Thermal activation type stable lithium complex lithium supplement additive as well as preparation method and application thereof

Abstract

The invention discloses a thermal activation type stable lithium complex lithium supplement additive as well as a preparation method and application thereof, and relates to the technical field of lithium supplement additives. The lithium complex lithium supplement additive disclosed by the invention is very stable in normal-temperature air and an electrolyte environment, the electrode preparation process and storage conditions are greatly simplified, and the production safety and the battery yield are improved; the lithium supplementing process is controlled by the temperature, so that the lithium supplementing time and degree are accurately regulated and controlled; the lithium supplement additive has high lithium supplement efficiency, complex decomposition is thorough, the utilization rate of released active lithium is high, most decomposition products are gas or neutral organic molecules capable of being dissolved in electrolyte, and high-impedance solid by-products cannot be left in an electrode; the lithium supplement additive disclosed by the invention is suitable for various high-capacity negative electrode systems, can effectively compensate huge first lithium loss of the high-capacity negative electrode systems, and is good in compatibility; the use of high-activity lithium metal or lithium-rich compounds is avoided, and the risks of combustion and explosion are reduced.

Description

Technical Field

[0001] This invention relates to the field of lithium supplementation additives, specifically a thermally activated stable lithium complex lithium supplementation additive, its preparation method, and its application. Background Technology

[0002] With the continuous improvement of the energy density of lithium-ion batteries, irreversible lithium loss caused by the formation of a solid electrolyte interface film during the first charge and discharge process has become a key factor in battery performance. Lithium replenishment technology is an effective means to solve this problem.

[0003] Currently, mainstream lithium supplementation additives include: lithium-rich compounds such as lithium oxide, lithium peroxide, and lithium nitride. These compounds are chemically reactive and readily react with air, moisture, or electrolyte at room temperature, leading to problems such as processing difficulties, poor storage stability, and battery gas generation; lithium metal powder, which also has high reactivity and safety risks; and other organic lithium salts such as lithium oxalate, which have high decomposition potentials and may not be able to effectively release lithium at the negative electrode potential.

[0004] In existing technologies, lithium replenishment additives generally suffer from a contradiction: highly reactive additives are unstable, while stable additives have decomposition potentials or conditions that are too harsh to effectively replenish lithium during normal battery formation. Therefore, it is crucial to develop a lithium replenishment additive that remains stable during battery preparation and storage, and can efficiently and controllably release active lithium under high-temperature and heated formation conditions. This invention proposes a thermally activated stable lithium complex lithium replenishment additive, its preparation method, and its application to solve the aforementioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide a thermally activated stable lithium complex lithium supplementation additive, its preparation method, and its application, in order to solve the problems raised in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A thermally activated stable lithium complex lithium supplement additive, whose general formula can be represented as Li⊕[L], where [L] is an organic ligand.

[0007] Furthermore, the organic ligand can form a stability constant (logK) with lithium ions in the range of 10. 4 ~10 10 Lithium complexes within the specified range are lithium supplementation additives.

[0008] Furthermore, the lithium complex lithium supplement additive has a decomposition rate of less than 5% within 30 days in lithium-ion battery electrolytes at temperatures below 40°C.

[0009] Furthermore, the lithium complex lithium supplement additive decomposes and releases more than 90% of the theoretical lithium capacity within 1 hour at a temperature of 50~80℃.

[0010] Furthermore, the organic ligand is any one or a combination of macrocyclic polyether compounds, organic acid anion compounds, and nitrogen-containing heterocyclic compounds.

[0011] Furthermore, the macrocyclic polyether compound is either a crown ether or a crypt ether.

[0012] Furthermore, the crown ether is any one of 12-crown ether-4, 15-crown ether-5, 18-crown ether-6 and their derivatives.

[0013] Furthermore, the organic acid anionic compound is any one of polycarboxylate anions or β-diketone anions.

[0014] Furthermore, the nitrogen-containing heterocyclic compound is any one of o-phenanthroline, bipyridine, and their derivatives.

