Ionic liquid, electrolyte, battery monomer and electric device

Abstract

The invention relates to the technical field of secondary batteries, and provides an ionic liquid, an electrolyte, a battery monomer and an electric device. The ionic liquid provided by the invention comprises cations shown as a structural formula of # imgabs0 #. According to the ionic liquid provided by the invention, cations, pyrrolidine and R4 containing unsaturated groups have relatively high reduction resistance and compatibility, so that the oxidation resistance of the ionic liquid is improved, the oxidation resistance of the ionic liquid can be further improved by alkyl, alkoxy and fluoroalkyl, and the reliability of the secondary battery can be obviously improved after combination; the nitrile group can effectively improve the ionic conductivity of the ionic liquid and promote the transmission of lithium ions, so that the coulombic efficiency and the rate capability of the secondary battery are improved; according to the present invention, the silicon group with the film forming tendency can be combined with R4 to form the high toughness interface layer, the reaction of the nitrile group and the active ion can be blocked, and the effect of the significant improvement of the cycle life of the secondary battery can be achieved, such that the ion liquid can provide the high cycle performance and the high reliability of the secondary battery.

Description

Technical Field

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

[0002] Lithium metal batteries are highly promising next-generation batteries with high energy density due to their high theoretical energy density and low negative electrode potential. Currently, lithium-ion batteries dominate the portable electronics market, and their applications have penetrated into all aspects of daily life, such as cameras, laptops, electric vehicles, etc.

[0003] During the first charge and discharge process of a lithium-ion battery, the electrode material and the electrolyte react at the solid-liquid interface to form a passivation layer covering the surface of the electrode material. This passivation layer is an interface layer that has the characteristics of a solid electrolyte. It is an electronic insulator but an excellent conductor of lithium. Lithium can be freely embedded and removed through this passivation layer. An excellent interface layer can effectively prevent the electrode material and the electrolyte from continuously reacting on the surface of the cathode and anode, thereby protecting the cathode and anode. However, as the secondary battery is charged and discharged, the interface layer at the positive and negative electrode interfaces is unstable and easily damaged, which affects the cycle performance of the secondary battery and brings great safety hazards to the battery.

[0004] The above statements are only used to provide background information related to the present application and do not necessarily constitute prior art. Summary of the invention

[0005] The purpose of the present application is to provide an ionic liquid, an electrolyte, a battery cell and an electrical device, aiming to solve the problem of unsatisfactory cycle performance and reliability of lithium-ion batteries.

[0006] In order to achieve the above application purpose, the technical solution adopted in this application is as follows:

[0007] In a first aspect, the present application provides an ionic liquid, wherein the ionic liquid comprises a cation as shown in formula I:

[0008]

[0009] Wherein, R0, R1, R2, and R3 each independently include C1 to C 10 Alkyl, C1~C 10 Alkoxy, C1~C 10 Any one of the fluoroalkyl groups; R4 is an unsaturated group containing a double bond.

[0010] The ionic liquid provided by the embodiments of the present application has a pyrrolidine as the main body of its cation, and a nitrile group, a silicon group, an alkyl group, an alkoxy group, a fluoroalkyl group, and an unsaturated group containing a double bond are introduced into the pyrrolidine. Among them, pyrrolidine and R4 containing an unsaturated group have high reducibility resistance and compatibility, so that the ionic liquid remains stable in a reducing environment. The alkyl group, alkoxy group, and fluoroalkyl group can further improve the antioxidant performance of the ionic liquid. After such combination, the reliability of the secondary battery can be significantly improved; the nitrile group can effectively improve the ionic conductivity of the ionic liquid and promote the transport of lithium ions, thereby improving the Coulomb efficiency and rate performance of the secondary battery; the silicon group with a film-forming tendency combined with R4 can form a highly tough interfacial layer, blocking the reaction between the nitrile group and active ions, and significantly improving the cycle life of the secondary battery. Thus, this ionic liquid can enable the secondary battery to exhibit high cycle performance and reliability.

[0011] In some embodiments, R0, R1, R2, and R3 each independently include any one of an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, and a fluoroalkyl group having 1 to 3 carbon atoms.

[0012] The alkyl group, alkoxy group, and fluoroalkyl group having 1 to 3 carbon atoms can improve the antioxidant performance of the ionic liquid, thereby extending the cycle life of the battery.

[0013] In some embodiments, at least one of R0, R1, R2, and R3 includes a fluoroalkyl group having 1 to 3 carbon atoms.

[0014] The fluoroalkyl group, on the one hand, can improve the antioxidant performance of the ionic liquid. On the other hand, the fluoroalkyl group can increase the content of inorganic substances in the interfacial layer. Especially when a fluoroalkyl group is introduced into the cation of the ionic liquid, the fluoroalkyl group is more likely to enter the first Helmholtz layer, thereby improving the stability of the interfacial layer.

[0015] The Helmholtz layer refers to when the electrode is in contact with the solution, due to the transfer of charged particles between the two phases, or by charging both sides of the electrode interface through an external circuit, excess charges will be induced in both phases. These excess charges are distributed in the thin layers on both sides of the interface, forming an electrochemical double layer, simply referred to as a double layer. The first Helmholtz layer refers to the electrochemical layer close to the electrode side.

[0016] In some embodiments, R4 includes any one of them, and the wavy line indicates the bonding position of R4 to the silicon group in Formula I.

[0017] These R4 groups not only have high reducibility resistance but also have high compatibility with the electrode material, making the ionic liquid have stability and universality.

[0018] In some embodiments, the ionic liquid includes at least one of the cations shown in Formula I-1 to Formula I-12:

[0019]

[0020]

[0021] In the embodiments of the present application, the ionic liquid cations represented by Formula I-1 to Formula I-12 are beneficial to forming an interfacial layer with high ionic conductivity, strong toughness, and excellent stability on the surface of the electrode material, and can also improve the flame retardancy of the secondary battery. Thus, the secondary battery has a long cycle life and high safety.

[0022] In some embodiments, the anions of the ionic liquid include at least one of bis(fluorosulfonyl)imide anion, tetrafluoroborate anion, bis(trifluoromethylsulfonyl)imide anion, hexafluorophosphate anion, hexafluoroarsenate anion, trifluoromethanesulfonate anion, difluorophosphate anion, bis(oxalato)borate anion, difluoro(oxalato)borate anion, difluoro(dioxalato)phosphate anion, and tetrafluoro(oxalato)phosphate anion.

[0023] These anions can improve the stability and solubility of the ionic liquid, and this stability enables the ionic liquid to be used as a medium for high-temperature or oxidation reactions, such as enabling the ionic liquid to be used as an additive and / or solvent for the electrolyte.

[0024] In some embodiments, the anions of the ionic liquid include bis(fluorosulfonyl)imide anion.

[0025] The bis(fluorosulfonyl)imide anion has high stability and can remain stable under high-temperature or oxidation conditions, and this stability is beneficial to improving the energy density and cycle life of the battery.

[0026] In a second aspect, the present application provides an application of an ionic liquid as an electrolyte solvent, and the ionic liquid includes the ionic liquid provided in the first aspect of the present application.

[0027] The ionic liquid has high ionic conductivity, stability, antioxidant property, and flame retardancy. Therefore, the ionic liquid can be used as an electrolyte solvent to improve the ionic conductivity and stability of the electrolyte.

[0028] In a third aspect, the present application provides an electrolyte, including an electrolyte and a solvent, and the solvent includes the ionic liquid provided in the first aspect of the present application.

[0029] The electrolyte provided by the present application includes an electrolyte and a solvent, and the solvent includes the ionic liquid of the present application. On the one hand, the ionic liquid has high flame retardancy, which is beneficial to improving the safety of the electrolyte, especially the battery. On the other hand, R4 containing unsaturated groups introduced into the ionic liquid has high reducibility resistance and compatibility, which means that the ionic liquid can maintain stability in a reducing environment, is not prone to chemical changes or being reduced, so that the ionic liquid has high stability and versatility. Combining alkyl, alkoxy, and fluoroalkyl can further improve the antioxidant performance of the ionic liquid. In this way, the reliability of the secondary battery can be significantly improved. On the other hand, the nitrile group introduced into the ionic liquid can effectively improve the ionic conductivity of the ionic liquid, promote the transport of lithium ions, and thus improve the Coulomb efficiency and rate performance of the secondary battery. On the other hand, the silicon-based with a film-forming tendency combined with R4 can form a high-toughness interfacial layer, blocking the reaction between the nitrile group and active ions, and playing an obvious role in improving the cycle life of the secondary battery. In this way, the electrolyte can make the secondary battery exhibit high cycle performance and reliability. In addition, the ionic liquid has excellent solubility in the electrolyte, thereby forming an electrolyte without separation phenomenon, making the transport of active ions smoother and obtaining an electrolyte with high stability.

