Electrolyte, and alkali metal secondary batteries containing it

Abstract

This application provides an electrolyte and an alkali metal secondary battery containing the same. [Solution] The electrolyte comprises a combination of an alkali metal salt and a solvent, the solvent comprising a combination of an ionic liquid, a weakly polar solvent and an inert diluent, the weakly polar solvent being a cyclic ether solvent. The electrolyte has low viscosity, good flame retardancy and wetting properties, and if the artificial SEI film on the surface of the alkali metal anode is damaged, it is repairable in situ, ensuring the long-term cycle stability of the battery. By pre-coating the surface of the alkali metal anode of the alkali metal secondary battery with a polyionic liquid artificial SEI film, it is advantageous to suppress side reactions between the electrolyte and the electrode, and furthermore, the consumption of the electrolyte during the process of forming the SEI film can be reduced. At the same time, the electrostatic shielding effect of the ionic liquid cations in the polymer segment homogenizes the ion distribution, promotes uniform ion deposition, mitigates the growth of metal dendrites, and further improves the battery's cycle life and Coulomb efficiency.

Description

[Technical Field]

[0001] This application relates to the technical field of alkali metal secondary batteries, and more particularly to an electrolyte and an alkali metal secondary battery containing the same. [Background technology]

[0002] In recent years, with the rapid development of the electric-powered new energy vehicle sector, people are placing increasingly high demands on the development of power energy storage batteries. Novel energy storage batteries need to provide higher energy capacity in a limited volume and mass to solve the problem of concerns about driving range during long-distance driving. Therefore, there is currently an urgent need to develop energy storage batteries with higher energy density to meet application needs. However, commercially available lithium-ion batteries have a finite theoretical specific capacity (372mAhg) of graphite-based carbon anode materials. -1 Because it is limited to ), it becomes difficult to break through the current energy density of lithium-ion batteries. Alkali metals are used as anode materials for batteries, for example, lithium metal has an extremely high theoretical specific capacity (3860mAhg). -1 ), low electrochemical potential (-3.04V vs. standard hydrogen electrode), and low density (0.534 g / cm³). -3 Alkali metal negative electrodes have advantages such as those listed above, and can significantly improve the energy density of energy storage batteries, which is expected to solve the problem of concerns about the driving range of new energy vehicles and has a wide range of application prospects. However, alkali metal negative electrodes have many problems that are difficult to solve. First, due to the active chemical properties of alkali metals, side reactions with the electrolyte become serious, and the loss of active materials and the consumption of electrolyte during the cycle process tend to occur, resulting in a low Coulomb efficiency of the battery and a short cycle life. In addition, alkali metals can cause uncontrollable dendrite growth during repeated cycle processes, which can pierce the separator and cause an internal short circuit in the battery, leading to safety accidents such as battery combustion and explosion.

[0003] By using an artificial solid electrolyte interface (SEI), interfacial side reactions between the electrode and the electrolyte can be effectively suppressed, and the growth problem of metal dendrites can be mitigated, thereby improving the Coulomb efficiency and cycle performance of alkali metal secondary batteries to some extent. However, conventional artificial SEI films are mainly composed of organic or inorganic materials, with organic materials having poor ionic conductivity and stability, and inorganic materials having poor flexibility. At the same time, the significant volume expansion of the alkali metal electrode during the cycling process easily leads to rupture and detachment of the artificial SEI film, making it difficult to ensure further long-term cycle stability of the battery. Furthermore, conventional electrolyte systems often use carbonate esters or ether-based solvents, which are prone to side reactions with the alkali metal surface, causing problems such as low Coulomb efficiency and poor cycle stability of the battery. At the same time, such electrolyte systems are highly flammable, increasing safety risks during battery use.

[0004] CN109888182A discloses an in-situ protected alkali metal electrode, a method of manufacture, and use, comprising an alkali metal material and a protective coating layer which is an amalgam formed by coating the alkali metal surface with mercury. CN115863769A discloses a fluorinated carbonate-based electrolyte and a lithium metal battery that form a lithium fluoride-rich solid electrolyte interface film on the surface of the electrodes of a lithium metal battery. Both the amalgam and lithium fluoride are inorganic materials, and such inorganic materials have poor flexibility as an alkali metal protective coating layer, are prone to rupture and detachment during use, and result in poor battery stability. Furthermore, the fluorinated carbonate-based electrolyte is prone to side reactions with the alkali metal surface and is highly flammable, posing safety problems.

[0005] Therefore, in order to improve the safety, Coulomb efficiency, and cycle life of alkali metal secondary batteries, there is an urgent need to develop alkali metal secondary batteries in which the electrolyte possesses properties such as flame retardancy, while suppressing interfacial side reactions and metal dendrite growth using a more stable artificial SEI film. [Overview of the project] [Problems to be Solved by the Invention]

[0006] The following outlines the subject matter described in detail in this specification. This outline is not intended to limit the scope of the claims.

[0007] The present application provides an electrolyte solution and an alkali metal secondary battery containing the same. The electrolyte solution can perform in-situ repair when the artificial SEI film on the surface of the alkali metal negative electrode is damaged, which is advantageous for further improving the stability of the alkali metal negative electrode, and also has certain flame retardancy to enhance the safety of the battery. The alkali metal secondary battery can effectively improve problems such as dendrite growth and interfacial side reactions of the alkali metal negative electrode, and significantly improve the Coulombic efficiency, cycle life and safety of the battery. [Means for Solving the Problems]

[0008] As a first aspect, the present application provides an electrolyte solution comprising a combination of an alkali metal salt and a solvent, wherein the solvent comprises a combination of an ionic liquid, a weakly polar solvent and an inert diluent, and the weakly polar solvent is selected from any one of the compounds having the following structure or a combination of at least two thereof. [Chemical Formula]

[0009] provided that R 11 , R 13 , R 15 , R 17 , R 19 , R 21 are each independently any one selected from a single bond, a substituted or unsubstituted C1 to C10 linear or branched alkylene group, and a substituted or unsubstituted C3 to C10 cycloalkylene group, and R 11 , R 13 , R 15 , R 17 , R 19 , R 21If it is a single bond, the oxygen atom is directly bonded to the cycloalkane.

[0010] R 12 , R 14 , R 16 , R 18 , R 20 , R 22 Each of these is independently selected from either a substituted or unsubstituted C1-C10 linear or branched alkyl group, or a substituted or unsubstituted C3-C10 cycloalkyl group.

[0011] R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 20 , R 21 , R 22 Of these, each of the substitution substituents is independently selected from at least one of the following: a deuterium atom, a halogen, a nitro group, an amino group, a carboxyl group, Z1-COO-, a linear or branched alkyl group of C1-C10, an alkenyl group of C2-C10, -O-Z2, an aryl group of C6-C30, or a heteroaryl group of C3-C30, wherein Z1 and Z2 are independently selected from any one of the linear or branched alkyl groups of C1-C10.

