阅读说明：本技术 一种用于正极材料的水洗砂磨包覆方法、制备方法、正极材料及电池 (Water washing and sanding coating method for positive electrode material, preparation method, positive electrode material and battery ) 是由 王壮 张树涛 李子郯 王亚州 白艳 马加力 于 2021-07-30 设计创作，主要内容包括：本发明提供了一种用于正极材料的水洗砂磨包覆方法、制备方法、正极材料及电池,所述的水洗砂磨包覆方法：正极颗粒和包覆剂混合水洗,在水洗的同时进行砂磨使得包覆剂包覆于正极颗粒表面。本发明在对正极颗粒进行水洗的过程中同时完成包覆,将传统的两步操作整合为一步操作,既起到降低残碱的作用还能将正极颗粒均匀包覆,减少工艺步骤及生产成本,降低副反应的发生,提高材料的循环稳定性。(The invention provides a washing and sanding coating method for a positive electrode material, a preparation method, the positive electrode material and a battery, wherein the washing and sanding coating method comprises the following steps: and mixing and washing the positive electrode particles and the coating agent, and sanding while washing to coat the coating agent on the surfaces of the positive electrode particles. The method disclosed by the invention can be used for simultaneously finishing coating in the process of washing the anode particles, and integrating the traditional two-step operation into one-step operation, so that the effect of reducing residual alkali is achieved, the anode particles can be uniformly coated, the process steps and the production cost are reduced, the occurrence of side reactions is reduced, and the cycling stability of the material is improved.)

1. A water washing sanding coating method for a positive electrode material is characterized by comprising the following steps: and mixing and washing the positive electrode particles and the coating agent, and sanding while washing to coat the coating agent on the surfaces of the positive electrode particles.

2. The water washing and sanding coating method as defined in claim 1, wherein the coating agent comprises aluminum oxide and/or cobalt oxide;

preferably, the mass ratio of the coating agent to the positive electrode particles is (0.001-0.003): 1.

3. The water washing sanding coating method according to claim 1 or 2, wherein the mass ratio of the mixture of the positive electrode particles and the coating agent to water in the water washing process is 1 (1-1.5);

preferably, the sanding process is performed under stirring conditions;

preferably, the stirring speed in the sanding process is 100-300 r/min;

preferably, the sanding time is 30-60 min.

4. A preparation method of a positive electrode material with a coating layer is characterized by comprising the following steps:

mixing the positive electrode precursor with a lithium source, calcining to obtain positive electrode particles, coating the surfaces of the positive electrode particles by using the water washing sand grinding coating method of any one of claims 1 to 3, and drying and roasting to obtain the positive electrode material with a coating layer.

5. The preparation method according to claim 4, wherein the positive electrode precursor is a high nickel positive electrode precursor;

preferably, the positive electrode precursor is a high-nickel ternary positive electrode precursor or a high-nickel quaternary positive electrode precursor, and more preferably, the high-nickel quaternary positive electrode precursor.

6. The preparation method according to claim 5, wherein the chemical formula of the high-nickel quaternary positive electrode precursor is Ni_xCo_yMn_zAl_(1-x-y-z)(OH)₂Wherein x is more than or equal to 0.9 and less than 1, y is more than 0 and less than or equal to 0.07, and z is more than 0 and less than 0.03;

preferably, the lithium source and the high-nickel quaternary positive electrode precursor are mixed according to the proportion of Li (Ni + Co + Mn + Al) (1-1.05): 1;

preferably, the calcination temperature is 650-800 ℃.

7. The preparation method according to any one of claims 4 to 6, wherein the drying temperature is 80 to 150 ℃;

preferably, the drying time is 5-15 h;

preferably, the roasting temperature is 300-500 ℃.

8. A positive electrode material having a coating layer, characterized in that the positive electrode material is produced by the production method according to any one of claims 4 to 7;

the positive electrode material comprises positive electrode particles and a coating layer coated on the surfaces of the positive electrode particles.