[0030] In some embodiments, the electrolyte includes a lithium salt.

[0031] The lithium salt has high ionic conductivity and good stability, which means that it can transfer charges more effectively in the electrolyte, thereby improving the efficiency and electrochemical performance of the battery.

[0032] In some embodiments, the concentration of the electrolyte is 0.5 mol / L to 4 mol / L.

[0033] In some embodiments, the concentration of the electrolyte is 2 mol / L.

[0034] Within this concentration range of the electrolyte, the electrolyte has high conductivity and stability, promoting the migration and transport of active ions.

[0035] In some embodiments, the electrolyte includes at least one of lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(trifluoromethylsulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium difluoro bis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0036] These electrolytes have high solubility in the ionic liquid. On the one hand, it is beneficial to the exertion of the electrolyte conductivity, promotes the transport of active ions, and makes the electrolyte exhibit a high active ion mobility. On the other hand, it makes the electrolyte and the ionic liquid not undergo obvious chemical reactions or phase separation, thereby maintaining the stability of the electrolyte.

[0037] In some embodiments, the electrolyte includes lithium bis(fluorosulfonyl)imide.

[0038] Lithium bis(fluorosulfonyl)imide has high conductivity, a wide liquid range, and excellent lithium ion transference number, enabling the electrolyte solution to have high conductivity, stability, and lithium ion transmission rate, thus facilitating the improvement of the rate performance and cycling performance of the battery.

[0039] In some embodiments, the solvent further includes an auxiliary solvent, and the auxiliary solvent includes at least one of benzene solvents, fluorinated hydrocarbon solvents, and ether solvents. Under normal circumstances, these auxiliary solvents cannot dissolve the electrolyte, but have good compatibility with ionic liquids. Thus, on the basis of improving the viscosity of the electrolyte solution, the solvation process of the electrolyte is not affected.

[0040] In some embodiments, the volume ratio of the ionic liquid to the auxiliary solvent is 1:9 to 9:1.

[0041] In some embodiments, the volume ratio of the ionic liquid to the auxiliary solvent is 4:6.

[0042] By controlling the volume ratio of the ionic liquid to the auxiliary solvent within the above range in the embodiments of the present application, the viscosity of the electrolyte solution can be effectively improved, thereby facilitating the increase of the transmission rate of active ions in the electrolyte solution.

[0043] In some embodiments, the auxiliary solvent has at least one of the following characteristics (1) to (3):

[0044] (1) The benzene solvent includes at least one of cyclohexane, benzene, toluene, p-xylene, m-xylene, o-xylene, fluorobenzene, p-difluorobenzene, m-difluorobenzene, o-difluorobenzene, trifluorotoluene, and trifluoromethoxybenzene;

[0045] (2) The fluorinated hydrocarbon solvent includes decafluoropentane, perfluoropentanone, and 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane;

[0046] (3) The ether solvent includes at least one of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl) ether, 1,1,2,3,3,3-hexafluoropropyl ethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-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.

[0047] These auxiliary solvents not only have high stability but also have excellent compatibility with ionic liquids. Thus, the viscosity of the electrolyte can be effectively improved, and the transport of active ions can be promoted.

[0048] In a fourth aspect, the present application provides a battery cell, including the electrolyte provided in the second aspect of the embodiments of the present application.

[0049] By providing this electrolyte, the battery cell improves the cycle performance and high-rate capacity of the battery.

[0050] In a fifth aspect, the present application provides a battery, including the battery cell of the present application.

[0051] By providing this battery cell, the battery improves its electrochemical properties including cycle performance.

[0052] In a sixth aspect, the present application provides an electrical device, including the battery of the present application.

[0053] By providing this battery, the electrical device has a long standby or endurance time, good safety, and a relatively low replacement frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present application. Moreover, in all the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0055] Figure 1 is a schematic structural diagram of a vehicle in some embodiments of the present application;

[0056] Figure 2 is an exploded structural diagram of a battery in some embodiments of the present application;

[0057] Figure 3 is a schematic structural diagram of a battery cell in some embodiments of the present application.

[0058] Among them, the reference numerals in the drawings:

[0059] 1000, vehicle;

[0060] 100, battery, 200, controller, 300, motor;

[0061] 10, box body, 11, upper box body, 12, lower box body;

[0062] 20, battery cell, 21, housing, 22, electrode assembly, 23, cover plate. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0063] The embodiments of the technical solution of the present application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solution of the present application more clearly, and thus are only examples and cannot be used to limit the protection scope of the present application.

[0064] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusion.

[0065] In the description of the embodiments of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0066] Referring to "embodiments" herein means that the specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of this application. The phrase appears in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0067] In the description of the embodiments of this application, the term "and / or" is only a description of the association relationship of associated objects, indicating that there can be three relationships, for example, A and / or B, which can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after.

[0068] In the description of the embodiments of this application, the term "plurality" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0069] In the description of the embodiments of the present application, the orientation or positional relationship indicated by technical terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the embodiments of the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the embodiments of the present application.

[0070] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installation", "connection", "coupling", "fixation", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can also be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0071] In the present application, "at least one" means one or more, and "a plurality" means two or more. "At least one (item)" or its similar expression refers to any combination of these items, including any combination of single item (item) or plural items (items). For example, "at least one (item) of a, b, or c", or, "at least one (item) of a, b, and c" can all represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0072] It should be understood that in various embodiments of the present application, the magnitude of the sequence numbers of the above processes does not mean the sequence of execution. Some or all steps can be executed in parallel or sequentially, and the execution sequence of each process should be determined according to its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

[0073] In the description of the embodiments of the present application, the weight of the relevant components mentioned not only can refer to the specific content of each component, but also can represent the proportional relationship of the weights between the components. Therefore, as long as the content of the relevant components in the description of the embodiments of the present application is scaled up or down proportionally, it is within the scope disclosed in the description of the embodiments of the present application. Specifically, the mass described in the description of the embodiments of the present application can be mass units well known in the chemical industry such as μg, mg, g, kg, etc.

[0074] In the description of the embodiments of the present application, the SEI film is an abbreviation of "solid electrolyte interface", which refers to a solid electrolyte interface film with the characteristics of a solid electrolyte, that is, during the first charge and discharge process of a liquid lithium-ion battery, a passivation layer formed by the reaction between the electrode material and the electrolyte at the solid-liquid phase interface forms a film covering the surface of the negative electrode material.

[0075] Lithium metal batteries are promising next-generation batteries with high energy density due to their high theoretical energy density and low negative electrode potential. Due to the high reactivity of lithium metal, it will react with the electrolyte to form a passivation film covering the electrode surface, that is, the SEI film. This passivation film can block the subsequent reaction between the electrode and the electrolyte. However, during the charge and discharge cycle of the battery, the volume of the lithium metal electrode will change continuously, causing the rupture of the SEI film, generating dead lithium, resulting in a decrease in the cycle efficiency. At the same time, the rupture of the SEI film will also cause irregular deposition of lithium ions, generating lithium dendrites. Lithium dendrites have the risk of penetrating the separator and causing a short circuit, bringing great safety hazards to the application of the battery.

[0076] Developing a flame-retardant electrolyte is one of the important methods to improve the safety of lithium metal batteries. Ionic liquids have become promising electrolyte additives due to their non-volatile and non-flammable properties. However, the ionic conductivity of currently disclosed ionic liquids is relatively low, which affects the transport properties of active ions, and then leads to unsatisfactory rate performance of the battery. In this way, it causes uneven deposition of lithium ions on the electrode surface, resulting in the formation of lithium dendrites, affecting the Coulomb efficiency of the battery. Therefore, the application of ionic liquids in electrolytes is limited.

[0077] Based on the above background, in the first aspect of the embodiments of the present application, an ionic liquid is provided, and the ionic liquid includes a cation as shown in Formula I:

[0078]

[0079] Wherein, R0, R1, R2, and R3 each independently include any one of C1-C 10 alkyl, C1-C 10 alkoxy, and C1-C 10 fluoroalkyl; R4 is an unsaturated group containing a double bond.

