Preparation and application of composite lithium supplement agent

Abstract

The invention relates to the technical field of preparation of a lithium ion battery positive electrode lithium supplement agent, in particular to preparation of a composite lithium supplement agent, which comprises the following steps: dissolving lithium hydroxide and oxalic acid in pure water to prepare a lithium oxalate saturated solution, and adding a metal catalyst; preparing lithium oxalate particles from the lithium oxalate saturated solution containing the metal catalyst through a spray dryer in an inert atmosphere; the lithium oxalate particles are put into a CVD rotary furnace, organic steam is introduced, the organic steam is decomposed through a metal catalyst to generate carbon, and the carbon is deposited on the surface of lithium oxalate; reducing the temperature of the CVD rotary furnace, introducing a silicon source, introducing water vapor, and coating the surface of the material with a SiO2 film; and reducing the temperature of the CVD rotary furnace, introducing a modifier, and carrying out a cross-linking reaction on the modifier and the surface of the material to obtain the final product Li2C2O4 (at) C (at) SiO2 (at) CF3. According to the invention, the defects of lithium oxalate insulation, high decomposition voltage and poor air stability are overcome.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery cathode lithium replenishing agent preparation, and particularly to the preparation and application of a composite lithium replenishing agent. Background Technology

[0002] Irreversible lithium loss (ICL) during battery cycling has become a core bottleneck restricting the improvement of energy density. Studies have shown that the active lithium loss rate of traditional graphite anode batteries reaches 3%-5% after every 100 charge-discharge cycles, leading to battery capacity decay and shortened cycle life. Positive electrode lithium replenishment technology, by compensating for active lithium loss, can improve the battery's initial efficiency to over 95% and extend cycle life by 20%-30%, becoming a key path to breaking through the energy density ceiling.

[0003] Traditional lithium supplementation agents suffer from poor stability and numerous byproducts. Lithium oxalate has become a research hotspot due to its low cost, high theoretical capacity, and residue-free decomposition, but it faces challenges related to high decomposition voltage, insulation, and hygroscopicity. Developing high-performance composite lithium supplementation agent systems to overcome the performance bottlenecks of lithium oxalate is a core research direction for promoting the commercialization of high-energy-density lithium-ion batteries. Summary of the Invention

[0004] In view of this, the present invention provides a method for preparing and applying a composite lithium supplement, which solves the shortcomings of lithium oxalate in terms of insulation, high decomposition voltage and poor air stability.

[0005] To achieve the above objectives, the present invention employs the following technical solution: Preparation of a composite lithium supplement, comprising the following steps:

[0006] S1. Dissolve lithium hydroxide and oxalic acid in pure water to prepare a saturated lithium oxalate solution, and add a metal catalyst;

[0007] S2. Under an inert atmosphere, a saturated lithium oxalate solution containing a metal catalyst is spray-dried to form lithium oxalate particles.

[0008] S3. Lithium oxalate particles are placed in a CVD rotary furnace. Inert gas is first introduced for 20 minutes to purge the furnace and remove air. Then, the temperature is increased to the set first-stage reaction temperature at a rate of 10℃ / min, and the plasma is started. During this process, organic vapor is introduced using inert gas as a carrier gas and reacted for 60 minutes. Under the action of a metal catalyst, the organic vapor decomposes to produce carbon, which is deposited on the surface of lithium oxalate, eventually forming Li2C2O4@C.

[0009] S4. Reduce the temperature of the CVD rotary furnace to the temperature required for the second stage reaction, introduce the silicon source using an inert gas as a carrier gas, and simultaneously introduce water vapor. React for 25 minutes. Under the catalytic action of water, the silicon source forms a SiO2 film, which uniformly coats the material surface, and finally obtains Li2C2O4@C@SiO2.

[0010] S5. Reduce the temperature of the CVD rotary kiln to the temperature required for the third stage reaction, introduce the modifier using an inert gas as a carrier gas, react for 45 minutes, and the modifier undergoes a cross-linking reaction with the surface of Li2C2O4@C@SiO2 to form a fluorosilicone polymer layer containing trifluoromethyl groups, thus obtaining the final product Li2C2O4@C@SiO2@CF3.

