CN109728277A - Method, product and battery for surface treatment of high nickel ternary cathode material - Google Patents

Abstract

The invention discloses a kind of method being surface-treated to nickelic tertiary cathode material and products and battery.The surface treatment method of the nickelic tertiary cathode material are as follows: using polyacrylic acid solution as covering liquid, nickelic tertiary cathode material is placed in covering liquid and is stirred certain time, it takes out, it is dry, the nickelic tertiary cathode material powder of gained polyacrylic acid cladding is heat-treated to arrive carbon-coated nickelic tertiary cathode material in oxidizing atmosphere.Nickelic tertiary cathode material is surface-treated using this method, nickelic tertiary cathode powder surface alkalinty can not only be removed, so that being not in that slurry becomes gelatin phenomenon when by resulting materials (- 30 DEG C of dew point) progress slurrying under normal condition, moreover it is possible to guarantee that the charge/discharge capacity of resulting materials is not suffered a loss.

Description

Method, product and battery for surface treatment of high nickel ternary cathode material

technical field

The invention relates to a method, a product and a battery for surface treatment of a high-nickel ternary positive electrode material, and belongs to the technical field of battery materials.

Background technique

Lithium ion batteries use materials capable of reversible intercalation and deintercalation of lithium ions as the positive electrode material and negative electrode material of the battery, combined with an appropriate electrolyte or solid electrolyte powder film to form a lithium ion secondary battery system. Because the energy of a battery depends on the product of its voltage and capacity, the means to improve the energy density of the battery is to use high-voltage and high-capacity positive and negative electrode materials. For the same negative electrode material, the higher the capacity and potential of the positive electrode material, the higher the energy density of the battery. Improving the energy density of lithium-ion batteries and developing ternary cathode powders with higher specific capacity and high nickel content are the main directions of battery research and development.

Compared with the spinel structure lithium manganate and the olivine structure lithium iron phosphate with low theoretical specific capacity (theoretical specific capacity is 170mAh/g), the layered structure ternary composite cathode material with theoretical specific capacity of 280mAh/g ( LiNi _x Co _y M _(1-xy) O ₂ , 0≤x<1, 0<y<1, and 0<x+y<1, M is Mn or Al) has obvious advantages, and the layered structure three The actual capacity of the element cathode in the lithium-ion battery will increase with the increase of the Ni content. Therefore, the ternary composite cathode material with the nickel element ratio higher than 60% is the preferred cathode for the current high-energy density lithium-ion battery.

High-nickel ternary cathode powder is usually synthesized by co-precipitation-high temperature solid-phase reaction, that is, the ternary hydroxide precursor is prepared by co-precipitation method, and then a lithium source such as lithium hydroxide or lithium carbonate is added to mix and sinter. The ternary positive electrode powder is made. It is well known that the morphology and particle size of the precursor powder in the co-precipitation-high temperature solid-phase reaction process affect many properties of the cathode powder in lithium-ion batteries. An efficient approach to cathode powder performance. Existing studies have shown that the coating layer can alleviate the corrosion of the electrolyte on the surface of the high nickel nickel cobalt manganese ternary cathode powder, and the doping element can also inhibit the crystal structure change of the surface part of the ternary cathode powder and improve the cycle of the ternary material. Stability and thermal stability.

