Positive electrode lithium supplementing material and preparation method and application thereof

Abstract

The invention provides an anode lithium supplementing material as well as a preparation method and application thereof, belongs to the technical field of lithium ion batteries, and can solve the technical problems of poor air stability and poor conductivity of an anode lithium supplementing agent Li5FeO4 in practical application. The moisture absorption rate of the positive electrode lithium supplementing material is less than or equal to 1ppm / s, and the powder resistivity of the positive electrode lithium supplementing material is less than or equal to 0.05 k omega.cm. According to the invention, the resistivity of Li5FeO4 can be effectively reduced, a more excellent lithium supplement effect is exerted, direct contact between a material and water molecules can be prevented, and the air stability of the lithium supplement agent is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium - ion batteries, and particularly relates to a cathode lithium - supplementing material, a preparation method thereof, and an application thereof. Background Art

[0002] During the first charge - discharge process of a lithium - ion battery, a solid electrolyte interface film (SEI film) will form on the surface of the negative electrode. Although the SEI film helps to improve the stability of the electrode - electrolyte interface, its formation process is an irreversible process, which will continuously consume active lithium, resulting in a decrease in battery capacity, a decrease in Coulombic efficiency, and a deterioration in cycle performance.

[0003] Lithium - supplementing technology is an effective means to solve the above problems, which is mainly divided into two categories: negative - electrode lithium - supplementing and positive - electrode lithium - supplementing. Among them, negative - electrode lithium - supplementing technology includes various lithium - supplementing methods such as physical mixing lithium - supplementing based on metallic lithium, self - discharge lithiation, chemical lithium - supplementing, and electrochemical lithiation. Although negative - electrode lithium - supplementing is simple to operate and has high efficiency, its process is complex and metallic lithium has high activity, resulting in safety risks and being difficult to be applied on a large scale. The positive - electrode lithium - supplementing technology adds a lithium - supplementing material to the positive electrode of a lithium - ion battery. During the battery charging process, the lithium - supplementing material decomposes and releases active lithium to make up for the irreversible loss of active lithium caused by the growth of the negative - electrode SEI film. The positive - electrode lithium - supplementing material has the advantages of relatively stable chemical properties, easy synthesis, low cost, and high lithium - supplementing ability. At the same time, the positive - electrode lithium - supplementing process can better be compatible with the existing lithium - ion battery production process and is more suitable for commercial application.

[0004] Among many positive - electrode lithium - supplementing agents, the lithium - rich metal oxide Li5FeO4 is considered to be a promising lithium - supplementing agent because of its high theoretical specific capacity of up to 867 mAh·g -1 , extremely low discharge capacity, high lithium - supplementing capacity, moderate working voltage, and little impact on the existing battery manufacturing process. However, Li5FeO4 still has significant defects in practical applications: its air stability is poor, it is easy to react with H2O and CO2 in the air, resulting in material deterioration, and its electrical conductivity is poor, which limits the full play of its high lithium - supplementing capacity, making it difficult for Li5FeO4 to be applied on a large scale in lithium - ion batteries.

[0005] Therefore, there is an urgent need to provide a positive - electrode lithium - supplementing material that can solve the above problems. Summary of the Invention

[0006] Aiming at the technical problems of poor air stability and poor electrical conductivity of Li5FeO4 in practical applications, the present invention provides a positive - electrode lithium - supplementing material and a preparation method thereof, which can effectively reduce the resistivity of Li5FeO4, exert a more excellent lithium - supplementing effect, and can prevent the direct contact of the material with water molecules, effectively improving the air stability of the lithium - supplementing agent.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows: a cathode lithium supplement material with a moisture absorption rate ≤ 1 ppm / s and a powder resistivity ≤ 0.05 kΩ·cm.

[0008] In some embodiments, it includes a lithium supplement agent core and a coating layer; wherein, the lithium supplement agent core is Li5FeO4, and the coating layer is obtained by coating a carbon layer on the surface of the lithium-containing core and then performing surface modification on it with a silane coupling agent. By coating a carbon layer on the surface of Li5FeO4 in the present invention, the resistivity of Li5FeO4 can be effectively reduced, and a more excellent lithium supplement effect can be exerted; then, the surface of the carbon-coated Li5FeO4 is modified with a silane coupling agent. The silane coupling agent is chemically bonded to the material surface. The organic functional groups such as aminopropyl and methacryloxy in its molecule have low surface energy and hydrophobicity, and the molecular layer formed by the organic functional groups has a certain steric hindrance, which can prevent the direct contact between the material and water molecules. Therefore, the problem of poor air stability of the lithium supplement agent can be effectively improved, and the storage, transportation and processing performance are improved.

