Electrolyte for high voltage lithium-ion batteries and its applications

Abstract

The present application relates to the field of lithium-ion batteries, and more particularly to an electrolyte for a high-voltage lithium-ion battery and its application. The electrolyte comprises a solvent and a lithium salt, wherein the solvent comprises 2,2,2-trifluoroethyl methanesulfonate (TM) and / or 2,2,2-trifluoroethyl trifluoromethanesulfonate (TTMS). The electrolyte provided in the embodiments of the present application has strong oxidative stability and forms a S(Li2SO x )CEI membrane suppresses cathode side reactions (transition metal dissolution, gas evolution, etc.) under high voltage conditions, extending the limits of high-voltage batteries and enabling batteries such as graphite||LCO with a cutoff voltage of 4.55V and graphite||NCM811 with a cutoff voltage of 4.6V to remain stable for thousands of cycles while maintaining good safety.

Description

Technical Field

[0001] The present application relates to the field of lithium-ion batteries, and in particular to an electrolyte for a high-voltage lithium-ion battery and its application. Background Art

[0002] Increasing the cutoff voltage is one method for improving the energy density of lithium-ion batteries. However, the solvents in traditional electrolytes (such as linear carbonates (dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC)) and cyclic carbonates (propylene carbonate (PC), ethylene carbonate (EC))) have low oxidation potentials and are not stable at high voltages, decomposing at voltages above 4.3V. Furthermore, traditional electrolytes can undergo severe side reactions with delithiated electrodes at high voltages, leading to dissolution of transition metals from the positive electrode and structural reconstruction, thereby reducing battery performance.

[0003] Numerous approaches have been developed to improve cathode-electrolyte compatibility. For example, surface coating or doping of the cathode can reduce the rate of side reactions between the electrolyte and the cathode. However, CEI films formed using these methods exhibit high interfacial resistance at high voltages and lack self-healing ability, resulting in limited performance improvements.

[0004] Therefore, there is an urgent need to provide an electrolyte suitable for high-voltage lithium-ion batteries. Summary of the Invention

[0005] The present invention solves at least one of the problems of the related art from the following aspects.

[0006] An embodiment of the first aspect of the present application provides an electrolyte comprising a solvent and a lithium salt, wherein the solvent comprises 2,2,2-trifluoroethyl methanesulfonate (TM) and / or 2,2,2-trifluoroethyl trifluoromethanesulfonate (TTMS).

[0007] In some embodiments, the lithium salt is lithium bis(fluorosulfonyl)imide (LiFSI).

[0008] In some embodiments, the electrolyte comprises 0.5 to 6 mol / L of lithium salt.

[0009] In some embodiments, the electrolyte comprises 0.5 to 3 mol / L of lithium salt.

[0010] In some embodiments, the solvent is 2,2,2-trifluoroethyl methanesulfonate (TM) and 2,2,2-trifluoroethyl trifluoromethanesulfonate (TTMS).

[0011] In some embodiments, the solvent is 2,2,2-trifluoroethyl methanesulfonate (TM) and 2,2,2-trifluoroethyl trifluoromethanesulfonate (TTMS) in a volume ratio of (5:1) to (1:5).

[0012] In some embodiments, the solvent is 2,2,2-trifluoroethyl methanesulfonate (TM) and 2,2,2-trifluoroethyl trifluoromethanesulfonate (TTMS) in a volume ratio of (3:1) to (1:2).

[0013] An embodiment of the second aspect of the present application provides an application of the electrolyte of any embodiment of the first aspect in a high-voltage battery.

[0014] In some embodiments, the positive active material of the high voltage battery includes LCO or NCM811.

[0015] In some embodiments, the negative active material of the high voltage battery includes graphite.

[0016] In some embodiments, the high-voltage battery has a charge cut-off voltage greater than 4.3V.

[0017] An embodiment of the third aspect of the present application provides a high-voltage battery, comprising the electrolyte of any embodiment of the first aspect.

[0018] In some embodiments, the positive active material of the high voltage battery includes LCO or NCM811.

[0019] In some embodiments, the negative active material of the high voltage battery includes graphite.

[0020] In some embodiments, the high-voltage battery has a charge cut-off voltage greater than 4.3V.

