A high entropy polymer protective film and its preparation method and application

Abstract

The present application discloses a high entropy polymer protective film and its preparation method and application, which belongs to the field of lithium battery technology. The high entropy polymer protective film provided by the present application is made of at least five polymers, at least five lithium salts and inorganic metal additives with a mass ratio of (5%-20%): (75%-95%): (1%-5%), and can form a 3D grid structure, which can not only reduce the crystallinity of the polymer, improve the ionic conductivity and ductility of the protective film, but also greatly reduce the proportion of the polymer in the protective film, minimize the adverse effects of the polymer, and at the same time expand the lithium ion transmission area, which is conducive to the uniform deposition / stripping of lithium ions, inhibit the growth of lithium dendrites, reduce battery impedance, and enhance the battery cycle power. It has broad application prospects in the preparation of lithium batteries.

Description

Technical Field

[0001] The present application belongs to the field of lithium battery technology, and in particular relates to a high entropy polymer protective film and a preparation method and application thereof. Background Art

[0002] Lithium metal batteries have attracted much attention due to their high specific energy, long cycle life, high output power, good safety performance and low environmental pollution, and have broad application prospects. Lithium metal has always been regarded as the most ideal negative electrode material for lithium batteries, and has attracted great attention due to its high theoretical capacity (3860mAh / g) and low reduction potential (about -3.04V compared to the standard hydrogen electrode). However, due to the irregular growth of lithium dendrites and strong interfacial side reactions, the lithium metal negative electrode causes poor cycle stability and low capacity of lithium metal batteries, and may even cause battery short circuit. Therefore, it is necessary to develop a negative electrode protective film that forms a uniform SEI film on the surface of the lithium metal negative electrode, so as to ensure the smooth transmission of lithium ions and thus improve the stability of the battery.

[0003] The prior art with application publication number CN 115810753 A discloses a method for preparing a negative electrode protective film: an anhydride polymer and a polymer A are dissolved in an organic solvent, and then a polymer B, an organic lithium salt and an optional inorganic additive are added to mix and perform a cross-linking polymerization reaction to obtain a film-forming coating; the film-forming coating is applied to the surface of a substrate, and then vacuum dried to obtain a negative electrode protective film.

[0004] However, the above-mentioned negative electrode protective film has the following problems: the amount of polymer used is large, the protective film is highly crystalline, and since the lithium ion conductivity is proportional to the number of free ions, a large amount of polymer will greatly reduce the number of lithium free ions, which is not conducive to lithium ion transmission and reduces battery efficiency and cycle performance. Summary of the invention

[0005] The present application discloses a high entropy polymer protective film and a preparation method and application thereof, aiming to solve the technical problems of existing polymer protective films such as large polymer usage, low electrical conductivity and poor mechanical strength.

[0006] In order to achieve the above purpose, the technical solution of this application is:

[0007] The first aspect of the present application provides a high entropy polymer protective film, the preparation raw materials of which include at least five polymers, at least five lithium salts and an inorganic metal additive;

[0008] Wherein, the mass ratio of the polymer: lithium salt: inorganic metal additive is (5%-20%): (75%-95%): (1%-5%).

[0009] In combination with the first aspect, preferably, the polymer is at least five of polycyanoacrylate, polyacrylonitrile, polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, thermoplastic polyurethane, polyvinyl alcohol, polyethyl methacrylate, and polymethyl methacrylate.

[0010] In combination with the first aspect, preferably, the lithium salt is at least five of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium bis(trifluoromethylsulfonylimide), lithium bis(fluorooxalatoborate), lithium bis(fluorosulfonylimide), lithium hexafluoroarsenate, lithium phosphate, lithium sulfate, lithium carbonate, lithium nitrate, lithium perchlorate, lithium nitride, lithium oxide, lithium sulfide, lithium iodide, lithium chloride, lithium fluoride, and lithium boride.

