material.The present application improves the structural stability and cycle stability of lithium cobaltate under high-voltage system.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, and in particular to a method for preparing a nickel-manganese-magnesium-aluminum co-doped lithium cobalt oxide cathode material and its application. Background Technology

[0002] Among the currently commercially available lithium-ion battery cathode materials, lithium cobalt oxide (LiCoO2) is widely used in digital products such as smartphones and laptops due to its relatively stable electrochemical performance, high operating voltage, high energy density, and long lifespan. This places increasingly higher demands on the energy density and other performance characteristics of lithium-ion batteries.

[0003] Doping and coating can effectively improve the structural stability, cycle life, and safety of the resulting lithium cobalt oxide cathode material under high voltage. Conventional doping involves solid-phase mixing of metal compounds, cobalt source, and lithium source, but it is difficult to achieve uniform mixing. Furthermore, metal element segregation can easily lead to the appearance of impurity phases, ultimately resulting in the inability to achieve homogeneous doping in the product.

[0004] CN113247964A discloses a method for preparing high-rate, high-compact, and high-voltage lithium cobalt oxide cathode material. The prepared cathode material has a particle size D50 of 6.0~11.0µm and a compaction density of 3.7~3.95g / cm³. 3 The small-sized lithium cobalt oxide particles have a narrow particle size distribution, resulting in a relatively low compaction density.

[0005] CN111769275A discloses a doped high-voltage lithium cobalt oxide cathode material and its preparation method. In the preparation process, Zn, Y, Tb and Pr are doped into the cathode material, which can effectively improve the structural stability, cycle life and safety of the cathode material under high voltage. However, the uniformity of solid phase doping is poor, which will affect the capacity and cycle life of the material.

[0006] CN103390748A discloses a method for preparing alumina-coated lithium cobalt oxide cathode material. The method involves ball milling to directly and uniformly disperse a solid aluminum-containing compound onto the surface of lithium cobalt oxide. The raw material composition and product formulation are easily controlled, making it suitable for large-scale production. Furthermore, the modified lithium cobalt oxide cathode material exhibits high specific capacity and excellent cycle performance. Coating reduces direct contact between lithium cobalt oxide and the electrolyte, improving cycle stability. While simple Al coating can appropriately improve cycle performance, it reduces capacity and the material's conductivity.

[0007] Therefore, how to further improve the structural stability and cycle stability of lithium cobalt oxide under high voltage systems is an important research direction in this field. Summary of the Invention

[0008] The purpose of this invention is to provide a lithium cobalt oxide cathode material for use at a high voltage of 4.5V. By designing with Ni / Mn element doping, the specific capacity of the material can be effectively improved while ensuring cycle performance. By co-doping with Mg and Al elements, the balance between specific capacity loss and cycle performance under high doping can be effectively achieved.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] One objective of this invention is to provide a method for preparing a nickel-manganese-magnesium-aluminum co-doped lithium cobalt oxide cathode material, the method comprising the following steps:

[0011] (1) Under a certain atmosphere, a first mixture is obtained by adding cobalt salt solution, precipitant solution, aluminum salt, nickel salt, magnesium salt and manganese salt to complexing agent solution. After removing 45~55% of the precipitate in the first mixture, a second mixture is obtained. After adding 10~100% of the removed precipitate to the second mixture, a third mixture is obtained to obtain a third mixture with a median particle size of 15~17µm. After washing and drying, NiMnMgAl highly doped cobalt carbonate is obtained.

[0012] (2) After mixing the NiMnMgAl highly doped cobalt carbonate, lithium source and dopant in step (1) for the fourth time, sinter to obtain lithium cobalt oxide matrix;

[0013] (3) Coating the lithium cobalt oxide matrix described in step (2) yields a lithium cobalt oxide cathode material.

[0014] This invention prepares a cobalt carbonate matrix with a wide particle size range by modifying the precursor in step (1). Step (2) involves doping during the precursor preparation process to make the doping more uniform. This doping method substitutes the lithium sites of lithium cobalt oxide with dopant elements, thereby alleviating the electrostatic interaction and cobalt dissolution caused by lithium extraction under high voltage, improving the structure and cycle stability of the material, and giving the material high capacity and good cycle stability under high voltage. The coating in step (3) further improves the conductivity of the material. The entire preparation method is simple, does not require high-end production equipment, and is easy to operate. These factors are conducive to the industrialization of the material.

[0015] In step (1), the mass fraction of the precipitate in the first mixture can be 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, or 55%, etc.; the fraction of the precipitate added to the second mixture can be 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%, etc.; and the median particle size in the third mixture can be 15µm, 15.2µm, 15.4µm, 15.6µm, 15.8µm, 16µm, 16.2µm, 16.4µm, 16.6µm, 16.8µm, or 17µm, etc., but is not limited to the listed values. Other unlisted values ​​within the above ranges are also applicable.

[0016] As a preferred technical solution of the present invention, the co-current volume ratio of the cobalt salt solution and the precipitant solution in step (1) is 1:(1.0~1.5), wherein the volume ratio can be 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4 or 1:1.5, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0017] Preferably, the flow rate of the cobalt salt solution is 0.2~3 mL / min, wherein the flow rate can be 0.2 mL / min, 0.4 mL / min, 0.6 mL / min, 0.8 mL / min, 1.0 mL / min, 1.2 mL / min, 1.4 mL / min, 1.6 mL / min, 1.8 mL / min, 2.0 mL / min, 2.2 mL / min, 2.4 mL / min, 2.6 mL / min, 2.8 mL / min or 3 mL / min, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0018] Preferably, the cobalt salt solution includes any one or a combination of at least two of cobalt sulfate solution, cobalt chloride solution, cobalt nitrate solution, or cobalt acetate solution, wherein typical but non-limiting examples of the combination include: a combination of cobalt sulfate solution and cobalt chloride solution, a combination of cobalt chloride solution and cobalt nitrate solution, or a combination of cobalt nitrate solution and cobalt acetate solution, etc.

