Preparation method of doped co-coated high-nickel ternary lithium nickel cobalt manganese oxide material

Abstract

This invention provides a method for preparing a high-nickel ternary lithium nickel cobalt manganese oxide material with doped co-coating, wherein the ternary cathode material precursor Ni x Co y Mn 1‑x‑y (OH)2, coarse-particle lithium carbonate is mixed with dopant element K and then mixed at high speed using a star-shaped ball mill, wherein 250 r / min ≤ rotation speed ≤ 500 r / min, and 100 min ≤ mixing time ≤ 150 min; after mixing, the material to be sintered, A, is obtained. The material to be sintered, A, is placed in a box, and the material in the box is marked in a grid pattern with a 3-5 mm wide iron sheet to facilitate full contact between the material and oxygen, which can solve the element segregation problem of multi-element synergistic doping. Under high cutoff voltage conditions, a high-nickel ternary cathode material with excellent performance is obtained.

Description

Technical Field

[0001] This invention relates to the field of high-voltage lithium-ion battery cathode materials, and more particularly to a method for preparing a high-nickel ternary nickel-cobalt-manganese lithium oxide material with doped and co-coated structure. Background Technology

[0002] In recent years, lithium-ion batteries have been widely used in electric vehicles, consumer electronics, and power tools due to their advantages such as high energy density, high operating voltage, small size, and no memory effect. With the continuous improvement of people's living standards, the application scenarios of lithium-ion batteries are becoming increasingly diverse, including low-altitude economy, drones, and aerospace. Furthermore, increasingly higher energy density requirements are being placed on lithium-ion batteries. Currently, the main lithium-ion cathode materials include lithium cobalt oxide, lithium iron phosphate, and ternary cathode materials. Ternary cathode materials can be divided into NCM and NCA materials (Ni / Co / Mn, Ni / Co / Al) according to their main content. Based on their microstructure, ternary cathode materials can be further divided into polycrystalline and monocrystalline cathode materials. Polycrystalline cathode materials are generally composed of primary particles with a primary particle size of 300-1000 nm, exhibiting generally high capacity utilization and good rate performance. Monocrystalline cathode materials are composed of single-crystal particles with a primary particle size of approximately 1-5 μm, with distinct grain boundaries between particles, high structural stability, and good tolerance to high cutoff voltages. Due to its advantages such as high specific capacity, ease of processing, and low cost, ternary cathode materials have gradually become a research hotspot for lithium-ion battery cathode materials. In recent years, to meet the ever-increasing demand for high energy density in lithium-ion batteries, cathode materials have been developing in two directions: ① High nickel content. In ternary cathode materials, Ni mainly participates in redox reactions. The higher the nickel content, the more redox couples are provided. According to the theoretical capacity calculation formula for active materials: C0 = m / M × Ne × 26.8 A•h = (m / K)•C, the more redox couples provided, the more capacity is released. Therefore, increasing the proportion of nickel in ternary materials can effectively improve the capacity of ternary cathode materials; ② Increasing the cutoff voltage during lithium battery use. According to the energy density formula: W = EV, increasing the cutoff voltage V of lithium-ion batteries can release more lithium ions and improve the capacity of cathode materials. However, with the increase of the cutoff voltage, a large amount of Ni in the ternary cathode material will also be released. 2+ Ni 3+ Losing electrons and transforming into a large amount of Ni 4+ Ni 4+ It has strong oxidizing properties and easily reacts with lattice oxygen, causing lattice oxygen to lose electrons and be converted into oxygen gas, resulting in the collapse of the material structure and the release of a large amount of heat, which can lead to thermal runaway of the material. This results in a deterioration of the safety performance of lithium batteries and may even cause major safety accidents. This phenomenon becomes more and more serious as the nickel content in ternary cathode materials increases.

[0003] In order to improve the capacity of ternary cathode materials and avoid the above problems, it is generally necessary to modify the ternary cathode materials.

[0004] Chinese invention patent CN113620352A discloses a method for preparing high-voltage ternary single-crystal cathode materials by co-doping with three oxides. This method is mainly for low-nickel high-voltage single-crystal cathode materials (Nimol≤60%). The material contains a large amount of Co and Mn elements, and the structure itself is relatively stable. In addition, a dry mixing process is used, and the proportion of dopant is low, but it will still cause segregation of dopant elements. Furthermore, only aluminum hydroxide is used as a coating material, which will lead to an increase in the surface resistance of the material and a slowdown in the transport performance of Li ions, resulting in a decrease in the rate performance of the material.