[0080] The term "alkyl" refers to a saturated hydrocarbon containing primary (normal) carbon atoms, secondary carbon atoms, tertiary carbon atoms, quaternary carbon atoms, or a combination thereof. A phrase containing this term, for example, "C1-C 10 alkyl" refers to an alkyl containing 1 to 10 carbon atoms, and each occurrence can independently be a C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, C7 alkyl, C8 alkyl, C9 alkyl, C10 Alkyl

[0081] The term "alkoxy" refers to the oxy group of alkanes with different carbon chain lengths (i.e., -O-A, where A is an alkyl).

[0082] The term "fluoroalkyl" refers to a group in which a hydrogen atom on an alkyl is substituted by a fluorine atom.

[0083] The term "double bond" refers to the formation of two covalent bonds between two atoms. The double bond can be a carbon-carbon double bond, a carbon-oxygen double bond, a carbon-nitrogen double bond, etc.

[0084] The term "nitrile group" refers to a group formed between a carbon atom and a nitrogen atom, usually represented as -CN.

[0085] The ionic liquid provided by the embodiments of the present application has a pyrrolidine as the main body of the cation, and a nitrile group, a silicon group, an alkyl group, an alkoxy group, a fluoroalkyl group, and an unsaturated group containing a double bond are introduced into the pyrrolidine. Among them, pyrrolidine and R4 containing an unsaturated group have high reducibility resistance and compatibility, so that the ionic liquid remains stable in a reducing environment. The alkyl group, alkoxy group, and fluoroalkyl group can further improve the antioxidant performance of the ionic liquid. After such combination, the reliability of the secondary battery can be significantly improved; the nitrile group can effectively improve the ionic conductivity of the ionic liquid and promote the transmission of lithium ions, thereby improving the Coulomb efficiency and rate performance of the secondary battery; the silicon group with a film-forming tendency combined with R4 can form an interface layer with high toughness, blocking the reaction between the nitrile group and active ions, and significantly improving the cycle life of the secondary battery. Thus, the ionic liquid can make the secondary battery exhibit high cycle performance and reliability.

[0086] The nitrile group introduced into the pyrrolidine main body of the ionic liquid cation has a strong coordination effect with lithium ions, which not only effectively improves the ionic conductivity of the ionic liquid, but also continuously reacts with the negative electrode material such as lithium metal. At this time, the silicon group with a film-forming tendency combined with R4 can form an interface layer with good stability, high density, and strong toughness. This interface layer can effectively block the reaction between the nitrile group and the negative electrode material such as lithium metal, thereby inhibiting the generation of lithium dendrites and dead lithium, and significantly improving the cycle performance and safety of the battery. Since the interaction force between the silicon group, the pyrrolidine main body and lithium ions is slightly weak, the silicon group and the nitrile group are simultaneously introduced into the pyrrolidine main body. In this way, the film-forming effect of the silicon group can be fully exerted, blocking the reaction between the nitrile group and active ions. In addition, the silicon atom in the silicon group has a d orbital, which can form a conjugate with the lone pair electrons of the nitrogen atom in the nitrile group, thereby reducing the nucleophilicity of the nitrogen atom, so that the nitrile group can not only maintain a certain ability to coordinate with lithium ions to achieve high ionic conductivity, but also not react too strongly with lithium metal.

[0087] Generally, due to the relatively negative electrochemical potential of negative electrode materials such as lithium metal electrodes, neutral groups such as alkyl, alkoxy, fluoroalkyl, silicon, etc. are difficult to enter the first Helmholtz layer, which is not conducive to the role of these groups, such as participating in the formation of the SEI film. In the embodiment of the present application, alkyl, alkoxy, fluoroalkyl and silicon are simultaneously introduced into the ionic liquid cationic pyrrolidine main body. Under the action of the ionic liquid, especially the positively charged cations contained therein, these groups can enter the first Helmholtz layer, thereby giving full play to their role, constructing an interface layer with high stability, strong toughness, good density and high inorganic content, further inhibiting the formation of lithium dendrites, so that the secondary battery has high energy density, cycle performance and other electrochemical properties, and good safety.

[0088] The Helmholtz layer refers to the excess charge in the two phases caused by the transfer of charged particles between the two phases or the charging of both sides of the electrode interface through an external circuit when the electrode is in contact with the solution. These excess charges are distributed in the thin layers on both sides of the interface, forming an electrochemical double layer, or double layer for short. The first Helmholtz layer refers to the electrochemical layer close to the electrode side.

[0089] In some embodiments, R0, R1, R2, and R3 independently include any one of a C1-C3 alkyl group, a C1-C3 alkoxy group, and a C1-C3 fluoroalkyl group.

[0090] Alkyl groups, alkoxy groups and fluoroalkyl groups with 1 to 3 carbon atoms can, on the one hand, improve the solubility and stability of ionic liquids, allowing the ionic liquids to remain stable in high temperature environments; on the other hand, they can improve the antioxidant properties of ionic liquids, thereby extending the cycle life of the battery.

[0091] In some embodiments, at least one of R0, R1, R2, and R3 includes a C1-C3 fluoroalkyl group.

[0092] On the one hand, fluoroalkyl groups can improve the antioxidant properties of ionic liquids, thereby increasing the stability of ionic liquids; on the other hand, since fluoroalkyl groups are connected to the main structure of ionic liquid cations, after solvation, fluoroalkyl-containing cations can more easily enter the first Helmholtz layer, which is beneficial for fluoroalkyl groups to participate in the formation of SEI film, increase the content of inorganic compounds such as lithium fluoride in the SEI film, and thus extend the cycle life of the battery.

[0093] In some embodiments, R4 comprises In any one of the above, the wavy line represents the bonding position of R4 to the silicon group in Formula I.

[0094] These R4 groups, on the one hand, have high reducibility resistance and can effectively improve the antioxidant property of the ionic liquid; on the other hand, they have a film-forming effect and combine with the silicon-based groups, which is more conducive to constructing an SEI film with high stability, strong toughness and good compactness, thereby blocking the reaction between the nitrile group and the electrode material. When the volume of the battery changes due to charge-discharge cycling, the SEI film can remain intact, and further inhibit the generation of lithium dendrites and dead lithium. In this way, the battery exhibits high cycle performance and safety. In addition, these groups enable the ionic liquid to have high compatibility with the electrode material, thereby increasing the versatility of the ionic liquid.

[0095] In some embodiments, the ionic liquid includes at least one of the cations shown in Formula I-1 to Formula I-12:

[0096]

[0097]

[0098] In the embodiments of the present application, the ionic liquid cations shown in Formula I-1 to Formula I-12, on the one hand, have high ionic conductivity and can effectively improve the transport performance of the ionic liquid; on the other hand, through the synergistic effect of the nitrile group, silicon-based group, alkyl group, alkoxy group, fluoroalkyl group and unsaturated group containing a double bond, an SEI film with high ionic conductivity, strong toughness, excellent stability and high lithium fluoride content is formed on the surface of the electrode material. And when the volume of the SEI film changes due to charge-discharge cycling, it still remains intact and stable, and further inhibits the generation of lithium dendrites and dead lithium; on the other hand, it can effectively improve the flame retardancy of the secondary battery. In this way, the battery exhibits high cycle performance, high-rate discharge capacity and safety.

[0099] In some embodiments, the anion of the ionic liquid includes at least one of bis(fluorosulfonyl)imide anion, tetrafluoroborate anion, bis(trifluoromethylsulfonyl)imide anion, hexafluorophosphate anion, hexafluoroarsenate anion, trifluoromethanesulfonate anion, difluorophosphate anion, bis(oxalato)borate anion, difluoro(oxalato)borate anion, difluoro-bis(oxalato)phosphate anion and tetrafluoro(oxalato)phosphate anion.

[0100] These anions not only have high conductivity and electrochemical performance, endowing the ionic liquid with high conductivity to increase the cycle life and high-rate capacity of the battery, but also can improve the stability and solubility of the ionic liquid. This stability enables the ionic liquid to be used as a medium for high-temperature or oxidation reactions, such as enabling the ionic liquid to be used as an additive and / or solvent for the electrolyte.

[0101] In some embodiments, the anion of the ionic liquid includes bis(fluorosulfonyl)imide anion.

[0102] The bis(fluorosulfonyl)imide anion has good electrical conductivity and electrochemical properties, so it is used as an electrolyte or electrode active material for batteries to increase the energy density and cycle life of the batteries.

[0103] In some embodiments, a method for preparing an ionic liquid includes the following steps:

[0104] Add the first reactant, the second reactant, the third reactant, and the fourth reactant to an organic solvent, and stir and react at 100-300 °C for 5-8 h. After the reaction is completed, perform reduced-pressure distillation to obtain the ionic liquid provided in the first aspect of the present application.

