A polymer artificial SEI layer solution and a preparation method thereof, a modified metal electrode, and an aqueous metal battery

Abstract

The application provides a polymer artificial SEI layer solution, a preparation method thereof, a modified metal electrode and an aqueous metal battery. The application utilizes the fact that fluorine-containing monomers and silicon, zinc, aluminum and boron elements in a crosslinking agent can form dynamic bonds and undergo dynamic crosslinking reaction to obtain a fluorine-containing self-healing single-ion monomer polymer artificial SEI layer solution. The polymer artificial SEI layer solution is coated on a metal electrode to form a polymer artificial SEI layer. The artificial SEI layer can better cater to and inhibit the generation of zinc dendrites of zinc and other metals in the process of electroplating / delamination, thereby solving the problem of poor surface interface stability of zinc and other metal anodes. The fluorine-containing molecular structure can promote the participation of the artificial SEI layer in the formation of an in-situ SEI layer on the electrode surface in the reduction process, generate fluorine-containing metal compounds and improve the surface interface stability of the electrode, thereby improving the cycle stability of the metal battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal batteries, in particular to a polymer artificial SEI layer solution and a preparation method thereof, a modified metal electrode and an aqueous metal battery. BACKGROUND

[0002] The environmentally friendly aqueous secondary metal battery, such as an aqueous zinc metal battery, uses zinc metal as a negative electrode and an aqueous solution of zinc salt as an electrolyte, and has the advantages of high safety, fast charge / discharge capacity, wide material availability, low cost and the like. In addition, zinc metal has a high theoretical specific capacity (820 mAh g -1 ), a high theoretical volume capacity (5855 mAh cm -3 ), a low redox potential of zinc metal (-0.76 V vs. SHE), and a unique high ionic conductivity of aqueous electrolyte (>10 mS cm -1 ), and has become a research hotspot for large-scale energy storage devices. Unfortunately, the current aqueous secondary zinc metal battery has not been commercialized due to some problems of the zinc metal negative electrode, such as poor stability of the zinc metal electrode / electrolyte surface interface caused by zinc dendrite growth, corrosion, passivation and the like, resulting in low utilization of the zinc metal negative electrode, poor battery coulomb efficiency and cycle performance.

[0003] The polymer artificial solid electrolyte layer (SEI) is widely used on the surface of the metal electrode due to its advantages of high elasticity, good stability and inhibition of dendrite growth, which makes up for the defect of poor stability of the in-situ generated SEI layer in the reduction process of the electrolyte. On the one hand, the design of the elastic polymer artificial SEI layer can relieve or inhibit the rupture of the SEI layer caused by the huge volume expansion of the metal negative electrode in the process of electrodeposition / detachment, effectively prevent the side reaction caused by the direct contact between the metal electrode and the electrolyte, and thus improve the utilization of the metal negative electrode. On the other hand, in the design process of the artificial SEI layer, the selection of the fluorine-containing molecular structure can promote the participation of the artificial SEI layer in the formation of the in-situ SEI layer on the electrode surface in the reduction process, generate fluorine-containing metal compounds, improve the stability of the electrode surface interface, and thus improve the cycle stability of the metal battery.

[0004] The currently reported polymer artificial SEI layer cannot well cater to the large local volume change of the electrode surface caused by zinc metal deposition and inhibit the growth of metal dendrites, which is not conducive to the stable cycle of the battery under high current density and deposition capacity. Therefore, it is necessary to improve the existing polymer artificial SEI layer. SUMMARY

[0005] Therefore, the present application provides a polymer artificial SEI layer solution and a preparation method thereof, a modified metal electrode and an aqueous metal battery to solve the technical problems in the prior art.

[0006] In a first aspect, the present application provides a polymer artificial SEI layer solution, comprising a fluorine-containing monomer, a cross-linking agent, an organic solvent, and a polymer film-forming agent.

[0007] Preferably, the fluorine-containing monomer comprises at least one of a partially fluorine-substituted alcohol-hydroxyl-terminated alkane and a perfluorine-substituted alcohol-hydroxyl-terminated alkane.

[0008] The cross-linking agent comprises at least one of a cross-linking agent containing silicon, zinc, aluminum, and boron.

[0009] Preferably, the polymer artificial SEI layer solution comprises at least one of tetrafluoropropyl alcohol, hexafluorobutyl alcohol, 4-fluoro-1-butyl alcohol, and 3,3-difluorocyclobutanol.

[0010] Preferably, the perfluorine-substituted alcohol-hydroxyl-terminated alkane comprises at least one of octafluoro-1,6-hexanediol, 2,2-difluoro-1,3-propanediol, 2,2,3,3-tetrafluoro-1,4-butanediol, 1H,1H,8H,8H-perfluoro-1,8-octanediol, 1H,1H,9H,9H-perfluoro-1,9-nonanediol, and 1H,1H,10H,10H-perfluoro-1,10-decanediol.