[0015] In the above technical solutions, macrocyclic polyether compounds chelate with lithium ions through multiple oxygen atoms to form a stable "cage-like" structure with matching size; organic acid anionic compounds, such as anions formed by the deprotonation of acetylacetone, dibenzoylmethane, and thiophenecarboxylic acid trifluoroacetone, can form stable six- or five-membered chelate rings with lithium ions; nitrogen-containing heterocyclic compounds can coordinate with lithium ions through nitrogen atoms; theoretical calculations show that the decomposition reaction energy barrier of this lithium complex lithium supplement additive is 80~120kJ. / mol, this energy barrier range ensures that the reaction is extremely slow (stable) at room temperature, while the reaction rate is significantly accelerated (activated) at temperatures of 60~80℃; introducing large-volume substituents (such as tert-butyl, phenyl, long-chain alkyl) into the ligand structure can further improve the kinetic stability of the complex through steric hindrance effect and slow down the dissociation rate of lithium ions; O and N atoms with moderate electronegativity are preferred as coordinating atoms, which can form coordinate bonds with lithium ions with moderate strength, ensuring both stability and breakage upon heating.

[0016] A method for preparing a thermally activated stable lithium complex lithium supplementation additive includes any one of solution precipitation, solid-phase grinding, or solvent evaporation.

[0017] Furthermore, the lithium complex lithium supplement additive is prepared by the following process: under an inert atmosphere, a lithium source and an organic ligand are reacted in an anhydrous organic solvent, and then filtered, washed, and vacuum dried to obtain the lithium complex lithium supplement additive.

[0018] Furthermore, the lithium source is any one or a mixture of lithium hydride, n-butyllithium, and lithium hydroxide.

[0019] Furthermore, the anhydrous organic solvent is either anhydrous tetrahydrofuran or anhydrous acetonitrile.

[0020] Furthermore, the lithium complex supplementary additive is either Li⊕[acetylacetone complex] or Li⊕[18-crown ether-6 complex].

[0021] Furthermore, the Li⊕[acetylacetone complex] is prepared by the following process: S1: Add lithium hydride to anhydrous tetrahydrofuran and stir until homogeneous to obtain a lithium hydride suspension; S2: Add acetylacetone to anhydrous tetrahydrofuran and stir until homogeneous to obtain an acetylacetone solution; S3: Slowly add the acetylacetone solution dropwise to the lithium hydride suspension for 15-30 minutes. After the addition is complete, stir in an ice bath for 25-40 minutes, remove the ice bath, and continue stirring at room temperature for 11-13 hours. Filter, collect the filtrate, vacuum dry, and wash to obtain Li⊕[acetylacetone complex].

[0022] Furthermore, in step S1, the concentration of the lithium hydride suspension is 0.3~0.5 mg / mL.

[0023] Furthermore, in step S2, the concentration of the acetylacetone solution is 0.3~0.5 mmol / mL.

[0024] Furthermore, in step S3, the volume ratio of acetylacetone solution to lithium hydride suspension is (2~3):20.

[0025] Furthermore, the Li⊕[18-crown-6 complex] is prepared by the following process: Step 1: Add 18-crown ether-6 to anhydrous acetonitrile and stir until homogeneous to obtain a 18-crown ether-6 solution; Step 2: Slowly add the hexamethyldisilamide lithium hexane solution dropwise to the 18-crown ether-6 solution for 15-30 minutes. After the addition is complete, continue stirring at room temperature for 1.5-3 hours. Filter, collect the filter cake, wash, and vacuum dry to obtain Li⊕[18-crown ether-6 complex].

[0026] Furthermore, in step one, the concentration of the 18-crown ether-6 solution is 0.06~0.08 mmol / mL.

[0027] Furthermore, in step two, the volume ratio of the hexamethyldisilamide lithium hexane solution to the 18-crown ether-6 solution is 1:(12~18), and the concentration of the hexamethyldisilamide lithium hexane solution is 0.5~1.5 mol / L.

[0028] Furthermore, the 18-crown ether-6 can also be monooctyl-18-crown ether-6, obtained by the following process: Step 1: Add the dried 18-crown ether-6 to anhydrous tetrahydrofuran and stir until homogeneous to obtain a 18-crown ether-6 solution; Step 2: Add the 18-crown ether-6 solution to the n-butyllithium hexane solution, stir at room temperature for 30-40 min, then add 1-bromooctane, heat to reflux, and after the reaction is complete, cool to room temperature and purify to obtain monooctyl-18-crown ether-6.