[0021] Compared with the related art, the embodiments of the present application achieve at least the following beneficial effects:

[0022] The electrolyte provided in the embodiments of the present application is not only stable under high voltage conditions, but also forms an inorganic-rich cathode electrolyte interphase (CEI) on the high-voltage positive electrode, significantly reducing the side reactions of the electrolyte with the delithiation positive electrode material under high voltage conditions. In addition, the electrolyte provided in the embodiments of the present application can also form a stable and low-impedance SEI film on the negative electrode graphite surface, ensuring the long-term cycling stability of LCO and NCM811 batteries at high cut-off voltages.

[0023] The electrolyte provided in the embodiment of the present application has strong oxidative stability and forms a S-containing (Li2SO x)CEI membrane suppresses the delithiation cathode side reactions (transition metal dissolution, gas evolution, etc.) under high voltage conditions, extending the limits of high-voltage batteries and enabling batteries such as graphite||LCO with a cut-off voltage of 4.55V and rechargeable graphite||NCM811 with a cut-off voltage of 4.6V to remain stable for thousands of cycles while maintaining good safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the O1 spectrum of the positive electrode surface of the graphite||NCM811 soft-pack battery using the electrolyte prepared in Example 1.

[0025] Figure 2 This is the EIS impedance spectrum of the graphite||NCM811 soft-pack battery using the electrolyte prepared in Example 1, Comparative Example 1, and Comparative Example 2 after 1000 cycles.

[0026] Figure 3 The oxidation stability of the electrolyte prepared in each example was tested for LSV.

[0027] Figure 4 The oxidation stability of the electrolytes prepared in Example 1 and Comparative Example 2 was tested for LSV.

[0028] Figure 5 The cycling stability of graphite||NCM811 soft-pack batteries using the electrolytes prepared in Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 5 at a cutoff voltage of 4.6V, a charge rate of 1C, and a discharge rate of 2C.

[0029] Figure 6 The cycling stability of graphite||LCO soft-pack batteries using the electrolytes prepared in Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 5 at a cutoff voltage of 4.55V, a charge rate of 1C, and a discharge rate of 2C. DETAILED DESCRIPTION

[0030] The present invention will be further described in detail below in conjunction with specific embodiments. The examples provided are only for illustrating the present invention and are not intended to limit the scope of the present invention. The examples provided below can serve as a guide for further improvements by those skilled in the art and are not intended to limit the present invention in any way.

[0031] This application is made based on the following knowledge of the inventors:

[0032] Increasing the cutoff voltage is one method for improving the energy density of lithium-ion batteries. However, the solvents in traditional electrolytes (such as linear carbonates (dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC)) and cyclic carbonates (propylene carbonate (PC), ethylene carbonate (EC))) have low oxidation potentials and are not stable at high voltages, decomposing at voltages above 4.3V. Furthermore, traditional electrolytes can undergo severe side reactions with delithiated electrodes at high voltages, leading to dissolution of transition metals from the positive electrode and structural reconstruction, thereby reducing battery performance.

[0033] Numerous approaches have been developed to improve cathode-electrolyte compatibility. For example, surface coating or doping of the cathode can reduce the rate of side reactions between the electrolyte and the cathode. However, CEI films formed using these methods exhibit high interfacial resistance at high voltages and lack self-healing ability, resulting in limited performance improvements.

[0034] Electrolyte design can form high-quality CEI films in situ, which is a more promising solution. Hydrofluoroethers, fluorobenzenes, fluorinated sulfones and fluorinated carbonates have excellent oxidative stability. However, the short shelf life of fluorinated electrolytes and the increase in interfacial impedance during use limit their applicability. Although additives can further protect the positive electrode by sacrificially decomposing to form a protective CEI, the CEI is in a dynamic process of formation, destruction and repair, so a small amount of additives cannot maintain interfacial stability during long-term cycling. High-concentration electrolytes (HCE), locally high-concentration electrolytes (LHCE) and weakly solvated electrolytes also improve oxidative stability by forming inorganic-rich CEI / SEI. However, to date, the charge cutoff voltages reported in these electrolytes are mostly limited to 4.5 V (relative to Li + / Li).

