A modified ternary cathode material and its preparation method

Abstract

The present invention belongs to the technical field of lithium-ion battery electrode materials, and particularly relates to a modified ternary cathode material and a preparation method thereof. By combining a water washing process and adopting a wet coating method, the present invention proposes a preparation method for a modified ternary cathode material with low residual alkali. This method can not only remove lithium impurities such as LiOH and Li2CO3 remaining on the ternary cathode material, but also significantly improve the cycle stability of the ternary cathode material, and has the prospect of industrial production application. In the present invention, surface modification is carried out while washing with water. A metal-containing organic compound is sintered at high temperature to obtain a metal oxide and form a coating layer, and at the same time, metal ions will also penetrate and dope into the interior of the ternary cathode. The surface modification not only reduces the pulverization and fragmentation of NCM particles during cycling, but also effectively stabilizes the crystal structure of NCM, reduces cation mixing and the formation of rock salt structure, thereby improving the electrochemical stability of the electrode.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery electrode materials, and particularly relates to a modified ternary cathode material and a preparation method thereof. Background Art

[0002] Lithium-ion batteries are chemical energy storage devices with high energy conversion efficiency. They have attracted much attention due to their high energy density, low self-discharge, high voltage, no memory effect, long cycle life and other advantages, and are one of the most widely used chemical power sources at present. Among many lithium-ion battery cathode materials, the layered nickel cobalt manganese (NCM) ternary cathode material LiNi x Co y M (1-x-y) O2 has quickly become the first choice for high energy density batteries due to its advantages such as reversible capacity, efficiency ability, and capital cost.

[0003] In the ternary cathode material, nickel is the most important active element. The higher the nickel content, the higher the discharge specific capacity. However, with the increase of nickel content, a series of new problems will also arise, such as unstable surface properties, lithium-nickel mixing, and intergranular microcracks.

[0004] In the prior art, coating and doping are often used to modify the ternary cathode material. When modifying, the ternary cathode material is dry-mixed with nano metal oxide, and then a coating layer is formed by high-temperature sintering and metal ions are doped into the material lattice. An excellent coating material can effectively improve the structural stability of the ternary cathode material, prevent side reactions between the bulk material and the electrolyte, and thus improve the cycle performance and rate performance of the material. Doping of the ternary cathode material can maintain the layered structure of the material during charge and discharge, effectively reduce lithium-nickel mixing, and thus improve the cycle stability. However, the cost of nano metal oxide is relatively high, increasing the production cost of the ternary cathode material.

[0005] In addition, with the increase of nickel content, higher residual alkaline lithium impurities such as LiOH and Li2CO3 will also be formed on the electrode surface. Higher LiOH on the material surface will increase its pH value, resulting in the formation of gel during the electrode processing. In addition, Li2CO3 will generate gas during the cycle, affecting the cycle life and safety performance of the battery. Water washing is an effective method to remove surface residual alkali. However, due to the high sensitivity of nickel-rich ternary cathode to water, after water washing, its storage stability becomes poor, and the clean surface is more easily eroded by the electrolyte to form a rock salt phase passivation structure.

[0006] In the prior art, process methods for improving ternary cathode materials have also been disclosed. For example, Chinese Patent No. CN113488643A discloses a method for surface coating modification of ternary cathode materials for lithium-ion batteries. By depositing an alumina film on the surface of the ternary cathode electrode sheet of a lithium-ion battery, surface coating modification of the ternary cathode materials for lithium-ion batteries is achieved, and it has advantages such as a short preparation cycle and low energy consumption. However, the capacity retention rate of the cathode material prepared by this patent after 1C rate cycling still needs to be improved.

[0007] Based on this, the present invention uses an organoaluminum source as a coating agent to coat the ternary cathode material for lithium-ion batteries (such as NCM), and by adjusting the raw material ratio, process parameters, and specific processes, to achieve the improvement of electrochemical properties such as the capacitance of the prepared modified cathode material. Summary of the Invention

[0008] The purpose of the present invention is to propose a preparation method for a modified low-residual-alkali ternary cathode material by combining a water washing process and adopting a wet coating method in view of the deficiencies existing in the prior art. This method can not only remove lithium impurities such as LiOH and Li2CO3 remaining on the ternary cathode material, but also significantly improve the cycle stability of the ternary cathode material. It is a method with simple process, low cost, convenient operation, and excellent performance, and has the prospect of industrial production application. In addition, the wet coating combined with the water washing process can also combine the water washing and mixing processes in the traditional process, thereby reducing the process cost.