[0011] Preferably, the cross-linking agent comprises at least one of silicon tetrachloride, zinc chloride, lithium aluminum hydride, lithium borohydride, and sodium borohydride.

[0012] Preferably, the polymer film-forming agent comprises at least one of polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, and polyvinyl alcohol.

[0013] Preferably, the organic solvent comprises at least one of N-methylpyrrolidone, dimethyl sulfoxide, ethylene glycol dimethyl ether, and N,N-dimethylformamide.

[0014] In a second aspect, the present application provides a preparation method of the polymer artificial SEI layer solution, comprising the following steps:

[0015] Dispersing the fluorine-containing monomer in the organic solvent under an inert gas to obtain a mixed solution;

[0016] Adding the cross-linking agent to the mixed solution and stirring to perform a cross-linking reaction;

[0017] Adding the mixed solution after the cross-linking reaction to the polymer film-forming agent and stirring to obtain the polymer artificial SEI layer solution.

[0018] Preferably, in the step of adding the cross-linking agent to the mixed solution and stirring, the stirring temperature is 30-70°C.

[0019] Preferably, the preparation method of the polymer artificial SEI layer solution, the step of adding the mixed solution after cross-linking reaction into the polymer film forming agent, the mass ratio of the mixed solution after cross-linking reaction to the polymer film forming agent is (4-9):1;

[0020] And / or, the mass ratio of the fluorine-containing monomer, the organic solvent and the cross-linking agent is (0.6-0.8):(2000-3000):(5-15);

[0021] And / or, the concentration of the mixed solution after cross-linking reaction is 50-250 mg / ml;

[0022] And / or, the inert gas includes at least one of argon, helium and nitrogen;

[0023] And / or, before adding the mixed solution after cross-linking reaction into the polymer film forming agent, the mixed solution after cross-linking reaction is further filtered.

[0024] In a third aspect, the present application further provides a modified metal electrode, and a preparation method of the modified metal electrode includes the following steps:

[0025] The polymer artificial SEI layer solution prepared by the preparation method is coated on the metal electrode to obtain the modified metal electrode.

[0026] Preferably, the modified metal electrode, the metal electrode includes any one of lithium metal electrode, sodium metal electrode, zinc metal electrode and aluminum metal electrode;

[0027] And / or, 5-20 μL of the polymer artificial SEI layer solution is coated on the metal electrode;

[0028] And / or, the diameter of the metal electrode is 8-16 mm.

[0029] In a fourth aspect, the present application further provides an application of the modified metal electrode as a negative electrode in the preparation of an aqueous metal battery.

[0030] In a fifth aspect, the present application further provides an aqueous metal battery, which includes a negative electrode, and the negative electrode is the modified metal electrode.

[0031] Preferably, the aqueous metal battery, the modified metal electrode is a modified zinc metal electrode;

[0032] The aqueous metal battery further includes a positive electrode, a separator and an electrolyte;

[0033] Preferably, the positive electrode includes any one of manganese dioxide, cobalt-nickel sulfide, vanadium pentoxide, ammonium vanadate and sodium vanadate;

[0034] Preferably, the diaphragm comprises any one of PP diaphragm, cellulose diaphragm, glass fiber diaphragm;

[0035] Preferably, the electrolyte comprises any one of zinc sulfate aqueous solution, zinc chloride aqueous solution, zinc triflate aqueous solution, zinc perchlorate aqueous solution, zinc hexafluorosilicate aqueous solution, zinc bistrifluoromethanesulfonimide aqueous solution;

[0036] Preferably, the concentration of the electrolyte is 0.5-3 mol / L.

[0037] The polymer artificial SEI layer solution, the preparation method thereof, the modified metal electrode and the aqueous metal battery have the following beneficial effects:

[0038] 1. The polymer artificial SEI layer solution comprises fluorine-containing monomer, crosslinking agent, organic solvent and polymer film forming agent. The fluorine-substituted alcohol hydroxyl-terminated alkane and / or perfluorinated alcohol hydroxyl-terminated alkane can form dynamic bonds with silicon, zinc, aluminum and boron elements in the crosslinking agent, and dynamic crosslinking reaction occurs. The mixed solution after crosslinking reaction is added to the polymer film forming agent to obtain a fluorine-containing self-healing single-ion monomer polymer artificial SEI layer solution. The fluorine-containing self-healing single-ion monomer polymer artificial SEI layer solution is coated on the metal electrode to form a polymer artificial SEI layer. The fluorine-rich self-healing single-ion conductor polymer artificial SEI layer can better cater to and inhibit the generation of zinc dendrites during the electroplating / detaching process of zinc and other metals, which causes the large volume change of the electrode, and solves the problem of poor interfacial stability of the zinc and other metal negative electrode. The selection of the fluorine-containing molecular structure can promote the artificial SEI layer to participate in the formation of the in-situ SEI layer on the electrode surface during the reduction process, generate fluorine-containing metal compounds, improve the interfacial stability of the electrode, and thus improve the cycle stability of the metal battery.