[0105] In another embodiment, a method for preparing an ionic liquid includes the following steps:

[0106] Add the first reactant, the second reactant, the third reactant, the fourth reactant, and the fifth reactant to an organic solvent, and stir and react at 100-300 °C for 5-8 h. After the reaction is completed, perform reduced-pressure distillation to obtain the ionic liquid provided in the first aspect of the present application.

[0107] Exemplarily, the reaction temperature can be limited but non-limiting values such as 100 °C, 150 °C, 200 °C, 250 °C, 280 °C, 300 °C, etc. The reaction time can be limited but non-limiting values such as 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, etc. The organic solvent includes but is not limited to tetrahydropyran.

[0108] The first reactant refers to an initial ionic liquid, which contains pyrrolidinium cations and anions. Specifically, the cations of the initial ionic liquid can include but are not limited to at least one of them. The anions in the initial ionic liquid can include but are not limited to at least one of bis(fluorosulfonyl)imide anion, tetrafluoroborate anion, bis(trifluoromethylsulfonyl)imide anion, hexafluorophosphate anion, hexafluoroarsenate anion, trifluoromethanesulfonate anion, difluorophosphate anion, bis(oxalato)borate anion, difluoro(oxalato)borate anion, difluoro(dioxalato)phosphate anion, and tetrafluoro(oxalato)phosphate anion.

[0109] The second reactant contains a reaction raw material with a silicon group. Specifically, it can include but is not limited to

[0110] at least one of them.

[0111] The third reactant refers to a reaction raw material containing a nitrile group. Specifically, it can include but is not limited to at least one of them.

[0112] The fourth reactant refers to a reaction raw material containing a double-bond unsaturated group. Specifically, it may include, but is not limited to, at least one of

[0113] The fifth reactant refers to a reaction raw material containing an alkyl group, an alkoxy group, or a fluoroalkyl group. Specifically, it may include, but is not limited to, at least one of CH4.

[0114] The lithium salt refers to a salt corresponding to the anion of the ionic liquid. Specifically, it may include at least one of lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonyl)imide, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium difluoro bis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0115] In a second aspect, the present application provides an application of an ionic liquid as an electrolyte solvent. The ionic liquid includes the ionic liquid provided in the first aspect of the present application.

[0116] The ionic liquid has high ionic conductivity, stability, antioxidant property, and flame retardancy. Therefore, the ionic liquid can be used as an electrolyte solvent to improve the ionic conductivity and stability of the electrolyte.

[0117] In a third aspect, the present application provides an electrolyte including an electrolyte and a solvent. The solvent includes the ionic liquid provided in the first aspect of the present application.

[0118] The electrolyte provided in the embodiments of the present application includes an electrolyte and a solvent. The solvent includes the ionic liquid of the present application. On the one hand, the ionic liquid has high flame retardancy, which is beneficial to improving the safety of the electrolyte, especially the battery. On the other hand, the introduced unsaturated group R4 in the ionic liquid has high reducibility resistance and compatibility, which means that the ionic liquid can maintain stability in a reducing environment, is not prone to chemical changes or reduction, so that the ionic liquid has high stability and versatility. Combining alkyl, alkoxy, and fluoroalkyl groups can further improve the antioxidant property of the ionic liquid. In this way, the reliability of the secondary battery can be significantly improved. On the other hand, the introduced nitrile group in the ionic liquid can effectively improve the ionic conductivity of the ionic liquid, promote the transport of lithium ions, and thus improve the Coulomb efficiency and rate performance of the secondary battery. On the other hand, the silicon group with a film-forming tendency combined with R4 can form a high-toughness interfacial layer to block the reaction between the nitrile group and active ions, playing an obvious role in improving the cycle life of the secondary battery. In this way, the electrolyte can make the secondary battery exhibit high cycle performance and reliability. In addition, the ionic liquid has excellent solubility in the electrolyte, thus forming an electrolyte without separation phenomenon, making the transport of active ions smoother and obtaining a highly stable electrolyte.

[0119] In some embodiments, the electrolyte includes a lithium salt. Specifically, it may include at least one of lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(trifluoromethylsulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium difluoro bis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0120] These electrolytes have high solubility in ionic liquids. On the one hand, it is beneficial to the conductivity of the electrolyte, promotes the transport of active ions, and enables the electrolyte solution to exhibit a high active ion mobility; on the other hand, it prevents obvious chemical reactions or phase separation between the electrolyte and the ionic liquid, thereby maintaining the stability of the electrolyte solution.

[0121] In some embodiments, the electrolyte includes lithium bis(fluorosulfonyl)imide.

[0122] Lithium bis(fluorosulfonyl)imide has high conductivity, a wide liquid range, and excellent lithium ion transference number, enabling the electrolyte solution to have high conductivity, stability, and lithium ion transport rate, thus being beneficial to improving the rate performance and cycle performance of the battery.

[0123] In some embodiments, the concentration of the electrolyte is 0.5 mol / L to 4 mol / L. Exemplarily, the concentration of the electrolyte includes but is not limited to any one of the point values of 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 or the range values between any two of them.

[0124] In some embodiments, the concentration of the electrolyte is 2 mol / L.

[0125] Within this concentration range, the electrolyte enables the electrolyte solution to have high conductivity and stability, promotes the migration and transport of active ions, and thus enables the battery to exhibit high capacity and cycle stability.

[0126] In some embodiments, the solvent further includes a co-solvent, and the co-solvent includes at least one of benzene solvents, fluorinated hydrocarbon solvents, and ether solvents. These co-solvents cannot dissolve the electrolyte but have good compatibility with the ionic liquid. Thus, on the basis of improving the viscosity of the electrolyte solution, it does not affect the solvation process of the electrolyte. In particular, the co-solvent can adjust the solvation structure of the electrolyte solution and does not enter the first solvation layer of lithium ions, which plays a promoting role in constructing an interfacial layer with strong toughness, excellent stability, and good compactness.

[0127] In some embodiments, the volume ratio of the ionic liquid to the co-solvent is 1:9 to 9:1.

[0128] The co-solvent, on the one hand, can effectively reduce the viscosity of the electrolyte, thereby promoting the transport of active ions and enabling the battery to have a high capacity; on the other hand, it does not participate in the electrode reaction, especially does not enter the first solvation layer of lithium ions, and can also adjust the solvation structure of the electrolyte, promote the reaction between the ionic liquid and the electrode material, and form a dense and stable interfacial layer on the surface of the electrode material, thereby inhibiting the formation of lithium dendrites and dead lithium and improving the cycle life and safety of the battery.

[0129] In some embodiments, the volume ratio of the ionic liquid to the co-solvent is 4:6.

[0130] In the embodiments of the present application, controlling the volume ratio of the ionic liquid to the co-solvent within the above range can not only effectively improve the viscosity of the electrolyte, thereby facilitating the increase of the transport rate of active ions in the electrolyte, but also adjust the solvation structure formed by the electrolyte, thereby forming a dense, stable and flexible interfacial layer on the surface of the electrode material, and when the volume of the interfacial layer changes due to charge and discharge cycles, it still remains intact and stable, thereby inhibiting the generation of lithium dendrites and dead lithium.

[0131] In some embodiments, the benzene solvent includes at least one of cyclohexane, benzene, toluene, p-xylene, m-xylene, o-xylene, fluorobenzene, p-difluorobenzene, m-difluorobenzene, o-difluorobenzene, benzotrifluoride, trifluoromethoxybenzene.

[0132] In some embodiments, the fluorinated hydrocarbon solvent includes decafluoropentane, perfluoropentanone, 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane.

[0133] In some embodiments, the ether solvent includes at least one of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl) ether, 1,1,2,3,3,3-hexafluoropropyl ethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-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.

[0134] These co-solvents not only have high stability, but also have excellent compatibility with the ionic liquid. Thus, the viscosity of the electrolyte can be effectively improved and the transport of active ions can be promoted.

[0135] Those raw materials not specifically described above can all be obtained through commercial purchase.

[0136] Fourthly, an embodiment of the present application provides a battery cell, including an electrolyte solution, which is the electrolyte solution provided above in the present application.

[0137] Generally, the battery cell further includes a positive electrode plate, a negative electrode plate, and a separator. During the charging and discharging process of the battery, active ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte solution plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The separator is disposed between the positive electrode plate and the negative electrode plate, mainly to prevent short circuit between the positive and negative electrodes, and at the same time allows ions to pass through.

[0138] [Positive electrode plate]

[0139] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0140] Exemplarily, the positive electrode current collector has two surfaces opposite to each other in its own 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.