[0011] In combination with the first aspect, preferably, the inorganic metal additive is one or more of magnesium nitrate, magnesium carbonate, magnesium chloride, zinc acetate, zinc sulfate, zinc carbonate, copper sulfate, copper carbonate, ferric acetate, ferric nitrate, ferric sulfate, ferric carbonate, ferric chloride, titanium sulfate, titanium carbonate, aluminum acetate, aluminum sulfate, aluminum carbonate, and aluminum chloride.

[0012] The second aspect of the present application provides a method for preparing the high entropy polymer protective film according to the first aspect, the method comprising:

[0013] Under a rare gas atmosphere, dissolving the polymer, lithium salt and inorganic metal additive in an organic solvent to obtain a film-forming solution;

[0014] The film-making solution is coated on the surface of a substrate and vacuum dried to obtain a high entropy polymer protective film.

[0015] In combination with the second aspect, preferably, the thickness of the high entropy polymer protective film is 1-5 μm.

[0016] In combination with the second aspect, preferably, the organic solvent is one or more of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, methyl formate, ethyl acetate, propyl acetate, methyl propionate and ethyl propionate.

[0017] In combination with the second aspect, preferably, the polymer, lithium salt and inorganic metal additive are dissolved in an organic solvent and the reaction temperature is 20-60° C. and the reaction time is 6-14 hours.

[0018] The third aspect of the present application provides a lithium battery negative electrode, the lithium battery negative electrode comprising a negative electrode sheet and a protective film composited on the surface of the negative electrode sheet;

[0019] The protective film is the high entropy polymer protective film described in the first aspect or the high entropy polymer protective film prepared by the preparation method described in the second aspect.

[0020] The fourth aspect of the present application provides the use of the lithium battery negative electrode described in the third aspect in the preparation of a lithium battery.

[0021] Compared with the prior art, the advantages or beneficial effects of the embodiments of the present application include at least:

[0022] The high entropy polymer protective film provided in the present application is made of at least five polymers, at least five lithium salts and inorganic metal additives in a mass ratio of (5%-20%): (75%-95%): (1%-5%); on the one hand, it can form a 3D grid structure, which can not only reduce the crystallinity of the polymer, improve the ionic conductivity and ductility of the protective film, but also greatly reduce the proportion of the polymer in the protective film, minimize the adverse effects of the polymer, and at the same time expand the lithium ion transmission area, which is conducive to the uniform deposition / stripping of lithium ions and inhibits the growth of lithium dendrites; on the other hand, it can induce rapid lithium ion transmission, thereby uniformly depositing lithium, inhibiting the growth of lithium dendrites, reducing battery impedance, and enhancing battery cycle power; thirdly, the inorganic metal additive acts as a Lewis acid to promote the dissociation of lithium salts, enhance lithium ion diffusion, and further improve the ionic conductivity of the high entropy polymer protective film. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 This is a graph showing the performance test results of the A1-high entropy polymer protective film and B1-protective film prepared in the examples of the present application. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0026] In the following description of this embodiment, the term "and / or" is used to describe the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, B exists alone, and A and B exist at the same time. A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0027] In the following description of this embodiment, the term "at least one" refers to one or more, and "plurality" refers to two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b or c", or "at least one of a, b and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0028] Those skilled in the art should understand that in the following description of the embodiments of the present application, the order of serial numbers does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0029] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0030] It should be noted that all raw materials and reagents in the examples of the present application were purchased on the market or prepared according to conventional methods well known to those skilled in the art.

[0031] In a first aspect, an embodiment of the present application provides a high entropy polymer protective film, the preparation raw materials of which include at least five polymers, at least five lithium salts and an inorganic metal additive;

[0032] Wherein, the mass ratio of the polymer: lithium salt: inorganic metal additive is (5%-20%): (75%-95%): (1%-5%).

