Electrolyte, lithium metal battery and electric device

Abstract

The invention provides an electrolyte, a lithium metal battery and a power utilization device, the electrolyte comprises a first solvent, the first solvent comprises anions and cations, the cations comprise at least one of structures shown as a formula I, a formula II, a formula III and a formula IV, R1, R6, R11 and R16 respectively and independently comprise C1-3 alkylene or C1-3 fluoroalkylene, and R1, R6, R11 and R16 are independently selected from the group consisting of C1-6 alkyl, C1-6 fluoroalkyl and C1-6 fluoroalkyl. R1, R2, R7, R12 and R22 each independently comprise a C1-5 alkyl group or a C1-5 fluoroalkyl group, R3, R4, R8, R9, R13, R14, R18 and R19 each independently comprise a C1-3 alkylene group, R5, R10, R15, R20, R21 and R22 each independently comprise a C1-3 alkyl group, R1 and R2 at least comprise one fluorine atom, R6 and R7 at least comprise one fluorine atom, R11 and R12 at least comprise one fluorine atom, R16 and R17 at least comprise one fluorine atom, and R1, R2, R7, R12 and R22 at least comprise one fluorine atom. And the anions comprise at least one of tetrafluoroborate, hexafluorophosphate, hexafluoroarsenate, trifluoromethanesulfonate, bis (trifluoromethylsulfonyl) imide, bis (fluorosulfonyl) imide, difluorophosphate, bis (oxalato) borate, difluoro (oxalato) borate, difluoro (oxalato) borate, difluoro (oxalato) phosphate and tetrafluoro (oxalato) phosphate.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to an electrolyte, a lithium metal battery and an electrical device. Background Art

[0002] The energy density of the battery materials used in commercial lithium-ion batteries has basically reached the theoretical limit, and new electrode materials are urgently needed to improve the energy density. Among them, the metallic lithium negative electrode has a theoretical energy density of 3860mAh / g and a low electrode potential (-3.04V), which has attracted extensive attention from researchers and has achieved a series of application results, such as lithium metal batteries.

[0003] However, the thermodynamic instability of the lithium metal negative electrode and the electrolyte will cause them to react spontaneously. The volume change of lithium during the deposition / stripping process will destroy the SEI film layer. The rupture and repair of the SEI film layer will continue to consume active lithium and electrolyte. These problems will cause the battery's cycle capacity to decay rapidly. At the same time, in addition, when the lithium dendrites grow to a certain extent, they will pierce the diaphragm and cause the battery to short-circuit. The large amount of heat released at the moment of short-circuit may cause combustion or even explosion. Therefore, the safety of lithium metal batteries also needs to be further improved. Summary of the invention

[0004] The present application is made in view of the above-mentioned problems, and its purpose is to provide an electrolyte, a lithium metal battery and an electrical device for increasing the number of room temperature cycles of the lithium metal battery and improving the cycle performance and safety performance of the lithium metal battery.

[0005] The first aspect of the present application provides an electrolyte solution, comprising a first solvent, wherein the first solvent comprises anions and cations, wherein the cations comprise at least one of the structures shown in Formula I, Formula II, Formula III, and Formula IV,

[0006]

[0007] Among them, R 1 , R 6 , R 11 , R 16 Each independently contains C 1-3 Alkylene or C 1-3 Fluorinated alkylene, R 2 , R 7 , R 12 , R 22 Each independently contains C 1-5 Alkyl or C 1-5 Fluorinated alkyl, R 3 , R 4 , R 8 , R 9 , R 13 , R14 , R 18 , R 19 Each independently contains C 1-3 Alkylene, R 5 , R 10 , R 15 , R 20 , R 21 , R 22 Each independently contains C 1-3 Alkyl, R 1 and R 2 Contains at least one fluorine atom, R 6 and R 7 Contains at least one fluorine atom, R 11 and R 12 Contains at least one fluorine atom, R 16 and R 17 contains at least one fluorine atom,

[0008] The anion comprises at least one of tetrafluoroborate, hexafluorophosphate, hexafluoroarsenate, trifluoromethanesulfonate, bistrifluoromethanesulfonyl imide, bisfluorosulfonyl imide, difluorophosphate, dioxalatoborate, difluorooxalatoborate, difluorodioxalatoborate, difluorodioxalatophosphate, and tetrafluorooxalatophosphate.

[0009] First, the first solvent in the electrolyte is an ionic liquid, which has properties such as non-volatility and flame retardancy. Adding the first solvent ionic liquid to the electrolyte can improve the flame retardancy of the electrolyte and the safety of the lithium metal battery. Secondly, the two ends of the cationic structure of the first solvent ionic liquid are functionally modified. On the one hand, one end of the cation of the first solvent ionic liquid contains an ether functional group, which can improve the ionic conductivity of the ionic liquid, reduce the viscosity of the electrolyte, increase the ionic conductivity of the electrolyte, increase the migration speed of lithium ions, and improve the kinetic performance of the system. At the same time, the fluorine atom substitution of the ether functional group also reduces the HOMO (highest occupied molecular orbital) energy level, so that the antioxidant property of the ionic liquid is improved, and the antioxidant property of the electrolyte is improved. In addition, due to the high bond energy of the CF bond, the stability of the cation is improved, and the ionic liquid containing the ether functional group has excellent compatibility with the lithium metal negative electrode, thereby improving the compatibility of the electrolyte with the lithium metal negative electrode, and thus improving the cycle stability of the battery; on the other hand, the other end of the cation of the first solvent ionic liquid contains an unsaturated ketone structure, which has good film-forming properties and can form a high-toughness SEI film layer mainly composed of organic components on the negative electrode surface of the lithium metal battery, thereby reducing the possibility of SEI film breakage during the battery cycle, and thus improving the cycle stability of the battery.

[0010] In summary, by using the above-mentioned electrolyte, on the basis of ensuring the safety of the lithium metal battery, the cycle stability of the battery is further improved, and the long life cycle of the lithium metal battery is achieved.

[0011] In any embodiment, the R 1 and R 2 The number of carbon atoms is not 1 at the same time, the R 6 and R 7 The number of carbon atoms is not 1 at the same time, the R 11 and R 12 The number of carbon atoms is not 1 at the same time, the R 16 and R 17 The number of carbon atoms is not always 1.

[0012] The number of carbon atoms in the groups at both ends of the oxygen atom in the fluoroether structure is different from 1, which can improve the stability of the fluoroether structure, so that the fluoroether structure can achieve the purpose of improving the conductivity and oxidation resistance of the first solvent ionic liquid and the electrolyte, improve the cycle performance of the battery, and extend the cycle life of the battery.