[0039] 2. The polymer artificial SEI layer solution is coated on the metal electrode to form a polymer artificial SEI layer, and a modified metal electrode is obtained. The polymer artificial SEI layer with self-healing and high elasticity can self-heal and repair the damage of the electrode surface interface caused by the long-term cycling of the battery, and its high elastic deformation capacity can adapt to the rough interface caused by the uneven deposition of the electrode, so as to improve the integrity and intimacy of the electrode and the SEI layer interface, effectively prevent the side reaction caused by the direct contact between the zinc and other metal electrode and the electrolyte, and thus improve the utilization rate of the metal negative electrode. The polymer artificial SEI layer with single-ion conductivity can selectively promote the Zn 2+The migration of metal ions is inhibited while the migration of anions is inhibited, so as to achieve the purpose of regulating the flow of zinc ions to realize uniform deposition of zinc and other metals; the modified metal electrode is applied as a negative electrode in a water-based metal battery, realizing super-long stable cycle performance under large current density and deposition capacity, indicating that the fluorine-rich self-healing single-ion conductor polymer artificial SEI layer has broad application prospects in the stable metal electrode of zinc metal and other (alkali) metal batteries. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without any creative effort.

[0041] Figure 1 Raman spectra of the polymer artificial SEI layer solution prepared in Example 1, the product after TDFND and LiAlH4 crosslinking in step S2, and pure TDFND;

[0042] Figure 2 Variation curves of the elastic modulus and hardness of the polymer artificial SEI layer modified zinc metal electrode with the cutting depth in Example 3;

[0043] Figure 3 Cycle performance diagram of the zinc-zinc symmetric button cell assembled in Example 4;

[0044] Figure 4 Cycle-capacity diagram of the zinc-sodium vanadate full cell assembled in Example 5. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present application will be described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort fall within the scope of protection of the present application.

[0046] In order to better understand the present application and not limit the scope of the present application, all numbers, percentages and other numerical values used in this application to express amounts, percentages and other values should be understood as being modified by the word "about" in all cases. Therefore, unless specifically stated otherwise, the numerical parameters set forth in the specification and attached claims are approximations. They can vary depending on different desired properties sought to be obtained by the ideal properties. Each numerical parameter should be construed as being open-ended in the context of the claims and obtaining the desired properties.

[0047] It is noted that the order of description of the examples below is not intended to imply a preference. Furthermore, in this description, the term "include" means "including but not limited to". Various embodiments of the present application can exist in a variety of forms; it should be understood that the description of a specific embodiment is merely an example and should not be construed as a limitation on the scope of the application; therefore, it should be considered that the description of the range has been specifically disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single values within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated in this document, it refers to any cited number (fraction or integer) within the indicated range.

[0048] The polymer artificial SEI layer solution provided by the embodiments of the present application comprises a fluorine-containing monomer, a crosslinking agent, an organic solvent, and a polymer film forming agent.

[0049] The fluorine-containing monomer comprises at least one of a partially fluorine-substituted alcohol-hydroxyl-terminated alkane and a perfluorine-substituted alcohol-hydroxyl-terminated alkane.

[0050] The crosslinking agent comprises at least one of silicon, zinc, aluminum, and boron.

[0051] In some embodiments, the partially fluorine-substituted alcohol-hydroxyl-terminated alkane comprises at least one of tetrafluoropropyl alcohol, hexafluorobutyl alcohol, 4-fluoro-1-butyl alcohol, and 3,3-difluorocyclobutanol.

[0052] In some embodiments, the perfluorine-substituted alcohol-hydroxyl-terminated alkane comprises at least one of octafluoro-1,6-hexanediol, 2,2-difluoro-1,3-propanediol, 2,2,3,3-tetrafluoro-1,4-butanediol, 1H,1H,8H,8H-perfluoro-1,8-octanediol (also known as 1H,1H,8H,8H-dodecafluoro-1,8-octanediol), 1H,1H,9H,9H-perfluoro-1,9-nonanediol, and 1H,1H,10H,10H-perfluoro-1,10-decanediol.

[0053] In some embodiments, the crosslinking agent comprises at least one of silicon tetrachloride, zinc chloride, lithium aluminum hydride, lithium borohydride, and sodium borohydride. The crosslinking agent is added in the form of a solid or a solution. If the crosslinking agent is selected from a compound containing a metal, such as lithium aluminum hydride, lithium borohydride, and sodium borohydride, the dynamic crosslinking product has a higher metal single-ion transference number in the corresponding metal battery, such as a lithium metal battery and a sodium metal battery.

[0054] In some embodiments, the polymer film-forming agent comprises at least one of polyethylene oxide (PEO), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), and polyvinyl alcohol (PVA).