[0141] In some embodiments, the positive electrode current collector can be made of a metal foil or a composite current collector with good electrical conductivity and mechanical properties. For example, as a metal foil, aluminum foil can be used. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material on the polymer material substrate. Among them, the metal material includes at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. The polymer material substrate includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0142] In some embodiments, the positive electrode active material may include positive electrode active materials well-known in the art for batteries.

[0143] Exemplarily, the positive electrode active material may include at least one of the following materials: layered transition metal oxides, transition metal oxides with a spinel structure, olivine structure polyanion compounds, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as the positive electrode active material of the battery can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, examples of the layered transition metal oxide may include, but are not limited to, single-layered compounds and multi-layered compounds. Examples of the single-layered compound may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), and examples of the multi-layered compound may include, but are not limited to, LiCo x Ni y Mn 1-x-y O2 and lithium-rich manganese-based positive electrode material Li x (Ni,Mn,Co)O2 (x > 1). Examples of the transition metal oxide with a spinel structure include, but are not limited to, lithium manganese compounds (LiMn2O4, Li2Mn4O9, Li4Mn5O 12 ), vanadium lithium compounds (LiV2O4), iron lithium compounds (LiFe5O8), titanium lithium compounds (Li4Ti5O 12 ), and cobalt nickel lithium compounds (Li2Co 2-2y Ni 2y O4, 0 ≤ y ≤ 0.1) and at least one of their modified compounds. Examples of the olivine structure polyanion compound may include, but are not limited to, lithium iron phosphate (such as LiFePO4, LiFeP2O7, Li3Fe2(PO4)3, LiFe4(P2O7)3), composites of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), composites of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and composites of lithium manganese iron phosphate and carbon.

[0144] In some embodiments, based on the total weight of the positive electrode film layer, the mass ratio of the positive electrode active material in the positive electrode film layer is 80 to 100%.

[0145] In some embodiments, the positive electrode film layer may optionally further include a binder. As an example, the binder includes, but is not limited to, at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin. Based on the total weight of the positive electrode film layer, the mass ratio of the binder in the positive electrode film layer is 0 to 20%.

[0146] In some embodiments, the positive electrode film layer may further optionally include a conductive agent. As an example, the conductive agent includes but is not limited to at least one of superconducting carbon, carbon black (such as acetylene black or Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Based on the total weight of the positive electrode film layer, the mass ratio of the conductive agent in the positive electrode film layer is 0 to 20%.

[0147] In some embodiments, the positive electrode plate can be prepared in the following manner: Dispersing the components for preparing the positive electrode plate described above, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry, where the solid content of the positive electrode slurry is 40 to 80 wt%, and the viscosity at room temperature is adjusted to 5000 - 25000 mPa·s. Coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode plate can be obtained.

[0148] [Negative electrode plate]

[0149] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

[0150] Exemplarily, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on either or both of the two opposite surfaces of the negative electrode current collector.

[0151] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. The metal foil can be a copper foil. The composite current collector can be a polymer material matrix material and a metal layer formed on at least one surface of the polymer matrix material. The composite current collector can be formed on the surface of the polymer material matrix material by copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, and the polymer matrix material such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0152] In some embodiments, the negative electrode active material can be a negative electrode active material for a battery well-known in the art. As an example, the negative electrode active material can include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0153] In some embodiments, based on the total weight of the negative electrode film layer, the mass ratio of the negative electrode active material in the negative electrode film layer is 70 to 100%.

[0154] In some embodiments, the negative electrode film layer may further optionally include a binder. As an example, the binder may include but is not limited to at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). Based on the total weight of the negative electrode film layer, the mass ratio of the binder in the negative electrode film layer is 0 to 30%.

[0155] In some embodiments, the negative electrode film layer may further optionally include a conductive agent. As an example, the conductive agent may include but is not limited to at least one of superconducting carbon, carbon black (such as acetylene black or Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Based on the total weight of the negative electrode film layer, the mass ratio of the conductive agent in the negative electrode film layer is 0 to 20%.

[0156] In some embodiments, the negative electrode film layer may further optionally include other additives, such as a thickening agent (such as sodium carboxymethyl cellulose (CMC-Na)).

[0157] In some embodiments, the negative electrode plate can be prepared in the following manner: dispersing the components for preparing the negative electrode plate, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (such as deionized water) to form a negative electrode slurry, wherein the solid content of the negative electrode slurry is 30 to 80 wt%, and the viscosity at room temperature is adjusted to 2000 - 10000 mPa·s; coating the obtained negative electrode slurry on the negative electrode current collector, and through a drying process, cold pressing, such as roll pressing, to obtain the negative electrode plate.

[0158] In some embodiments, the negative electrode plate may not include a negative electrode active material capable of intercalating and deintercalating lithium ions. For example, the negative electrode plate may include a lithium sheet or a lithium alloy sheet; or, the negative electrode plate may include a three-dimensional skeleton layer in a mesh or foam shape; or, the negative electrode plate may include a negative electrode current collector and a lithium-containing layer provided on at least one surface of the negative electrode current collector. As an example, the lithium alloy sheet is an alloy formed by metallic lithium and various other metal or non-metal elements, wherein the metal elements include but are not limited to at least one of tin (Sn), zinc (Zn), aluminum (Al), magnesium (Mg), silver (Ag), gold (Au), gallium (Ga), indium (In), and platinum (Pt), and the non-metal elements include but are not limited to at least one of boron (B), carbon (C), and silicon (Si).

[0159] [Separator membrane]

[0160] In some embodiments, the material of the separator membrane may include, but is not limited to, at least one of polyolefins, polyamides, polysulfones, polyethersulfones, and porous membranes formed by various polymers. The separator membrane can be a single-layer thin film or a multi-layer composite thin film, without particular limitation. When the separator membrane is a multi-layer composite thin film, the materials of each layer can be the same or different, without particular limitation.

[0161] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator membrane can be made into an electrode assembly through a winding process or a stacking process. The electrode assembly is placed in an outer package, dried, and then electrolyte is injected. After vacuum packaging, standing, forming, shaping and other processes, a battery cell is obtained. The shape of the battery cell has no particular limitation, and it can be cylindrical, square or any other shape.

[0162] In some embodiments, the outer package of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic. As plastics, polypropylene, polybutylene terephthalate, and polybutylene succinate can be listed, etc.

[0163] In a fifth aspect, an embodiment of the present application provides a battery, which includes at least one of the above-mentioned battery cells. Generally, it includes a plurality of battery cells, and the plurality of battery cells are connected in series, in parallel or in a hybrid connection to increase the power supply capacity of the battery. In some cases, the battery further includes a box body, and the battery cells are accommodated in the box body.

[0164] Therefore, in the embodiment, the battery can include any one of a battery cell, a battery module, and a battery pack.

[0165] In some embodiments, when the battery in the embodiment of the present application is a battery module, the battery module contains a plurality of the above-mentioned battery cells, and the plurality of battery cells can be arranged in sequence along the length direction of the battery module. Of course, they can also be arranged in any other way. Further, the plurality of battery cells can be fixed by fasteners.

[0166] In some embodiments, the battery module can further include a housing having an accommodation space, and the plurality of battery cells are accommodated in the accommodation space.

[0167] In some embodiments, when the battery in the embodiment of the present application is a battery pack, the battery pack can contain a plurality of the above-mentioned battery cells, and the plurality of battery cells can be assembled into the above-mentioned battery module. Therefore, the specific number of battery cells or battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0168] In an embodiment, a battery pack may include a battery box and a plurality of battery modules disposed in the battery box. The battery box includes an upper box body and a lower box body. The upper box body is used to cover the lower box body and form a closed space for accommodating the battery modules. The plurality of battery modules may be arranged in the battery box in any manner.

[0169] In a sixth aspect, an embodiment of the present application provides an electrical device including the battery of the embodiment of the present application. The battery in the embodiment of the present application can be used as a power source of the electrical device or as an energy storage unit of the electrical device. Therefore, the electrical device in the embodiment of the present application has a long standby or endurance time and good safety performance.

[0170] The battery disclosed in some embodiments of the present application can be but is not limited to being used in electrical devices such as vehicles, ships, or aircraft. A power supply system of the electrical device can be composed of the battery disclosed in the present application.