[0013] In any embodiment, the R 1 , R 6 , R 11 , R 16 Each independently comprises the following groups,

[0014]

[0015] Wherein, * represents the R 1 , R 6 , R 11 , R 16 The connection site with the nitrogen atom in the structure shown in Formula I, Formula II, Formula III, and Formula IV, Represents the R 1 , R 6 , R 11 , R 16 The connection site with the oxygen atom in the structure shown in Formula I, Formula II, Formula III, and Formula IV.

[0016] R 1 , R 6 , R 11 , R 16The carbon atom substituted with fluorine atom is not directly connected to the oxygen atom, which can weaken the interaction between fluorine atom and oxygen atom, and is beneficial to the interaction between oxygen atom of fluoroether structure and lithium ion, so that lithium ion and the first solvent ionic liquid form a more stable solvation structure, which is beneficial to the unsaturated ketone structure in the ionic liquid to reach the negative electrode surface with the solvation structure to carry out film-forming reaction, generate a high-toughness SEI film layer, improve the cycle stability of the battery, and improve the cycle performance of the battery.

[0017] In any embodiment, the R 2 , R 7 , R 12 , R 22 Each independently comprises the following groups,

[0018]

[0019] in, Representative 2 , R 7 , R 12 , R 22 The connection site with the oxygen atom in the structure shown in Formula I, Formula II, Formula III, and Formula IV.

[0020] R 2 , R 7 , R 12 , R 22 The carbon atoms substituted with fluorine atoms are not directly connected to the oxygen atoms, which can weaken the interaction between the fluorine atoms and the oxygen atoms, and is beneficial to the interaction between the oxygen atoms of the fluoroether structure and the lithium ions, so that the lithium ions and the first solvent ionic liquid form a more stable solvation structure, which is beneficial for the unsaturated ketone structure in the ionic liquid to reach the negative electrode surface along with the solvation structure to undergo a film-forming reaction, thereby generating a highly tough SEI film layer, thereby improving the cycle stability of the battery and improving the cycle performance of the battery.

[0021] In any embodiment, the cation comprises at least one of the following structures,

[0022]

[0023]

[0024] In any embodiment, the electrolyte further includes a second solvent, and the volume ratio of the first solvent to the second solvent is 0.1-1, preferably 0.5-0.85.

[0025] The electrolyte contains a second solvent, which can further improve the conductivity of the electrolyte. At the same time, the solvation structure formed by the second solvent and lithium ions helps the anions in the lithium salt to react on the surface of the negative electrode to form a high-density SEI film layer composed mainly of inorganic components. The high-density SEI film layer composed mainly of inorganic components and the high-toughness SEI film layer composed mainly of organic components formed by the cationic structure of the first solvent ionic liquid work together to improve the stability of the lithium metal negative electrode and the cycle performance of the battery.

[0026] In any embodiment, the electrolyte further includes a lithium salt, and the molar concentration of the lithium salt in the electrolyte is 0.5 mol / L-4 mol / L, and can be optionally 0.8 mol / L-2.2 mol / L.

[0027] The appropriate molar concentration of lithium salt makes the electrolyte have excellent electrical conductivity, while ensuring that a sufficient number of lithium salt anions participate in the formation of a high-density SEI film layer mainly composed of inorganic components, thereby comprehensively improving the cycle performance of the battery.

[0028] In any embodiment, the second solvent comprises at least one of fluorinated aromatic compounds, aromatic compounds, ester compounds, ether compounds, sulfone compounds, and nitrile compounds, and can be selected from ethylene carbonate, ethyl methyl carbonate, fluoroethylene carbonate, difluoroethylene carbonate, diethyl carbonate, methyl trifluoroethyl carbonate, dimethyl carbonate, benzene, toluene, p-xylene, m-xylene, o-xylene, fluorobenzene, p-difluorobenzene, m-difluorobenzene, o-difluorobenzene, trifluorotoluene, trifluoromethoxybenzene, decafluoropentane, perfluoropentanone, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,2-bis(1,1,2 ,2-tetrafluoroethoxy)ethane, bis(2,2,2-trifluoroethyl) ether, 1,1,2,3,3,3-hexafluoropropyl ethyl ether, 1,2,2-tetrafluoroethyl ether, ethyl trifluoromethyl ether, difluoromethyl-2,2,3,3,3-pentafluoropropyl ether, heptafluoropropyl-1,2,2,2-tetrafluoroethyl ether, difluoromethyl-2,2,3,3-tetrafluoropropyl ether, perfluoroisopropyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, ethyl-1,1,2,2-tetrafluoroethyl ether, ethyl-2,2,2-tetrafluoroethyl ether, bis(1,1,2,2-tetrafluoroethyl) ether.

[0029] In any embodiment, the lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium trifluoroacetate, lithium tetraphenylborate, lithium trifluoromethylsulfonate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide, and lithium hexafluorophosphate may be selected.

[0030] A second aspect of the present application provides a lithium metal battery, comprising the electrolyte described in the first aspect.

[0031] The third aspect of the present application provides an electrical device, comprising the lithium metal battery described in the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic diagram of lithium metal according to one embodiment of the present application;

[0033] Figure 2 yes Figure 1 An exploded view of lithium metal according to one embodiment of the present application is shown;

[0034] Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application;

[0035] Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0036] Figure 5 yes Figure 4 An exploded view of a battery pack according to an embodiment of the present application is shown;

[0037] Figure 6 It is a schematic diagram of an electrical device using a lithium metal battery as a power source according to one embodiment of the present application.

[0038] Reference numerals:

[0039] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 lithium metal battery; 51 shell; 52 electrode assembly; 53 cover plate. DETAILED DESCRIPTION

[0040] Hereinafter, the embodiments of the electrolyte, lithium metal battery and electrical device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0041] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0042] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0043] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0044] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0045] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0046] The current non-aqueous electrolyte of lithium metal batteries is highly flammable, which poses a safety hazard to lithium metal batteries. Ionic liquids have the advantages of being non-volatile and non-flammable, which has gradually attracted attention. However, traditional ionic liquids have high viscosity and high ionic conductivity, which will affect the transport performance of lithium ions, causing uneven deposition of lithium ions on the electrode surface, resulting in the formation of lithium dendrites, and easily forming "dead lithium", which is not conducive to the battery's cycle performance and safety performance. In addition, during the battery cycle, the volume change of lithium will destroy the SEI film layer, and the exposed lithium metal will continue to react with the electrolyte, which will also have a negative impact on the battery's cycle performance.

