Electrolyte, lithium-ion battery and electrical device

Abstract

The present invention relates to an electrolyte, a lithium ion battery and an electrical device. The electrolyte comprises a lithium salt, a solvent and a diluent; wherein the solvent comprises a compound having a general structural formula as shown in formula (I): wherein R1 and R2 are independently selected from nitrogen-containing groups, substituted or unsubstituted C1-C 12 The electrolyte provided by the present application improves the high-voltage resistance and thermal stability of a single dicarbonate solvent without adding additional additives or increasing the concentration of lithium salts, and the electrolyte has good interfacial compatibility, low viscosity, and good wettability, which is conducive to the transmission and migration of ions, thereby improving the electrochemical performance of lithium-ion batteries.

Description

Technical Field

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

[0002] With the widespread application of lithium-ion batteries in electric vehicles, electronic products and other fields, users have put forward higher and higher requirements for their performance, especially higher energy density.

[0003] The general formula of lithium-ion electrolyte is to dissolve 1 mol / L salt solution in a mixed solvent of cyclic ethylene carbonate and linear carbonate, among which free solvent molecules account for the majority, and the solvated structures are mostly solvent-separated ion pair structures (SSIP) and a few are contact ion pair structures (CIP), which determines that the operating voltage of the battery is limited, and thus the improvement of energy density is limited.

[0004] Dicarbonate solvents have longer chemical chains and therefore have stronger high pressure resistance, and can be used to replace mixed solvents of cyclic ethylene carbonate and linear carbonate.

[0005] In conventional technology, the high voltage resistance of dicarbonate solvent electrolyte is further improved by adding additives or increasing the concentration of lithium salt.

[0006] However, adding additives or increasing the lithium salt greatly increases the cost of the electrolyte, and the increase in lithium salt concentration will make the viscosity of the electrolyte too high, thereby affecting the migration rate of lithium ions. In addition, the applicant has found that if a single dicarbonate solvent is used in the electrolyte, there are problems of high viscosity and poor wettability, which will also make it difficult for ions to migrate in the electrolyte. Summary of the invention

[0007] Based on this, it is necessary to provide an electrolyte, a lithium-ion battery and an electrical device to improve the high-voltage resistance of the electrolyte while reducing the viscosity of the electrolyte, improving the wetting properties of the electrolyte, and improving the ionic conductivity of the electrolyte.

[0008] The first aspect of the present application provides an electrolyte, which includes a lithium salt, a solvent and a diluent; wherein the solvent includes a compound having a structural formula as shown in formula (I):

[0009] ;

[0010] In formula (I), R1 and R2 are independently selected from nitrogen-containing groups, substituted or unsubstituted C1-C 12 Any hydrocarbon group.

[0011] In some embodiments, the substituted C1-C 12In the hydrocarbon group, the substituent includes at least one of halogen, C1-C5 alkyl or C2-C5 alkenyl.

[0012] In some embodiments, the solvent comprises at least two compounds having formula (I).

[0013] In some embodiments, based on the total mass of the solvent and the diluent being 100%, the mass percentage of the diluent is 10% to 30%.

[0014] In some embodiments, the solubility of the diluent for the lithium salt is less than 0.1 mol / L; and / or the diluent includes one or more of 2H,3H-decafluoropentane, tert-butylcyclohexane, 1,1,1-trichlorotrifluoroethane, 1H-perfluorohexane, tris(trifluoroethoxy)methane, methyl nonafluorobutyl ether, 2,2,3,3,3-pentafluoropropyl methyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether and 2,2,2-trifluoroethyl ether.

[0015] In some embodiments, the concentration of the lithium salt in the electrolyte is 0.5 mol / L to 0.8 mol / L.

[0016] In some embodiments, the compound having the general structural formula as shown in formula (I) is selected from at least one of the following compounds:

[0017] Formula (I-1), Formula (I-2), Formula (Ⅰ-3).

[0018] In some embodiments, the viscosity of the electrolyte at 25° C. is 5.1 mPa·s to 19.7 mPa·s.

[0019] In some embodiments, the ionic conductivity of the electrolyte at 25° C. is 7.9 ms / cm to 12.6 ms / cm.

[0020] The second aspect of the present application provides a lithium ion battery, which includes a positive electrode, a negative electrode, a separator and the electrolyte provided by the first aspect, and the positive electrode includes at least one positive electrode active material with a charge cut-off voltage higher than 4.5V.

[0021] A third aspect of the present application provides an electrical device, which includes the lithium-ion battery provided in the second aspect.

[0022] Compared with the traditional technology, the present invention has the following beneficial effects:

[0023] The electrolyte provided by the present application, on the one hand, uses a dicarbonate compound as the main solvent to form a high-voltage resistant electrolyte that does not require additional additives. However, dicarbonate has a high viscosity. When a dicarbonate compound is used as the main solvent, the electrolyte cannot meet the requirements of daily use. The present application forms a local high-concentration electrolyte by the interaction between the diluent and the compound solvent having the structural formula shown in formula (I) and the lithium salt. The diluent weakens the strong binding between the lithium salt ions and the dicarbonate solvent to a certain extent. The free solvent ratio of the local high-concentration electrolyte is small, and the solvation structure is based on contact ion pairs (CIP) and polymers. The solvated structure is composed of a group cluster (AGG). Compared with the free solvent molecule, the HOMO energy level of such a solvated structure is lower, thereby enhancing the high-voltage stability of the electrolyte. The chemical structure of the compound solvent with the general structural formula shown in formula (I) and the anions in the lithium salt can work together on the positive and negative electrode surfaces to form CEI film and SEI film, improving the interface chemistry, thereby showing excellent high-voltage resistance and thermal stability; on the other hand, the diluent acts as a molecular lubricant in the electrolyte, which helps to reduce the friction between molecules, thereby facilitating the migration and transmission of ions, reducing the viscosity of the electrolyte, and improving the wetting properties of the electrolyte.