[0019] Preferably, the concentration of the precipitant in the precipitant solution is 1~3 mol / L, wherein the concentration can be 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, 2.0 mol / L, 2.2 mol / L, 2.4 mol / L, 2.6 mol / L, 2.8 mol / L or 3 mol / L, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0020] Preferably, the precipitant comprises any one or a combination of at least two of ammonia, alkali metal carbonate, alkali metal bicarbonate or alkaline earth metal bicarbonate, wherein typical but non-limiting examples of the combination include: a combination of ammonia and alkali metal carbonate, a combination of alkali metal carbonate and alkali metal bicarbonate, or a combination of alkali metal bicarbonate and alkaline earth metal bicarbonate, etc.

[0021] Preferably, the alkali metal carbonate includes sodium carbonate and / or potassium carbonate.

[0022] Preferably, the alkali metal bicarbonate includes sodium bicarbonate and / or potassium bicarbonate.

[0023] Preferably, the alkaline earth metal bicarbonate includes barium bicarbonate and / or calcium bicarbonate.

[0024] Preferably, the concentration of the aluminum salt in the first mixture is 0.1~1 mol / L, wherein the concentration can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L or 1 mol / L, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0025] Preferably, the aluminum salt includes any one or a combination of at least two of aluminum chloride, aluminum sulfate, or sodium aluminate, wherein typical but non-limiting examples of the combination include: a combination of aluminum chloride and aluminum sulfate, a combination of aluminum sulfate and sodium aluminate, or a combination of aluminum chloride and sodium aluminate, etc.

[0026] Preferably, the concentration of the magnesium salt in the first mixture is 0.1~1 mol / L, wherein the concentration can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L or 1 mol / L, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0027] Preferably, the magnesium salt comprises any one or a combination of at least two of magnesium chloride, magnesium sulfate, or magnesium nitrate, wherein typical but non-limiting examples of such combinations include combinations of magnesium chloride and magnesium sulfate, combinations of magnesium sulfate and magnesium nitrate, or combinations of magnesium chloride and magnesium nitrate, etc.

[0028] Preferably, the concentration of the nickel salt in the first mixture is 0.1~1 mol / L, wherein the concentration can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L or 1 mol / L, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0029] Preferably, the nickel salt comprises any one or a combination of at least two of nickel sulfate, nickel nitrate, nickel chloride, or nickel acetate, wherein typical but non-limiting examples of the combination include: a combination of nickel sulfate and nickel nitrate, a combination of nickel nitrate and nickel chloride, a combination of nickel chloride and nickel acetate, or a combination of nickel sulfate and nickel acetate, etc.

[0030] Preferably, the concentration of the manganese salt in the first mixture is 0.1~1 mol / L, wherein the concentration can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L or 1 mol / L, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0031] Preferably, the manganese salt includes any one or a combination of at least two of manganese chloride, manganese sulfate, or manganese nitrate, wherein typical but non-limiting examples of the combination include a combination of manganese chloride and manganese sulfate, a combination of manganese sulfate and manganese nitrate, or a combination of manganese chloride and manganese nitrate, etc.

[0032] As a preferred technical solution of the present invention, the certain atmosphere in step (1) includes a nitrogen atmosphere.

[0033] Preferably, in step (1), the temperature of the first mixture is 40~80℃, wherein the temperature can be 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃ or 80℃, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] Preferably, the stirring speed of the first mixing in step (1) is 200~700 r / min, wherein the stirring speed can be 200 r / min, 250 r / min, 300 r / min, 350 r / min, 400 r / min, 450 r / min, 500 r / min, 550 r / min, 600 r / min, 650 r / min or 700 r / min, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0035] Preferably, the pH of the first mixture in step (1) is 8.0 to 11.0, wherein the pH can be 8.0, 8.5, 9.0, 9.5, 10.0, 10.5 or 11.0, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0036] Preferably, in step (1), the median particle size of the first mixture is 4~6µm, wherein the median particle size can be 4µm, 4.2µm, 4.4µm, 4.6µm, 4.8µm, 5.0µm, 5.2µm, 5.4µm, 5.6µm, 5.8µm or 6µm, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0037] Preferably, the median particle size of the second mixture in step (1) is 15~17µm, wherein the median particle size can be 15µm, 15.2µm, 15.4µm, 15.6µm, 15.8µm, 16µm, 16.2µm, 16.4µm, 16.6µm, 16.8µm or 17µm, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0038] Preferably, the median particle size of the precipitate in step (1) is 4~6µm, wherein the median particle size can be 4µm, 4.2µm, 4.4µm, 4.6µm, 4.8µm, 5.0µm, 5.2µm, 5.4µm, 5.6µm, 5.8µm or 6µm, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0039] As a preferred technical solution of the present invention, the lithium source in step (2) includes any one or at least two of lithium carbonate, lithium hydroxide, lithium oxide or lithium peroxide, wherein typical but non-limiting examples of the combination include: a combination of lithium carbonate and lithium hydroxide, a combination of lithium hydroxide and lithium oxide, a combination of lithium oxide and lithium peroxide or a combination of lithium carbonate and lithium oxide, etc.

[0040] Preferably, in step (2), the lithium source and the NiMnMgAl highly doped cobalt carbonate are fed in a mass ratio of Li:Co of 1:(12~16), wherein the mass ratio can be 1:12, 1:13, 1:14, 1:15 or 1:16, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] As a preferred technical solution of the present invention, the dopant in step (2) is a compound containing element M, wherein element M is selected from any one or at least two combinations of La, Ti, Zr, Ce, Pr, Mo or Sr, wherein typical but non-limiting examples of such combinations include: combinations of La and Ti, combinations of Ti and Zr, combinations of Zr and Ce, combinations of Ce and Pr, combinations of Pr and Mo or combinations of Mo and Sr, etc.

[0042] Preferably, the element M accounts for 0.001 to 10% of the mass fraction of the NiMnMgAl highly doped cobalt carbonate, and the mass fraction can be 0.001%, 0.01%, 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0043] As a preferred technical solution of the present invention, the fourth mixing in step (2) includes adding the dopant to the mixture of NiMnMgAl highly doped cobalt carbonate and lithium source in the form of spray.

[0044] This invention employs a spray method to add dopant elements while mixing, resulting in more uniform doping of the additives.

[0045] Preferably, the sintering in step (2) includes a first sintering, a second sintering, and a third sintering.