[0035] Based on this, the inventors of the present application designed a multifunctional solvent molecule by integrating the advantages of an additive (PS) and a lithium salt (LiOTf) into a solvent, thereby obtaining a fluorinated sulfonate electrolyte for high-voltage lithium-ion batteries.

[0036] An embodiment of the first aspect of the present application provides an electrolyte comprising a solvent and a lithium salt, wherein the solvent comprises 2,2,2-trifluoroethyl methanesulfonate (TM) and / or 2,2,2-trifluoroethyl trifluoromethanesulfonate (TTMS).

[0037] In some embodiments, the lithium salt is lithium bis(fluorosulfonyl)imide (LiFSI).

[0038] In some embodiments, the electrolyte contains 0.5 to 6 mol / L (e.g., 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L) of lithium salt.

[0039] In some embodiments, the electrolyte comprises 0.5 to 3 mol / L (eg, 1 mol / L, 1.5 mol / L, 2 mol / L, 5.2 mol / L) of lithium salt.

[0040] In some embodiments, the solvent is 2,2,2-trifluoroethyl methanesulfonate (TM) and 2,2,2-trifluoroethyl trifluoromethanesulfonate (TTMS).

[0041] In some embodiments, the solvent is 2,2,2-trifluoroethyl methanesulfonate (TM) and 2,2,2-trifluoroethyl trifluoromethanesulfonate (TTMS) in a volume ratio of (5:1) to (1:5) (e.g., 5:1, 4:1, 3:1, 2:1, 1:1, 5:2, 4:2, 3:2, 2:2, 1:2, 5:3, 4:3, 3:3, 2:3, 1:3, 5:4, 4:4, 3:4, 2:4, 1:4, 5:5, 4:54, 3:5, 2:5, 1:5).

[0042] In some embodiments, the solvent is 2,2,2-trifluoroethyl methanesulfonate (TM) and 2,2,2-trifluoroethyl trifluoromethanesulfonate (TTMS) in a volume ratio of (3:1) to (1:2) (eg, 3:1, 3:2, 2:1, 1:1, 1:2).

[0043] An embodiment of the second aspect of the present application provides an application of the electrolyte of any embodiment of the first aspect in a high-voltage battery.

[0044] In some embodiments, the positive electrode active material of the high voltage battery includes but is not limited to LCO or NCM811.

[0045] In some embodiments, the negative electrode active material of the high-voltage battery includes, but is not limited to, graphite, and may also be various modified artificial graphites and other materials.

[0046] In some embodiments, the charging cut-off voltage of the high-voltage battery is greater than 4.3V (eg, greater than 4.5V, such as 4.3-5V, such as 4.5-4.8V, etc.).

[0047] The following examples are used to further illustrate the advantages and characteristics of the present method, but are not intended to limit the present invention. The experimental methods in the following examples, unless otherwise specified, are conventional methods and are performed according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0048] Unless otherwise specified, the quantitative analysis experiments in the following examples were performed three times, and the results were averaged.

[0049] Preparation Example 1

[0050] Synthesis of TTMS: 2,2,2-Trifluoroethanol (1 equivalent) was mixed with dichloromethane, placed in a 5°C water bath, and stirred for 20 minutes. Triethylamine was then added dropwise to the mixture and stirred for an additional 10 minutes. Methanesulfonyl chloride (1.5 equivalents) in dichloromethane was added dropwise to the stirred solvent mixture. The flask was removed from the 5°C bath and the mixture was stirred at room temperature overnight. The reaction mixture was slowly added to a 5% sodium bicarbonate solution and stirred for 20 minutes. The aqueous layer was then extracted with dichloromethane. The organic extract was dried and concentrated to give a 90% yield of the product, which was then transferred to an argon-filled glove box for later use.

[0051] Synthesis of TM: Trifluoromethanesulfonate (12.5 mL, 44.3 mmol) and 2,2,2-trifluoroethanol (6.25 mL, 62.4 mmol) were mixed and stirred at room temperature under nitrogen for 30 minutes, then refluxed at 95°C. After 4 hours, the mixture was allowed to cool to room temperature, and the excess 2,2,2-trifluoroethanol was distilled to obtain the target molecule as a colorless liquid. The product was transferred to an argon-filled glove box for further use.