[0005] Chinese invention patent CN116722119B discloses a method for preparing a composite high-voltage ternary cathode material. The method involves mixing and evaporating a mixed solution of a precursor with dysprosium, cerium, and niobium salts, followed by high-temperature solid-state sintering with a lithium source to obtain a composite high-voltage ternary cathode material with niobium doping and synergistic coating of oxygen-ion conductors and fast-ion conductors. The method utilizes the formed oxygen-ion conductor Ce... 0.8 Dy 0.2 O 1.9 The coating layer is used to suppress activated surface lattice oxygen ions, utilizing the formed Li8CeO6 & LiN b O3 / Li3NbO4 acts as a fast ion conductor to enhance the Li diffusion rate at the cathode material-electrolyte interface. Additionally, some Nb diffuses into the ternary cathode material, replacing a portion of the Ni. 2+ This method can reduce lithium-nickel mixing and improve the high-voltage cycle stability of ternary cathode materials. However, through a single high-temperature sintering process, the Nb, Ce, and Dy elements coated on the precursor surface will simultaneously dop into the crystal lattice under high-temperature conditions. This may not necessarily form a stable Li8CeO6&LiNbO3 / Li3NbO4 fast ion conductor layer on the cathode material surface. In addition, as the lithium source melts at high temperatures, the solid-solid reaction becomes a solid-liquid reaction. The molten lithium salt will cause segregation of the surface-coated elements, resulting in uneven doping and affecting the high-voltage performance of the material.

[0006] Therefore, how to efficiently and easily obtain high-nickel single-crystal ternary cathode materials with good electrochemical performance suitable for high-voltage systems is an urgent technical problem to be solved. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of the prior art by providing a method for preparing a high-nickel ternary lithium nickel cobalt manganese oxide material with doped co-coating.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] This invention provides a method for preparing a high-nickel ternary lithium nickel cobalt manganese oxide material with doped co-coating, comprising the following steps:

[0010] S1, Ni, a ternary cathode material precursor x Co y Mn 1-x-y (OH)2, coarse-particle lithium carbonate is mixed with doped element K and then mixed at high speed using a star ball mill, wherein 250 r / min ≤ rotation speed ≤ 500 r / min, and 100 min ≤ mixing time ≤ 150 min;

[0011] After mixing, the material to be sintered, A, is obtained. The material to be sintered, A, is placed into the box, and the material in the box is marked with a 3-5mm wide iron sheet in a grid pattern to facilitate full contact between the material and oxygen.

[0012] In terms of molar ratio, in the ternary cathode material precursor, 0.80≤x≤0.95, 0.02≤y≤0.15, 0.02≤1-xy≤0.15, and D50≤2.5-4.5μm;

[0013] The particle size of the coarse lithium carbonate is D50 = 500-1000 μm;

[0014] The lithium ratio (Li / M) is 0.5~0.6;

[0015] The content of the dopant element K, by weight percentage, is: 15000ppm≤k≤25000ppm;

[0016] S2. Place the material A to be sintered into a box furnace for high-temperature sintering, and maintain the oxygen concentration in the furnace at ≥96% throughout the process. Increase the temperature from 25°C at 3°C / min, and hold at 500°C for 4 hours. After holding, increase the temperature at 3°C / min to 700-830°C and sinter at a constant temperature for 15 hours. Then, decrease the temperature at 5°C / min to 300°C, turn off the power, and take out the material after the material temperature drops to room temperature to obtain material B.

[0017] S3. After crushing and sieving the material B, add it to an ethanol solution at a mass ratio of 1:1.2. Add lithium according to a lithium ratio of Li / M of 0.54~0.60. After the lithium addition is completed, evaporate the solution to dryness to obtain the cathode material C to be sintered with lithium for secondary addition.

[0018] Furthermore, it also includes:

[0019] S4. The positive electrode material C is placed into a crucible, and lines are drawn in a grid pattern using a 3-5mm wide iron sheet to facilitate full contact between the material and oxygen. The positive electrode material C in the crucible is placed into a box furnace for high-temperature sintering, and the oxygen concentration in the furnace is maintained at ≥96% throughout the process. The temperature is increased from 25℃ at a rate of 3℃ / min, and then held at 500℃ for 4 hours. After the holding period, the temperature is increased at a rate of 3℃ / min to 800-900℃ for constant-temperature sintering for 12 hours. Then the temperature is reduced to 300℃ at a rate of 5℃ / min. The power is turned off, and the material is removed after the temperature drops to room temperature to obtain the sintered material D.

[0020] Furthermore, it also includes:

[0021] S5. After crushing and sieving the sintered material D, add it to an ethanol solution at a ratio of 1:1.2, add aluminum hydroxide and solid electrolyte, and stir at high speed with a stirrer. After stirring, evaporate the solution to obtain the coated material E to be sintered three times.