[0012] The electrolyte according to this application, by using a flame-retardant ionic liquid, a low-viscosity weakly polar solvent, and an inert diluent, combines good flame retardancy, low viscosity, and good penetration properties. This solves the problems of current ionic liquid electrolytes, such as high cost, high viscosity, high melting point, low ionic conductivity, and poor penetration properties, while promoting the preferential reduction of anions and ionic liquid cations on the surface of the alkali metal anode. It forms an SEI film rich in inorganic and organic substances such as LiF, Li2O, and Li3N. If the artificial SEI film on the surface of the alkali metal anode is damaged, it can be repaired in situ. This improves the cycle life of the alkali metal secondary battery, ensures the long-term cycle stability of the battery, and further improves the Coulomb efficiency and safety of the alkali metal secondary battery.

[0013] In this application, C1 to C10 may each be independently C1, C2, C3, C4, C5, C6, C7, C8, C9, or C10.

[0014] The aforementioned C3 to C10 may each be independently C3, C4, C5, C6, C7, C8, C9, or C10.

[0015] The aforementioned C2 to C10 may each be independently C2, C3, C4, C5, C6, C7, C8, C9, or C10.

[0016] The aforementioned C6 to C30 may each be independently C6, C7, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, C18, C19, C22, C24, C26, C28, C29, or C30, etc.

[0017] The aforementioned C3 to C30 may each be independently C3, C4, C5, C6, C7, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, C18, C19, C22, C24, C26, C28, C29, or C30, etc.

[0018] In this application, the linear or branched alkylene groups of C1 to C10 (for example, C1, C2, C3, C4, C5, C6, C7, C8, C9, or C10) include, but are not limited to, methylene groups, ethylene groups, n-propylene groups, isopropylene groups, n-butylene groups, isobutylene groups, tert-butylene groups, n-pentylene groups, isopentylene groups, neopentylene groups, tert-pentylene groups, n-hexylene groups, n-octylene groups, n-heptylene groups, n-nonylene groups, or n-decylene groups.

[0019] In this application, the cycloalkylene groups of C3 to C10 (for example, C3, C4, C5, C6, C7, C8, C9, or C10) include, but are not limited to, cyclopropylene, cyclobutylene, cyclopentylene, cyclohexylene, or adamantylene groups.

[0020] In this application, the linear or branched alkyl groups of C1 to C10 (for example, C1, C2, C3, C4, C5, C6, C7, C8, C9, or C10) include, but are not limited to, methyl groups, ethyl groups, n-propyl groups, isopropyl groups, n-butyl groups, isobutyl groups, tert-butyl groups, n-pentyl groups, isopentyl groups, neopentyl groups, tert-pentyl groups, n-hexyl groups, n-octyl groups, n-heptyl groups, n-nonyl groups, or n-decyl groups.

[0021] In this application, the C3-C10 (e.g., C3, C4, C5, C6, C7, C8, C9, or C10) cycloalkyl groups include, but are not limited to, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, an adamantyl group, and the like.

[0022] In this application, the “substituted or unsubstituted” group may be substituted with one substituent or with multiple substituents, and if there are multiple substituents (at least two), the multiple substituents (at least two) are the same or different groups, and the substituents can be attached to any ligable position on the group. When the same expression is mentioned in the following description, it has the same meaning.

[0023] In this application, the halogen may be fluorine, chlorine, bromine, or iodine.

[0024] In this application, the C2-C10 (e.g., C2, C3, C4, C5, C6, C7, C8, C9, or C10) alkenyl groups include, but are not limited to, a vinyl group, a propenyl group, a 1-butenyl group, or a 1-pentenyl group.

[0025] In this application, the aryl groups C6 to C30 (for example, C6, C7, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, C18, C19, C22, C24, C26, C28, C29, or C30, etc.) include, but are not limited to, phenyl, biphenyl, terphenyl, naphthyl, anthryl, phenanthryl, indenyl, fluorenyl, fluorantenyl, triphenylenyl, pyrenyl, perilenyl, chrysenyl, naphthacenyl, or benzophenantrenyl groups.

[0026] In this application, the heteroaryl groups of C3 to C30 (for example, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, C18, C19, C22, C24, C26, C28, C29 or C30, etc.) include heteroatoms containing O, S, N, P or B, etc. Exemplary examples include furyl group, thienyl group, pyrrolyl group, pyridyl group, pyrazinyl group, pyridadinyl group, pyrimidinyl group, triazinyl group, quinolyl group, isoquinolyl group, quinazolinyl group, quinoxalinyl group, synnolinyl group, o-phenant This includes, but is not limited to, loryl groups, imidazolyl groups, thiazolyl groups, oxazolyl groups, benzimidazolyl groups, benzothiazolyl groups, benzoxazolyl groups, benzofuranyl groups, benzothienyl groups, indolyl groups, dibenzofuranyl groups, dibenzothienyl groups, carbazolyl groups and their derivatives (such as N-phenylcarbazolyl groups, N-naphthylcarbazolyl groups, benzocarbazolyl groups, dibenzocarbazolyl groups, indrocarbazolyl groups, azacarbazolyl groups, etc.), phenothiazinyl groups, phenoxazinyl groups, or hydroacridinyl groups.

[0027] The following are preferred technical solutions of the present application, but are not intended to limit the technical solutions relating to the present application. According to the following preferred technical solutions, the objectives and beneficial effects of the present application can be better achieved and realized.

[0028] As a preferred technical option, the weakly polar solvent includes one or at least two of the following: cyclopropyl methyl ether, cyclobutyl ethyl ether, cyclopentyl methyl ether, cyclopentyl ethyl ether, cyclopentyl propyl ether, cyclohexyl methyl ether, cyclohexyl ethyl ether, cyclopentyl trifluoromethyl ether, cyclohexyl trifluoromethyl ether, cycloheptyl ethyl ether, cyclooctyl propyl ether, or cyclooctyl butyl ether.

[0029] In one embodiment, the mass percentage of the weakly polar solvent in the solvent is 10 to 85%, and may be, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or 85%, as well as specific values ​​between these points. For the sake of space and clarity, specific values ​​within the above range are not exhaustively illustrated in this application.

[0030] In one embodiment, the mass percentage of the weakly polar solvent in the solvent is 20-60%, and may be, for example, 20%, 24%, 29%, 34%, 39%, 44%, 49%, 54%, 59%, or 60%, as well as specific values ​​between these points. For the sake of space and clarity, specific values ​​within the above range are not comprehensively illustrated in this application.

[0031] In one embodiment, the alkali metal salt includes one or at least two of the following: lithium salt, sodium salt, or potassium salt.

[0032] In one embodiment, the lithium salt includes one or at least two of the following: bis(fluorosulfonyl)imide lithium, bis(trifluoromethanesulfonyl)imide lithium, hexafluorophosphate lithium, perchlorate lithium, tetrafluoroborate lithium, lithium bisoxalate borate, hexafluoroarsenate lithium, lithium difluorooxalate borate, difluorophosphate lithium, or 4,5-dicyano-2-trifluoromethylimidazole lithium.

[0033] In one embodiment, the sodium salt includes one or at least two of the following: sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium bisoxalate borate, sodium hexafluoroarsenate, sodium difluorooxalate borate, sodium difluorophosphate, or sodium 4,5-dicyano-2-trifluoromethylimidazole.