[0011] As a further description of the above technical solution:

[0012] The metal catalyst in step S1 is one or more of molybdenum carbide, molybdenum oxide, nickel oxide, iron oxide, and cobalt oxide.

[0013] As a further description of the above technical solution:

[0014] In step S1, the molar ratio of lithium hydroxide to oxalic acid is 2:1, and the pH of the saturated lithium oxalate solution in step S1 is 6.5-7.5.

[0015] As a further description of the above technical solution:

[0016] In step S2, the outlet temperature of the spray dryer is controlled at 110-115℃, and the particle size D50 of the prepared lithium oxalate particles is 4-6μm.

[0017] As a further description of the above technical solution:

[0018] In step S3, the organic vapor is one or more of acetone, cyclohexanone, diethyl ether, and ethanol, and the reaction temperature in the first stage of step S3 is 340-360℃.

[0019] As a further description of the above technical solution:

[0020] In step S4, the silicon source is one or more of TEOS and SiH4, and the reaction temperature in the second stage of step S4 is 240-260℃.

[0021] As a further description of the above technical solution:

[0022] In step S5, the modifier is one or more of FOTS, PFOTS, MTES, and PFPTES, and the reaction temperature in the third stage of step S5 is 180-200℃.

[0023] As a further description of the above technical solution:

[0024] In steps S2, S3, S4, and S5, the inert gas is one or more of nitrogen, argon, and helium.

[0025] A composite lithium replenishing agent material, comprising the above-mentioned composite lithium replenishing agent.

[0026] By employing the above technical solution, the preparation and application of the composite lithium supplement of the present invention have at least the following beneficial effects:

[0027] 1. Compared with existing technologies, the preparation and application of this composite lithium supplement significantly improves its performance by constructing a multilayer composite structure of Li2C2O4@C@SiO2@CF3. The inner lithium oxalate layer provides the lithium source, achieving efficient lithium supplementation. The middle amorphous carbon layer enhances the electronic conductivity of the material, promoting rapid lithium-ion transport. The outer dense SiO2 layer and the outermost fluorosilicone polymer layer reduce interfacial impedance and enhance environmental stability by optimizing interfacial chemical properties, such as hydrophobicity and electrolyte wettability. This design overcomes the performance limitations of single materials and achieves synergistic effects of each layer's function.

[0028] 2. Compared with existing technologies, the preparation and application of this composite lithium supplement utilizes chemical vapor deposition (CVD) technology to achieve multi-layer coating in a CVD rotary furnace. The continuous process and adjustable parameters ensure product consistency. Precise control of temperature, gas flow rate, and reaction time ensures uniform deposition and quality of each material layer. Organic vapors decompose under the catalysis of metal oxides to form an amorphous carbon layer, and a dense SiO2 layer is generated on the carbon layer through a decomposition reaction. Finally, a surface modifier is introduced to form a fluorosilicone polymer containing -CF3 groups. This integrated process not only improves production efficiency but also provides potential for large-scale production, making it suitable for energy storage devices such as lithium-ion batteries, significantly improving battery capacity and cycle stability. Attached Figure Description

[0029] Figure 1 This is a SEM image of Li2C2O4@C@SiO2@CF3 proposed in this invention;

[0030] Figure 2 The image shows the XRD pattern of Li2C2O4@C@SiO2@CF3 proposed in this invention. Detailed Implementation

[0031] Reference Figures 1-2 The present invention provides a method for preparing a composite lithium supplement, comprising the following steps:

[0032] S1. Dissolve lithium hydroxide and oxalic acid in pure water at a molar ratio of 2:1 to prepare a saturated lithium oxalate solution. The pH of the saturated lithium oxalate solution is controlled at 6.5-7.5. One or more of molybdenum carbide, molybdenum oxide, nickel oxide, iron oxide, cobalt oxide, etc. are added as metal catalysts.

[0033] S2. Under an inert atmosphere, a saturated lithium oxalate solution containing a metal catalyst is spray-dried into pellets using a spray dryer. The outlet temperature of the spray dryer is controlled at 110-115℃ to produce lithium oxalate particles with a particle size D50 of 4-6μm.