[0047] [Electrolyte]

[0048] Based on this, the present application provides an electrolyte, including a first solvent, wherein the first solvent includes anions and cations, and the cations include at least one of the structures shown in Formula I, Formula II, Formula III, and Formula IV.

[0049]

[0050] Among them, R 1 , R 6 , R 11 , R 16 Each independently contains C 1-3 Alkylene or C 1-3 Fluorinated alkylene, R 2 , R 7 , R 12 , R 22 Each independently contains C 1-5 Alkyl or C 1-5 Fluorinated alkyl, R 3 , R 4 , R 8 , R 9 , R 13 , R 14 , R 18 , R 19 Each independently contains C 1-3 Alkylene, R 5 , R 10 , R 15 , R 20 , R 21 , R 22 Each independently contains C 1-3 Alkyl, R 1 and R 2 Contains at least one fluorine atom, R 6 and R 7 Contains at least one fluorine atom, R 11 and R 12 Contains at least one fluorine atom, R 16and R 17 contains at least one fluorine atom,

[0051] The anion comprises at least one of tetrafluoroborate, hexafluorophosphate, hexafluoroarsenate, trifluoromethanesulfonate, bistrifluoromethanesulfonyl imide, bisfluorosulfonyl imide, difluorophosphate, dioxalatoborate, difluorooxalatoborate, difluorodioxalatoborate, difluorodioxalatophosphate, and tetrafluorooxalatophosphate.

[0052] In this article, the term "electrolyte" refers to the liquid electrolyte, which is the carrier for ion transport in lithium metal batteries.

[0053] In this article, the term "ionic liquid" refers to a fluid composed entirely of anions and cations at around or below 100° C. Ionic liquids have the advantages of being almost non-volatile, non-flammable, thermodynamically stable, having a wide operating temperature range and a wide electrochemical window.

[0054] In this article, the term “C 1-3 "Alkylene" refers to a divalent branched or unbranched saturated hydrocarbon chain. 1-3 Examples of alkylene include, but are not limited to: -CH 2 -、-CH 2 CH 2 -、-CH 2 CH 2 CH 2 -、-CH(CH 3 )CH 2 -、-CH 2 CH(CH 3 )-.

[0055] In this article, the term “C 1-3 "Fluoroalkylene" refers to C 1-3 At least one hydrogen atom in the alkylene group is replaced by a fluorine atom. 1-3 Examples of fluoroalkylene groups include, but are not limited to: -CHF-, -CF 2 -、-CH 2 CHF-、-CH 2 CF 2 CH 2 -、-CF(CH 3 )CH 2 -、-CF 2 CH(CH 3 )-.

[0056] In this article, the term “C 1-5 "Alkyl" is a monovalent branched or unbranched saturated hydrocarbon chain having 1, 2, 3, 4 or 5 carbon atoms. 1-5Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl.

[0057] In this article, the term “C 1-5 "Fluoroalkyl" refers to C 1-5 At least one hydrogen atom in the alkyl group is replaced by a fluorine atom. 1-5 Examples of fluoroalkylene groups include, but are not limited to: -CF 3 、-CH 2 CH 2 F, -CH 2 CF 2 CF 3 、-CF(CH 3 )CH 3 , -CF 2 CH(CH 3 )CF 3 .

[0058] In some embodiments, R 1 Contains fluorine atoms.

[0059] In some embodiments, R 2 Contains fluorine atoms.

[0060] In some embodiments, R 6 Contains fluorine atoms.

[0061] In some embodiments, R 7 Contains fluorine atoms.

[0062] In some embodiments, R 11 Contains fluorine atoms.

[0063] In some embodiments, R 12 Contains fluorine atoms.

[0064] In some embodiments, R 16 Contains fluorine atoms.

[0065] In some embodiments, R 17 Contains fluorine atoms.

[0066] Herein, the term "fluoroether structure" refers to a structure containing both an ether bond and a fluorine atom.

[0067] Herein, the term "unsaturated keto group-containing structure" refers to a structure containing an unsaturated double bond and a keto group.

[0068] In this article, the term "solvation structure" means that since the binding effect of solvent molecules in the electrolyte on cations is much stronger than that on anions, after the lithium salt is dissolved in the solvent, the solvent will gather around the lithium ions, and the aggregate formed by the lithium ions and the solvent is called the solvation structure.

[0069] First, the first solvent is an ionic liquid, which has properties such as non-volatility and flame retardancy. Adding the first solvent ionic liquid to the electrolyte can improve the flame retardancy of the electrolyte and the safety of the lithium metal battery. Secondly, the two ends of the cationic structure of the first solvent ionic liquid are functionally modified. On the one hand, one end of the cation of the ionic liquid contains an ether functional group, which can improve the ionic conductivity of the ionic liquid, reduce the viscosity of the electrolyte, increase the ionic conductivity of the electrolyte, increase the migration speed of lithium ions, and improve the kinetic performance of the system. At the same time, the fluorine atom substitution of the ether functional group also reduces the HOMO (highest occupied molecular orbital) energy level, thereby improving the antioxidant property of the ionic liquid and the antioxidant property of the electrolyte. In addition, due to the high bond energy of the CF bond, the stability of the cation is improved, and the ionic liquid containing the ether functional group has excellent compatibility with the lithium metal negative electrode, which improves the compatibility of the electrolyte with the lithium metal negative electrode, thereby improving the cycle stability of the battery; on the other hand, the other end of the cation of the first solvent ionic liquid contains an unsaturated ketone structure, which has good film-forming properties and can form a high-toughness SEI film layer composed mainly of organic components on the negative electrode surface of the lithium metal battery, reducing the possibility of SEI film layer rupture during battery cycling, thereby improving the cycle stability of the battery. At the same time, the anion of the first solvent ionic liquid can generate a high-density SEI film layer composed mainly of inorganic components on the negative electrode surface, which cooperates with the high-toughness SEI film layer composed mainly of organic components formed by the cation structure to form a stable SEI film layer.

[0070] Compared with the modification method of physically blending fluoroether compounds with basic ionic liquids, the chemical modification method of combining the fluoroether structure with the ionic liquid is more stable, and the improvement of the viscosity and conductivity of the electrolyte is more obvious, thereby improving the kinetic properties of the system. At the same time, combining the fluoroether structure with the first solvent ionic liquid by chemical modification can further improve the compatibility of the first solvent ionic liquid with the lithium metal negative electrode, improve the compatibility of the electrolyte with the lithium metal negative electrode, and improve the cycle stability of the system.