[0046] Preferably, the first sintering temperature is 120~300℃, wherein the temperature can be 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃ or 300℃, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0047] Preferably, the first sintering time is 2 to 10 hours, wherein the time can be 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0048] Preferably, the second sintering temperature is 500~700℃, wherein the temperature can be 500℃, 520℃, 540℃, 560℃, 580℃, 600℃, 620℃, 640℃, 660℃, 680℃ or 700℃, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0049] Preferably, the second sintering time is 5 to 8 hours, wherein the time can be 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours or 8 hours, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0050] Preferably, the temperature of the third sintering is 900~1100℃, wherein the temperature can be 900℃, 920℃, 940℃, 960℃, 980℃, 1000℃, 1020℃, 1040℃, 1060℃, 1080℃ or 1100℃, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0051] Preferably, the third sintering time is 5 to 10 hours, wherein the time can be 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0052] As a preferred technical solution of the present invention, the coating in step (3) includes:

[0053] The coating agent and the lithium cobalt oxide matrix are sequentially mixed, calcined, and pulverized to obtain the lithium cobalt oxide cathode material.

[0054] Preferably, the coating agent comprises a solid electrolyte.

[0055] Preferably, the solid electrolyte includes any one or a combination of at least two of LLZO, LLTO, or LATP, wherein typical but non-limiting examples of the combination include: a combination of LLZO and LLTO, a combination of LLTO and LATP, or a combination of LLZO and LATP, etc.

[0056] Preferably, the coating agent accounts for 0.001 to 5% of the lithium cobalt oxide matrix by mass fraction. The mass fraction can be 0.001%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, or 5%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0057] This invention employs a method of coating solid electrolytes to improve the conductivity of materials.

[0058] As a preferred technical solution of the present invention, the calcination temperature is 800~1200℃, wherein the temperature can be 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃ or 1200℃, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0059] Preferably, the calcination time is 6 to 15 hours, wherein the time can be 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours or 15 hours, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0060] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0061] (1) Under a certain atmosphere, a first mixture with pH 8.0 to 11.0 and median particle size of 4 to 6 µm is obtained by adding cobalt salt solution, precipitant solution, aluminum salt, nickel salt, magnesium salt and manganese salt to complexing agent solution at a temperature of 40 to 80 °C and a stirring speed of 200 to 700 r / min. After removing 45 to 55% of the precipitate from the first mixture, a second mixture is obtained to obtain a second mixture with median particle size of 15 to 17 µm. After adding 10 to 100% of the removed precipitate to the second mixture, a third mixture is obtained to obtain a mixture with median particle size of 15 to 17 µm. After washing and drying, NiMnMgAl highly doped cobalt carbonate is obtained.

[0062] (2) The NiMnMgAl highly doped cobalt carbonate, lithium source and dopant described in step (1) are mixed in a fourth mixture by adding the dopant to the mixture of NiMnMgAl highly doped cobalt carbonate and lithium source in the form of spray, and then sintered to obtain lithium cobalt oxide matrix;

[0063] (3) Coating the lithium cobalt oxide matrix described in step (2) yields a lithium cobalt oxide cathode material.

[0064] The second objective of this invention is to provide an application of the preparation method of nickel-manganese-magnesium-aluminum co-doped lithium cobalt oxide cathode material as described in the first objective, wherein the preparation method is applied in the field of lithium-ion batteries.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] (1) The cathode material prepared by this invention has high capacity and good cycle performance, wherein the capacity at 4.65V 0.5C at 25℃ can reach 215 mAhg.-1 The cathode material provided by this invention, when used to make a battery, retains more than 95% of its capacity after 50 cycles at 25°C, 4.65V, and 0.5C.

[0067] (2) The compaction density of the cathode material prepared by this invention is 4.3 g / cm³. 3 The material's energy density can reach over 186 mAh / g at 4.5V.

[0068] (3) The present invention uses a method of coating solid electrolyte to improve the conductivity of the material. Attached Figure Description

[0069] Figure 1 This is a SEM image of nickel-manganese-magnesium-aluminum co-doped lithium cobalt oxide in Example 1 of the present invention.

[0070] Figure 2 This is a SEM image of nickel-manganese-magnesium-aluminum co-doped lithium cobalt oxide in Comparative Example 1 of this invention.

[0071] Figure 3 These are capacity cycling curves corresponding to the cathode materials in Examples 1-4 and Comparative Examples 1-5 of this invention.

[0072] Figure 4 These are retention rate cycle curves from Examples 1-4 and Comparative Examples 1-5 of the present invention. Detailed Implementation

[0073] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0074] Example 1

[0075] This embodiment provides a method for preparing a nickel-manganese-magnesium-aluminum co-doped lithium cobalt oxide cathode material, including the following steps:

[0076] (1) Ammonia water was added to the reactor as a complexing agent. Under a N2 atmosphere, at a temperature of 80℃, a pH of 11.0, and a stirring speed of 500 rpm, 2 mL of ammonia water was continuously added at a flow rate of 3 mL / min. A mol / L cobalt chloride solution, a precipitant solution, and a 2 mol / L potassium carbonate solution were added to the reactor in a co-current flow at a volume ratio of 1.1:1 to the cobalt salt solution. Simultaneously, a mixed solution of 0.5 mol / L aluminum chloride, 0.2 mol / L magnesium chloride, 0.2 mol / L nickel chloride, and 0.2 mol / L manganese chloride was added, ensuring that Al, Mg, Ni, and Mn elements accounted for 5%, 3%, 2%, and 2% of the mass of the NiMnMgAl highly doped cobalt carbonate, respectively. The reaction was stopped when the median particle size reached 5 µm. Half of the precipitate was then removed, and the reaction continued. When the median particle size reached 16 µm, 50% of the mass of the removed 5 µm precipitate was added. The reaction was stopped again when the median particle size reached 16 µm. The mixture was washed and dried to obtain NiMnMgAl highly doped cobalt carbonate.

[0077] (2) 200g of NiMnMgAl highly doped cobalt carbonate and lithium carbonate were placed in a mixer, where the Li / Co (molar ratio) was 0.9. Lanthanum oxide solution was added to the mixer in the form of spray, where the amount of La added was 5wt% of the mass of NiMnMgAl highly doped cobalt carbonate. Then it was placed in a muffle furnace for segmented sintering. The first sintering temperature was 150℃ and the calcination time was 5h. The second sintering temperature was 600℃ and the calcination time was 7h. The third sintering temperature was 1000℃ and the calcination time was 8h. After sintering, the mixture was crushed by a jaw crusher, a roller crusher, and an air jet mill in sequence to finally obtain the lithium cobalt oxide matrix.

