WO2023184996A1 - Modified high-nickel ternary positive electrode material and preparation method therefor - Google Patents

Abstract

Disclosed in the present invention are a modified high-nickel ternary positive electrode material and a preparation method therefor. The modified high-nickel ternary positive electrode material is a cobalt element doped and cobalt element coated high-nickel ternary positive electrode material. The mass fraction of a doped cobalt element is 0.2-2%, and the thickness of a cobalt element coating layer is 20-200 nm. The cobalt element doped on the surface of the high-nickel ternary positive electrode material can improve the cycle performance of the high-nickel ternary positive electrode material, and cobalt hydroxide reacts with residual lithium on the surface of the material during microwave treatment of the coated cobalt element, such that the content of the residual lithium on the surface of the material can be reduced. Under the combined action of doping and coating, the performance of the high-nickel ternary positive electrode material is obviously improved. Moreover, the preparation method in the present invention is simple, low in cost, environment-friendly, and suitable for large-scale industrial production.

Description

A modified high-nickel ternary cathode material and its preparation method Technical field

The invention belongs to the technical field of electrode materials, and specifically relates to a modified high-nickel ternary cathode material and a preparation method thereof.

Background technique

The requirement for high energy density in power batteries has promoted the development of high-nickel cathode materials, lithium-rich manganese-based cathode materials and lithium-sulfur batteries. The high-nickel ternary cathode material LiNi _x Co _y Mn _1-xy O ₂ (NCM) has With the advantages of high specific capacity, good rate performance and relatively low cost, it is in an absolutely leading position among various cathode materials and is considered to be one of the most promising cathode materials for power batteries.

However, high-nickel ternary cathode materials have shortcomings such as poor cyclability, thermal stability, and safety. The high-nickel ternary cathode material's high-temperature synthesis, storage in air, and repeated charge and discharge will cause its layered structure to change into a rock salt structure. This transformation inhibits the transfer of lithium ions from the surface of the high-nickel ternary cathode material to its interior. role. In addition, during storage in the air, the high-nickel _ternary cathode material will react with moisture and carbon dioxide in the air, thereby forming residual lithium compounds containing LiOH, _LiHCO3 , and _Li2CO3 on its surface. These residual lithium compounds will have adverse effects on lithium-ion batteries, causing the lithium-ion battery to produce gas during the cycle. In addition, it will also cause the slurry of high-nickel ternary cathode materials to gel during the manufacturing process of lithium-ion batteries. change.

Based on these problems existing in high-nickel ternary cathode materials themselves, it is of great significance to develop a technology that can effectively improve or overcome the defects of high-nickel ternary cathode materials, which will help promote the further development and utilization of high-nickel ternary cathode materials.

Contents of the invention

The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a modified high-nickel ternary cathode material and a preparation method thereof. The high-nickel ternary cathode material is modified by cobalt element doping and cobalt element coating. The cobalt element doping has It is beneficial to improve the cycle performance of high-nickel ternary cathode materials, and the cobalt layer coated with microwave heating method can reduce the residual lithium content in high-nickel ternary cathode materials, thereby effectively solving the problem of gas production during battery cycling. Moreover, this preparation method is simple, low-cost, environmentally friendly, and suitable for large-scale industrial production.

A first aspect of the present invention provides a high-nickel ternary cathode material. The ternary cathode material is a high-nickel ternary cathode material doped with cobalt element and coated with cobalt element.

According to the first aspect of the present invention, in some embodiments of the present invention, the mass fraction of cobalt element doping in the high-nickel ternary cathode material is 0.2-2%.

In some preferred embodiments of the present invention, in the high-nickel ternary cathode material, the thickness of the cobalt element coating layer is 20 nm-200 nm.

In some preferred embodiments of the present invention, in the high-nickel ternary cathode material, the thickness of the cobalt element coating layer is 50 nm-100 nm.