[0009] Furthermore, the present invention also provides a method for dry coating to prepare a modified ternary cathode material. This method directly coats a coating agent on the surface of the ternary cathode material and then performs high-temperature heat treatment to obtain the modified ternary cathode material, so as to overcome the defect of poor cycle stability of the ternary cathode material.

[0010] Furthermore, the application of the modified ternary cathode material in the preparation of lithium-ion batteries is also provided.

[0011] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0012] A method for wet coating to prepare a modified ternary cathode material, comprising the following steps:

[0013] 1) Prepare a coating agent solution;

[0014] 2) Mix the ternary cathode material with the coating agent solution in step 1) in a certain proportion, stir and mix evenly, and then obtain the ternary cathode material coated with the coating agent through suction filtration and drying.

[0015] (3) Place the ternary cathode material coated with the coating agent in step (2) in an atmosphere furnace and sinter it under a pure oxygen atmosphere to obtain a modified ternary cathode material with low residual alkali.

[0016] Furthermore, the coating agent described in step (1) is one or a combination of more of aluminum dihydroxyglycinate, titanium hydroxyacetate, zirconium polyhydroxyacetate, amino polyethylene glycol silane, tetracarbonyl(1,5-cyclooctadiene)tungsten, pentakis(dimethylamino)niobium, niobium 2-ethylhexanoate, and preferably aluminum dihydroxyglycinate.

[0017] Furthermore, the concentration of the coating agent solution prepared in step (1) is 0.05 - 10 mg / mL.

[0018] Furthermore, the ternary cathode material described in step (2) is LiNi x Co y M (1-x-y) O2; where x≥0.30, and M is one or both of Mn and Al elements. Preferably, the ternary cathode material described in step (1) is Li(Ni 0.8 Co 0.1 Mn 0.1 )O2 (abbreviated as NCM811).

[0019] Furthermore, the mass ratio of the ternary cathode material and the coating agent solution described in step (2) is 0.01 - 1:1.

[0020] Furthermore, the specific stirring process in step (2) is to stir at a rotation speed of 200 - 600 rpm for 0.5 - 500 min; preferably, stir at a rotation speed of 400 rpm for 10 min.

[0021] Furthermore, the drying temperature described in step (2) is 50 - 200 °C, and the drying time is 1 - 20 h.

[0022] Furthermore, the sintering temperature described in step (3) is 200 - 900 °C, and the heat preservation time is 1 - 10 h.

[0023] Furthermore, the present invention also provides a method for preparing a modified ternary cathode material by dry coating, including the following steps:

[0024] (1) Mix the coating agent and the ternary cathode material in a certain mass ratio to obtain a coated ternary cathode material;

[0025] (2) Place the coated ternary cathode material in an atmosphere furnace and sinter it under a pure oxygen atmosphere to obtain a modified ternary cathode material.

[0026] Furthermore, the coating agent described in step (1) is one or more compositions selected from aluminum dihydroxyglycinate, titanium hydroxyacetate, zirconium polyhydroxyacetate, amino polyethylene glycol silicon, tetracarbonyl(1,5-cyclooctadiene)tungsten, pentakis(dimethylamino)niobium, and niobium 2-ethylhexanoate, preferably aluminum dihydroxyglycinate.

[0027] Furthermore, the ternary cathode material described in step (1) is LiNi x Co y M (1-x-y) O2; where x≥0.30, and M is one or two of the elements Mn and Al. Preferably, the ternary cathode material described in step (1) is Li(Ni 0.8 Co 0.1 Mn 0.1 )O2 (abbreviated as NCM811).

[0028] Furthermore, the mass ratio of the coating agent to the ternary cathode material described in step (1) is 0.001 - 0.1:1.

