Composite electrolyte and preparation method and application thereof

Abstract

The invention discloses a composite electrolyte and a preparation method and application thereof. The composite electrolyte comprises a lithium salt, a solvent, a Lewis acid precursor, a Lewis acid trapping agent and a thermal response monomer, the mass content of the Lewis acid precursor is 0.1-5%, the mass content of the Lewis acid trapping agent is 2-5%, and the mass content of the thermal response monomer is 5-30%. The composite electrolyte can be rapidly polymerized at high temperature, so that the thermal stability of the electrolyte is improved, an ion transmission path is cut off, meanwhile, the composite electrolyte can be stably kept in a liquid state in a non-high-temperature environment, the electrochemical performance of the composite electrolyte is not influenced, and the composite electrolyte can be compatible with various storage and use environments; the problems of gas production and fire in the thermal runaway process of the battery can be remarkably inhibited, the safety of the battery is improved, and the electrical performance of the battery in a normal operation state is not influenced.

Description

Technical Field

[0001] The present invention relates to a composite electrolyte, and also relates to a preparation method and application of the composite electrolyte in lithium ion batteries, belonging to the technical field of lithium batteries. Background Art

[0002] As a key component of electrochemical energy storage systems, lithium-ion batteries play a vital role in new energy systems. Despite this, lithium-ion batteries still face safety issues and are prone to thermal runaway under thermal, electrical, and mechanical abuse conditions, posing a significant challenge to the stable operation of new energy systems.

[0003] Commercial lithium-ion battery electrolytes are primarily composed of carbonate solvents, which can easily burn during thermal runaway and generate large amounts of flammable and explosive gases. To improve lithium-ion battery safety, employing electrolytes with higher thermal stability has become a key research direction.

[0004] While gelation can effectively improve the thermal stability of electrolytes, existing technologies often directly achieve electrolyte gelation during battery preparation through heating, radiation, and other methods. This results in decreased electrolyte ionic conductivity and poor contact between the electrolyte and the positive and negative electrodes, seriously affecting battery performance. Furthermore, because existing technologies often use free radical initiators to achieve electrolyte gelation, strict control is required over the storage and use environment of the electrolyte.

[0005] Patent publication number CN111430780B discloses a gel electrolyte raw material composition for lithium-ion batteries, which contains a non-aqueous organic solvent, an electrolyte lithium salt, and additives such as inorganic acid organic esters and / or nitriles, and acrylic esters. By mixing the composition with a thermal initiator, the electrolyte is gelled in situ, significantly improving the safety of the battery. Patent publication number CN117497843B discloses a gel electrolyte for lithium batteries, a preparation method thereof, and a preparation method for a gel electrolyte lithium battery, relating to the field of lithium battery technology. The preparation method of the gel electrolyte for lithium batteries comprises pre-preparing a precursor polymer M by polymerizing monomers A, B, C and an initiator, and then mixing M with the electrolyte to prepare a gel electrolyte. The step-by-step polymerization method reduces the influence of the polymerized monomers and initiators on the electrolyte performance, thereby improving the low-temperature rate performance of the lithium battery. However, the above-mentioned technologies all use free radical initiators to achieve gelation, which has strict requirements on the storage and use environment of the electrolyte. In addition, the above technologies all perform electrolyte gelation during the battery preparation process, resulting in a decrease in the electrolyte ion conductivity and affecting the battery's electrical performance.

[0006] Therefore, it is crucial to develop an electrolyte with high thermal stability and high ionic conductivity to improve the safety and electrochemical performance of lithium batteries. Summary of the Invention

[0007] In view of the problems in the prior art, a first object of the present application is to provide a composite electrolyte.

[0008] A second object of the present application is to provide a preparation method of the composite electrolyte.

[0009] A third object of the present application is to provide an application of the composite electrolyte.

[0010] To achieve the above technical objects, the present application provides a composite electrolyte comprising a lithium salt, a solvent, a Lewis acid precursor, a Lewis acid capturing agent and a thermal response monomer, the mass content of the Lewis acid precursor being 0.1-5%, the mass content of the Lewis acid capturing agent being 2-5%, and the mass content of the thermal response monomer being 5-30%.