[0024] In summary, the electrolyte provided in the present application improves the high-voltage resistance and thermal stability of a single dicarbonate solvent without adding additional additives or increasing the lithium salt concentration, and the electrolyte has good interfacial compatibility, low viscosity, and good wettability, which is conducive to the transmission and migration of ions, forming a new low-concentration lithium salt (lithium salt concentration is less than 1 mol / L) electrolyte system, reducing the cost of the electrolyte, matching the high viscosity characteristics of the dicarbonate solvent, matching the requirements of the high voltage system, and thereby improving the electrochemical performance of the lithium-ion battery. DETAILED DESCRIPTION

[0025] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0026] In the description of the present application, unless otherwise defined, the professional terms and professional words that are not clearly stated are the same as the meanings that are generally understood by those skilled in the art, and are common knowledge of those skilled in the art, and the methods that are not clearly stated are all conventional methods known to those skilled in the art. The meaning of the term "multiple" in the present application is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features. In the description of the present application, unless otherwise defined, the professional terms and professional words that are not clearly stated are the same as the meanings that are generally understood by those skilled in the art, and are common knowledge of those skilled in the art, and the methods that are not clearly stated are all conventional methods known to those skilled in the art. The meaning of the term "multiple" in the present application is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0027] In the description of the present application, unless otherwise defined, the professional terms and professional words not clearly described are the same as the meanings commonly understood by those skilled in the art, and are common knowledge of those skilled in the art, and the methods not clearly described are conventional methods known to those skilled in the art. The meaning of the term "multiple" in the present application is at least two, such as two, three, etc., unless otherwise clearly and specifically limited. In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0028] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0029] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0030] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0031] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0032] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0033] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0034] "Hydrocarbon group" refers to a group containing only carbon and hydrogen atoms, including but not limited to alkyl, alkenyl, alkynyl, aryl, etc.

[0035] "Alkyl" refers to a saturated hydrocarbon containing primary (normal) carbon atoms, or secondary carbon atoms, or tertiary carbon atoms, or quaternary carbon atoms, or a combination thereof. Phrases containing this term, for example, "C1-C9 alkyl" refers to an alkyl group containing 1 to 9 carbon atoms, each occurrence of which can be independently C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, C7 alkyl, C8 alkyl or C9 alkyl. Suitable examples include, but are not limited to, methyl (Me, -CH3), ethyl (Et, -CH2CH3), 1-propyl (n-Pr, n-propyl, -CH2CH2CH3), 2-propyl (i-Pr, i-propyl, -CH(CH3)2), 1-butyl (n-Bu, n-butyl, -CH2CH2CH2CH3), 2-methyl-1-propyl (i-Bu, i-butyl, -CH2CH(CH3)2), 2-butyl (s-Bu, s-butyl, -CH(C H3)CH2CH3), 2-methyl-2-propyl (t-Bu, t-butyl, -C(CH3)3), 1-pentyl (n-pentyl, -CH2CH2CH2CH2CH3), 2-pentyl (-CH(CH3)CH2CH2CH3), 3-pentyl (-CH(CH2CH3)2), 2-methyl-2-butyl (-C(CH3)2CH2CH3), 3-methyl-2-butyl (-CH(CH3)CH(CH3)2), 3-methyl-1-butyl (- CH2CH2CH(CH3)2), 2-methyl-1-butyl (-CH2CH(CH3)CH2CH3), 1-hexyl (-CH2CH2CH2CH2CH2CH3), 2-hexyl (-CH(CH3)CH2CH2CH2CH3), 3-hexyl (-CH(CH2CH3)(CH2CH2CH3)), 2-methyl-2-pentyl (-C(CH3)2CH2CH2CH3), 3-methyl-2-pentyl (-CH(CH3)CH( 2), 2-methyl-3-pentyl (-CH(CH2CH3)CH(CH3)2), 2,3-dimethyl-2-butyl (-C(CH3)2CH(CH3)2), 3,3-dimethyl-2-butyl (-CH(CH3)C(CH3)3 and octyl (-(CH2)7CH3).

[0036] "Alkenyl" refers to a group containing at least one unsaturated site, i.e., a carbon-carbon sp 2A hydrocarbon of a positive carbon atom, a secondary carbon atom, a tertiary carbon atom or a ring carbon atom of a double bond. A phrase comprising the term, for example, "C2-C9 alkenyl" refers to an alkenyl group comprising 2 to 9 carbon atoms, each occurrence of which may be independently C2 alkenyl, C3 alkenyl, C4 alkenyl, C5 alkenyl, C6 alkenyl, C7 alkenyl, C8 alkenyl or C9 alkenyl. Suitable examples include, but are not limited to, vinyl (-CH=CH2), allyl (-CH2CH=CH2), cyclopentenyl (-C5H7) and 5-hexenyl (-CH2CH2CH2CH2CH=CH2).

[0037] "Alkynyl" refers to a hydrocarbon containing a positive carbon atom, a secondary carbon atom, a tertiary carbon atom or a ring carbon atom having at least one unsaturated site, i.e., a carbon-carbon sp triple bond. Phrases containing this term, for example, "C2-C9 alkenyl" refers to an alkynyl group containing 2 to 9 carbon atoms, each occurrence of which can be independently C2 alkynyl, C3 alkynyl, C4 alkynyl, C5 alkynyl, C6 alkynyl, C7 alkynyl, C8 alkynyl or C9 alkynyl. Suitable examples include, but are not limited to, ethynyl (-C≡CH) and propargyl (-CH2C≡CH).