[0029] Furthermore, in step 1, the specific drying process is as follows: vacuum drying at a temperature of 50~70℃ for 11~13 hours.

[0030] Furthermore, in step 1, the concentration of the 18-crown ether-6 solution is 0.08~0.1 g / mL.

[0031] Furthermore, in step 2, the ratio of 18-crown ether-6 solution, n-butyllithium hexane solution, and 1-bromooctane is (25~35) mL : (3~5) mL : (1.9~2.0) g.

[0032] Furthermore, in step 2, the n-butyllithium hexane solution is added at a rate of 1~2 drops / s under ice bath cooling; the concentration of the n-butyllithium hexane solution is 2.3~3.0 mol / L.

[0033] Furthermore, in step 2, the process conditions for heating and reflux are: reflux reaction at a temperature of 60~65℃ for 24~48h.

[0034] Furthermore, in step 2, the specific purification process is as follows: add 4-6 mL of deionized water to quench excess alkali, transfer to a separatory funnel, extract with ethyl acetate 3-4 times, combine the organic phases, wash with saturated saline, dry with anhydrous magnesium sulfate, filter, rotary evaporate, and purify using a silica gel column.

[0035] Furthermore, the eluent used in the silica gel column purification process is petroleum ether and ethyl acetate, with a volume ratio of petroleum ether to ethyl acetate of (3~5):1.

[0036] In the above technical solution, the effluent is collected separately during the purification process. The polarity of modified 18-crown ether-6 is slightly greater than that of 18-crown ether-6, and it will be eluted afterward. By thin-layer chromatography monitoring, the target component modified 18-crown ether-6 is a colorless and transparent oily liquid.

[0037] Furthermore, the anhydrous tetrahydrofuran is prepared by the following process: adding tetrahydrofuran to an indicator and distilling to obtain anhydrous tetrahydrofuran; the indicator is a mixture of sodium metal and benzophenone, with a mass ratio of sodium metal to benzophenone of 1:(0.5~1).

[0038] In the above technical solution, benzophenone reacts with metallic sodium in an anhydrous environment to generate a dark blue benzophenone free radical anion. The solution exhibits a persistent and stable blue color, which is a sign that tetrahydrofuran has been completely dried. If water is present, the free radical will react with water and become colorless. In step 2, n-butyllithium removes a proton from the ortho-methylene group of an oxygen atom in 18-crown ether-6 to generate a monolithiated 18-crown ether-6 anion.

[0039] Application of a thermally activated stable lithium complex lithium supplementation additive, which is used in the preparation of lithium-ion battery anode sheets and lithium-ion batteries containing the lithium-ion battery anode sheets.

[0040] Furthermore, the lithium-ion battery negative electrode sheet is made of lithium complex lithium supplementation additive, negative electrode active material, conductive agent and binder.

[0041] Furthermore, the negative electrode active material is any one of graphite, silicon-carbon composite material, and hard carbon.

[0042] Furthermore, the conductive agent is conductive carbon black.

[0043] Furthermore, the adhesive is polyvinylidene fluoride.

[0044] Compared with the prior art, the beneficial effects of the present invention are: 1. The lithium complex lithium replenishment additive of the present invention is very stable in room temperature air and electrolyte environment, which greatly simplifies the electrode preparation process and storage conditions, and improves production safety and battery yield. The lithium replenishment process is precisely controlled by the external parameter of temperature, rather than the traditional potential control. This allows the lithium replenishment reaction to be "triggered" by a mild heating program in the formation stage after battery packaging, so as to achieve precise control of the timing and degree of lithium replenishment.

[0045] 2. The lithium complex lithium supplementation additive of the present invention has high lithium supplementation efficiency, thorough decomposition of the complex, high utilization rate of released active lithium, and the decomposition products are mostly gases or neutral organic molecules soluble in electrolyte, and no high-resistivity solid by-products remain in the electrode.