A second aspect of the present invention provides a method for preparing the high-nickel ternary cathode material described in the first aspect of the present invention. The preparation method includes the following steps:

(1) Coat the cobalt-containing compound A on the surface of the nickel cobalt manganese hydroxide precursor Ni _x Co _y Mn _1-xy (OH) ₂ to prepare a nickel cobalt manganese hydroxide precursor coated with cobalt element on the surface;

(2) Mix and calcine the nickel cobalt manganese hydroxide precursor surface-coated with cobalt element described in step (1) and the lithium-containing compound to prepare a high-nickel ternary cathode material with surface doped cobalt element;

(3) Mix the surface-doped high-nickel ternary cathode material with cobalt element described in step (2) and the cobalt-containing compound B and then microwave process to prepare a surface-doped and coated high-nickel ternary cathode material with cobalt element LiNi _x Mn _y Co _1-xy O ₂ ·nLiCoO ₂ .

According to the second aspect of the present invention, in some embodiments of the present invention, the chemical formula of the nickel cobalt manganese hydroxide precursor described in step (1) is _Nix Co _y Mn _1-xy (OH) ₂ in which 1.00 >x≥0.6, y>0, 1-xy>0.

In some preferred embodiments of the present invention, the nickel cobalt manganese hydroxide precursor _Nix Co _y Mn _1-xy (OH) ₂ in step (1) is Ni _0.95 Co _0.03 Mn _0.02 (OH) ₂ .

In some preferred embodiments of the present invention, the Ni _0.95 Co _0.03 Mn _0.02 (OH) ₂ is purchased from Guangdong Bangpu Recycling Technology Co., Ltd.

In some preferred embodiments of the present _{invention , the} chemical _{formula LiN} x≥0.6, y>0, 1-xy>0, n>0.

Among them, LiCoO ₂ exists in _{LiNixMnyCo1 -xyO2 in} the form of _doping and coating.

In some preferred embodiments of the present invention, the specific steps in step (1) are to place the solution formed by dissolving the cobalt-containing compound A in water for later use; and put the nickel cobalt manganese hydroxide precursor Ni _x Co _y Mn _1-xy (OH) ₂ is placed in a mixing device with a heating function and stirred. During the stirring process, the cobalt-containing compound A is coated in Ni _x Co _y Mn _1-xy (OH) ₂ using a spray method. On the surface, a nickel cobalt manganese hydroxide precursor coated with cobalt element was prepared.

In some preferred embodiments of the present invention, the stirring speed of the nickel cobalt manganese hydroxide precursor _Nix Co _y Mn _1-xy (OH) ₂ is 200-800 rpm.

In some preferred embodiments of the present invention, _{NixCoyMn1 -xy} (OH) ₂ continues to stir after the spraying _is completed.

In some more preferred embodiments of the present invention, the stirring time after the spraying is completed is 30-300 minutes.

In some more preferred embodiments of the present invention, the spray time of the spray method is 5-120 minutes.

In some more preferred embodiments of the present invention, the spray time of the spray method is 20-100 minutes.

In some more preferred embodiments of the present invention, the spray time of the spray method is 30-60 minutes.

In some more preferred embodiments of the present invention, the spray flow rate of the spray method is 3-6 mL/min.

In some more preferred embodiments of the present invention, the mass ratio of the cobalt-containing compound A to water is 1: (1-100).

In some preferred embodiments of the present invention, the cobalt-containing compound A in step (1) includes at least one of cobalt chloride hexahydrate, cobalt nitrate hexahydrate, cobalt acetate tetrahydrate, and cobalt sulfate heptahydrate.

In some preferred embodiments of the present invention, the molar ratio of _Nix Co _y Mn _1-xy (OH) ₂ in step (1) to the cobalt element in the cobalt-containing compound A is 1: (0.002-0.02).

In some preferred embodiments of the present invention, the lithium-containing compound in step (2) includes at least one of lithium hydroxide, lithium carbonate, lithium fluoride, lithium chloride, and lithium nitrate.

In some preferred embodiments of the present invention, the molar ratio of _{NixCoyMn1 -xy} (OH) ₂ in step (2) to the lithium element in the lithium- _containing compound is 1:(1-1.2).

In some preferred embodiments of the present invention, the calcination temperature described in step (2) is 700-1000°C.

In some preferred embodiments of the present invention, the calcination time described in step (2) is 10-20 h.