[0071] In the prior art, a film-forming additive containing an unsaturated ketone structure is physically blended with a basic ionic liquid. During the initial reaction between the film-forming additive and the lithium metal negative electrode, the film-forming additive will be completely consumed to form a SEI film layer. However, in the subsequent cycle process, the continuous deposition / stripping of lithium on the negative electrode plate will destroy the SEI film layer initially formed, making it impossible for the film-forming additive to continue to play a role in the cycle process and continue to participate in the formation of the SEI film layer. In order to overcome the above problems, the present application combines the unsaturated ketone structure with the first solvent ionic liquid by chemical modification. The unsaturated ketone structure on the ionic liquid will participate in the formation of the solvation structure of lithium ions, and continuously follow the lithium ions to migrate to the lithium metal negative electrode, forming a high-toughness SEI film layer mainly composed of organic components on the surface of the lithium negative electrode, so that the SEI film layer of the lithium negative electrode is continuously repaired during the cycle, thereby achieving a longer cycle life of the lithium negative electrode.

[0072] Compared with chemically modifying the ionic liquid with an unsaturated bond, chemically modifying the first solvent ionic liquid with a structure containing an unsaturated bond and a ketone group, the oxygen atom on the ketone group shows nucleophilicity and can interact with lithium ions to a certain extent, thereby improving the ionic conductivity.

[0073] In summary, by using the electrolyte containing the first solvent ionic liquid, the cycle stability of the battery is further improved on the basis of ensuring the safety of the lithium metal battery, thereby achieving a long life cycle of the lithium metal battery.

[0074] In some embodiments, the R 1 and R 2 The number of carbon atoms is not 1 at the same time, the R 6 and R 7 The number of carbon atoms is not 1 at the same time, the R 11 and R 12 The number of carbon atoms is not 1 at the same time; the R 16 and R 17 The number of carbon atoms is not always 1.

[0075] In some embodiments, R 1 Containing methylene or fluoromethylene, R 2 Contains C 2-5 Alkyl or C 2-5 Fluorinated alkyl.

[0076] In some embodiments, R 1 Contains C 2-3 Alkylene or C 2-3 Fluorinated alkylene, R 2 Contains C 1-5 Alkyl or C 1-5 Fluorinated alkyl.

[0077] In some embodiments, R 6 Containing methylene or fluoromethylene, R 7 Contains C 2-5 Alkyl or C 2-5 Fluorinated alkyl.

[0078] In some embodiments, R 6 Contains C 2-3 Alkylene or C 2-3 Fluorinated alkylene, R 7 Contains C 1-5 Alkyl or C 1-5 Fluorinated alkyl.

[0079] In some embodiments, R 11 Containing methylene or fluoromethylene, R 12 Contains C 2-5 Alkyl or C 2-5 Fluorinated alkyl.

[0080] In some embodiments, R 11 Contains C 2-3 Alkylene or C 2-3 Fluorinated alkylene, R 12 Contains C 1-5 Alkyl or C 1-5 Fluorinated alkyl.

[0081] In some embodiments, R 16 Containing methylene or fluoromethylene, R 17 Contains C 2-5 Alkyl or C 2-5 Fluorinated alkyl.

[0082] In some embodiments, R 16 Contains C 2-3 Alkylene or C 2-3 Fluorinated alkylene, R 17 Contains C 1-5 Alkyl or C 1-5 Fluorinated alkyl.

[0083] The number of carbon atoms in the groups at both ends of the oxygen atom in the fluoroether structure is different from 1, which can improve the stability of the fluoroether structure, so that the fluoroether structure can achieve the purpose of improving the conductivity and antioxidant properties of the first solvent ionic liquid, and achieve the purpose of improving the conductivity and antioxidant properties of the electrolyte, thereby improving the cycle performance of the battery and extending the cycle life of the battery.

[0084] In some embodiments, the R 1 , R 6 , R 11 , R 16 Each independently comprises the following groups,

[0085]

[0086] Wherein, * represents the R 1 , R 6 , R 11 , R 16 The connection site with the nitrogen atom in the structure shown in Formula I, Formula II, Formula III, and Formula IV, Represents the R 1 , R 6 , R 11 , R 16 The connection site with the oxygen atom in the structure shown in Formula I, Formula II, Formula III, and Formula IV.

[0087] R 1 , R 6 , R 11 , R 16 The carbon atom substituted with fluorine atom is not directly connected to the oxygen atom, which can weaken the interaction between fluorine atom and oxygen atom, and is beneficial to the interaction between oxygen atom of fluoroether structure and lithium ion, so that lithium ion and the first solvent ionic liquid form a more stable solvation structure, which is beneficial to the unsaturated ketone structure in the ionic liquid to reach the negative electrode surface with the solvation structure to carry out film-forming reaction, generate a high-toughness SEI film layer, improve the cycle stability of the battery, and improve the cycle performance of the battery.

[0088] In some embodiments, the R 2 , R 7 , R 12 , R 22 Each independently comprises the following groups,

[0089]

[0090] in, Representative 2 , R 7 , R 12 , R 22 The connection site with the oxygen atom in the structure shown in Formula I, Formula II, Formula III, and Formula IV.

[0091] R 2 , R 7 , R 12 , R 22The carbon atoms substituted with fluorine atoms are not directly connected to the oxygen atoms, which can weaken the interaction between the fluorine atoms and the oxygen atoms, and is beneficial to the interaction between the oxygen atoms of the fluoroether structure and the lithium ions, so that the lithium ions and the first solvent ionic liquid form a more stable solvation structure, which is beneficial for the unsaturated ketone structure in the ionic liquid to reach the negative electrode surface along with the solvation structure to undergo a film-forming reaction, thereby generating a highly tough SEI film layer, thereby improving the cycle stability of the battery and improving the cycle performance of the battery.

[0092] In some embodiments, the cation comprises at least one of the following structures,

[0093]

[0094]

[0095] In some embodiments, the cation comprises at least one of the following structures,

[0096]

[0097] The cation structures of the above formula II-1, formula II-2 and formula II-3 have a reduction potential lower than that of lithium ions, have excellent reduction resistance, and improve the cycle stability of the battery.

[0098] In some embodiments, the electrolyte further includes a second solvent, and a volume ratio of the first solvent to the second solvent is 0.1-1.

[0099] In some embodiments, the volume ratio of the first solvent to the second solvent may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or any value therebetween.