9. The positive electrode material as claimed in claim 8, wherein the positive electrode particles are a high nickel positive electrode material;

preferably, the positive electrode particles are a high-nickel ternary positive electrode material or a high-nickel quaternary positive electrode material, and further preferably are a high-nickel quaternary positive electrode material;

preferably, the chemical general formula of the high-nickel quaternary positive electrode material is LiNi_xCo_yMn_zAl_(1-x-y-z)O₂Wherein x is more than or equal to 0.9 and less than 1, y is more than 0 and less than or equal to 0.07, and z is more than 0 and less than 0.03.

10. A battery comprising a positive electrode, a negative electrode and a separator, wherein the positive electrode comprises the positive electrode material having a coating layer according to claim 8 or 9.

Technical Field

The invention belongs to the technical field of lithium batteries, and relates to a water-washing sanding coating method for a positive electrode material, a preparation method, the positive electrode material and a battery.

Background

Lithium ion batteries have become the most widely used electrochemical power source at present, and the most representative of such batteries is lithium secondary batteries (LIBs) which generate electric energy by the change of chemical potential when lithium ions in a positive electrode and a negative electrode are intercalated and deintercalated. The positive electrode material has a direct leading effect on the performance of LIBs, and therefore, many researchers are dedicated to realizing a positive electrode material which has a large capacity, a fast charge/discharge speed and a long cycle life and can reversibly intercalate and deintercalate lithium ions. Currently, high nickel materials are considered to be the most promising candidate materials because they can increase the specific capacity of lithium ion batteries by increasing the nickel content. However, the resulting poor cycling stability of lithium ion batteries may hinder the success of this approach.

The high-nickel lithium ion battery anode material becomes a research hotspot by virtue of the advantages of high specific capacity, low cost, excellent safety and the like, and is considered to be a lithium ion power battery anode material with great application prospect. However, because the high nickel material precursor has a high pH value during synthesis and a low primary sintering temperature, the content of free lithium, i.e., residual alkali (lithium oxide, lithium carbonate, lithium hydroxide) on the surface of the high nickel positive electrode material is high, and lithium hydroxide is mainly used and is easy to absorb water and damp. For the treatment of the residual alkali, a common method is to uniformly mix deionized water and a high-nickel anode material according to a certain proportion, considering that the solubility of the residual alkali at a low temperature is higher than the normal temperature, so the residual alkali floating on the surface of the high-nickel anode material is dissolved in the water as much as possible by stirring at a low temperature of 5-10 ℃, then filtering is carried out, and a filter element is dried to remove the water in the high-nickel anode material, so that the purpose of reducing the residual alkali is achieved.

CN112194200A discloses a preparation method of a high-nickel cathode material with low residual alkali, high compaction and uniform coating layer, which comprises the following steps: s1, uniformly mixing a large-particle high-nickel polycrystal precursor, lithium hydroxide and a doping agent, and sintering to obtain a large-particle high-nickel polycrystal primary sintering material; s2, uniformly mixing the small-particle high-nickel polycrystal precursor, lithium hydroxide and a doping agent, and sintering to obtain a small-particle high-nickel polycrystal primary sintering material; s3, carrying out wet mixing reaction on the large and small-particle high-nickel polycrystal primary sintering material, lithium hydroxide and soluble salt, and then carrying out filter pressing and drying to obtain a mixture; and S4, uniformly mixing the mixture and the coating agent, then carrying out secondary calcination, crushing, sieving and demagnetizing to obtain the high-nickel anode material with low residual alkali, high compaction and uniform coating layer.

CN110828807A provides a method for reducing the surface alkalinity of a high-nickel anode material, namely, an alcohol solution of lithium salt and manganese salt mixed according to a certain molar ratio is mixed with a high-nickel ternary mixture, and the mixture is dried and sintered to obtain Li_xMnO₂And (3) a coated high-nickel cathode material.

CN112186157A discloses a water washing method of a high-nickel anode material, a product and application thereof, wherein the water washing method comprises the steps of mixing the high-nickel anode material with a phosphate solution with the concentration of 0.1-1 mol/L, reacting, and sintering to obtain the water-washed high-nickel anode material; phosphate reacts with high-nickel anode material surface residual alkali to generate lithium phosphate precipitate and adheres to high-nickel anode material surface in the washing process, a lithium phosphate coating layer is formed through subsequent sintering, and partial lithium phosphate can permeate into the material surface layer and lattice gaps of deep filling materials on the surface, the surface is modified, the coating is more compact, so that the structural stability and the thermal stability of the anode material are improved, and the double effects of removing the residual alkali and improving the material stability through washing are realized.