[0046] 3. The lithium complex lithium replenishment additive of the present invention is suitable for various high-capacity anode systems, especially silicon-based anodes with extremely high initial coulombic efficiency requirements. It can effectively compensate for the huge initial lithium loss and has good compatibility. It avoids the use of highly active lithium metal or lithium-rich compounds, reducing the risk of combustion and explosion from the source. It is highly safe and overcomes the defects of existing lithium complex lithium replenishment additives that are difficult to balance stability and reactivity. Detailed Implementation

[0047] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] In the following specific implementation, Conductive agent, conductive carbon black, Super P; Adhesive, polyvinylidene fluoride (PVDF), model Solvay PVDF 5130; Anode active material, BTR New Materials: Natural graphite anode material, providing a particle size D50 of 15μm and an average specific surface area of ​​15m². 2 / g, average tap density 1.8g / cm³ 3 ; Oxidized powder, Shanghai Jizhi Biochemical: purity 99.9% (battery grade), key impurities heavy metals (Cu / Ni / Zn) ≤0.002%, Si≤0.004%, average particle size 3μm; Lithium hydride powder, Ganfeng Lithium: 99% battery grade, key impurities heavy metals (Cu / Ni / Zn) ≤0.002%, moisture ≤0.1%; 18-crown ether-6, molecular weight 264.32 g / mol; Anhydrous tetrahydrofuran is prepared by the following process: adding tetrahydrofuran to an indicator and distilling to obtain anhydrous tetrahydrofuran; the indicator is a mixture of sodium metal and benzophenone, with a mass ratio of sodium metal to benzophenone of 1:0.5. Example 1:

[0049] A method for preparing a thermally activated stable lithium complex lithium supplement additive includes the following steps: S1: Preparation and Weighing: (1) Place the round-bottom flask, stir bar, syringe, rubber septum, and needle into the transition chamber of the glove box, fully evacuate and purge with argon gas three times to remove air, and assemble the dry instrument in the glove box. (2) Accurately weigh 0.0080 g of lithium hydride powder and add it to a 50 mL dry round-bottom flask. Add a magnetic stir bar and 20 mL of anhydrous tetrahydrofuran measured with a syringe. Stir well to form a lithium hydride suspension. (3) Use another syringe to accurately measure 1.0 mmol of acetylacetone, dilute it with 2 mL of anhydrous tetrahydrofuran, and transfer it to a small vial with a rubber septum to obtain an acetylacetone solution; S2: Assembly and cooling of the reaction apparatus: (1) Seal the mouth of the round-bottom flask with a rubber septum, remove it from the glove box, and fix it on a magnetic stirrer. From this step until the reaction is completed and the flask is transferred back to the glove box, the system should always be isolated from the atmosphere by the septum. Aeration or feeding should be performed by needle. (2) Immerse the round-bottom flask in an ice-water bath and turn on the magnetic stirrer to fully suspend the lithium hydride in tetrahydrofuran; S3: Dropping reaction and process monitoring: Using a dry syringe, draw up the acetylacetone solution, insert the needle through the rubber septum, and add it dropwise very slowly into the lithium hydride suspension. The dropwise addition process should last for 15 minutes. After the addition is complete, continue stirring in an ice-water bath for 30 minutes to ensure the reaction is complete. S4: Follow-up reaction: Remove the ice-water bath and allow the reaction mixture to continue stirring at room temperature for 12 hours to ensure that the lithium hydride reacts completely. S5: Post-processing and purification: (1) After the reaction is complete, transfer the round-bottom flask back to the glove box, set up a filter device in the glove box, filter the reaction mixture with filter paper to remove any unreacted lithium hydride or other insoluble impurities, and collect the filtrate. (2) Place the filtrate in a vacuum dryer, connect a vacuum pump, and slowly evacuate at room temperature to allow the anhydrous tetrahydrofuran to completely evaporate. Avoid heating to prevent the product from decomposing or agglomerating, and obtain a solid powder. (3) Add the solid powder obtained in the previous step to 10 mL of anhydrous diethyl ether, stir gently with a spatula and break the solid, then let it stand for 15 min, filter again, wash the solid with diethyl ether, repeat the process of "adding anhydrous diethyl ether, stirring, and filtering" 3 times, then transfer it to a vacuum desiccator and vacuum dry at room temperature for 4 h, then transfer it to a sample bottle with a sealed cap in a glove box to obtain Li⊕[acetylacetone complex] lithium supplementation additive; An application of a thermally activated stable lithium complex lithium supplementation additive: the above-mentioned Li⊕[acetylacetone complex] lithium supplementation additive is applied to the preparation of lithium-ion battery anode sheets and lithium-ion batteries containing the lithium battery anode sheets; The negative electrode sheet of a lithium-ion battery is made of lithium complex lithium supplementation additive, negative electrode active material, conductive agent and binder. Example 2:

[0050] A method for preparing a thermally activated stable lithium complex lithium supplement additive includes the following steps: S1: Preparation and Weighing: (1) Place the round-bottom flask, stir bar, syringe, rubber septum, and needle into the transition chamber of the glove box, fully evacuate and purge with argon gas three times to remove all air, and assemble the dry instrument in the glove box. (2) Accurately weigh 1.0 mmol of 18-crown ether-6 powder and add it to a 50 mL dry round-bottom flask. Add a magnetic stir bar and 10 mL of anhydrous acetonitrile measured with a syringe. Stir well to form an 18-crown ether-6 solution. S2: Assembly of the reaction apparatus: Seal the mouth of the round-bottom flask with a rubber septum, remove it from the glove box, and fix it on the magnetic stirrer; S3: Add lithium source solution dropwise: (1) Using a dry 1mL syringe, accurately measure 1.0mL of a 1.0mol / L hexamethyldisilamide lithium hexane solution; (2) Insert the needle through the rubber septum into the liquid surface and slowly add the hexamethyldisilamide lithium hexane solution to the 18-crown ether-6 solution at a rate of 1 drop / s. The dropping process lasts for 15 minutes. After the dropping is completed, continue stirring at room temperature for 2 hours to ensure the reaction is complete, allow the crystal nuclei to grow, and allow the precipitate to age, which will facilitate subsequent filtration. S4: Post-processing and purification: (1) After the reaction is complete, transfer the round-bottom flask back into the glove box, set up a filter device, transfer the solid mixture from the previous step to the filter device for filtration, and collect the filter cake. (2) The solid powder obtained in the previous step was washed three times with 15 mL of anhydrous hexane, and transferred together with the funnel to a vacuum desiccator. A vacuum pump was connected, and the powder was vacuum dried at room temperature for 4 h. The powder was then transferred to a sample bottle with a sealed cap to obtain Li⊕[18-crown ether-6 complex] lithium supplementation additive. An application of a thermally activated stable lithium complex lithium supplementation additive: the above-mentioned Li⊕[18-crown ether-6 complex] lithium supplementation additive is applied to the preparation of lithium-ion battery anode sheets and lithium-ion batteries containing the lithium battery anode sheets; The negative electrode sheet of a lithium-ion battery is made of lithium complex lithium supplementation additive, negative electrode active material, conductive agent and binder. Example 3:

[0051] This embodiment provides a method for preparing a thermally activated stable lithium complex lithium supplement additive, wherein 18-crown ether-6 is replaced with monooctyl-18-crown ether-6, and the additive is prepared by the following process: Step 1: Preparation: (1) Place the round-bottom flask, stir bar, syringe, rubber septum, and needle into the transition chamber of the glove box, fully evacuate and purge with argon gas three times to remove all air, and assemble the dry instrument in the glove box. (2) 18-crown ether-6 was vacuum dried at 60°C for 12 h; Step 2: Ligand activation: (1) Accurately weigh 2.64 g of 18-crown ether-6 and add it to a 50 mL dry round-bottom flask. Add a magnetic stir bar and 30 mL of anhydrous tetrahydrofuran measured with a syringe. Stir to dissolve and obtain a 18-crown ether-6 solution. (2) Take 18-crown ether-6 solution and, under ice-water bath cooling, add 4.0 mL of 2.5 mol / L n-butyllithium hexane solution dropwise with a syringe at a dropping rate of 1 drop / s; Step 3: Nucleophilic substitution reaction: The product obtained in step 2 was stirred at room temperature for 30 minutes to ensure complete reaction. Then, 1.93 g of 1-bromooctane was added using a syringe, and the mixture was refluxed at 60 °C for 24 h. Step 4: Post-processing and purification: (1) After the reaction is completed, cool to room temperature, add 5 mL of water to quench the excess alkali, then transfer to a separatory funnel, extract three times with 30 mL of ethyl acetate, then combine the organic phases, wash with saturated brine, dry with anhydrous magnesium sulfate, filter, and rotary evaporate to obtain the crude oil product. (2) The crude oil product was purified using a silica gel column. The eluent used in the silica gel column purification process was petroleum ether and ethyl acetate, with a volume ratio of 3:1. The eluent was concentrated to obtain monooctyl-18-crown ether-6. The preparation process of the lithium complex lithium supplement additive was the same as in Example 2. An application of a thermally activated stable lithium complex lithium supplementation additive, wherein the above-mentioned lithium complex lithium supplementation additive is applied to the preparation of lithium-ion battery anode sheets and lithium-ion batteries containing the lithium battery anode sheets; The negative electrode sheet of a lithium-ion battery is made of lithium complex lithium supplementation additive, negative electrode active material, conductive agent and binder.

[0052] Comparative Example 1: This comparative example uses commercially available lithium oxide powder as a lithium supplement additive to prepare a lithium-ion battery negative electrode sheet and a lithium-ion battery containing the negative electrode sheet; the lithium-ion battery negative electrode sheet is made of lithium oxide powder, negative electrode active material, conductive agent and binder.

[0053] Comparative Example 2: This comparative example prepares a lithium battery without using lithium supplementation additives, prepares a lithium-ion battery negative electrode sheet and a lithium-ion battery containing the lithium-ion battery negative electrode sheet; the lithium-ion battery negative electrode sheet is made of negative electrode active material, conductive agent and binder.

[0054] experiment: The lithium supplementation additives obtained in Examples 1-3 and Comparative Examples 1-2 were used to prepare samples, and their performance was tested and the test results were recorded.

[0055] Stability test: The lithium supplementation additive samples were exposed to a glove box atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm) and the color and state changes were observed. At the same time, they were added to standard carbonate electrolytes and stored at 25°C for 30 days to observe their stability. Thermal activation performance test: The lithium complex lithium supplementation additive in the lithium battery sample was used to prepare a half cell. The half cell was left to stand at 25°C for 4 hours and then charged to 0.01V at a rate of 0.1C. The first week charging capacity was then tested. Battery performance testing: The lithium battery sample was subjected to 100 battery cycle performance tests, and the coulombic efficiency in the first week was recorded.

[0056] Table 1 Performance Comparison Table

[0057] Based on the data in the table above, the following conclusions can be clearly drawn: The lithium complex lithium supplementation additives obtained in Examples 1-3 are compared with the lithium supplementation additives obtained in Comparative Example 1, and the lithium batteries obtained in Examples 1-3 are compared with the lithium batteries obtained in Comparative Example 1-2. The test results show that: Compared with the comparative examples, the lithium complex lithium supplementation additives prepared in Examples 1-3 have good stability, and the batteries prepared with the lithium complex lithium supplementation additives of the present invention have good electrochemical performance.

[0058] Compared with Example 1, the commercial lithium oxide in Comparative Example 1 showed a significant color change within 3 days and generated a large amount of gas in the electrolyte. This indicates that lithium oxide is unstable as a lithium supplement additive and does not perform as well as the lithium complex supplement additive of the present invention, demonstrating the technical advantages of the lithium complex supplement additive preparation process of the present invention.

[0059] Compared with Example 1, the battery prepared in Comparative Example 2 without the use of lithium supplementation additives showed a significant decrease in electrochemical performance. This indicates that the use of lithium supplementation additives can significantly improve the electrochemical performance of batteries, meeting the current demand for high performance and high stability of lithium-ion batteries, and demonstrating the technical advantages of the lithium complex lithium supplementation additives of this invention.