[0100] The electrolyte contains a second solvent, which can further improve the conductivity of the electrolyte. At the same time, the solvation structure formed by the second solvent and lithium ions helps the anions in the lithium salt to react on the surface of the negative electrode to form a high-density SEI film layer composed mainly of inorganic components. The high-density SEI film layer composed mainly of inorganic components and the high-toughness SEI film layer composed mainly of organic components formed by the cationic structure of the ionic liquid work together to improve the stability of the lithium metal negative electrode and the cycle performance of the battery.

[0101] In some embodiments, the volume ratio of the first solvent to the second solvent is 0.5-0.85.

[0102] In some embodiments, the volume ratio of the first solvent to the second solvent can be 0.5, 0.6, 0.7, 0.8, 0.85 or any value therebetween.

[0103] When the volume ratio of the first solvent to the second solvent is within an appropriate range, the cycle performance of the battery can be further improved and the cycle life of the battery can be extended.

[0104] In some embodiments, the second solvent includes at least one of fluorinated aromatic compounds, aromatic compounds, ester compounds, ether compounds, sulfone compounds, and nitrile compounds.

[0105] As used herein, the term "fluorinated aromatic compound" refers to a compound having a benzene ring structure and including at least one fluorine atom as a substituent.

[0106] As used herein, the term "aromatic compound" refers to a compound having a benzene ring structure.

[0107] As used herein, the term "ester compound" refers to a compound containing an ester group, including a linear ester compound and a cyclic ester compound.

[0108] As used herein, the term "ether compound" refers to a compound in which two hydrocarbon groups are linked together via an oxygen atom.

[0109] As used herein, the term "sulfone compounds" refers to a class of compounds characterized by a sulfonyl group, usually attached via sulfur to two carbon atoms.

[0110] As used herein, the term "nitrile compound" refers to a compound containing a hydrocarbon group and a cyano group linked to each other by carbon atoms.

[0111] In some embodiments, the second solvent includes ethylene carbonate, ethyl methyl carbonate, fluoroethylene carbonate, difluoroethylene carbonate, diethyl carbonate, methyl trifluoroethyl carbonate, dimethyl carbonate, benzene, toluene, p-xylene, m-xylene, o-xylene, fluorobenzene, p-difluorobenzene, m-difluorobenzene, o-difluorobenzene, trifluorotoluene, trifluoromethoxybenzene, decafluoropentane, perfluoropentanone, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane, bis(2,2,2-trifluoroethyl)ether , 1,1,2,3,3,3-hexafluoropropyl ethyl ether, 1,2,2-tetrafluoroethyl ether, ethyl trifluoromethyl ether, difluoromethyl-2,2,3,3,3-pentafluoropropyl ether, heptafluoropropyl-1,2,2,2-tetrafluoroethyl ether, difluoromethyl-2,2,3,3-tetrafluoropropyl ether, perfluoroisopropyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, ethyl-1,1,2,2-tetrafluoroethyl ether, ethyl-2,2,2-tetrafluoroethyl ether, and one or more of bis(1,1,2,2-tetrafluoroethyl) ether.

[0112] In some embodiments, the electrolyte further comprises a lithium salt, and the molar concentration of the lithium salt in the electrolyte is 0.5 mol / L-4 mol / L. In some embodiments, the molar concentration of the lithium salt in the electrolyte can be 0.5 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or any value therebetween.

[0113] In some embodiments, the molar concentration of the lithium salt in the electrolyte is 0.8 mol / L-2.2 mol / L. In some embodiments, the molar concentration of the lithium salt in the electrolyte may be 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, 2.0 mol / L, 2.2 mol / L or any value therebetween.

[0114] The appropriate molar concentration of lithium salt makes the electrolyte have excellent electrical conductivity, while ensuring that a sufficient number of lithium salt anions participate in the formation of a high-density SEI film layer mainly composed of inorganic components, thereby comprehensively improving the cycle performance of the battery.

[0115] In some embodiments, the lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium trifluoroacetate, lithium tetraphenylborate, lithium trifluoromethylsulfonate, lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide.

[0116] In some embodiments, the lithium salt includes lithium hexafluorophosphate.

[0117] Lithium hexafluorophosphate has excellent cycle stability in lithium metal battery systems and improves the cycle performance of the battery.

[0118] The electrolyte proposed in this application can be prepared by the following method:

[0119] At room temperature, in a stirring mixing tank, lithium salt is added to the first solvent and stirred and dissolved to obtain an electrolyte.

[0120] In some embodiments, at room temperature, in a stirring mixing tank, after the first solvent and the second solvent are evenly mixed, the lithium salt is added thereto and stirred to be fully dissolved to obtain an electrolyte.

[0121] In some embodiments, a lithium metal battery is provided, including the electrolyte in some embodiments.

[0122] In some embodiments, a lithium metal battery comprises a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte in any embodiment.

[0123] [Positive electrode]

[0124] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

[0125] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0126] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0127] In some embodiments, the positive electrode active material may adopt a positive electrode active material for a battery known in the art. As an example, the positive electrode active material may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxide (such as LiNiO 2 ), lithium manganese oxide (such as LiMnO 2 、LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (also referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O 2 ) and its modified compounds, etc. Examples of lithium phosphates containing olivine structures may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also referred to as LFP), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), at least one of a composite material of lithium manganese phosphate and carbon, a composite material of lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0128] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene (HFP)-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0129] In some embodiments, the positive electrode film layer may further include a conductive agent, which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0130] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0131] [Negative electrode]

[0132] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0133] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0134] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0135] In some embodiments, the negative electrode active material is metallic lithium.

[0136] In some embodiments, the negative electrode active material may be an alloy of metallic lithium and other metal or non-metal elements. The metal element includes any one or more of tin (Sn), zinc (Zn), aluminum (Al), magnesium (Mg), silver (Ag), gold (Au), gallium (Ga), indium (In), and platinum (Pt). The metalloid element includes one or more of boron (B), carbon (C), and silicon (Si).

[0137] In some embodiments, the negative electrode sheet can be prepared by the following method: the upper negative electrode active material is coated on the negative electrode current collector by rolling, and after a cutting process, the negative electrode sheet can be obtained.

[0138] [Isolation film]

[0139] In some embodiments, the lithium metal battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0140] In some embodiments, the material of the isolation membrane can be selected from at least one of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fiber. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0141] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0142] In some embodiments, the lithium metal battery may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

[0143] In some embodiments, the outer packaging of the lithium metal battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the lithium metal battery can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, and as the plastic, polypropylene, polybutylene terephthalate, and polybutylene succinate can be listed.

[0144] The present application has no particular limitation on the shape of the lithium metal battery, which may be cylindrical, square or any other shape. Figure 1 A lithium metal battery 5 having a square structure is used as an example.