[0022] Furthermore, it also includes:

[0023] S6. Place the material E to be sintered three times, which is packed in a box, into a box furnace for high-temperature sintering. Maintain the oxygen concentration in the furnace at ≥96% throughout the process. Increase the temperature from 25℃ at 3℃ / min, raise it to 300-700℃ and hold it for 10 hours. Then, decrease the temperature to 300℃ at 5℃ / min. Turn off the power and wait for the material temperature to drop to room temperature to obtain the finished material F.

[0024] S7. The finished material F is made into button batteries and soft-pack batteries for electrical performance evaluation.

[0025] Furthermore, the dopant element K is composed of flux, fluoride and metal element oxide, and the original crystal size of the additive is controlled at 150±50nm.

[0026] The flux is one or more selected from boric acid, boron oxide, bismuth oxide, molybdenum oxide, tungsten oxide, zinc oxide, strontium oxide, and strontium carbonate.

[0027] The fluoride is one or more of lithium fluoride, aluminum fluoride, lithium aluminum fluoride, titanium fluoride, magnesium fluoride, zirconium fluoride, lanthanum fluoride, and yttrium fluoride;

[0028] The metal oxide is one or more of the following: zirconium oxide, aluminum oxide, magnesium oxide, barium oxide, lanthanum oxide, yttrium oxide, titanium oxide, tungsten oxide, molybdenum oxide, strontium oxide, vanadium oxide, niobium oxide, and tantalum oxide.

[0029] Furthermore, the BET of the aluminum hydroxide is ≥80 cm⁻¹ 2 / g;

[0030] The aluminum hydroxide is 2500~5000 ppm by weight percentage;

[0031] The solid electrolyte is one or more of LLZO, LATP, LLTO, LPS, and LGPS;

[0032] The original crystal size of the solid electrolyte is ≤150nm;

[0033] The solid electrolyte is 4000-7000 ppm by weight percentage.

[0034] The beneficial effects of this invention are: it can solve the element segregation problem of multi-element synergistic doping, and obtain a high-nickel ternary cathode material with excellent performance under high cutoff voltage conditions. Attached Figure Description

[0035] Figure 1 A flowchart of a method for preparing a high-nickel ternary lithium nickel cobalt manganese oxide material with doped co-coating;

[0036] Figure 2 (a) is a SEM image of Example 1;

[0037] Figure 2 (b) is the SEM image of Comparative Example 1;

[0038] Figure 2 (c) is a SEM image of Example 2;

[0039] Figure 2 (d) is the SEM image of Comparative Example 2;

[0040] Figure 3 The coin charge rate performance diagrams are for the examples and comparative examples;

[0041] Figure 4 Performance graphs of 100 coin cycles for the embodiments and comparative examples;

[0042] Figure 5 The DSC diagrams are for the examples and comparative examples. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0044] Please see Figure 1 A method for preparing a high-nickel ternary lithium nickel cobalt manganese oxide material with doped co-coating includes the following steps:

[0045] S1, Ni, a ternary cathode material precursor x Coy Mn 1-x-y (OH)2, coarse-particle lithium carbonate is mixed with doped element K and then mixed at high speed using a star ball mill, wherein 250 r / min ≤ rotation speed ≤ 500 r / min, and 100 min ≤ mixing time ≤ 150 min;

[0046] After mixing, the material to be sintered, A, is obtained. The material to be sintered, A, is placed into the box, and the material in the box is marked with a 3-5mm wide iron sheet in a grid pattern to facilitate full contact between the material and oxygen.

[0047] In terms of molar ratio, in the ternary cathode material precursor, 0.80≤x≤0.95, 0.02≤y≤0.15, 0.02≤1-xy≤0.15, and D50≤2.5-4.5μm;

[0048] The particle size of the coarse lithium carbonate is D50 = 500-1000 μm;

[0049] The lithium ratio (Li / M) is 0.5~0.6;

[0050] The content of the dopant element K, by weight percentage, is: 15000ppm≤k≤25000ppm;

[0051] S2. Place the material A to be sintered into a box furnace for high-temperature sintering, and maintain the oxygen concentration in the furnace at ≥96% throughout the process. Increase the temperature from 25°C at 3°C / min, and hold at 500°C for 4 hours. After holding, increase the temperature at 3°C / min to 700-830°C and sinter at a constant temperature for 15 hours. Then, decrease the temperature at 5°C / min to 300°C, turn off the power, and take out the material after the material temperature drops to room temperature to obtain material B.