[0029] Furthermore, in step (2), the sintering temperature is 200 - 900 °C, and the heat preservation time is 1 - 8 h.

[0030] Furthermore, the method for dry coating to prepare the modified ternary cathode material further includes washing the ternary cathode material with water before coating the ternary cathode material with the coating agent.

[0031] Specifically, the water washing step is as follows:

[0032] Mix the ternary cathode material and deionized water at a mass ratio of 0.01 - 1:1, then stir and wash under the condition of 200 - 600 rpm for 0.5 - 500 min, filter by suction, and finally vacuum dry at a temperature of 50 - 200 °C for 1 - 20 h to obtain the ternary cathode material washed with water.

[0033] Furthermore, the modified ternary cathode material prepared by the above wet coating preparation method or dry coating preparation method of the present invention has good capacitance and charge-discharge performance and can be used to prepare lithium-ion batteries.

[0034] Furthermore, based on a general inventive concept, the present invention also provides the application of the modified ternary cathode material in the preparation of lithium-ion batteries.

[0035] Specifically, the modified ternary cathode material is used to prepare lithium-ion batteries.

[0036] Compared with the prior art, the advantages of the present invention are:

[0037] 1) The wet coating method described in the present invention uses an aqueous solution of the coating agent as a detergent for the ternary cathode to remove lithium impurities such as residual LiOH and Li2CO3 in the ternary cathode. Compared with the aqueous solution washing of the ternary cathode in traditional industrial production, the coating agent provides an alkaline water washing environment to protect the ternary cathode from being eroded by water, thereby reducing the generation of disordered structures on the surface of the ternary cathode.

[0038] 2) The wet coating method described in the present invention can combine the two processes of water washing and coating and mixing in the traditional process, reducing the process flow and production cost. During the coating process, the coating agent is finally coated on the surface of the ternary cathode material through processes such as aqueous solution washing, filtration, and drying coating, making the coating process more uniform compared to the dry coating method.

[0039] 3) In the present invention, surface modification is carried out while washing with water. The metal-containing organic matter is sintered at high temperature to obtain metal oxides and form a coating layer. At the same time, metal ions will also penetrate and dope into the interior of the ternary cathode. Surface modification not only reduces the pulverization and fragmentation of NCM particles during cycling, but also effectively stabilizes the crystal structure of NCM, reduces cation mixing and the formation of rock salt structures, thereby improving the electrochemical stability of the electrode.

[0040] 4) The dry coating method described in the present invention has a simple process and low cost of aluminum dihydroxyglycinate, which is conducive to large-scale production and application. In the dry coating method described in the present invention, aluminum dihydroxyglycinate will form Li3N with surface lithium residues after high-temperature sintering, which has a lithium supplement effect on the ternary cathode material and is conducive to improving the positive-negative electrode matching and cycle stability.

[0041] 5) Existing technologies show that after high-temperature treatment, Al elements can exist on the surface of the ternary cathode material in the form of oxides, and at the same time penetrate and dope into the lattice of the ternary cathode material (NCM811) in the form of Al 3+ Therefore, the dry coating method of the present invention effectively reduces cation mixing after modification, forms a protective layer to hinder the reaction between the ternary cathode and the electrolyte, and improves the electrochemical cycle stability. Description of the Drawings

[0042] Figure 1 SEM image of NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 O2) prepared in Comparative Example 1;

[0043] Figure 2 SEM image of pure water-washed NCM811 prepared in Comparative Example 2;

[0044] Figure 3 SEM image of NCM811 wet-coated with aluminum dihydroxyglycinate prepared in Example 1 before sintering;

[0045] Figure 4 SEM image of the sintered aluminum dihydroxyglycinate wet-coated NCM811 prepared in Example 1;

[0046] Figure 5 Cycling performance graphs of Comparative Example 1, Comparative Example 2, Example 1, Example 2, Example 3, Example 4, and Example 5;

[0047] Figure 6 Cycling performance graphs of Comparative Example 1 and Example 6;

[0048] Figure 7 Cycling performance graphs of Comparative Example 2 and Example 7. Detailed implementation manners

[0049] The following examples will further illustrate the present invention in conjunction with the accompanying drawings. These examples are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and processes are given. However, the protection scope of the present invention is not limited to the following examples.