In some preferred embodiments of the present invention, the cobalt-containing compound B in step (3) includes cobalt oxide, cobalt tetroxide, cobalt oxyhydroxide, cobalt hydroxide, cobalt trioxide, cobalt carbonate, cobalt acetate, and cobalt oxalate. At least one.

In some preferred embodiments of the present invention, the molar ratio of the high-nickel ternary cathode material surface-doped with cobalt element and the cobalt element of the cobalt-containing compound B in step (3) is 1:(0.002-0.02).

In some preferred embodiments of the present invention, the power of the microwave treatment described in step (3) is 1000W-1800W.

In some preferred embodiments of the present invention, the temperature of the microwave treatment described in step (3) is 200-400°C.

In some preferred embodiments of the present invention, the microwave treatment time described in step (3) is 10-120 minutes.

A third aspect of the present invention provides a positive electrode sheet, and the active material in the positive electrode sheet is the high-nickel ternary positive electrode material of the first aspect of the present invention.

According to the third aspect of the present invention, in some embodiments of the present invention, the positive electrode sheet further includes a conductive agent and a binder.

In some preferred embodiments of the present invention, the mass ratio of active material, conductive agent and binder in the positive electrode sheet is 90:5:5.

In some preferred embodiments of the present invention, the preparation method of the positive electrode sheet is: dispersing the active material, conductive agent and binder in N-methylpyrrolidone, stirring for 4 hours and then coating on the surface of the aluminum foil, 120 The positive electrode sheet is obtained after vacuum drying at ℃.

A fourth aspect of the present invention provides a lithium-ion battery assembled using the positive electrode sheet according to the third aspect of the present invention.

According to the fourth aspect of the present invention, in some embodiments of the present invention, the assembly method of the lithium-ion battery is: using the positive electrode sheet described in the third aspect of the present invention as the positive electrode of the lithium-ion battery, and metallic lithium as the lithium For the counter electrode of the ion battery, the button cell is assembled in a glove box filled with high-purity argon gas.

In some preferred embodiments of the present invention, the button battery is a CR2032 lithium-ion battery.

The beneficial effects of the present invention are:

1. In the present invention, a spray coating method is used to coat the precursor of the high-nickel ternary cathode material. The formed coating layer is more uniform. After coating, it is sintered with a lithium-containing compound to prepare a surface-doped cobalt material. The high-nickel ternary cathode material of the element is coated with the high-nickel ternary cathode material doped with cobalt element on the surface using microwave heating method. The microwave heating method has the advantages of short heating time and uniform heating, which is helpful to prepare the coating. Uniform layer of high-nickel ternary cathode material. Moreover, the preparation method of the present invention is simple, low-cost, environmentally friendly, and suitable for large-scale industrial production.

2. The cobalt element in the cobalt element-doped and cobalt element-coated high-nickel ternary cathode material prepared by the present invention is distributed at different depths, which is conducive to forming a protective layer on the surface of the cathode material, which can inhibit the battery cycle process. The mixed arrangement of lithium and nickel in the cathode material makes the high-nickel ternary cathode material have excellent cycle performance.

3. In the present invention, the cobalt element doped in the surface layer of the high-nickel ternary cathode material helps to improve the cycle performance of the cathode material. The cobalt element coated in the surface layer of the cathode material can be combined with the residues on the surface of the cathode material during microwave heating coating. Lithium reaction, thus reducing the residual lithium content on the surface of the cathode material, which can effectively solve the problem of gas production during battery cycling. Under the joint action of surface doping and surface coating of cobalt element, the electrochemical performance of the high-nickel ternary cathode material in the present invention is significantly improved.

Description of drawings

Figure 1 is an SEM image of the high-nickel ternary cathode material prepared in Example 1 of the present invention;

Figure 2 is the XRD pattern of the product after microwave heating of a mixture composed of cobalt hydroxide, lithium hydroxide and lithium carbonate;

Figure 3 is a graph showing the changing trend of the capacity retention rate with the number of cycles of the lithium-ion battery assembled with the high-nickel ternary cathode material in Examples 1-3 and Comparative Examples 1-3.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments, and the advantages and features of the present invention will become clearer with the description. However, these embodiments are only exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that the details and forms of the technical solution of the present invention can be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and substitutions all fall within the protection scope of the present invention.

