Composite electrolyte and lithium battery

Abstract

A composite electrolyte and a lithium battery. The composite electrolyte comprises a first lithium salt and a composite solvent; the composite solvent comprises ethylene glycol dimethyl ether (DME) and / or 1,3-dioxolane (DOL) and a fluorine-containing ether compound, and the molar ratio of DME and DOL to the fluorine-containing ether compound is 1:0.2-10; the fluorine-containing ether compound is represented by formula R1-O-R2; and in the formula, R1 is a C1-C10 fluoroalkyl or fluoroalkoxyalkyl group, and R2 is any C1-C5 fluoroalkyl or fluoroalkoxyalkyl group. The composite electrolyte can significantly improve the number of cycles and the charge-discharge rate of the lithium metal battery, and improves the performance and safety of the battery.

Description

Composite electrolyte and lithium battery Technical Field

[0001] The present invention relates to a novel composite electrolyte particularly suitable for lithium metal batteries, applications thereof, and a lithium battery comprising the composite electrolyte. Background Art

[0002] Lithium metal batteries are batteries that use metallic lithium as their negative electrode material. As high-energy-density batteries, they are widely used in electric vehicles, portable electronic devices, and energy storage systems. Their high energy density, lightweight design, and environmental friendliness make them a hot topic for research and development. The working principle of lithium metal batteries is that lithium ions are deposited on the lithium metal negative electrode during charging, migrate to the positive electrode through the intermediate membrane, and then migrate back to the positive electrode during discharge. The advantages of lithium metal batteries include high energy density and a high voltage platform. However, traditional lithium metal batteries face some technical difficulties during the cyclic charge and discharge process. One of the most important problems is the growth and accumulation of lithium dendrites. As lithium ions are continuously inserted and extracted during the charge and discharge process, lithium dendrites easily form on the surface of the lithium electrode and gradually expand to form a tree-like structure of lithium dendrites, resulting in reduced battery safety and shortened cycle life. This phenomenon is often referred to as the "lithium dendrite problem."

[0003] In order to solve the problem of lithium dendrites, current research mainly focuses on optimizing the electrolyte formulation, changing the structure of battery electrodes and using artificial coatings. However, there are still some limitations in the existing technology: a) Additive limitations: Although many additives have been introduced to inhibit the formation of lithium dendrites, the action mechanism and effect of different additives are still unclear, and the types and proportions of additives are limited. b) Difficulty in solvent selection: It is still challenging to select suitable organic solvents to improve the solubility and electrochemical properties of the electrolyte because the effects of different solvents on battery performance are complex and diverse. c) Limited choice of lithium salts: Lithium salts are the main component of the electrolyte. Different lithium salts have different effects on battery performance, but there is still a lack of more new lithium salts to choose from.

[0004] In summary, although some progress has been made in the research of electrolytes for lithium metal batteries, there are still certain limitations in solving the problem of lithium dendrites, and more in-depth research and innovation are needed.

[0005] Summary of the Invention

[0006] The present invention aims to solve the problem of lithium dendrites existing in the cyclic charge and discharge process of lithium metal batteries, and provide a new electrolyte formula to effectively inhibit the formation and accumulation of lithium dendrites, thereby significantly improving the cycle number and charge and discharge rate of lithium metal batteries, and enhancing the performance and safety of the battery.

[0007] The generation and accumulation of lithium dendrites can easily lead to the following problems: (1) Reduced safety: If lithium ions are unevenly deposited, it is easy to cause the generation of lithium dendrites; (2) Reduced cycle life: The continuous consumption of lithium metal will reduce the number of cycles that the battery can be cycled, thereby reducing the battery's service life; (3) Degraded battery performance: The reaction between lithium metal and conventional electrolyte will affect the battery's charge and discharge efficiency, causing the battery's coulombic efficiency to continue to decrease, thereby reducing the battery's performance.

[0008] In response to the above, the inventors of the present invention have discovered through in-depth research that by selecting a new organic solvent and rationally choosing the combination ratio of the organic solvent, lithium salt and specific additives, the cycle number and charge and discharge rate of the lithium metal battery can be significantly improved, further promoting the development of lithium metal battery technology.

[0009] Thus, in one aspect, the present invention provides a composite electrolyte comprising a first lithium salt and a composite solvent;

[0010] The composite solvent comprises ethylene glycol dimethyl ether (DME) and / or 1,3-dioxolane (DOL), and a fluorine-containing ether compound, and the molar ratio of the total of DME and DOL to the fluorine-containing ether compound is 1:0.2-10;

[0011] The fluorine-containing ether compound is represented by the formula R1-O-R2;

[0012] In the formula, R1 is a C1-C10 fluorinated alkyl group or a fluorinated alkoxyalkyl group, and R2 is an arbitrarily fluorinated C1-C5 alkyl group or an alkoxyalkyl group.

[0013] In some embodiments of the present invention, R1 is such as -C n1 F m1 H (2*n1+1-m1) or -C n1 O x1 F m1 H (2*n1+1-m1) As shown in the formula, n1 represents the number of carbon atoms in the R1 group, and is an integer of 1-10, preferably 3-7, and more preferably 3-5; m1 represents the number of fluorine atoms substituted in the R1 group, and is an integer of 3-21, preferably 7-15, and more preferably 7-11; x1 represents the number of alkoxy groups substituted by R1 being a fluoroalkoxyalkyl group, and is an integer of 1-3, preferably 1 or 2.

[0014] In some embodiments of the present invention, R2 is such as -C n2 H (2*n2+1) or -C n2 F m2 H (2*n2+1-m2) , or -C n2 O x2 H (2*n2+1)or -C n2 O x2 F m2 H (2*n2+1-m2) As shown in the formula, n2 represents the number of carbon atoms in the R2 group, and is an integer of 1-5, preferably 1-3; m2 represents the number of fluorine atoms substituted in the R2 group, and is an integer of 0-11, preferably 0-7; x2 represents the number of alkoxy groups substituted by R1, which is a fluoroalkoxyalkyl group, and is an integer of 1-3, preferably 1 or 2.