[0078] (3) 200g of lithium cobalt oxide matrix was mixed with a certain amount of LLZO using a mixer, wherein the LLZO coating was weighed according to 2% of the mass of lithium cobalt oxide; the two mixtures were placed in a muffle furnace and calcined at 850℃ for 10h; the calcined lithium cobalt oxide was pulverized to obtain nickel-manganese-magnesium-aluminum co-doped 4.5V high-voltage lithium cobalt oxide cathode material. The SEM image of the nickel-manganese-magnesium-aluminum co-doped lithium cobalt oxide in this embodiment is shown below. Figure 1 As shown.

[0079] Example 2

[0080] This embodiment provides a method for preparing a nickel-manganese-magnesium-aluminum co-doped lithium cobalt oxide cathode material, including the following steps:

[0081] (1) Ammonia water was added to the reactor as a complexing agent. Under a N2 atmosphere, at a temperature of 60℃, a pH of 9.0, and a stirring speed of 600 rpm, 1.5 mL of ammonia water was continuously added at a flow rate of 2 mL / min. A 1 mol / L cobalt nitrate solution and a 2 mol / L sodium carbonate solution were added to the reactor in a co-current flow at a volume ratio of 1.2:1 to the cobalt salt solution. Simultaneously, a mixed solution of 0.8 mol / L aluminum sulfate, 0.4 mol / L magnesium nitrate, 0.5 mol / L nickel acetate, and 0.5 mol / L manganese nitrate was added, ensuring that Al, Mg, Ni, and Mn elements accounted for 8%, 3%, 4%, and 4% of the mass of the NiMnMgAl highly doped cobalt carbonate, respectively. The reaction was stopped when the median particle size reached 4 μm. Half of the precipitate was then removed, and the reaction continued. When the median particle size reached 15 μm, 80% of the mass of the 4 μm precipitate was added. The reaction was stopped again when the median particle size reached 15 μm. The mixture was washed and dried to obtain NiMnMgAl highly doped cobalt carbonate.

[0082] (2) 200g of NiMnMgAl highly doped cobalt carbonate and lithium carbonate were placed in a mixer, where the Li / Co (molar ratio) was 1.1. Titanium oxide solution was added to the mixer in the form of spray, where the amount of Ti added was 3wt% of the mass of NiMnMgAl highly doped cobalt carbonate. Then it was placed in a muffle furnace for segmented sintering. The first sintering temperature was 200℃ and the calcination time was 8h. The second sintering temperature was 500℃ and the calcination time was 8h. The third sintering temperature was 900℃ and the calcination time was 8h. After sintering, the mixture was crushed by a jaw crusher, a roller crusher, and an air jet mill in sequence to finally obtain the lithium cobalt oxide matrix.

[0083] (3) Take 200g of lithium cobalt oxide matrix and a certain amount of LLTO and mix them using a mixer. The amount of LLTO coating is 3% of the mass of lithium cobalt oxide. Place the two mixtures in a muffle furnace and calcine at 1000℃ for 7h. After calcination, the lithium cobalt oxide is crushed to obtain a nickel-manganese-magnesium-aluminum co-doped 4.5V high-voltage lithium cobalt oxide cathode material.

[0084] Example 3

[0085] This embodiment provides a method for preparing a nickel-manganese-magnesium-aluminum co-doped lithium cobalt oxide cathode material, including the following steps:

[0086] (1) Add ammonia water as a complexing agent to the reactor. Under N2 atmosphere, at a temperature of 50℃, a pH of 10.0, and a stirring speed of 300 rpm, continuously add 1 mL / min. A mol / L cobalt sulfate solution and a 1 mol / L sodium bicarbonate solution were added to the reactor in a co-current flow at a volume ratio of 1.4:1 to the cobalt salt solution. Simultaneously, a mixed solution of 0.4 mol / L aluminum nitrate, 0.6 mol / L magnesium sulfate, 0.2 mol / L nickel chloride, and 0.5 mol / L manganese sulfate was added, ensuring that Al, Mg, Ni, and Mn elements accounted for 2%, 4%, 3%, and 2% of the mass of the NiMnMgAl highly doped cobalt carbonate, respectively. The reaction was stopped when the median particle size reached 6 μm. Half of the precipitate was then removed, and the reaction continued. When the median particle size reached 17 μm, 40% of the mass of the removed 6 μm precipitate was added. The reaction was stopped again when the median particle size reached 17 μm. The mixture was washed and dried to obtain NiMnMgAl highly doped cobalt carbonate.

[0087] (2) 200g of NiMnMgAl highly doped cobalt carbonate and lithium carbonate were placed in a mixer, where the Li / Co (molar ratio) was 1.3. Strontium carbonate solution was added to the mixer in the form of spray, where the amount of Sr added was 2wt% of the mass of NiMnMgAl highly doped cobalt carbonate. Then it was placed in a muffle furnace for segmented sintering. The first sintering temperature was 260℃ and the calcination time was 3h. The second sintering temperature was 700℃ and the calcination time was 5h. The third sintering temperature was 900℃ and the calcination time was 10h. After sintering, the material was crushed by a jaw crusher, a roller crusher, and an air jet mill in sequence to finally obtain the lithium cobalt oxide matrix.

[0088] (3) Take 200g of lithium cobalt oxide matrix and a certain amount of LATP and mix them using a mixer. The LATP coating is weighed according to 1% of the mass of lithium cobalt oxide. Place the two mixtures in a muffle furnace and calcine at 1000℃ for 12h. After calcination, the lithium cobalt oxide is crushed to obtain a nickel-manganese-magnesium-aluminum co-doped 4.5V high-voltage lithium cobalt oxide cathode material.