[0034] In one embodiment, the potassium salt includes one or at least two of the following: potassium bis(fluorosulfonyl)imide, potassium bis(trifluoromethanesulfonyl)imide, potassium hexafluorophosphate, potassium perchlorate, potassium tetrafluoroborate, potassium bisoxalate borate, potassium hexafluoroarsenate, potassium difluorooxalate borate, potassium difluorophosphate, or potassium 4,5-dicyano-2-trifluoromethylimidazole.

[0035] In one embodiment, the concentration of the alkali metal salt in the electrolyte is 0.1 to 6 mol / L, and may be, for example, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, or 6 mol / L, or a specific point value between the above points. For the sake of space and clarity, specific point values ​​included in the above range are not comprehensively illustrated in this application.

[0036] In one embodiment, the concentration of the alkali metal salt in the electrolyte is 0.5 to 2 mol / L, and may be, for example, 0.5 mol / L, 0.7 mol / L, 0.9 mol / L, 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.5 mol / L, 1.7 mol / L, 1.9 mol / L, or 2 mol / L, or a specific point value between the above points. For the sake of space and simplicity, specific point values ​​included in the above range are not comprehensively illustrated in this application.

[0037] In one embodiment, the structure of the ionic liquid is A + [B] - And, however, A + This is one or at least two combinations selected from the following structures.

[0038] [ka]

[0039] However, R 31 , R 32 , R 33 , R 34 , R 35 , R 36 , R 37 , R 38 , R 39 , R 40 , R 41 , R 42 , R 43 , R 44 , R 45 , R 46 , R 47 , R 48 , R 49 , R 50Each of the following is independently selected from substituted or unsubstituted C1-C20 linear or branched alkyl groups, -R'-O-Z3, -O-Ar1, an amino group, substituted or unsubstituted C6-C12 aryl groups, substituted or unsubstituted C3-C12 heteroaryl groups, a cyano group, a nitro group, or a halogen; Z3 is selected from substituted or unsubstituted C1-C10 linear or branched alkyl groups; R' is selected from a single bond, a substituted or unsubstituted C1-C10 linear or branched alkylene group; and if R' is a single bond, the oxygen atom is directly bonded by a single bond, N, N + S + or P + Directly linked to Ar1, Ar1 is one of the following: a substituted or unsubstituted C6-C12 aryl group, or a substituted or unsubstituted C3-C12 heteroaryl group.

[0040] R 31 , R 32 , R 33 , R 34 , R 35 , R 36 , R 37 , R 38 , R 39 , R 40 , R 41 , R 42 , R 43 , R 44 , R 45 , R 46 , R 47 , R 48 , R 49 , R 50 Of Z3, Ar1, and R', each of the substitution substituents is at least one independently selected from halogens.

[0041] A + The form of the above combination in is as follows: Multiple identical A + Structure or different A + The structure is linked by carbon-carbon single bonds, and the plurality is at least two, and the carbon-carbon single bonds are R 31 , R 32 , R 33 , R34 , R 35 , R 36 , R 37 , R 38 , R 39 , R 40 , R 41 , R 42 , R 43 , R 44 , R 45 , R 46 , R 47 , R 48 , R 49 or R 50 is formed by removing one hydrogen atom each from the hydrogen-containing carbon atoms therein, and illustratively, A + includes, but is not limited to, the following structures.

[0042]

Chemical Formula

[0043] provided that R 31 and R' 31 may be the same or different, and R 32 and R' 32 may be the same or different.

[0044] The aforementioned C1 to C20 may each independently be C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, C18, C19 or C20.

[0045] The aforementioned C3 to C12 (for example, C3, C4, C5, C6, C7, C8, C9, C10, C11 or C12) heteroaryl group illustratively includes, but is not limited to, a thienyl group, a benzothienyl group, a thienoimidazolyl group, a thienofuranyl group, a thiazinyl group and the like.

[0046] The aforementioned C6 to C12 may each independently be C6, C7, C8, C9, C10, C11 or C12.

[0047] The aforementioned C1 to C10 may each be independently C1, C2, C3, C4, C5, C6, C7, C8, C9, or C10.

[0048] The aforementioned C3 to C12 may each be independently C3, C4, C5, C6, C7, C8, C9, C10, C11, C12, or C13.

[0049] [B] - FSI - TFSI - BF4 - PF6 - PF2O2 - NO3 - CF3SO3 - , BOB - Or DFOB - It is one of the following, or a combination of at least two.

[0050] In one embodiment, A + This includes one or at least two combinations of the following cations.

[0051] [ka]

[0052] In one embodiment, the mass percentage of the ionic liquid in the solvent is 10 to 85%, and may be, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or 85%, as well as specific values ​​between these points. For the sake of space and clarity, specific values ​​within this range are not comprehensively illustrated in this application.

[0053] In one embodiment, the mass percentage of the ionic liquid in the solvent is 30-70%, and may be, for example, 30%, 34%, 39%, 44%, 49%, 54%, 59%, 64%, or 70%, as well as specific values ​​between these points. For the sake of space and clarity, specific values ​​within this range are not comprehensively illustrated in this application.

[0054] In one embodiment, the inert diluent comprises one or at least two of the following: halogenated ethers, halogenated benzenes, or halogenated alkanes.

[0055] In one embodiment, the halogenated ether includes one or at least two of the following: 1,1,1,3,3,3-hexafluoroisopropyl methyl ether, 2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 2,2,2-trifluoroethyl methyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, methyl nonafluorobutyl ether, or ethyl nonafluorobutyl ether.

[0056] In one embodiment, the halogenated benzene includes fluorobenzene and / or 1,2-difluorobenzene.

[0057] In one embodiment, the halogenated alkane includes one or at least two of the following: dichloromethane, dichloroethane, dichloropropane, dichlorobutane, chloroform, trichloropropane, chlorodifluoromethane, dichlorofluoromethane, or difluoromethane.

[0058] In one embodiment, the mass percentage of the inert diluent in the solvent is 5 to 60%, and may be, for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, or 60%, as well as specific values ​​between these points. For the sake of space and clarity, specific values ​​within this range are not comprehensively illustrated in this application.

[0059] In one embodiment, the mass percentage of the inert diluent in the solvent is 10 to 50%, and may be, for example, 10%, 14%, 19%, 24%, 29%, 34%, 39%, 44%, or 50%, as well as specific values ​​between these points. For the sake of space and clarity, specific values ​​within this range are not comprehensively illustrated in this application.

[0060] In a second aspect, the present application provides an alkali metal secondary battery comprising a negative electrode, a positive electrode, an electrolyte as described in the first aspect, and a separator.

[0061] In one embodiment, the negative electrode includes an alkali metal negative electrode and a negative electrode current collector.

[0062] In one embodiment, the alkali metal anode comprises one of lithium, sodium, or potassium.

[0063] In one embodiment, the negative electrode current collector includes one of the following: copper foil, nickel foil, or nickel-plated steel strip.

[0064] In one embodiment, a polyionic liquid artificial SEI film is coated on the outer surface of the alkali metal anode.

[0065] In one embodiment, the thickness of the polyionic liquid artificial SEI film is 2 to 2000 nm, and may be, for example, 2 nm, 30 nm, 50 nm, 80 nm, 100 nm, 200 nm, 500 nm, 800 nm, 1000 nm, 1200 nm, 1500 nm, 1800 nm, or 2000 nm, as well as specific point values ​​between the above points. For the sake of space and clarity, specific point values ​​included in the above range are not comprehensively illustrated in this application.

