Electrolyte and lithium ion battery

Abstract

The invention relates to the technical field of lithium ion batteries, and discloses an electrolyte and a lithium ion battery. The electrolyte comprises a carbonic ester solvent and a carboxylic ester solvent, and the mass ratio of the carbonic ester solvent to the carboxylic ester solvent is (7: 3)-(9: 1); the composite additive comprises a first functional additive and a second functional additive, the mass of the composite additive accounts for 2%-8% of the total mass of the electrolyte, the mass ratio of the first functional additive to the second functional additive is (1: 10)-(10: 1), the first functional additive comprises vinylene carbonate, fluoroethylene carbonate, 1, 2, 4-trimethyl-1, 3-pentanediol monoisobutyrate, and the second functional additive comprises vinylene carbonate, fluoroethylene carbonate, 1, 2, 4-trimethyl-1, 3-pentanediol monoisobutyrate and 1, 2, 4-trimethyl-1, 3-pentanediol monoisobutyrate. The first functional additive comprises any one of 1, 3-propane sultone, and the second functional additive comprises at least one of ethylene sulfate and lithium difluorophosphate. The electrolyte provided by the invention is helpful for improving the fast charging performance of the lithium ion battery and the electrical performance at a low temperature.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, specifically to electrolytes and lithium-ion batteries. Background Technology

[0002] With the continuous promotion of the new energy vehicle market, range anxiety has become a pressing issue affecting the user experience of new energy vehicles. Given relatively limited battery capacity, improving the charging rate of the battery system and shortening charging time are key ways to address range anxiety. Therefore, improving the fast-charging performance of batteries is an urgent need to improve the user experience of new energy vehicles. Furthermore, in northern my country, the battery performance of new energy vehicles is significantly affected by low winter temperatures. For example, lithium iron phosphate (LFP) lithium-ion batteries experience a significant reduction in discharge energy at low temperatures, severely limiting the promotion and application of new energy vehicles in vast northern regions. Therefore, comprehensive improvement of lithium-ion battery performance requires not only consideration of improving fast-charging performance but also its charge and discharge capabilities under low-temperature conditions. The performance of the electrolyte has a significant impact on the fast-charging and low-temperature performance of lithium-ion batteries, requiring further research and development.

[0003] It should be noted that the above statements are only used to provide background information related to this application and do not necessarily constitute prior art. Summary of the Invention

[0004] In a first aspect, this application proposes an electrolyte comprising: a carbonate solvent and a carboxylic acid ester solvent, wherein the mass ratio of the carbonate solvent to the carboxylic acid ester solvent is (7:3)-(9:1); and a composite additive comprising a first functional additive and a second functional additive, wherein the composite additive accounts for 2%-8% of the total mass of the electrolyte, and the mass ratio of the first functional additive to the second functional additive is (1:10)-(10:1). The first functional additive comprises any one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), and 1,3-propanesulfonate lactone (PS), and the second functional additive comprises at least one of vinyl sulfate (DTD) and lithium difluorophosphate (LiPO2F2). Therefore, the electrolyte proposed in this application exhibits high low-temperature chemical stability and ionic conductivity, and can improve the low-temperature performance and fast-charging performance of the battery while maintaining battery life.

[0005] In some embodiments, the carbonate solvent includes at least two of ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), propylene carbonate (PC), and diethyl carbonate (DEC); and / or, the carboxylic acid ester solvent includes at least one of ethyl acetate (EA), ethyl propionate (EP), and methyl propionate (MP). This is beneficial for reducing the viscosity of the electrolyte, increasing the transport rate of lithium ions in the electrolyte, and improving the wettability of the electrolyte to the electrodes, thereby enhancing the cycle performance and fast-charging performance of the lithium-ion battery.

[0006] In some embodiments, the first functional additive accounts for 0.3%-6% of the total mass of the electrolyte; and / or, the second functional additive accounts for 0.5%-3% of the total mass of the electrolyte. Thus, the functional additive can form a highly stable SEI film with lithium ions and groups in the electrolyte such as carboxylic acid esters.

[0007] In some embodiments, the vinylene carbonate accounts for 0.5%-3% of the total mass of the electrolyte; and / or, the fluoroethylene carbonate accounts for 0.5%-1.5% of the total mass of the electrolyte; and / or, the 1,3-propanesulfonate lactone accounts for 0.5%-1% of the total mass of the electrolyte. This improves the SEI film formation stability and ionic conductivity, which is beneficial for enhancing the cycle stability of lithium-ion batteries during charge and discharge.