The quaternary polycrystalline material in the high nickel material is compared with the ternary positive electrode materialThe material has more advantages in safety and cycling stability, and is one of the most promising materials at present. However, the current way of reducing residual alkali of the high-nickel quaternary positive electrode material is mainly by a water washing process, but after the water washing, lithium residues are removed, lithium ions in crystal lattices have larger concentration difference with lithium ions outside the crystal lattices, the material is more prone to undergoing a delithiation reaction without electron transfer, and then Ni is more prone to occurring³⁺/Ni²⁺The material after water washing has rough surface, large specific surface area, large contact area with the electrolyte and more severe side reaction. In order to solve the problem, the surface of the material is coated in a common modification mode, but for the high-nickel quaternary cathode material, dry-mixing coating can cause uneven coating on the surface of the material, and a one-step process is added, so that the production cost is increased. Consequently this patent adopts cobalt oxide and aluminium oxide to carry out washing sanding cladding to high nickel cathode material, can reduce cathode material alkali residue through the washing, prevents that the jelly form condition from appearing in the homogenate, and sanding cladding cobalt aluminium both can improve material conductivity and can also play the effect of protective layer, and the side reaction that reduces cathode material and electrolyte takes place. The one-step process not only has the function of reducing residual alkali, but also can uniformly coat the anode material, and simultaneously reduces the process steps and cost, reduces the occurrence of side reactions and improves the cycling stability of the material.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a water washing sanding coating method for a positive electrode material, a preparation method, the positive electrode material and a battery, wherein coating is completed simultaneously in the process of washing positive electrode particles, the traditional two-step operation is integrated into one-step operation, so that the residual alkali is reduced, the positive electrode particles can be uniformly coated, the process steps and the production cost are reduced, the occurrence of side reactions is reduced, and the cycle stability of the material is improved.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the invention provides a water washing sanding coating method for a positive electrode material, which comprises the following steps: and mixing and washing the positive electrode particles and the coating agent, and sanding while washing to coat the coating agent on the surfaces of the positive electrode particles.

The invention provides a washing and sanding coating method for a positive electrode material, which is used for simultaneously finishing coating in the process of washing positive electrode particles, integrates the traditional two-step operation into one-step operation, plays a role in reducing residual alkali, can uniformly coat the positive electrode particles, reduces the process steps and the production cost, reduces the occurrence of side reactions and improves the cycling stability of the material.

As a preferred embodiment of the present invention, the coating agent comprises alumina and/or cobalt oxide.

According to the invention, cobalt oxide and/or aluminum oxide are used for water washing and sanding coating of the positive electrode particles, residual alkali on the surfaces of the positive electrode particles can be reduced through water washing, the jelly-like condition of homogenate is prevented, the cobalt aluminum coated by sanding can improve the conductivity of the material and can also play a role of a protective layer, and the occurrence of side reactions of the positive electrode particles and electrolyte is reduced.

Preferably, the mass ratio of the alumina to the positive electrode particles is (0.001-0.003): 1, and may be, for example, 0.001:1, 0.0012:1, 0.0014:1, 0.0016:1, 0.0018:1, 0.002:1, 0.0022:1, 0.0024:1, 0.0026:1, 0.0028:1, or 0.003:1, but is not limited to the recited values, and other values not recited in the range of values are also applicable.

Preferably, the mass ratio of the cobalt oxide to the positive electrode particles is (0.001-0.003): 1, and may be, for example, 0.001:1, 0.0012:1, 0.0014:1, 0.0016:1, 0.0018:1, 0.002:1, 0.0022:1, 0.0024:1, 0.0026:1, 0.0028:1, or 0.003:1, but is not limited to the enumerated values, and other unrecited values within the numerical range are also applicable.

In a preferred embodiment of the present invention, the mass ratio of the mixture of the positive electrode particles and the coating agent to water in the washing process is 1 (1 to 1.5), and may be, for example, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4 or 1:1.5, but not limited to the above-mentioned values, and other values not listed in the above-mentioned range are also applicable.