There have been many studies on the use of metal oxides to coat nickel cobalt lithium manganate ternary cathode powder to improve its electrochemical stability. For example, the invention patent publication number CN104393277A discloses a lithium A method for preparing a ternary positive electrode material for an ion battery, the method comprising: (1) adding a soluble metal salt to a solution in which a polymer polyacrylamide is used as a dispersant for uniform dispersion; (2) adding a ternary positive electrode material powder to the above solution, stirring and mixing; ③ Add an aqueous solution of alkali metal hydroxide to the mixed solution, adjust the pH value of the solution to 9-12, filter after precipitation, and dry to obtain a positive electrode material coated with hydroxide; ④ Then coat the surface with hydroxide The positive electrode material of the metal oxide is heat treated at 400-700° C. to obtain a ternary positive electrode material whose surface is coated with metal oxide. Another example is the invention patent whose publication number is CN108777296A, which discloses a method for forming a surface modification layer of a high-nickel ternary positive electrode material. The inner core of the high-nickel ternary positive electrode material is coated with two kinds of surface modification substances, one of which is Yttrium oxide stabilized zirconia, another one selected from metal oxides, metal fluorides, metal phosphates or C, the surface modification substance is coated on the surface of the bulk material, reducing the side reaction between the high nickel ternary positive electrode material and the electrolyte , the irreversible capacity loss of the ternary cathode material is suppressed. Another example is the invention patent whose publication number is CN105576233A, which discloses a method for modifying the surface of a nickel-based ternary positive electrode material. , using one or more of a titanate coupling agent, an aluminate coupling agent and a silane coupling agent to react and compound in an organic solvent, calcined and heat-treated to obtain titanium, aluminum or silicon oxide coating modification The nickel-based ternary cathode material. Although similar metal oxide coating modification treatments can improve the cycle performance and thermal stability of the cathode powder to a certain extent, it also brings negative effects, because the coated metal oxide is an inert material, which inhibits lithium Transport of ions and electrons.

On the other hand, there is also a method for improving the electrical conductivity of ternary positive electrode material powder by carbon coating, such as the invention patent with publication number CN103474628A, the disclosed method for improving ternary positive electrode material powder by carbon coating includes: 1. Nickel salt, cobalt salt and manganese salt as raw materials to prepare ternary cathode material precursor; ② disperse conductive carbon in water containing organic carbon source to prepare conductive carbon dispersion; ③ add ternary cathode material precursor and lithium compound into conductive carbon dispersion , to obtain a uniform mixture; 4. drying the mixture under vacuum conditions; The invention points out that the rate performance of the ternary positive electrode material can be improved by simultaneously coating the conductive carbon powder and the ternary positive electrode material in the network-like conductive medium amorphous carbon. The invention patent with publication number CN104733721A discloses a method for preparing a nickel-cobalt lithium manganate ternary positive electrode material by liquid-phase sugar coating and spray drying. The ternary composite precursor (Ni _x Co _y Mn _z )(OH) ₂ is obtained by precipitation, after filtering, washing and drying, it is added together with soluble metal lithium compound and rare earth compound into the solvent in which sugar is dissolved, and then mixed uniformly. A ternary precursor coated with sugar and doped with rare earth elements is obtained by spray drying, and finally, a carbon-containing layer and a ternary material LiNi _x Co _y Mn _z RnO ₂ powder doped with rare earth elements are obtained by high temperature calcination.

In addition, the invention patent with publication number CN107895793A discloses a preparation method of a lithium battery positive electrode material coated with tungsten doped boride on the surface, specifically dissolving a tungsten source in water, spraying the ternary precursor and the ternary precursor by spraying. Stirring the lithium source mixed raw materials to obtain dry materials, and then roasting to obtain a tungsten-doped ternary positive electrode material; then adding metal boride to the above-mentioned tungsten-doped ternary positive electrode material, stirring evenly, and then sintering at a certain temperature to obtain a tungsten-doped ternary positive electrode material Boride-coated cathode material for lithium batteries.

However, as known to those skilled in the art, the surface of the high-nickel ternary cathode powder is alkaline. If it is directly applied to the subsequent slurry mixing process, pulping under normal conditions (dew point -30°C) will lead to slurry The problem that the material becomes gel (jelly-like colloid); if you want to remove the alkalinity of the surface of the ternary positive electrode powder, although the operation of water washing can be used, this will cause the loss of lithium ions on the surface and cause the discharge capacity of the ternary positive electrode material to decrease. . The above-mentioned various ternary positive electrode powder surface coating or doping treatment methods do not mention solutions based on this problem. Therefore, it is necessary to provide a method to effectively remove the surface alkalinity of high-nickel ternary positive electrode powder, so that in the A method for surface treatment of high-nickel ternary cathode materials without causing the slurry to become gel when it is pulped under normal conditions (dew point -30 ° C), and without causing the loss of charge and discharge capacity of the obtained material .