Example 1 Preparation of a modified high-nickel ternary cathode material

(1) Preparation of nickel cobalt manganese hydroxide precursor with surface coating of cobalt element:

Dissolve 45.82g of cobalt chloride hexahydrate in 120 mL of deionized water to make a cobalt chloride aqueous solution, and place the cobalt chloride aqueous solution in the spray equipment. Take 1111.7g of the nickel cobalt manganese hydroxide precursor Ni _0.95 Co _0.03 Mn _0.02 (OH) ₂ and place it in a high-efficiency mixer with heating function for stirring. The heating temperature is 150°C and the stirring speed is 600 rpm. In the process of high-speed stirring of the precursor, use a spray device filled with cobalt chloride aqueous solution to spray. Control the spray time to 30 minutes and the spray flow rate to 4 mL/min. The solution will be completely sprayed. After the spray is completed, a high-efficiency mixer with heating function will be used. Continue stirring for 120 minutes until Ni _0.95 Co _0.03 Mn _0.02 (OH) ₂ is fully dried to prepare a nickel cobalt manganese hydroxide precursor with cobalt element on the surface;

(2) Preparation of high-nickel ternary cathode materials doped with cobalt on the surface:

1kg of the cobalt-coated nickel-cobalt-manganese hydroxide precursor prepared in step (1) and 462g of lithium hydroxide were placed in a ball mill and mixed. The ball milling speed was 500 rpm, the ball milling time was 4 hours, and then calcined at 800°C. After 15 hours, a high-nickel ternary cathode material doped with cobalt on the surface was prepared;

(3) Preparation of high-nickel ternary cathode material with surface doped and coated cobalt element:

Place 975.6g of the high-nickel ternary cathode material doped with cobalt on the surface obtained in step (2) and 13.95g of cobalt hydroxide in a ball mill to mix. The ball milling speed is 500rpm and the ball milling time is 4h. Then, the ball milling time is 4h. Microwave processing in a power microwave oven, the power of microwave processing is 1600W, the temperature of microwave processing is 300°C, and the microwave processing time is 60 minutes. A high-nickel ternary cathode material whose surface is doped and coated with cobalt element is prepared. The chemical formula of the high-nickel ternary cathode material whose surface is doped and coated with cobalt element is LiNi _0.936 Co _0.044 Mn _0.02 O ₂ ·0.015LiCoO ₂ .

Example 2 Preparation of a modified high-nickel ternary cathode material

(1) Preparation of nickel cobalt manganese hydroxide precursor with surface coating of cobalt element:

Dissolve 34.92g of cobalt nitrate in 120 mL of deionized water to make a cobalt nitrate aqueous solution, and place the cobalt nitrate aqueous solution in the spray equipment. Take 1111.7g of the nickel cobalt manganese hydroxide precursor Ni _0.95 Co _0.03 Mn _0.02 (OH) ₂ and place it in a high-efficiency mixer with heating function for stirring. The heating temperature is 150°C and the stirring speed is 600 rpm. During the process of high-speed stirring of the precursor, use a spray device equipped with a cobalt nitrate aqueous solution to spray. Control the spray time to 30 minutes and the spray flow rate to 4 mL/min. The solution will be completely sprayed. After the spray is completed, the high-efficiency mixer with heating function will continue. Stir for 120 minutes until the precursor is fully dry to prepare a nickel cobalt manganese hydroxide precursor with cobalt element coating on the surface;

(2) Preparation of high-nickel ternary cathode materials doped with cobalt on the surface:

Place 1kg of the cobalt-coated nickel-cobalt-manganese hydroxide precursor prepared in step (1) and 462g of lithium hydroxide in a ball mill to mix. The ball milling speed is 500rpm, the ball milling time is 4h, and then 800°C Calcined for 15 hours to obtain a high-nickel ternary cathode material doped with cobalt on the surface;

(3) Preparation of high-nickel ternary cathode material with surface doped and coated cobalt element:

Place 975.6g of the high-nickel ternary cathode material doped with cobalt on the surface obtained in step (2) and 9.30g of cobalt hydroxide in a ball mill to mix. The ball milling speed is 500rpm and the ball milling time is 4h. Then, the ball milling time is 4h. Microwave heating in a microwave oven, the microwave heating power is 1600W, the microwave heating temperature is 300°C, and the microwave heating time is 60 minutes. A high-nickel ternary cathode material whose surface is doped and coated with cobalt element is prepared. The chemical formula of the high-nickel ternary cathode material whose surface is doped and coated with cobalt element is LiNi _0.94 Co _0.04 Mn _0.02 O ₂ ·0.01LiCoO ₂ .

Example 3 Preparation of a modified high-nickel ternary cathode material

(1) Preparation of nickel cobalt manganese hydroxide precursor with surface coating of cobalt element:

Dissolve 84.65g of cobalt acetate tetrahydrate in 120 mL of deionized water to prepare a cobalt acetate aqueous solution, and place the cobalt acetate aqueous solution in the spray equipment. Take 1kg of nickel cobalt manganese hydroxide precursor Ni _0.95 Co _0.03 Mn _0.02 (OH) ₂ and place it in a high-efficiency mixer with heating function for stirring. The heating temperature is 150°C and the stirring speed is 600 rpm. During the process of high-speed stirring of the precursor, use a spray device filled with cobalt acetate aqueous solution to spray. Control the spray time to 30 minutes and the spray flow rate to 4 mL/min. The solution will be completely sprayed. After the spray is completed, the high-efficiency mixer with heating function will continue. Stir for 120 minutes until the precursor is fully dry to prepare a nickel cobalt manganese hydroxide precursor with cobalt element coating on the surface;

(2) Preparation of high-nickel ternary cathode materials with cobalt-containing elements doped on the surface:

Mix 1kg of the nickel cobalt manganese hydroxide precursor with surface-coated cobalt element prepared in step (1) and 462g of lithium hydroxide by ball milling. The ball milling speed is 500rpm and the ball milling time is 4h. Then it is calcined at 800°C for 15h to prepare High-nickel ternary cathode material with surface doped with cobalt element;

(3) Preparation of high-nickel ternary cathode material with surface doped and coated cobalt element:

Mix 1kg of the high-nickel ternary cathode material surface-doped with cobalt prepared in step (2) and 4.65g of cobalt hydroxide through ball milling. The speed of the ball milling is 500rpm and the ball milling time is 4h. Then microwave it in a high-power microwave oven. For heating, the microwave heating power is 1600W, the microwave heating temperature is 300°C, and the microwave heating time is 60 minutes. A high-nickel ternary cathode material whose surface is doped and coated with cobalt element is prepared. The chemical formula of the high-nickel ternary cathode material whose surface is doped and coated with cobalt element is LiNi _0.945 Co _0.035 Mn _0.02 O ₂ ·0.005LiCoO ₂ .

Comparative example 1

Compared with Example 1, the difference between Comparative Example 1 and Example 1 is that the high-nickel ternary cathode material prepared in Comparative Example 1 is neither coated with cobalt element nor doped with cobalt element. The specific steps are:

Take 1kg of nickel cobalt manganese hydroxide precursor Ni _0.95 Co _0.03 Mn _0.02 (OH) ₂ and mix it with 462g of lithium hydroxide by ball milling. The ball milling speed is 500rpm and the ball milling time is 4h. Then it is calcined at 800℃ for 15h to obtain high nickel. Ternary cathode material LiNi _0.95 Co _0.03 Mn _0.02 O ₂ .

Comparative example 2

Compared with Example 1, the difference between Comparative Example 2 and Example 1 is that the high-nickel ternary cathode material prepared in Comparative Example 2 is only coated with cobalt element and is not doped with cobalt element. The specific steps are:

(1) Take 1kg of nickel cobalt manganese hydroxide precursor Ni _0.95 Co _0.03 Mn _0.02 (OH) ₂ and mix it with 462g of lithium hydroxide by ball milling. The ball milling speed is 500rpm and the ball milling time is 4h. Then calcined at 800°C for 15h to prepare Obtain high nickel ternary cathode material.