[0052] S3. After crushing and sieving the material B, add it to an ethanol solution at a mass ratio of 1:1.2. Add lithium according to a lithium ratio of Li / M of 0.54~0.60. After the lithium addition is completed, evaporate the solution to dryness to obtain the cathode material C to be sintered with lithium for secondary addition.

[0053] Also includes:

[0054] S4. The positive electrode material C is placed into a crucible, and lines are drawn in a grid pattern using a 3-5mm wide iron sheet to facilitate full contact between the material and oxygen. The positive electrode material C in the crucible is placed into a box furnace for high-temperature sintering, and the oxygen concentration in the furnace is maintained at ≥96% throughout the process. The temperature is increased from 25℃ at a rate of 3℃ / min, and then held at 500℃ for 4 hours. After the holding period, the temperature is increased at a rate of 3℃ / min to 800-900℃ for constant-temperature sintering for 12 hours. Then the temperature is reduced to 300℃ at a rate of 5℃ / min. The power is turned off, and the material is removed after the temperature drops to room temperature to obtain the sintered material D.

[0055] Also includes:

[0056] S5. After crushing and sieving the sintered material D, add it to an ethanol solution at a ratio of 1:1.2, add aluminum hydroxide and solid electrolyte, and stir at high speed with a stirrer. After stirring, evaporate the solution to obtain the coated material E to be sintered three times.

[0057] Also includes:

[0058] S6. Place the material E to be sintered three times, which is packed in a box, into a box furnace for high-temperature sintering. Maintain the oxygen concentration in the furnace at ≥96% throughout the process. Increase the temperature from 25℃ at 3℃ / min, raise it to 300-700℃ and hold it for 10 hours. Then, decrease the temperature to 300℃ at 5℃ / min. Turn off the power and wait for the material temperature to drop to room temperature to obtain the finished material F.

[0059] S7. The finished material F is made into button batteries and soft-pack batteries for electrical performance evaluation.

[0060] The dopant element K is composed of flux, fluoride and metal oxide, and the original crystal size of the additive is controlled at 150±50nm.

[0061] Among them, additives refer to cosolvents, fluorides, and metal oxides.

[0062] The flux is one or more selected from boric acid, boron oxide, bismuth oxide, molybdenum oxide, tungsten oxide, zinc oxide, strontium oxide, and strontium carbonate.

[0063] The fluoride is one or more of lithium fluoride, aluminum fluoride, lithium aluminum fluoride, titanium fluoride, magnesium fluoride, zirconium fluoride, lanthanum fluoride, and yttrium fluoride;

[0064] The metal oxide is one or more of the following: zirconium oxide, aluminum oxide, magnesium oxide, barium oxide, lanthanum oxide, yttrium oxide, titanium oxide, tungsten oxide, molybdenum oxide, strontium oxide, vanadium oxide, niobium oxide, and tantalum oxide.

[0065] The BET of the aluminum hydroxide is ≥80cm 2 / g;

[0066] The aluminum hydroxide is 2500~5000 ppm by weight percentage;

[0067] The solid electrolyte is one or more of LLZO, LATP, LLTO, LPS, and LGPS;

[0068] The original crystal size of the solid electrolyte is ≤150nm;

[0069] The solid electrolyte is 4000-7000 ppm by weight percentage.

[0070] Example 1:

[0071] 500g of ternary high-nickel cathode material precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2, with a D50 of 3.5 μm, is mixed with coarse-grained lithium carbonate (D50-730 μm, Li / M ratio of 0.5). 0.3 wt% boric acid, 0.3 wt% lithium fluoride, and 1.2 wt% zirconium oxide flux are added to a star-shaped ball mill. Zirconium balls are added at 1 / 3 of the material weight, with a 1:1 weight ratio of large (10 μm) to small (3 μm) zirconium balls. The mixture is then high-speed mixed at 350 r / min for 120 min. After mixing, the mixed material A is placed in a crucible, and the crucible is marked with a 3-5 mm wide iron sheet in a grid pattern to ensure sufficient contact between the material and oxygen.

[0072] The mixture was placed in a sagger and then placed in a box furnace for high-temperature sintering. The oxygen concentration in the furnace was maintained at ≥96% throughout the process. The temperature was increased from 25℃ at a rate of 3℃ / min to 500℃ and held for 4 hours. After the holding period, the temperature was increased again at a rate of 3℃ / min to 750℃ and then sintered at a constant temperature for 15 hours. After the constant temperature sintering was completed, the temperature was reduced to 300℃ at a rate of 5℃ / min. The power was turned off, and the material was taken out and crushed and sieved after the temperature of the material dropped to room temperature.