[0055] In some embodiments, the organic solvent comprises at least one of N-methylpyrrolidone, dimethyl sulfoxide, ethylene glycol dimethyl ether, and N,N-dimethylformamide.

[0056] Based on the same inventive concept, the present application also provides a preparation method of the above-mentioned polymer artificial SEI layer solution, comprising the following steps:

[0057] S1. Dispersing a fluorine-containing monomer in an organic solvent under an inert gas to obtain a mixed solution;

[0058] S2. Adding a crosslinking agent to the mixed solution and stirring to perform a crosslinking reaction;

[0059] S3. Adding the mixed solution after the crosslinking reaction to a polymer film-forming agent and stirring to obtain the polymer artificial SEI layer solution.

[0060] It should be noted that the preparation method of the polymer artificial SEI layer solution of the present application, the fluorine-containing monomer comprises a partially fluorine-substituted alcohol-hydroxyl-terminated alkane and / or a perfluorine-substituted alcohol-hydroxyl-terminated alkane. Specifically, the partially fluorine-substituted alcohol-hydroxyl-terminated alkane is partially hydrogen-substituted on a fluorine-substituted alkane chain and terminated with a hydroxyl group; the perfluorine-substituted alcohol-hydroxyl-terminated alkane is all hydrogen-substituted on a fluorine-substituted alkane chain and terminated with a hydroxyl group; the alcohol-hydroxyl group of the terminated alkane can form a dynamic bond with silicon, zinc, aluminum, and boron elements in the crosslinking agent to perform a dynamic crosslinking reaction; the mixed solution after the crosslinking reaction is added to a polymer film-forming agent to obtain a fluorine-containing self-healing monomer polymer artificial SEI layer solution. Coating the fluorine-containing self-healing monomer polymer artificial SEI layer solution of the present application on a metal electrode forms a polymer artificial SEI layer, which can prevent direct contact between the metal electrode such as zinc and an electrolyte and inhibit the occurrence of side reactions between the two; at the same time, the fluorine structure in the fluorine-containing self-healing monomer polymer artificial SEI layer solution participates in the formation of an in-situ solid-state electrolyte on the surface of the metal electrode, effectively improving the stability of the metal electrode and improving the cycle stability of the metal secondary battery such as zinc under a large current density and deposition capacity; in addition, the design of the fluorine-containing self-healing monomer polymer artificial SEI layer allows Zn 2+ metal ions to pass through while preventing large-scale migration of salt anions, thereby achieving the purpose of regulating the flow of zinc metal ions and promoting uniform deposition. In addition, the synthesis steps of the polymer artificial SEI layer solution are simple, the conditions are mild, the cost is low, and the repeatability is strong, and it can be used for large-scale preparation.

[0061] Specifically, the fluorine-containing monomer (octafluoro-1, 6-hexanediol) and the crosslinking agent (lithium aluminum tetrahydride) undergo a dynamic cross-linking reaction as shown below:

[0062]

[0063] In some embodiments, the inert gas includes at least one of argon, helium, and nitrogen.

[0064] In some embodiments, the fluorine-containing monomer is added to the organic solvent and stirred at room temperature for 1-4 hours, i.e., the fluorine-containing monomer is dispersed in the organic solvent to obtain a mixed solution.

[0065] In some embodiments, in step S2, the cross-linking product has different states under different stirring temperatures, and the stirring temperature is preferably 30-70°C.

[0066] Specifically, the cross-linking agent is added in different ways, and the cross-linking degree of the cross-linking product is different. The addition method of the cross-linking agent is preferably feeding, injection, or dropwise addition.

[0067] In some embodiments, the mixed solution after the cross-linking reaction is further filtered before being added to the polymer film-forming agent.

[0068] Specifically, the mixed solution after the cross-linking reaction contains polymers with different cross-linking chain lengths. In order to prepare a more uniform artificial SEI layer, the mixed solution after the cross-linking reaction is filtered, and then the filtered mixed solution is added to the polymer film-forming agent and stirred to obtain a polymer artificial SEI layer solution. The filtering method is preferably vacuum filtration, natural filtration, or PTFE filter membrane filtration.

[0069] In some embodiments, in the step of adding the mixed solution after the cross-linking reaction to the polymer film-forming agent, the mass ratio of the mixed solution after the cross-linking reaction to the polymer film-forming agent is (4-9):1.

[0070] If the mixed solution after the cross-linking reaction is filtered, and then the filtered mixed solution is added to the polymer film-forming agent, the mass ratio of the filtered mixed solution to the polymer film-forming agent is (4-9):1.

[0071] The artificial SEI layer film formed under different mass ratios has different elasticity. The mass ratio of the mixed solution after the cross-linking reaction to the polymer film-forming agent is preferably 4:1, 5:1, 6:1, 7:1, 8:1, or 9:1.

[0072] In some embodiments, the mass ratio of the fluorine-containing monomer, the organic solvent, and the cross-linking agent is (0.6-0.8):(2000-3000):(5-15).