[0015] In some embodiments of the present invention, the fluorinated ether compound is one or more of perfluoropropyl methyl ether, perfluoroisobutyl methyl ether, perfluoro-n-butyl methyl ether, perfluoropentyl methyl ether, perfluorohexyl methyl ether, perfluoro-3-oxabutyl methyl ether, perfluoro-3,5-dioxahexyl methyl ether, perfluoro-2-oxahexyl methyl ether, ethyl perfluorobutyl ether, perfluorodimethyl ether, perfluoromethyl perfluoroethyl ether, perfluoromethyl perfluoropropyl ether, perfluoromethyl perfluorobutyl ether, perfluoroethyl methyl ether, perfluoroethyl ethyl ether, perfluoroethyl propyl ether, perfluoroethyl butyl ether, perfluoropropyl butyl ether, perfluorobutyl butyl ether, perfluoro-3,5-dioxahexyl methyl ether, perfluoro-3-oxabutyl methyl ether, and perfluoro-2-oxahexyl methyl ether.

[0016] In some embodiments of the present invention, the fluorine-containing ether compound is one or more of perfluoropropyl methyl ether, perfluoroisobutyl methyl ether, ethyl perfluorobutyl ether and perfluoroethylpropyl ether.

[0017] In some embodiments of the present invention, the fluorinated ether compound is perfluoropropyl methyl ether and / or perfluoroisobutyl methyl ether.

[0018] In some embodiments of the present invention, the first lithium salt is selected from one or more of lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), lithium fluorosulfonate (LiFSO3), lithium hexafluoroaluminate (LiAlF6), lithium tetrafluoroborate (LiBF4), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiCF3SO3), lithium tetrafluoroborate (LiBF4) and lithium bis(fluorosulfonyl)imide (LiFSI).

[0019] In some embodiments of the present invention, the composite electrolyte further comprises a second lithium salt and / or an additive.

[0020] Preferably, the second lithium salt is selected from one or more of lithium nitrate (LiNO 3 ), lithium difluorooxalatoborate (LiDFOB), and lithium bis(oxalateborate) (LiBOB).

[0021] Preferably, the additive is selected from one or more of fluoroethylene carbonate (FEC), vinylene carbonate (VC), succinonitrile (SN), methylene methanedisulfonate (MMDS), 1,3-propane sultone (PS), propenyl-1,3-sultone (PST), and dithiothreitol (DTD).

[0022] In some embodiments of the present invention, in the composite electrolyte, the content of the first lithium salt is 0.5-4.5M, preferably 0.7-3M.

[0023] In some embodiments of the present invention, in the composite electrolyte, the content of the second lithium salt is 0.5-5 wt%, preferably 0.7-3 wt%.

[0024] In some embodiments of the present invention, the molar ratio of the total of DME and DOL to the fluorinated ether compound in the composite solvent is 1:1-10, preferably 1:1-5, and more preferably 1:1.8-2.8.

[0025] In some embodiments of the present invention, the volume ratio of DME to DOL in the composite solvent is 1:0.1-10, preferably 1:0.3-5.3, and more preferably 1:0.6-1.6.

[0026] In some embodiments of the present invention, the composite solvent consists of ethylene glycol dimethyl ether (DME), 1,3-dioxolane (DOL) and a fluorine-containing ether compound.

[0027] The second aspect of the present invention provides use of the composite electrolyte according to the first aspect of the present invention in a lithium battery.

[0028] In some embodiments of the present invention, the lithium battery is a lithium metal battery, a lithium ion battery, a lithium sulfur battery or a lithium air battery.

[0029] A third aspect of the present invention provides a lithium battery, comprising a negative electrode, an electrolyte, a separator, and a positive electrode; wherein the electrolyte is the composite electrolyte of the first aspect of the present invention.

[0030] In some embodiments of the present invention, the lithium battery is a lithium metal battery, a lithium ion battery, a lithium sulfur battery or a lithium air battery.

[0031] Advantageous Effects of the Invention

[0032] The composite electrolyte of the present invention has the following technical effects and beneficial effects:

[0033] (1) Significantly Improved Cycle Life: The novel composite electrolyte of this invention promotes uniform deposition of lithium metal, thereby significantly increasing the cycle life of lithium metal batteries. By enhancing the battery's cycle life, this technology will make lithium metal batteries more durable and reliable, reduce the frequency of battery replacement, and lower operating costs.

[0034] (2) Improved charge and discharge rates: The novel composite electrolyte of the present invention can improve the charge and discharge efficiency of batteries, enabling lithium metal batteries to achieve high-rate transmission more quickly during the charge and discharge process. This will enable lithium metal batteries to perform better in high-charge and discharge rate scenarios, meeting the demand for high power output, such as the acceleration performance of electric vehicles and the rapid discharge requirements of energy storage systems.

[0035] (3) Improved battery safety: The novel composite electrolyte of the present invention can effectively inhibit the formation and accumulation of lithium dendrites, reducing the risk of internal short circuits in the battery, thereby improving the safety of lithium metal batteries. Furthermore, the composite electrolyte is non-flammable and has a high safety factor. More reliable battery safety will reduce the probability of accidents during battery use, protecting the safety of users and equipment.

[0036] (4) Promoting high energy density applications: Due to the high energy density of lithium metal batteries, the technology of this invention will promote the development of lithium metal batteries in high energy density applications. This will have a positive impact on electric vehicles, aerospace, energy storage systems and other fields, and promote the innovation and development of related industries.

[0037] (5) Expanding the application prospects of lithium metal batteries: By improving the cycle performance, power output and safety of lithium metal batteries, new electrolytes will create more opportunities for lithium metal batteries to play a role in a wider range of application scenarios. This will further promote the application expansion of lithium metal battery technology and provide more reliable solutions for future energy storage and mobile applications.

[0038] In summary, the composite electrolyte of the present invention has significant technical and beneficial effects in terms of the cycle performance, power output and safety of lithium metal batteries, and is of great significance to promoting the development and application of lithium metal battery technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 shows the impedance data of batteries assembled from the composite electrolytes of Formulation A and Formulation B, respectively.

[0040] FIG2 shows the cycle performance data of batteries assembled from the composite electrolytes of Formula A and Formula B at room temperature.

[0041] FIG3 shows the rate performance data of batteries assembled from the composite electrolytes of Formula A and Formula B at room temperature.