[0008] In some embodiments, the vinyl sulfate (DTD) accounts for 0.5%-1.5% of the total mass of the electrolyte; and / or, the lithium difluorophosphate (LiPO2F2) accounts for 0.2%-1% of the total mass of the electrolyte. This can improve the migration rate of lithium ions in the electrolyte, which is beneficial for improving the fast-charging performance of lithium-ion batteries.

[0009] In some embodiments, the electrolyte further includes a lithium salt, comprising a first lithium salt and a second lithium salt, wherein the first lithium salt comprises LiPF6 and the second lithium salt comprises at least one of LiFSI, LiTFSI, and LiBF4, and the lithium salt accounts for 8%-20% of the total mass of the electrolyte. Thus, the electrolyte exhibits excellent lithium-ion transport capability over a wide temperature range, thereby significantly improving the power characteristics and low-temperature performance of the lithium-ion battery.

[0010] In some embodiments, the concentration of the first lithium salt is 0.5 mol / L to 1.5 mol / L; and / or, the concentration of the second lithium salt is 0.05 mol / L to 0.5 mol / L. Thus, the lithium salt in the electrolyte can dissociate to generate sufficient mobile lithium ions, resulting in a high ionic conductivity in the electrode solution.

[0011] In some embodiments, the LiFSI accounts for 5%-50% of the total mass of the lithium salt; and / or, the LiTFSI accounts for 2%-25% of the total mass of the lithium salt; and / or, the LiBF4 accounts for 2%-15% of the total mass of the lithium salt; and / or, the LiPF6 accounts for 10%-80% of the total mass of the lithium salt. This improves the migration ability of lithium ions in the electrolyte, which is beneficial for enhancing the electrochemical performance of lithium-ion batteries during high-power charge and discharge processes and reducing the impact of temperature on their electrical performance.

[0012] In some embodiments, the viscosity of the electrolyte is 0.5 mPa·s to 8 mPa·s at temperatures ranging from -30°C to 65°C. This is beneficial for improving the charge-discharge capability of lithium-ion batteries at different temperatures.

[0013] In a second aspect, this application proposes a lithium-ion battery comprising the electrolyte proposed in this application. Therefore, the lithium-ion battery proposed in this application exhibits high charge-discharge rates at both room temperature and low temperatures, and also demonstrates superior cycle performance. Attached Figure Description

[0014] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0015] Figure 1 The results are the cyclic test results of Examples 2, 4 and Comparative Example 1 of this application. Detailed Implementation

[0016] The embodiments of this application are described in detail below, with examples of these embodiments shown in the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0017] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit this application; unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0018] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are open-ended expressions, meaning they include what is specified in this application but do not exclude other aspects.

[0019] In the description of this application, all figures disclosed herein, whether or not the words "approximately" or "about" are used, are approximate values. Each figure may vary by less than 10% or by a difference that is considered reasonable by one of the art, such as 1%, 2%, 3%, 4%, or 5%.

[0020] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0021] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0022] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0023] Related technologies primarily improve battery low-temperature performance and fast-charging capabilities by using low-viscosity, low-melting-point solvents in the electrolyte. However, these solvents exhibit poor electrochemical stability, weak oxidation and reduction resistance, and are prone to decomposition at high voltages or low potentials, leading to rapid degradation of battery cycle life. Furthermore, these low-viscosity solvents are highly volatile, making the electrolyte susceptible to decomposition during lithium-ion battery cycling. Electrolyte loss can cause the electrolyte to dry out at high temperatures, resulting in increased internal pressure in the lithium-ion battery, leading to leakage or bulging, thus causing cycle degradation and safety hazards. At low temperatures, the lithium-ion transport capacity of the aforementioned electrolytes also decreases with decreasing temperature, failing to meet the requirements for low-temperature battery performance.

[0024] In a first aspect of this application, an electrolyte is provided, comprising: a carbonate solvent and a carboxylic acid ester solvent, wherein the mass ratio of the carbonate solvent to the carboxylic acid ester solvent is (7:3)-(9:1); and a composite additive, wherein the composite additive comprises a first functional additive and a second functional additive, wherein the composite additive accounts for 2%-8% of the total mass of the electrolyte, and the mass ratio of the first functional additive to the second functional additive is (1:10)-(10:1), wherein the first functional additive comprises any one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), and 1,3-propanesulfonic acid lactone (PS), and the second functional additive comprises at least one of vinyl sulfate (DTD) and lithium difluorophosphate (LiPO2F2).