[0050] For the experimental methods without specific conditions in the following examples, they are usually carried out under conventional conditions. The raw materials and reagents used are all commercially available products without special instructions.

[0051] Both the comparative examples and examples use the Li(Ni 0.8 Co 0.1 Mn 0.1 )O2 ternary cathode material prepared by one-time sintering of the precursor and provided by Tianli Lithium Energy Co., Ltd. in Xinxiang, Henan as the initial material, named one-burn NCM811.

[0052] Comparative Example 1

[0053] Comparative Example 1 uses the one-burn NCM811 ternary cathode material commonly used in traditional industries without any treatment as the cathode material. Specifically, the SEM image of the one-burn NCM811 ternary cathode material in Comparative Example 1 is as shown in Figure 1 . As can be seen from Figure 1 , the surface of the one-burn NCM811 is rough and there are a large number of residual lithium impurities.

[0054] Comparative Example 2

[0055] Comparative Example 2 uses the one-burn NCM811 ternary cathode material commonly used in traditional industries and washes it with deionized water to prepare the cathode material. The specific steps are as follows:

[0056] Mix a fired NCM811 ternary cathode material and deionized water in a mass ratio of 0.2:1, then stir and wash for 2 min under the condition of 400 rpm, filter by suction, and finally vacuum dry at 100 °C for 10 h to obtain the washed fired NCM811 ternary cathode material. The SEM image of the ternary cathode material prepared in Comparative Example 2 is as shown in Figure 2 shown. It can be seen from Figure 2 that the surface of NCM811 is relatively smooth, and no residual lithium impurities can be observed.

[0057] Example 1

[0058] Example 1 provides a preparation method of a modified ternary cathode material. By means of wet coating, using aluminum dihydroxyglycinate as the coating agent, a modified ternary cathode material is prepared. The specific steps are as follows:

[0059] 1) Add aluminum dihydroxyglycinate to deionized water, and stir and dissolve to obtain an aluminum dihydroxyglycinate solution with a concentration of 1.2 mg / mL;

[0060] 2) Mix the fired NCM811 ternary cathode material with the aluminum dihydroxyglycinate solution in step 1) in a mass ratio of 0.2:1, then stir and mix evenly for 10 min under the condition of 400 rpm, filter by suction, and vacuum dry at 100 °C for 10 h to obtain the NCM811 ternary cathode material coated with aluminum dihydroxyglycinate;

[0061] 3) Place the NCM811 ternary cathode material coated with aluminum dihydroxyglycinate in step 2) in an atmosphere furnace, and sinter at 700 °C for 4 h under a pure oxygen atmosphere to obtain a modified low-residual-alkali NCM811 ternary cathode material.

[0062] The SEM image of the NCM811 ternary cathode material coated with aluminum dihydroxyglycinate prepared in step 2) of Example 1 before sintering is as shown in Figure 3 shown, and the SEM image after sintering at 700 °C is as shown in Figure 4 shown. It can be seen from Figure 3 that the surface of the unsintered NCM811 is slightly rough and there is a layer of residue on the surface. It can be seen from Figure 4 that the surface of the sintered NCM811 is relatively smooth.

[0063] Example 2

[0064] Example 2 provides a preparation method of a modified ternary cathode material. By means of wet coating, using aluminum dihydroxyglycinate as the coating agent, a modified ternary cathode material is prepared. The difference between Example 2 and Example 1 is that the concentration of the aluminum dihydroxyglycinate solution prepared in step 1) is 0.5 mg / mL.

[0065] Example 3

[0066] Example 3 provides a method for preparing a modified ternary cathode material. By means of wet coating and using aluminum dihydroxyglycinate as the coating agent, a modified ternary cathode material is prepared. The difference between Example 3 and Example 1 is that the concentration of the aluminum dihydroxyglycinate solution prepared in step 1) is 0.7 mg / mL.