[0009] In some embodiments, the size of the lithium supplement agent core is 1 - 20 μm, and the thickness of the coating layer is 20 - 80 nm.

[0010] On the other hand, the present invention provides a preparation method of a cathode lithium supplement material for preparing the above cathode lithium supplement material, including the step of coating a carbon layer on the surface of Li5FeO4 and then performing surface modification treatment with a silane coupling agent.

[0011] In some embodiments, the step of coating a carbon layer on the surface of Li5FeO4 specifically includes the following steps: placing Li5FeO4 in a chemical vapor deposition furnace, introducing an inert gas, heating to a set temperature, and then introducing an organic gas for carbonization treatment, and then cooling with the furnace to obtain carbon-coated Li5FeO4.

[0012] In some embodiments, the temperature of the carbonization treatment is 500 - 600 °C, the carbonization time is 5 - 40 min, and the organic gas is at least one of acetylene, ethylene, methane, propane, and butane. By performing carbonization treatment under the above conditions to obtain carbon-coated Li5FeO4 in the present invention, the effect of reducing the resistivity of the lithium-rich lithium ferrate powder can be achieved.

[0013] In some embodiments, the surface modification treatment with a silane coupling agent specifically includes the following steps: placing the carbon-coated Li5FeO4 in a silane coupling agent diluted with an organic solvent, mixing evenly and then performing an oil bath reaction, and then performing suction filtration and vacuum drying to obtain the cathode lithium supplement material. Using a silane coupling agent to perform surface modification treatment on the carbon-coated Li5FeO4 has the effect of improving the air stability of the lithium-rich lithium ferrate.

[0014] In some of these embodiments, the silane coupling agent is diluted with an organic solvent to form a solution with a mass fraction of 2-10%, and the organic solvent is at least one of N,N-dimethylpyrrolidone, ethanol, methanol, N,N-dimethylformamide, dimethyl carbonate, and ethylene carbonate.

[0015] In some of these embodiments, the temperature of the oil bath reaction is 60-100 °C, and the heat preservation time is 0.5 h-2 h.

[0016] The present invention also provides a lithium-ion battery, the positive electrode sheet of which is prepared by mixing the positive electrode lithium supplementing material described in any one of claims 1-3 as an additive with a positive electrode active material, a conductive agent, and a binder; wherein, the addition amount of the positive electrode lithium supplementing material is 0.5-5% of the mass of the positive electrode active substance.

[0017] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0018] The positive electrode lithium supplementing material of the present invention can effectively reduce the resistivity of Li5FeO4, exert a more excellent lithium supplementing effect, and can hinder the direct contact between the material and water molecules, effectively improving the air stability of the lithium supplementing agent. By coating a carbon layer on the surface of Li5FeO4, the resistivity of Li5FeO4 can be effectively reduced, and a more excellent lithium supplementing effect can be exerted; then, the surface of the carbon-coated Li5FeO4 is modified with a silane coupling agent. The silane coupling agent is bonded to the material surface through chemical bonds. The organic functional groups such as aminopropyl and methacryloxy in its molecule have low surface energy and hydrophobicity, and the molecular layer formed by the organic functional groups has a certain steric hindrance, which can hinder the direct contact between the material and water molecules. Therefore, the problem of poor air stability of the lithium supplementing agent can be effectively improved, and the storage, transportation, and processing performance are improved. Brief Description of the Drawings

[0019] Figure 1 SEM picture of the positive electrode lithium supplementing material prepared in Example 1 of the present invention;

[0020] Figure 2 Lithium supplementing capacity performance diagram of the positive electrode lithium supplementing material prepared in Example 1 of the present invention. Detailed Description of the Embodiments

[0021] In order to more comprehensively understand the features and technical content of the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the embodiments described below are only a part of the embodiments of the present invention, rather than all the embodiments of the present invention. In the following technical description, for the convenience of explanation, multiple details are provided to provide a full understanding of the disclosed embodiments. However, one or more embodiments can still be implemented without these details. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope claimed by the present invention.