[0073] Specifically, further by adjusting and screening the mass ratio of the fluorine-containing monomer and the cross-linking agent, direct contact between the metal electrode such as zinc and the electrolyte is further inhibited, occurrence of side reactions of the two is inhibited, and stability of the metal electrode is further effectively improved, and cycle stability of the metal secondary battery such as zinc under a large current density and deposition capacity is improved.

[0074] In some embodiments, SEI films formed by the mixed solution after the cross-linking reaction have different phase stabilities, and the concentration of the mixed solution after the cross-linking reaction is 50-250 mg / ml.

[0075] In some embodiments, the cross-linking agent such as LiAlH4 is first added to the THF solvent to form a THF solution containing the cross-linking agent such as LiAlH4, and then the THF solution containing the cross-linking agent such as LiAlH4 is added to the mixed solution to perform the cross-linking reaction.

[0076] In some embodiments, the polymer film-forming agent is first added to the NMP to form an NMP solution containing the polymer film-forming agent, and then the NMP solution containing the polymer film-forming agent is mixed with the mixed solution after the cross-linking reaction and stirred to obtain the polymer artificial SEI layer solution.

[0077] Based on the same inventive concept, the application further provides a modified metal electrode, and a preparation method of the modified metal electrode, which comprises the following steps:

[0078] The polymer artificial SEI layer solution prepared by the above preparation method is coated on the metal electrode, and the organic solvent is volatilized to obtain the modified metal electrode.

[0079] It can be understood that the polymer artificial SEI layer solution is coated on the metal electrode to form a polymer artificial SEI layer on the metal electrode, and specifically, the monomer with a fluorine-containing alcohol hydroxyl end cap and the cross-linking agent are dynamically cross-linked to form a self-healing single-ion conductor polymer artificial SEI layer.

[0080] In some embodiments, different coating methods for preparing the polymer artificial SEI layer have different film uniformity and controllable thickness, and the polymer artificial SEI layer solution coating method is preferably flow casting, spin coating, or pressing.

[0081] In some embodiments, the metal electrode includes any one of a lithium metal electrode, a sodium metal electrode, a zinc metal electrode, and an aluminum metal electrode.

[0082] In some embodiments, different amounts of the polymer artificial SEI layer solution are added to form polymer artificial SEI layers with different thicknesses, and preferably, 5-20 μL of the polymer artificial SEI layer solution is coated on the metal electrode.

[0083] In some embodiments, the diameter of the metal electrode is 8-16 mm.

[0084] Based on the same inventive concept, the application further provides an application of the modified metal electrode as a negative electrode in preparation of an aqueous metal battery.

[0085] If the modified metal electrode is a modified lithium metal electrode, the corresponding battery is an aqueous lithium metal battery;

[0086] If the modified metal electrode is a modified sodium metal electrode, the corresponding battery is an aqueous sodium metal battery;

[0087] If the modified metal electrode is a modified zinc metal electrode, the corresponding battery is an aqueous zinc metal battery;

[0088] If the modified metal electrode is a modified aluminum metal electrode, the corresponding battery is an aqueous aluminum metal battery.

[0089] The application of the modified metal electrode in the aqueous metal battery realizes the ultra-long stable electrochemical performance under large current density and deposition capacity, indicating that the polymer artificial SEI layer has a broad application prospect in the aqueous metal battery system.

[0090] Based on the same inventive concept, the application further provides an aqueous metal battery comprising a negative electrode, which is the modified metal electrode.

[0091] In some embodiments, the modified metal electrode is a modified zinc metal electrode;

[0092] The aqueous metal battery further comprises a positive electrode, a separator and an electrolyte;

[0093] In some embodiments, the positive electrode of the aqueous zinc metal battery is made of a material with low cost, stable structure and good rate performance, preferably, the positive electrode comprises any one of manganese dioxide, cobalt-nickel sulfide, vanadium pentoxide, ammonium vanadate and sodium vanadate.

[0094] In some embodiments, the separator can separate the anode and cathode materials and remain stable during the charging and discharging cycle, and is made of a material with ion conductivity and electronic insulation, preferably a PP separator, a cellulose separator and a glass fiber separator.

[0095] In some embodiments, the electrolyte is suitable for maintaining high ionic conductivity and low viscosity of the electrolyte, preferably, the concentration of the electrolyte is 0.5-3 mol / L, and the electrolyte comprises any one of zinc sulfate aqueous solution, zinc chloride aqueous solution, zinc triflate aqueous solution, zinc perchlorate aqueous solution, zinc hexafluorosilicate aqueous solution and bis-trifluoromethanesulfonimide zinc aqueous solution.