[0052] Example 1

[0053] An embodiment of an electrolyte for a high-voltage lithium-ion battery of the present invention and its application is provided. The preparation method of the electrolyte for the high-voltage lithium-ion battery described in this embodiment is as follows: first, TM and TTMS are uniformly mixed, and then lithium bis(fluorosulfonyl)imide (LiFSI) is dissolved in a TM / TTMS mixed solvent to prepare an electrolyte having a lithium bis(fluorosulfonyl)imide concentration of 1.9 M and a TM:TTMS volume ratio of 2:1.

[0054] Example 2

[0055] An embodiment of the electrolyte of a high-voltage lithium-ion battery and its application of the present invention is provided. The preparation method of the electrolyte of the high-voltage lithium-ion battery described in this embodiment is as follows: the preparation method of the electrolyte is similar to that of Example 1, except that the concentration of lithium bis(fluorosulfonyl)imide is 1.5 M, and the other conditions remain unchanged.

[0056] Example 3

[0057] An embodiment of the electrolyte of a high-voltage lithium-ion battery and its application of the present invention is provided. The preparation method of the electrolyte of the high-voltage lithium-ion battery described in this embodiment is as follows: the preparation method of the electrolyte is similar to that of Example 1, except that the concentration of lithium bis(fluorosulfonyl)imide is 2.5 M, and the other conditions remain unchanged.

[0058] Example 4

[0059] An embodiment of the electrolyte of a high-voltage lithium-ion battery and its application of the present invention, the preparation method of the electrolyte of the high-voltage lithium-ion battery described in this embodiment is: the preparation method of the electrolyte is similar to that of Example 1, except that the volume ratio of TM:TTMS is 1:1, and the other conditions remain unchanged.

[0060] Example 5

[0061] An embodiment of the electrolyte of a high-voltage lithium-ion battery and its application of the present invention, the preparation method of the electrolyte of the high-voltage lithium-ion battery described in this embodiment is: the preparation method of the electrolyte is similar to that of Example 1, except that the volume ratio of TM:TTMS is 3:1, and the other conditions remain unchanged.

[0062] Example 6

[0063] An embodiment of the electrolyte of a high-voltage lithium-ion battery and its application of the present invention, the preparation method of the electrolyte of the high-voltage lithium-ion battery described in this embodiment is: the preparation method of the electrolyte is similar to that of Example 1, except that the volume ratio of TM:TTMS is 1:2, and the other conditions remain unchanged.

[0064] Example 7

[0065] An embodiment of the electrolyte of a high-voltage lithium-ion battery and its application of the present invention is provided. The preparation method of the electrolyte of the high-voltage lithium-ion battery described in this embodiment is as follows: the preparation method of the electrolyte is similar to that of Example 1, except that the concentration of lithium bis(fluorosulfonyl)imide is 0.5M or 1M, and the other conditions remain unchanged.

[0066] Comparative Example 1

[0067] A comparative example of the electrolyte of a high-voltage lithium-ion battery of the present invention and its application is provided. The preparation method of the electrolyte in this comparative example is as follows: lithium hexafluorophosphate is dissolved in a solvent with an EC:DMC ratio of 1 to prepare an electrolyte with a lithium salt concentration of 1M.

[0068] Comparative Example 2

[0069] A comparative example of the electrolyte of a high-voltage lithium-ion battery of the present invention and its application is provided. The preparation method of the electrolyte in this comparative example is as follows: lithium hexafluorophosphate is dissolved in a solvent with a ratio of EC:DMC:VC of 49:49:2 to prepare an electrolyte with a lithium salt concentration of 1M.

[0070] Comparative Example 3

[0071] A comparative example of the electrolyte of the high-voltage lithium-ion battery of the present invention and its application is provided. The preparation method of the electrolyte in this comparative example is as follows: the preparation method of the electrolyte is similar to that of Example 1, except that TM is replaced with trifluoromethyl trifluoromethanesulfonate, and the other conditions remain unchanged.

[0072] Comparative Example 4

[0073] A comparative example of the electrolyte of the high-voltage lithium-ion battery of the present invention and its application is provided. The preparation method of the electrolyte in this comparative example is as follows: the preparation method of the electrolyte is similar to that of Example 1, except that TTMS is replaced with trifluoroethyl perfluorobutyl sulfonate or 2,2-difluoroethanol methane sulfonate, and the other conditions remain unchanged.