[0034] S3. Lithium oxalate particles are placed in a CVD rotary furnace. Inert gas is first introduced for 20 minutes to purge the furnace and remove air. Then, the temperature is increased to the set first-stage reaction temperature of 340-360℃ at a rate of 10℃ / min, and the plasma is started. During this process, organic vapor is introduced using inert gas as a carrier gas (inert gas as a support). The organic vapor is one or more of acetone, cyclohexanone, diethyl ether, and ethanol. The reaction is carried out for 60 minutes. Under the action of a metal catalyst, the organic vapor decomposes to produce carbon, which is deposited on the surface of lithium oxalate, and finally forms Li2C2O4@C.

[0035] S4. Reduce the temperature of the CVD rotary furnace to the temperature required for the second stage reaction, 240-260℃. Use an inert gas as a carrier gas to introduce the silicon source, wherein the silicon source is one or more of TEOS and SiH4. At the same time, water vapor is introduced and the reaction is carried out for 25 minutes. Under the catalytic action of water, the silicon source forms a SiO2 film, which is uniformly coated on the material surface, and finally Li2C2O4@C@SiO2 is obtained.

[0036] S5. Lower the temperature of the CVD rotary kiln to the temperature required for the third stage reaction, 180-200℃. Inert gas is used as a carrier gas to introduce the modifier, which is one or more of FOTS, PFOTS, MTES, and PFPTES. The reaction is carried out for 45 minutes. The modifier undergoes a cross-linking reaction with the surface of Li2C2O4@C@SiO2 to form a fluorosilicone polymer layer containing trifluoromethyl (-CF3). The final product Li2C2O4@C@SiO2@CF3 is obtained.

[0037] In the above steps, the inert gas is one or more of nitrogen, argon, and helium.

[0038] A composite lithium replenishing agent material, including the above-mentioned composite lithium replenishing agent, can be directly incorporated into the positive electrode slurry to form an electrode sheet, and then assembled with the negative electrode, separator and electrolyte to form a lithium-ion battery; the composite lithium replenishing agent can improve the battery's initial efficiency and cycle life.

[0039] Example 1:

[0040] Lithium hydroxide and oxalic acid were dissolved in pure water at a molar ratio of 2:1 to prepare a 20 L saturated lithium oxalate solution. The pH of the solution was controlled at 7.15, and 3 wt% molybdenum oxide was added as a metal catalyst.

[0041] A saturated lithium oxalate solution containing a metal catalyst was spray-dried into spherical particles. The process was carried out in a nitrogen atmosphere, with the outlet temperature of the spray dryer controlled at 110℃-115℃. The final particle size D50 was 4.03μm.

[0042] 150g of lithium oxalate particles were placed in a CVD rotary furnace and purged with nitrogen at a flow rate of 300 sccm for 20 min to remove air from the furnace. Subsequently, the furnace was heated to 350℃ at a heating rate of 10℃ / min, and the plasma was adjusted to 45Hz and started. During the reaction, acetone vapor at a flow rate of 60 sccm was introduced as a carrier gas, and the reaction time was 60 min. Under the catalysis of molybdenum oxide, acetone decomposed rapidly to generate carbon, which was deposited on the surface of the lithium oxalate particles, ultimately forming Li₂C₂O₄@C.

[0043] The temperature of the CVD rotary kiln was lowered to 245℃, nitrogen was used as the carrier gas, and 20 sccm of TEOS vapor (nitrogen carrier gas flow rate was 40 sccm) was introduced, while 50 sccm of water vapor was simultaneously introduced. Under these conditions, the reaction was carried out for 25 min, forming a SiO2 film on the lithium oxalate surface, ultimately yielding Li2C2O4@C@SiO2.

[0044] The temperature of the CVD rotary kiln was lowered to 190℃, and FOTS vapor at a flow rate of 40 sccm was introduced using nitrogen as the carrier gas (nitrogen carrier gas flow rate was 60 sccm). The reaction was carried out under these conditions for 45 min, allowing FOTS to undergo a cross-linking reaction with Li2C2O4@C@SiO2, thereby forming a fluorosilicone polymer layer containing trifluoromethyl (-CF3), yielding the final product Li2C2O4@C@SiO2@CF3.

[0045] Example 2:

[0046] Lithium hydroxide and oxalic acid were dissolved in pure water at a molar ratio of 2:1 to prepare a 20 L saturated lithium oxalate solution. The pH of the solution was controlled at 7.15, and 3 wt% molybdenum oxide was added as a metal catalyst.