[0066] In one embodiment, the material of the polyionic liquid artificial SEI membrane has a structure represented by formula I, formula II, or formula III.

[0067] [ka]

[0068] However, R1, R2, R3, R4, R5, R6, R7, R8, and R9 are each independently selected from a hydrogen atom, a substituted or unsubstituted C1-C10 linear or branched alkyl group, -O-Z4, -O-Ar2, an amino group, a substituted or unsubstituted C3-C12 heteroaryl group, a substituted or unsubstituted C6-C12 aryl group, a cyano group, a nitro group, or a halogen; Z4 is selected from a substituted or unsubstituted C1-C10 linear or branched alkyl group; and Ar2 is selected from a substituted or unsubstituted C6-C12 aryl group or a substituted or unsubstituted C3-C12 heteroaryl group.

[0069] Of R1, R2, R3, R4, R5, R6, R7, R8, R9, Z4, and Ar2, each of the substitution substituents is at least one independently selected from halogens.

[0070] X1 + This is one or at least two combinations selected from the following structures.

[0071] [ka]

[0072] X1 + The combinations described above are as follows: Multiple identical X1 + Structure or different X1 + The structure is linked by carbon-carbon single bonds, and the plurality is at least two, and the carbon-carbon single bonds are R 51 , R 53 , R 55 , R 58 , R 63 , R 64 , R 65 , R 67 , R 68 , R 69 , R 71 or R 72 After removing one hydrogen atom from any one of the hydrogen-containing carbon atoms, R 52 , R 54 , R 56 , R 57 , R 59 , R 60 , R 61 , R 62 , R 66 or R 70 It is formed by connecting to any one of the connection points, for example, X1 + This includes, but is not limited to, the following structures:

[0073] [ka]

[0074] However, R 54 , R' 54 They may be the same or different, R 53 , R' 53 They may be the same or they may be different.

[0075] X2 + It is one of the following structures:

[0076] [ka]

[0077] X3 + It is one of the following structures:

[0078] [ka]

[0079] however, TIFF2026534174000011.tif312 represents the base connection point.

[0080] R 51 , R 53 , R 55 , R 58 , R 63 , R 64 , R 65 , R 67 , R 68 , R 69 , R 71 , R 72 , R 81 , R 82 , R 84 , R 85 , R 88 Each of these is independently selected from substituted or unsubstituted C1-C20 linear or branched alkyl groups, -O-Z5, -O-Ar3, an amino group, substituted or unsubstituted C3-C12 heteroaryl groups, substituted or unsubstituted C6-C12 aryl groups, a cyano group, a nitro group, or a halogen; Z5 is selected from substituted or unsubstituted C1-C10 linear or branched alkyl groups; and Ar3 is selected from substituted or unsubstituted C6-C12 aryl groups or substituted or unsubstituted C3-C12 heteroaryl groups.

[0081] R 52 , R 54 , R 56 , R 57 , R 59 , R 60 , R 61 , R 62 , R66 , R 70 , R 73 , R 74 , R 75 , R 76 , R 77 , R 78 , R 79 , R 80 , R 83 , R 86 , R 87 , R 89 , R 90 , R 91 , R 92 Each is independently selected from single bonds, substituted or unsubstituted C1-C20 linear or branched alkylene groups, -O-Z6-, -O-Ar4-, -Z7-Ar5-, imino groups, substituted or unsubstituted C3-C12 heteroarylene groups, or substituted or unsubstituted C6-C12 arylene groups. 52 , R 54 , R 56 , R 57 , R 59 , R 60 , R 61 , R 62 , R 66 , R 70 , R 73 , R 74 , R 75 , R 76 , R 77 , R 78 , R 79 , R 80 , R 83 , R 86 , R 87 , R 89 , R 90 , R 91 , R 92 When it is a single bond, the heteroatom or heterocation is directly linked to the main chain segment in parentheses.

[0082] Z6 and Z7 are each independently selected from either substituted or unsubstituted C1-C10 linear or branched alkylene groups.

[0083] Ar4 and Ar5 are each independently selected from either a substituted or unsubstituted C6-C12 arylene group or a substituted or unsubstituted C3-C12 heteroarylene group.

[0084] R 51 , R 52 , R 53 , R 54 , R 55 , R 56 , R 57 , R 58 , R 59 , R 60 , R 61 , R 62 , R 63 , R 64 , R 65 , R 66 , R 67 , R 68 , R 69 , R 70 , R 71 , R 72 , R 73 , R 74 , R 75 , R 76 , R 77 , R 78 , R 79 , R 80 , R 81 , R 82 , R 83 , R 84 , R 85 , R 86 , R 87 , R 88 , R 89 , R 90 , R 91 , R 92 Of Z5, Z6, Z7, Ar3, Ar4, or Ar5, each of the substitution substituents is at least one independently selected from halogens.

[0085] Y - FSI - TFSI - BF4 - PF6 - PF2O2 - NO3 - CF3SO3 - , BOB- DFOB - It is one of the following, or a combination of at least two.

[0086] n and m are each independently selected from integers between 1 and 100,000, for example, 1, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 10000, 50000, 80000 or 100000, and specific point values ​​between the above point values. For the sake of space and simplicity, specific point values ​​included in the above range are not comprehensively illustrated in this application.

[0087] In one embodiment, the material of the polyionic liquid artificial SEI membrane includes one or at least two of the following compounds.

[0088] [ka]

[0089] However, n1, n2, n3, n4, n5, n6, and n7 are each independently selected from integers between 1 and 100,000.

[0090] The polycations, i.e., anions, in the material for the polyionic liquid artificial SEI film according to this application are all available for purchase as polycationic salts. Next, the material for the polyionic liquid artificial SEI film is prepared experimentally using the polycationic salt. The preparation method includes the following: An aqueous LiY solution is added dropwise to an aqueous polycationic salt solution and reacted to obtain a solid. The solid is washed with water and then dried to obtain the material for the polyionic liquid artificial SEI film. The mass of LiY in the aqueous LiY solution is 1 to 10%, the mass of the polycationic salt in the aqueous polycationic salt solution is 0.2 to 5%, the molar ratio of LiY to the polycationic salt is n:1, where n is the degree of polymerization of the polycationic salt, the reaction time is 5 to 10 hours, the drying temperature is 70 to 100°C, and the drying time is 24 to 72 hours. - Y is a material in the polyionic liquid artificial SEI film relating to the present application. - It is similarly limited.

[0091] This invention utilizes a polyionic liquid containing cationic groups as an artificial SEI film on the surface of an alkali metal anode. This film not only possesses excellent ionic conductivity and flexibility, but also, through the electrostatic shielding effect of the cationic groups in the polymer backbone, homogenizes the ion distribution on the surface of the alkali metal anode, thereby inducing uniform ion deposition behavior and effectively suppressing the growth of metal dendrites.

[0092] In one embodiment, the positive electrode active material of the positive electrode includes one of the following: lithium cobalt oxide, lithium manganese oxide, ternary positive electrode material, lithium-rich manganese positive electrode material, nickel-manganese positive electrode material, lithium iron phosphate, lithium manganese phosphate, or sulfur-based positive electrode material.