[0089] Example 4

[0090] This embodiment provides a method for preparing a nickel-manganese-magnesium-aluminum co-doped lithium cobalt oxide cathode material, including the following steps:

[0091] (1) Ammonia water was added to the reactor as a complexing agent. Under a N2 atmosphere, at a temperature of 60℃, a pH of 9.0, and a stirring speed of 600 rpm, 1.5 mL of ammonia water was continuously added at a flow rate of 2 mL / min. A cobalt chloride solution of 1 mol / L and a potassium carbonate solution of 2 mol / L were added to the reactor in a co-current flow at a volume ratio of 1.2:1 to the cobalt salt solution. Simultaneously, a mixed solution of aluminum chloride (0.8 mol / L), magnesium chloride (0.4 mol / L), nickel chloride (0.5 mol / L), and manganese chloride (0.5 mol / L) was added, such that Al, Mg, Ni, and Mn elements accounted for 8%, 3%, 4%, and 4% of the mass of the NiMnMgAl highly doped cobalt carbonate, respectively. The reaction was stopped when the median particle size reached 4 μm. Half of the precipitate was then removed, and the reaction continued. When the median particle size reached 16 μm, 80% of the mass of the 4 μm precipitate was added. The reaction was stopped again when the median particle size reached 16 μm. The mixture was then washed and dried to obtain NiMnMgAl highly doped cobalt carbonate.

[0092] (2) 200g of NiMnMgAl highly doped cobalt carbonate and lithium carbonate were placed in a mixer, where the Li / Co (molar ratio) was 1.1. Lanthanum oxide solid phase was added to the mixer, where the amount of La added was 3wt% of the mass of NiMnMgAl highly doped cobalt carbonate. Then it was placed in a muffle furnace for segmented sintering. The first sintering temperature was 200℃ and the calcination time was 8h. The second sintering temperature was 500℃ and the calcination time was 8h. The third sintering temperature was 900℃ and the calcination time was 8h. After sintering, the material was crushed by a jaw crusher, a roller mill, and an air jet mill in sequence to finally obtain the lithium cobalt oxide matrix.

[0093] (3) Take 200g of lithium cobalt oxide matrix and a certain amount of LLZO and mix them using a mixer. The amount of LLZO coated is 3% of the mass of lithium cobalt oxide. Place the two mixtures in a muffle furnace and calcine at 1000℃ for 7h. After calcination, the lithium cobalt oxide is crushed to obtain a nickel-manganese-magnesium-aluminum co-doped 4.5V high-voltage lithium cobalt oxide cathode material.

[0094] Example 5

[0095] In this embodiment, the segmented sintering in the muffle furnace in step (2) is replaced with two-stage sintering: the first stage sintering temperature is 350℃ and sintering time is 10h, and the second stage sintering temperature is 1000℃ and sintering time is 10h. All other conditions are the same as in Example 1.

[0096] Example 6

[0097] In this embodiment, except that LLZO in step (3) is replaced with alumina, all other conditions are the same as in Example 1.

[0098] Example 7

[0099] In this embodiment, except that step (3) of coating LLZO by weighing 2% of the mass of lithium cobalt oxide is replaced by coating LLZO by weighing 8% of the mass of lithium cobalt oxide, all other conditions are the same as in Example 1.

[0100] Comparative Example 1

[0101] This comparative example provides a method for preparing a nickel-manganese-magnesium-aluminum co-doped lithium cobalt oxide cathode material, including the following steps:

[0102] (1) Ammonia water was added to the reactor as a complexing agent. Under N2 atmosphere, at a temperature of 60℃, pH of 9, and stirring speed of 600 rpm, 1.5 mol / L cobalt chloride solution and 2 mol / L potassium bicarbonate solution were continuously added to the reactor at a flow rate of 2 mL / min in a co-current ratio of 1.2:1 to the cobalt salt solution. At the same time, a mixed solution of 0.8 mol / L aluminum chloride, 0.4 mol / L magnesium chloride, 0.5 mol / L nickel chloride, and 0.5 mol / L manganese chloride was added so that Al, Mg, Ni, and Mn elements accounted for 8%, 3%, 4%, and 4% of the mass of NiMnMgAl highly doped cobalt carbonate, respectively. When the median particle size was 16 μm, the reaction was stopped, and the mixture was washed and dried to obtain NiMnMgAl highly doped cobalt carbonate.

[0103] (2) 200g of NiMnMgAl highly doped cobalt carbonate and lithium carbonate were placed in a mixer, where the Li / Co (molar ratio) was 1.1. Lanthanum oxide solution was added to the mixer in the form of spray, where the amount of La added was 3wt% of the mass of NiMnMgAl highly doped cobalt carbonate. Then it was placed in a muffle furnace for segmented sintering. The first sintering temperature was 200℃ and the calcination time was 8h. The second sintering temperature was 500℃ and the calcination time was 8h. The third sintering temperature was 900℃ and the calcination time was 8h. After sintering, the mixture was crushed by a jaw crusher, a roller crusher, and an air jet mill in sequence to finally obtain the lithium cobalt oxide matrix.

[0104] (3) 200g of lithium cobalt oxide matrix was mixed with a certain amount of LLZO using a mixer, wherein the LLZO coating was weighed according to 3% of the mass of lithium cobalt oxide; the two mixtures were placed in a muffle furnace and calcined at 1000℃ for 7h; the calcined lithium cobalt oxide was pulverized to obtain a nickel-manganese-magnesium-aluminum co-doped 4.5V high-voltage lithium cobalt oxide cathode material. The SEM image of the nickel-manganese-magnesium-aluminum co-doped material in this comparative example is shown below. Figure 2 As shown.

[0105] Comparative Example 2

[0106] This comparative example provides a method for preparing a magnesium-aluminum co-doped lithium cobalt oxide cathode material, including the following steps:

[0107] (1) Ammonia water was added to the reactor as a complexing agent. Under N2 atmosphere, at a temperature of 80℃, a pH of 11.0 and a stirring speed of 500 rpm, 2 mol / L cobalt chloride solution and precipitant solution were continuously added to the reactor at a flow rate of 3 mL / min. Sodium carbonate solution with a concentration of 2 mol / L was added to the reactor in parallel flow at a volume ratio of 1.1:1 with cobalt salt solution. At the same time, a mixed solution of aluminum chloride with a concentration of 0.5 mol / L and magnesium chloride with a concentration of 0.2 mol / L was added so that Al and Mg elements accounted for 2% and 2% of the mass of MgAl highly doped cobalt carbonate, respectively. When the median particle size reached 5 μm, the reaction was stopped. Half of the precipitate was then taken out and the reaction was continued. When the median particle size reached 16 μm, 50% of the mass of the 5 μm precipitate was added. When the median particle size reached 16 μm again, the reaction was stopped. The precipitate was washed and dried to obtain MgAl highly doped cobalt carbonate.