[0025] The electrolyte proposed in this application includes a composite solvent of carbonate solvent and carboxylic acid ester solvent. When the carboxylic acid ester solvent and carbonate solvent are combined within the mass ratio range of this application, the carbonyl oxygen in the carboxylic acid ester solvent molecule can form a superior dipole interaction with the carbon atoms of the carbonate. This reduces the viscosity and freezing point of the electrolyte, while the composite solvent in the electrolyte also exhibits high chemical stability and low internal resistance. Consequently, the composite solvent in the electrolyte can maintain a high lithium-ion transport capacity over a wide temperature range (e.g., -30°C to 65°C), which is beneficial for its continuous and stable function in establishing the lithium-ion transport pathway in the lithium-ion battery. Therefore, it helps to improve the fast-charging performance and low-temperature discharge capacity of the lithium-ion battery.

[0026] Furthermore, the carboxylic acid ester molecules, the first functional additive, and the second functional additive in the aforementioned mixed composite solvent, within the ratio range proposed in this application, can cooperate in the formation of the solid electrolyte interphase (SEI) film at the contact interface between the electrolyte and the negative electrode. The aforementioned ratio of composite solvent gives the electrolyte good lithium salt dissociation ability, good dispersibility of the functional additives, and improved wettability of the electrolyte to the electrode. Therefore, the electrolyte has a superior wetting effect on the electrode, which can assist the first and second functional additives in improving the flexibility and mechanical strength of the SEI film, thereby significantly improving the stability of the organic-inorganic composite film layer composed of the negative electrode and the SEI film layer, suppressing electrolyte decomposition and gas generation and lithium ion loss caused by repeated SEI film formation, and improving the cycle performance and system stability during the charge and discharge process of the lithium-ion battery.

[0027] In summary, the electrolyte proposed in this application improves the wettability of lithium-ion battery electrodes, adjusts the physicochemical properties such as boiling point and freezing point, enhances high-temperature stability and low-temperature lithium-ion transport capacity, and achieves the effects of reducing decomposition gas production and improving SEI film stability. Thus, in lithium-ion batteries, it can improve the fast charging and low-temperature capabilities of the battery while taking into account cycle life.

[0028] In some embodiments, the carbonate solvent includes at least two of ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), propylene carbonate (PC), and diethyl carbonate (DEC); and / or, the carboxylic acid ester solvent includes at least one of ethyl acetate (EA), ethyl propionate (EP), and methyl propionate (MP). Mixing the aforementioned carboxylic acid ester solvent and the aforementioned carbonate solvent in the mass ratio proposed in this application can preferably reduce the viscosity and freezing point of the electrolyte, and a relatively stable interaction can be formed between the two types of molecules. This is beneficial for improving the wettability of the electrolyte to the lithium-ion battery electrodes at both room temperature and low temperature. By adjusting the boiling point of the composite solvent in the electrolyte, the decomposition and gas generation of the electrolyte during battery cycling is reduced, and the high-temperature stability and low-temperature fluidity of the electrolyte are improved, thereby enhancing the cycle performance of the battery and improving the low-temperature performance and fast-charging performance of the lithium-ion battery.

[0029] In some embodiments, the first functional additive accounts for 0.3%-6% of the total mass of the electrolyte; and / or, the second functional additive accounts for 0.5%-3% of the total mass of the electrolyte. Thus, the first and second functional additives can be fully dissolved and dispersed in the composite solvent of the electrolyte, allowing their functional molecules to form a highly stable SEI film with lithium ions and groups in the electrolyte, such as carboxylic acid esters, during the formation of the SEI film.

[0030] In some embodiments, the vinylene carbonate accounts for 0.5%-3% of the total mass of the electrolyte; and / or, the fluoroethylene carbonate accounts for 0.5%-1.5% of the total mass of the electrolyte; and / or, the 1,3-propanesulfonate lactone accounts for 0.5%-1% of the total mass of the electrolyte. Introducing vinylene carbonate (VC), fluoroethylene carbonate (FEC), and 1,3-propanesulfonate lactone (PS) as first additives in the aforementioned mass proportions can improve the stability of the SEI film formation in lithium-ion batteries, thereby improving the cycle stability of lithium-ion batteries during charge and discharge.

[0031] In some embodiments, the vinyl sulfate (DTD) accounts for 0.5%-1.5% of the total mass of the electrolyte; and / or, the lithium difluorophosphate (LiPO2F2) accounts for 0.2%-1% of the total mass of the electrolyte. Introducing the vinyl sulfate and / or lithium difluorophosphate as a second additive at the aforementioned mass percentages can reduce the impedance of the SEI film formed in the lithium-ion battery, thereby improving the fast-charging performance of the lithium-ion battery.