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a method, product and battery for surface treatment of a high-nickel ternary positive electrode material. The surface treatment of the high-nickel ternary positive electrode material by this method can not only remove the surface alkalinity of the high-nickel ternary positive electrode powder, but also prevent the slurry from changing when the obtained material is slurried under normal conditions (dew point -30°C). At the same time of gelation phenomenon, it can also ensure that the charge-discharge capacity of the obtained material is not lost.

In order to solve the above-mentioned technical problems, the method for surface treatment of a high-nickel ternary positive electrode material according to the present invention is characterized in that: a polyacrylic acid solution is used as a coating liquid, and the high-nickel ternary positive electrode material is placed in the coating liquid Stir and mix for a certain period of time, take out, and dry to obtain polyacrylic acid-coated high-nickel ternary positive electrode material powder; then place the obtained polyacrylic acid-coated high-nickel ternary positive electrode material powder in an oxidizing atmosphere for heat treatment to obtain a carbon coating Coated high-nickel ternary positive electrode material; wherein, the high-nickel ternary positive electrode material is LiNi _x Co _y M _(1-xy) O ₂ , 0.6≤x<1, 0<y<0.4, and 0<x +y<1, M is Mn or Al.

In the surface treatment method of the present invention, the polyacrylic acid solution is obtained by dissolving polymer polyacrylic acid in a polar aprotic solvent, preferably a polyacrylic acid solution with a solid content of 0.001-0.005% (mass, the same below). The polar aprotic solvent is the same as the prior art, and can be specifically selected from N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF), N-methyl- One or a combination of any two or more of 2-pyrrolidone (NMP), N,N-diethylacetamide and N,N-diethylformamide.

In the surface treatment method of the present invention, the high-nickel ternary positive electrode material powder is placed in the polyacrylic acid solution under low moisture conditions (such as dew point -30° C.) and stirred and mixed for a certain period of time to make the two fully contact, because the polyacrylic acid solution It has a certain viscosity. On the one hand, stirring and mixing makes the weakly acidic polyacrylic acid solution react with the high-nickel ternary cathode material powder with an alkaline surface, and on the other hand, it also realizes that the polyacrylic acid solution has an alkaline surface. Coating of material powder. The material-to-liquid ratio of the high-nickel ternary positive electrode material powder and the polyacrylic acid solution can be designed as required. When the polyacrylic acid solution is a polyacrylic acid solution with a solid content of 0.001-0.005%, the high-nickel ternary positive electrode material powder The solid-liquid ratio with the polyacrylic acid solution can be 1:1-10, more preferably 1:1-3. The time for stirring and mixing is usually ≥ 0.1 h, more preferably 0.5-3 h, and more preferably 1-3 h. In this step, the drying is usually carried out at 120-200°C.

In the surface treatment method of the present invention, the heat treatment is to keep the temperature at 600-700° C. for 3-8 hours.

The high-nickel ternary positive electrode material involved in the surface treatment method of the present invention can be a commercially available conventional product, or can be prepared by itself. For example, it can be prepared according to the existing conventional co-precipitation-high-temperature solid-phase reaction synthesis. method to prepare:

1) According to the chemical formula LiNi _x Co _y M _(1-xy) O ₂ (0.6≤x<1, 0<y<0.4, and 0<x+y<1, M is Mn or Al), weigh the nickel salt, Cobalt salt and manganese salt or aluminum salt are dissolved in water to obtain a first mixed solution, and the concentration of total metal ions in the first mixed solution is controlled to be 2mol/L; a precipitating agent and a complexing agent are added to the first mixed solution for co-precipitation Reaction, in the whole co-precipitation reaction process, the consumption of the precipitant is the pH=10-13 of the control system, after the reaction is completed, the obtained reaction material is filtered, and the precipitation is collected and dried to obtain the high nickel ternary hydroxide precursor (nickel-cobalt). manganese hydroxide precursor or nickel cobalt aluminum hydroxide precursor);

2) Mixing the high-nickel ternary hydroxide precursor and the lithium source uniformly, and performing heat treatment in an oxidizing atmosphere to obtain a high-nickel ternary positive electrode material.