[0047] A saturated lithium oxalate solution containing a metal catalyst was spray-dried into spherical particles. The process was carried out in a nitrogen atmosphere, with the outlet temperature of the spray dryer controlled at 110℃-115℃. The final particle size D50 was 4.49μm.

[0048] 150g of lithium oxalate particles were placed in a CVD rotary furnace and purged with nitrogen at a flow rate of 300 sccm for 20 min to remove air from the furnace. Subsequently, the furnace was heated to 350℃ at a heating rate of 10℃ / min, and the plasma was adjusted to 45Hz and started. During the reaction, acetone vapor at a flow rate of 60 sccm was introduced as a carrier gas, and the reaction time was 60 min. Under the catalysis of molybdenum oxide, acetone decomposed rapidly to generate carbon, which was deposited on the surface of the lithium oxalate particles, ultimately forming Li₂C₂O₄@C.

[0049] The temperature of the CVD rotary kiln was lowered to 245℃, nitrogen was used as the carrier gas, and 20 sccm of TEOS vapor (nitrogen carrier gas flow rate was 40 sccm) was introduced, while 50 sccm of water vapor was simultaneously introduced. Under these conditions, the reaction was carried out for 25 min, forming a SiO2 film on the lithium oxalate surface, ultimately yielding Li2C2O4@C@SiO2.

[0050] The temperature of the CVD rotary kiln was lowered to 190℃, and FOTS vapor at a flow rate of 40 sccm was introduced using nitrogen as the carrier gas (nitrogen carrier gas flow rate was 60 sccm). The reaction was carried out under these conditions for 45 min, allowing FOTS to undergo a cross-linking reaction with Li2C2O4@C@SiO2, thereby forming a fluorosilicone polymer layer containing trifluoromethyl (-CF3), yielding the final product Li2C2O4@C@SiO2@CF3.

[0051] Example 3:

[0052] Lithium hydroxide and oxalic acid were dissolved in pure water at a molar ratio of 2:1 to prepare a 20 L saturated lithium oxalate solution. The pH of the solution was controlled at 7.15, and 3 wt% molybdenum oxide was added as a metal catalyst.

[0053] A saturated lithium oxalate solution containing a metal catalyst was spray-dried into spherical particles. The process was carried out in a nitrogen atmosphere, with the outlet temperature of the spray dryer controlled at 110℃-115℃. The final particle size D50 was 5.07μm.

[0054] 150g of lithium oxalate particles were placed in a CVD rotary furnace and purged with nitrogen at a flow rate of 300 sccm for 20 min to remove air from the furnace. Subsequently, the furnace was heated to 350℃ at a heating rate of 10℃ / min, and the plasma was adjusted to 45Hz and started. During the reaction, acetone vapor at a flow rate of 60 sccm was introduced as a carrier gas, and the reaction time was 60 min. Under the catalysis of molybdenum oxide, acetone decomposed rapidly to generate carbon, which was deposited on the surface of the lithium oxalate particles, ultimately forming Li₂C₂O₄@C.

[0055] The temperature of the CVD rotary kiln was lowered to 245℃, nitrogen was used as the carrier gas, and 20 sccm of TEOS vapor (nitrogen carrier gas flow rate was 40 sccm) was introduced, while 50 sccm of water vapor was simultaneously introduced. Under these conditions, the reaction was carried out for 25 min, forming a SiO2 film on the lithium oxalate surface, ultimately yielding Li2C2O4@C@SiO2.

[0056] The temperature of the CVD rotary kiln was lowered to 190℃, and FOTS vapor at a flow rate of 40 sccm was introduced using nitrogen as the carrier gas (nitrogen carrier gas flow rate was 60 sccm). The reaction was carried out under these conditions for 45 min, allowing FOTS to undergo a cross-linking reaction with Li2C2O4@C@SiO2, thereby forming a fluorosilicone polymer layer containing trifluoromethyl (-CF3), yielding the final product Li2C2O4@C@SiO2@CF3.

[0057] Example 4:

[0058] Lithium hydroxide and oxalic acid were dissolved in pure water at a molar ratio of 2:1 to prepare a 20 L saturated lithium oxalate solution. The pH of the solution was controlled at 7.15, and 3 wt% molybdenum oxide was added as a metal catalyst.