[0038] "Aryl" refers to an aromatic hydrocarbon group derived from an aromatic ring compound by removing a hydrogen atom. It can be a monocyclic aromatic group, a condensed aromatic group, or a polycyclic aromatic group. For polycyclic rings, at least one is an aromatic ring system. For example, "C5-C 20 "Aryl" refers to an aromatic group containing 5 to 20 carbon atoms, and each occurrence can be independently C5 aromatic group, C6 aromatic group, C 10 Aryl, C 14 Aryl, C 18 Aryl or C 20 Aryl. Suitable examples include, but are not limited to, benzene, biphenyl, naphthalene, anthracene, phenanthrene, perylene, triphenylene and derivatives thereof. It is understood that multiple aryl groups may also be interrupted by short non-aromatic units (e.g., <10% non-H atoms, such as C, N or O atoms), specifically acenaphthene, fluorene, or 9,9-diarylfluorene, triarylamine, diaryl ether systems should also be included in the definition of aryl.

[0039] The "nitrogen-containing group" refers to a group containing a nitrogen atom in the group, including an amine group, an amide group, a cyano group, and the like.

[0040] "Halogen" or "halo" refers to F, Cl, Br or I.

[0041] The “solvent-separated ion pair structure” refers to the fact that a large number of free solvent molecules dissolve the lithium salt and make Li + Isolated from lithium salt anion dissociation.

[0042] A contact ion pair is an anion and a Li +Coordination.

[0043] A “cluster aggregate” refers to an anion with two or more Li + Coordination.

[0044] The first aspect of the present application provides an electrolyte, which includes a lithium salt, a solvent and a diluent; wherein the solvent includes a compound having a structural formula as shown in formula (I):

[0045] ;

[0046] In formula (I), R1 and R2 are independently selected from nitrogen-containing groups, substituted or unsubstituted C1-C 12 Any hydrocarbon group.

[0047] On the one hand, through the interaction between the diluent and the compound solvent having the general structural formula shown in formula (I) and the lithium salt, the diluent weakens the strong binding between ions and solvent to a certain extent, forming a local high-concentration electrolyte. The free solvent accounts for a small proportion of the local high-concentration electrolyte, and the solvation structure is composed of contact ion pairs (CIP) and aggregate clusters (AGG). Such a solvation structure has a lower HOMO energy level than the free solvent molecules, thereby enhancing the high-voltage stability of the electrolyte. The chemical structure of the compound solvent having the general structural formula shown in formula (I) and the anions in the lithium salt can dominate the formation of a CEI film on the positive electrode surface, improve the interface chemistry, and thus exhibit excellent high-voltage resistance and thermal stability. On the other hand, the diluent acts as a molecular lubricant in the electrolyte, which helps to reduce the friction between molecules, thereby facilitating the migration and transmission of ions, reducing the viscosity of the electrolyte, and improving the wetting properties of the electrolyte.

[0048] In summary, the electrolyte provided in the present application improves the high-voltage resistance and thermal stability of the dicarbonate solvent without adding additional additives or increasing the lithium salt concentration, and the electrolyte has good interfacial compatibility, low viscosity, and good wettability, which is beneficial to the transmission and migration of ions, thereby improving the electrochemical performance of lithium-ion batteries.

[0049] It is understandable that the dielectric constant ε of the compound having the general structural formula shown in formula (I) is low. During the charging process, the accumulation amount of free solvent molecules of the compound on the positive electrode surface is small, and the anions of the lithium salt are mainly gathered on the positive electrode surface. Therefore, the CEI film will be mainly formed by the decomposition product of the solvent and the lithium salt anion complex. Compared with the traditional carbonate system of more than 1 mol / L and the single dicarbonate system, the CEI film formed by the electrolyte provided in the present application has a lower contribution from the oxidative decomposition of free solvent molecules, and the content of inorganic matter in the formed CEI film is higher than that of the traditional electrolyte system, thereby promoting the formation of a more dense, uniform and strong CEI film, effectively inhibiting the further decomposition of the electrolyte, maintaining the stability of the positive electrode-electrolyte interface, and is conducive to improving the energy density of the battery and improving the long cycle performance of the battery.

[0050] In some embodiments, the substituted C1-C 12 In the hydrocarbon group, the substituent includes at least one of halogen, C1-C5 alkyl or C2-C5 alkenyl.

[0051] In some embodiments, at least one of R1 and R2 is selected from a substituted or unsubstituted C1-C6 hydrocarbon group.

[0052] In some embodiments, at least one of R1 and R2 is selected from substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C6 alkenyl, substituted or unsubstituted C3-C6 alkynyl.

[0053] In some embodiments, at least one of R1 and R2 is selected from C1-C6 alkyl substituted by halogen.

[0054] In some embodiments, at least one of R1 and R2 is a nitrogen-containing group.

[0055] In some embodiments, the nitrogen-containing group is selected from one or more of an amino group, an amide group, and a cyano group.

[0056] In some embodiments, the solvent comprises at least two compounds represented by formula (I).

[0057] In some embodiments, the mass percentage of the diluent is 10% to 30%, including but not limited to 10%, 15%, 20%, 25%, and 30%, based on the total mass of the solvent and the diluent being 100%. Further, the mass percentage of the diluent is 20%.

[0058] In some embodiments, the solubility of the diluent in the lithium salt is less than 0.1 mol / L.

[0059] In some embodiments, the diluent includes one or more of 2H,3H-decafluoropentane, tert-butylcyclohexane, 1,1,1-trichlorotrifluoroethane, 1H-perfluorohexane, tris(trifluoroethoxy)methane, methyl nonafluorobutyl ether, 2,2,3,3,3-pentafluoropropyl methyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether and 2,2,2-trifluoroethyl ether.