[0042] FIG4 shows the impedance data of batteries assembled from the composite electrolytes of Formulation A, Formulation C, and Formulation D, respectively.

[0043] FIG5 shows the impedance data of batteries assembled from the composite electrolytes of Formulation A and Formulation E, respectively. DETAILED DESCRIPTION

[0044] The present invention will be further described below through specific embodiments. Unless otherwise specified, the technical terms used herein have the same meanings as those generally understood by those skilled in the art.

[0045] As used herein, the term "alkyl" refers to a linear or branched saturated hydrocarbon group. In some embodiments, C1-C5 alkyl includes methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, etc. In some embodiments, the alkyl group of the present invention can be C1-C4 alkyl, C1-C3 alkyl, C1-C2 alkyl, C2-C5 alkyl, C2-C4 alkyl, C2-C3 alkyl, C3-C5 alkyl, C3-C4 alkyl, or C4-C5 alkyl.

[0046] As used herein, the term "fluoroalkyl" refers to a fluorine-substituted linear or branched saturated hydrocarbon group. In some embodiments, the C1-C10 fluoroalkyl group includes a fluorinated methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, hexyl, heptyl, octyl, nonyl, or decyl group. In some embodiments, the number of fluorine atoms in the fluoroalkyl group of the present invention is preferably 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, etc.; the specific number of fluorine atoms can be 1, 2, 3, 4, 5, 6, 7, ... 2n-1, 2n, 2n+1, etc., where n is the number of carbon atoms in the fluoroalkyl group. In some embodiments, the number of hydrogen atoms in the fluoroalkyl group of the present invention is preferably 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or 0.

[0047] As used herein, the term "alkoxyalkyl" refers to an alkyl group substituted with an alkoxy group, such as methoxymethyl, methoxyethyl, ethoxyethyl, etc. In the present invention, the number of carbon atoms in an alkoxyalkyl group refers to the total number of carbon atoms in the alkoxyalkyl group. In the present invention, "fluoroalkoxyalkyl" refers to an alkoxyalkyl group substituted with fluorine.

[0048] In the present invention, "optionally fluorinated" means that the group may or may not contain fluorine substitution.

[0049] Numerical limits or ranges stated herein are inclusive of the endpoints and specifically include all values ​​and subranges within the numerical limits or ranges.

[0050] Existing ether electrolytes have some disadvantages in lithium metal batteries, specifically in the following aspects. (1) Safety risk: Ether electrolytes have a low flash point and flammability. This means that when exposed to external heat sources or internal short circuits in the battery, ether electrolytes may cause fire or explosion. This poses a potential risk to the reliability and safety of lithium metal batteries. (2) Oxidation: Ether electrolytes are easily oxidized under high voltage conditions, which in turn causes thermal runaway and safety problems in the battery. This also limits the reliability and stability of ether electrolytes in applications with high energy density requirements. (3) Evaporation and volatility: Ether electrolytes generally have a high evaporation rate and volatility. During battery cycling and long-term use, the evaporation of the electrolyte will lead to a loss of battery capacity and changes in the electrolyte concentration, thereby reducing battery performance and cycle life. (4) Solubility limitation: Some ether solvents may react with lithium metal and dissolve, resulting in the loss of electrolyte and the desolvation of lithium metal. This may lead to battery capacity decay, shortened cycle life and unstable battery performance. (5) Temperature dependence: The conductivity of ether electrolytes is generally low at low temperatures, which affects the performance and usability of the battery. Under extremely low temperature conditions, ether electrolytes may freeze, causing the battery to not work properly. (6) Inability to withstand wide voltage environments: Commonly used ethers include ethylene glycol dimethyl ether (DME) and 1,3-dioxolane (DOL).

[0051] In response to the above problems, the inventors of the present invention have found that a composite electrolyte including a fluorinated ether compound forms a solid electrolyte interface film (SEI film) rich in lithium fluoride on the surface of the lithium metal negative electrode. Among them, lithium fluoride can help Li + It is uniformly deposited on the surface of the lithium metal negative electrode to form an ordered, neatly arranged cylindrical structure, which improves the coulombic efficiency and cycle stability of the lithium metal battery. The lithium fluoride-rich SEI film effectively inhibits the growth of lithium dendrites and the oxidation of the battery positive electrode in the electrolyte, significantly improving the cycle stability and safety of the lithium metal battery and enhancing the electrochemical performance of the lithium metal battery.

[0052] Specifically, the composite electrolyte of the present invention uses DME and / or DOL as a base solvent, adds a fluorinated ether compound to form a composite solvent, and then combines it with a lithium salt, thereby effectively improving the number of cycles and charge and discharge rates of lithium metal batteries, and overall improving the comprehensive performance of lithium metal batteries such as cycle performance, power output and safety.

[0053] As described above, the first aspect of the present invention provides a composite electrolyte, which comprises a composite lithium salt and a composite solvent; the composite solvent comprises ethylene glycol dimethyl ether (DME) and / or 1,3-dioxolane (DOL), and a fluorinated ether compound, and the molar ratio of the total of DME and DOL to the fluorinated ether compound is 1:0.2-10; the fluorinated ether compound is represented by the formula R1-O-R2; wherein R1 is a C1-C10 fluorinated alkyl or fluorinated alkoxyalkyl, and R2 is an arbitrarily fluorinated C1-C5 alkyl or alkoxyalkyl.

[0054] According to the present invention, by using the fluoroether compound of the present invention, a composite electrolyte capable of improving the cycle performance, power output and safety of a lithium battery is provided.

[0055] In the composite electrolyte of the present invention, the ratio of DME and DOL can be any ratio. In some embodiments, only DME and fluorinated ether compounds can be used, or only DOL and fluorinated ether compounds can be used. The properties of the two materials DME and DOL are relatively similar, and their usage ratio can be determined according to the physical properties (such as viscosity, etc.) required for the composite electrolyte. For example, the volume ratio of DME to DOL in the composite solvent can be 1:0.1-10, 1:0.3-5.3 or 1:0.5-5, etc., such as 1:0.5, 1:1, 1:2, 1:3, 1:4 or 1:5.