[0060] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A thermally activated stable lithium complex lithium supplement additive, characterized in that: The general formula of the lithium complex lithium supplementation additive is Li⊕[L], where [L] is an organic ligand; The organic ligand is any one or a combination of macrocyclic polyether compounds, organic acid anion compounds, and nitrogen-containing heterocyclic compounds.

2. The thermally activated stable lithium complex lithium supplementation additive according to claim 1, characterized in that: The macrocyclic polyether compound is any one of crown ethers and crypt ethers; The organic acid anionic compounds are any one of polycarboxylic acid anions or β-diketone anions; The nitrogen-containing heterocyclic compound is any one of o-phenanthroline, bipyridine, and their derivatives.

3. A method for preparing a thermally activated stable lithium complex lithium supplementation additive, characterized in that: The lithium complex lithium supplement additive is prepared by the following process: under an inert atmosphere, a lithium source and an organic ligand are reacted in an anhydrous organic solvent, and then filtered, washed, and vacuum dried to obtain the lithium complex lithium supplement additive.

4. The method for preparing a thermally activated stable lithium complex lithium supplementation additive according to claim 3, characterized in that: The lithium source is any one or a mixture of lithium hydride, n-butyllithium, and lithium hydroxide; the anhydrous organic solvent is any one of anhydrous tetrahydrofuran and anhydrous acetonitrile.

5. The method for preparing a thermally activated stable lithium complex lithium supplementation additive according to claim 3, characterized in that: The lithium complex supplementary additive is either Li⊕[acetylacetone complex] or Li⊕[18-crown ether-6 complex].

6. The method for preparing a thermally activated stable lithium complex lithium supplementation additive according to claim 5, characterized in that: The Li⊕[acetylacetone complex] is prepared by the following process: S1: Add lithium hydride to anhydrous tetrahydrofuran and stir until homogeneous to obtain a lithium hydride suspension; S2: Add acetylacetone to anhydrous tetrahydrofuran and stir until homogeneous to obtain an acetylacetone solution; S3: Slowly add the acetylacetone solution dropwise to the lithium hydride suspension for 15-30 minutes. After the addition is complete, stir in an ice bath for 25-40 minutes, remove the ice bath, and continue stirring at room temperature for 11-13 hours. Filter, collect the filtrate, vacuum dry, and wash to obtain Li⊕[acetylacetone complex].

7. The method for preparing a thermally activated stable lithium complex lithium supplementation additive according to claim 5, characterized in that: The Li⊕[18-crown-6 complex] was prepared by the following process: Step 1: Add 18-crown ether-6 to anhydrous acetonitrile and stir until homogeneous to obtain a 18-crown ether-6 solution; Step 2: Slowly add the hexamethyldisilamide lithium hexane solution dropwise to the 18-crown ether-6 solution for 15-30 minutes. After the addition is complete, continue stirring at room temperature for 1.5-3 hours. Filter, collect the filter cake, wash, and vacuum dry to obtain Li⊕[18-crown ether-6 complex].

8. The method for preparing a thermally activated stable lithium complex lithium supplementation additive according to claim 7, characterized in that: The 18-crown ether-6 can also be monooctyl-18-crown ether-6, obtained by the following process: Step 1: Add the dried 18-crown ether-6 to anhydrous tetrahydrofuran and stir until homogeneous to obtain a 18-crown ether-6 solution; Step 2: Add the 18-crown ether-6 solution to the n-butyllithium hexane solution, stir at room temperature for 30-40 min, then add 1-bromooctane, heat to reflux, and after the reaction is complete, cool to room temperature and purify to obtain monooctyl-18-crown ether-6.

9. The method for preparing a thermally activated stable lithium complex lithium supplementation additive according to claim 8, characterized in that: In step 1, the specific drying process is as follows: vacuum drying at 50~70℃ for 11~13h; in step 2, the n-butyllithium hexane solution is added at an acceleration rate of 1~2 drops / s under ice bath cooling, and the concentration of the n-butyllithium hexane solution is 2.5~3.0mol / L; the heating and reflux process conditions are as follows: reflux reaction at 60~65℃ for 24~48h.

10. The application of a thermally activated stable lithium complex lithium supplementation additive, characterized in that: Used in the preparation of lithium battery anode sheets and in lithium batteries containing such anode sheets.

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