[0011] The present application constructs a Lewis acid slow-release mechanism by introducing a Lewis acid precursor and a capturing agent. In a non-high-temperature conventional environment, the Lewis acid precursor decomposes slowly and only releases a small amount of Lewis acid during long-term storage. The Lewis acid capturing agent such as is(thio)cyanate or silazane, silamine alkane can coordinate with the Lewis acid through the nitrogen, sulfur and oxygen atoms containing lone pairs of electrons, thereby neutralizing the acidity and blocking the initiation of cationic polymerization of monomers in the electrolyte. However, due to the large steric hindrance, the coordination compound formed by the capturing agent and the Lewis acid in the present application has limited stability. At high temperature, the Lewis acid is re-released through reversible decomposition, and the decomposition rate of the Lewis acid in the electrolyte at high temperature is also significantly increased, greatly exceeding the binding capacity of the capturing agent, thereby further rapidly initiating the cationic polymerization of the thermal response monomer, achieving rapid thermal response solidification of the electrolyte, improving the thermal stability of the electrolyte and cutting off the internal ion path, and significantly improving the safety of the battery. In summary, the present application realizes long-term stable storage of the electrolyte at room temperature and rapid response polymerization at high temperature by introducing the Lewis acid precursor and the capturing agent, ensures the high ionic conductivity of the electrolyte in normal environment, makes the electrochemical performance of the electrolyte unaffected, and improves the safety and stability of the electrolyte.

[0012] In addition, controlling the content of the Lewis acid, the Lewis acid capturing agent and the thermal response monomer within a suitable range can ensure that the electrolyte has excellent comprehensive performance. If the content of the Lewis acid precursor is too high, the content of the Lewis acid capturing agent is too low or the content of the thermal response monomer is too high, the electrochemical performance of the electrolyte in a normal environment will be affected. If the content of the Lewis acid precursor is too low, the content of the Lewis acid capturing agent is too high or the content of the thermal response monomer is too low, the thermal response solidification effect of the electrolyte in a high-temperature environment will be affected, and the high-temperature safety performance of the electrolyte is limited.

[0013] As a preferred solution, the Lewis acid precursor includes at least one of lithium hexafluorophosphate, lithium difluoro(oxalato)borate, tris(pentafluorophenyl)borane, tris(pentafluorophenyl)phosphine, lithium tetrafluoroborate, tin tetrachloride, titanium tetrachloride, titanium tetrabromide and aluminum triflate. Such a Lewis acid precursor has good stability in a non-high-temperature environment and is easy to decompose to generate a Lewis acid under a high-temperature condition.

[0014] As a preferred solution, the Lewis acid capturing agent includes at least one of trimethylsilyl isocyanate, (trimethylsilyl) isothiocyanate, 4-(trifluoromethyl)phenyl isothiocyanate, hexamethyldisilazane and heptamethyldisilazane. Such a Lewis acid capturing agent has moderate Lewis acid combination capacity and is suitable for the system of the present application.

[0015] As a preferred solution, the thermal response monomer includes at least one of 2-fluorostyrene, 3-fluorostyrene, 4-fluorostyrene, 4-(trifluoromethyl)styrene, 2,3,4,5,6-pentafluorostyrene, 4-fluoro-alpha-methylstyrene, acrylamidomethylpropane sulfonic acid and perfluoro octyl acrylate.

[0016] As a preferred solution, the composite electrolyte further contains a film-forming additive.

[0017] As a preferred solution, the content of the film-forming additive is 1-7 wt% of the composite electrolyte.

[0018] As a preferred solution, the film-forming additive includes at least one of vinylene carbonate, vinyl sulfate, fluoroethylene carbonate, methane disulfonic acid methylene ester, 1,3-propane sultone and vinyl vinylene carbonate.

[0019] As a preferred solution, the lithium salt includes at least one of lithium bistrifluoromethylsulfonylimide, lithium bisfluorosulfonylimide, lithium perchlorate and lithium nitrate.

[0020] As a preferred solution, the content of the lithium salt is 10-15.5 wt%.

[0021] As a preferred scheme, the solvent comprises at least one of ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, gamma-butyrolactone, methyl acetate, propyl acetate, and butyl acetate.

[0022] The application further provides a preparation method of the composite electrolyte, which comprises mixing raw materials comprising a lithium salt, a solvent, a Lewis acid precursor, a Lewis acid capturing agent, and a thermal response monomer.

[0023] The application further provides an application of the composite electrolyte, which is used as an electrolyte for a lithium ion battery.