In the above-mentioned step 1), the selection of the nickel salt, cobalt salt, manganese salt and aluminum salt is the same as the prior art, and specifically, the nickel salt can be one or both of nickel sulfate, nickel nitrate and nickel chloride The above combination, the cobalt salt can be a combination of one or more of cobalt sulfate, cobalt nitrate and cobalt chloride, and the manganese salt can be one or more of manganese sulfate, manganese nitrate and manganese chloride. In combination, the aluminum salt can be one or a combination of two or more of aluminum sulfate, aluminum nitrate and aluminum chloride. In the whole co-precipitation reaction process, the dosage of the precipitant is pH=10.5-11.5 of the control system; the selection of the precipitant is the same as that in the prior art, and it can be a sodium hydroxide solution with a concentration of 1-5mol/L or Potassium hydroxide solution, etc. The selection of the complexing agent is the same as that in the prior art. Usually, when the concentration is 25% (the mass fraction of NH is ₂₅ %, the same below), the addition amount is 10-50 mL per liter of the first mixed solution. Complexing agent calculation.

In the above-mentioned step 2), the lithium source is a conventional choice in the prior art, and specifically can be lithium hydroxide and/or lithium carbonate, etc., and the amount of the lithium source is required by the high nickel ternary positive electrode material to be prepared. The theoretical batching amount is usually 1.01-1.1 times the theoretical amount in the actual operation process. The high-nickel ternary hydroxide precursor and the lithium source are uniformly mixed by using an existing conventional mechanical mixing method, such as a drum-type high-speed mixer or a ball mill, etc. for mixing. The heat treatment after mixing uniformly is to complete the lithiation reaction.

The present invention also includes the carbon-coated high-nickel ternary positive electrode material obtained by the above method.

The present invention also provides a lithium ion battery, comprising a positive electrode sheet, and the positive electrode material used on the positive electrode sheet is a carbon-coated high-nickel ternary positive electrode material obtained by the above-mentioned surface treatment method.

Compared with the prior art, the characteristics of the present invention are:

1. The high nickel ternary positive electrode material powder is coated with polyacrylic acid solution, and the alkaline compounds on the surface of the high nickel content ternary positive electrode material are removed by surface reaction, on the one hand, the high nickel content ternary positive electrode material is eliminated under conventional conditions. The problem that the slurry becomes gel occurs during pulping; on the other hand, because the obtained carbon (unshaped carbon)-coated high-nickel ternary positive electrode material does not need to be washed with water, it can be directly slurried, which overcomes the problem of alkaline removal caused by water washing. The resulting decrease in charge and discharge capacity is insufficient.

2. The carbon-coated high-nickel ternary positive electrode material obtained by the method of the present invention maintains the original layered crystal structure of the ternary positive electrode material and does not produce impurity phases. The electrochemical performance of the positive electrode material was tested with a button battery, and there was no problem similar to the decrease in the positive electrode capacity due to the increase in the diffusion resistance of lithium ions after the metal oxide coating treatment. Under the condition of the first discharge specific capacity>190mAh/g, and the cycle performance is good; in the subsequent slurry mixing process, there is no problem that the slurry becomes gel and fails.