[0056] In the present invention, R1 is preferably a fluoroalkyl group having a branched chain, such as fluoroisopropyl, fluoroisobutyl, fluoroisopentyl, etc., and more preferably the branched chain is a perfluoroalkyl group. In the present invention, R2 is preferably an arbitrarily fluorinated alkyl group or alkoxyalkyl group having a branched chain, and more preferably the branched chain is a perfluoroalkyl group.

[0057] In the present invention, R1 is such as -C n1 F m1 H (2*n1+1-m1) (R1 is a fluoroalkyl group) or -C n1 O x1 F m1 H (2*n1+1-m1) (R1 is a fluoroalkoxyalkyl group), wherein n1 represents the number of carbon atoms in the R1 group and is an integer of 1-10; m1 represents the number of fluorine atoms substituted in the R1 group and is an integer of 1-21; x1 represents the number of alkoxy groups substituted by R1 which is a fluoroalkoxyalkyl group, for example, it can be 1, 2 or 3.

[0058] From the perspective of further improving the cycle performance, power output and safety of the lithium battery, n1 is preferably 3-8, more preferably 3-7, further preferably 3-6, and particularly preferably 3-5. From the perspective of further improving the cycle performance, power output and safety of the lithium battery, m1 is preferably 3 to (2*n1+1), more preferably 5 to (2*n1+1), and further preferably 7 to (2*n1+1).

[0059] In addition, in R1 of the present invention, n1 may be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10; and m1 may be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or 21.

[0060] In some specific embodiments, R1 can be, for example, a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluoro-n-butyl group, a perfluoroisobutyl group, a perfluoropentyl group, a perfluorohexyl group, a perfluoroheptyl group, a perfluorononyl group, etc. In some specific embodiments, R1 can be, for example, CH3-O-CF2CF2-O-CF2-, CH3-O-CF2CF2-, CH3-O-CF(C3H7)-CF2-, etc.

[0061] In the present invention, R2 is such as -C n2 H (2*n2+1) or -C n2 F m2 H (2*n2+1-m2) (R2 is alkyl or fluoroalkyl), or -C n2 O x2 H (2*n2+1) or -C n2 O x2 F m2 H (2*n2+1-m2) (R2 is an alkoxyalkyl group or a fluoroalkoxyalkyl group), wherein n2 represents the number of carbon atoms in the R2 group and is an integer of 1-5; m2 represents the number of fluorine atoms substituted in the R2 group and is an integer of 1-11; x2 represents the number of alkoxy groups substituted by R1 which is a fluoroalkoxyalkyl group, for example, it can be 1, 2 or 3.

[0062] From the perspective of further improving the cycle performance, power output, and safety of the lithium battery, n2 is preferably an integer of 1-3, more preferably 1-2, and even more preferably 1. From the perspective of further improving the cycle performance, power output, and safety of the lithium battery, m2 is preferably 1 or more, 2 or more, or 3 or more; preferably 2*n2-2 or less, 2*n2-1 or less, 2*n2 or less, 2*n2+1 or less, etc.

[0063] Furthermore, in R2 of the present invention, n2 may be, for example, 1, 2, 3, 4, or 5; and m2 may be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11.

[0064] In some specific embodiments, R2 can be, for example, methyl, ethyl, propyl, n-butyl, isobutyl, perfluoromethyl, perfluoroethyl, perfluoropropyl, etc.

[0065] Examples of fluorinated ether compounds include perfluoropropyl methyl ether (C3ME, CF3CF2CF2OCH3), perfluoroisobutyl methyl ether (C4ME, (CF3)2CFCF2OCH3), perfluoro-n-butyl methyl ether (CF3CF2CF2CF2OCH3), perfluoropentyl methyl ether (C5ME, for example (CF3)2CFCF(OCH3)CF3), perfluorohexyl methyl ether (C6ME, for example (CF3)2CFCF(OCH3)CF2CF3), perfluoro-3-oxobutyl Methyl ether (X1ME, CF3OCF2CF2OCH3), perfluoro-3,5-dioxahexyl methyl ether (X2ME, CF3OCF2OCF2CF2OCH3), perfluoro-2-oxahexyl methyl ether (6XME, CF3OCF2CF(OCH3)CF(CF3)2), ethyl perfluorobutyl ether (C4FE, such as (CF3)2CFCF2OCH2CH3), perfluorodimethyl ether (CF3OCF3), perfluoromethyl perfluoroethyl ether (CF3CF2OCF3), perfluoromethyl Perfluoropropyl ether (e.g. CF3CF2CF2OCF3), perfluoromethyl perfluorobutyl ether (e.g. (CF3)2CFCF2OCF3, CF3CF2CF2CF2OCF3), perfluoroethyl methyl ether (CF3CF2OCH3), perfluoroethyl ethyl ether (CF3CF2OCH2CH3), perfluoroethyl propyl ether (e.g. CF3CF2OCH2CH2CH3), perfluoroethyl butyl ether (e.g. CF3CF2OCH2CH2CH2CH3, CF3CF2OCH2C H(CH3)2), perfluoropropyl butyl ether (e.g., CF3CF2CF2OCH2CH2CH2CH3, CF3CF2CF2OCH2CH(CH3)2), perfluorobutyl butyl ether (e.g., (CF3)2CFCF2OCH2CH(CH3)2, (CF3)2CFCF2OCH2CH2CH2CH3, CF3CF2CF2CF2OCH2CH(CH3)2, CF3CF2CF2CF2OCH2CH2CH2CH3).

[0066] According to some preferred embodiments of the present invention, the fluorine-containing ether compound is one or more of perfluoropropyl methyl ether, perfluoroisobutyl methyl ether and perfluoropentyl methyl ether.

[0067] In addition, the fluorinated ether compound may account for more than 1% of the total volume of the composite electrolyte. For example, the fluorinated ether compound may account for 1-80% of the total volume of the composite electrolyte.

[0068] According to the present invention, the first lithium salt can use various lithium salts commonly used in lithium battery electrolytes, for example, lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), lithium fluorosulfonate (LiFSO3), lithium hexafluoroaluminate (LiAlF6), lithium tetrafluoroborate (LiBF4), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiCF3SO3), lithium tetrafluoroborate (LiBF4) and lithium bis(fluorosulfonyl)imide (LiFSI). The first lithium salt is preferably LiTFSI, LiFSI, etc.