[0145] In some embodiments, reference Figure 2 , the outer packaging may include a shell 51 and a cover plate 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the lithium metal battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0146] In some embodiments, lithium metal batteries can be assembled into a battery module. The number of lithium metal batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0147] Figure 3 4 is an example of a battery module. Figure 3 In the battery module 4, the plurality of lithium metal batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of lithium metal batteries 5 may be fixed by fasteners.

[0148] Optionally, the battery module 4 may further include a housing having a housing space, and the plurality of lithium metal batteries 5 are accommodated in the housing space.

[0149] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0150] Figure 4 and Figure 5 1 is a battery pack 1 as an example. Figure 4 and Figure 5The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0151] In addition, the present application also provides an electrical device, which includes at least one of the lithium metal battery, battery module, or battery pack provided in the present application. The lithium metal battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0152] As the electrical device, a lithium metal battery, a battery module or a battery pack can be selected according to its usage requirements.

[0153] Figure 6 The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the lithium metal battery of the power consumption device, a battery pack or a battery module can be used.

[0154] Another example of a device may be a mobile phone, a tablet computer, a laptop computer, etc. Such a device is usually required to be light and thin, and a lithium metal battery may be used as a power source.

[0155] Example

[0156] The following are examples of the present application. The examples described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the art or in the product instructions shall be followed. The reagents or instruments used without indicating the manufacturer are all conventional products that can be obtained commercially. In the following examples, only the case of lithium metal batteries is shown, but the present application is not limited thereto.

[0157] 1. Preparation method

[0158] Example 1

[0159] 1) Preparation of electrolyte

[0160] In an argon atmosphere glove box with a water content of less than 10 ppm, 4 ml of the first solvent and 6 ml of the second solvent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether were fully mixed to form a mixed solution, 20 mmol of lithium bis(fluorosulfonyl)imide was added thereto, and the mixture was stirred to obtain the electrolyte of Example 1, wherein the molar concentration of the lithium salt in the electrolyte was 2 mol / L, the cation of the first solvent was shown in Formula Ⅰ-1, and the anion of the first solvent was hexafluorophosphate.

[0161]

[0162] 2) Preparation of positive electrode

[0163] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 The binder polyvinylidene fluoride (PVDF) and the conductive agent acetylene black were mixed in N-methylpyrrolidone (NMP) solvent in a mass ratio of 98%:1%:1% to prepare the positive electrode slurry. The positive electrode slurry was heated at 25 mg / cm 2 The loading amount is evenly coated on both sides of the positive electrode collector aluminum foil, dried at room temperature, transferred to an oven for further drying, and then cut into 40mm*50mm rectangles as positive electrode sheets.

[0164] 3) Preparation of negative electrode sheet

[0165] A 50 μm thick lithium foil was rolled onto a 12 μm thick copper foil and then cut into a 41 mm*51 mm rectangle as a negative electrode sheet.

[0166] 4) Isolation film

[0167] A polyethylene film (PE membrane) is used as the isolation membrane.

[0168] 5) Preparation of batteries

[0169] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is between the positive and negative electrode sheets to play an isolating role, and the electrolyte is added to assemble a lithium metal battery.

[0170] Embodiment 2-8

[0171] The difference between Example 2-8 and Example 1 is that the structure of the first solvent is adjusted, wherein the structures of the cations of the first solvents of Example 2-8 are shown below in sequence:

[0172]

[0173]

[0174] The anions of the first solvent in Examples 2-8 are difluorooxalatoborate, bistrifluoromethylsulfonyl imide, bisfluorosulfonyl imide, bisfluorosulfonyl imide, bisfluorosulfonyl imide, bisfluorosulfonyl imide, bisfluorosulfonyl imide, and bisfluorosulfonyl imide, respectively.

[0175] Examples 9-12

[0176] The difference between Examples 9-12 and Example 4 is that the volume ratio of the first solvent to the second solvent is adjusted. For specific parameters, see Table 1.

[0177] Comparative Examples 1-8

[0178] The difference between Comparative Examples 1-8 and Example 4 is that the formula of the electrolyte is adjusted. The specific electrolyte formula is as follows:

[0179] Comparative Example 1: In an argon atmosphere glove box with a water content of less than 10 ppm, 4 ml of ethylene glycol dimethyl ether and 6 ml of the second solvent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether were fully mixed to form a mixed solution, 20 mmol of lithium bis(fluorosulfonyl)imide was added thereto, and the mixture was stirred and mixed to obtain the electrolyte of Comparative Example 1, wherein the molar concentration of the lithium salt in the electrolyte was 2 mol / L.

[0180] Comparative Example 2: In an argon atmosphere glove box with a water content of less than 10 ppm, 4 ml of the first solvent and 6 ml of the second solvent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether were fully mixed to form a mixed solution, 20 mmol of lithium bis(fluorosulfonyl)imide was added thereto, and the mixture was stirred to obtain the electrolyte of Comparative Example 2, wherein the molar concentration of the lithium salt in the electrolyte was 2 mol / L, and the cation of the first solvent of Comparative Example 2 was as shown in Formula VI-1, and the anion was bis(fluorosulfonyl)imide.

[0181]

[0182] Comparative Example 3: In an argon atmosphere glove box with a water content of less than 10 ppm, 4 ml of the first solvent and 6 ml of the second solvent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether were fully mixed to form a mixed solution, 20 mmol of lithium bis(fluorosulfonyl)imide was added thereto, and the mixture was stirred to obtain the electrolyte of Comparative Example 3, wherein the molar concentration of the lithium salt in the electrolyte was 2 mol / L, and the cation of the first solvent of Comparative Example 3 was as shown in Formula VI-2, and the anion was bis(fluorosulfonyl)imide.

[0183]

[0184] Comparative Example 4: In an argon atmosphere glove box with a water content of less than 10 ppm, 4 ml of the first solvent, 4 ml of 2,2,2-trifluoroethyl ethyl ether, 4 ml of vinylene carbonate and 6 ml of the second solvent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether were fully mixed to form a mixed solution, 36 mmol of lithium bis(fluorosulfonyl)imide was added thereto, and the mixture was stirred to obtain the electrolyte of Comparative Example 4, wherein the molar concentration of the lithium salt in the electrolyte was 2 mol / L, the cation of the first solvent of Comparative Example 4 was shown in the above-mentioned formula VI-1, and the anion was bis(fluorosulfonyl)imide.