According to the invention, after the original two steps are integrated into one step, the technological parameters of the washing and sanding operations are correspondingly adjusted, so that the washing process and the sanding process are matched to realize uniform coating of the anode particles. Specifically, for the water washing process, the mass ratio of the mixture of the positive electrode particles and the coating agent to water is limited to 1 (1-1.5), and when the ratio of the positive electrode particles to the coating agent to water is beyond the range, the solution is too thin due to too high water amount, the stirring is not uniform, and the later-stage drying time is longer; when the ratio of the alkali to the alkali is lower than the range, the water washing effect is poor due to the fact that the water amount is too low, residual alkali cannot be completely dissolved in the water to be washed out, the solution is thick, and the sanding difficulty is increased.

Preferably, the sanding process is performed under agitation.

Preferably, the stirring speed of the sanding process is 100 to 300r/min, such as 100r/min, 120r/min, 140r/min, 160r/min, 180r/min, 200r/min, 220r/min, 240r/min, 260r/min, 280r/min or 300r/min, but is not limited to the recited values, and other values not recited in the range of values are equally applicable.

The stirring rotating speed in the sanding process is specially limited, the residual alkali amount can be further reduced by matching with distilled water in a proper proportion for washing in the range, and when the stirring rotating speed exceeds 300r/min, the particles are seriously crushed due to overlarge grinding pressure; when the stirring speed is lower than 100r/min, the particles are not uniformly dispersed due to the lower speed, resulting in non-uniform mixing.

Preferably, the sanding time is 30-60 min, for example 30min, 32min, 34min, 36min, 38min, 40min, 42min, 44min, 46min, 48min, 50min, 52min, 54min, 56min, 58min or 60min, but is not limited to the recited values, and other values not recited in this range of values are equally applicable.

In a second aspect, the present invention provides a method for preparing a positive electrode material having a coating layer, the method comprising:

the positive electrode precursor is mixed with a lithium source and then calcined to obtain positive electrode particles, the surfaces of the positive electrode particles are coated by adopting the washing, sanding and coating method of the first aspect, and then the positive electrode material with the coating layer is obtained after drying and roasting.

As a preferable technical scheme of the invention, the positive electrode precursor is a high-nickel positive electrode precursor.

Preferably, the positive electrode precursor is a high-nickel ternary positive electrode precursor or a high-nickel quaternary positive electrode precursor, and more preferably, the high-nickel quaternary positive electrode precursor.

As a preferable technical scheme of the invention, the chemical general formula of the high-nickel quaternary positive electrode precursor is Ni_xCo_yMn_zAl_(1-x-y-z)(OH)₂Where 0.9. ltoreq. x < 1, 0. ltoreq. y 0.07, 0. ltoreq. z < 0.03, for example x can be 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98 or 0.99, y can be 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, 0.055 or 0.06, z can be 0.005, 0.01, 0.015, 0.02 or 0.025, but is not limited to the values listed, but other values not listed in this range of values are equally suitable.

Preferably, the lithium source and the high-nickel quaternary positive electrode precursor are mixed in a ratio of Li (Ni + Co + Mn + Al) ═ 1 to 1.05):1, for example, 1:1, 1.005:1, 1.01:1, 1.015:1, 1.02:1, 1.025:1, 1.03:1, 1.035:1, 1.04:1, 1.045:1, or 1.05:1, but not limited to the enumerated values, and other non-enumerated values within this range of values are also applicable.

Preferably, the calcination temperature is 650 to 800 ℃, for example 650 ℃, 660 ℃, 670 ℃, 680 ℃, 690 ℃, 700 ℃, 710 ℃, 720 ℃, 730 ℃, 740 ℃, 750 ℃, 760 ℃, 770 ℃, 780 ℃, 790 ℃ or 800 ℃, but is not limited to the recited values, and other values not recited within the range of values are also applicable.