[0108] (2) 200g of MgAl highly doped cobalt carbonate and lithium carbonate were placed in a mixer, where the Li / Co (molar ratio) was 0.9. Lanthanum oxide solution was added to the mixer in the form of spray, where the amount of La added was 5wt% of the mass of MgAl highly doped cobalt carbonate. Then it was placed in a muffle furnace for segmented sintering. The first sintering temperature was 150℃ and the calcination time was 5h. The second sintering temperature was 600℃ and the calcination time was 7h. The third sintering temperature was 1000℃ and the calcination time was 8h. After sintering, the mixture was crushed by a jaw crusher, a roller crusher, and an air jet mill in sequence to finally obtain the lithium cobalt oxide matrix.

[0109] (3) Take 200g of lithium cobalt oxide matrix and a certain amount of LLZO and mix them using a mixer. The amount of LLZO coated is 2% of the mass of lithium cobalt oxide. Place the two mixtures in a muffle furnace and calcine at 850℃ for 10h. After calcination, the lithium cobalt oxide is crushed to obtain magnesium-aluminum co-doped 4.5V high voltage lithium cobalt oxide cathode material.

[0110] Comparative Example 3

[0111] This comparative example provides a method for preparing a nickel-manganese co-doped lithium cobalt oxide cathode material, including the following steps:

[0112] (1) Ammonia water was added to the reactor as a complexing agent. Under N2 atmosphere, at a temperature of 80℃, a pH of 11.0 and a stirring speed of 500 rpm, 2 mol / L cobalt chloride solution and precipitant solution were continuously added to the reactor at a flow rate of 3 mL / min. Potassium carbonate solution with a concentration of 2 mol / L was added to the reactor in parallel flow at a volume ratio of 1.1:1 to cobalt salt solution. At the same time, a mixed solution of nickel chloride with a concentration of 0.2 mol / L and manganese chloride with a concentration of 0.2 mol / L was added so that Ni and Mn elements accounted for 2% and 2% of the mass of NiMn highly doped cobalt carbonate, respectively. When the median particle size reached 5 μm, the reaction was stopped. Half of the precipitate was then taken out and the reaction was continued. When the median particle size reached 16 μm, 50% of the mass of the 5 μm precipitate was added. When the median particle size reached 16 μm again, the reaction was stopped. The precipitate was washed and dried to obtain NiMn highly doped cobalt carbonate.

[0113] (2) 200g of NiMn highly doped cobalt carbonate and lithium carbonate were placed in a mixer, where the Li / Co (molar ratio) was 0.9. Lanthanum oxide solution was added to the mixer in the form of spray, where the amount of La added was 5wt% of the mass of NiMn highly doped cobalt carbonate. Then it was placed in a muffle furnace for segmented sintering. The first sintering temperature was 150℃ and the calcination time was 5h. The second sintering temperature was 600℃ and the calcination time was 7h. The third sintering temperature was 1000℃ and the calcination time was 8h. After sintering, the mixture was crushed by a jaw crusher, a roller crusher, and an air jet mill in sequence to finally obtain the lithium cobalt oxide matrix.

[0114] (3) Take 200g of lithium cobalt oxide matrix and a certain amount of LLZO and mix them using a mixer. The amount of LLZO coated is 2% of the mass of lithium cobalt oxide. Place the two mixtures in a muffle furnace and calcine at 850℃ for 10h. After calcination, the lithium cobalt oxide is crushed to obtain nickel-manganese co-doped 4.5V high voltage lithium cobalt oxide cathode material.

[0115] Comparative Example 4

[0116] This comparative example provides a method for preparing a lithium cobalt oxide cathode material, including the following steps:

[0117] (1) Ammonia water was added to the reactor as a complexing agent. Under N2 atmosphere, at a temperature of 80℃, a pH of 11.0 and a stirring speed of 500 rpm, 2 mol / L cobalt chloride solution and precipitant solution were continuously added at a flow rate of 3 mL / min. Potassium carbonate solution with a concentration of 2 mol / L was added to the reactor in parallel flow at a volume ratio of 1.1:1 to cobalt salt solution. When the median particle size reached 5 μm, the reaction was stopped. Half of the precipitate was then removed and the reaction was continued. When the median particle size reached 16 μm, 50% of the amount of the 5 μm precipitate was added. When the median particle size reached 16 μm again, the reaction was stopped. The precipitate was washed and dried to obtain cobalt carbonate.

[0118] (2) 200g of cobalt carbonate and lithium carbonate were placed in a mixer, with Li / Co (molar ratio) = 0.9. Lanthanum oxide solution was added to the mixer in the form of spray, with the amount of La added being 5wt% of the mass of cobalt carbonate. Then, it was placed in a muffle furnace for segmented sintering. The first sintering temperature was 150℃ and the calcination time was 5h. The second sintering temperature was 600℃ and the calcination time was 7h. The third sintering temperature was 1000℃ and the calcination time was 8h. After sintering, the mixture was crushed by a jaw crusher, a roller mill, and an air jet mill in sequence to finally obtain the lithium cobalt oxide matrix.

[0119] (3) Take 200g of lithium cobalt oxide matrix and a certain amount of LLZO and mix them using a mixer. The amount of LLZO coated is 2% of the mass of lithium cobalt oxide. Place the two mixtures in a muffle furnace and calcine at 850℃ for 10h. After calcination, the lithium cobalt oxide is crushed to obtain a 4.5V high voltage lithium cobalt oxide cathode material (LiCoO2).