[0171] Some embodiments of the present application provide an electrical device using a battery as a power source. The electrical device can be but is not limited to vehicles, mobile phones, portable devices, laptop computers, ships, spacecraft, electric toys, and electric tools, etc. The vehicle can be but is not limited to a fuel vehicle, a gas vehicle, or a new energy vehicle. The new energy vehicle can be but is not limited to a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle, etc.; the spacecraft includes airplanes, rockets, space shuttles, and spaceships, etc.; the electric toys include fixed or mobile electric toys, for example, game consoles, electric vehicle toys, electric ship toys, and electric airplane toys, etc.; the electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, for example, electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact electric drills, concrete vibrators, and electric planers, etc.

[0172] For the convenience of description in the following embodiments, a vehicle as an electrical device according to an embodiment of the present application is taken as an example for description.

[0173] Please refer to Figure 1 , Figure 1 , which is a schematic structural diagram of a vehicle provided by some embodiments of the present application. The vehicle 1000 can be a fuel vehicle, a gas vehicle, or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle, etc. A lithium-ion battery 100 is disposed inside the vehicle 1000. The lithium-ion battery 100 can be disposed at the bottom, head, or tail of the vehicle 1000. The lithium-ion battery 100 can be used for power supply of the vehicle 1000. For example, the lithium-ion battery 100 can be used as an operating power source of the vehicle 1000. The vehicle 1000 may further include a controller 200 and a motor 300. The controller 200 is used to control the lithium-ion battery 100 to supply power to the motor 300. For example, it is used for the working power requirements during the start, navigation, and driving of the vehicle 1000.

[0174] In some embodiments of the present application, the lithium-ion battery 100 is a secondary battery, and secondary batteries have various different forms, including but not limited to battery cells, battery modules, battery packs, etc. Here, the secondary battery refers to a battery that can activate the active substances through charging after discharging and continue to be used.

[0175] Please refer to Figure 2 , Figure 2 , which is an exploded view of the lithium-ion battery 100 provided in some embodiments of the present application. The lithium-ion battery 100 includes a box body 10 and lithium-ion battery cells 20, and the lithium-ion battery cells 20 are accommodated in the box body 10. Among them, the box body 10 is used to provide a accommodating space for the lithium-ion battery cells 20, and the box body 10 can adopt various structures. In some embodiments, the box body 10 may include an upper box body 11 and a lower box body 12, the upper box body 11 and the lower box body 12 are covered with each other, and the upper box body 11 and the lower box body 12 jointly define a closed space for accommodating the lithium-ion battery cells 20. Of course, the box body 10 formed by the upper box body 11 and the lower box body 12 can be of various shapes, such as a cylinder, a cuboid, etc. Multiple battery cells 20 can be arranged in the battery box in any manner.

[0176] In the lithium-ion battery 100, there may be multiple lithium-ion battery cells 20, and the multiple lithium-ion battery cells 20 can be connected in series, in parallel, or in a series-parallel combination. The series-parallel combination means that there are both series and parallel connections among the multiple lithium-ion battery cells 20. The multiple lithium-ion battery cells 20 can be directly connected in series, in parallel, or in a series-parallel combination together, and then the whole formed by the multiple lithium-ion battery cells 20 is accommodated in the box body 10; of course, the lithium-ion battery 100 can also be in the form that multiple lithium-ion battery cells 20 are first connected in series, in parallel, or in a series-parallel combination to form lithium-ion battery modules, and then the multiple lithium-ion battery modules are connected in series, in parallel, or in a series-parallel combination to form a whole and are accommodated in the box body 10.

[0177] Please refer to Figure 3 , Figure 3 , which is an exploded view of the battery cell 20 in some embodiments of the present application. The battery cell 20 includes a housing 21, a cover plate 23, an electrode assembly 22, and other functional components.

[0178] The housing 21 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose an accommodation cavity. The housing 21 has an opening communicating with the accommodation cavity, and the cover plate 23 can be covered on the opening to close the accommodation cavity. The positive electrode plate, the negative electrode plate, and the separator can be formed into the electrode assembly 22 through a winding process or a stacking process. The electrode assembly 22 is encapsulated in the accommodation cavity. The electrolyte is infiltrated in the electrode assembly 22. The number of electrode assemblies 22 included in the battery cell 20 can be one or more, and those skilled in the art can select according to specific actual needs.

[0179] Example

[0180] The following describes the embodiments of the present application. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application. For those specific technologies or conditions not specified in the embodiments, they shall be carried out according to the technologies or conditions described in the literature in this field or according to the product specifications. For the reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase.

[0181] Example 1

[0182] This example provides an ionic liquid, an electrolyte solution and a battery cell.

[0183] Ionic liquid:

[0184] An ionic liquid, wherein the structural formula of the cation is shown in Formula I-12, and the anion is a bis(fluorosulfonyl)imide anion.

[0185]

[0186] A preparation method of an ionic liquid includes the following steps:

[0187] Mix the reaction raw materials, the initial ionic liquid (the cation is and the anion is a bis(fluorosulfonyl)imide anion), in a ratio of 1:1:1:1 by molar ratio, add them to tetrahydropyran, stir and react at 200 °C for 5 h, and after the reaction is completed, perform reduced-pressure distillation to obtain the ionic liquid.

[0188] Electrolyte solution:

[0189] An electrolyte solution includes an electrolyte and an ionic liquid; wherein, the electrolyte is lithium bis(fluorosulfonyl)imide, the structural formula of the cation of the ionic liquid is shown in Formula I-12, and the anion is a bis(fluorosulfonyl)imide anion; the concentration of the electrolyte is 2 mol / L.

[0190]

[0191] The preparation method of the above electrolyte solution includes the following steps:

[0192] Add 0.374 g of the electrolyte to 1 mL of the above ionic liquid, stir well to form a colorless and transparent electrolyte solution.

[0193] Battery cell:

[0194] [Electrolyte solution]

[0195] That is, the above electrolyte solution of Example 1 of the present application.

[0196] [Preparation of negative electrode sheet]

[0197] A 50-μm lithium foil was laminated onto a 12-μm copper foil by rolling, and then cut into a negative electrode sheet with a size of 41 mm × 51 mm.

[0198] [Preparation of Positive Electrode Sheet]

[0199] The positive electrode active material lithium nickel cobalt manganese oxide (NCM811), the conductive agent acetylene black, and the binder PVDF (polyvinylidene fluoride) were mixed in a mass ratio of 98:1:1, and the solvent NMP (N-methylpyrrolidone) was added and stirred until the system became homogeneous to obtain a positive electrode slurry (solid content: 70%); the positive electrode slurry was uniformly double-sided coated on the positive electrode current collector aluminum foil at a loading amount of 25 mg / cm 2 , air-dried at room temperature, then transferred to an oven for further drying, and then cut into a positive electrode sheet with a size of 40 mm × 50 mm.

[0200] [Separator Membrane]

[0201] Separator membrane: polyethylene porous membrane, size: 45 mm × 55 mm.

[0202] Preparation of battery cell: The above positive electrode sheet, separator membrane, and negative electrode sheet were stacked in sequence, with the separator membrane placed between the positive and negative electrode sheets, and wrapped in an aluminum-plastic film bag to form a stacked dry battery core. 0.3 g of the above electrolyte was injected, and the aluminum-plastic film bag was vacuum heat-pressed and sealed.

[0203] Example 2

[0204] This example provides an ionic liquid, an electrolyte, and a battery cell. The difference from Example 1 is that the electrolyte includes an electrolyte and a solvent. The electrolyte is lithium bis(fluorosulfonyl)imide salt, and the solvent includes an ionic liquid and an auxiliary solvent with a volume ratio of 1:9. The structural formula of the cation of the ionic liquid is shown in Formula I-1, the anion is bis(fluorosulfonyl)imide anion, and the auxiliary solvent is 1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether; the concentration of the electrolyte is 2 mol / L; other conditions are the same as in Example 1.

[0205]

[0206] The preparation method of the ionic liquid is different from that in Example 1 in that the reaction raw materials are the initial ionic liquid (cation is anion is bis(fluorosulfonyl)imide anion) with a mass ratio of 1:1:1:1,

[0207]

[0208] Example 3

[0209] This embodiment provides an ionic liquid, an electrolyte, and a battery cell. The difference from Embodiment 2 is that the volume ratio of the ionic liquid to the auxiliary solvent is 1:2, and the others are the same as in Embodiment 2.

[0210] Embodiment 4

[0211] This embodiment provides an ionic liquid, an electrolyte, and a battery cell. The difference from Embodiment 2 is that the volume ratio of the ionic liquid to the auxiliary solvent is 4:6, and the others are the same as in Embodiment 2.

[0212] Embodiment 5

[0213] This embodiment provides an ionic liquid, an electrolyte, and a battery cell. The difference from Embodiment 2 is that the volume ratio of the ionic liquid to the auxiliary solvent is 1:1, and the others are the same as in Embodiment 2.

