Preparation method of doped and co-coated high-nickel ternary nickel cobalt lithium manganate material

Abstract

The invention provides a preparation method of a doped and co-coated high-nickel ternary nickel cobalt lithium manganate material, which comprises the following steps: mixing a ternary positive electrode material precursor NixCoyMn1-x-y (OH) 2, coarse particle lithium carbonate and a doping element K, and carrying out high-speed mixing by using a star ball mill, with the rotating speed being greater than or equal to 250 r / min and less than or equal to 500 r / min, and the mixing time being greater than or equal to 100 min and less than or equal to 150 min; a to-be-sintered material A is obtained after mixing is completed, the to-be-sintered material A is put into a box body, and the material in the box body is marked by an iron sheet with the width of 3-5 mm according to a # shape, so that sufficient contact between the material and oxygen is facilitated, the problem of element segregation of multi-element synergistic doping can be solved, and under the condition of high cut-off voltage, the sintering temperature is lowered, and the sintering time is shortened. And the high-nickel ternary positive electrode material with excellent performance is obtained.

Description

TECHNICAL FIELD

[0001] The application relates to the field of high-voltage lithium ion battery positive electrode materials, in particular to a preparation method of a high-nickel ternary lithium nickel cobalt manganese oxide material doped with co-coating. BACKGROUND

[0002] In recent years, lithium ion batteries have been widely used in the fields of electric vehicles, consumer electronics, electric tools and the like due to their advantages of high energy density, high working voltage, small size and no memory effect. With the increasing improvement of the national living standard, the application scenarios of lithium ion batteries are becoming more and more rich, such as the fields of low-altitude economy, unmanned aerial vehicles, aerospace and the like, and higher and higher index requirements for the energy density of lithium ion batteries are put forward. At present, the lithium ion positive electrode materials mainly include lithium cobaltate, lithium iron phosphate and ternary positive electrode materials. The ternary positive electrode materials can be divided into NCM and NCA materials (Ni / Co / Mn, Ni / Co / Al) according to the different main contents, and can be divided into polycrystal and single crystal positive electrode materials according to the different micro-morphologies. The polycrystal positive electrode material is generally formed by agglomeration of primary particles with a primary particle size of 300-1000 nm, and the capacity of the polycrystal positive electrode material is generally high, and the rate performance is good. The single crystal positive electrode material is composed of single crystal particles with a primary particle size of about 1-5 microns, the grain boundaries between the particles are obvious, the structural stability is high, and the resistance to high cut-off voltage is good. Because the ternary positive electrode material has the advantages of high specific capacity, easy processing and low cost, it has gradually become a research hotspot of lithium ion battery positive electrode materials. In recent years, in order to meet the increasing demand for high energy density of lithium ion batteries, the positive electrode material is developing in two directions: ① high nickelization. In the ternary positive electrode material, Ni element mainly participates in the redox reaction. The higher the content of nickel, the more the provided redox couple, according to the theoretical capacity calculation formula of active material: C0=m / MxNe x 26.8A•h=(m / K)•C, the more the capacity released, so increasing the proportion of nickel content in the ternary material can effectively improve the capacity of the ternary positive electrode material; ② improving the cut-off voltage of lithium battery in use. According to the energy density formula: W=EV, increasing the cut-off voltage V of the lithium ion battery can release more lithium ions, which can improve the capacity of the positive electrode material. However, with the increase of the cut-off voltage, a large amount of Ni 2+ , Ni 3+ loses electrons to convert into a large amount of Ni 4+ , Ni 4+ has strong oxidizing property and is easy to react with lattice oxygen, resulting in the loss of electrons of the lattice oxygen to convert into oxygen gas, causing the structure of the material to collapse and releasing a large amount of heat, which causes the material to be out of control and leads to poor safety performance of the lithium battery, and even a major safety accident. This phenomenon is more and more serious with the increase of the nickel content in the ternary positive electrode material.

[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. 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.

[0004] 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.