[0022] The embodiments of the present invention provide a cathode lithium supplement material and a preparation method thereof, which can solve the technical problems of poor air stability and poor electrical conductivity of the lithium supplement material.

[0023] The moisture absorption rate of the cathode lithium supplement material of the present invention is ≤1 ppm / s, and the powder resistivity of the cathode lithium supplement material is ≤0.05 kΩ·cm.

[0024] The cathode lithium supplement material of the present invention includes a lithium supplement agent core and a coating layer; wherein, the structural formula of the lithium supplement agent core is Li5FeO4; the coating layer is obtained by coating a carbon layer on the surface of the lithium-containing core and then modifying it with a silane coupling agent. Among them, the size of the lithium supplement agent core is 1-20 μm, and the thickness of the coating layer is 20-80 nm. The carbon layer coating layer of the present invention has good electrical conductivity, can effectively reduce the resistivity of the lithium supplement agent, and play a more excellent lithium supplement effect; after the carbon layer is coated on the surface of the lithium-containing core of the present invention and then modified with a silane coupling agent, a uniform and dense carbon layer coating layer is formed on the surface of the lithium supplement agent, which can effectively isolate the reaction between the lithium supplement agent core and moisture and carbon dioxide, improve the problem of poor air stability of the lithium supplement agent, and enhance the storage, transportation and processing performance.

[0025] The preparation method of the cathode lithium supplement material of the present invention includes the step of coating a carbon layer on the surface of Li5FeO4 and then performing surface modification treatment with a silane coupling agent. By coating a carbon layer on the surface of Li5FeO4, the resistivity of Li5FeO4 can be effectively reduced, and a more excellent lithium supplement effect can be achieved; after coating a carbon layer on the surface of Li5FeO4 and then modifying it with a silane coupling agent, the silane coupling agent is chemically bonded to the surface of the carbon-coated Li5FeO4. The organic functional groups such as aminopropyl and methacryloxy in the silane coupling agent molecule have low surface energy and hydrophobicity, and the molecular layer formed by the organic functional groups has a certain steric hindrance, which can prevent the direct contact between the carbon-coated Li5FeO4 and water molecules, effectively improve the problem of poor air stability of the lithium supplement agent Li5FeO4, and enhance the storage, transportation and processing performance.

[0026] Among them, the steps of coating the surface of Li5FeO4 with a carbon layer specifically include the following steps: placing the Li5FeO4 prepared by the liquid phase method into a chemical vapor deposition furnace, introducing an inert gas, heating to a set temperature, and then introducing an organic gas for carbonization treatment, and then cooling with the furnace to obtain carbon-coated Li5FeO4.

[0027] In the above steps of coating the surface of Li5FeO4 with a carbon layer in the present invention, the inert gas is preferably nitrogen; the organic gas is selected from at least one of acetylene, ethylene, methane, propane, and butane; the temperature of the carbonization treatment is 500-600 °C, and the carbonization time is 5-40 min.

[0028] The above surface modification treatment using a silane coupling agent in the present invention specifically includes the following steps: placing the carbon-coated Li5FeO4 into a silane coupling agent diluted with an organic solvent, mixing evenly and then carrying out an oil bath reaction, followed by filtration and vacuum drying to obtain the cathode lithium supplement material.

[0029] In the above steps of surface modification treatment using a silane coupling agent in the present invention, the organic solvent is selected from at least one of N,N-dimethylpyrrolidone, ethanol, methanol, N,N-dimethylformamide, dimethyl carbonate, and ethylene carbonate; the silane coupling agent is selected from at least one of silane coupling agent KH550 and silane coupling agent KH570; the dilution ratio is 2-10%; the temperature of the oil bath reaction is 60-100 °C, and the holding time is 0.5 h-2 h; the vacuum drying conditions are a temperature of 80-100 °C, a time of 6-8 h, and a vacuum degree of -0.1 MPa.

[0030] The present invention also provides the application of the above cathode lithium supplement material in a lithium-ion battery. The cathode lithium supplement material is used as an additive and mixed with a cathode active material, a conductive agent, and a binder to prepare a cathode sheet; among them, the addition amount of the cathode lithium supplement material is 0.5-5% of the mass of the cathode active substance.