[0060] In some embodiments, the lithium salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium perchlorate (LiClO4), lithium tetraphenylborate (LiB(C6H5)4), lithium methanesulfonate (LiCH3SO3), lithium bis(trifluoromethanesulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethylsulfonyl)imide (LiN(SO2CF3)2), tris(trifluoromethylsulfonyl)methyl lithium (LiC(SO2CF3)3), lithium bis(oxalatoborate) (LiBOB) and lithium difluorophosphate (LiPO2F2).

[0061] In some embodiments, the concentration of the lithium salt in the electrolyte is 0.5 mol / L~0.8 mol / L, including but not limited to 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L; preferably, the concentration of the lithium salt in the electrolyte is 0.6 mol / L~0.8 mol / L.

[0062] In traditional technology, the oxidation resistance of the electrolyte is improved by increasing the concentration of lithium salt in the electrolyte. However, based on the traditional electrolyte system, the electrolyte is mainly composed of free solvent molecules. As the concentration of lithium salt increases, the solvent molecules are limited, so the improvement in pressure resistance is limited, and the viscosity of the electrolyte will be too high, inhibiting the ion transmission performance. The electrolyte of the present application forms a local high-concentration electrolyte through the interaction of diluent, solvent and lithium salt, so that the high-voltage resistance can still be achieved when the concentration of lithium salt in the electrolyte is reduced, thereby reducing the viscosity of the electrolyte, improving the ion transmission performance, and saving the cost of lithium salt.

[0063] In some embodiments, the compound having the general structural formula as shown in formula (I) is selected from at least one of the following compounds:

[0064] Formula (I-1), Formula (I-2), Formula (Ⅰ-3).

[0065] In some embodiments, the viscosity of the electrolyte at 25° C. is 5.1 mPa·s to 19.7 mPa·s.

[0066] In some embodiments, the ionic conductivity of the electrolyte at 25° C. is 7.9 ms / cm to 12.6 ms / cm.

[0067] The second aspect of the present application provides a lithium-ion battery, which includes a positive electrode, a negative electrode, a separator and the electrolyte provided by the first aspect above; preferably, the positive electrode includes at least one positive electrode active material with a charge cut-off voltage higher than 4.5V; further preferably, the positive electrode includes at least one positive electrode active material with a charge cut-off voltage higher than 4.6V; particularly preferably, the positive electrode includes at least one positive electrode active material with a charge cut-off voltage higher than 4.8V.

[0068] It is understood that the positive electrode active material of the present application can be a mixture or a pure substance. When it is a pure substance, it can be a positive electrode active material with a charge cut-off voltage greater than 4.5 V. When it is a mixture, it can be a mixture of multiple positive electrode active materials with a charge cut-off voltage greater than 4.5 V, or it can be a mixture of one or more positive electrode active materials with a charge cut-off voltage greater than 4.5 V and one or more positive electrode materials with a charge cut-off voltage lower than 4.5 V.

[0069] As an embodiment, the positive electrode active material is a mixture, and the voltage platform of at least one positive electrode active material is higher than 4.5V.

[0070] As an embodiment, the positive electrode active material is a mixture, and the charging cut-off voltage of at least one positive electrode active material is ≥4.6V.

[0071] As an embodiment, the positive electrode active material is a mixture of a plurality of positive electrode active materials with a charge cut-off voltage ≥ 4.6V.

[0072] As an embodiment, the positive electrode active material is a pure substance.

[0073] It is understandable that a pure substance refers to a substance containing only one positive electrode active material, and the presence of impurities and non-positive electrode active material additives in a single positive electrode active material system should not be interpreted as the positive electrode active material system being a mixture.

[0074] Preferably, the charging cut-off voltage of the positive electrode active material is greater than 4.8V.

[0075] Preferably, the positive electrode active material with a charging cut-off voltage greater than 4.5V accounts for more than 50wt% of all the positive electrode active materials in the positive electrode active material layer; further preferably, the positive electrode active material with a charging cut-off voltage greater than 4.5V accounts for more than 70wt% of all the positive electrode active materials in the positive electrode active material layer; particularly preferably, the positive electrode active material with a charging cut-off voltage greater than 4.5V accounts for more than 90wt% of all the positive electrode active materials in the positive electrode active material layer.

[0076] It can be understood that when using a multi-layer electrode, as long as one layer in the entire positive electrode active material layer meets the above proportion requirements, it should be considered to fall within the protection scope of this application. The above positive electrode active material layer should be understood as the active material layer containing the positive electrode active material with a charging cut-off voltage greater than 4.5V, rather than the entire positive electrode active material layer.

[0077] Merely as a schematic example, rather than a limitation of the protection scope, the positive electrode active material operating at a potential above 4.5V relative to lithium is preferably a lithium-containing composite oxide. The lithium-containing composite oxides include spinel-type lithium manganese composite oxides, olivine-type lithium manganese-containing composite oxides, and inverse spinel-type lithium manganese-containing composite oxides.

[0078] In addition, as a lithium manganese composite oxide containing Mn, for example, manganese spinel represented by the following formula can be used: Li a (M x Mn 2-x )O4, where 0.4 < x < 2, and 0 < a < 1.2; and M is at least one selected from the group consisting of Ni, Co, Fe, Cr, and Cu. Among them, from the perspective of safety, spinel-type lithium manganese composite oxides are preferred.