[0005] 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

[0006] 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. To achieve the above objectives, the present invention adopts the following technical solution: 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: 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 D50≤2.5-4.5μm; 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 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.

[0007] Furthermore, it also includes: S4, load the positive electrode material C into a sagger, mark a well-shaped line with an iron sheet of 3-5 mm wide to facilitate the full contact between the material and oxygen; put the sagger-loaded positive electrode material C into a box furnace for high-temperature sintering, maintain the oxygen concentration in the furnace at ≥96% throughout the process, heat from 25℃ at a rate of 3℃ / min, heat to 500℃ and keep for 4h, after the end of the heat preservation, heat to 800-900℃ at a rate of 3℃ / min for constant temperature sintering for 12h, then cool down at a rate of 5℃ / min to 300℃, turn off the power, and take out the sintered material D after the material temperature drops to room temperature.

[0008] Further, it further comprises: S5, after crushing and sieving the sintered material D, add it into an ethanol solution at a ratio of 1:1.2, add aluminum hydroxide and solid electrolyte, and stir at high speed with a stirrer, then evaporate the solution to obtain the coated material E ready for the third sintering.

[0009] Further, it further comprises: S6, put the sagger-loaded material E ready for the third sintering into a box furnace for high-temperature sintering, maintain the oxygen concentration in the furnace at ≥96% throughout the process, heat from 25℃ at a rate of 3℃ / min, heat to 300-700℃ and keep for 10h, cool down at a rate of 5℃ / min to 300℃, turn off the power, and obtain the finished product F after the material temperature drops to room temperature; S7, make the finished product F into button cells and soft package batteries for electrical performance evaluation.

[0010] Further, the doping element K is composed of fluxing agent, fluoride and metal oxide, and the original crystal size of the additive is controlled at 150±50nm; The fluxing agent is one or more of boric acid, boric 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 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.

[0011] Further, the BET of the aluminum hydroxide is ≥80cm 2 / g; The aluminum hydroxide is 2500-5000ppm in 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.

[0012] 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

[0013] Figure 1 A flowchart of a method for preparing a high-nickel ternary lithium nickel cobalt manganese oxide material with doped co-coating; Figure 2 (a) is a SEM image of Example 1; Figure 2 (b) is the SEM image of Comparative Example 1; Figure 2 (c) is a SEM image of Example 2; Figure 2 (d) is the SEM image of Comparative Example 2; Figure 3 The coin charge rate performance diagrams are for the examples and comparative examples; Figure 4 Performance graphs of 100 coin cycles for the embodiments and comparative examples; Figure 5 The DSC diagrams are for the examples and comparative examples. Detailed Implementation

[0014] 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.

[0015] 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: 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 the ternary positive electrode material precursor, 0.80≤x≤0.95, 0.02≤y≤0.15, 0.02≤1-x-y≤0.15, and D50≤2.5-4.5 μm in terms of molar ratio; The particle size D50 of the coarse-grained lithium carbonate is 500-1000 μm. The lithium ratio Li / M is 0.5-0.6. The content of the doping element K is 15000-25000 ppm in terms of weight percentage. S2, the sintering material A is put into a box furnace for high-temperature sintering, and the oxygen concentration in the furnace is kept ≥96% throughout the process, the temperature is raised from 25°C at a rate of 3°C / min, and then raised to 500°C for 4h, after the end of the heat preservation, raised to 700-830°C at a rate of 3°C / min for constant temperature sintering for 15h, then cooled to 300°C at a rate of 5°C / min, the power is turned off, and the material is taken out after the temperature drops to room temperature to obtain material B. S3, the material B is crushed and sieved, then added into ethanol solution at a mass ratio of 1:1.2, the lithium ratio Li / M is 0.54-0.60, after lithium supplementation, the solution is evaporated to obtain the positive electrode material C for secondary lithium sintering.