[0093] In one embodiment, the ternary cathode material is LiNi 0.9 Co 0.05 Mn 0.05 O2, LiLiLi 0.8 Co 0.1 Mn 0.1 O2, LiLiLi 0.6 Co0.2 Mn 0.2 O2, LiLiLi 0.5 Co 0.2 Mn 0.3 Contains O2.

[0094] In one embodiment, the nickel-manganese cathode material is LiNi 0.5 Mn 0.5 O2, LiLiLi 0.5 Mn 1.5 Contains O4 and LiNiMnCoO2.

[0095] In one embodiment, the sulfur-based cathode material includes one of the following: elemental sulfur, lithium sulfide, lithium polysulfide, sulfur / carbon composite material, lithium sulfide / carbon composite material, sulfur / polymer composite material, or lithium polysulfide / carbon composite material.

[0096] In one embodiment, the sulfur / polymer composite material includes sulfurized polyacrylonitrile, sulfurized polyvinylnitrile, and sulfurized polyimide.

[0097] In one embodiment, the separator includes a glass cellulose membrane, a cellulose membrane, and a polyolefin compound porous membrane.

[0098] In one embodiment, the polyolefin compound porous membrane includes a polypropylene separator, a polyethylene separator, and a polytetrafluoroethylene membrane.

[0099] In one embodiment, the alkali metal secondary battery further includes tab leads.

[0100] Compared to conventional technology, this invention offers the following beneficial effects.

[0101] The electrolyte according to this application has low viscosity, good flame retardancy and penetrating properties, and allows for in situ repair if the artificial SEI film on the surface of the alkali metal anode is damaged, thereby ensuring the long-term cycle stability of the battery.

[0102] (2) The alkali metal secondary battery according to the present invention, by using the above-mentioned electrolyte and polyionic liquid artificial SEI membrane, has high cycle life, Coulomb efficiency and safety, with an average Coulomb efficiency of 99.7-99.9% after 100 cycles and a capacity retention rate of 98.1-99.8%.

[0103] After reviewing and understanding the drawings and detailed descriptions, other embodiments can be understood. [Brief explanation of the drawing]

[0104] The drawings are for further understanding of the technical concept described herein, constitute part of the specification, and are used together with the embodiments of this application to interpret the technical concept described herein, and are not intended to limit the technical concept described herein.

[0105] [Figure 1] This is a schematic diagram of the internal structure of the alkali metal secondary battery relating to the present invention. [Figure 2] This is the nuclear magnetic resonance spectrum of PDDATFSI-1. [Modes for carrying out the invention]

[0106] The technical proposal of this application will be further explained below with reference to specific embodiments, accompanied by drawings. Those skilled in the art should understand that the above embodiments are merely for the purpose of understanding this application and should not be considered as specifically limiting it.

[0107] The materials related to this application, with the exception of the polyionic liquid artificial SEI membrane material, are all commercially available materials, and the origins of some of the compositions in the following examples and comparative examples are as follows.

[0108] (1) Material PDDATFSI-1 of the polyionic liquid artificial SEI membrane: The structural formula is as follows, and the preparation steps include the following. [ka]

[0109] 2 g of LiTFSI salt was completely dissolved in 50 mL of deionized water to prepare the solution. Then, 5.63 g of polydimethyldiallylammonium chloride (PDDACl) solution (20 wt% aqueous solution, molecular weight 200,000, purchased from Adamas) and 200 mL of deionized water were mixed and stirred, and the LiTFSI aqueous solution was added dropwise during the stirring process to allow the reaction to proceed. At this time, a white, cotton-like solid gradually precipitated in the solution, and the reaction time was 6 hours. After stirring stopped, the white solid quickly settled in the container, and after standing for 10 minutes, the liquid was discarded, leaving the white solid, which was washed with deionized water and repeated 5-6 times. Washing was considered complete when no obvious precipitation or sedimentation occurred after adding AgNO3 aqueous solution to the washed liquid. Finally, the white solid was collected using a suction filter and dried in an 80°C oven for 48 hours to obtain the final dried white solid, which was then ground into a powder using a mortar and pestle to obtain PDDATFSI-1.

[0110] (2) Material PDDAFSI for polyionic liquid artificial SEI membrane: The structural formula is as follows. [ka] The preparation step differs from that of PDDATFSI-1 in that an equal amount of LiTFSI aqueous solution is replaced with an equal amount of LiFSI aqueous solution of the same proportion; all other raw materials, process steps, and parameters are the same as those used in the preparation of PDDATFSI-1.

[0111] (3) Material PDDATFSI-2 for polyionic liquid artificial SEI membrane: The structural formula is as follows. [ka] The preparation step differs from PDDATFSI-1 described above only in that an equal amount of polydimethyldiallylammonium chloride (PDDACl) solution (20 wt% aqueous solution, molecular weight 200,000, purchased from Adamas) is replaced with polydimethyldiallylammonium chloride (PDDACl) solution (20 wt% aqueous solution, molecular weight 500,000, purchased from Adamas). All other raw materials, process steps, and parameters are the same as those for the preparation of PDDATFSI-1.

[0112] (4) Material PDDATFSI-3 for polyionic liquid artificial SEI membrane: The structural formula is as follows. [ka] The preparation step differs from PDDATFSI-1 described above only in that an equal amount of polydimethyldiallylammonium chloride (PDDACl) solution (20 wt% aqueous solution, molecular weight 200,000, purchased from Adamas) is replaced with polydimethyldiallylammonium chloride (PDDACl) solution (20 wt% aqueous solution, molecular weight 10,000, purchased from Adamas). All other raw materials, process steps, and parameters are the same as those used for the preparation of PDDATFSI-1.

[0113] (5) N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide salt: Purchased from Shanghai Cheng Jie Chemical Co. LTD.

[0114] (6) N-methyl-N-butylpiperidinium bis(fluorosulfonyl)imide salt: Purchased from Shanghai Cheng Jie Chemical Co. LTD.

[0115] (7) N-methyl-N-butylpyrrolidinium bis(fluorosulfonyl)imide salt: Purchased from Shanghai Cheng Jie Chemical Co. LTD.

[0116] (8) N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide salt: Purchased from Shanghai Cheng Jie Chemical Co. LTD.

[0117] (9) Polyethylene oxide: Purchased from Adamas.

[0118] Example 1 An electrolyte, wherein the method for preparing the electrolyte comprises dissolving LiTFSI in 4 g of N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide salt, 3 g of cyclopentyl methyl ether, and 3 g of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether in a glove box under the protection of an inert gas, stirring until the lithium salt is completely dissolved, and obtaining a clear electrolyte, wherein the concentration of LiTFSI in the electrolyte is 1 mol / L.

[0119] Preparation of a lithium metal anode coated with a polyionic liquid artificial SEI film on its outer surface: Under dry conditions (H2O < 1 ppm), PDDATFSI-1 was dissolved in NMP (N-methylpyrrolidone) solvent, and then uniformly coated onto the surface of a lithium metal anode. The NMP solvent was removed by vacuum drying at 80°C to obtain a lithium metal anode coated with a polyionic liquid artificial SEI film on its outer surface. The thickness of the polyionic liquid artificial SEI film was 20 nm.