[0079] Preferably, a lithium manganese composite oxide represented by the following formula is preferably used: Li a (M x Mn 2-x-y Y y )(O 4-w Z w ) where 0.4 < x ≤ 1.2, 0 ≤ y, x + y < 2, 0 ≤ a ≤ 1.2, and 0 ≤ w ≤ 1; M is at least one selected from Co, Ni, Fe, Cr, and Cu; Y is at least one selected from Li, B, Na, Mg, Al, Ti, Si, K, and Ca; and Z is at least one selected from F and Cl.

[0080] Preferably, from the perspective of obtaining sufficient capacity and achieving a longer life, among these lithium manganese composite oxides, a spinel-type compound represented by the following formula is more preferably used. LiNi x Mn 2-x-y A yO4 wherein, 0.4 < x < 0.6 and 0 ≤ y < 0.3, and A represents at least one metal selected from Li, B, Na, Mg, Al, Ti, and Si. Preferably, 0 ≤ y < 0.2.

[0081] Preferably, examples of other high-voltage cathode active materials include olivine compounds represented by the following formula: Li x MPO4F y , wherein, 0 ≤ x ≤ 2 and 0 ≤ y ≤ 1, and M is at least one selected from Co and Ni.

[0082] Preferably, examples of cathode active materials with a charge cut-off voltage reaching 5V include compounds represented by the following formula: Li x [Li a M b Mn 1-a-b O2, wherein, 0 ≤ x ≤ 1, 0.05 ≤ a ≤ 0.3, and 0.1 < b < 0.4, and M is at least one selected from Ni, Co, Fe, and Cr.

[0083] It can be understood that when the cathode active material is a mixture composed of a high-voltage cathode active material and a cathode active material with a charge cut-off voltage lower than 4.5V, the present application has no particular limitation on the type of the cathode active material with a charge cut-off voltage lower than 4.5V. Based on the inventive concept of the present application, any type of cathode active material can be used in the present application. Merely as a schematic example rather than a limitation of the protection scope, the cathode active material with a charge cut-off voltage lower than 4.5V is one of a layered oxide cathode material, a spinel cathode, and a polyanion cathode. For example, the layered oxide cathode (e.g., rock salt layered oxide) contains one or more lithium-based cathode active materials selected from the following: LiCoO2 (LCO), LiNi 1-x-y Co x Al y O2 (where 0 ≤ x ≤ 1 and 0 ≤ y ≤ 1) and Li 1+x MO2 (where M is one of Ni, Co, and Al and 0 ≤ x ≤ 1); the spinel cathode contains one or more lithium-based cathode electroactive materials selected from the following: LiMn2O4 (LMO) and LiNi x Mn 1.5 O4. The olivine-type cathode contains one or more lithium-based cathode active materials LiMPO4 (where M is at least one of Fe, Ni, and Co); it can be understood that the above materials are merely schematic examples rather than a limitation of the protection scope.

[0084] In one embodiment, one or more lithium-based positive active materials may be optionally coated (e.g., by LiNbO3 and / or Al2O3) and / or may be doped (e.g., by magnesium (Mg)). It is also possible to form a core-shell structure by coating two positive active materials with each other, such as using a low-voltage positive electrode material to coat a high-voltage positive electrode material. It is understood that improvements to the positive electrode material or the positive electrode active material layer are within the scope of protection of the present application. In addition, in certain embodiments, one or more lithium-based positive active materials may be optionally mixed with one or more conductive agents that provide an electronic conduction path and / or at least one polymer binder that improves the structural integrity of the positive electrode. For example, the positive electrode active material layer may contain greater than or equal to about 30wt% to less than or equal to about 99wt% of one or more lithium-based positive active materials; greater than or equal to about 0wt% to less than or equal to about 30wt% of a conductive agent; and greater than or equal to about 0wt% to less than or equal to about 20wt% of a binder, and in some aspects, optionally greater than or equal to about 1wt% to less than or equal to about 20wt% of a binder. Among lithium-based positive electrode active materials, the present application does not limit the proportion of high-voltage positive electrode materials. Without violating the inventive concept of the present application, the adjustment of the addition amount of high-voltage positive electrode materials should be deemed to be within the protection scope of the present application; preferably, the positive electrode active materials with a charging cut-off voltage greater than 4.5V account for more than 50wt% of all positive electrode active materials; further preferably, the positive electrode active materials with a charging cut-off voltage greater than 4.5V account for more than 70wt% of all positive electrode active materials; particularly preferably, the positive electrode active materials with a charging cut-off voltage greater than 4.5V account for more than 90wt% of all positive electrode active materials.

[0085] In some embodiments, the negative electrode includes a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer includes a negative electrode active material. The negative electrode active material includes one or more of graphite, soft carbon, hard carbon, a composite material of single crystal silicon and graphite, a composite material of silicon oxide and graphite, lithium titanate, or niobium pentoxide.

[0086] It is understood that lithium-ion batteries can be prepared and used according to conventional methods known in the art.

[0087] In some of the embodiments, the electrolyte can be prepared as follows: in a glove box, an organic solvent and a sufficiently dried lithium salt are mixed according to mass fractions, and then an additive is added and mixed uniformly to obtain an electrolyte.

[0088] A third aspect of the present application provides an electrical device, which includes the lithium-ion battery provided in the second aspect.

[0089] The electrical device of the present application is not particularly limited, and it can be any electrical device known in the prior art. For example, the electrical device can include, but is not limited to, a laptop computer, a pen-input computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.

[0090] The present application will be further described below with reference to specific embodiments and comparative examples.

[0091] In the following embodiments, comparative examples and test examples, the reagents, materials and instruments used are all commercially available unless otherwise specified.

[0092] Example 1

[0093] This embodiment provides an electrolyte and a lithium-ion battery.