[0073] Take 200g of calcined powder and add it to an ethanol solution at a ratio of 1:1.2. Add lithium hydroxide according to the lithium ratio Li / M=0.54. Then stir the mixed solution at high speed and evaporate the alcohol to obtain the secondary lithium replenishment material.

[0074] The secondary lithium-replenishing material is loaded into a sagger and marked with a 3-5mm wide iron sheet in a grid pattern. The sagger is then placed in a box furnace for high-temperature sintering, maintaining an oxygen concentration of ≥96% throughout the process. The temperature is increased from 25℃ at a rate of 3℃ / min to 500℃ and held for 4 hours. After holding, the temperature is increased to 840℃ at a rate of 3℃ / min and sintered at a constant temperature for 12 hours. Then, the temperature is reduced to 300℃ at a rate of 5℃ / min. The power is then turned off, and the material is removed after it has cooled to room temperature to obtain the secondary sintered material.

[0075] After pulverizing and sieving 100g of the secondary calcined material, it was added to an ethanol solution at a ratio of 1:1.2, along with 0.2wt% aluminum hydroxide and 0.5wt% LATP. The mixture was stirred at high speed with a stirrer. After stirring, the solution was evaporated to dryness to obtain the coated material to be sintered a third time.

[0076] The material to be sintered three times was placed into a box furnace using a sagger for high-temperature sintering, maintaining an oxygen concentration of ≥96% throughout the process. The temperature was increased from 25℃ at a rate of 3℃ / min, reaching 400℃ and holding for 10 hours. Then, the temperature was decreased to 300℃ at a rate of 5℃ / min. The power was then turned off, and the material was allowed to cool to room temperature to obtain the finished product, LiNi. 0.83 Co 0.12 Mn 0.05 O2.

[0077] Example 2:

[0078] 500g of ternary high-nickel cathode material precursor Ni 0.90 Co 0.05 Mn 0.05 (OH)2, with a D50 of 3.5 μm, is mixed with coarse-grained lithium carbonate (D50-730 μm, Li / M ratio of 0.5). 0.3 wt% boric acid, 0.3 wt% lithium fluoride, and 1.2 wt% zirconium oxide flux are added to a star-shaped ball mill. Zirconium balls are added at 1 / 3 of the material weight, with a 1:1 weight ratio of large (10 μm) to small (3 μm) zirconium balls. The mixture is then high-speed mixed at 350 r / min for 120 min. After mixing, the mixed material A is placed in a crucible, and the crucible is marked with a 3-5 mm wide iron sheet in a grid pattern to ensure sufficient contact between the material and oxygen.

[0079] The mixture was placed in a sagger and then placed in a box furnace for high-temperature sintering. The oxygen concentration in the furnace was maintained at ≥96% throughout the process. The temperature was increased from 25℃ at a rate of 3℃ / min to 500℃ and held for 4 hours. After the holding period, the temperature was increased again at a rate of 3℃ / min to 750℃ and then sintered at a constant temperature for 15 hours. After the constant temperature sintering was completed, the temperature was reduced to 300℃ at a rate of 5℃ / min. The power was turned off, and the material was taken out and crushed and sieved after the temperature of the material dropped to room temperature.

[0080] Take 200g of calcined powder and add it to an ethanol solution at a ratio of 1:1.2. Add lithium hydroxide according to the lithium ratio Li / M=0.54. Then stir the mixed solution at high speed and evaporate the alcohol to obtain the secondary lithium replenishment material.

[0081] The secondary lithium-replenishing material is loaded into a sagger and marked with a 3-5mm wide iron sheet in a grid pattern. The sagger is then placed in a box furnace for high-temperature sintering, maintaining an oxygen concentration of ≥96% throughout the process. The temperature is increased from 25℃ at a rate of 3℃ / min to 500℃ and held for 4 hours. After holding, the temperature is increased to 810℃ at a rate of 3℃ / min and sintered at a constant temperature for 12 hours. Then, the temperature is reduced to 300℃ at a rate of 5℃ / min. The power is then turned off, and the material is removed after it has cooled to room temperature to obtain the secondary sintered material.

[0082] After pulverizing and sieving 100g of the secondary calcined material, it was added to an ethanol solution at a ratio of 1:1.2, along with 0.2wt% aluminum hydroxide and 0.5wt% LATP. The mixture was stirred at high speed with a stirrer. After stirring, the solution was evaporated to dryness to obtain the coated material to be sintered a third time.