[0059] A saturated lithium oxalate solution containing a metal catalyst was spray-dried into spherical particles. The process was carried out in a nitrogen atmosphere, with the outlet temperature of the spray dryer controlled at 110℃-115℃. The final particle size D50 was 5.54μm.

[0060] 150g of lithium oxalate particles were placed in a CVD rotary furnace and purged with nitrogen at a flow rate of 300 sccm for 20 min to remove air from the furnace. Subsequently, the furnace was heated to 350℃ at a heating rate of 10℃ / min, and the plasma was adjusted to 45Hz and started. During the reaction, acetone vapor at a flow rate of 60 sccm was introduced as a carrier gas, and the reaction time was 60 min. Under the catalysis of molybdenum oxide, acetone decomposed rapidly to generate carbon, which was deposited on the surface of the lithium oxalate particles, ultimately forming Li₂C₂O₄@C.

[0061] The temperature of the CVD rotary kiln was lowered to 245℃, nitrogen was used as the carrier gas, and 20 sccm of TEOS vapor (nitrogen carrier gas flow rate was 40 sccm) was introduced, while 50 sccm of water vapor was simultaneously introduced. Under these conditions, the reaction was carried out for 25 min, forming a SiO2 film on the lithium oxalate surface, ultimately yielding Li2C2O4@C@SiO2.

[0062] The temperature of the CVD rotary kiln was lowered to 190℃, and FOTS vapor at a flow rate of 40 sccm was introduced using nitrogen as the carrier gas (nitrogen carrier gas flow rate was 60 sccm). The reaction was carried out under these conditions for 45 min, allowing FOTS to undergo a cross-linking reaction with Li2C2O4@C@SiO2, thereby forming a fluorosilicone polymer layer containing trifluoromethyl (-CF3), yielding the final product Li2C2O4@C@SiO2@CF3.

[0063] Example 5:

[0064] Lithium hydroxide and oxalic acid were dissolved in pure water at a molar ratio of 2:1 to prepare a 20 L saturated lithium oxalate solution. The pH of the solution was controlled at 7.15, and 3 wt% molybdenum oxide was added as a metal catalyst.

[0065] A saturated lithium oxalate solution containing a metal catalyst was spray-dried into spherical particles. The process was carried out in a nitrogen atmosphere, with the outlet temperature of the spray dryer controlled at 110℃-115℃. The final particle size D50 was 5.95μm.

[0066] 150g of lithium oxalate particles were placed in a CVD rotary furnace and purged with nitrogen at a flow rate of 300 sccm for 20 min to remove air from the furnace. Subsequently, the furnace was heated to 350℃ at a heating rate of 10℃ / min, and the plasma was adjusted to 45Hz and started. During the reaction, acetone vapor at a flow rate of 60 sccm was introduced as a carrier gas, and the reaction time was 60 min. Under the catalysis of molybdenum oxide, acetone decomposed rapidly to generate carbon, which was deposited on the surface of the lithium oxalate particles, ultimately forming Li₂C₂O₄@C.

[0067] The temperature of the CVD rotary kiln was lowered to 245℃, nitrogen was used as the carrier gas, and 20 sccm of TEOS vapor (nitrogen carrier gas flow rate was 40 sccm) was introduced, while 50 sccm of water vapor was simultaneously introduced. Under these conditions, the reaction was carried out for 25 min, forming a SiO2 film on the lithium oxalate surface, ultimately yielding Li2C2O4@C@SiO2.

[0068] The temperature of the CVD rotary kiln was lowered to 190℃, and FOTS vapor at a flow rate of 40 sccm was introduced using nitrogen as the carrier gas (nitrogen carrier gas flow rate was 60 sccm). The reaction was carried out under these conditions for 45 min, allowing FOTS to undergo a cross-linking reaction with Li2C2O4@C@SiO2, thereby forming a fluorosilicone polymer layer containing trifluoromethyl (-CF3), yielding the final product Li2C2O4@C@SiO2@CF3.

[0069] Comparative Example 1:

[0070] Acidified CNTs, MoO3, and Li2C2O4 were mixed in a mass ratio of 3:3:94 and added to pure water, with the solid content controlled at 20%. The mixture was then milled for 2 hours. After treatment, it was dried under a nitrogen atmosphere at an outlet temperature of 110-115℃ to obtain composite lithium oxalate with a particle size D50 of 5.03 micrometers.