[0031] In order to introduce the cathode lithium supplement material and its preparation method and application provided by the embodiments of the present invention more clearly and in detail, the following will be described in conjunction with specific embodiments. Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art; the test reagents used in the following embodiments are all conventional biochemical reagents unless otherwise specified; the experimental methods in the following embodiments are all conventional experimental methods unless otherwise specified.

[0032] Example 1

[0033] The preparation method of the cathode lithium supplement material in this embodiment specifically includes the following steps:

[0034] Weigh 5 g of Li5FeO4 and spread it evenly on the bottom of the crucible, then place it in a chemical vapor deposition furnace. Purge with nitrogen, heat up to 550 °C, then introduce acetylene, keep it warm for 20 min, and then cool it down with the furnace to obtain carbon-coated Li5FeO4;

[0035] Dilute the silane coupling agent KH550 to 5% with N,N-dimethylpyrrolidone. Take 5 g of carbon-coated Li5FeO4 and add it to 20 mL of the diluted KH550 solution, mix evenly, heat in an oil bath at 80 °C for 1 h, filter by suction, and carry out vacuum drying under the conditions of a temperature of 80 °C, a time of 6 h, and a vacuum degree of -0.1 MPa to obtain the positive electrode lithium supplement material.

[0036] The SEM image and the lithium supplement capacity performance graph of the positive electrode lithium supplement material obtained in Example 1 are respectively as Figure 1 and 2 shown. It can be seen from Figure 1 that the positive electrode lithium supplement material in the embodiment of the present invention has a small particle size and a short lithium ion diffusion path, which is helpful for the extraction of lithium ions; it can be seen from Figure 2 that the charging capacity of the positive electrode lithium supplement material in the embodiment of the present invention can reach 750 + mAh / g, and it has excellent lithium supplement performance.

[0037] Example 2

[0038] The preparation method of the positive electrode lithium supplement material in this example specifically includes the following steps:

[0039] Weigh 5 g of Li5FeO4 and spread it evenly on the bottom of the crucible, then place it in a chemical vapor deposition furnace. Purge with nitrogen, heat up to 550 °C, then introduce acetylene, keep it warm for 20 min, and then cool it down with the furnace to obtain carbon-coated Li5FeO4;

[0040] Dilute the silane coupling agent KH550 to 2% with N,N-dimethylpyrrolidone. Take 5 g of carbon-coated Li5FeO4 and add it to 20 mL of the diluted KH550 solution, mix evenly, heat in an oil bath at 80 °C for 1 h, filter by suction, and carry out vacuum drying under the conditions of a temperature of 80 °C, a time of 6 h, and a vacuum degree of -0.1 MPa to obtain the positive electrode lithium supplement material.

[0041] Example 3

[0042] The preparation method of the positive electrode lithium supplement material in this example specifically includes the following steps:

[0043] Weigh 5 g of Li5FeO4 and spread it evenly on the bottom of the crucible, then place it in a chemical vapor deposition furnace. Purge with nitrogen, heat up to 600 °C, then introduce acetylene, keep it warm for 10 min, and then cool it down with the furnace to obtain carbon-coated Li5FeO4;

[0044] Dilute the silane coupling agent KH550 to 5% with ethanol. Take 5 g of carbon-coated Li5FeO4 and add it to 20 mL of the diluted KH550 solution, mix evenly, perform an oil bath at 80 °C for 1 h, carry out suction filtration, and conduct vacuum drying at a temperature of 80 °C, a time of 6 h, and a vacuum degree of -0.1 MPa to obtain the cathode lithium supplement material.

[0045] Example 4

[0046] The preparation method of the cathode lithium supplement material in this example specifically includes the following steps:

[0047] Weigh 5 g of Li5FeO4, spread it evenly on the bottom of the crucible, then place it in a chemical vapor deposition furnace, purge with nitrogen, heat up to 550 °C, then introduce acetylene, keep the temperature for 20 min, and then cool down with the furnace to obtain carbon-coated Li5FeO4;

[0048] Dilute the silane coupling agent KH570 to 10% with N,N-dimethylpyrrolidone. Take 5 g of carbon-coated Li5FeO4 and add it to 20 mL of the diluted KH570 solution, mix evenly, perform an oil bath at 85 °C for 1 h, carry out suction filtration, and conduct vacuum drying at a temperature of 80 °C, a time of 6 h, and a vacuum degree of -0.1 MPa to obtain the cathode lithium supplement material.