[0214] Embodiment 6

[0215] This embodiment provides an ionic liquid, an electrolyte, and a battery cell. The difference from Embodiment 2 is that the volume ratio of the ionic liquid to the auxiliary solvent is 7:3, and the others are the same as in Embodiment 2.

[0216] Embodiment 7

[0217] This embodiment provides an ionic liquid, an electrolyte, and a battery cell. The difference from Embodiment 2 is that the volume ratio of the ionic liquid to the auxiliary solvent is 9:1, and the others are the same as in Embodiment 2.

[0218] Embodiment 8

[0219] This embodiment provides an ionic liquid, an electrolyte, and a battery cell. The difference from Embodiment 4 is that the cation structure formula of the ionic liquid is as shown in Formula I-2, and the others are the same as in Embodiment 4.

[0220]

[0221] The preparation method of the ionic liquid, different from that in Embodiment 1, is that the reaction raw materials are the initial ionic liquid (cation is anion is bis(fluorosulfonyl)imide anion) with a mass ratio of 1:1:1:1:1,

[0222]

[0223] Embodiment 9

[0224] This embodiment provides an ionic liquid, an electrolyte, and a battery cell. The difference from Embodiment 4 is that the cation structure formula of the ionic liquid is as shown in Formula I-3, and the others are the same as in Embodiment 4.

[0225]

[0226] The preparation method of the ionic liquid is different from that of Example 1 in that the reaction raw materials are initial ionic liquids with a mass ratio of 1:1:1:1:1 (the cation is and the anion is bis(fluorosulfonyl)imide anion),

[0227]

[0228] Example 10

[0229] This example provides an ionic liquid, an electrolyte and a battery cell. The difference from Example 4 is that the structural formula of the cation in the ionic liquid is as shown in Formula I-4, and the others are the same as in Example 4.

[0230]

[0231] The preparation method of the ionic liquid is different from that of Example 1 in that the reaction raw materials are initial ionic liquids with a mass ratio of 1:1:1:1:1 (the cation is and the anion is bis(fluorosulfonyl)imide anion),

[0232]

[0233] Example 11

[0234] This example provides an ionic liquid, an electrolyte and a battery cell. The difference from Example 4 is that the structural formula of the cation in the ionic liquid is as shown in Formula I-5, and the others are the same as in Example 4.

[0235]

[0236] The preparation method of the ionic liquid is different from that of Example 1 in that the reaction raw materials are initial ionic liquids with a mass ratio of 1:1:1:1:1 (the cation is and the anion is bis(fluorosulfonyl)imide anion),

[0237] Example 12

[0238] This example provides an ionic liquid, an electrolyte and a battery cell. The difference from Example 4 is that the structural formula of the cation in the ionic liquid is as shown in Formula I-6, and the others are the same as in Example 4.

[0239]

[0240] The preparation method of the ionic liquid is different from that of Example 1 in that the reaction raw materials are initial ionic liquids with a mass ratio of 1:1:1:1:1 (the cation is and the anion is bis(fluorosulfonyl)imide anion),

[0241] Example 13

[0242] This embodiment provides an ionic liquid, an electrolyte, and a battery cell. The difference from Embodiment 4 is that the structural formula of the cation in the ionic liquid is as shown in Formula I-7, and the others are the same as in Embodiment 4.

[0243]

[0244] The preparation method of the ionic liquid is different from that of Embodiment 1 in that the reaction raw materials are an initial ionic liquid (cation is anion is bis(fluorosulfonyl)imide anion), and methane.

[0245] Embodiment 14

[0246] This embodiment provides an ionic liquid, an electrolyte, and a battery cell. The difference from Embodiment 4 is that the structural formula of the cation in the ionic liquid is as shown in Formula I-8, and the others are the same as in Embodiment 4.

[0247]

[0248] The preparation method of the ionic liquid is different from that of Embodiment 1 in that the reaction raw materials are an initial ionic liquid (cation is anion is bis(fluorosulfonyl)imide anion),

[0249]

[0250] Embodiment 15

[0251] This embodiment provides an ionic liquid, an electrolyte, and a battery cell. The difference from Embodiment 4 is that the structural formula of the cation in the ionic liquid is as shown in Formula I-9, and the others are the same as in Embodiment 4.

[0252]

[0253] The preparation method of the ionic liquid is different from that of Embodiment 1 in that the reaction raw materials are an initial ionic liquid (cation is anion is bis(fluorosulfonyl)imide anion),

[0254]

[0255] Embodiment 16

[0256] This embodiment provides an ionic liquid, an electrolyte, and a battery cell. The difference from Embodiment 4 is that the structural formula of the cation in the ionic liquid is as shown in Formula I-10, and the others are the same as in Embodiment 4.

[0257]

[0258] The preparation method of the ionic liquid is different from that of Example 1 in that the reaction raw materials are the initial ionic liquids with a mass ratio of 1:1:1:1 (the cation is and the anion is bis(fluorosulfonyl)imide anion),

[0259]

[0260] Example 17

[0261] This example provides an ionic liquid, an electrolyte and a battery cell. The difference from Example 4 is that the structural formula of the cation in the ionic liquid is as shown in Formula I-11, and the others are the same as in Example 4.

[0262]

[0263] The preparation method of the ionic liquid is different from that of Example 1 in that the reaction raw materials are the initial ionic liquids with a mass ratio of 1:1:1:1 (the cation is and the anion is bis(fluorosulfonyl)imide anion),

[0264]

[0265] Example 18

[0266] This example provides an ionic liquid, an electrolyte and a battery cell. The difference from Example 4 is that the structural formula of the cation in the ionic liquid is as shown in Formula I-12, and the others are the same as in Example 4.

[0267]

[0268] Example 19

[0269] This example provides an ionic liquid, an electrolyte and a battery cell. The difference from Example 4 is that the bis(fluorosulfonyl)imide anion in the ionic liquid is replaced by a hexafluorophosphate anion, and the lithium bis(fluorosulfonyl)imide salt in the electrolyte is replaced by lithium hexafluorophosphate, and the others are the same as in Example 4.

[0270] Example 20

[0271] This example provides an ionic liquid, an electrolyte and a battery cell. The difference from Example 4 is that the bis(fluorosulfonyl)imide anion in the ionic liquid is replaced by a hexafluoroarsenate anion, and the lithium bis(fluorosulfonyl)imide salt in the electrolyte is replaced by lithium hexafluoroarsenate, and the others are the same as in Example 4.

[0272] Example 21

[0273] This embodiment provides an ionic liquid, an electrolyte solution and a battery cell. The difference from Example 4 is that the anion bis(fluorosulfonyl)imide anion in the ionic liquid is replaced by the difluoro(oxalato)phosphate anion, and the lithium bis(fluorosulfonyl)imide salt in the electrolyte is replaced by lithium difluoro(oxalato)phosphate, and the rest is the same as Example 4.

[0274] Example 22

[0275] This embodiment provides an ionic liquid, an electrolyte solution and a battery cell. The difference from Example 4 is that the co-solvent 1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether is replaced by 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane, and the rest is the same as Example 4.

[0276] Example 23

[0277] This embodiment provides an ionic liquid, an electrolyte solution and a battery cell. The difference from Example 4 is that the co-solvent 1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether is replaced by trifluoromethoxybenzene, and the rest is the same as Example 4.

[0278] Comparative Example 1

[0279] This comparative example provides an electrolyte solution and a battery cell. The difference from Example 4 is that the solvent is replaced by ethylene glycol dimethyl ether, and the rest is the same as Example 4.

[0280] Comparative Example 2

[0281] This comparative example provides an electrolyte solution and a battery cell. The difference from Example 4 is that the ionic liquid in the solvent is replaced by ethylene glycol dimethyl ether, and the rest is the same as Example 4.

[0282] Comparative Example 3

[0283] This comparative example provides an ionic liquid, an electrolyte solution and a battery cell. The difference from Example 4 is that the cation of the ionic liquid shown in I-1 in the solvent is replaced by the cation PY13.

[0284]

[0285] Performance detection

[0286] (1) Ionic conductivity

[0287] Test method for ionic conductivity of ionic liquid:

[0288] Apply an electrochemical workstation to apply a sinusoidal current in the electrode system, record the signal generated by the electrode in response to this current, and obtain the impedance spectra generated by a series of sinusoidal signals with different frequencies. According to the electrochemical impedance spectroscopy (EIS), the internal resistance value Z is obtained, and then the ionic conductivity S = L / (Z·A) is calculated, where L is the distance between the two electrodes, and A is the electrode area.