[0024] Compared with the prior art, the application has the following beneficial effects:

[0025] (1) The composite electrolyte provided by the application can rapidly respond to polymerization and solidification under a high-temperature environment, and can stably maintain a liquid state of the electrolyte under a non-high-temperature conventional environment, thereby ensuring the electrochemical performance of the electrolyte and significantly improving the comprehensive stability of the electrolyte, and the compatibility with storage and use environments is good.

[0026] (2) The composite electrolyte does not need to be pre-gelatinized in the battery preparation process, has high ionic conductivity of the electrolyte, and has good contact and infiltration with the positive and negative electrodes, and does not affect the electrical performance of the battery.

[0027] (3) The composite electrolyte provided by the application can be rapidly solidified under a high temperature, thereby improving the thermal stability of the electrolyte, cutting off the ion passage inside the battery, and insulating the positive and negative electrodes as a supporting material, preventing large-area short circuit inside the battery, and greatly improving the safety performance of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only constitute the embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of the provided drawings.

[0029] Figure 1 The figure is a thermal response solidification effect diagram of the composite electrolyte of the embodiment 1 of the application under 120 DEG C.

[0030] Figure 2 The figure is a cycle performance comparison diagram of the lithium ion batteries corresponding to the embodiment 1 and the comparative example 2 of the application. DETAILED DESCRIPTION

[0031] The technical solutions of the present application will be described clearly and completely below in combination with the embodiments of the present application and the drawings. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0032] In the following examples, if not specifically stated, the raw materials and equipment used are commercially available, and the solvents used are analytical pure.

[0033] Lithium hexafluorophosphate: CAS No. 21324-40-3, purchased from Suzhou Dodd Reagent Co., Ltd.

[0034] Lithium difluorooxalate borate: CAS No. 409071-16-5, purchased from Suzhou Dodd Reagent Co., Ltd.

[0035] Lithium tetrafluoroborate: CAS No. 14283-07-9, purchased from Suzhou Dodd Reagent Co., Ltd.

[0036] Trimethylsilyl isocyanate: CAS No. 1118-02-1, purchased from Shanghai McLean Biochemical Science and Technology Co., Ltd.

[0037] Hexamethyldisilazane: CAS No. 999-97-3, purchased from Shanghai McLean Biochemical Science and Technology Co., Ltd.

[0038] 4-Fluorostyrene: CAS No. 405-99-2, purchased from Shanghai McLean Biochemical Science and Technology Co., Ltd.

[0039] Acrylamidomethylpropane sulfonic acid: CAS No. 15214-89-8, purchased from Shanghai McLean Biochemical Science and Technology Co., Ltd.

[0040] Lithium bisfluorosulfonylimide: CAS No. 9002-81-7, purchased from Suzhou Dodd Reagent Co., Ltd.

[0041] Lithium perchlorate: CAS No. 7791-03-9, purchased from Suzhou Dodd Reagent Co., Ltd.

[0042] Vinyl carbonate: CAS No. 96-49-1, purchased from Suzhou Dodd Reagent Co., Ltd.

[0043] Dimethyl carbonate: CAS No. 616-38-6, purchased from Suzhou Dodd Reagent Co., Ltd.

[0044] Methyl ethyl carbonate: CAS No. 623-53-0, purchased from Suzhou Dodd Reagent Co., Ltd.

[0045] Vinylene carbonate: CAS No. 872-36-6, purchased from Suzhou Dodd Reagent Co., Ltd.

[0046] Vinyl sulfate: CAS No. 1072-53-3, purchased from Suzhou Dodd Reagent Co., Ltd.

[0047] Fluoroethylene carbonate: CAS No. 114435-02-8, purchased from Suzhou Dodd Reagent Co., Ltd.

[0048] Polyolefin separator: Celgard 2400 separator, thickness 25 μm, single layer of PP material, 41% porosity, purchased from Celgard, USA.

[0049] Commercialized lithium iron phosphate positive electrode: areal density 13.5 mg / cm 2 , active material proportion 95.3 wt%, purchased from Shenzhen Keyouzhida Technology Co., Ltd.

[0050] Commercialized graphite negative electrode: areal density 6.3 mg / cm 2 , active material proportion 95.3 wt%, purchased from Shenzhen Keyouzhida Technology Co., Ltd.