[0033] Among them, on the one hand, it can form a 3D grid structure, which can not only reduce the crystallinity of the polymer, improve the ionic conductivity and ductility of the protective film, but also greatly reduce the proportion of the polymer in the protective film, minimize the adverse effects of the polymer, and at the same time expand the lithium ion transmission area, which is conducive to the uniform deposition / stripping of lithium ions and inhibits the growth of lithium dendrites; on the other hand, it can induce rapid lithium ion transmission, thereby making lithium uniformly deposited, inhibiting the growth of lithium dendrites, reducing battery impedance, and enhancing battery cycle power; thirdly, inorganic metal additives act as Lewis acids to promote the dissociation of lithium salts, enhance lithium ion diffusion, and further improve the ionic conductivity of the high entropy polymer protective film.

[0034] In the embodiment of the present application, the polymer is preferably at least five of polycyanoacrylate, polyacrylonitrile, polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, thermoplastic polyurethane, polyvinyl alcohol, polyethyl methacrylate, and polymethyl methacrylate. The ratio of five or more polymers is (5-95%): (5-95%): (5-95%): (5-95%): (5-95%)..., wherein, since lithium ions move between complexing points with the assistance of the polymer matrix, it is not conducive to lithium ion transmission, reduces the rate performance of the battery, and causes a large amount of lithium metal to be deposited on the negative electrode surface. The polymer selected in this application, on the one hand, has low crystallinity, enhances the transmission performance of lithium ions, and improves the battery charge and discharge efficiency; on the other hand, multiple polymers are cross-linked with each other to form a 3D grid structure, reducing the proportion of polymers, while improving the mechanical strength of the protective film, and also increasing the ion transport point at the interface with the negative electrode, improving the lithium ion conductivity, reducing the battery impedance, preventing lithium metal deposition, and improving the battery stability. Therefore, by selecting these polymers, the proportion of polymer in the protective film can be greatly reduced, the adverse effects of the polymer can be reduced, the mechanical properties of the protective film can be greatly improved, and the volume expansion and the generation of lithium dendrites can be inhibited.

[0035] In the embodiment of the present application, the lithium salt is at least five of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium bis(trifluoromethylsulfonyl imide), lithium bis(fluorooxalatoborate), lithium bis(fluorosulfonyl imide), lithium hexafluoroarsenate, lithium phosphate, lithium sulfate, lithium carbonate, lithium nitrate, lithium perchlorate, lithium nitride, lithium oxide, lithium sulfide, lithium iodide, lithium chloride, lithium fluoride, and lithium boride. The ratio of five or more lithium salts is (5-95%): (5-95%): (5-95%): (5-95%): (5-95%)... Among them, the lithium ion conductivity is proportional to the free ions in the protective film, and the effective number of free ions is related to the degree of dissociation of the lithium salt in the polymer. These lithium salts have a good degree of dissociation. Adding a variety of lithium salts can further increase the lithium free ions, thereby improving the lithium ion conductivity and enhancing the battery performance.

[0036] In the embodiment of the present application, the inorganic metal additive is preferably one or more of magnesium nitrate, magnesium carbonate, magnesium chloride, zinc acetate, zinc sulfate, zinc carbonate, copper sulfate, copper carbonate, ferric acetate, ferric nitrate, ferric sulfate, ferric carbonate, ferric chloride, titanium sulfate, titanium carbonate, aluminum acetate, aluminum sulfate, aluminum carbonate, and aluminum chloride. The polymer itself has a certain degree of crystallinity and low disorder, which is not conducive to the dissociation of lithium salts and reduces the free transport of lithium ions. By selecting these inorganic metal additives, the crystallinity of the polymer can be reduced, the lithium ion dissociation effect can be enhanced, the lithium ion transport performance can be improved, and the battery charge and discharge efficiency and cycle performance can be enhanced.