[0083] The material to be sintered three times was placed into a box furnace using a sagger for high-temperature sintering, maintaining an oxygen concentration of ≥96% throughout the process. The temperature was increased from 25℃ at a rate of 3℃ / min, reaching 400℃ and holding for 10 hours. Then, the temperature was decreased to 300℃ at a rate of 5℃ / min. The power was then turned off, and the material was allowed to cool to room temperature to obtain the finished product, LiNi. 0.90 Co 0.05 Mn 0.05 O2.

[0084] Comparative Example 1:

[0085] 500g of ternary high-nickel cathode material precursor Ni 0.83 Co 0.12 Mn 0.05(OH)2, with a D50 of 3.5μm, is mixed with micronized lithium hydroxide (D50-15μm) at a Li / M ratio of 1.04. Zirconia (0.8wt%) is added to a star-shaped ball mill, and zirconium balls are added at 1 / 3 of the material weight, with a 1:1 weight ratio of large (10μm) to small (3μm) zirconium balls. The mixture is then mixed at high speed using a high-speed mixer at 350 r / min for 120 min. After mixing, the mixed material A is placed in a sagger, and the material in the sagger is marked in a crisscross pattern with a 3-5 mm wide iron sheet to ensure sufficient contact between the material and oxygen.

[0086] The mixture was placed in a sagger and then placed in a box furnace for high-temperature sintering. The oxygen concentration in the furnace was maintained at ≥96% throughout the process. The temperature was increased from 25℃ at a rate of 3℃ / min to 500℃ and held for 4 hours. After the holding period, the temperature was increased again at a rate of 3℃ / min to 840℃ and then sintered at a constant temperature for 12 hours. After the constant temperature sintering was completed, the temperature was reduced to 300℃ at a rate of 5℃ / min. The power was turned off, and the material was taken out and crushed and sieved after the temperature of the material dropped to room temperature.

[0087] Take 200g of the pulverized material and add it to an ethanol solution at a ratio of 1:1.2. Add 0.2wt% aluminum hydroxide and 0.5wt% LATP, and stir at high speed with a stirrer. After stirring, evaporate the solution to dryness to obtain the coated material ready for secondary sintering.

[0088] The material to be sintered a second time was placed into a box furnace using a sagger for high-temperature sintering, maintaining an oxygen concentration of ≥96% throughout the process. The temperature was increased from 25℃ at a rate of 3℃ / min, reaching 400℃ and holding for 10 hours. Then, the temperature was decreased to 300℃ at a rate of 5℃ / min. The power was then turned off, and the material was allowed to cool to room temperature to obtain the finished product, LiNi. 0.83 Co 0.12 Mn 0.05 O2.

[0089] Comparative Example 2:

[0090] 500g of ternary high-nickel cathode material precursor Ni 0.90 Co 0.05 Mn 0.05(OH)2, with a D50 of 3.5μm, is mixed with micronized lithium hydroxide (D50-15μm) at a Li / M ratio of 1.04. Zirconia (0.8wt%) is added to a star-shaped ball mill, and zirconium balls are added at 1 / 3 of the material weight, with a 1:1 weight ratio of large (10μm) to small (3μm) zirconium balls. The mixture is then mixed at high speed using a high-speed mixer at 350 r / min for 120 min. After mixing, the mixed material A is placed in a sagger, and the material in the sagger is marked in a crisscross pattern with a 3-5 mm wide iron sheet to ensure sufficient contact between the material and oxygen.

[0091] The mixture was placed in a sagger and then placed in a box furnace for high-temperature sintering. The oxygen concentration in the furnace was maintained at ≥96% throughout the process. The temperature was increased from 25℃ at a rate of 3℃ / min to 500℃ and held for 4 hours. After the holding period, the temperature was increased again at a rate of 3℃ / min to 810℃ and then sintered at a constant temperature for 12 hours. After the constant temperature sintering was completed, the temperature was reduced to 300℃ at a rate of 5℃ / min. The power was turned off, and the material was taken out and crushed and sieved after the temperature of the material dropped to room temperature.

[0092] Take 200g of the pulverized material and add it to an ethanol solution at a ratio of 1:1.2. Add 0.2wt% aluminum hydroxide and 0.5wt% LATP, and stir at high speed with a stirrer. After stirring, evaporate the solution to dryness to obtain the coated material ready for secondary sintering.

[0093] The material to be sintered a second time was placed into a box furnace using a sagger for high-temperature sintering, maintaining an oxygen concentration of ≥96% throughout the process. The temperature was increased from 25℃ at a rate of 3℃ / min, reaching 400℃ and holding for 10 hours. Then, the temperature was decreased to 300℃ at a rate of 5℃ / min. The power was then turned off, and the material was allowed to cool to room temperature to obtain the finished product, LiNi. 0.90 Co 0.05 Mn 0.05 O2.