[0051] In the following examples, room temperature refers to 23±2℃.

[0052] Example 1

[0053] In an argon glove box (water and oxygen content less than 0.1 ppm), the following substances were weighed in turn:

[0054] Lewis acid precursor: 0.20 g lithium difluoro(oxalato)borate;

[0055] Lewis acid trapping agent: 0.40 g trimethylsilylisocyanate;

[0056] Thermally responsive monomer: 1.5 g 4-fluorostyrene;

[0057] Lithium salt: 1.2 g lithium bis(fluorosulfonyl)imide;

[0058] Solvent: 2.00 g dimethyl carbonate, 2.00 g vinyl carbonate and 2.50 g ethyl methyl carbonate;

[0059] Film-forming additive: 0.10 g vinylene carbonate, 0.05 g fluoroethylene carbonate and 0.05 g vinyl sulfate;

[0060] After mixing all the above substances at room temperature and stirring for 6 h, a safe electrolyte S1 was prepared when the lithium salt was completely dissolved.

[0061] Example 2

[0062] The electrolyte was prepared by the method of Example 1, except that the lithium difluoro(oxalato)borate was replaced by an equal mass of lithium tetrafluoroborate to obtain a safe electrolyte S2.

[0063] Example 3

[0064] The electrolyte was prepared by the method of Example 1, except that the trimethylsilyl isocyanate was replaced by an equal mass of hexamethyldisilazane to obtain a safe electrolyte S3.

[0065] Example 4

[0066] The electrolyte was prepared by the method of Example 1, except that the 4-fluorostyrene was replaced by an equal mass of acrylamidomethylpropane sulfonic acid to obtain a safe electrolyte S4.

[0067] Example 5

[0068] The electrolyte was prepared by the method of Example 1, except that the lithium bisfluorosulfonylimide was replaced by an equal mass of lithium perchlorate to obtain a safe electrolyte S5.

[0069] Example 6

[0070] The electrolyte was prepared by the method of Example 1, except that the raw material ratio was:

[0071] Lewis acid precursor: 0.10 g lithium difluoroborate;

[0072] Lewis acid trapping agent: 0.20 g trimethylsilyl isocyanate;

[0073] Thermal response monomer: 2.0 g 4-fluorostyrene;

[0074] Lithium salt: 1.2 g lithium bisfluorosulfonylimide;

[0075] Solvent: 1.80 g dimethyl carbonate, 2.00 g ethylene carbonate, 2.50 g methyl ethyl carbonate;

[0076] Film-forming additive: 0.10 g vinylene carbonate, 0.05 g fluoroethylene carbonate, 0.05 g ethylene sulfate. This example obtained a safe electrolyte S6.

[0077] Example 7

[0078] The electrolyte was prepared by the method of Example 2, except that the lithium bisfluorosulfonylimide was replaced by an equal mass of lithium perchlorate to obtain a safe electrolyte S7.

[0079] Example 8

[0080] The electrolyte was prepared by the method of Example 1, except that no film-forming additive was used.

[0081] Comparative Example 1

[0082] Commercial lithium ion battery electrolyte, the specific composition is 1 M LiPF6 EC / EMC / DMC = 1 / 1 / 1 (wt%), that is, the solvent is a mixed solvent of vinyl carbonate, ethyl methyl carbonate and dimethyl carbonate with a mass ratio of 1:1:1, and the concentration of lithium hexafluorophosphate is 1 mol / L.

[0083] Comparative Example 2

[0084] Conventional gelled electrolyte, the specific composition is 1 M LiPF6 EC / EMC / DMC = 1 / 1 / 1 (wt%) + 0.1wt% azobisisobutyronitrile + 10wt% methyl methacrylate + 10wt% ethylene glycol dimethacrylate, that is, the solvent is a mixed solvent of vinyl carbonate, ethyl methyl carbonate and dimethyl carbonate with a mass ratio of 1:1:1, and the concentration of lithium hexafluorophosphate in the electrolyte is 1 mol / L, and 0.1wt% azobisisobutyronitrile, 10wt% methyl methacrylate and 10wt% ethylene glycol dimethacrylate are added according to the mass of the lithium-containing mixed solution.

[0085] Comparative Example 3

[0086] The electrolyte is prepared by the method of Example 1, except that no Lewis acid precursor is added.