[0037] In a second aspect, the present application also provides a method for preparing the high entropy polymer protective film according to the first aspect, the method comprising:

[0038] Under a rare gas atmosphere, dissolving the polymer, lithium salt and inorganic metal additive in an organic solvent to obtain a film-forming solution;

[0039] The film-making solution is coated on the surface of a substrate and vacuum dried to obtain a high entropy polymer protective film.

[0040] It should be noted that the preparation process adopted in the present application is simple, easy to mass produce, and has broad application prospects.

[0041] In the embodiment of the present application, the organic solvent is preferably one or more of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, methyl formate, ethyl acetate, propyl acetate, methyl propionate, and ethyl propionate. By selecting these organic solvents, a uniform and stable film-forming solution can be formed, providing a basis for subsequent coating.

[0042] In the embodiment of the present application, the polymer, lithium salt and inorganic metal additive are dissolved in an organic solvent and the reaction temperature is preferably 20-30°C and the reaction time is preferably 6-14 hours. By controlling the reaction time in the organic solvent, a uniform and stable film-forming solution can be formed, providing a basis for subsequent coating.

[0043] The third aspect of the present application provides a lithium battery negative electrode, the lithium battery negative electrode comprising a negative electrode sheet and a protective film composited on the surface of the negative electrode sheet; the protective film is the high entropy polymer protective film described in the first aspect or the high entropy polymer protective film prepared by the preparation method described in the second aspect. The preferred negative electrode sheet of the present application is a metal lithium sheet, more preferably a metal lithium foil.

[0044] The fourth aspect of the present application provides the application of the negative electrode of the lithium battery described in the third aspect in the preparation of a lithium battery. Among them, the lithium metal battery includes a positive electrode sheet, a lithium metal negative electrode sheet, a separator and an electrolyte. The positive electrode sheet may include a positive electrode current collector and a positive electrode membrane provided on at least one surface of the positive electrode current collector and including a positive electrode active material. The positive electrode active material may be selected from lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, olivine structure lithium phosphate, etc., but the present application is not limited to these materials, and other traditionally known materials that can be used as positive electrode active materials for lithium metal batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. The positive electrode membrane may also include a conductive agent and a binder. The types of the conductive agent and the binder are not specifically limited and may be selected according to actual needs. The separator is provided between the positive electrode sheet and the negative electrode sheet to serve as an isolation. The type of the separator is not specifically limited, and can be any separator material used in existing batteries, such as polyethylene, polypropylene, polyvinylidene fluoride, and multilayer composite films thereof, but not limited thereto. The electrolyte includes an organic solvent, a lithium salt, and an additive.

[0045] The technical solution of the present application will be further described below in conjunction with specific embodiments.

[0046] Example 1

[0047] This embodiment provides a method for preparing an A1-high-efficiency organic up-conversion device, which specifically includes:

[0048] (1) Preparation of negative electrode sheet:

[0049] Preparation of polymer protective film: in a glove box filled with argon (water content <1ppm, oxygen content <1ppm), one or more polymers A are dissolved in xylene, stirred at a speed of 100-300rpm, and stirred at room temperature for 6-14h to obtain a slurry; one or more lithium salts B are dissolved in the slurry, stirred at a speed of 200-800rpm, and stirred at 60°C for 1-2h, then an inorganic metal additive is added, and stirring is continued for 1h to obtain a solution; the solution is poured on a polytetrafluoroethylene plate, the polytetrafluoroethylene plate is placed on a fully automatic coating machine, and a 350μm scraper is used for scraping, the coating speed is 20-50mm / s, and it is allowed to stand at room temperature in a drying room for 12-20h, and dried in a vacuum drying oven at 40-60°C for 6-12h to obtain a polymer protective film.

[0050] Lithium metal negative electrode sheet: In a glove box filled with argon (water content <1 ppm, oxygen content <1 ppm), a high entropy polymer protective film was set on a lithium metal sheet with a thickness of 50 μm to obtain a lithium metal negative electrode sheet C.