Description of drawings

1 is the XRD pattern of the carbon-coated LiNi _0.7 Co _0.1 Mn _0.2 O ₂ ternary positive electrode material prepared in Example 1 of the present invention;

2 is a SEM image of the carbon-coated LiNi _0.7 Co _0.1 Mn _0.2 O ₂ ternary positive electrode material prepared in Example 1 of the present invention;

3 is a charge-discharge curve diagram of the carbon-coated LiNi _0.7 Co _0.1 Mn _0.2 O ₂ ternary positive electrode material prepared in Example 1 of the present invention at 0.2C;

4 is a charge-discharge curve diagram of the carbon-coated LiNi _0.7 Co _0.1 Mn _0.2 O ₂ ternary positive electrode material prepared in Example 1 of the present invention at 1C;

FIG. 5 is the XRD pattern of the LiNi _0.7 Co _0.1 Mn _0.2 O ₂ ternary cathode material prepared in Comparative Example 1 of the present invention;

6 is a SEM image of the LiNi _0.7 Co _0.1 Mn _0.2 O ₂ ternary cathode material prepared in Comparative Example 1 of the present invention;

FIG. 7 is a picture of the gel formed by the LiNi _0.7 Co _0.1 Mn _0.2 O ₂ ternary cathode material prepared in Comparative Example 1 during the slurry mixing process.

Detailed ways

The present invention will be described in further detail below in conjunction with specific embodiments to better understand the content of the present invention, but the present invention is not limited to the following embodiments.

Example 1: Carbon-coated LiNi _0.7 Co _0.1 Mn _0.2 O ₂ Ternary Cathode Material

1) get nickel sulfate, cobalt sulfate and manganese sulfate and be dissolved in water, obtain the first mixed solution, control the concentration of total metal ions in the first mixed solution to be 2mol/L, and the mol ratio of nickel ion, cobalt ion and manganese ion is 7:1:2; add a precipitant and a complexing agent to the first mixed solution to carry out co-precipitation reaction, the total time of co-precipitation reaction is designed to be 6h, after the reaction is completed, the obtained reaction material is filtered, the precipitate is collected, washed with water at 80°C drying under conditions to obtain nickel cobalt manganese hydroxide precursor; wherein,

The precipitating agent is a sodium hydroxide solution with a concentration of 2 mol/L, and its dosage is to control the pH=11.5 of the system in the entire co-precipitation reaction process, and it is added dropwise throughout the entire co-precipitation reaction process; the complexing agent is a concentration of It is 25% ammonia water, and its addition amount is calculated by adding 20mL per liter of the first mixed solution, and it is evenly added dropwise within 6h;

2) nickel-cobalt-manganese hydroxide precursor and lithium hydroxide are placed in a drum-type high-speed mixer to mix uniformly, wherein the consumption of lithium hydroxide is 1.03 times of the theoretical lithium content according to LiNi _0.7 Co _0.1 Mn _0.2 O ₂ , the obtained The mixture was placed in an oxidizing atmosphere and kept at 760°C for 6 hours to obtain LiNi _0.7 Co _0.1 Mn _0.2 O ₂ powder;

3) obtaining a polyacrylic acid solution with a solid content of 0.002%;

4) Weigh the LiNi _0.7 Co _0.1 Mn _0.2 O ₂ powder and the polyacrylic acid solution with a solid content of 0.002% in a mass ratio of 1:1, and then place the LiNi _0.7 Co _0.1 Mn _0.2 O ₂ powder in a solid content of 0.002%. In the polyacrylic acid solution, stir and mix for 3 hours, take out, and dry at 150°C to obtain LiNi _0.7 Co _0.1 Mn _0.2 O ₂ powder coated with polyacrylic acid;

5) The obtained polyacrylic acid-coated LiNi _0.7 Co _0.1 Mn _0.2 O ₂ powder was placed under vacuum and heated to 650° C. (the heating rate was 5° C./min), and then an oxidizing atmosphere was introduced, and the temperature was kept for 5 hours to obtain carbon coating. LiNi _0.7 Co _0.1 Mn _0.2 O ₂ ternary cathode material.

The carbon-coated LiNi _0.7 Co _0.1 Mn _0.2 O ₂ ternary cathode material prepared in this example is subjected to X-ray diffraction analysis and electron microscope scanning, and the obtained XRD pattern and SEM pattern are shown in Figures 1 and 2, respectively.