[0096] The modified zinc metal electrode has the following advantages:

[0097] The fluorine-rich self-healing single-ion conductor polymer artificial SEI layer of the application can better cater to and inhibit the generation of zinc dendrites in the plating / delamination process of zinc metal, causing large volume changes of the electrode, solve the problem of poor interface stability of the zinc negative electrode surface, on the premise of ensuring high ionic conductivity, high mechanical properties, low cost, environmental protection and other advantages; the designed polymer artificial SEI layer with self-healing and high elasticity can self-heal and repair the damage of the artificial SEI layer caused by the long-term cycling of the electrode surface interface, and its high elastic deformation capacity can adapt to the rough interface caused by the uneven deposition of the electrode, so that the integrity and intimacy of the electrode and the SEI layer interface can effectively prevent the side reactions caused by the direct contact of the zinc metal electrode and the electrolyte, thereby improving the utilization rate of the metal negative electrode; the designed polymer artificial SEI layer with single-ion conductivity can selectively promote the migration of Zn 2+ and inhibit the migration of anions, so as to achieve the purpose of regulating the flow of zinc ions to realize the uniform deposition of zinc metal. In the design process of the artificial SEI layer, the selection of fluorine-containing molecular structure can promote the participation of the artificial SEI layer in the formation of the in-situ SEI layer on the electrode surface during the reduction process, generate fluorine-containing metal compounds, improve the stability of the electrode surface interface, and thus improve the cycle stability of the metal battery; the zinc metal negative electrode modified by the fluorine-rich self-healing single-ion conductor polymer artificial SEI layer has achieved super-long stable cycle performance under large current density and deposition capacity when applied in the aqueous zinc metal battery, indicating that the fluorine-rich self-healing single-ion conductor polymer artificial SEI layer has broad application prospects in the stable metal electrode of zinc metal and other (alkali) metal batteries.

[0098] The following further illustrates the preparation method of the polymer artificial SEI layer solution, the modified metal electrode, and the aqueous metal battery of the application with specific examples. This part further illustrates the content of the application in combination with specific examples, but should not be understood as a limitation of the application. If not specifically stated, the technical means used in the examples is the conventional means familiar to those skilled in the art. Unless specifically stated, the reagents, methods and equipment used in the application are conventional reagents, methods and equipment in the art.

[0099] Example 1

[0100] The embodiment provides a polymer artificial SEI layer solution, which comprises 0.8 mg 1H, 1H, 9H, 9H-perfluoro-1, 9-nonanediol (TDFND), 3 ml ethylene glycol dimethyl ether (DME), 300 μL of 1M (i.e. 1 mol / L) LiAlH4 THF solution (i.e. 1M LiAlH4 THF solution is obtained by dissolving LiAlH4 in tetrahydrofuran (THF)), 2 mL of NMP (N-methyl pyrrolidone) solution of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) (i.e. the NMP solution of PVDF-HFP is obtained by dissolving PVDF-HFP in 2 mL of NMP); wherein the mass ratio of TDFND and PVDF-HFP is 8:1.

[0101] The preparation method of the polymer artificial SEI layer solution comprises the following steps:

[0102] S1, 0.8 mg 1H, 1H, 9H, 9H-perfluoro-1, 9-nonanediol (TDFND) and 3 ml ethylene glycol dimethyl ether (DME) are added to a glass bottle, the glass bottle is sealed in an argon-filled glove box, and stirring is performed at room temperature for 1 hour until the TDFND is completely dispersed in the ethylene glycol dimethyl ether (DME) to obtain a mixed solution;

[0103] S2, 300 μL of 1M LiAlH4 THF solution is added dropwise into the mixed solution in step S1, and stirring is performed at 50°C for 6h to perform a crosslinking reaction;

[0104] S3, the mixed solution after the crosslinking reaction in step S2 is filtered with a PTFE filter membrane, and then the filtered mixed solution is added into the NMP solution of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), and stirring is performed for 15h to obtain the polymer artificial SEI layer solution; wherein the mass ratio of TDFND and PVDF-HFP is 8:1.

[0105] The Raman diagrams of the film formed by dropping the polymer artificial SEI layer solution prepared in Example 1 on a flat substrate after volatilizing the solvent, the product after the crosslinking of TDFND and LiAlH4 in step S2, and pure TDFND are as shown in Figure 1 . Figure 1 TDFND and Al crosslinking in the figure is the product after crosslinking in step S2, Pure TDFND is pure TDFND, and TDFND and Al crosslinking@PVDF-HFP is the polymer artificial SEI layer solution prepared in Example 1. Figure 1 The right side graph in the figure is an enlarged view of 800-1300 cm -1 in the left side graph.

[0106] From Figure 1As can be seen, the peak at 3200cm -1 ~3500cm -1 belonging to O-H bond is obviously weakened, and the peak at 1079cm -1 ~1096cm -1 belonging to Al-O bond is obviously enhanced compared with the Raman of pure TDFND, indicating the formation of Al-O dynamic bond.