[0032] In some embodiments, the electrolyte further includes a lithium salt, comprising a first lithium salt and a second lithium salt, wherein the first lithium salt comprises LiPF6, and the second lithium salt comprises at least one of LiFSI, LiTFSI, and LiBF4, and the lithium salt accounts for 8%-20% of the total mass of the electrolyte. At the aforementioned mass percentage, the combined use of the first lithium salt LiPF6 and at least one of the second lithium salts LiFSI, LiTFSI, and LiBF4 in the electrolyte can result in higher thermal stability and ionic conductivity of the lithium salts in the electrolyte. Consequently, the electrolyte exhibits excellent lithium-ion transport capabilities over a wide temperature range, thus significantly improving the power characteristics and low-temperature performance of lithium-ion batteries.

[0033] In some embodiments, the concentration of the first lithium salt is 0.5 mol / L-1.5 mol / L; and / or, the concentration of the second lithium salt is 0.05 mol / L-0.5 mol / L. When the concentrations of the first and / or second lithium salts are within the aforementioned ranges, the lithium salts in the electrolyte can dissociate to generate sufficient mobile lithium ions, resulting in high ionic conductivity. Simultaneously, this effectively matches the changes in lithium ion density during the lithium-ion battery's charge-discharge process. Therefore, the migration capability of lithium ions in the electrolyte is fully adapted to the charge-discharge process of the lithium-ion battery, achieving superior charge-discharge power and cycle performance.

[0034] In some embodiments, LiFSI accounts for 5%-50% of the total mass of the lithium salt; and / or, LiTFSI accounts for 2%-25% of the total mass of the lithium salt; and / or, LiBF4 accounts for 2%-15% of the total mass of the lithium salt; and / or, LiPF6 accounts for 10%-80% of the total mass of the lithium salt. Introducing the second lithium salts LiFSI, LiTFSI, and LiBF4 into the electrolyte at the aforementioned mass percentages, and combining them with the first lithium salt LiPF6, allows for the dissociation of sufficient lithium ions and corresponding anions in the electrolyte even at low temperatures. This effectively enhances the cation migration capability of the electrolyte at low temperatures, comprehensively improving the lithium ion migration capability in the electrolyte. This is beneficial for improving the electrochemical performance of lithium-ion batteries during high-power charge and discharge processes and reducing the impact of temperature on their electrical performance.

[0035] In some embodiments, the viscosity of the electrolyte is 0.5 mPa·s to 8 mPa·s at temperatures ranging from -30°C to 65°C. Therefore, the electrolyte exhibits high flow properties within the operating temperature range of the lithium-ion battery, which is beneficial for improving its wettability to the electrodes, thereby enhancing the charge-discharge capability of the lithium-ion battery at different temperatures.

[0036] In a second aspect, this application proposes a lithium-ion battery comprising the electrolyte proposed in this application. Therefore, the lithium-ion battery proposed in this application exhibits high charge-discharge rates at both room temperature and low temperatures, and also demonstrates superior cycle performance.

[0037] The following specific embodiments illustrate the solution of this application. It should be noted that these embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0038] Example 1 An organic solvent (including carbonate and carboxylic acid ester solvents) is uniformly mixed with ethylene carbonate, ethyl methyl carbonate, and ethyl acetate in a mass ratio of 25:60:15. 0.8 mol / L of lithium salt LiPF6 and 0.4 mol / L of lithium salt LiFSI are then added to the organic solvent, and the mixture is stirred thoroughly to dissolve the lithium salts. Then, 1.5% vinylene carbonate, 0.6% fluoroethylene carbonate, and 0.8% ethylene sulfate (based on the total mass of the electrolyte) are added to prepare the electrolyte.

[0039] The differences between the remaining embodiments and comparative examples and Embodiment 1 are shown in Table 1.

[0040] Table 1

[0041] Experimental testing methods: 1. Lithium-ion battery assembly The positive electrode preparation method is as follows: In a homogenizing device, N-methylpyrrolidone is used as a solvent to uniformly mix lithium iron phosphate powder, Super P conductive carbon black, carbon nanotubes and polyvinylidene fluoride in a mass ratio of 96:1:1:2 to form a positive electrode slurry. The positive electrode slurry is coated on a 12μm aluminum foil, and after drying, cold pressing and cutting, a positive electrode sheet is obtained.