(2) Mix 975.6g of the high-nickel ternary cathode material obtained in step (1) with 13.95g of cobalt hydroxide through ball milling. The speed of the ball milling is 500rpm and the milling time is 4h. Then microwave it in a high-power microwave oven. The power of microwave heating is 1600W, the temperature of microwave heating is 300°C, and the time of microwave heating is 60 minutes. A high-nickel ternary cathode material LiNi _0.95 Co _0.03 Mn _0.02 O ₂ with surface coating of cobalt element was prepared.

Comparative example 3

Compared with Example 1, the difference between Comparative Example 3 and Example 1 is that the high-nickel ternary cathode material prepared in Comparative Example 3 is only a high-nickel ternary cathode material doped with cobalt element, and is not coated with cobalt. The steps are: :

(1) Dissolve 45.82g of cobalt chloride hexahydrate in 120 mL of deionized water to make a cobalt chloride aqueous solution, and place the cobalt chloride aqueous solution in the spray equipment. Take 1111.7g of the nickel cobalt manganese hydroxide precursor Ni _0.95 Co _0.03 Mn _0.02 (OH) ₂ and place it in a high-efficiency mixer with heating function for stirring. The heating temperature is 150°C and the stirring speed is 600 rpm. In the process of high-speed stirring of the precursor, use a spray device filled with cobalt chloride aqueous solution to spray. Control the spray time to 30 minutes and the spray flow rate to 4 mL/min. The solution will be completely sprayed. After the spray is completed, a high-efficiency mixer with heating function will be used. Continue stirring for 120 minutes until the precursor is fully dried to obtain a nickel cobalt manganese hydroxide precursor with cobalt element coating on the surface;

(2) Mix 1kg of the cobalt-coated nickel-cobalt-manganese hydroxide precursor prepared in step (1) with 462g of lithium hydroxide by ball milling. The ball milling speed is 500rpm and the ball milling time is 4h, and then calcined at 800°C. In 15h, a high-nickel ternary cathode material doped with cobalt element on the surface was prepared. The chemical formula of the high-nickel ternary cathode material with cobalt element doped on the surface is LiNi _0.936 Co _0.044 Mn _0.02 O ₂ ·0.015LiCoO ₂ .

Characterization and performance testing of modified high-nickel ternary cathode materials

(1) Morphological characterization:

Figure 1 is an SEM image of the modified high-nickel ternary cathode material prepared in Example 1. It can be seen from the figure that the particle surface of the modified high-nickel ternary cathode material has fine powder distribution (circled in Figure 1 Partly), which is a substance formed after the reaction of cobalt hydroxide with the residual lithium on the surface of the modified high-nickel ternary cathode material under microwave heating conditions.

(2) Test of residual lithium content in high-nickel ternary cathode materials:

The test method for residual lithium content in high-nickel ternary cathode materials is as follows: disperse the high-nickel ternary cathode materials in deionized water, stir for 30 minutes, filter with a vacuum filtration device, collect the filtrate and weigh it, and place the filtrate On a potentiometric titrator, use 0.1 mol/L hydrochloric acid labeled solution for potentiometric titration to pH ≤ 4, and record the consumption volume of hydrochloric acid at the mutation point in the titration curve. The data are then processed according to conventional methods in this field, and the residual lithium content in the high-nickel ternary cathode material is calculated.

The test results of the residual lithium content in the high-nickel ternary cathode materials prepared in Examples 1-3 and Comparative Examples 1-3 are as shown in Table 1. From the data in Table 1, it can be seen that in Example 1-3 The residual lithium content is lower than that in Comparative Examples 1-3. This is because when microwave coating of cobalt element, cobalt hydroxide and residual lithium on the surface of the material (residual lithium is composed of lithium hydroxide and lithium carbonate) are processed. The reaction generates lithium cobalt oxide, thereby reducing the residual lithium content on the surface of the material. Figure 2 is the XRD pattern of the product after microwave heating of a mixture of cobalt hydroxide, lithium hydroxide and lithium carbonate. The molar ratio of cobalt hydroxide, lithium hydroxide and lithium carbonate is 2:1:1. From the figure 2, it can be seen that the peaks in the XRD pattern are all characteristic peaks of LiCoO, which further illustrates that during the microwave heating process _of the modified high-nickel ternary cathode material prepared in the embodiment of the present invention, cobalt hydroxide and lithium hydroxide It reacts with residual lithium composed of lithium carbonate to generate LiCoO ₂ .