[0120] Comparative Example 5

[0121] This comparative example provides a method for preparing a nickel-manganese-magnesium-aluminum co-doped lithium cobalt oxide cathode material, including the following steps:

[0122] (1) Ammonia water was added to the reactor as a complexing agent. Under a N2 atmosphere, at a temperature of 60℃, a pH of 9.0, and a stirring speed of 600 rpm, 1.5 mL of ammonia water was continuously added at a flow rate of 2 mL / min. A cobalt chloride solution, a precipitant solution, and a sodium carbonate solution of 2 mol / L were added to the reactor in a co-current flow at a volume ratio of 1.2:1 to the cobalt salt solution. Simultaneously, a mixed solution of aluminum chloride (0.8 mol / L), magnesium chloride (0.4 mol / L), nickel chloride (0.5 mol / L), and manganese chloride (0.5 mol / L) was added, ensuring that Al, Mg, Ni, and Mn elements accounted for 8%, 3%, 4%, and 4% of the mass of the NiMnMgAl highly doped cobalt carbonate, respectively. The reaction was stopped when the median particle size reached 4 μm. Half of the precipitate was then removed, and the reaction continued. When the median particle size reached 16 μm, 80% of the mass of the removed 4 μm precipitate was added. The reaction was stopped again when the median particle size reached 16 μm. The mixture was then washed and dried to obtain NiMnMgAl highly doped cobalt carbonate.

[0123] (2) 200g of NiMnMgAl highly doped cobalt carbonate and lithium carbonate were placed in a mixer, where the Li / Co (molar ratio) was 1.1. Lanthanum oxide solution was added to the mixer in the form of spray, where the amount of La added was 3wt% of the mass of NiMnMgAl highly doped cobalt carbonate. Then it was placed in a muffle furnace for segmented sintering. The first sintering temperature was 200℃ and the calcination time was 8h. The second sintering temperature was 500℃ and the calcination time was 8h. The third sintering temperature was 900℃ and the calcination time was 8h. After sintering, the material was crushed by a jaw crusher, a roller crusher, and an air jet mill in sequence to finally obtain lithium cobalt oxide cathode material.

[0124] Comparative Example 6

[0125] The only difference between this comparative example and Example 1 is that the step (1) of removing half of the precipitate before continuing the reaction is replaced with removing 30% of the precipitate before continuing the reaction.

[0126] Comparative Example 7

[0127] The only difference between this comparative example and Example 1 is that the step (1) of removing half of the precipitate before continuing the reaction is replaced with removing 70% of the precipitate before continuing the reaction.

[0128] Comparative Example 8

[0129] The only difference between this comparative example and Example 1 is that the reaction was stopped when the median particle size was 5 μm, and the addition of 50% of the amount of 5 μm precipitate when the median particle size was 16 μm was replaced with the reaction being stopped when the median particle size was 8 μm, and the addition of 50% of the amount of 8 μm precipitate when the median particle size was 16 μm.

[0130] Comparative Example 9

[0131] The only difference between this comparative example and Example 1 is that the reaction was stopped when the median particle size was 5 μm, and the addition of 50% of the amount of 5 μm precipitate when the median particle size was 16 μm was replaced with the reaction being stopped when the median particle size was 2 μm, and the addition of 50% of the amount of 2 μm precipitate when the median particle size was 16 μm.

[0132] The positive electrode materials from Examples 1-7 and Comparative Examples 1-9 were assembled into batteries for testing. Graphite was selected as the negative electrode material, and coin cells were used. The tests included battery cycle testing and tests of the conductivity and compaction density of the positive electrode materials. The test results are shown in Table 1. The capacity cycle curves corresponding to the positive electrode materials in Examples 1-4 and Comparative Examples 1-5 are shown in the figure below. Figure 3 As shown. The retention rate cycle curves in Examples 1-4 and Comparative Examples 1-5 of the present invention are shown in the figure. Figure 4 As shown.

[0133]

[0134] The results above show that: comparing Examples 1 and 5, it can be seen that replacing the sintering method from three-stage sintering to two-stage sintering reduces the conductivity of the solid electrolyte and slightly decreases the cycle performance; comparing Examples 1 and 6, it can be seen that replacing LLZO with alumina reduces the conductivity of the solid electrolyte; compared to Examples 1 and 7, increasing the content of the coating agent increases the conductivity of the solid electrolyte, but reduces the cycle performance and compaction density.

[0135] As can be seen from Example 1 and Comparative Example 1, the absence of small particles in the preparation of cobalt carbonate significantly reduces the compaction density. As can be seen from Example 1 and Comparative Examples 2-4, the cycling performance and capacity of undoped NiMnMgAl deteriorate somewhat during the synthesis of cobalt carbonate. As can be seen from Example 1 and Comparative Example 5, the conductivity of the material without solid electrolyte coating is significantly reduced, and the cycling performance also deteriorates. As can be seen from Example 1 and Comparative Examples 6-7, adjusting the proportion of small particles removed during the synthesis of cobalt carbonate reduces the compaction density of the material. As can be seen from Example 1 and Comparative Examples 8-9, adjusting the particle size of small particles during the synthesis of cobalt carbonate not only reduces the compaction density but also reduces the capacity and cycling performance.

[0136] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a nickel-manganese-magnesium-aluminum co-doped lithium cobalt oxide cathode material, characterized in that, The preparation method includes the following steps: (1) Under a certain atmosphere, cobalt salt solution, precipitant solution, aluminum salt, nickel salt, magnesium salt and manganese salt are added to complexing agent solution for first mixing to obtain a first mixed liquid with a median particle size of 4~6µm. After taking out 45~55% of the precipitate with a median particle size of 4~6µm from the first mixed liquid, a second mixing is carried out to obtain a second mixed liquid with a median particle size of 15~17µm. After adding 10~100% of the precipitate with a median particle size of 4~6µm to the second mixed liquid, a third mixing is carried out to obtain a third mixed liquid with a median particle size of 15~17µm. After washing and drying, NiMnMgAl highly doped cobalt carbonate is obtained. (2) After mixing the NiMnMgAl highly doped cobalt carbonate, lithium source and dopant in step (1) for the fourth time, sinter to obtain lithium cobalt oxide matrix; The dopant is a compound containing element M, wherein element M is selected from any one or a combination of at least two of La, Ti, Zr, Ce, Pr, Mo or Sr; The sintering includes a first sintering, a second sintering, and a third sintering; The first sintering temperature is 120~300℃; The second sintering temperature is 500~700℃; The temperature of the third sintering is 900~1100℃; (3) Coating the lithium cobalt oxide matrix described in step (2) yields a lithium cobalt oxide cathode material.