[0107] Embodiment 2

[0108] The embodiment provides a polymer artificial SEI layer solution, which comprises 0.6 mg of 2,2-difluoro-1,3-propanediol, 3 ml of ethylene glycol dimethyl ether (DME), 250 muL of 1M (i.e. 1 mol / L) LiBH4 THF solution (i.e. LiBH4 is dissolved in tetrahydrofuran (THF) to obtain the 1M LiBH4 THF solution), 4 ml of acetonitrile solution of polyethylene oxide (PEO) (i.e. PEO is dissolved in 4 ml of acetonitrile to obtain the acetonitrile solution of PEO); wherein the mass ratio of 2,2-difluoro-1,3-propanediol and PEO is 8:1.

[0109] The preparation method of the polymer artificial SEI layer solution comprises the following steps:

[0110] S1, 0.6 mg of 2,2-difluoro-1,3-propanediol and 3 ml of ethylene glycol dimethyl ether (DME) are added to a glass bottle, the glass bottle is sealed in an argon-filled glove box, and stirring is performed at room temperature for 1 hour until the 2,2-difluoro-1,3-propanediol is completely dispersed in the ethylene glycol dimethyl ether (DME) to obtain a mixed solution;

[0111] S2, 250 muL of 1M (i.e. 1 mol / L) LiBH4 THF solution (i.e. LiBH4 is dissolved in tetrahydrofuran (THF) to obtain the 1M LiBH4 THF solution) is added dropwise into the mixed solution in step S1, and stirring is performed at 30 DEG C for 6h to perform a crosslinking reaction;

[0112] S3, the mixed solution after the crosslinking reaction in step S2 is filtered with a PTFE filter membrane, and the filtered mixed solution is added into the acetonitrile solution of polyethylene oxide (PEO) (i.e. PEO is dissolved in acetonitrile to obtain the acetonitrile solution of PEO), and stirring is performed for 15h to obtain the polymer artificial SEI layer solution; wherein the mass ratio of 2,2-difluoro-1,3-propanediol and PEO is 8:1.

[0113] Embodiment 3

[0114] The embodiment of the present application provides a preparation method of a modified zinc metal electrode, comprising the following steps:

[0115] 15 μL of the polymer artificial SEI layer solution prepared in Example 1 was added dropwise to the surface of a zinc metal electrode (a round sheet with a diameter of 1.2 cm and a thickness of 100 μm), and was cast coated. After the organic solvent was volatilized, a polymer artificial SEI layer was formed on the surface of the zinc metal electrode, i.e., a modified zinc metal electrode.

[0116] The modified zinc metal electrode of Example 3 was subjected to depth and modulus / hardness measurement, and the results are shown in Figure 2 . Specifically, the modified zinc metal electrode of Example 3 was cut using a conical knife, and the change in elastic modulus and hardness with the cutting depth was tested.

[0117] Figure 2 The photos before and after the cutting indentation test are shown in Figure 2 . As can be seen from the photos, the modified zinc metal electrode of Example 3 can repair the damage to the SEI layer within 5 minutes, and the SEI layer has a high elastic modulus and a low hardness, and the thickness is only about 300 nm.

[0118] Example 4

[0119] The example of the present application provides a water-based zinc metal battery, which is a zinc-zinc symmetric battery. The positive electrode and the negative electrode are both the modified zinc metal electrode of Example 3. The separator is selected from glass fiber. The electrolyte is a 2 mol L -1 aqueous zinc sulfate solution. The battery is assembled into a CR2032 type button cell. The structure of the assembled battery is: positive electrode shell, modified zinc metal electrode, electrolyte, separator, electrolyte, modified zinc metal electrode, gasket, spring and negative electrode shell.

[0120] Example 5

[0121] The example of the present application provides a water-based zinc metal battery, which is a zinc-sodium vanadate full battery. The negative electrode is the modified zinc metal electrode of Example 3. The positive electrode is sodium vanadate. The separator is selected from glass fiber. The electrolyte is a 2 mol L -1 aqueous zinc sulfate solution. The battery is assembled into a CR2032 type button cell. The structure of the assembled battery is: positive electrode shell, positive electrode sheet with active material of sodium vanadate, electrolyte, separator, electrolyte, modified zinc metal electrode, gasket, spring and negative electrode shell.

[0122] The zinc-zinc symmetric button cell assembled in Example 4 was subjected to charge-discharge test on a new wei battery test system at room temperature. The test conditions of the zinc-zinc symmetric battery are: current density is 5 mA cm -2 , and deposition capacity is 5 mAh cm -2 . The cycle performance chart is shown in Figure 3 .

[0123] As can be seen from Figure 3 , the overpotential of the zinc-zinc symmetric button cell assembled in Example 4 was only 278 mV after 1600 hours of cycling.

[0124] The zinc-sodium vanadate full cell assembled in Example 5 was subjected to charge-discharge test at room temperature on a Neware battery test system, and the test conditions of the zinc-sodium vanadate full cell were that the charge-discharge voltage interval was 0.2-1.6 V, and the charge-discharge test was carried out at a current density of 1 A g -1 -1, and its cycle-capacity diagram is shown in Figure 4 .