[0067] Example 4

[0068] Example 4 provides a method for preparing a modified ternary cathode material. By means of wet coating and using aluminum dihydroxyglycinate as the coating agent, a modified ternary cathode material is prepared. The difference between Example 4 and Example 1 is that the concentration of the aluminum dihydroxyglycinate solution prepared in step 1) is 1.0 mg / mL.

[0069] Example 5

[0070] Example 4 provides a method for preparing a modified ternary cathode material. By means of wet coating and using aluminum dihydroxyglycinate as the coating agent, a modified ternary cathode material is prepared. The difference between Example 4 and Example 1 is that the concentration of the aluminum dihydroxyglycinate solution prepared in step 1) is 1.5 mg / mL.

[0071] Performance Test 1

[0072] Compare the surface residual lithium content of the products prepared in Examples 1-5 and Comparative Example 1, and use potentiometric titration for testing (for the testing method, see the detection method for residual free lithium content in the ternary cathode material in Patent Document CN109917070A). The test results are shown in Table 1.

[0073] Table 1 Titration data of the residual lithium content of the ternary cathode materials in Comparative Example 1, Example 1, Example 2, Example 3, Example 4 and Example 5.

[0074]

[0075] It can be seen from Table 1 that the surface residual lithium content of Comparative Example 1 is relatively high, and the residual lithium mass fractions are Li2CO3 (0.711%) and LiOH (1.034%) respectively. In contrast, the surface residual lithium content of Examples 1-5 is less, the Li2CO3 content is less than 0.45% for all, and the LiOH content is less than 0.4% for all. The results in Table 1 show that the wet coating method of the present invention can significantly reduce the LiOH and Li2CO3 content on the surface of NCM811.

[0076] Compare the cycling performance of the products prepared in Examples 1-5 and Comparative Example 1. The cycling performance test was carried out by assembling into a CR2032 coin cell and performing constant current charge and discharge between 3 and 4.8 V. The specific preparation method is as follows:

[0077] According to the mass ratio of active material (the prepared modified ternary cathode material): conductive agent (Super P): binder (PVDF) of 8:1:1, it was mixed evenly with N-methylpyrrolidone (NMP) as the solvent. After coating, it was vacuum dried at 120 °C for 12 h to obtain the electrode sheet. Using the electrode sheet as the working electrode, a lithium metal sheet as the counter electrode, a polypropylene membrane as the separator, and 1 M LiPF6 in EC:EMC:DMC = 1:1:1 as the electrolyte, a CR2032 coin cell was assembled for constant current charge and discharge tests.

[0078] The results are shown in Table 1 and Figure 5 as shown Figure 5 is the cycling curve at 1C rate, Figure 5 The initial discharge specific capacity at 1C rate and the Coulombic efficiency after 200 cycles are shown in Table 1.

[0079] From Table 1 and Figure 5 it can be obtained that the initial discharge specific capacity of Comparative Example 1 was 162.38 mAh / g, and the capacity retention rate after 200 cycles was 91.50%. The initial discharge specific capacity of Comparative Example 2 did not change significantly compared with Comparative Example 1, but the capacity retention rate after 200 cycles was only 9.44%.

[0080] Compared with Comparative Example 1 and Comparative Example 2, Examples 1-5 had a greater increase in the initial discharge specific capacity. After 200 cycles, the discharge specific capacities of Examples 1-5 were much higher than that of Comparative Example 2. In particular, the capacity retention rates of Examples 1 and 5 exceeded that of Comparative Example 1. The above results show that the wet coating method of the present invention can improve the cycling stability of the NCM811 electrode while removing residual lithium salts.

[0081] Example 6

[0082] Example 6 provides a preparation method of a modified ternary cathode material. By using a dry coating method and using aluminum dihydroxyglycinate as the coating agent, a modified ternary cathode material was prepared. The specific steps are as follows:

[0083] (1) Mix aluminum dihydroxyglycinate with the calcined NCM811 ternary cathode material at a mass ratio of 0.006:1, and stir and mix evenly at 300 rpm for 2 h to obtain the NCM811 ternary cathode material coated with aluminum dihydroxyglycinate;

[0084] (2) Place the aluminum dihydroxyglycinate-coated NCM811 ternary cathode material obtained in step (1) in an atmosphere furnace and sinter it at 700 °C for 4 h under a pure oxygen atmosphere to obtain a modified low-residual-alkali NCM811 ternary cathode material.