[0074] Comparative Example 5

[0075] A comparative example of the electrolyte of the high-voltage lithium-ion battery of the present invention and its application, the preparation method of the electrolyte in this comparative example is: the preparation method of the electrolyte is similar to that of Example 1, except that it also contains solvent dimethyl carbonate, and the volume ratio of TM:TTMS:dimethyl carbonate is 2:1:1, and the other conditions remain unchanged.

[0076] Test Example 1

[0077] 1.1 The conductivity of the electrolytes prepared in various embodiments was tested, and the results are shown in Tables 1 and 2 below.

[0078] Conductivity detection method: Conductivity meter AC impedance method, test voltage 10mV, test frequency 0.01Hz~10KHz.

[0079] Table 1: Li electrolytes with different lithium salt concentrations of TM:TTMS = 2:1 + Conductivity

[0080]

[0081] Table 2: Li in 1.9M LiFSI in different solvent ratios + Conductivity

[0082] TM:TTMS <![CDATA[Li + Conductivity (mS / cm) TM:TTMS=3:1 (corresponding to Example 5) 4.18 TM:TTMS=2:1 (corresponding to Example 1) 2.53 TM:TTMS=1:1 (corresponding to Example 4) 1.68 TM:TTMS=1:2 (corresponding to Example 6) 1.52

[0083] 1.2 Linear sweep voltammetry (LSV) was used to test the oxidation stability of the electrolytes prepared in each embodiment. The results are as follows: Figure 3-4 shown.

[0084] Specific methods and conditions for LSV testing: test range is 2~6V, scan rate is 1mV / s.

[0085] Figure 3Among them, the TM:TTMS=3:1 group corresponds to the electrolyte prepared in Example 5, the TM:TTMS=2:1 group corresponds to the electrolyte prepared in Example 1, the TM:TTMS=1:1 group corresponds to the electrolyte prepared in Example 4, and the TM:TTMS=1:2 group corresponds to the electrolyte prepared in Example 6. Figure 3 It can be seen that the electrolytes of Examples 1 and 4-6 have excellent oxidation stability and the current density is lower than 0.01 mA / cm 2 .

[0086] Figure 4 The results of the electrolyte oxidation stability test of Example 1 and Comparative Example 2 are shown. Figure 4 It can be seen that the current density of Example 1 is Figure 3 The measured results were consistent and never exceeded 0.01mA / cm 2 , and its oxidation stability is significantly better than that of Comparative Example 2.

[0087] Test Example 2

[0088] 2.1 The electrolytes prepared in Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 5 were respectively injected between the MNC811 ternary positive electrode sheet and the graphite negative electrode to assemble a ternary lithium battery (1Ah graphite||NCM811 soft pack battery) for charge and discharge tests. The performance test results are shown in Tables 3 and Figure 2 and 5 .

[0089] The proportion of positive and negative active materials in the 1Ah graphite||NCM811 soft pack battery is 95.5% and 94.8% respectively, and the compaction density of the positive and negative electrodes is 3.4cc respectively. -1 and 1.5cc -1 The N / P ratio is 1.1. The injection volume is 2g.

[0090] Table 3

[0091] electrolyte Ni(ppm) Co(ppm) Mn (ppm) Example 1 0.003 0.0004 0.001 Comparative Example 2 0.009 0.001 0.003

[0092] Table 3 shows the amount of transition metal dissolution in the graphite||NCM811 soft-pack battery using the electrolyte prepared in Example 1 or Comparative Example 2 after 100 cycles (25°C 1C charge / 2C discharge, charge cut-off voltage of 4.6V and discharge cut-off voltage of 2.7V).

[0093] Figure 2 The EIS impedance spectra of the graphite||NCM811 soft-pack battery using the electrolytes of Example 1, Comparative Example 1, and Comparative Example 2 after 1000 cycles are shown.

[0094] Figure 5The cycling stability of graphite||NCM811 soft-pack batteries using the electrolytes of Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 5 at a cutoff voltage of 4.6V, a charge rate of 1C, and a discharge rate of 2C is shown. The test results of Comparative Example 4 are similar to those of Comparative Example 3 and are not shown here.