Table 1 Statistics of residual lithium content in high-nickel ternary cathode materials prepared in Examples 1-3 and Comparative Examples 1-3

sample	Residual lithium content (%)
Example 1	0.1782
Example 2	0.1945
Example 3	0.2069
Comparative example 1	0.2744
Comparative example 2	0.2146
Comparative example 3	0.2698

(3)Electrochemical performance test

Assembly of lithium-ion battery: Mix the conductive agent and the binder in a certain proportion and add it to 1-methyl 2-pyrrolidone. After fully stirring in a vacuum mixer, add the positive electrode material in the embodiments of the present invention or the comparative example. (Among them, the mass ratio of positive electrode material, binder and conductive agent is 90:5:5), the solid content of the slurry is 50%, stir thoroughly and prepare the slurry of electrode material, and coat it on aluminum foil On the above, the positive electrode sheet is obtained by drying and rolling. In this embodiment, the areal density of the positive electrode sheet is 3.7g/cm ² . Using the obtained positive electrode sheet as the positive electrode and metallic lithium as the counter electrode, a CR2032 lithium-ion button battery was assembled for electrochemical performance testing. Among them, the electrolyte was E20, purchased from Shenzhen Xinzhoubang Technology Co., Ltd.

Electrochemical performance test of lithium-ion battery: The test equipment is a blue battery test system, the voltage window is 2.8V-4.3V, the current density is 1C, and the test temperature is normal temperature.

Figure 3 shows the capacity retention rate of the lithium-ion batteries assembled using the cathode materials in Examples 1-3 and Comparative Examples 1-3 as a function of the number of cycles. It can be seen from the data in Figure 3 that compared to the In Example 1-3, the capacity retention rate of the lithium-ion battery assembled using the cathode material in Example 1-3 decreases slowly with the number of cycles and has a high capacity retention rate. This shows that simultaneous cobalt doping and cobalt coating of high-nickel ternary cathode materials can further improve the cycle performance of high-nickel ternary cathode materials, and the electrochemical performance is better than pure cobalt doping or cobalt coating. Lithium-ion batteries assembled from cathode materials. In addition, the capacity retention rate of the lithium-ion batteries assembled with the cathode materials of Comparative Examples 2 and 3 decreased more slowly than that of the lithium-ion battery assembled with the cathode material of Comparative Examples 1, indicating that a single pair of high-nickel ternary cathode materials undergoes cobalt Element coating or cobalt element doping can improve the cycle performance of high-nickel ternary cathode materials.

Table 2 shows the electrochemical properties of lithium-ion batteries assembled with the high-nickel ternary cathode materials prepared in Examples 1-3 and Comparative Examples 1-3. Table 2 includes the first-cycle discharge specific capacity, first-cycle efficiency and 100 cycles. Capacity retention rate. As can be seen from Table 2, the first-cycle discharge specific capacity and first-cycle efficiency of the lithium-ion battery prepared from the high-nickel ternary cathode material in Examples 1-3 are both higher than those of the high-nickel ternary cathode material in Comparative Examples 1-3. The assembled lithium-ion battery has a high capacity retention rate for 100 cycles, and the capacity retention rate of the lithium-ion battery assembled with the high-nickel ternary cathode material in Examples 1-3 is significantly higher than that of the high-nickel ternary cathode material assembled in Comparative Examples 1-3. Lithium-ion battery, which shows that using the method in the embodiment of the present invention to dope and coat the high-nickel ternary cathode material with cobalt element can significantly improve the cycle performance and cycle life of the high-nickel ternary cathode material.