[0049] Comparative Example 1

[0050] The cathode lithium supplement material in this comparative example is Li5FeO4 without any treatment.

[0051] Comparative Example 2

[0052] The preparation method of the cathode lithium supplement material in this comparative example specifically includes the following steps:

[0053] Weigh 5 g of Li5FeO4, spread it evenly on the bottom of the crucible, then place it in a chemical vapor deposition furnace, purge with nitrogen, heat up to 550 °C, then introduce acetylene, keep the temperature for 20 min, and then cool down with the furnace to obtain carbon-coated Li5FeO4.

[0054] Performance Test

[0055] Perform powder resistivity tests on the cathode lithium supplement materials prepared in Examples 1-4 and Comparative Examples 1-2, and the test results are shown in Table 1 respectively.

[0056] Table 1 Powder Resistivity Test Table of Examples 1-4 and Comparative Examples 1-2

[0057] Powder resistivity (kΩ·cm) Example 1 0.015 Example 2 0.021 Example 3 0.009 Example 4 0.012 Comparative Example 1 >10 Comparative Example 2 0.006

[0058] As can be seen from Table 1, compared with Comparative Example 1 and Comparative Example 2, in Examples 1-4, the technical solution of the present application was adopted. After coating the surface of Li5FeO4 with a carbon layer, surface modification treatment was carried out with a silane coupling agent. The introduction of the carbon layer had an obvious improvement effect on reducing the powder resistivity of the lithium supplementing agent material.

[0059] The moisture absorption rates of the cathode lithium supplementing materials prepared in Examples 1-4 and Comparative Examples 1-2 were tested respectively. The specific test method steps were as follows: Take 1 g of each of the samples prepared in Examples 1-4, Comparative Example 1 and Comparative Example 2 and spread them evenly on a watch glass. Control the humidity at 20-25%, and test the moisture absorption rate after placing for 24 h. The test results are shown in Table 2.

[0060] Table 2 Moisture Absorption Rate Test Table of Examples 1-4 and Comparative Examples 1-2

[0061] Moisture absorption rate (ppm / s) Example 1 0.459 Example 2 0.502 Example 3 0.715 Example 4 0.420 Comparative Example 1 4.521 Comparative Example 2 2.47

[0062] As can be seen from Table 2, the moisture absorption rate of Li5FeO4 only coated with a carbon layer in Comparative Example 2 was still as high as 2.47 ppm / s, while the moisture absorption rate of the carbon-coated Li5FeO4 lithium supplementing material after being modified with a silane coupling agent in Examples 1-4 could be reduced to less than 1 ppm / s, indicating that the synergistic effect of surface carbon layer coating and silane coupling agent modification could effectively hinder the reaction of Li5FeO4 with moisture in the air.

[0063] The cathode lithium supplementing materials prepared in Examples 1-4 and Comparative Examples 1-2 were respectively mixed with a conductive agent and a binder to make a cathode sheet, and assembled with a lithium sheet into a half-cell for testing. The stability data in an air atmosphere at a temperature of 25°C and a humidity of 20-25% are shown in Table 3.

[0064] Table 3 Stability Data Table of Examples 1-4 and Comparative Examples 1-2

[0065] Case 24h capacity retention rate (%) Example 1 93.21 Example 2 92.55 Example 3 92.14 Example 4 93.72 Comparative Example 1 51.60 Comparative Example 2 76.45

[0066] As can be seen from Table 3, Comparative Example 1 was Li5FeO4 without any treatment, and its air stability was extremely poor. Under the condition of a humidity of 20-25%, the capacity retention rate after 24 h was only 51.60%; Comparative Example 2 was Li5FeO4 treated with a carbon layer coating, and the capacity retention rate after 24 h could be increased to 76.45%; the 24 h capacity retention rate of the carbon-coated Li5FeO4 lithium supplementing material after being modified with a silane coupling agent in Examples 1-4 could be increased to more than 90%. The above results show that the synergistic effect of carbon layer coating and silane coupling agent modification can effectively improve the air stability of Li5FeO4.