2. The preparation method according to claim 1, characterized in that, The co-current volume ratio of the cobalt salt solution and the precipitant solution in step (1) is 1:(1.0~1.5).

3. The preparation method according to claim 1, characterized in that, The flow rate of the cobalt salt solution is 0.2~3 mL / min.

4. The preparation method according to claim 1, characterized in that, The cobalt salt solution includes any one or a combination of at least two of the following: cobalt sulfate solution, cobalt chloride solution, cobalt nitrate solution, or cobalt acetate solution.

5. The preparation method according to claim 1, characterized in that, The concentration of the precipitant in the precipitant solution is 1~3 mol / L.

6. The preparation method according to claim 1, characterized in that, The precipitant includes any one or a combination of at least two of ammonia, alkali metal carbonates, alkali metal bicarbonates, or alkaline earth metal bicarbonates.

7. The preparation method according to claim 6, characterized in that, The alkali metal carbonates include sodium carbonate and / or potassium carbonate.

8. The preparation method according to claim 6, characterized in that, The alkali metal bicarbonate includes sodium bicarbonate and / or potassium bicarbonate.

9. The preparation method according to claim 6, characterized in that, The alkaline earth metal bicarbonates include barium bicarbonate and / or calcium bicarbonate.

10. The preparation method according to claim 1, characterized in that, The concentration of the aluminum salt in the first mixture is 0.1~1 mol / L.

11. The preparation method according to claim 1, characterized in that, The aluminum salt includes any one or a combination of at least two of aluminum chloride, aluminum sulfate, or sodium aluminate.

12. The preparation method according to claim 1, characterized in that, The concentration of the magnesium salt in the first mixture is 0.1~1 mol / L.

13. The preparation method according to claim 1, characterized in that, The magnesium salt includes any one or a combination of at least two of magnesium chloride, magnesium sulfate, or magnesium nitrate.

14. The preparation method according to claim 1, characterized in that, The concentration of the nickel salt in the first mixture is 0.1~1 mol / L.

15. The preparation method according to claim 1, characterized in that, The nickel salt includes any one or a combination of at least two of nickel sulfate, nickel nitrate, nickel chloride, or nickel acetate.

16. The preparation method according to claim 1, characterized in that, The concentration of the manganese salt in the first mixture is 0.1~1 mol / L.

17. The preparation method according to claim 1, characterized in that, The manganese salt includes any one or a combination of at least two of manganese chloride, manganese sulfate, or manganese nitrate.

18. The preparation method according to claim 1, characterized in that, The specific atmosphere mentioned in step (1) includes a nitrogen atmosphere.

19. The preparation method according to claim 1, characterized in that, Step (1) The temperature of the first mixture is 40~80℃.

20. The preparation method according to claim 1, characterized in that, Step (1) The stirring speed of the first mixture is 200~700r / min.

21. The preparation method according to claim 1, characterized in that, Step (1) The pH of the first mixture is 8.0~11.

0.

22. The preparation method according to claim 1, characterized in that, The lithium source in step (2) includes any one or a combination of at least two of lithium carbonate, lithium hydroxide, lithium oxide, or lithium peroxide.

23. The preparation method according to claim 1, characterized in that, In step (2), the lithium source and the NiMnMgAl highly doped cobalt carbonate are fed in a mass ratio of Li:Co of 1:(12~16).

24. The preparation method according to claim 1, characterized in that, Based on mass fraction, the element M accounts for 0.001~10% of the mass fraction of the NiMnMgAl highly doped cobalt carbonate.

25. The preparation method according to claim 1, characterized in that, Step (2) The fourth mixing involves adding the dopant in the form of a spray into a mixture of NiMnMgAl highly doped cobalt carbonate and a lithium source.

26. The preparation method according to claim 1, characterized in that, The first sintering time is 2~10h.

27. The preparation method according to claim 1, characterized in that, The second sintering time is 5-8 hours.

28. The preparation method according to claim 1, characterized in that, The third sintering time is 5-10 hours.

29. The preparation method according to claim 1, characterized in that, The coating in step (3) includes: The coating agent and the lithium cobalt oxide matrix are sequentially mixed, calcined, and pulverized to obtain the lithium cobalt oxide cathode material.

30. The preparation method according to claim 29, characterized in that, The coating agent includes a solid electrolyte.

31. The preparation method according to claim 30, characterized in that, The solid electrolyte includes any one or a combination of at least two of LLZO, LLTO, or LATP.

32. The preparation method according to claim 29, characterized in that, The coating agent accounts for 0.001 to 5% of the mass fraction of the lithium cobalt oxide matrix.

33. The preparation method according to claim 29, characterized in that, The calcination temperature is 800~1200℃.

34. The preparation method according to claim 29, characterized in that, The calcination time is 6-15 hours.

35. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: (1) Under a certain atmosphere, a first mixture with pH 8.0 to 11.0 and median particle size of 4 to 6 µm is obtained by adding cobalt salt solution, precipitant solution, aluminum salt, nickel salt, magnesium salt and manganese salt to complexing agent solution and mixing at a temperature of 40 to 80 °C and a stirring speed of 200 to 700 r / min. After removing 45 to 55% of the precipitate with median particle size of 4 to 6 µm from the first mixture, a second mixture is obtained to obtain a second mixture with median particle size of 15 to 17 µm. After adding 10 to 100% of the removed precipitate with median particle size of 4 to 6 µm to the second mixture, a third mixture is obtained to obtain a third mixture with median particle size of 15 to 17 µm. After washing and drying, NiMnMgAl highly doped cobalt carbonate is obtained. (2) The NiMnMgAl highly doped cobalt carbonate, lithium source and dopant described in step (1) are mixed in a fourth mixture by adding the dopant to the mixture of NiMnMgAl highly doped cobalt carbonate and lithium source in the form of spray, and then sintered to obtain lithium cobalt oxide matrix; (3) Coating the lithium cobalt oxide matrix described in step (2) yields a lithium cobalt oxide cathode material.

36. The application of a method for preparing a nickel-manganese-magnesium-aluminum co-doped lithium cobalt oxide cathode material as described in any one of claims 1-35, characterized in that, The preparation method described herein is applied in the field of lithium-ion batteries.

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