The carbon-coated LiNi _0.7 Co _0.1 Mn _0.2 O ₂ ternary positive electrode material, superconducting carbon black (SP) and PVDF prepared in this example were prepared in a conventional lithium-ion battery slurry preparation environment (dew point -30°C). The binders are mixed in a weight ratio of 94:3:3, and NMP is used as a solvent to make a slurry according to the existing conventional process, and there is no situation that the slurry becomes a gel (jelly-like colloid).

The slurry prepared above was coated on aluminum foil and dried to obtain a positive electrode sheet. The electrochemical performance of the positive electrode sheet was tested by using a 2032-type coin-type half-cell. The negative electrode of the 2032-type coin-type half cell was a metal lithium sheet, and the electrolyte was EC/DMC with a LiPF ₆ concentration of 1.0M (volume ratio 1:1). solution, the diaphragm is made of commercial polyolefin. The first discharge capacity of the positive electrode at 0.2C is 194.1mAh/g, the capacity after 50 cycles is 183.5mAh/g, and the capacity retention rate is 94.5%. The charge-discharge curve is shown in Figure 3; The capacity after the cycle is 183.2mAh/g, the capacity retention rate is 93.5%, and the charge-discharge curve is shown in Figure 4. It can be seen that the carbon-coated LiNi _0.7 Co _0.1 Mn _0.2 O ₂ ternary cathode material obtained by the method of the present invention has the characteristics of high discharge capacity and high electrochemical stability.

Comparative Example 1

The same as steps 1) and 2) of Example 1, LiNi _0.7 Co _0.1 Mn _0.2 O ₂ ternary positive electrode material was prepared.

The LiNi _0.7 Co _0.1 Mn _0.2 O ₂ ternary cathode material prepared in this comparative example was subjected to X-ray diffraction analysis and electron microscope scanning, and the obtained XRD pattern and SEM image were shown in Figure 5 and Figure 6, respectively.

Under the same lithium-ion battery slurry preparation environment as in Example 1, the LiNi _0.7 Co _0.1 Mn _0.2 O ₂ ternary cathode material, SP and PVDF binder prepared in this comparative example were prepared in a ratio of 94:3:3 Mixing by weight, using NMP as solvent to prepare slurry according to the same process as Example 1, the slurry failed due to the formation of gel (jelly-like colloid) during the slurry mixing process, as shown in FIG. 7 .

The LiNi _0.7 Co _0.1 Mn _0.2 O ₂ ternary positive electrode material prepared in this comparative example was washed with water and dried, and then pulped according to the same pulping conditions as in Example 1, to form a positive electrode slurry. Then, according to the same electrode preparation conditions and battery assembly conditions of Example 1, the first discharge capacity of the positive electrode was only 165.4mAh/g under the condition of 0.2C.

Comparing Example 1 and Comparative Example 1, the crystal structure of the LiNi _0.7 Co _0.1 Mn _0.2 O ₂ ternary positive electrode material treated by the surface treatment of the present invention has no change, and no impurity phase is generated; While stabilizing the electrochemical performance, it eliminates the problem that jelly-like colloids are easily produced during the preparation of battery slurry with high nickel content ternary cathode powder under conventional conditions.

Example 2: Carbon-coated LiNi _0.8 Co _0.1 Mn _0.1 O ₂ Ternary Cathode Material

1) get nickel sulfate, cobalt sulfate and manganese sulfate and be dissolved in water, obtain the first mixed solution, control the concentration of total metal ions in the first mixed solution to be 2mol/L, and the mol ratio of nickel ion, cobalt ion and manganese ion is 8:1:1; add precipitating agent and complexing agent to the first mixed solution to carry out co-precipitation reaction, the total time of co-precipitation reaction is designed to be 6h, after the reaction is completed, the obtained reaction material is filtered, and the precipitate is collected, washed with water at 60°C drying under conditions to obtain nickel cobalt manganese hydroxide precursor; wherein,

The precipitating agent is a sodium hydroxide solution with a concentration of 4 mol/L, and its dosage is to control the pH=10 of the system in the entire co-precipitation reaction process, and it is added dropwise throughout the entire co-precipitation reaction process; the complexing agent is a concentration of It is 25% ammonia water, and its addition amount is calculated by adding 10 mL per liter of the first mixed solution, and it is evenly added dropwise within 6 hours;