[0069] From the perspective of improving the cycle performance, power output and safety of lithium metal batteries, preferably, in the composite electrolyte, the content of the first lithium salt is 0.5-4.5M, preferably 0.7-3M, and more preferably 0.8-1.5M.

[0070] According to the present invention, the composite electrolyte optionally further comprises a second lithium salt, which may be selected from one or more of lithium nitrate (LiNO 3 ), lithium difluorooxalatoborate (LiDFOB), lithium bis(oxalateborate) (LiBOB) and lithium fluoride (LiF).

[0071] From the perspective of improving the cycle performance, power output and safety of lithium metal batteries, preferably, in the composite electrolyte, the content of the second lithium salt is 0.5-5wt%, more preferably 0.7-3wt%, and further preferably 0.8-2wt%.

[0072] According to the present invention, the composite electrolyte may further optionally contain an additive, and the additive may be selected from one or more of fluoroethylene carbonate (FEC), vinylene carbonate (VC), succinonitrile (SN), methylene methanedisulfonate (MMDS), 1,3-propane sultone (PS), propenyl-1,3-sultone (PST), and diethylene sulfate (DTD).

[0073] From the perspective of improving the cycle performance, power output and safety of lithium metal batteries, preferably, in the composite electrolyte, the content of the additive is 0.5-5wt%, more preferably 0.7-3wt%, and even more preferably 0.8-2wt%.

[0074] In order to further improve the cycle performance, power output, and safety of lithium metal batteries, preferably, the volume ratio of DME to DOL in the composite solvent is 1:0.5-1.5, preferably 1:0.8-1.2, and more preferably 1:0.9-1.1. Furthermore, preferably, the molar ratio of the total of DME and DOL to the fluorinated ether compound in the composite solvent is 1:1-10, preferably 1:1-5, more preferably 1:1-3, and even more preferably 1:1.8-2.8.

[0075] According to some preferred embodiments of the present invention, the fluorinated ether compound is perfluoropropyl methyl ether and / or perfluoroisobutyl methyl ether, more preferably perfluoroisobutyl methyl ether or a mixture of perfluoropropyl methyl ether and perfluoroisobutyl methyl ether. According to some preferred embodiments of the present invention, the fluorinated ether compound is a mixture of perfluoropropyl methyl ether and perfluoroisobutyl methyl ether, and the volume ratio of perfluoroisobutyl methyl ether to perfluoropropyl methyl ether is 1:0.1-10, preferably 1:0.5-5, more preferably 1:1-2.

[0076] According to some preferred embodiments of the present invention, the composite solvent is composed of ethylene glycol dimethyl ether (DME), 1,3-dioxolane (DOL) and a fluorine-containing ether compound.

[0077] The composite electrolyte of the present invention can be prepared by, for example, using DME or DOL alone, or by mixing DME and DOL in appropriate proportions and then further mixing them with a fluorinated ether compound to form a composite solvent. Lithium nitrate and a first lithium salt are then dissolved in the composite solvent at appropriate concentrations to obtain the composite electrolyte of the present invention. During the mixing process, heating (e.g., low-temperature heating at 40-50° C.) can be performed as needed to promote dissolution of the relevant components.

[0078] The second aspect of the present invention provides use of the composite electrolyte according to the first aspect of the present invention in a lithium battery.

[0079] A third aspect of the present invention provides a lithium battery, comprising a negative electrode, an electrolyte, a separator, and a positive electrode; wherein the electrolyte is the composite electrolyte of the first aspect of the present invention.

[0080] In the second and third aspects of the present invention described above, there is no particular limitation on the type of lithium battery, and the type may be, for example, a lithium metal battery, a lithium ion battery, a lithium sulfur battery, or a lithium air battery, with lithium metal batteries being preferred. The composite electrolyte of the present invention, when used in a lithium metal battery, can particularly improve various aspects of the performance of the lithium metal battery.

[0081] In addition, the lithium battery is preferably a lithium battery to which lithium replenishment technology is applied.

[0082] In the lithium battery of the present invention, the negative electrode may include a negative electrode active material capable of releasing and accepting lithium ions. For example, the negative electrode active material may be lithium metal, a lithium alloy, or a carbon material doped or undoped with lithium ions.

[0083] In some specific embodiments, the negative electrode active material is lithium metal. Preferably, the thickness of the lithium metal sheet is 5-50 μm, preferably 5-20 μm.

[0084] In some embodiments, the negative electrode active material is a carbon material doped or undoped with lithium ions. Such a carbon material can be graphite or amorphous carbon, and any carbonaceous material such as activated carbon, carbon fiber, carbon black, medium carbon microbeads, etc. can be used.

[0085] In the lithium battery of the present invention, the positive electrode may include a positive electrode active material capable of releasing and accepting lithium ions.

[0086] In some embodiments, the positive electrode active material can be a composite oxide or sulfide of lithium and transition metal (such as MnO2, V2O 5、 MoS2, TiS2, etc.). Among them, the composite oxides used as positive electrode active materials include LiCoO2, LiMnO2, LiMn2O4, LiNiO2, etc.

[0087] In some specific embodiments, the positive electrode active material is a nickel-cobalt-manganese ternary positive electrode material (such as NCM111, NCM523, NCM622, and NCM811), a nickel-cobalt-aluminum ternary positive electrode material NCA (commonly in a ratio of 8:1.5:0.5), a lithium iron phosphate positive electrode material, a lithium iron manganese phosphate positive electrode material, etc. Preferably, the positive electrode active material of the present invention is a high-nickel ternary positive electrode material or a lithium iron phosphate positive electrode material.

[0088] In the lithium battery of the present invention, the separator is not particularly limited. For example, various separators commonly used in lithium batteries of the present invention can be used. From the perspective of combining with the composite electrolyte to obtain higher battery performance, the separator of the present invention can be a PE film or a PP film.

[0089] In the present invention, there is no particular limitation on the shape and style of the lithium battery. The lithium battery of the present invention can be cylindrical, square, coin-shaped, card-shaped, large-sized or similar shapes. Within the scope of the present invention, the specific shape can be selected as needed.

[0090] Since the non-aqueous electrolyte battery of the present invention contains the above-mentioned non-aqueous electrolyte as an electrolyte, it can be used as a non-aqueous rechargeable battery that can generate a high voltage and whose battery performance does not deteriorate even after repeated charge and discharge.