[0289] (2) Full cell testing

[0290] The test process for cycle life is as follows: Take the above-prepared laminated battery cells, set the ambient temperature to 25°C, and perform charge-discharge cycles at a charge rate of 0.2C (i.e., 28 mA) and a discharge rate of 1C (i.e., 140 mA). The cut-off voltages for charge and discharge are set to 4.3V and 2.8V respectively, and the constant current-constant voltage charging method is used during the charging process. Specifically, after the constant current charging at 0.2C reaches the cut-off voltage of 4.3V, continue to use constant voltage charging at 4.3V until the current decays to 0.1C (i.e., 14 mA). When the discharge capacity decays to 80% of the discharge capacity in the first cycle, the battery life is considered to be over.

[0291] The test process for rate discharge is as follows: Take the above-prepared laminated battery cells, set the ambient temperature to 25°C, and perform charge-discharge cycles at a charge rate of 0.2C (i.e., 28 mA) and a discharge rate of 4C (i.e., 560 mA). The cut-off voltages for charge and discharge are set to 4.3V and 2.8V respectively, and the constant current-constant voltage charging method is used during the charging process. Specifically, after the constant current charging at 0.2C reaches the cut-off voltage of 4.3V, continue to use constant voltage charging at 4.3V until the current decays to 0.1C (i.e., 14 mA). When the discharge capacity decays to 80% of the discharge capacity in the first cycle, the battery life is considered to be over.

[0292] (3) Flash point

[0293] The flash point of the electrolyte is an important indicator to measure its flammability. The lower the flash point, the higher the flammability of the electrolyte, increasing the risk of battery combustion or even explosion. Therefore, increasing the flash point of the electrolyte can, to a certain extent, enhance the flame retardancy of the battery, thereby increasing the reliability of the battery cell.

[0294] The flash point is measured using a flash point tester. The measurement range of the flash point tester is 0 - 100°C, which can meet the requirements for testing the flash point of the electrolyte. After testing, the flash points of the electrolytes provided in the examples of this application are all higher than 100°C. Although specific values cannot be provided, it can be confirmed that the electrolytes have high flame retardancy.

[0295] The performance test results of the battery cells prepared in Examples 1 - 23 and the battery cells provided in Comparative Examples 1 - 3 are listed in Table 1 below.

[0296] Table 1 Performance test results

[0297]

[0298]

[0299]

[0300] It can be seen from Table 1 that the ionic conductivity of the electrolyte provided by the embodiment of the present application is significantly better than the ionic conductivity of Comparative Example 3. This is because the ionic liquid cation of the present application simultaneously introduces silicon groups, nitrile groups, fluoroalkyl groups, alkoxy groups, carbon-carbon double bonds and carbonyl groups on the pyrrolidine main body, which can effectively improve the ionic conductivity of the ionic liquid.

[0301] As can be seen from Table 1, the ionic liquid used as the main component of the solvent in Examples 1 to 23 improves the cycle performance, high-rate discharge capacity and flame retardant performance of the battery monomer to varying degrees. Specifically, in combination with Example 1 and Example 12, the ionic liquid and the auxiliary solvent are compounded as the solvent of the electrolyte. The auxiliary solvent can reduce the viscosity of the electrolyte and adjust the solvation structure, thereby further improving the cycle life and high-rate discharge capacity of the battery monomer.

[0302] From the comparison of Example 4 and Comparative Example 1 in Table 1, it can be seen that compared with the use of ethylene glycol dimethyl ether, the addition of ionic liquid and auxiliary solvent as a solvent in the electrolyte can improve the cycle life, high-rate discharge capacity and flame retardancy of the battery monomer. This is because the ionic liquid and the auxiliary solvent play a synergistic role in forming an SEI film with high ionic conductivity, strong toughness, excellent stability and high lithium fluoride content on the surface of the electrode material, thereby inhibiting the generation of lithium dendrites and dead lithium, so that the battery monomer has a higher cycle life, discharge capacity and flame retardancy.

[0303] From the comparison of Example 4 and Comparative Example 2 in Table 1, it can be seen that compared with the use of ethylene glycol dimethyl ether and 1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, the use of ionic liquid and auxiliary solvent as solvent in the electrolyte can improve the cycle life and high-rate discharge capacity of the battery monomer. This is because the ionic liquid fully exerts the synergistic effect through the nitrile group, silicon group, alkyl group, alkoxy group, fluoroalkyl group and unsaturated group containing double bonds to form a stable interface layer on the surface of the electrode material.

[0304] From the comparison between Example 4 and Comparative Example 3 in Table 1, it can be seen that the introduction of silicon group, nitrile group, fluoroalkyl group, alkoxy group, carbon-carbon double bond and carbonyl group on the pyrrolidine main body in the cation represented by Formula I-1 can improve the active ion conductivity, stability, film-forming property, flame retardancy and solvation structure of the electrolyte, thereby improving the electrochemical properties of the battery monomer including cycle life, high-rate discharge capacity and safety performance.

[0305] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present application, and they should all be covered by the scope of the claims and the description of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions that fall within the scope of the claims.

Claims

1. An ionic liquid, characterized in that, The ionic liquid includes a cation shown in Formula I: Among them, R0, R1, R2, and R3 each independently include any one of C1-C 10 alkyl groups, C1-C 10 alkoxy groups, C1-C 10 fluoroalkyl groups; R4 is an unsaturated group containing a double bond.

2. The ionic liquid according to claim 1, characterized in that, The R0, R1, R2, and R3 each independently include any one of C1-C3 alkyl groups, C1-C3 alkoxy groups, and C1-C3 fluoroalkyl groups.

3. The ionic liquid according to claim 2, wherein At least one of the R0, R1, R2, and R3 includes a C1-C3 fluoroalkyl group.

4. The ionic liquid according to any one of claims 1 to 3, characterized in that, The R4 includes any one of them, and the wavy line indicates the bonding position of R4 with the silicon group in Formula I.

5. The ionic liquid according to any one of claims 1 to 4, characterized in that, The ionic liquid includes at least one of the cations shown in Formula I-1 to Formula I-12:

6. The ionic liquid according to any one of claims 1 to 5, characterized in that, The anion of the ionic liquid includes at least one of bis(fluorosulfonyl)imide anion, tetrafluoroborate anion, bis(trifluoromethylsulfonyl)imide anion, hexafluorophosphate anion, hexafluoroarsenate anion, trifluoromethanesulfonate anion, difluorophosphate anion, bis(oxalato)borate anion, difluoro(oxalato)borate anion, difluoro bis(oxalato)phosphate anion, and tetrafluoro(oxalato)phosphate anion.

7. The ionic liquid according to claim 6, wherein The anion of the ionic liquid includes bis(fluorosulfonyl)imide anion.

8. Use of the ionic liquid according to any one of claims 1 to 7 as an electrolyte solvent.

9. An electrolyte, characterized in that, It includes an electrolyte and a solvent, and the solvent includes the ionic liquid according to any one of claims 1 to 7.

10. The electrolyte according to claim 9, characterized in that, The electrolyte includes a lithium salt; and / or The concentration of the electrolyte is 0.5 mol / L to 4 mol / L.

11. The electrolyte according to claim 9 or 10, characterized in that, The electrolyte includes at least one of lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(trifluoromethylsulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium difluoro bis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

12. The electrolyte according to any one of claims 9 to 11, characterized in that, The solvent further includes a co-solvent, and the co-solvent includes at least one of benzene solvents, fluorinated hydrocarbon solvents, and ether solvents.

13. The electrolyte according to claim 12, wherein The volume ratio of the ionic liquid to the co-solvent is 1:9 to 9:

1.

14. The electrolyte according to claim 12 or 13, characterized in that, The co-solvent has at least one of the following characteristics (1) to (3): (1) The benzene solvent includes at least one of cyclohexane, benzene, toluene, p-xylene, m-xylene, o-xylene, fluorobenzene, p-difluorobenzene, m-difluorobenzene, o-difluorobenzene, trifluorotoluene, and trifluoromethoxybenzene; (2) The fluorinated hydrocarbon solvent includes decafluoropentane, perfluoropentanone, and 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane; (3) The ether solvent includes at least one of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl) ether, 1,1,2,3,3,3-hexafluoropropyl ethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-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.

15. A battery cell, characterized in that, It includes the electrolyte according to any one of claims 9 to 14.

16. A battery, characterized in that, It includes the battery cell according to claim 15.

17. An electrical device, characterized in that, Comprising the battery according to claim 16.

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