2) nickel-cobalt-manganese hydroxide precursor and lithium hydroxide are placed in a drum-type high-speed mixer to mix uniformly, wherein the consumption of lithium hydroxide is 1.01 times of the theoretical lithium content according to LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , the obtained The mixture was placed in an oxidizing atmosphere and kept at 720°C for 7 hours to obtain LiNi _0.8 Co _0.1 Mn _0.1 O ₂ powder;

3) obtaining a polyacrylic acid solution with a solid content of 0.005%;

4) Weigh the LiNi _0.8 Co _0.1 Mn _0.1 O ₂ powder and the polyacrylic acid solution with a solid content of 0.005% in a mass ratio of 1:1, and then place the LiNi _0.8 Co _0.1 Mn _0.1 O ₂ powder in a solid content of 0.005%. In the polyacrylic acid solution, stir and mix for 2 hours, take out, and dry at 120 °C to obtain LiNi _0.8 Co _0.1 Mn _0.1 O ₂ powder coated with polyacrylic acid;

5) The obtained polyacrylic acid-coated LiNi _0.8 Co _0.1 Mn _0.1 O ₂ powder was placed in an oxidizing atmosphere, heated to 680° C. (the heating rate was 5° C./min), and kept for 1 h to obtain a carbon-coated LiNi _0.8 Co _0.1 Mn _0.1 O ₂ ternary cathode material.

The carbon-coated LiNi _0.8 Co _0.1 Mn _0.1 O ₂ ternary positive electrode material, superconducting carbon black (SP) and PVDF prepared in this example were prepared in a conventional lithium-ion battery slurry preparation environment (dew point -30°C). The binders are mixed in a weight ratio of 94:3:3, and NMP is used as a solvent to make a slurry according to the existing conventional process, and there is no situation that the slurry becomes a gel (jelly-like colloid).

Example 3: Carbon-coated LiNi _0.8 Co _0.1 Al _0.1 O ₂ Ternary Cathode Material

1) get nickel sulfate, cobalt sulfate and aluminum sulfate and be dissolved in water, obtain the first mixed solution, control the concentration of total metal ions in the first mixed solution to be 2mol/L, and the mol ratio of nickel ion, cobalt ion and aluminum ion is 8:1:1; add precipitating agent and complexing agent to the first mixed solution to carry out co-precipitation reaction, the total time of co-precipitation reaction is designed to be 6h, after the reaction is completed, the obtained reaction material is filtered, the precipitate is collected, washed with water and stored at 80°C drying under conditions to obtain nickel-cobalt-aluminum hydroxide precursor; wherein,

Described precipitating agent is the potassium hydroxide solution that the concentration is 5mol/L, and its consumption is to control the pH=13 of the system in the whole co-precipitation reaction process, and its dripping runs through the whole co-precipitation reaction process; Described complexing agent is quality Ammonia water with a concentration of 25%, the addition amount is calculated by adding 50 mL per liter of the first mixed solution, and it is evenly added dropwise within 6 hours;

2) nickel-cobalt-aluminum hydroxide precursor and lithium hydroxide are placed in a drum-type high-speed mixer to mix homogeneously, wherein the consumption of lithium hydroxide is 1.03 times of the theoretical lithium content according to LiNi _0.8 Co _0.1 Al _0.1 O ₂ , the obtained The mixture was placed in an oxidizing atmosphere and kept at 780°C for 6 hours to obtain LiNi _0.8 Co _0.1 Al _0.1 O ₂ powder;

3) obtaining a polyacrylic acid solution with a solid content of 0.001%;

4) Weigh the LiNi _0.8 Co _0.1 Al _0.1 O ₂ powder and the polyacrylic acid solution with a solid content of 0.001% in a mass ratio of 1:2, and then place the LiNi _0.8 Co _0.1 Al _0.1 O ₂ powder in a solid content of 0.001%. In the polyacrylic acid solution, stir and mix for 1 hour, take out, and dry at 200 °C to obtain LiNi _0.8 Co _0.1 Al _0.1 O ₂ powder coated with polyacrylic acid;

5) The obtained polyacrylic acid-coated LiNi _0.8 Co _0.1 Al _0.1 O ₂ powder is placed in an oxidizing atmosphere, heated to 600° C. (with a heating rate of 5° C./min), and kept for 3 hours to obtain a carbon-coated LiNi _0.8 Co _0.1 Al _0.1 O ₂ ternary cathode material.