[0094] Electrolyte:

[0095] The electrolyte includes a lithium salt, a solvent and a diluent. The lithium salt is 0.8 mol / L LiPF6, the diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether; and the solvent is a compound shown in the following formula (I-1):

[0096] ;

[0097] Wherein, taking the mass of the solvent and the diluent as 100%, the mass percentage of the diluent is 10%.

[0098] Lithium-ion battery:

[0099] The lithium-ion battery comprises a positive electrode, a negative electrode, a separator and the above-mentioned electrolyte.

[0100] The positive electrode includes a positive electrode active material layer and a positive electrode current collector, and the positive electrode active material layer includes 96wt% of the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, 2wt% of conductive agent Super-P and 2wt% of binder PVDF; the negative electrode includes a negative electrode active material layer and a negative electrode current collector, the negative electrode active material layer includes 95% of negative electrode active material graphite, 2wt% of conductive agent Super-P and 3wt% of binder (CMC+SBR).

[0101] Example 2

[0102] This embodiment provides an electrolyte and a lithium-ion battery.

[0103] Electrolyte:

[0104] The electrolyte includes a lithium salt, a solvent and a diluent. The lithium salt is 0.8 mol / L LiPF6, the diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether; and the solvent is a compound shown in the following formula (I-1):

[0105] ;

[0106] Wherein, taking the mass percentage of the solvent and the diluent as 100%, the mass percentage of the diluent is 20%.

[0107] Lithium-ion battery:

[0108] The lithium-ion battery comprises a positive electrode, a negative electrode, a separator and the above-mentioned electrolyte.

[0109] The positive electrode includes a positive electrode active material layer and a positive electrode current collector, and the positive electrode active material layer includes 96wt% of the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, 2wt% of conductive agent Super-P and 2wt% of binder PVDF; the negative electrode includes a negative electrode active material layer and a negative electrode current collector, the negative electrode active material layer includes 95% of negative electrode active material graphite, 2wt% of conductive agent Super-P and 3wt% of binder (CMC+SBR).

[0110] Example 3

[0111] This embodiment provides an electrolyte and a lithium-ion battery.

[0112] Electrolyte:

[0113] The electrolyte includes a lithium salt, a solvent and a diluent. The lithium salt is 0.8 mol / L LiPF6, the diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether; and the solvent is a compound shown in the following formula (I-1):

[0114] ;

[0115] Wherein, taking the mass percentage of the solvent and the diluent as 100%, the mass percentage of the diluent is 30%.

[0116] Lithium-ion battery:

[0117] The lithium-ion battery comprises a positive electrode, a negative electrode, a separator and the above-mentioned electrolyte.

[0118] The positive electrode includes a positive electrode active material layer and a positive electrode current collector, and the positive electrode active material layer includes 96wt% of the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, 2wt% of conductive agent Super-P and 2wt% of binder PVDF; the negative electrode includes a negative electrode active material layer and a negative electrode current collector, the negative electrode active material layer includes 95% of negative electrode active material graphite, 2wt% of conductive agent Super-P and 3wt% of binder (CMC+SBR).

[0119] Example 4

[0120] This embodiment provides an electrolyte and a lithium-ion battery.

[0121] Electrolyte:

[0122] The electrolyte includes a lithium salt, a solvent and a diluent. The lithium salt is 0.8 mol / L LiPF6, the diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether; and the solvent is a compound shown in the following formula (I-1):

[0123] ;

[0124] Wherein, taking the mass percentage of the solvent and the diluent as 100%, the mass percentage of the diluent is 40%.

[0125] Lithium-ion battery:

[0126] The lithium-ion battery comprises a positive electrode, a negative electrode, a separator and the above-mentioned electrolyte.

[0127] The positive electrode includes a positive electrode active material layer and a positive electrode current collector, and the positive electrode active material layer includes 96wt% of the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, 2wt% of conductive agent Super-P and 2wt% of binder PVDF; the negative electrode includes a negative electrode active material layer and a negative electrode current collector, the negative electrode active material layer includes 95% of negative electrode active material graphite, 2wt% of conductive agent Super-P and 3wt% of binder (CMC+SBR).

[0128] Example 5

[0129] This embodiment provides an electrolyte and a lithium-ion battery.

[0130] Electrolyte:

[0131] The electrolyte includes a lithium salt, a solvent and a diluent. The lithium salt is 0.8 mol / L LiPF6, the diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether; and the solvent is a compound shown in the following formula (I-1):

[0132] ;

[0133] Wherein, taking the mass percentage of the solvent and the diluent as 100%, the mass percentage of the diluent is 50%.

[0134] Lithium-ion battery:

[0135] The lithium-ion battery comprises a positive electrode, a negative electrode, a separator and the above-mentioned electrolyte.

[0136] The positive electrode includes a positive electrode active material layer and a positive electrode current collector, and the positive electrode active material layer includes 96wt% of the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, 2wt% of conductive agent Super-P and 2wt% of binder PVDF; the negative electrode includes a negative electrode active material layer and a negative electrode current collector, the negative electrode active material layer includes 95% of negative electrode active material graphite, 2wt% of conductive agent Super-P and 3wt% of binder (CMC+SBR).

[0137] Example 6

[0138] This embodiment provides an electrolyte and a lithium-ion battery.

[0139] Electrolyte:

[0140] The electrolyte includes a lithium salt, a solvent and a diluent. The lithium salt is 0.8 mol / L LiPF6, the diluent is 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether; and the solvent is a compound shown in the following formula (I-1):

[0141] ;

[0142] Wherein, taking the mass percentage of the solvent and the diluent as 100%, the mass percentage of the diluent is 30%.

[0143] Lithium-ion battery:

[0144] The lithium-ion battery comprises a positive electrode, a negative electrode, a separator and the above-mentioned electrolyte.