[0051] (2) Preparation of positive electrode sheet:

[0052] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, conductive agent SuperP, and binder polyvinylidene fluoride (PVDF) are mixed evenly in N-methylpyrrolidone (NMP) to prepare positive electrode slurry, wherein the solid content in the positive electrode slurry is 50wt%, and the solid content of LiNi 0.8 Co 0.1 Mn 0.1 The mass ratio of O2, SuperP and PVDF is 80:10:10. Then, the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil and dried at 60°C and then cold pressed, followed by trimming, cutting and striping, and then continued to dry at 60°C under vacuum conditions for 12 hours to make a positive electrode sheet.

[0053] (3) Preparation of electrolyte:

[0054] In a glove box filled with argon (water content <1ppm, oxygen content <1ppm), lithium hexafluorophosphate (LiPF6) was slowly added to a mixed solvent of fluoroethylene carbonate (FEC) and dimethyl carbonate (DMC) (the volume ratio of FEC and DMC was 1:1) to prepare an electrolyte with a LiPF6 concentration of 1 mol / L.

[0055] (4) Preparation of lithium metal batteries:

[0056] In a glove box filled with argon (water content <1ppm, oxygen content <1ppm), a polyethylene film (Φ20mm) with a thickness of 12μm was used as an isolating film, and the positive electrode sheet, isolating film, and lithium metal negative electrode sheet were placed in order, so that the isolating film was placed between the positive and negative electrode sheets to play an isolating role. The electrolyte was injected, assembled into a CR2430 button cell, and left to stand for 24 hours to obtain a lithium metal battery.

[0057] Embodiment 2-6

[0058] The method of Example 1 is followed, except that the selection and weight content of the selected polymer combination, lithium salt combination and inorganic metal additive are as shown in Table 1.

[0059] Table 1 Selection of substances in the examples

[0060]

[0061]

[0062] At the same time, in order to verify the comprehensive performance of the high entropy polymer protective film prepared in the above examples, the present application provides the following comparative examples for detailed description.

[0063] Comparative Examples 1-6

[0064] The method of Example 1 is followed, except that the selection and weight content of the selected polymer combination, lithium salt combination and inorganic metal additive are as shown in Table 2.

[0065] Table 2 Selection of substances in comparative examples

[0066]

[0067]

[0068] The polymer protective films prepared in the examples and comparative examples of the present application were subjected to comprehensive performance tests, and the results are shown in Table 3.

[0069] Table 3 Comprehensive performance data

[0070]

[0071]

[0072] from Figure 1 It can be seen from the test results of Table 3 that the polymer protective films of Examples 1-6 contain 5 or more polymers and lithium salts, and inorganic metal additives are added. The lithium metal battery has a higher initial charge and discharge efficiency and capacity retention rate, and no lithium dendrite growth is found. This is because a variety of polymers and inorganic metal additives can reduce the crystallinity of the protective film, enhance the film-forming property, make the protective film thin and crack-free, and a variety of different polymers will form a 3D grid structure. Even if the polymer content is very low, a thin and uniform polymer protective film can still be formed. It has excellent mechanical strength during the battery cycle, prevents lithium dendrite penetration and cracks caused by too thin a film, improves ionic conductivity and cycle stability, and reduces interface impedance; at the same time, multiple types of lithium salts further improve ionic conductivity, which is conducive to uniform deposition of lithium ions, inhibits lithium dendrite growth, and improves battery capacity and cycle stability.