[0016] Further comprising: S4, the positive electrode material C is loaded into a sagger, and an iron sheet with a width of 3-5 mm is used to draw a cross-shaped line to facilitate the contact between the material and oxygen, the positive electrode material C loaded in the sagger is put into a box furnace for high-temperature sintering, and the oxygen concentration in the furnace is kept ≥96% throughout the process, the temperature is raised from 25°C at a rate of 3°C / min, and then raised to 500°C for 4h, after the end of the heat preservation, raised to 800-900°C at a rate of 3°C / min for constant temperature sintering for 12h, then cooled to 300°C at a rate of 5°C / min, the power is turned off, and the material is taken out after the temperature drops to room temperature to obtain the sintered material D.

[0017] Further comprising: S5, the sintered material D is crushed and sieved, then added into ethanol solution at a ratio of 1:1.2, aluminum hydroxide and solid electrolyte are added, and a stirrer is used for high-speed stirring, after stirring, the solution is evaporated to obtain the coated material E for third sintering.

[0018] Further comprising: S6, the three sintering material E is put into the box furnace, and the oxygen concentration in the furnace is kept at 96% or more, the temperature is raised from 25 DEG C at a rate of 3 DEG C / min, and the temperature is kept at 300-700 DEG C for 10h, and then the temperature is lowered to 300 DEG C at a rate of 5 DEG C / min, the power is turned off, and the finished product F is obtained after the material temperature is reduced to room temperature; S7, the finished product F is made into a buckle and a soft package battery for electrical performance evaluation.

[0019] The doping element K is composed of fluxing agent, fluoride and metal element oxide, and the original crystal size of the additive is controlled at 150±50nm; Among them, the additive refers to the cosolvent, fluoride and metal oxide.

[0020] The fluxing agent is one or more of 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 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.

[0021] The BET of the aluminum hydroxide is greater than or equal to 80cm 2 / g; The aluminum hydroxide is 2500-5000ppm in 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 less than or equal to 150nm; The solid electrolyte is 4000-7000ppm in weight percentage.

[0022] Example one:

[0023] 500g of ternary high-nickel positive 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. 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. 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. 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. 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. 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.

[0024] Example 2:

[0025] 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. 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. 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. 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. 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. 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.

[0026] Comparative Example 1: 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. 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. 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. 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.

[0027] Comparative Example 2: 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. 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. 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. 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.

[0028] Coated with metal oxide: the metal elements doped into the crystal lattice form a "column ion" effect, which widens the transmission path of lithium ions, inhibits the phase change of the ternary cathode material, enhances the structural strength of the cathode material, and improves the stability of the ternary cathode material under high-voltage and high-lithium extraction conditions.