[0087] Comparative Example 4

[0088] The electrolyte is prepared by the method of Example 1, except that no Lewis acid capturing agent is added.

[0089] Comparative Example 5

[0090] The electrolyte is prepared by the method of Example 1, except that no thermal response monomer is added.

[0091] Comparative Example 6

[0092] The electrolyte is prepared by the method of Example 1, except that the content of the Lewis acid capturing agent is increased to 1.0g.

[0093] Comparative Example 7

[0094] The electrolyte is prepared by the method of Example 1, except that the content of the Lewis acid precursor is increased to 0.6g and the content of the Lewis acid capturing agent is decreased to 0.1g.

[0095] The commercial lithium iron phosphate positive electrode, the commercial graphite negative electrode, the commercial separator (polyolefin separator), and the electrolyte prepared in each example and the comparative example were assembled into lithium ion batteries, respectively. Among them, for Comparative Example 2, the commercial lithium iron phosphate positive electrode, the commercial graphite negative electrode, the commercial separator (polyolefin separator), and the electrolyte prepared in Comparative Example 2 were assembled into a battery, and heated at 60°C for 48h to obtain the corresponding lithium ion battery.

[0096] The performance of each lithium ion battery was tested, including electrolyte high-temperature response test, electrolyte long-term storage stability test, battery cycle performance test, and battery needle test, and the results are shown in Table 1. Among them, the electrolyte high-temperature response test was as follows: in an argon glove box (water and oxygen content were less than 0.1 ppm), 2.0g of electrolyte was weighed and placed in a transparent glass bottle, sealed and transferred to a 120°C air oven for heating, and the electrolyte thermal response time and solidification degree were recorded.

[0097]

[0098] As can be seen from Table 1, the composite electrolyte prepared in the examples of the present application can quickly respond to complete solidification of the electrolyte at high temperature, and the thermal response speed is faster and the solidification degree is higher than that of Comparative Example 2 which represents a conventional gel electrolyte. Comparative Example 6 shows that too high a content of the capturing agent in the electrolyte will affect the thermal response effect of the electrolyte, making the electrolyte unable to quickly solidify, thereby reducing the high-temperature safety performance of the electrolyte.

[0099] Figure 1 The photo of the composite electrolyte S1 prepared in Example 1 of the present application was thermally solidified at 120°C, and from the figure it can be seen that the electrolyte can be completely solidified at high temperature and presents as a white solid, indicating a high degree of polymerization.

[0100] The long-term storage stability test of each electrolyte was as follows: in an argon glove box (water and oxygen content were less than 0.1 ppm), 2.0g of electrolyte was weighed and placed in a transparent glass bottle, sealed and transferred to a room temperature, conventional humidity environment for storage, and the electrolyte spontaneous gelation time and solidification degree were recorded, and the test results are shown in Table 2.

[0101]

[0102] As can be seen from Table 2, the composite electrolyte prepared in the present application can be maintained in a liquid state at room temperature for a long time without special low-temperature and light-avoiding storage, and the stability is significantly better than that of Comparative Example 2 which represents a conventional gel electrolyte, and also better than that of Comparative Example 4 without a capturing agent. Comparative Example 7 shows that when the content of the Lewis acid in the electrolyte is too high, the electrolyte will solidify in a non-high-temperature environment, thereby affecting the electrochemical performance of the battery.

[0103] The battery cycle performance test was performed on the battery assembled by each electrolyte: the cycle test was performed on a RIGIDIT charge-discharge tester, specifically: (1) 3 times of charging and discharging at 0.1C rate in the voltage range of 2.5-3.65V to fully activate the battery; (2) cycle test of charging and discharging at 0.5C rate in the voltage range of 2.5-3.65V, and the discharge capacity retention rate and energy efficiency after 100 cycles were recorded, wherein the discharge capacity retention rate = discharge capacity of the 100th cycle / discharge capacity of the first cycle x 100%, and the test results are shown in Table 3.

[0104]

[0105] As can be seen from Table 3, the lithium ion battery prepared by using the composite electrolyte of the application has good discharge capacity retention rate and energy efficiency, which indicates that the composite electrolyte of the application has no negative effect on the battery performance, and the performance is significantly better than that of the conventional gelled electrolyte (Comparative Example 2). At the same time, from the data of Comparative Examples 6 and 7, it can be seen that too high content of Lewis acid precursor or too high content of capturing agent in the electrolyte will affect the charge-discharge performance of the battery, especially when the content of Lewis acid is too high, the discharge capacity retention rate and energy efficiency of the battery will be greatly reduced.