The carbon-coated LiNi _0.8 Co _0.1 Al _0.1 O ₂ ternary positive electrode material, superconducting carbon black (SP) and PVDF prepared in this example were prepared in a conventional lithium-ion battery slurry preparation environment (dew point -30°C). The binders are mixed in a weight ratio of 94:3:3, and NMP is used as a solvent to make a slurry according to the existing conventional process, and there is no situation that the slurry becomes a gel (jelly-like colloid).

Example 4: Carbon-coated LiNi _0.6 Co _0.2 Mn _0.2 O ₂ Ternary Cathode Material

1) Purchase LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ternary positive electrode material from the market, spare;

3) obtaining a polyacrylic acid solution with a solid content of 0.003%;

4) Weigh the LiNi _0.6 Co _0.2 Mn _0.2 O ₂ powder and the polyacrylic acid solution with a solid content of 0.003% in a mass ratio of 1:3, and then place the LiNi _0.6 Co _0.2 Mn _0.2 O ₂ powder in a solid content of 0.003%. In the polyacrylic acid solution, stir and mix for 3 hours, take out, and dry at 150 °C to obtain LiNi _0.6 Co _0.2 Mn _0.2 O ₂ powder coated with polyacrylic acid;

5) The obtained polyacrylic acid-coated LiNi _0.6 Co _0.2 Mn _0.2 O ₂ powder is placed in an oxidizing atmosphere, heated to 650° C. (the heating rate is 8° C./min), and kept for 2 hours, to obtain a carbon-coated LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ternary cathode material.

The carbon-coated LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ternary positive electrode material, superconducting carbon black (SP) and PVDF prepared in this example were prepared in a conventional lithium-ion battery slurry preparation environment (dew point -30°C). The binders are mixed in a weight ratio of 94:3:3, and NMP is used as a solvent to make a slurry according to the existing conventional process, and there is no situation that the slurry becomes a gel (jelly-like colloid).

Claims (7)

1. A method for carrying out surface treatment on a high-nickel ternary cathode material is characterized by comprising the following steps: taking a polyacrylic acid solution as a coating solution, placing the high-nickel ternary positive electrode material in the coating solution, stirring and mixing for a certain time, taking out, and drying to obtain polyacrylic acid-coated high-nickel ternary positive electrode material powder; then placing the obtained polyacrylic acid-coated high-nickel ternary positive electrode material powder in an oxidizing atmosphere for heat treatment to obtain a carbon-coated high-nickel ternary positive electrode material; wherein the high-nickel ternary positive electrode material is LiNi_xCo_yM_(1-x-y)O₂X is more than or equal to 0.6 and less than 1, y is more than 0 and less than 0.4, x + y is more than 0 and less than 1, and M is Mn or Al.

2. A surface treatment method according to claim 1, characterized in that: the polyacrylic acid solution has a solid content of 0.001-0.005%.

3. A surface treatment method according to claim 1, characterized in that: the time for stirring and mixing is more than or equal to 0.1 h.

4. A surface treatment method according to claim 1, characterized in that: stirring and mixing for 0.5-3 h.

5. A surface treatment method according to claim 1, characterized in that: the heat treatment is carried out for 3-8h at the temperature of 600-700 ℃.

6. A carbon-coated high-nickel ternary positive electrode material treated by the method of any one of claims 1 to 5.

7. A lithium ion battery comprises a positive plate and is characterized in that: the positive electrode material used on the positive electrode sheet is the carbon-coated high-nickel ternary positive electrode material according to claim 6.