[0145] The positive electrode includes a positive electrode active material layer and a positive electrode current collector, and the positive electrode active material layer includes 96wt% of the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1O2, 2wt% of conductive agent Super-P and 2wt% of binder PVDF; the negative electrode includes a negative electrode active material layer and a negative electrode current collector, the negative electrode active material layer includes 95% of negative electrode active material graphite, 2wt% of conductive agent Super-P and 3wt% of binder (CMC+SBR).

[0146] Example 7

[0147] This embodiment provides an electrolyte and a lithium-ion battery.

[0148] Electrolyte:

[0149] The electrolyte includes a lithium salt, a solvent and a diluent. The lithium salt is 0.8 mol / L LiPF6, the diluent is 2,2,2-trifluoroethyl ether, and the solvent is a compound shown in the following formula (I-1):

[0150] ;

[0151] Wherein, taking the mass percentage of the solvent and the diluent as 100%, the mass percentage of the diluent is 30%.

[0152] Lithium-ion battery:

[0153] The lithium-ion battery comprises a positive electrode, a negative electrode, a separator and the above-mentioned electrolyte.

[0154] The positive electrode includes a positive electrode active material layer and a positive electrode current collector, and the positive electrode active material layer includes 96wt% of the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, 2wt% of conductive agent Super-P and 2wt% of binder PVDF; the negative electrode includes a negative electrode active material layer and a negative electrode current collector, the negative electrode active material layer includes 95% of negative electrode active material graphite, 2wt% of conductive agent Super-P and 3wt% of binder (CMC+SBR).

[0155] Example 8

[0156] This embodiment provides an electrolyte and a lithium-ion battery.

[0157] Electrolyte:

[0158] The electrolyte includes a lithium salt, a solvent and a diluent. The lithium salt is 0.8 mol / L LiPF6, the diluent is 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether; and the solvent is a compound shown in the following formula (I-2):

[0159] ;

[0160] Wherein, taking the mass percentage of the solvent and the diluent as 100%, the mass percentage of the diluent is 30%.

[0161] Lithium-ion battery:

[0162] The lithium-ion battery comprises a positive electrode, a negative electrode, a separator and the above-mentioned electrolyte.

[0163] The positive electrode includes a positive electrode active material layer and a positive electrode current collector, and the positive electrode active material layer includes 96wt% of the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, 2wt% of conductive agent Super-P and 2wt% of binder PVDF; the negative electrode includes a negative electrode active material layer and a negative electrode current collector, the negative electrode active material layer includes 95% of negative electrode active material graphite, 2wt% of conductive agent Super-P and 3wt% of binder (CMC+SBR).

[0164] Example 9

[0165] This embodiment provides an electrolyte and a lithium-ion battery.

[0166] Electrolyte:

[0167] The electrolyte includes a lithium salt, a solvent and a diluent. The lithium salt is 0.8 mol / L LiPF6, the diluent is 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether; and the solvent is a compound shown in the following formula (I-3):

[0168] ;

[0169] Wherein, taking the mass percentage of the solvent and the diluent as 100%, the mass percentage of the diluent is 30%.

[0170] Lithium-ion battery:

[0171] The lithium-ion battery comprises a positive electrode, a negative electrode, a separator and the above-mentioned electrolyte.

[0172] The positive electrode includes a positive electrode active material layer and a positive electrode current collector, and the positive electrode active material layer includes 96wt% of the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, 2wt% of conductive agent Super-P and 2wt% of binder PVDF; the negative electrode includes a negative electrode active material layer and a negative electrode current collector, and the negative electrode active material layer includes 95% of negative electrode active material graphite, 2wt% of conductive agent Super-P and 3wt% of binder (CMC+SBR)0

[0173] Example 10

[0174] This embodiment provides an electrolyte and a lithium-ion battery.

[0175] Electrolyte:

[0176] The electrolyte includes a lithium salt, a solvent and a diluent. The lithium salt is 1 mol / L LiPF6, the diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether; and the solvent is a compound shown in the following formula (I-1):

[0177] ;

[0178] Wherein, taking the mass of the solvent and the diluent as 100%, the mass percentage of the diluent is 10%.

[0179] Lithium-ion battery:

[0180] The lithium-ion battery comprises a positive electrode, a negative electrode, a separator and the above-mentioned electrolyte.

[0181] The positive electrode includes a positive electrode active material layer and a positive electrode current collector, and the positive electrode active material layer includes 96wt% of the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, 2wt% of conductive agent Super-P and 2wt% of binder PVDF; the negative electrode includes a negative electrode active material layer and a negative electrode current collector, the negative electrode active material layer includes 95% of negative electrode active material graphite, 2wt% of conductive agent Super-P and 3wt% of binder (CMC+SBR).

[0182] The important parameters of the embodiment are sorted out as shown in the following Table 1:

[0183]

[0184] Wherein, “ / ” represents the absence of the substance or parameter.

[0185] Comparative Example 1

[0186] This comparative example provides an electrolyte and a lithium ion battery.

[0187] Electrolyte:

[0188] The electrolyte includes a lithium salt and a solvent. The lithium salt is 0.8 mol / L LiPF6, and the solvent is a compound shown in the following formula (I-1):

[0189] .

[0190] Lithium-ion battery:

[0191] The lithium-ion battery comprises a positive electrode, a negative electrode, a separator and the above-mentioned electrolyte.

[0192] The positive electrode includes a positive electrode active material layer and a positive electrode current collector, and the positive electrode active material layer includes 96wt% of the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, 2wt% of conductive agent Super-P and 2wt% of binder PVDF; the negative electrode includes a negative electrode active material layer and a negative electrode current collector, the negative electrode active material layer includes 95% of negative electrode active material graphite, 2wt% of conductive agent Super-P and 3wt% of binder (CMC+SBR).