[0042] The negative electrode preparation method is as follows: In a homogenizing equipment, deionized water is used to uniformly mix graphite, Super P conductive carbon black, sodium hydroxymethyl cellulose, and styrene-butadiene rubber at a mass ratio of 96.2:1:0.8:2 to form a negative electrode slurry. The negative electrode slurry is coated on an aluminum foil of 6μm-8μm, and after drying, cold pressing, and cutting, a negative electrode sheet is obtained.

[0043] The preparation of a lithium-ion battery includes: stacking the positive electrode, PE separator, and negative electrode in sequence, with the PE separator acting as a separator between the positive and negative electrodes. Then, the stacked bare cell is placed in an aluminum-plastic film casing, and the prepared electrolyte is injected into the dried battery. After vacuum sealing, settling, formation, secondary degassing and sealing, and volume adjustment, the preparation of the lithium-ion battery is complete.

[0044] 2. Fast charging cycle test at 25°C (room temperature) The aforementioned lithium-ion battery was charged at 25 degrees Celsius and discharged at 1C for 500 cycles, and the cycle data were recorded. The charging regime is shown in Table 2.

[0045] Table 2

[0046] 3. Low-temperature discharge capability test at -30°C and 0.3C The aforementioned lithium-ion battery was placed at -30°C for 6 hours and discharged at 0.3C to test the discharge capacity retention rate.

[0047] Test results: see Figure 1 And Table 3.

[0048] Table 3

[0049] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. "First feature" and "second feature" may include one or more of the indicated feature.

[0050] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.

[0051] In this application, the order in which the steps are written does not imply a strict execution order and does not limit the implementation process. The specific execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps in this application can be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0052] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. An electrolyte, characterized in that, include: Carbonate solvent and carboxylic acid ester solvent, wherein the mass ratio of the carbonate solvent to the carboxylic acid ester solvent is (7:3)-(9:1); The composite additive includes a first functional additive and a second functional additive, the composite additive accounting for 2%-8% of the total mass of the electrolyte, the mass ratio of the first functional additive to the second functional additive being (1:10)-(10:1), the first functional additive including any one of vinylene carbonate, fluorovinyl carbonate, and 1,3-propanesulfonic acid lactone, and the second functional additive including at least one of vinyl sulfate and lithium difluorophosphate.

2. The electrolyte according to claim 1, characterized in that, The carbonate solvent includes at least two of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, and diethyl carbonate; and / or, The carboxylic acid ester solvent includes at least one of ethyl acetate, ethyl propionate, and methyl propionate.

3. The electrolyte according to claim 1, characterized in that, The first functional additive accounts for 0.3%-6% of the total mass of the electrolyte; and / or, The second functional additive accounts for 0.5%-3% of the total mass of the electrolyte.

4. The electrolyte according to claim 1, characterized in that, The vinylene carbonate comprises 0.5%-3% of the total mass of the electrolyte; and / or, The fluoroethylene carbonate comprises 0.5%-1.5% of the total mass of the electrolyte; and / or, The 1,3-propanesulfonic acid lactone accounts for 0.5%-1% of the total mass of the electrolyte.

5. The electrolyte according to claim 1, characterized in that, The vinyl sulfate comprises 0.5%-1.5% of the total mass of the electrolyte; and / or, The lithium difluorophosphate accounts for 0.2%-1% of the total mass of the electrolyte.

6. The electrolyte according to any one of claims 1-5, characterized in that, Also includes: The lithium salt includes a first lithium salt and a second lithium salt, wherein the first lithium salt includes LiPF6 and the second lithium salt includes at least one of LiFSI, LiTFSI, and LiBF4, and the lithium salt accounts for 8%-20% of the total mass of the electrolyte.

7. The electrolyte according to claim 6, characterized in that, The concentration of the first lithium salt is 0.5 mol / L to 1.5 mol / L; and / or, The concentration of the second lithium salt is 0.05 mol / L to 0.5 mol / L.

8. The electrolyte according to claim 6, characterized in that, The LiFSI accounts for 5%-50% of the total mass of the lithium salt; and / or, The LiTFSI comprises 2%-25% of the total mass of the lithium salt; and / or, The LiBF4 comprises 2%-15% of the total mass of the lithium salt; and / or, The LiPF6 accounts for 10%-80% of the total mass of the lithium salt.

9. The electrolyte according to any one of claims 1-5, characterized in that, The viscosity of the electrolyte is 0.5 mPa·s to 8 mPa·s at temperatures ranging from -30°C to 65°C.

10. A lithium-ion battery, characterized in that, Includes the electrolyte according to any one of claims 1-9.

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