[0125] As can be seen from Figure 4 , under this condition, the specific capacity of the electrode material can reach 256 mAh g -1 , and it can be stably cycled for more than 1400 cycles with a coulombic efficiency close to 100%.

[0126] The above merely describes preferred embodiments of the present application but should not be used to restrict the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A polymer-based artificial SEI layer solution, characterized in that, Including fluorinated monomers, crosslinking agents, organic solvents, and polymer film-forming agents; The fluorinated monomers include perfluorinated substituted alcohol hydroxyl-terminated alkanes; The perfluorinated hydroxyl-terminated alkanes include at least one of octafluoro-1,6-hexanediol, 2,2-difluoro-1,3-propanediol, 2,2,3,3-tetrafluoro-1,4-butanediol, 1H,1H,8H,8H-perfluoro-1,8-octanediol, 1H,1H,9H,9H-perfluoro-1,9-nonanediol, and 1H,1H,10H,10H-perfluoro-1,10-decanediol. The crosslinking agent includes a crosslinking agent containing at least one element selected from silicon, zinc, aluminum, and boron; The crosslinking agent includes at least one of lithium aluminum hydride, lithium boron hydride, and sodium borohydride. Under an inert gas atmosphere, fluorine-containing monomers are dispersed in an organic solvent to obtain a mixture; Add a crosslinking agent to the mixture, stir, and carry out a crosslinking reaction; The cross-linked mixture is added to the polymer film-forming agent and stirred to obtain the polymer artificial SEI layer solution. The mass ratio of the fluorinated monomer, organic solvent, and crosslinking agent is (0.6~0.8):(2000~3000):(5~15).

2. The polymer-based artificial SEI layer solution as described in claim 1, characterized in that, The polymer film-forming agent includes at least one of polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, and polyvinyl alcohol; And / or, the organic solvent includes at least one of N-methylpyrrolidone, dimethyl sulfoxide, ethylene glycol dimethyl ether, and N,N-dimethylformamide.

3. A method for preparing a polymer-based artificial SEI layer solution as described in any one of claims 1 to 2, characterized in that, Includes the following steps: Under an inert gas atmosphere, fluorine-containing monomers are dispersed in an organic solvent to obtain a mixture; Add a crosslinking agent to the mixture, stir, and carry out a crosslinking reaction; The cross-linked mixture is added to the polymer film-forming agent and stirred to obtain the polymer artificial SEI layer solution.

4. The method for preparing the polymer artificial SEI layer solution as described in claim 3, characterized in that, In the step of adding a crosslinking agent to the mixture and stirring, the stirring temperature is 30~70℃.

5. The method for preparing the polymer artificial SEI layer solution according to any one of claims 3 to 4, characterized in that, In the step of adding the cross-linked mixture to the polymer film-forming agent, the mass ratio of the cross-linked mixture to the polymer film-forming agent is (4~9):

1. And / or, the concentration of the mixture after the crosslinking reaction is 50~250 mg / ml; And / or, the inert gas includes at least one of argon, helium, and nitrogen; And / or, before adding the crosslinked mixture to the polymer film-forming agent, the crosslinked mixture may also be filtered.

6. A modified metal electrode, characterized in that, The method for preparing the modified metal electrode includes the following steps: The polymer artificial SEI layer solution prepared by any one of the preparation methods described in claims 3 to 5 is coated onto the metal electrode to obtain the modified metal electrode.

7. The modified metal electrode as described in claim 6, characterized in that, The metal electrode includes any one of lithium metal electrode, sodium metal electrode, zinc metal electrode, and aluminum metal electrode; And / or, coat the metal electrode with 5~20 μL of polymer artificial SEI layer solution; And / or, the diameter of the metal electrode is 8~16 mm.

8. The application of a modified metal electrode as described in any one of claims 6 to 7 as a negative electrode in the preparation of an aqueous metal battery.

9. A water-based metal battery, characterized in that, Includes a negative electrode, which is the modified metal electrode as described in claim 6 or 7.

10. The aqueous metal battery as described in claim 9, characterized in that, The modified metal electrode is a modified zinc metal electrode; The aqueous metal battery also includes a positive electrode, a separator, and an electrolyte; The positive electrode comprises any one of manganese dioxide, cobalt nickel sulfide, vanadium pentoxide, ammonium vanadate, and sodium vanadate. The diaphragm includes any one of PP diaphragm, cellulose diaphragm, and glass fiber diaphragm. The electrolyte includes any one of the following: zinc sulfate aqueous solution, zinc chloride aqueous solution, zinc trifluoromethanesulfonate aqueous solution, zinc perchlorate aqueous solution, zinc hexafluorosilicate aqueous solution, and bis(trifluoromethanesulfonyl)imide zinc aqueous solution; The concentration of the electrolyte is 0.5 ~ 3 mol / L.

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