[0193] Comparative Example 2

[0194] This comparative example provides an electrolyte and a lithium ion battery.

[0195] Electrolyte:

[0196] The electrolyte includes a lithium salt and a solvent. The lithium salt is 0.3 mol / L LiPF6, and the solvent is a compound shown in the following formula (I-1):

[0197] .

[0198] Lithium-ion battery:

[0199] The lithium-ion battery comprises a positive electrode, a negative electrode, a separator and the above-mentioned electrolyte.

[0200] The positive electrode includes a positive electrode active material layer and a positive electrode current collector, and the positive electrode active material layer includes 96wt% of the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, 2wt% of conductive agent Super-P and 2wt% of binder PVDF; the negative electrode includes a negative electrode active material layer and a negative electrode current collector, the negative electrode active material layer includes 95% of negative electrode active material graphite, 2wt% of conductive agent Super-P and 3wt% of binder (CMC+SBR).

[0201] Comparative Example 3

[0202] This comparative example provides an electrolyte and a lithium ion battery.

[0203] Electrolyte:

[0204] The electrolyte includes a lithium salt, a solvent and a diluent. The lithium salt is 0.8 mol / L LiPF6, and the solvent is a mixed solvent of EC and DMC in a volume ratio of 1:1.

[0205] Wherein, taking the mass percentage of the solvent and the diluent as 100%, the mass percentage of the diluent is 30%.

[0206] Lithium-ion battery:

[0207] The lithium-ion battery comprises a positive electrode, a negative electrode, a separator and the above-mentioned electrolyte.

[0208] The positive electrode includes a positive electrode active material layer and a positive electrode current collector, and the positive electrode active material layer includes 96wt% of the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, 2wt% of conductive agent Super-P and 2wt% of binder PVDF; the negative electrode includes a negative electrode active material layer and a negative electrode current collector, the negative electrode active material layer includes 95% of negative electrode active material graphite, 2wt% of conductive agent Super-P and 3wt% of binder (CMC+SBR).

[0209] Test Case

[0210] The lithium ion batteries obtained in the above examples and comparative examples were subjected to viscosity test, ion conductivity test and high voltage cycle performance test.

[0211] Test conditions for high voltage cycle test:

[0212] The charge and discharge potential range is 2.4V~4.25V, and the charging current is 0.33C to 4.25V. The specific test process is as follows: the lithium-ion battery is charged at a constant voltage of 4.25V to a cut-off current ≤0.05C, and then it is discharged at 0.33C to 2.4V and left to stand for 5 minutes. This is a charge and discharge cycle process, and the discharge capacity of the first cycle is recorded. The test results are shown in Table 2.

[0213] The lithium-ion battery was cycled at room temperature or high temperature for 500 cycles at 1C current according to the above method, and the discharge capacity of the 100th cycle was detected. Among them, the room temperature condition is 25°C and the high temperature condition is 45°C. The capacity retention rate (%) of the lithium-ion battery after 500 cycles is calculated = (discharge capacity of the lithium-ion battery after 500 cycles / discharge capacity of the lithium-ion battery in the first cycle) × 100%. The calculation results are shown in Table 2.

[0214]

[0215] Here, “ / ” means that the electrolyte cannot completely dissolve the lithium salt, so the electrolyte cannot be tested.

[0216] As shown in Table 2, by comparing Examples 1 to 10 with Comparative Examples 1 to 3, it can be seen that the use of the electrolyte of the present application improves the capacity performance and cycle performance of the lithium-ion battery under high voltage, while reducing the viscosity of the electrolyte and improving the ionic conductivity of the electrolyte.

[0217] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0218] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A lithium ion battery, characterized in that: The lithium-ion battery comprises a positive electrode, a negative electrode, a separator and an electrolyte, and the positive electrode comprises at least one positive electrode active material having a charge cut-off voltage higher than 4.5V; The electrolyte comprises a lithium salt, a solvent and a diluent; Wherein, the solvent includes a compound having a general structural formula as shown in formula (I): ； In formula (I), R1 and R2 are independently selected from nitrogen-containing groups, substituted or unsubstituted C1-C 12 Any of the hydrocarbon groups; The concentration of the lithium salt in the electrolyte is 0.5 mol / L to 0.8 mol / L; The solubility of the diluent in the lithium salt is less than 0.1 mol / L; and / or, The diluent includes one or more of 2H,3H-decafluoropentane, tert-butylcyclohexane, 1,1,1-trichlorotrifluoroethane, 1H-perfluorohexane, tris(trifluoroethoxy)methane, methyl nonafluorobutyl ether, 2,2,3,3,3-pentafluoropropyl methyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether and 2,2,2-trifluoroethyl ether; Taking the total mass of the solvent and the diluent as 100%, the mass percentage of the diluent is 25% to 30%; The electrolyte satisfies at least one of the following characteristics: (1) The viscosity of the electrolyte at 25° C. is 5.1 mPa·s to 9.6 mPa·s; (2) The ionic conductivity of the electrolyte at 25° C. is 9.8 ms / cm to 12.6 ms / cm; Substituted C1-C 12 In the hydrocarbon group of , the substituent is a halogen; The solvent comprises at least two compounds represented by formula (I).

2. The lithium-ion battery according to claim 1, characterized in that The compound having the general structural formula as shown in formula (I) is selected from at least one of the following compounds: Formula (I-1), Formula (I-2), Formula (Ⅰ-3).

3. An electrical device, characterized in that: Comprising the lithium ion battery as claimed in claim 1 or 2.

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