In a preferred embodiment of the present invention, the drying temperature is 80 to 150 ℃, and may be, for example, 80 ℃, 85 ℃, 90 ℃, 95 ℃, 100 ℃, 105 ℃, 110 ℃, 115 ℃, 120 ℃, 125 ℃, 130 ℃, 135 ℃, 140 ℃, 145 ℃ or 150 ℃, but is not limited to the above-mentioned values, and other values not listed in the above-mentioned range of values are also applicable.

Preferably, the drying time is 5 to 15 hours, for example, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours or 15 hours, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, the baking temperature is 300 to 500 ℃, for example, 300 ℃, 320 ℃, 340 ℃, 360 ℃, 380 ℃, 400 ℃, 420 ℃, 440 ℃, 460 ℃, 480 ℃ or 500 ℃, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.

In a third aspect, the invention provides a cathode material with a coating layer, and the cathode material is prepared by the preparation method of the second aspect.

The positive electrode material comprises positive electrode particles and a coating layer coated on the surfaces of the positive electrode particles.

As a preferable technical scheme of the invention, the positive electrode particles are high-nickel positive electrode materials.

Preferably, the positive electrode particles are a high-nickel ternary positive electrode material or a high-nickel quaternary positive electrode material, and more preferably a high-nickel quaternary positive electrode material.

Preferably, the chemical general formula of the high-nickel quaternary positive electrode material is LiNi_xCo_yMn_zAl_(1-x-y-z)O₂Where 0.9. ltoreq. x < 1, 0. ltoreq. y 0.07, 0. ltoreq. z < 0.03, for example x can be 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98 or 0.99, y can be 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, 0.055 or 0.06, z can be 0.005, 0.01, 0.015, 0.02 or 0.025, but is not limited to the values listed, but other values not listed in this range of values are equally suitable.

In a fourth aspect, the invention provides a battery comprising a positive electrode, a negative electrode and a separator, wherein the positive electrode material with the coating layer of the second aspect is adopted in the positive electrode.

Compared with the prior art, the invention has the beneficial effects that:

the invention provides a washing and sanding coating method for a positive electrode material, which is used for simultaneously finishing coating in the process of washing positive electrode particles, integrates the traditional two-step operation into one-step operation, plays a role in reducing residual alkali, can uniformly coat the positive electrode particles, reduces the process steps and the production cost, reduces the occurrence of side reactions and improves the cycling stability of the material.

Drawings

Fig. 1 is a diagram of charge-discharge specific capacity of a button cell made of the positive electrode material prepared in example 1 of the present invention;

fig. 2 is a graph showing the charge/discharge specific capacity of a button cell made of the positive electrode material prepared in comparative example 1 of the present invention.

Detailed Description

The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.

Example 1

The embodiment provides a preparation method of a cathode material with a coating layer, and the preparation method specifically comprises the following steps:

(1) precursor Ni_0.9Co_0.07Mn_0.02Al_0.01(OH)₂Mixing with LiOH by a dry method according to the proportion of Li (Ni + Co + Mn + Al) to 1.025:1, calcining for 8 hours at 700 ℃ in an oxygen atmosphere after mixing, and then cooling, crushing and sieving to obtain anode particles;

(2) mixing the prepared positive electrode particles, aluminum oxide and cobalt oxide according to the mass ratio of 1:0.001:0.001, mixing the obtained mixture and water according to the mass ratio of 1:1, washing with water, sanding in the washing process, placing in a vacuum drying oven at 100 ℃ for 10 hours after sanding for 60 minutes, drying, taking out, calcining in an air atmosphere at 400 ℃ for 8 hours, cooling and sieving to obtain the positive electrode material with the coating layer.

Example 2

The embodiment provides a preparation method of a cathode material with a coating layer, and the preparation method specifically comprises the following steps:

(1) precursor Ni_0.91Co_0.04Mn_0.025Al_0.025(OH)₂Mixing with LiOH by a dry method according to the proportion of Li (Ni + Co + Mn + Al) to 1:1, calcining for 8 hours at 650 ℃ in an oxygen atmosphere after mixing, and then cooling, crushing and sieving to obtain anode particles;

(2) mixing the prepared positive electrode particles, aluminum oxide and cobalt oxide according to the mass ratio of 1:0.0015:0.0015, mixing the obtained mixture and water according to the mass ratio of 1:1, washing with water, sanding in the washing process, setting the sanding speed at 100r/min, standing in a vacuum drying oven at 80 ℃ for 15h after sanding for 60min, drying, taking out, and calcining in an air atmosphere at 300 ℃ for 8h to obtain the positive electrode material with the coating layer.