[0085] Example 7

[0086] Example 7 provides a method for preparing a modified ternary cathode material. By using a dry coating method and taking aluminum dihydroxyglycinate as a coating agent, a modified ternary cathode material is prepared. The specific steps are as follows:

[0087] (1) Mix the first-fired NCM811 ternary cathode material and deionized water at a mass ratio of 0.2:1, then stir and mix evenly for 2 min under the condition of 400 rpm, filter by suction, and finally vacuum dry at 100 °C for 10 h to obtain the first-fired NCM811 ternary cathode material washed with water;

[0088] (2) Mix the first-fired NCM811 ternary cathode material washed with water in step (1) and aluminum dihydroxyglycinate at a mass ratio of 1:0.006, and stir and mix evenly for 3 h under the condition of 300 rpm to obtain an aluminum dihydroxyglycinate-coated NCM811 ternary cathode material;

[0089] (3) Place the aluminum dihydroxyglycinate-coated NCM811 ternary cathode material obtained in step (2) in an atmosphere furnace and sinter it at 700 °C for 4 h under a pure oxygen atmosphere to obtain a modified low-residual-alkali NCM811 ternary cathode material.

[0090] Performance Test 2

[0091] Compare the cycle performance of the products prepared in Comparative Examples 6-7 and Comparative Example 1. The cycle performance test is carried out by assembling into a CR2032 coin cell and performing constant current charge and discharge between 3 and 4.8 V (the preparation method is referred to Performance Test 1). The results are shown in Table 2 and Figure 6 、 Figure 7 as shown.

[0092] Table 2 Initial specific capacity and capacity retention rate at 200 cycles when cycling at 1C for Comparative Example 1, Comparative Example 2, Example 6, and Example 7.

[0093]

[0094] Compare the cycle performance of Example 6 and Comparative Example 1. The cycle performance curve at a 1C rate is as shown in Figure 6 as shown. Figure 6 The initial discharge specific capacity and Coulombic efficiency after 200 cycles at the corresponding 1C rate in the figure are shown in Table 2.

[0095] The initial discharge specific capacity of Comparative Example 1 was 162.38 mAh / g, lower than 173.39 mAh / g of Example 6. The capacity retention rate of Comparative Example 1 after 200 cycles was 91.50%, while that of Example 6 increased to 100%. The results show that the method of dry coating with aluminum dihydroxyglycinate can effectively improve the cycle stability of NCM811.

[0096] Comparing the cycle performance of Example 7 and Comparative Example 2, the cycling curves at 1C rate are as Figure 7 shown. Figure 7 The initial charge specific capacity at the corresponding 1C rate and the Coulombic efficiency after 200 cycles are shown in Table 2.

[0097] The initial discharge specific capacity of Comparative Example 2 was 177.87 mAh / g, slightly lower than 182.39 mAh / g of Example 7. The capacity retention rate of Example 7 after 200 cycles was 97.26%, much higher than 9.44% of Example 2. The results show that dry coating with aluminum dihydroxyglycinate can greatly promote the improvement of the cycle stability of water-washed NCM811.

[0098] The preparation method adopted for the modified ternary cathode material of the present invention not only simplifies the preparation method of the ternary cathode material in the prior art but also improves its overall performance, has good application value, and is suitable for industrialized popularization and application.