[0073] According to the test results in Table 3, Comparative Example 1 contains only one polymer and lithium salt, the protective film is thick and uneven, the impedance is large, the ion conductivity is low, the cycle stability is poor, and the battery is short-circuited; Comparative Example 2 keeps the polymer unchanged, increases the type of lithium salt, and the conductivity and the first charge and discharge efficiency are significantly improved, but the film is thick, the structure is easy to collapse, and the ductility is poor, which is not conducive to ion transmission, resulting in large battery energy loss; Comparative Example 3 keeps the lithium salt unchanged, increases the type of polymer, and the conductivity is slightly improved. This is due to the significant reduction in the thickness of the film, but it cannot effectively improve the ion conductivity and the first charge and discharge efficiency, and it cannot suppress The growth of lithium dendrites causes the battery to short-circuit; the polymer content in comparative example 4 is less than 5%, which makes it difficult for the polymer to effectively aggregate to form a protective film, resulting in a thick film and uneven surface, and even cracks; the polymer content in comparative example 5 is higher than 20%, although the thickness is significantly reduced, the high content of polymer reduces the ionic conductivity, making the first charge and discharge efficiency extremely low and the cycle stability poor; comparative example 6 contains a variety of polymers and lithium salts, the film thickness is greatly reduced, the conductivity and the first charge and discharge efficiency are significantly improved, but because no additives are added, the cycle stability is poor, and the protective film fails to effectively inhibit the growth of lithium dendrites. Therefore, by using at least five polymers, at least five lithium salts and inorganic metal additives in a mass ratio of (5%-20%): (75%-95%): (1%-5%), the ionic conductivity and the ductility of the protective film are improved, and the battery cycle power is enhanced.

[0074] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0075] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions recorded in the aforementioned embodiments may still be modified, or some or all of the technical features therein may be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. A high entropy polymer protective film, characterized in that: The raw materials for its preparation include at least five polymers, at least five lithium salts and inorganic metal additives; Wherein, the mass ratio of the polymer: lithium salt: inorganic metal additive is (5%-20%): (75%-95%): (1%-5%); The thickness of the high entropy polymer protective film is 1-5 μm; The polymer is at least five of polycyanoacrylate, polyacrylonitrile, polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, thermoplastic polyurethane, polyvinyl alcohol, polyethyl methacrylate, and polymethyl methacrylate; The lithium salt is at least five of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium bis(trifluoromethylsulfonylimide), lithium bis(fluorooxalatoborate), lithium bis(fluorosulfonylimide), lithium hexafluoroarsenate, lithium phosphate, lithium sulfate, lithium carbonate, lithium nitrate, lithium perchlorate, lithium nitride, lithium oxide, lithium sulfide, lithium iodide, lithium chloride, lithium fluoride, and lithium boride; The preparation method of the high entropy polymer protective film comprises: Under a rare gas atmosphere, dissolving the polymer, lithium salt and inorganic metal additive in an organic solvent to obtain a film-forming solution; The film-making solution is coated on the surface of a substrate and vacuum dried to obtain a high entropy polymer protective film.

2. The high entropy polymer protective film according to claim 1, characterized in that: The inorganic metal additive is one or more of magnesium nitrate, magnesium carbonate, magnesium chloride, zinc acetate, zinc sulfate, zinc carbonate, copper sulfate, copper carbonate, ferric acetate, ferric nitrate, ferric sulfate, ferric carbonate, ferric chloride, titanium sulfate, titanium carbonate, aluminum acetate, aluminum sulfate, aluminum carbonate, and aluminum chloride.

3. The high entropy polymer protective film according to claim 1, characterized in that: The organic solvent is one or more of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, methyl formate, ethyl acetate, propyl acetate, methyl propionate, and ethyl propionate.

4. The high entropy polymer protective film according to claim 1, characterized in that: The polymer, lithium salt and inorganic metal additive are dissolved in an organic solvent and the reaction temperature is 20-60°C and the reaction time is 6-14 hours.

5. A lithium battery negative electrode, characterized in that: The negative electrode of the lithium battery comprises a negative electrode sheet and a protective film compounded on the surface of the negative electrode sheet; The protective film is the high entropy polymer protective film described in any one of claims 1-4.

6. Use of the lithium battery negative electrode according to claim 5 in the preparation of a lithium battery.

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