[0120] Manufacturing of positive electrode pieces: Under dry conditions, 5% by mass of polyvinylidene fluoride was thoroughly dissolved in NMP, 5% by mass of conductive carbon black and 90% of lithium iron phosphate were added to the solution and mixed uniformly, the prepared slurry was uniformly applied to aluminum foil, dried, roll-rolled, cut out to obtain positive electrode pieces.

[0121] The lithium metal secondary battery, the internal structure of which is shown in Figure 1. The internal structure of the alkali metal secondary battery includes a positive electrode current collector and a negative electrode current collector, a positive electrode, a separator, a lithium metal negative electrode coated with a polyionic liquid artificial SEI film, and an electrolyte. The manufacturing of the lithium metal secondary battery includes assembling a lithium metal secondary battery cell together with a polypropylene separator using the lithium metal negative electrode piece and positive electrode piece, which have the prepared outer surface coated with a polyionic liquid artificial SEI film, using metallic aluminum and metallic nickel as the positive electrode tab lead and negative electrode tab lead, respectively, packaging the outside with an aluminum plastic film, and finally injecting the prepared electrolyte and completing the sealing to obtain the lithium metal secondary battery.

[0122] Example 2 The electrolyte is the same as the electrolyte in Example 1.

[0123] This lithium metal secondary battery differs from Example 1 only in that the material of the polyionic liquid artificial SEI membrane is PDDAFSI; all other compositions are the same as in Example 1.

[0124] Example 3 The electrolyte is the same as the electrolyte in Example 1.

[0125] This lithium metal secondary battery differs from Example 1 only in that the material of the polyionic liquid artificial SEI membrane is PDDATFSI-2; all other compositions are the same as in Example 1.

[0126] Example 4 The electrolyte is the same as the electrolyte in Example 1.

[0127] This lithium metal secondary battery differs from Example 1 only in that the material of the polyionic liquid artificial SEI membrane is PDDATFSI-3; all other compositions are the same as in Example 1.

[0128] Example 5 The electrolyte is composed of LiTFSI, 3 g of N-methyl-N-butylpiperidinium bis(fluorosulfonyl)imide salt, 2 g of cyclohexyl methyl ether, and 5 g of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and differs from Example 1 only in that the concentration of LiTFSI in the electrolyte is 1 mol / L; the other preparation processes are the same as in Example 1.

[0129] This lithium metal secondary battery differs from Example 1 only in that the electrolyte of the lithium metal secondary battery is the electrolyte according to this embodiment; all other compositions are the same as in Example 1.

[0130] Example 6 The electrolyte is composed of LiDFOB, 7 g of N-methyl-N-butylpyrrolidinium bis(fluorosulfonyl)imide salt, 2 g of cyclohexyl methyl ether, and 1 g of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and differs from Example 1 only in that the concentration of LiDFOB in the electrolyte is 0.5 mol / L; the other preparation processes are the same as in Example 1.

[0131] This lithium metal secondary battery differs from Example 1 only in that the electrolyte of the lithium metal secondary battery is the electrolyte according to this embodiment; all other compositions are the same as in Example 1.

[0132] Example 7 The electrolyte is composed of LiTFSI, 6 g of N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide salt, 2 g of cyclobutyl methyl ether, and 2 g of 1,2-difluorobenzene, and differs from Example 1 only in that the concentration of LiTFSI in the electrolyte is 2 mol / L; the other preparation processes are the same as in Example 1.

[0133] This lithium metal secondary battery differs from Example 1 only in that the electrolyte of the lithium metal secondary battery is the electrolyte according to this embodiment; all other compositions are the same as in Example 1.

[0134] Example 8

[0135] The electrolyte is the same as the electrolyte in Example 1.

[0136] This lithium metal secondary battery differs from Example 1 only in that a polyionic liquid artificial SEI film is not coated on the outer surface of the lithium metal negative electrode.

[0137] Comparative Example 1 The electrolyte differs from Example 1 only in that its composition is LiTFSI and 10 g of N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide salt, and the concentration of LiTFSI in the electrolyte is 1 mol / L; the other preparation processes are the same as in Example 1.

[0138] This lithium metal secondary battery differs from Example 1 only in that the electrolyte of the lithium metal secondary battery is the electrolyte according to this comparative example; all other compositions are the same as in Example 1.

[0139] Comparative Example 2 The electrolyte is composed of LiTFSI, 7 g of N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide salt, and 3 g of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and differs from Example 1 only in that the concentration of LiTFSI in the electrolyte is 1 mol / L; the other preparation processes are the same as in Example 1.

[0140] This lithium metal secondary battery differs from Example 1 only in that the electrolyte of the lithium metal secondary battery is the electrolyte according to this comparative example; all other compositions are the same as in Example 1.

[0141] Comparative Example 3 The electrolyte is composed of LiTFSI, 3 g of ethylene carbonate, and 7 g of dimethyl carbonate, and differs from Example 1 only in that the concentration of LiTFSI in the electrolyte is 1 mol / L; the other preparation processes are the same as in Example 1.

[0142] This lithium metal secondary battery differs from Example 1 only in that the electrolyte of the lithium metal secondary battery is the electrolyte according to this comparative example; all other compositions are the same as in Example 1.

[0143] Comparative Example 4 This electrolyte differs from Example 1 only in that 3 g of cyclopentyl methyl ether is replaced with 3 g of ethylene glycol dimethyl ether; the other preparation processes are the same as in Example 1.

[0144] This lithium metal secondary battery differs from Example 1 only in that the electrolyte of the lithium metal secondary battery is the electrolyte according to this comparative example; all other compositions are the same as in Example 1.

[0145] Comparative Example 5 The electrolyte is the same as the electrolyte in Example 1.

[0146] This lithium metal secondary battery differs from Example 1 only in that the material of the polyionic liquid artificial SEI membrane is polyethylene oxide (PEO), while all other compositions are the same as in Example 1.

[0147] Performance measurement: (1) Nuclear Magnetic Resonance Spectrum Measurement: PDDATFSI-1 was measured using a nuclear magnetic resonance spectrometer (Varian-400 MHz). The measurement results are shown in the nuclear magnetic resonance spectrum of PDDATFSI-1 in Figure 2. As can be seen from Figure 2, the four peaks a, b, c, and d each correspond to the hydrogen atoms at the relevant positions marked in the chemical structure, and by comparing the size and position of the peaks, it is possible to correlate them well with the target structure. This has revealed that the substance matches the target structure and is free of other impurities. (2) Electrochemical performance measurements were performed on the lithium metal secondary batteries in Examples 1-8 and Comparative Examples 1-5, with measurement voltages ranging from 2.5 to 4.0 V and a cycle rate of 0.2 C. The measurement results are shown in Table 1. [Table 1]

[0148] As can be seen from the measurement data of Examples 1 to 7 in Table 1, the lithium metal secondary battery according to the present invention exhibits high Coulomb efficiency and high capacity retention after 100 cycles. As can be seen from the comparison of Comparative Examples 1, 2 and 1, by adding a weakly polar solvent and an inert diluent to the ionic liquid, the viscosity of the electrolyte can be effectively reduced, further improving the discharge ratio capacity of the battery.