[0094] Coarse-grained lithium carbonate: Due to the higher reaction temperature, coarse-grained lithium carbonate further slows down the diffusion rate of lithium ions, which helps dopants preferentially enter the ternary cathode material lattice, reduces the segregation and agglomeration of additives, and makes the additives in the ternary cathode material more uniformly distributed. This is especially important for the structural stability of the ternary cathode material under high-voltage application scenarios. Fluorides: Provide anion F- doping, forming FO bond energy with lattice oxygen, reducing the release of lattice oxygen under high voltage conditions, increasing the thermal failure temperature of the ternary cathode material, and improving high-temperature performance. Metal oxides: Metal elements are doped into the lattice, forming a "pillar ion" effect inside the lattice, widening the lithium ion transport path, suppressing the phase transition of the ternary cathode material, enhancing the structural strength of the cathode material, and improving the stability of the ternary cathode material under high voltage and high delithiation conditions.

[0095] Results analysis:

[0096] Depend on Figure 2 (a) As can be seen in Example 1, the finished product material LiNi 0.83 Co 0.12 Mn 0.05 In the SEM image of O2, the particles are uniform in size and distribution.

[0097] Depend on Figure 2 (b) As can be seen from the finished product LiNi in Comparative Example 1 0.83 Co 0.12 Mn 0.05 In the SEM image of O2, the grains are relatively aggregated, with no obvious grain boundaries, and the surface coating layer is obviously aggregated and unevenly distributed.

[0098] Depend on Figure 2 (c) As can be seen in Example 2, the finished product material LiNi 0.90 Co 0.05 Mn 0.05 In the SEM image of O2, the particles are uniform in size and distribution.

[0099] Depend on Figure 2 (d) As can be seen from the finished product LiNi in Comparative Example 2 0.90 Co 0.05 Mn 0.05 In the SEM image of O2, the grains are of different sizes and are relatively aggregated, with no obvious grain boundaries, and the surface coating layer is obviously aggregated and unevenly distributed.

[0100] Depend on Figure 3As shown in the coin cell rate performance diagram for voltages ranging from 3.0V to 4.4V, the capacity exhibited by the material at a 0.1C discharge rate is similar between the comparative and example examples. With increasing rate performance, the lithium-ion diffusion rate accelerates, and the lattice distortion increases. Examples 1 and 2, due to their more uniform internal doping and higher structural strength, achieved 1C rate capacities of 201 and 209 mAh / g, respectively (capacity retention rates of 92.2% and 92.07% compared to 0.1C discharge). In contrast, the comparative examples, due to fewer doped elements and increased lattice stress caused by dopant segregation, achieved 1C rate capacities of 63 and 37 mAh / g, respectively (capacity retention rates of 28.7% and 16.16% compared to 0.1C discharge).

[0101] Depend on Figure 4 It can be seen that when the voltage is 3.0V~4.4V, during 1C discharge, Examples 1 and 2, due to their uniform surface coating, suppressed the surface erosion of the positive electrode material by the electrolyte, and the capacity retention rate could still reach about 99% after 100 cycles. Comparative Examples 1 and 2, due to internal doping segregation and uneven surface coating, experienced collapse of the internal structure of the positive electrode material under continuous charge and discharge at 4.4V, and the surface was eroded and failed by the electrolyte, resulting in a rapid decrease in capacity retention rate. After 100 cycles, the capacity retention rate of Comparative Example 1 was 53.05%, while that of Comparative Example 2 was only 11.54%.

[0102] Depend on Figure 5 It can be seen that when the voltage is 3.0V~4.4V, the electrode is subjected to DSC thermal failure test after 0.1C, 100% DOD discharge. Due to the large number of doped elements in Examples 1 and 2 and their uniform distribution inside, the bond energy (MO) with the lattice oxygen is increased, which significantly enhances the structural strength of the lattice and increases the thermal stability of the material. The DSC peak temperatures of Examples 1 and 2 are 239 and 222℃, respectively; while the DSC peak temperatures of Comparative Examples 1 and 2 are 219 and 198℃, respectively. Under the same nickel-cobalt-manganese conditions, the peak temperatures of DSC differ by about 20℃.

[0103] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be defined by the appended claims.