Example 3

The embodiment provides a preparation method of a cathode material with a coating layer, and the preparation method specifically comprises the following steps:

(1) precursor Ni_0.92Co_0.05Mn_0.02Al_0.01(OH)₂Mixing with LiOH by a dry method according to the proportion of Li (Ni + Co + Mn + Al) to 1.02:1, calcining for 8 hours at 680 ℃ in an oxygen atmosphere after mixing, and then cooling, crushing and sieving to obtain anode particles;

(2) mixing the prepared positive electrode particles, aluminum oxide and cobalt oxide according to the mass ratio of 1:0.002:0.002, mixing the obtained mixture with water according to the mass ratio of 1:1, washing with water, sanding in the washing process, placing in a vacuum drying oven at 100 ℃ for 13h after sanding for 50min, drying, taking out, and calcining in an air atmosphere at 350 ℃ for 8h to obtain the positive electrode material with the coating layer.

Example 4

The embodiment provides a preparation method of a cathode material with a coating layer, and the preparation method specifically comprises the following steps:

(1) precursor Ni_0.95Co_0.03Mn_0.015Al_0.005(OH)₂Dry mixing with LiOH at Li (Ni + Co + Mn + Al) ratio of 1.03:1Calcining for 8 hours at 750 ℃ in an oxygen atmosphere after mixing, and then cooling, crushing and sieving to obtain anode particles;

(2) mixing the prepared positive electrode particles, aluminum oxide and cobalt oxide according to the mass ratio of 1:0.0025:0.0025, mixing the obtained mixture and water according to the mass ratio of 1:1, washing with water, sanding in the washing process, placing in a vacuum drying oven at 120 ℃ for 10h after sanding for 45min, drying, taking out, and calcining in an air atmosphere at 400 ℃ for 8h to obtain the positive electrode material with the coating layer.

Example 5

The embodiment provides a preparation method of a cathode material with a coating layer, and the preparation method specifically comprises the following steps:

(1) precursor Ni_0.96Co_0.02Mn_0.01Al_0.01(OH)₂Mixing with LiOH by a dry method according to the proportion of Li (Ni + Co + Mn + Al) to 1.04:1, calcining for 8 hours at 780 ℃ in an oxygen atmosphere after mixing, and then cooling, crushing and sieving to obtain anode particles;

(2) mixing the prepared positive electrode particles, aluminum oxide and cobalt oxide according to the mass ratio of 1:0.003:0.003, mixing the obtained mixture and water according to the mass ratio of 1:1, washing with water, sanding in the washing process, placing in a vacuum drying oven at 140 ℃ for 7h after sanding treatment for 40min, drying, taking out, and calcining in an air atmosphere at 450 ℃ for 8h to obtain the positive electrode material with the coating layer.

Example 6

The embodiment provides a preparation method of a cathode material with a coating layer, and the preparation method specifically comprises the following steps:

(1) precursor Ni_0.98Co_0.01Mn_0.005Al_0.005(OH)₂Mixing with LiOH by a dry method according to the proportion of Li (Ni + Co + Mn + Al) to 1.05:1, calcining for 8 hours at 800 ℃ in an oxygen atmosphere after mixing, and then cooling, crushing and sieving to obtain anode particles;

(2) mixing the prepared positive electrode particles, aluminum oxide and cobalt oxide according to the mass ratio of 1:0.001:0.002, mixing the obtained mixture and water according to the mass ratio of 1:1, washing with water, sanding in the washing process, setting the sanding at the rotating speed of 300r/min, standing in a vacuum drying oven at 150 ℃ for 5h after sanding for 30min, drying, taking out, and calcining in the air atmosphere at 500 ℃ for 8h to obtain the positive electrode material with the coating layer.

Example 7

This example provides a method for preparing a cathode material with a coating layer, which is different from example 1 in that in step (2), the mass ratio of the mixture to water is 1:2, and other process parameters and operation steps are exactly the same as those in example 1.