Table 2 Electrochemical properties of high-nickel ternary cathode materials prepared in Examples 1-3 and Comparative Examples 1-3

sample	Discharge specific capacity in the first week (mAh/g)	First week efficiency (%)	Capacity retention rate after 100 cycles (%)
Example 1	229.8	92.7	83.74
Example 2	228.9	92.0	81.53
Example 3	227.3	92.1	80.31
Comparative example 1	226.8	90.9	69.38
Comparative example 2	226.7	91.7	78.55
Comparative example 3	226.9	91.0	74.55

The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, etc. may be made without departing from the spirit and principles of the present invention. All simplifications should be equivalent substitutions, and are all included in the protection scope of the present invention.

Claims (10)

1. A high-nickel ternary cathode material, characterized in that the ternary cathode material is a high-nickel ternary cathode material doped with cobalt element and coated with cobalt element, wherein the mass fraction of the cobalt element doping is 0.2 -2%, and the thickness of the coating layer coated with cobalt element is 20-200nm.
2. The preparation method of high-nickel ternary cathode material according to claim 1, characterized in that the preparation method includes the following steps:

   (1) Coat the cobalt-containing compound A on the surface of the nickel cobalt manganese hydroxide precursor Ni _x Co _y Mn _1-xy (OH) ₂ to prepare a nickel cobalt manganese hydroxide precursor coated with cobalt element on the surface, In the formula, 1.00>x≥0.6, y>0, 1-xy>0;

   (2) Mix and calcine the nickel cobalt manganese hydroxide precursor surface-coated with cobalt element described in step (1) and the lithium-containing compound to prepare a high-nickel ternary cathode material with surface doped cobalt element;

   (3) Mix the surface-doped high-nickel ternary cathode material with cobalt element described in step (2) and the cobalt-containing compound B and then microwave process to prepare a surface-doped and coated high-nickel ternary cathode material with cobalt element LiNi _x Mn _y Co _1-xy O ₂ ·nLiCoO ₂ , in the formula, 1.00>x≥0.6, y>0, 1-xy>0, n>0;

   Wherein, the calcination temperature in step (2) is 700-1000°C, and the calcination time is 10-20h.
3. The method according to claim 2, characterized in that, in step (1), the solution of the cobalt-containing compound A mixed with water is coated on the surface of _Nix Co _y Mn _1-xy (OH) ₂ by spraying method, Wherein, the spray time of the spray method is 5-120min, and the spray flow rate is 3-6mL/min.
4. The method according to claim 3, characterized in that the mass ratio of the cobalt-containing compound A and water is 1: (1-100).
5. The method according to claim 2, wherein the cobalt-containing compound A in step (1) includes at least one of cobalt chloride hexahydrate, cobalt nitrate hexahydrate, cobalt acetate tetrahydrate, and cobalt sulfate heptahydrate. , preferably, the molar ratio of _Nix Co _y Mn _1-xy (OH) ₂ described in step (1) to the cobalt element in the cobalt-containing compound A is 1: (0.002-0.02).
6. The method according to claim 2, wherein the lithium-containing compound in step (2) includes at least one of lithium hydroxide, lithium carbonate, lithium fluoride, lithium chloride, and lithium nitrate, preferably, The molar ratio of _{NixCoyMn1 -xy} (OH) ₂ and the lithium element in the lithium-containing _compound described in step (2) is 1:(1-1.2).
7. The method of claim 2, wherein the cobalt-containing compound B in step (3) includes cobalt oxide, cobalt tetroxide, cobalt oxyhydroxide, cobalt hydroxide, cobalt trioxide, cobalt carbonate, cobalt acetate, and cobalt oxalate. At least one of them, preferably, the molar ratio of the high-nickel ternary cathode material surface-doped with cobalt element in step (3) to the cobalt element in the cobalt-containing compound B is 1: (0.002-0.02).
8. The method according to claim 2, characterized in that the microwave treatment time in step (3) is 10-120 min; the microwave treatment temperature is 200-400°C, and the microwave treatment power is 1000 -1800W.
9. The positive electrode sheet is prepared using the high-nickel ternary positive electrode material described in claim 1, and the positive electrode sheet further includes a conductive agent and a binder.
10. A lithium-ion battery assembled using the positive electrode sheet described in claim 9.

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