[0099] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. Application of a modified ternary cathode material prepared by wet coating in the preparation of CR2032 button lithium-ion batteries, characterized in that, The modified ternary cathode material is made into a CR2032 coin-type lithium-ion battery, which has good capacitance and charge-discharge performance; According to the mass ratio of modified ternary cathode material: conductive agent Super P: binder PVDF of 8:1:1, it is mixed evenly with N-methylpyrrolidone as the solvent, vacuum-dried at 120 °C for 12 h after coating to obtain a pole piece. Using the pole piece as the working electrode, a metal lithium sheet as the counter electrode, a polypropylene film as the separator, and 1 M LiPF6 in EC:EMC:DMC = 1:1:1 as the electrolyte to assemble a CR2032 coin-type battery; The modified ternary cathode material is prepared through the following steps: 1) Prepare a coating agent solution; 2) Mix the ternary cathode material with the coating agent solution in step 1) in a certain proportion, stir and mix evenly, and then obtain the ternary cathode material coated with the coating agent through suction filtration and drying; 3) Place the ternary cathode material coated with the coating agent in step 2) in an atmosphere furnace and sinter it under a pure oxygen atmosphere to obtain a modified low-residual-alkali ternary cathode material; The coating agent described in step 1) is aluminum dihydroxyglycinate; the concentration of the coating agent solution prepared in step 1) is 0.05 - 10 mg / mL; The ternary cathode material described in step 2) is Li(Ni 0.8 Co 0.1 Mn 0.1 )O2; The mass ratio of the ternary cathode material and the coating agent solution described in step 2) is 0.01 - 1:1; The specific stirring process in step 2) is to stir at a rotation speed of 200 - 600 rpm for 0.5 - 500 min; The drying temperature in step 2) is 50 - 200 °C, and the drying time is 1 - 20 h; The sintering temperature in step 3) is 200 - 900 °C, and the heat preservation time is 1 - 10 h.

2. The application according to claim 1, characterized in that The concentration of the coating agent solution prepared in step 1) is 1.2 mg / mL, 0.5 mg / mL, 0.7 mg / mL, 1.0 mg / mL or 1.5 mg / mL; The mass ratio of the ternary cathode material and the coating agent solution described in step 2) is 0.2:1; The sintering temperature in step 3) is 700 °C, and the heat preservation time is 4 h.

3. Application of the modified ternary cathode material prepared by dry coating in the preparation of CR2032 button lithium-ion batteries, characterized in that, The modified ternary cathode material is made into a CR2032 coin-type lithium-ion battery, which has good capacitance and charge-discharge performance; According to the mass ratio of modified ternary cathode material: conductive agent Super P: binder PVDF of 8:1:1, it is mixed evenly with N-methylpyrrolidone as the solvent, vacuum-dried at 120 °C for 12 h after coating to obtain a pole piece. Using the pole piece as the working electrode, a metal lithium sheet as the counter electrode, a polypropylene film as the separator, and 1 M LiPF6 in EC:EMC:DMC = 1:1:1 as the electrolyte to assemble a CR2032 coin-type battery; The modified ternary cathode material is prepared through the following steps: (1) Mix the coating agent and the ternary cathode material in a certain mass ratio to obtain the coated ternary cathode material; (2) Place the coated ternary cathode material in an atmosphere furnace and sinter it under a pure oxygen atmosphere to obtain the modified ternary cathode material; The coating agent described in step (1) is aluminum dihydroxyglycinate; The ternary cathode material described in step (1) is Li(Ni 0.8 Co 0.1 Mn 0.1 )O2; The mass ratio of the coating agent and the ternary cathode material described in step (1) is 0.001 - 0.1:1; In step (2), the sintering temperature is 200~900 °C and the heat preservation time is 1~8 h; In step (1) during mixing, it is stirred and mixed evenly for 2 h under the condition of 300 rpm, or stirred and mixed evenly for 3 h under the condition of 300 rpm.

4. The application according to claim 3, characterized in that, The mass ratio of the coating agent to the ternary cathode material described in step (1) is 0.006:1; The sintering temperature described in step (2) is 700 °C and the heat preservation time is 4 h.

5. The application according to claim 3, characterized in that, Before coating the ternary cathode material with the coating agent, the ternary cathode material is washed with water; the water washing step is as follows: The ternary cathode material and deionized water are mixed at a mass ratio of 0.01~1:1, then stirred and washed under the condition of 200~600 rpm for 0.5~500 min, filtered by suction, and finally vacuum dried at a temperature of 50~200 °C for 1~20 h to obtain the ternary cathode material washed with water.

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