[0185] Comparative Example 5: In an argon atmosphere glove box with a water content of less than 10 ppm, 4 ml of the first solvent and 6 ml of the second solvent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether were fully mixed to form a mixed solution, 20 mmol of lithium bis(fluorosulfonyl)imide was added thereto, and the mixture was stirred to obtain the electrolyte of Comparative Example 5, wherein the molar concentration of the lithium salt in the electrolyte was 2 mol / L, and the cation of the first solvent of Comparative Example 5 was as shown in Formula VI-3, and the anion was bis(fluorosulfonyl)imide.

[0186]

[0187] Comparative Example 6: In an argon atmosphere glove box with a water content of less than 10 ppm, 4 ml of the first solvent, 4 ml of vinylene carbonate and 6 ml of the second solvent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether were fully mixed to form a mixed solution, 28 mmol of lithium bis(fluorosulfonyl)imide was added thereto, and the mixture was stirred to obtain the electrolyte of Comparative Example 6, wherein the molar concentration of the lithium salt in the electrolyte was 2 mol / L, the cation of the first solvent of Comparative Example 6 was as shown in the above-mentioned formula VI-3, and the anion was bis(fluorosulfonyl)imide.

[0188] Comparative Example 7: In an argon atmosphere glove box with a water content of less than 10 ppm, 4 ml of the first solvent and 6 ml of the second solvent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether were fully mixed to form a mixed solution, 20 mmol of lithium bis(fluorosulfonyl)imide was added thereto, and the mixture was stirred to obtain the electrolyte of Comparative Example 7, wherein the molar concentration of the lithium salt in the electrolyte was 2 mol / L, and the cation of the first solvent of Comparative Example 7 was as shown in Formula VI-4, and the anion was bis(fluorosulfonyl)imide.

[0189]

[0190] Comparative Example 8: In an argon atmosphere glove box with a water content of less than 10 ppm, 4 ml of the first solvent, 4 ml of 2,2,2-trifluoroethyl ethyl ether and 6 ml of the second solvent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether were fully mixed to form a mixed solution, 28 mmol of lithium bis(fluorosulfonyl)imide was added thereto, and the mixture was stirred to obtain the electrolyte of Comparative Example 8, wherein the molar concentration of the lithium salt in the electrolyte was 2 mol / L, the cation of the first solvent of Comparative Example 8 was as shown in the above-mentioned formula VI-4, and the anion was bis(fluorosulfonyl)imide.

[0191] Comparative Example 9: In an argon atmosphere glove box with a water content of less than 10 ppm, 4 ml of the first solvent and 6 ml of the second solvent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether were fully mixed to form a mixed solution, 20 mmol of lithium bis(fluorosulfonyl)imide was added thereto, and the mixture was stirred to obtain the electrolyte of Comparative Example 9, wherein the molar concentration of the lithium salt in the electrolyte was 2 mol / L, and the cation of the first solvent of Comparative Example 9 was as shown in Formula VI-5, and the anion was bis(fluorosulfonyl)imide.

[0192]

[0193] 2. Test Method

[0194] 1) Lithium metal battery room temperature cycle performance

[0195] The lithium metal battery was placed in a constant temperature box at 25℃±2℃ and allowed to stand for 2 hours. The cycle process was: charged to 4.3V at a constant current of 0.2C, then charged to 0.05C at a constant voltage of 4.3V and allowed to stand for 5 minutes, and then discharged to 2.8V at 1C. This was a charge and discharge cycle process, and the charge and discharge capacity of the lithium metal battery in the first cycle was recorded; with the capacity of the first discharge being 100%, the charge and discharge cycle was repeated, and the number of cycles when the capacity retention rate of the lithium metal battery dropped to 80% was recorded. Ten lithium metal batteries were taken from each group, and the average value of the number of cycles when the capacity retention rate of the lithium metal battery dropped to 80% was calculated, which was the number of cycles for each group.

[0196] 3. Test Results

[0197] The test results of the above embodiments and comparative examples are shown in Table 1.

[0198] Table 1

[0199]

[0200] According to the above results, the electrolyte in Examples 1-12 includes a first solvent, the first solvent includes cations and anions, and the cations include

[0201] Any one of the following, wherein the anion comprises any one of hexafluorophosphate, bisfluorosulfonyl imide, difluorooxalatoborate, and bistrifluoromethylsulfonyl imide.

[0202] From the comparison between Examples 1-12 and Comparative Example 1, it can be seen that compared with the electrolyte containing ethylene glycol dimethyl ether solvent in the prior art, the electrolyte containing the first solvent ionic liquid of the present application can effectively increase the number of normal temperature cycles of the battery and extend the cycle life of the battery. From Examples 1-8 and Comparative Example 2, it can be seen that compared with the electrolyte containing the unmodified ionic liquid, that is, containing the cation shown in Formula VI-1,

[0203] The electrolyte of the present application can increase the number of normal temperature cycles of the battery and extend the cycle life of the battery. From the comparison between Examples 1-8 and Comparative Example 3, it can be seen that compared with the electrolyte containing the cationic structure of Formula VI-2,

[0204] The electrolyte of the present application can increase the number of normal temperature cycles of the battery and extend the cycle life of the battery. As can be seen from the comparison between Examples 1-8 and Comparative Example 4, compared with the electrolyte containing the cationic structure of Formula VI-1 and 2,2,2-trifluoroethyl ethyl ether and vinylene carbonate, the ionic liquid of the present application can increase the number of normal temperature cycles of the battery and extend the cycle life of the battery. As can be seen from the comparison between Examples 1-8 and Comparative Example 5, the electrolyte containing the cationic structure of Formula VI-3,

[0205] The electrolyte of the present application can increase the number of normal temperature cycles of the battery and extend the cycle life of the battery. From the comparison between Examples 1-8 and Comparative Example 6, it can be seen that compared with the electrolyte containing the cationic structure of Formula VI-3 and vinylene carbonate, the electrolyte of the present application can increase the number of normal temperature cycles of the battery and extend the cycle life of the battery. From the comparison between Examples 1-8 and Comparative Example 7, it can be seen that compared with the electrolyte containing the cationic structure of Formula VI-4,

[0206] The electrolyte of the present application can increase the number of normal temperature cycles of the battery and extend the cycle life of the battery. From the comparison between Examples 1-8 and Comparative Example 8, it can be seen that compared with the electrolyte containing the cationic structure of Formula VI-4 and 2,2,2-trifluoroethyl ethyl ether, the electrolyte of the present application can increase the number of normal temperature cycles of the battery and extend the cycle life of the battery. From the comparison between Examples 1-8 and Comparative Example 9, it can be seen that compared with the electrolyte containing the cationic structure of Formula VI-5,

[0207] The use of the electrolyte of the present application can increase the number of normal temperature cycle cycles of the battery and extend the cycle life of the battery.