[0029] Result analysis: By Figure 2 (a) It can be seen from the SEM image of the finished material LiNi 0.83 Co 0.12 Mn 0.05 O2 in Example 1 that the particle size is uniform, and the particle distribution is uniform; By Figure 2 (b) It can be seen from the SEM image of the finished material LiNi 0.83 Co 0.12 Mn 0.05 O2 in Comparative Example 1 that the crystal grains are agglomerated, there is no obvious grain boundary, and the surface coating layer is obviously agglomerated and unevenly distributed; By Figure 2 (c) It can be seen from the SEM image of the finished material LiNi 0.90 Co 0.05 Mn 0.05 O2 in Example 2 that the particle size is uniform, and the particle distribution is uniform; By Figure 2 (d) It can be seen from the SEM image of the finished material LiNi 0.90 Co 0.05 Mn 0.05 O2 in Comparative Example 2 that the crystal grains are of different sizes and are agglomerated, there is no obvious grain boundary, and the surface coating layer is obviously agglomerated and unevenly distributed; By Figure 3It can be seen that the voltage is 3.0V~4.4V, and the discharge rate performance diagram can be known. When discharging at 0.1C rate, the capacity of the material is small, and the difference between the comparative example and the embodiment is small. With the increase of rate performance, the lithium ion diffusion speed is accelerated, and the lattice distortion amplitude is increased. The internal doping of the first and second embodiments is more uniform, and the structural strength is higher. The 1C rate capacity of the first and second embodiments is 201, 209mAh / g (compared with 0.1C rate discharge, the capacity retention rate is 92.2, 92.07%), and the comparative example has less doping coating elements, and the segregation of the doping elements increases the internal stress of the lattice. The 1C rate capacity of the first and second comparative examples is 63, 37mAh / g (compared with 0.1C rate discharge, the capacity retention rate is 28.7, 16.16%) By Figure 4 It can be seen that when the voltage is 3.0V~4.4V, the discharge at 1C, the first and second embodiments have uniform surface coating, which inhibits the surface erosion of the electrolyte to the positive electrode material. After 100 cycles, the capacity retention rate can still reach about 99%. The first and second comparative examples have internal doping segregation and uneven surface coating. Under the condition of continuous charging and discharging at 4.4V voltage, the internal structure of the positive electrode material collapses, the surface is eroded by the electrolyte, and the capacity retention rate decreases rapidly. The capacity retention rate of the first comparative example is 53.05%, and the capacity retention rate of the second comparative example is only 11.54% By Figure 5 It can be seen that when the voltage is 3.0V~4.4V, the DSC thermal failure test of the pole piece is carried out after 0.1C, 100%DOD discharge. Since the first and second embodiments have more internal doping elements and are uniformly distributed inside, the bond energy (M-O) with the lattice oxygen is increased, the structural strength of the lattice is obviously enhanced, and the thermal stability of the material is increased. The DSC peak temperature of the first and second embodiments is 239, 222℃; and the DSC peak temperature of the first and second comparative examples is 219, 198℃. Under the same nickel-cobalt-manganese condition, the peak temperature of DSC is about 20℃.

[0030] The above-described embodiments only express the implementation of the present application, which is described in detail and specifically, but it cannot be understood as a limitation on the scope of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the protection scope of the present application patent should be based on the appended claims.

Claims

1. A method for preparing a doped co-coated high-nickel ternary lithium nickel cobalt manganese oxide material, characterized in that, Includes the following steps: S1, mixing the ternary cathode material precursor Ni x Co y Mn 1-x-y (OH)2, coarse-grained lithium carbonate with doping element K, and high-speed mixing with a star-shaped ball mill, wherein 250 r / min≤rotational speed≤500 r / min, 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 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.

2. The preparation method of the doped co-coated high-nickel ternary lithium nickel-cobalt-manganese oxide material according to claim 1, characterized in that, Also includes: 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.

3. The preparation method of the doped co-coated high-nickel ternary lithium nickel-cobalt-manganese oxide material according to claim 2, characterized in that, 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.

4. The preparation method of the doped co-coated high-nickel ternary lithium nickel-cobalt-manganese oxide material according to claim 3, characterized in that, 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.

5. The preparation method of the doped co-coated high-nickel ternary lithium nickel-cobalt-manganese oxide material according to claim 1, characterized by: 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 fluxing agent is one or more of boric acid, boric oxide, bismuth oxide, molybdenum oxide, tungsten oxide, zinc oxide, strontium oxide, strontium carbonate; The fluoride is one or more of lithium fluoride, aluminum fluoride, lithium aluminum fluoride, titanium fluoride, magnesium fluoride, zirconium fluoride, lanthanum fluoride, yttrium fluoride; The metal oxide is one or more of zirconium oxide, aluminum oxide, magnesium oxide, barium oxide, lanthanum oxide, yttrium oxide, titanium oxide, tungsten oxide, molybdenum oxide, strontium oxide, vanadium oxide, niobium oxide, tantalum oxide.

6. The preparation method of the doped co-coated high-nickel ternary lithium nickel-cobalt-manganese oxide material according to claim 3, characterized by: The aluminum hydroxide has a BET > 80 cm 2 / g; The aluminum hydroxide is 2500-5000 ppm in terms of weight percentage; The solid-state electrolyte is one or more of LLZO, LATP, LLTO, LPS, LGPS; The original crystal size of the solid-state electrolyte is ≤150 nm; The solid-state electrolyte is 4000-7000 ppm in terms of weight percentage.

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