[0091] Example

[0092] The experimental methods in the following examples are conventional methods unless otherwise specified. The reagents used in the following examples are commercially available unless otherwise specified.

[0093] In the following examples and comparative examples, the abbreviations of the relevant compounds are as follows.

[0094] LiTFSI: lithium bis(trifluoromethanesulfonyl)imide

[0095] DME: Ethylene glycol dimethyl ether

[0096] DOL: 1,3-dioxolane

[0097] In each formulation of the following examples and comparative examples, the structural formulas of the relevant compounds are shown in Table 1 below.

[0098] Table 1

[0099] Comparative Example 1

[0100] This example is used to illustrate the preparation method of a comparative composite electrolyte. The composition of the comparative composite electrolyte is as follows, also referred to as Formula A herein.

[0101] Solvent: DME / DOL composite solvent with a volume ratio of 1:1

[0102] Lithium salt: 1.2M LiTFSI, 1wt% LiNO3 (both final concentrations, the same below)

[0103] Example 1

[0104] This example is used to illustrate the preparation method of the composite electrolyte of the present invention. The composition of the composite electrolyte is as follows, also referred to as Formulation B herein.

[0105] Solvent: a composite solvent consisting of a DME / DOL mixture (the volume ratio of DME / DOL in the mixture is 1:1) and perfluoroisobutyl methyl ether, wherein the molar ratio of the DME / DOL mixture to the perfluoroisobutyl methyl ether is 1:2.

[0106] Lithium salt: 1.2 M LiTFSI, 1 wt% LiNO3.

[0107] Example 2

[0108] This example is used to illustrate the preparation method of the composite electrolyte of the present invention. The composition of the composite electrolyte is as follows, also referred to as Formulation C herein.

[0109] Solvent: A composite solvent consisting of a DME / DOL mixture (the volume ratio of DME / DOL in the mixture is 1:1) and a perfluoroisobutyl methyl ether / perfluoropropyl methyl ether mixture (the volume ratio of perfluoroisobutyl methyl ether / perfluoropropyl methyl ether in the mixture is 1:1), wherein the molar ratio of the DME / DOL mixture to the perfluoroisobutyl methyl ether / perfluoropropyl methyl ether mixture is 1:2.

[0110] Lithium salt: 1.2 M LiTFSI, 1 wt% LiNO3.

[0111] Example 3

[0112] This example is used to illustrate the preparation method of the composite electrolyte of the present invention. The composition of the composite electrolyte is as follows, also referred to as Formulation D herein.

[0113] Solvent: A composite solvent consisting of a DME / DOL mixture (the volume ratio of DME / DOL in the mixture is 1:1) and a perfluoroisobutyl methyl ether / perfluoropropyl methyl ether mixture (the volume ratio of perfluoroisobutyl methyl ether / perfluoropropyl methyl ether in the mixture is 1:2), wherein the molar ratio of the DME / DOL mixture to the perfluoroisobutyl methyl ether / perfluoropropyl methyl ether mixture is 1:2.

[0114] Lithium salt: 1.2 M LiTFSI, 1 wt% LiNO3.

[0115] Example 4

[0116] This example is used to illustrate the preparation method of the composite electrolyte of the present invention. The composition of the composite electrolyte is as follows, also referred to as Formulation E herein.

[0117] Solvent: a composite solvent consisting of a DME / DOL mixture (the volume ratio of DME / DOL in the mixture is 1:1) and perfluoropentyl methyl ether, wherein the molar ratio of the DME / DOL mixture to the perfluoropentyl methyl ether is 1:2.

[0118] Lithium salt: 1.2 M LiTFSI, 1 wt% LiNO3.

[0119] Example 5

[0120] This example is used to illustrate the preparation method of the composite electrolyte of the present invention. The composition of the composite electrolyte is as follows, also referred to as Formula F herein.

[0121] Solvent: a composite solvent consisting of a DME / DOL mixture (the volume ratio of DME / DOL in the mixture is 1:1) and perfluoropropyl methyl ether, wherein the molar ratio of the DME / DOL mixture to the perfluoropropyl methyl ether is 1:2.

[0122] Lithium salt: 1.2 M LiTFSI, 1 wt% LiNO3.

[0123] Example 6

[0124] This example is used to illustrate the preparation method of the composite electrolyte of the present invention. The composition of the composite electrolyte is as follows, also referred to as Formulation G herein.

[0125] Solvent: a composite solvent consisting of a DME / DOL mixture (the volume ratio of DME / DOL in the mixture is 1:1) and perfluoroisobutyl methyl ether, wherein the molar ratio of the DME / DOL mixture to the perfluoroisobutyl methyl ether is 1:1.

[0126] Lithium salt: 1.2 M LiTFSI, 1 wt% LiNO3.

[0127] Example 7

[0128] This example is used to illustrate the preparation method of the composite electrolyte of the present invention. The composition of the composite electrolyte is as follows, also referred to as Formula H herein.

[0129] Solvent: a composite solvent consisting of a DME / DOL mixture (the volume ratio of DME / DOL in the mixture is 1:1) and perfluoroisobutyl methyl ether, wherein the molar ratio of the DME / DOL mixture to the perfluoroisobutyl methyl ether is 1:3.

[0130] Lithium salt: 1.2 M LiTFSI, 1 wt% LiNO3.

[0131] Example 8

[0132] This example is used to illustrate the preparation method of the composite electrolyte of the present invention. The composition of the composite electrolyte is as follows, also referred to as Formula I herein.

[0133] Solvent: a composite solvent consisting of a DME / DOL mixture (the volume ratio of DME / DOL in the mixture is 2:1) and perfluoroisobutyl methyl ether, wherein the molar ratio of the DME / DOL mixture to the perfluoroisobutyl methyl ether is 1:2.

[0134] Lithium salt: 1.2 M LiTFSI, 1 wt% LiNO3.

[0135] Example 9

[0136] This example is used to illustrate the preparation method of the composite electrolyte of the present invention. The composition of the composite electrolyte is as follows, also referred to as Formula J herein.