Claims

1. A method for preparing a high-nickel ternary lithium nickel cobalt manganese oxide material with doped and co-coated structure, characterized in that, Includes the following steps: S1, Ni, a ternary cathode material precursor x Co y Mn 1-x-y (OH)2, coarse-particle lithium carbonate is mixed with doped element K and then mixed at high speed using a star ball mill, wherein 250 r / min ≤ rotation speed ≤ 500 r / min, and 100 min ≤ mixing time ≤ 150 min; After mixing, the material to be sintered, A, is obtained. The material to be sintered, A, is placed into the box, and the material in the box is marked with a 3-5mm wide iron sheet in a grid pattern to facilitate full contact between the material and oxygen. In terms of molar ratio, in the ternary cathode material precursor, 0.80≤x≤0.95, 0.02≤y≤0.15, 0.02≤1-xy≤0.15, and 2.5≤D50≤4.5μm; The particle size of the coarse lithium carbonate is D50 = 500-1000 μm; The lithium ratio (Li / M) is 0.5~0.6; The content of the dopant element K, by weight percentage, is: 15000ppm≤k≤25000ppm; S2. Place the material A to be sintered into a box furnace for high-temperature sintering, and maintain the oxygen concentration in the furnace at ≥96% throughout the process. Increase the temperature from 25°C at 3°C / min, and hold at 500°C for 4 hours. After holding, increase the temperature at 3°C / min to 700-830°C and sinter at a constant temperature for 15 hours. Then, decrease the temperature at 5°C / min to 300°C, turn off the power, and take out the material after the material temperature drops to room temperature to obtain material B. S3. After crushing and sieving the material B, add it to the ethanol solution at a mass ratio of 1:1.2, and add lithium according to the lithium ratio Li / M of 0.54~0.

60. After the lithium addition is completed, evaporate the solution to dryness to obtain the positive electrode material C to be sintered with lithium for the second time. Also includes: S4. The positive electrode material C is placed into a sagger, and lines are drawn in a grid pattern using a 3-5mm wide iron sheet to facilitate full contact between the material and oxygen. The positive electrode material C in the sagger is placed into a box furnace for high-temperature sintering, and the oxygen concentration in the furnace is maintained at ≥96% throughout the process. The temperature is increased from 25℃ at a rate of 3℃ / min, and then held at 500℃ for 4 hours. After the holding period, the temperature is increased at a rate of 3℃ / min to 800-900℃ for constant-temperature sintering for 12 hours. Then the temperature is reduced to 300℃ at a rate of 5℃ / min. The power is turned off, and the material is removed after the temperature drops to room temperature to obtain the sintered material D. Also includes: S5. After crushing and sieving the sintered material D, add it to an ethanol solution at a ratio of 1:1.2, add aluminum hydroxide and solid electrolyte, and stir at high speed with a stirrer. After stirring, evaporate the solution to obtain the coated material E to be sintered three times. Also includes: S6. Place the material E to be sintered three times, which is packed in a box, into a box furnace for high-temperature sintering. Maintain the oxygen concentration in the furnace at ≥96% throughout the process. Increase the temperature from 25℃ at 3℃ / min, raise it to 300-700℃ and hold it for 10 hours. Then, decrease the temperature to 300℃ at 5℃ / min. Turn off the power and wait for the material temperature to drop to room temperature to obtain the finished material F. S7. The finished material F is made into button batteries and soft-pack batteries for electrical performance evaluation.

2. The method for preparing a high-nickel ternary lithium nickel cobalt manganese oxide material with doped co-coating according to claim 1, characterized in that: The dopant element K is composed of flux, fluoride and metal oxide, and the original crystal size of the additive is controlled at 150±50nm. The flux is one or more selected from boric acid, boron oxide, bismuth oxide, molybdenum oxide, tungsten oxide, zinc oxide, strontium oxide, and strontium carbonate. The fluoride is one or more of lithium fluoride, aluminum fluoride, lithium aluminum fluoride, titanium fluoride, magnesium fluoride, zirconium fluoride, lanthanum fluoride, and yttrium fluoride; The metal oxide is one or more of the following: zirconium oxide, aluminum oxide, magnesium oxide, barium oxide, lanthanum oxide, yttrium oxide, titanium oxide, tungsten oxide, molybdenum oxide, strontium oxide, vanadium oxide, niobium oxide, and tantalum oxide.

3. The method for preparing a high-nickel ternary lithium nickel cobalt manganese oxide material with doping and co-coating according to claim 2, characterized in that: The BET of the aluminum hydroxide is ≥80cm 2 / g; The aluminum hydroxide is 2500~5000 ppm by weight percentage; The solid electrolyte is one or more of LLZO, LATP, LLTO, LPS, and LGPS; The original crystal size of the solid electrolyte is ≤150nm; The solid electrolyte is 4000-7000 ppm by weight percentage.

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