Example 8

This example provides a method for preparing a cathode material with a coating layer, which is different from example 1 in that in step (2), the mass ratio of the mixture to water is 1:0.5, and other process parameters and operation steps are exactly the same as those in example 1.

Example 9

This example provides a method for preparing a positive electrode material with a coating layer, which is different from example 1 in that in step (2), the sanding speed is 80r/min, and other process parameters and operation steps are exactly the same as those in example 1.

Example 10

This example provides a method for preparing a positive electrode material with a coating layer, which is different from example 1 in that in step (2), the sanding speed is 350r/min, and other process parameters and operation steps are exactly the same as those in example 1.

Comparative example 1

The comparative example provides a preparation method of a positive electrode material with a coating layer, and the preparation method specifically comprises the following steps:

(1) precursor Ni_0.9Co_0.07Mn_0.02Al_0.01O₂Mixing with LiOH by a dry method according to the proportion of Li (Ni + Co + Mn + Al) to 1.025:1, calcining for 8 hours at 700 ℃ in an oxygen atmosphere after mixing, and then cooling, crushing and sieving to obtain anode particles;

(2) mixing the prepared positive electrode particles with distilled water according to the weight ratio of 1:1, mixing and washing with water, stirring at the rotating speed of 200r/min for 60min, and then drying in a vacuum drying oven at 100 ℃ for 10 h;

(3) the positive electrode particles after washing are dry-mixed with alumina and cobalt oxide according to the mass ratio of 1:0.001:0.001, and the mixture is stirred for 60min at the rotating speed of 200r/min, so that the alumina and the cobalt oxide are uniformly coated on the surfaces of the positive electrode particles;

(4) and calcining the coated positive electrode particles for 8 hours in an air atmosphere at 400 ℃, and cooling and sieving to obtain the positive electrode material with the coating layer.

The button cell is prepared by adopting the positive electrode materials prepared in the embodiment 1 and the comparative example 1, and the button cell specifically comprises the following steps:

mixing a positive electrode material, a carbon black conductive agent, a binder PVDF and NMP in a mass ratio of 95:2.5:2.5:5 to prepare positive electrode slurry; coating the positive electrode slurry on an aluminum foil with the thickness of 20-40 um, and performing vacuum drying and rolling to obtain a positive electrode plate, wherein the lithium metal plate is used as a negative electrode, the electrolyte ratio is 1.15M LiPF6EC: DMC (1:1 vol%), and the button cell is assembled.

The electrical property test of the anode material adopts a blue battery test system to test at 45 ℃, and the test voltage range is 3V-4.3V; the button cell was tested for specific charge capacity, specific discharge capacity, first effect, and 50-cycle capacity retention rate, respectively, and the test results are shown in table 1. Among them, a charge-discharge specific capacity map of example 1 is shown in fig. 1, and a charge-discharge specific capacity map of comparative example 1 is shown in fig. 2.

TABLE 1

As can be seen from the test data of example 1 and comparative example 1, the button cell prepared in example 1 has higher capacity, first effect and cycle capacity retention rate, because the water washing and the sand grinding are integrated into one step in example 1, the sand grinding coating is completed while the water washing is performed, the residual alkali is reduced, and the coating uniformity of the positive electrode particles can be further improved in a wet coating mode, so that various performances of the cell are greatly improved. While comparative example 1 performed water washing and coating separately, dry coating was used to affect the uniformity of coating.

From the test data provided by examples 1, 7 and 8, it can be seen that the capacity, first-pass efficiency and cycle capacity retention of the button cell prepared in examples 7 and 8 are slightly lower than those of example 1, because the addition amount of distilled water is too high or too low during the washing and sanding process of examples 7 and 8, which directly affects the coating effect and further affects the battery performance.

From the test data provided by examples 1, 9 and 10, it can be seen that the capacity, first-pass efficiency and cycle capacity retention of the button cell prepared in examples 9 and 10 are slightly lower than those of example 1, because the coating effect and the battery performance are directly affected by the excessively fast or slow stirring speed during the washing and sanding process of examples 9 and 10.

The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.