[0137] Solvent: a composite solvent consisting of a DME / DOL mixed solution (the volume ratio of DME / DOL in the mixed solution is 1:2) and perfluoroisobutyl methyl ether, wherein the molar ratio of the DME / DOL mixed solution to the perfluoroisobutyl methyl ether is 1:2.

[0138] Lithium salt: 1.2 M LiTFSI, 1 wt% LiNO3.

[0139] Example 10

[0140] This example is used to illustrate the preparation method of the composite electrolyte of the present invention. The composition of the composite electrolyte is as follows, also referred to as Formulation K herein.

[0141] Solvent: a composite solvent consisting of a DME / DOL mixture (the volume ratio of DME / DOL in the mixture is 1:1) and perfluoro-3-oxobutyl methyl ether, wherein the molar ratio of the DME / DOL mixture to the perfluoro-3-oxobutyl methyl ether is 1:2.

[0142] Lithium salt: 1.2 M LiTFSI, 1 wt% LiNO3.

[0143] Example 11

[0144] This example is used to illustrate the preparation method of the composite electrolyte of the present invention. The composition of the composite electrolyte is as follows, also referred to as Formula L herein.

[0145] Solvent: a composite solvent consisting of a DME / DOL mixture (the volume ratio of DME / DOL in the mixture is 1:1) and ethyl perfluorobutyl ether, wherein the molar ratio of the DME / DOL mixture to the ethyl perfluorobutyl ether is 1:2.

[0146] Lithium salt: 1.2 M LiTFSI, 1 wt% LiNO3.

[0147] Example 12

[0148] This example is used to illustrate the preparation method of the composite electrolyte of the present invention. The composition of the composite electrolyte is as follows, also referred to as Formulation M herein.

[0149] Solvent: a composite solvent consisting of a DME / DOL mixed solution (the volume ratio of DME / DOL in the mixed solution is 1:1) and perfluoroethyl propyl ether, wherein the molar ratio of the DME / DOL mixed solution to the perfluoroethyl propyl ether is 1:2.

[0150] Lithium salt: 1.2 M LiTFSI, 1 wt% LiNO3.

[0151] Test Example 1

[0152] Batteries were assembled using the composite electrolytes of Comparative Example 1 and Examples 1-4. The positive electrode used NCM811 ternary material with a loading capacity of 3.2 mAh / cm 2 ; The negative electrode uses 20μm lithium metal; the separator uses PE film.

[0153] The assembled battery was subjected to AC impedance testing using an electrochemical workstation with a 10mV amplitude voltage and a test frequency range of 0.1Hz-100kHz. The measured data is the impedance value. Battery cycle testing was also performed using a Xinwei battery cycle tester under 0 / 5C charging and 1C discharging conditions. Detailed results are shown in Table 2.

[0154] Table 2

[0155] Figure 1 shows the impedance data of batteries assembled with composite electrolytes from Formulations A and B, respectively. The batteries were stored for 24 hours and then tested using a 0.5C charge and 1C discharge test standard. The impedance of Formulation A is significantly higher than that of Formulation B, indicating that Formulation B is more stable to lithium metal than Formulation A, forming a thinner SEI film or having higher ionic conductivity.

[0156] Figure 2 shows the cycling performance data of batteries assembled with the composite electrolytes of Formulations A and B at room temperature. The batteries were stored for 24 hours and then tested using a 0.33C charge and 1C discharge test standard. The comparison shows that Formulation B is far more stable than Formulation A due to its ability to form a stable SEI film. Furthermore, Formulation B can improve the cycling performance of batteries by at least 10-15 times, significantly improving and commercializing lithium metal batteries.

[0157] Figure 3 shows the rate performance data of batteries assembled from composite electrolytes of Formula A and Formula B at room temperature. The batteries were stored for 24 hours and then tested using a 0.33C charge and discharge test standard of different rates (0.2C, 0.5C, 1C, 2C, and 0.5C). The rate performance data obtained show that the stability of Formula B is far better than that of Formula A because Formula B can form a stable SEI film. In addition, Formula B can greatly improve the rate performance of lithium metal batteries compared to Formula A, indicating that the formed SEI film is stable and is not damaged or can be repaired in a timely manner during high-rate discharge, allowing lithium ions to be deposited more evenly.

[0158] Figure 4 shows the impedance data of batteries assembled from composite electrolytes of Formula A, Formula C, and Formula D, respectively. The batteries were tested after being stored for 24 hours, using a 0.5C charge and 1C discharge test standard. The impedance of Formula A is significantly higher than that of Formula C and Formula D, indicating that the fluorinated ether additives in Formula C and Formula D can significantly reduce the impedance of the common ether DME / DOL in the battery, and are more stable to lithium metal than Formula A, and the SEI film formed is thinner or has better ion conductivity. The impedance of Formula D is slightly lower than that of Formula C, and the viscosity of Formula D is greater than that of Formula C. This shows that in lithium metal batteries, electrolytes with slightly higher viscosities are more stable to lithium metal and form a more uniform SEI film.

[0159] Figure 5 shows the impedance data of batteries assembled from composite electrolytes of Formula A and Formula E, respectively. The batteries were tested after 24 hours of storage, using a 0.5C charge and 1C discharge test standard. The impedance of Formula A is significantly higher than that of Formula E, indicating that Formula E is still significantly better than the common ether formula DME / DOL in lithium metal batteries. Compared with Formula A, it is more stable to lithium metal, and the SEI film formed is thinner or has better ion conductivity. Compared with Formulas B, C, and D, the impedance of Formula E has increased, indicating that the impedance of the formed SEI film is not as low as that of perfluoroisobutyl methyl ether and perfluoropropyl methyl ether.

[0160] From the results in Table 1 and Figures 1-5, it can be seen that the composite electrolyte of the present invention can significantly increase the number of cycles of lithium metal batteries and reduce the impedance of the battery. Specifically, by comparing Examples 1-5 and 10-12, it can be seen that when perfluoroisobutyl methyl ether, perfluoropropyl methyl ether, ethyl perfluorobutyl ether and perfluoroethyl propyl ether are used as fluorinated ether compounds, the number of cycles of lithium metal batteries can be further increased and the impedance of the battery can be reduced. By comparing Examples 1 and 6-9, it can be seen that when the molar ratio of the DME / DOL mixed solution to the fluorinated ether compound is 1:1.8-2.8, and / or the volume ratio of DME to DOL is 1:0.6-1.6, the number of cycles of lithium metal batteries can be further increased and the impedance of the battery can be reduced.