[0071]

[0072] Table 1 shows the test results.

[0073] Working principle: First, lithium hydroxide and oxalic acid are dissolved in water, and lithium oxalate powder is obtained through spray drying. Then, a series of chemical reactions are carried out in a CVD rotary kiln: heating is performed under an inert atmosphere, and organic vapor is introduced to form an amorphous carbon layer on the surface of the lithium oxalate; next, a dense SiO2 layer is generated on the carbon layer through a decomposition reaction; finally, a surface modifier is introduced to form a fluorosilicone polymer containing -CF3 groups. Through these steps, a Li2C2O4@C@SiO2@CF3 composite lithium replenisher is finally prepared. This composite lithium replenisher not only has excellent lithium replenishment performance but also excellent electrochemical performance, making it particularly suitable for energy storage devices such as lithium-ion batteries, significantly improving battery capacity and cycle stability.

[0074] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a composite lithium supplement, characterized in that, Includes the following steps: S1. Dissolve lithium hydroxide and oxalic acid in pure water to prepare a saturated lithium oxalate solution, and add a metal catalyst; S2. Under an inert atmosphere, a saturated lithium oxalate solution containing a metal catalyst is spray-dried to form lithium oxalate particles. S3. Lithium oxalate particles are placed in a CVD rotary furnace. Inert gas is first introduced for 20 minutes to purge the air from the furnace. Then, the temperature is increased to the set first-stage reaction temperature at a rate of 10℃ / min, and the plasma is started. During this process, organic vapor is introduced using inert gas as a carrier gas and reacted for 60 minutes. Under the action of a metal catalyst, the organic vapor decomposes to produce carbon, which is deposited on the surface of lithium oxalate, eventually forming Li2C2O4@C. S4. Reduce the temperature of the CVD rotary furnace to the temperature required for the second stage reaction, introduce the silicon source using an inert gas as a carrier gas, and simultaneously introduce water vapor. React for 25 minutes. Under the catalytic action of water, the silicon source forms a SiO2 film, which uniformly coats the material surface, and finally obtains Li2C2O4@C@SiO2. S5. Reduce the temperature of the CVD rotary kiln to the temperature required for the third stage reaction, introduce the modifier using an inert gas as a carrier gas, react for 45 minutes, and the modifier undergoes a cross-linking reaction with the surface of Li2C2O4@C@SiO2 to form a fluorosilicone polymer layer containing trifluoromethyl groups, thus obtaining the final product Li2C2O4@C@SiO2@CF3.

2. The preparation method of the composite lithium supplement according to claim 1, characterized in that: The metal catalyst in step S1 is one or more of molybdenum carbide, molybdenum oxide, nickel oxide, iron oxide, and cobalt oxide.

3. The preparation of a composite lithium supplement according to claim 1, characterized in that: In step S1, the molar ratio of lithium hydroxide to oxalic acid is 2:1, and the pH of the saturated lithium oxalate solution in step S1 is 6.5-7.

5.

4. The preparation of a composite lithium supplement according to claim 1, characterized in that: In step S2, the outlet temperature of the spray dryer is controlled at 110-115℃, and the particle size D50 of the prepared lithium oxalate particles is 4-6μm.

5. The preparation of a composite lithium supplement according to claim 1, characterized in that: In step S3, the organic vapor is one or more of acetone, cyclohexanone, diethyl ether, and ethanol, and the reaction temperature in the first stage of step S3 is 340-360℃.

6. The preparation of a composite lithium supplement according to claim 1, characterized in that: In step S4, the silicon source is one or more of TEOS and SiH4, and the reaction temperature in the second stage of step S4 is 240-260℃.

7. The preparation of a composite lithium supplement according to claim 1, characterized in that: In step S5, the modifier is one or more of FOTS, PFOTS, MTES, and PFPTES, and the reaction temperature in the third stage of step S5 is 180-200℃.

8. The preparation of a composite lithium supplement according to claim 1, characterized in that: In steps S2, S3, S4, and S5, the inert gas is one or more of nitrogen, argon, and helium.

9. A composite lithium supplement material, characterized in that, Includes any one of the composite lithium supplements described in claims 1-8.

Images