[0067] To further prove the effectiveness of the product of the present invention, the positive electrode lithium supplement materials prepared in Examples 1-4 and Comparative Examples 1-2 were mixed and homogenized with lithium iron phosphate, conductive carbon black, and PVDF at 2 wt% of the positive electrode active material to prepare a positive electrode sheet. Graphite was used as the negative electrode active material to prepare a negative electrode sheet, and a full battery was assembled for testing. The data are shown in Table 4 below.

[0068] Table 4 Data Sheet for Battery Performance Testing of Examples 1-4 and Comparative Examples 1-2

[0069]

[0070]

[0071] As can be seen from Table 4, Examples 1-4 are positive electrode lithium supplement materials prepared according to the preparation method of the present invention. After 100 cycles, the capacity retention rates are all greater than those of Comparative Examples 1-2 and the battery without adding a lithium supplement agent, indicating that the positive electrode lithium supplement materials prepared in Examples 1-4 have more excellent lithium supplement effects when applied to lithium-ion batteries.

[0072] Finally, it should be noted that the present invention is not limited to the above-listed embodiments. The above are only preferred and feasible embodiments of the present invention. The above embodiments are only used to illustrate the technical solutions of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations, modifications, evolutions, and improvements made by those of ordinary skill in the art to the technical solutions of the present invention should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A cathode lithium supplement material, characterized in that, The moisture absorption rate of the positive electrode lithium supplement material is ≤1 ppm / s, and the powder resistivity of the positive electrode lithium supplement material is ≤0.05 kΩ·cm.

2. The cathode lithium supplement material according to claim 1, characterized in that It includes a lithium supplement agent core and a coating layer; among them, the lithium supplement agent core is Li5FeO4, and the coating layer is surface-modified with a silane coupling agent after coating a carbon layer on the surface of the lithium-containing core.

3. The cathode lithium supplement material according to claim 2, wherein The size of the lithium supplement agent core is 1-20 μm, and the thickness of the coating layer is 20-80 nm.

4. A preparation method of a cathode lithium supplement material for preparing the cathode lithium supplement material according to any one of claims 1-3, characterized in that, It includes the step of surface-modifying the surface of Li5FeO4 with a silane coupling agent after coating a carbon layer.

5. The preparation method of the cathode lithium supplement material according to claim 4, characterized in that, The step of coating a carbon layer on the surface of Li5FeO4 specifically includes the following steps: placing Li5FeO4 in a chemical vapor deposition furnace, introducing an inert gas, heating to a set temperature, and then introducing an organic gas for carbonization treatment, and then cooling with the furnace to obtain carbon-coated Li5FeO4.

6. The preparation method of the cathode lithium supplement material according to claim 5, characterized in that, The temperature of the carbonization treatment is 500-600 °C, the carbonization time is 5-40 min, and the organic gas is at least one of acetylene, ethylene, methane, propane, and butane.

7. The preparation method of the cathode lithium supplement material according to claim 4, characterized in that, The surface modification treatment with a silane coupling agent specifically includes the following steps: placing the carbon-coated Li5FeO4 in a silane coupling agent diluted with an organic solvent, mixing evenly and then performing an oil bath reaction, followed by filtration and vacuum drying to obtain the positive electrode lithium supplement material.

8. The preparation method of the cathode lithium supplement material according to claim 7, characterized in that, The dilution ratio of the silane coupling agent with the organic solvent is 2-10%, and the organic solvent is at least one of N,N-dimethylpyrrolidone, ethanol, methanol, N,N-dimethylformamide, dimethyl carbonate, and ethylene carbonate.

9. The preparation method of the cathode lithium supplement material according to claim 7, characterized in that, The temperature of the oil bath reaction is 60-100 °C, and the holding time is 0.5 h-2 h.

10. A lithium-ion battery, characterized in that, The positive electrode sheet is prepared by mixing the positive electrode lithium supplement material described in any one of claims 1-3 as an additive with a positive electrode active material, a conductive agent, and a binder; among them, the addition amount of the positive electrode lithium supplement material is 0.5-5% of the mass of the positive electrode active substance.

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