[0161] The above examples are used to describe exemplary embodiments of the present invention, but the present invention is not limited thereto. It should be understood by those skilled in the art that the above examples are for illustrative purposes only, and the specific embodiments and examples of the present invention should not be construed as limiting the scope of the present invention. The embodiments can be changed and modified within the scope of the present invention, and such changes and modifications should fall within the scope of protection of the present invention.

Claims

1. A composite electrolyte, characterized in that: The composite electrolyte comprises a first lithium salt and a composite solvent; The composite solvent comprises ethylene glycol dimethyl ether (DME) and / or 1,3-dioxolane (DOL), and a fluorine-containing ether compound, and the molar ratio of the total of DME and DOL to the fluorine-containing ether compound is 1:0.2-10; The fluorine-containing ether compound is represented by the formula R1-O-R2; In the formula, R1 is a C1-C10 fluorinated alkyl group or a fluorinated alkoxyalkyl group, and R2 is an arbitrarily fluorinated C1-C5 alkyl group or an alkoxyalkyl group.

2. The composite electrolyte according to claim 1, wherein R1 as-C n1 F m1 H (2*n1+1-m1) or -C n1 O x1 F m1 H (2*n1+1-m1) As shown in the formula, n1 represents the number of carbon atoms in the R1 group, and is an integer of 1-10, preferably 3-7, and more preferably 3-5; m1 represents the number of fluorine atoms substituted in the R1 group, and is an integer of 3-21, preferably 7-15, and more preferably 7-11; x1 represents the number of alkoxy substitutions of R1 as a fluoroalkoxyalkyl group, and is an integer of 1-3, preferably 1 or 2.

3. The composite electrolyte according to claim 1, wherein R2 as -C n2 H (2*n2+1) or -C n2 F m2 H (2*n2+1-m2) , or -C n2 O x2 H (2*n2+1) or -C n2 O x2 F m2 H (2*n2+1-m2) As shown in the formula, n2 represents the number of carbon atoms in the R2 group, and is an integer of 1-5, preferably 1-3; m2 represents the number of fluorine atoms substituted in the R2 group, and is an integer of 0-11, preferably 0-7; x2 represents the number of alkoxy substitutions of R1 as a fluoroalkoxyalkyl group, and is an integer of 1-3, preferably 1 or 2.

4. The composite electrolyte according to claim 1, wherein The fluorinated ether compound is one or more of perfluoropropyl methyl ether, perfluoroisobutyl methyl ether, perfluoro-n-butyl methyl ether, perfluoropentyl methyl ether, perfluorohexyl methyl ether, perfluoro-3-oxabutyl methyl ether, perfluoro-3,5-dioxahexyl methyl ether, perfluoro-2-oxahexyl methyl ether, ethyl perfluorobutyl ether, perfluorodimethyl ether, perfluoromethyl perfluoroethyl ether, perfluoromethyl perfluoropropyl ether, perfluoromethyl perfluorobutyl ether, perfluoroethyl methyl ether, perfluoroethyl ethyl ether, perfluoroethyl propyl ether, perfluoroethyl butyl ether, perfluoropropyl butyl ether and perfluorobutyl butyl ether.

5. The composite electrolyte according to claim 1, wherein The fluorine-containing ether compound is one or more of perfluoropropyl methyl ether, perfluoroisobutyl methyl ether, ethyl perfluorobutyl ether and perfluoroethylpropyl ether.

6. The composite electrolyte according to claim 5, wherein: The fluorine-containing ether compound is perfluoropropyl methyl ether and / or perfluoroisobutyl methyl ether.

7. The composite electrolyte according to any one of claims 1 to 6, wherein: The first lithium salt is selected from one or more of lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), lithium fluorosulfonate (LiFSO3), lithium hexafluoroaluminate (LiAlF6), lithium tetrafluoroborate (LiBF4), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiCF3SO3), lithium tetrafluoroborate (LiBF4) and lithium bis(fluorosulfonyl)imide (LiFSI).

8. The composite electrolyte according to claim 7, wherein: The composite electrolyte further comprises a second lithium salt and / or an additive; Preferably, the second lithium salt is selected from one or more of lithium nitrate (LiNO3), lithium difluorooxalatoborate (LiDFOB), lithium bis(oxalateborate) (LiBOB), and lithium fluoride (LiF); Preferably, the additive is selected from one or more of fluoroethylene carbonate (FEC), vinylene carbonate (VC), succinonitrile (SN), methylene methanedisulfonate (MMDS), 1,3-propane sultone (PS), propenyl-1,3-sultone (PST), and diethylene sulfate (DTD).

9. The composite electrolyte according to claim 8, wherein: In the composite electrolyte, the content of the first lithium salt is 0.5-4.5M, preferably 0.7-3M; and / or The content of the second lithium salt is 0.5-5wt%, preferably 0.7-3wt%.

10. The composite electrolyte according to any one of claims 1 to 6, wherein: The molar ratio of the total of DME and DOL to the fluorine-containing ether compound in the composite solvent is 1:1-10, preferably 1:1-5, more preferably 1:1.8-2.8; Preferably, the volume ratio of DME to DOL in the composite solvent is 1:0.1-10, preferably 1:0.3-5.3, and more preferably 1:0.6-1.

6.

11. The composite electrolyte according to any one of claims 1 to 6, wherein: The composite solvent consists of ethylene glycol dimethyl ether (DME), 1,3-dioxolane (DOL) and fluorine-containing ether compounds.

12. Use of the composite electrolyte according to any one of claims 1 to 11 in a lithium battery.

13. The use according to claim 12, wherein: The lithium battery is a lithium metal battery, a lithium ion battery, a lithium sulfur battery or a lithium air battery.

14. A lithium battery, characterized in that: The lithium battery comprises a negative electrode, an electrolyte, a separator, and a positive electrode; wherein the electrolyte is the composite electrolyte according to any one of claims 1 to 11.

15. The lithium battery according to claim 14, wherein: The lithium battery is a lithium metal battery, a lithium ion battery, a lithium sulfur battery or a lithium air battery.

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