[0208] From the comparison between Examples 4-6 and 8 and Example 7, it can be seen that compared with the R in the cation structure of the first solvent ionic liquid, 6 and R 7 The number of carbon atoms is 1, that is, the cationic structure shown in Formula II-4, and the R in the cationic structure of the first solvent ionic liquid is controlled. 6 and R 7 The number of carbon atoms is not 1 at the same time, that is, the cationic structures shown in Formula II-1, Formula II-2, Formula II-3 and Formula II-5 can further increase the number of cycles of the battery at room temperature and further improve the cycle stability of the battery.

[0209] From the comparison between Examples 4-6 and 7-8, it can be seen that compared with the R in the cation structure of the first solvent ionic liquid in Examples 7-8, 7 for That is, the cation structures shown in Formula II-4 and Formula II-5, and R in the cation structure of the first solvent ionic liquid in Example 4-6 7 for That is, the cationic structures shown in Formula II-1, Formula II-2 and Formula II-3 can further increase the number of cycles of the battery at room temperature and further extend the cycle life of the battery.

[0210] From Examples 1-12, it can be seen that the electrolyte comprises a first solvent ionic liquid and a second solvent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, wherein the volume ratio of the first solvent ionic liquid to the second solvent is 0.1-1, and the battery has a high number of normal temperature cycles and excellent cycle performance. From the comparison of Examples 4, 10-11 with Examples 9 and 12, it can be seen that the volume ratio of the first solvent ionic liquid to the second solvent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether is 0.5-0.85, which can further increase the number of normal temperature cycles of the battery and improve the cycle performance of the battery.

[0211] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. An electrolyte, characterized in that: The method comprises a first solvent, wherein the first solvent comprises anions and cations, wherein the cations comprise at least one of the structures shown in Formula I, Formula II, Formula III, and Formula IV, Among them, R1, R6, R 11 , R 16 Each independently contains C 1-3 Alkylene or C 1-3 Fluorinated alkylene, R2, R7, R 12 , R 22 Each independently contains C 1-5 Alkyl or C 1-5 Fluorinated alkyl, R3, R4, R8, R9, R 13 , R 14 , R 18 , R 19 Each independently contains C 1-3 Alkylene, R5, R 10 , R 15 , R 20 , R 21 , R 22 Each independently contains C 1-3 Alkyl, R1 and R2 contain at least one fluorine atom, R6 and R7 contain at least one fluorine atom, R 11 and R 12 Contains at least one fluorine atom, R 16 and R 17 contains at least one fluorine atom, The anion comprises at least one of tetrafluoroborate, hexafluorophosphate, hexafluoroarsenate, trifluoromethanesulfonate, bistrifluoromethanesulfonyl imide, bisfluorosulfonyl imide, difluorophosphate, dioxalatoborate, difluorooxalatoborate, difluorodioxalatoborate, difluorodioxalatophosphate, and tetrafluorooxalatophosphate.

2. The electrolyte according to claim 1, characterized in that The number of carbon atoms of R1 and R2 is not 1 at the same time, the number of carbon atoms of R6 and R7 is not 1 at the same time, and the R 11 and R 12 The number of carbon atoms is not 1 at the same time, the R 16 and R 17 The number of carbon atoms is not always 1.

3. The electrolyte according to claim 1 or 2, characterized in that R1, R6, R 11 , R 16 Each independently comprises the following groups, Wherein, * represents the R1, R6, R 11 , R 16 The connection site with the nitrogen atom in the structure shown in Formula I, Formula II, Formula III, and Formula IV, Represents the R1, R6, R 11 , R 16 The connection site with the oxygen atom in the structure shown in Formula I, Formula II, Formula III, and Formula IV.

4. The electrolyte according to any one of claims 1 to 3, characterized in that R2, R7, R 12 , R 22 Each independently comprises the following groups, in, Represents R2, R7, R 12 , R 22 The connection site with the oxygen atom in the structure shown in Formula I, Formula II, Formula III, and Formula IV.

5. The electrolyte according to any one of claims 1 to 4, characterized in that The cation comprises at least one of the following structures, 6. The electrolyte according to any one of claims 1 to 5, characterized in that The electrolyte further includes a second solvent, and the volume ratio of the first solvent to the second solvent is 0.1-1, preferably 0.5-0.

85.

7. The electrolyte according to any one of claims 1 to 6, characterized in that The electrolyte further includes a lithium salt, and the molar concentration of the lithium salt in the electrolyte is 0.5 mol / L-4 mol / L, and can be optionally 0.8 mol / L-2.2 mol / L.

8. The electrolyte according to claim 6 or 7, characterized in that The second solvent includes at least one of fluorinated aromatic compounds, aromatic compounds, ester compounds, ether compounds, sulfone compounds, and nitrile compounds, and can be selected from ethylene carbonate, ethyl methyl carbonate, fluoroethylene carbonate, difluoroethylene carbonate, diethyl carbonate, methyl trifluoroethyl carbonate, dimethyl carbonate, benzene, toluene, p-xylene, m-xylene, o-xylene, fluorobenzene, p-difluorobenzene, m-difluorobenzene, o-difluorobenzene, trifluorotoluene, trifluoromethoxybenzene, decafluoropentane, perfluoropentanone, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,2-bis(1,1,2,2-tetrafluoro One or more of 1,2,2-trifluoroethyl)ethane, bis(2,2,2-trifluoroethyl)ether, 1,1,2,3,3,3-hexafluoropropyl ethyl ether, 1,2,2-tetrafluoroethyl ether, ethyl trifluoromethyl ether, difluoromethyl-2,2,3,3,3-pentafluoropropyl ether, heptafluoropropyl-1,2,2,2-tetrafluoroethyl ether, difluoromethyl-2,2,3,3-tetrafluoropropyl ether, perfluoroisopropyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, ethyl-1,1,2,2-tetrafluoroethyl ether, ethyl-2,2,2-tetrafluoroethyl ether, and bis(1,1,2,2-tetrafluoroethyl)ether.

9. The electrolyte according to claim 7 or 8, characterized in that The lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium trifluoroacetate, lithium tetraphenylborate, lithium trifluoromethylsulfonate, lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide, and lithium hexafluorophosphate may be selected.

10. A lithium metal battery, characterized in that: The electrolyte comprising the electrolyte described in any one of claims 1 to 9.

11. An electrical device, characterized in that: Including the lithium metal battery as described in claim 10.

Images