[0149] As can be seen from the comparison between Comparative Example 3 and Example 1, the carbonate-based electrolyte and the lithium metal anode undergo serious side reactions, resulting in a decrease in the average Coulomb efficiency and capacity retention rate of the battery. It has been further found that, when the battery structure is similar, using the electrolyte according to the present invention can effectively reduce side reactions on the surface of the lithium metal anode, thereby improving the performance of the battery.

[0150] As can be seen from the comparison between Example 1 and Comparative Example 4, compared to adding a highly polar linear ether solvent to the electrolyte, an electrolyte prepared using a weakly polar, large-volume cyclic hydrocarbon-containing ether solvent can effectively improve the Coulomb efficiency and capacity retention rate of the battery. The weakly polar ether solvent according to the present invention has been found to effectively reduce interfacial side reactions at the electrode and improve interfacial stability.

[0151] As can be seen from the comparison of Examples 1, 8 and Comparative Example 5, batteries using lithium metal anodes without a polyionic liquid artificial SEI film coating on the surface of the lithium metal anode, and lithium metal anodes coated with PEO, both showed lower initial Coulomb efficiency and capacity retention. This indicates that lithium metal anodes coated with a polyionic liquid artificial SEI film can effectively suppress interfacial reactions between the electrolyte and the electrode, and because the polyionic liquid artificial SEI film has high ionic conductivity, it can ensure high capacity, high Coulomb efficiency, and excellent cycle stability of the battery.

[0152] While the present application has described the detailed process steps of the present application with respect to the above-described embodiments, the applicant declares that the present application is not limited to the above-described detailed process steps, that is, it does not mean that the present application must be implemented in accordance with the above-described detailed process steps. Those skilled in the art should understand that any improvements to the present application, equivalent substitutions and additions of auxiliary components to the raw materials used in the present application, and selection of specific forms are all included within the scope of protection and disclosure of the present application.

Claims

1. An electrolyte comprising a combination of an alkali metal salt and a solvent, The solvent comprises a combination of an ionic liquid, a weakly polar solvent, and an inert diluent. The weakly polar solvent is selected from any one or at least two combinations of the following compounds having the structure described below. 【Chemistry 1】 (However, R １１ , R １３ , R １５ , R １７ , R １９ , R ２１ Each of these is independently selected from single bonds, substituted or unsubstituted C1-C10 linear or branched alkylene groups, and substituted or unsubstituted C3-C10 cycloalkylene groups. R １２ , R １４ , R １６ , R １８ , R ２０ , R ２２ are each independently any one selected from a substituted or unsubstituted C1-C10 linear or branched alkyl group, and a substituted or unsubstituted C3-C10 cycloalkyl group, R １１ , R １２ , R １３ , R １４ , R １５ , R １６ , R １７ , R １８ , R １９ , R ２０ , R ２１ , R ２２ Of these, the substituted substituents are, independently, a deuterium atom, a halogen, a nitro group, an amino group, a carboxyl group, and Z. １ -COO-, C1-C10 linear or branched alkyl group, C2-C10 alkenyl group, -O-Z ２ , at least one selected from C6-C30 aryl groups and C3-C30 heteroaryl groups, However, Z １ and Z ２ Each of these is independently selected from one of the linear or branched alkyl groups of C1 to C10. Electrolyte.

2. The weakly polar solvent includes one or at least two of the following: cyclopropyl methyl ether, cyclobutyl ethyl ether, cyclopentyl methyl ether, cyclopentyl ethyl ether, cyclopentyl propyl ether, cyclohexyl methyl ether, cyclohexyl ethyl ether, cyclopentyl trifluoromethyl ether, cyclohexyl trifluoromethyl ether, cycloheptyl ethyl ether, cyclooctyl propyl ether, or cyclooctyl butyl ether. The electrolyte according to claim 1.

3. The mass percentage of the weakly polar solvent in the aforementioned solvent is 10 to 85%, and more preferably 20 to 60%. The electrolyte according to claim 1 or 2.

4. The alkali metal salt includes one or at least two of the following: lithium salt, sodium salt, or potassium salt. The electrolyte according to any one of claims 1 to 3.

5. The lithium salt comprises one or at least two of the following: bis(fluorosulfonyl)imide lithium, bis(trifluoromethanesulfonyl)imide lithium, hexafluorophosphate lithium, lithium perchlorate, lithium tetrafluoroborate, lithium bisoxalate borate, hexafluoroarsenate lithium, lithium difluorooxalate borate, lithium difluorophosphate, or 4,5-dicyano-2-trifluoromethylimidazole lithium. Preferably, the sodium salt includes one or at least two of the following: sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium bisoxalate borate, sodium hexafluoroarsenate, sodium difluorooxalate borate, sodium difluorophosphate, or sodium 4,5-dicyano-2-trifluoromethylimidazole. Preferably, the potassium salt includes one or at least two of the following: potassium bis(fluorosulfonyl)imide, potassium bis(trifluoromethanesulfonyl)imide, potassium hexafluorophosphate, potassium perchlorate, potassium tetrafluoroborate, potassium bisoxalate borate, potassium hexafluoroarsenate, potassium difluorooxalate borate, potassium difluorophosphate, or potassium 4,5-dicyano-2-trifluoromethylimidazole. Preferably, the concentration of the alkali metal salt in the electrolyte is 0.1 to 6 mol / L, and more preferably 0.5 to 2 mol / L. The electrolyte according to claim 4.

6. The structure of the aforementioned ionic liquid is A ＋ [B] － And, However, A ＋ This is one or at least two combinations selected from the following structures: 【Chemistry 2】 (However, R ３１ , R ３２ , R ３３ , R ３４ , R ３５ , R ３６ , R ３７ , R ３８ , R ３９ , R ４０ , R ４１ , R ４２ , R ４３ , R ４４ , R ４５ , R ４６ , R ４７ , R ４８ , R ４９ , R ５０ Each is independently a substituted or unsubstituted C1-C20 linear or branched alkyl group, -R'-O-Z ３ , -O-Ar １ , one selected from an amino group, a substituted or unsubstituted C6-C12 aryl group, a substituted or unsubstituted C3-C12 heteroaryl group, a cyano group, a nitro group, or a halogen, Z ３ is one selected from substituted or unsubstituted C1-C10 linear or branched alkyl groups, R' is one of the single-bonded, substituted, or unsubstituted C1-C10 linear or branched alkylene groups. Ar １ This is one of the following selected from substituted or unsubstituted C6-C12 aryl groups and substituted or unsubstituted C3-C12 heteroaryl groups. R ３１ , R ３２ , R ３３ , R ３４ , R ３５ , R ３６ , R ３７ , R ３８ , R ３９ , R ４０ , R ４１ , R ４２ , R ４３ , R ４４ , R ４５ , R ４６ , R ４７ , R ４８ , R ４９ , R ５０ Z ３ Ar １ Of R', each of the substitution substituents is at least one independently selected from halogens. [B] － is FSI － , TFSI － , BF ４ － , PF ６ － , PF ２ O ２ － , NO ３ － , CF ３ SO ３ － , BOB － or DFOB － is any one selected from the above or a combination of at least two thereof.) The electrolyte according to any one of claims 1 to 5.