[0106] Figure 2 The cycle performance test was performed on the lithium ion battery prepared by using the electrolyte of Example 1 and Comparative Example 2 of the application, and from the graph, it can be seen that the cycle performance of the lithium ion battery corresponding to Example 1 of the application is significantly better than that of the lithium ion battery prepared by using the conventional gelled electrolyte (Comparative Example 2).

[0107] The battery needle test was performed on the battery corresponding to each embodiment and comparative example electrolyte: the battery was charged to 3.65V on a RIGIDIT charge-discharge tester, and then the needle test and heating test were performed. The steel needle used in the needle test has a diameter of 6mm, and the penetration speed is 25mm / s, and the state of the battery after needle penetration is recorded, and the test results are shown in Table 4.

[0108]

[0109] As can be seen from Table 4, the lithium ion battery corresponding to the electrolyte in the application does not smoke and does not catch fire after needle penetration, and the safety is better than that of the lithium ion battery prepared by using the commercial electrolyte (Comparative Example 1) and the conventional gelled electrolyte (Comparative Example 2), which indicates that the composite electrolyte of the application can effectively improve the safety of the battery. At the same time, from the data of Comparative Example 6, it can be seen that too high content of capturing agent in the electrolyte will greatly reduce the fire safety performance of the lithium battery.

[0110] Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A composite electrolyte, characterized by: The lithium salt, the solvent, the Lewis acid precursor, the Lewis acid capturing agent and the thermal responsive monomer, the mass content of the Lewis acid precursor is 0.1-5%, the mass content of the Lewis acid capturing agent is 2-5%, and the mass content of the thermal responsive monomer is 5-30%.

2. The composite electrolyte according to claim 1, characterized in that: The Lewis acid precursor includes at least one of lithium hexafluorophosphate, lithium difluoro(oxalato)borate, tris(pentafluorophenyl)borane, tris(pentafluorophenyl)phosphine, lithium tetrafluoroborate, tin tetrachloride, titanium tetrachloride, titanium tetrabromide, and aluminum triflate.

3. The composite electrolyte according to claim 1, wherein: The Lewis acid capturing agent includes at least one of trimethylsilyl isocyanate, (trimethylsilyl) isothiocyanate, 4-(trifluoromethyl)phenyl isothiocyanate, hexamethyldisilazane, and heptamethyldisilazane.

4. The composite electrolyte according to claim 1, wherein: The thermal responsive monomer includes at least one of 2-fluorostyrene, 3-fluorostyrene, 4-fluorostyrene, 4-(trifluoromethyl)styrene, 2,3,4,5,6-pentafluorostyrene, 4-fluoro-alpha-methylstyrene, acrylamidomethylpropane sulfonic acid, and perfluorooctyl acrylate.

5. The composite electrolyte of claim 1, 2, 3 or 4, wherein: the composite electrolyte further comprises a film-forming additive; and the film-forming additive is present in an amount of 1-7 wt% of the composite electrolyte. The film-forming additive includes at least one of vinylene carbonate, vinyl sulfate, fluorinated vinyl carbonate, methane disulfonic acid methylene ester, 1,3-propane sultone, and vinyl vinylene carbonate.

7. The composite electrolyte of claim 1, wherein: the lithium salt includes at least one of lithium bistrifluoromethanesulfonylimide, lithium bisfluorosulfonylimide, lithium perchlorate, and lithium nitrate; and the lithium salt is present in an amount of 10-15.5 wt%.

6. The composite electrolyte according to claim 5, wherein: The solvent includes at least one of vinyl carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, gamma-butyrolactone, methyl acetate, propyl acetate, and butyl acetate. The raw materials including the lithium salt, the solvent, the Lewis acid precursor, the Lewis acid capturing agent and the thermal responsive monomer are mixed to obtain the composite electrolyte. The composite electrolyte is used as an electrolyte for a lithium ion battery. ​ 8. The composite electrolyte of claim 1, wherein: ​ 9. A method of preparing a composite electrolyte according to any one of claims 1 to 8, characterised in that: ​ 10. Use of a composite electrolyte according to any one of claims 1 to 8, characterized in that: ​

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