[0095] according to Figure 2 and Figure 5 It can be seen that the graphite||NCM811 soft-pack battery using the electrolyte of Example 1 has lower impedance and better cycle performance, which is significantly better than each comparative example.

[0096] 2.2 X-ray photoelectron spectroscopy (XPS) was used to detect the positive electrode surface of the graphite||NCM811 soft pack battery using the electrolyte prepared in Example 1 after 100 cycles (25°C 1C charge / 2C discharge charge cut-off voltage of 4.6V discharge cut-off voltage of 2.7V). The results are as follows Figure 1 shown.

[0097] Table 3 and Figure 1 The results show that TM and TTMS decompose during the initial charge and discharge process to generate more protective inorganic Li2SO x CEI membrane significantly reduces the dissolution of transition metals in the cathode material.

[0098] Test Example 3

[0099] The electrolytes in Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 5 were injected between the LCO positive electrode sheet and the graphite negative electrode, and assembled into lithium cobalt oxide soft pack batteries (1Ah graphite||LCO soft pack batteries) for charge and discharge tests. The performance test results are shown in Figure 6 .

[0100] The proportion of positive and negative active materials in a 1Ah lithium cobalt oxide soft pack battery is 98.6% and 96.7% respectively, and the compaction density of the positive and negative electrodes is 4.1cc respectively. -1 and 1.7cc -1 The N / P ratio is 1.1. The injection volume is 2g.

[0101] Figure 6 The cycling stability of graphite||LCO soft-pack batteries using the electrolytes of Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 5 at a cutoff voltage of 4.55V, a charge rate of 1C, and a discharge rate of 2C is shown. The test results of Comparative Example 4 are similar to those of Comparative Example 3 and are not shown here.

[0102] according to Figure 6 It can be seen that the cycle performance of the graphite||LCO soft-pack battery using the electrolyte of Example 1 is better and significantly better than that of each comparative example.

[0103] High-voltage electrolyte needs to form a stable CEI film on the surface of the positive electrode material to enhance the passivation ability of the delithiation positive electrode material surface, thereby reducing the side reaction between the positive electrode material and the electrolyte. The organic CEI film formed by the decomposition of traditional EC, DMC and other electrolytes has poor stability and cannot effectively protect the positive electrode material. The TM and TTMS in the fluorinated sulfonate electrolyte prepared in the embodiment of the present application will decompose during the initial charge and discharge process and generate more protective inorganic Li2SO x CEI membrane significantly reduces the dissolution of transition metals in cathode materials ( Figure 1 and Table 3 ).

[0104] In addition, the high-voltage electrolyte needs to form a stable SEI film with low interfacial impedance on the graphite negative electrode to ensure faster battery kinetic performance. The impedance of the SEI film of the battery with the electrolyte of Example 1 of this application after 1000 cycles is significantly lower than that of Comparative Examples 1 and 2 ( Figure 2 ).

[0105] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0106] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. An electrolyte, characterized in that The invention consists of a solvent and a lithium salt, wherein the solvent consists of 2,2,2-trifluoroethyl methanesulfonate and 2,2,2-trifluoroethyl trifluoromethanesulfonate; and the lithium salt is lithium bis(fluorosulfonyl)imide.

2. The electrolyte according to claim 1, wherein The electrolyte contains 0.5 to 6 mol / L of lithium salt.

3. The electrolyte according to claim 2, wherein The electrolyte contains 0.5 to 3 mol / L of lithium salt.

4. The electrolyte according to claim 1, characterized in that The solvent is 2,2,2-trifluoroethyl methanesulfonate and 2,2,2-trifluoroethyl trifluoromethanesulfonate in a volume ratio of (5:1) to (1:5).

5. The electrolyte according to claim 4, characterized in that The solvent is 2,2,2-trifluoroethyl methanesulfonate and 2,2,2-trifluoroethyl trifluoromethanesulfonate in a volume ratio of (3:1) to (1:2).

6. Use of the electrolyte according to any one of claims 1 to 5 in a high voltage battery.

7. The use according to claim 6, characterized in that The positive electrode active material of the high voltage battery includes LCO or NCM811.

8. The use according to claim 7, characterized in that The negative active material of the high voltage battery includes graphite.

9. The use according to claim 6, characterized in that The cut-off voltage of the high-voltage battery is greater than 4.3V.

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