7. A ＋ This includes one or at least two combinations of the following cations: 【Transformation 3】 Preferably, the mass percentage of the ionic liquid in the solvent is 10 to 85%, and more preferably 30 to 70%. The electrolyte according to claim 6.

8. The inert diluent comprises one or at least two of the following: halogenated ethers, halogenated benzenes, or halogenated alkanes. The electrolyte according to any one of claims 1 to 7.

9. The halogenated ether comprises one or at least two of the following: 1,1,1,3,3,3-hexafluoroisopropyl methyl ether, 2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 2,2,2-trifluoroethyl methyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, methyl nonafluorobutyl ether, or ethyl nonafluorobutyl ether. Preferably, the halogenated benzene includes fluorobenzene and / or 1,2-difluorobenzene. Preferably, the halogenated alkane includes one or at least two of the following: dichloromethane, dichloroethane, dichloropropane, dichlorobutane, chloroform, trichloropropane, chlorodifluoromethane, dichlorofluoromethane, or difluoromethane. Preferably, the mass percentage of the inert diluent in the solvent is 5 to 60%, and more preferably 10 to 50%. The electrolyte according to claim 8.

10. A negative electrode, a positive electrode, an electrolyte according to any one of claims 1 to 9, and a separator are included. Alkaline metal rechargeable battery.

11. The negative electrode includes an alkali metal negative electrode and a negative electrode current collector. Preferably, the alkali metal anode comprises one of lithium, sodium, or potassium. Preferably, the negative electrode current collector includes one of the following: copper foil, nickel foil, or nickel-plated steel strip. The alkali metal secondary battery according to claim 10.

12. The outer surface of the alkali metal negative electrode is coated with a single layer of polyionic liquid artificial SEI film. Preferably, the thickness of the polyionic liquid artificial SEI film is 2 to 2000 nm. The alkali metal secondary battery according to claim 11.

13. The material of the polyionic liquid artificial SEI membrane has a structure represented by formula I, formula II, or formula III. 【Chemistry 4】 (provided that R １ , R ２ , R ３ , R ４ , R ５ , R ６ , R ７ , R ８ , R ９ are each independently any one selected from a hydrogen atom, a substituted or unsubstituted C1-C10 linear or branched alkyl group, -O-Z ４ , -O-Ar ２ , an amino group, a substituted or unsubstituted C3-C12 heteroaryl group, a substituted or unsubstituted C6-C12 aryl group, a cyano group, a nitro group, or a halogen, Z ４ is one selected from substituted or unsubstituted C1-C10 linear or branched alkyl groups, Ar ２ This is one of the following selected from substituted or unsubstituted C6-C12 aryl groups and substituted or unsubstituted C3-C12 heteroaryl groups. R １ , R ２ , R ３ , R ４ , R ５ , R ６ , R ７ , R ８ , R ９ Z ４ Ar ２ Of these, each of the substitution substituents is at least one independently selected from halogens. X １ ＋ This is one or at least two combinations selected from the following structures: 【Transformation 5】 X ２ ＋ It is one of the following structures, 【Transformation 6】 X ３ ＋ It is one of the following structures, 【Transformation 7】 however, 【change】 This represents the connection point of the base, R ５１ , R ５３ , R ５５ , R ５８ , R ６３ , R ６４ , R ６５ , R ６７ , R ６８ , R ６９ , R ７１ , R ７２ , R ８１ , R ８２ , R ８４ , R ８５ , R ８８ Each is independently a substituted or unsubstituted C1-C20 linear or branched alkyl group, -O-Z ５ , -O-Ar ３ , one selected from an amino group, a substituted or unsubstituted C3-C12 heteroaryl group, a substituted or unsubstituted C6-C12 aryl group, a cyano group, a nitro group, or a halogen, Z ５ is one selected from substituted or unsubstituted C1-C10 linear or branched alkyl groups, Ar ３ This is one of the following selected from substituted or unsubstituted C6-C12 aryl groups and substituted or unsubstituted C3-C12 heteroaryl groups. R ５２ , R ５４ , R ５６ , R ５７ , R ５９ , R ６０ , R ６１ , R ６２ , R ６６ , R ７０ , R ７３ , R ７４ , R ７５ , R ７６ , R ７７ , R ７８ , R ７９ , R ８０ , R ８３ , R ８６ , R ８７ , R ８９ , R ９０ , R ９１ , R ９２ Each of these is independently a single bond, a substituted or unsubstituted C1-C20 linear or branched alkylene group, and -O-Z ６ -, -O-Ar ４ -, -Z ７ -Ar ５ - is one selected from an imino group, a substituted or unsubstituted C3-C12 heteroarylene group, or a substituted or unsubstituted C6-C12 arylene group. Z ６ Z ７ Each is independently selected from substituted or unsubstituted C1-C10 linear or branched alkylene groups. Ar ４ Ar ５ Each of these is independently selected from either a substituted or unsubstituted C6-C12 arylene group or a substituted or unsubstituted C3-C12 heteroarylene group. R ５１ , R ５２ , R ５３ , R ５４ , R ５５ , R ５６ , R ５７ , R ５８ , R ５９ , R ６０ , R ６１ , R ６２ , R ６３ , R ６４ , R ６５ , R ６６ , R ６７ , R ６８ , R ６９ , R ７０ , R ７１ , R ７２ , R ７３ , R ７４ , R ７５ , R ７６ , R ７７ , R ７８ , R ７９ , R ８０ , R ８１ , R ８２ , R ８３ , R ８４ , R ８５ , R ８６ , R ８７ , R ８８ , R ８９ , R ９０ , R ９１ , R ９２ Z ５ Z ６ Z ７ Ar ３ Ar ４ or Ar ５ Of these, each of the substitution substituents is at least one independently selected from halogens. Y － FSI － TFSI － BF ４ － , PF ６ － , PF ２ O ２ － NO ３ － CF ３ SO ３ － , BOB － DFOB － It is one or at least two combinations selected from the following: n and m are each independently selected from integers between 1 and 100,000. The alkali metal secondary battery according to claim 12.

14. The material of the polyionic liquid artificial SEI membrane comprises one or at least two of the following compounds: 【Transformation 8】 (However, n １ , n ２ , n ３ , n ４ , n ５ , n ６ , n ７ (Each of these is independently selected from integers between 1 and 100,000.) The alkali metal secondary battery according to claim 12 or 13.

15. The positive electrode active material of the positive electrode includes one of the following: lithium cobalt oxide, lithium manganese oxide, ternary positive electrode material, lithium-rich manganese positive electrode material, nickel-manganese positive electrode material, lithium iron phosphate, lithium manganese phosphate, or sulfur-based positive electrode material. Preferably, the sulfur-based cathode material includes one of the following: elemental sulfur, lithium sulfide, lithium polysulfide, sulfur / carbon composite material, lithium sulfide / carbon composite material, sulfur / polymer composite material, or lithium polysulfide / carbon composite material. Preferably, the separator includes a glass cellulose membrane, a cellulose membrane, and a polyolefin compound porous membrane. Preferably, the alkali metal secondary battery further includes a tab lead. The alkali metal secondary battery according to any one of claims 10 to 14.

Images