Low-temperature lithium ion battery gel electrolyte as well as preparation method and application thereof

Abstract

The invention provides a low-temperature lithium ion battery gel electrolyte as well as a preparation method and application thereof. The low-temperature lithium ion battery gel electrolyte comprises a gel polymer and a liquid electrolyte, the gel polymer is prepared from the following raw materials: a thermal initiator, an acrylate compound, and a silane compound and / or a fluorocarboxylate compound. According to the gel electrolyte for the lithium ion battery, provided by the invention, through screening and synergistic compounding of all the components, especially introduction of the acrylate compound, the silane compound and / or the fluorocarboxylate compound, the gel electrolyte for the lithium ion battery has relatively high low-temperature discharge performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion battery electrolytes, and relates to a low-temperature lithium ion battery gel electrolyte, a preparation method and an application thereof, and specifically relates to a low-temperature lithium ion battery gel electrolyte based on in-situ polymerization, a preparation method and an application thereof. Background Art

[0002] Gel electrolyte is a solid-liquid mixed state, which can improve the interfacial stability and high-temperature stability of the battery. However, the liquid electrolyte that plays a transmission role will cause the viscosity of the electrolyte to increase and the fluidity to deteriorate at low temperatures, resulting in a slowdown in ion conduction, which significantly reduces the conductivity of the lithium-ion battery gel electrolyte at low temperatures. Under low temperature conditions, the mismatch in the electron migration speed of the external circuit will cause severe polarization of the battery and a sharp drop in the charge and discharge capacity. In addition, at low temperatures, the compatibility between the electrolyte and the negative electrode and the diaphragm deteriorates, and lithium precipitation at the negative electrode is serious. The precipitated metallic lithium reacts with the electrolyte, resulting in an increase in the thickness of the solid electrolyte interface (SEI), further affecting the conductivity and performance of the battery.

[0003] The polymer gel electrolyte forms a mesh-structured gel tissue in the battery electrodes and separators, which improves the safety of the battery and the stability of the interface. However, since the gel electrolyte is between liquid and solid, the migration of lithium ions at low temperatures will be affected to a certain extent, causing the discharge performance of the gel polymer battery to deteriorate at low temperatures.

[0004] Therefore, it is desirable in the present invention to develop a low-temperature lithium-ion battery gel electrolyte that can improve the low-temperature discharge performance of the gel electrolyte. Summary of the invention

[0005] In view of the shortcomings of the prior art, namely, the problem that the solid-liquid mixed electrolyte has a slow ion conduction speed at low temperature and a significant decrease in low-temperature conductivity, the purpose of the present invention is to provide a low-temperature lithium ion battery gel electrolyte and a preparation method and application thereof. The lithium ion battery gel electrolyte provided by the present invention improves the low-temperature discharge performance of the gel electrolyte by improving the lithium ion conductivity of the gel structure.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a low-temperature lithium-ion battery gel electrolyte, wherein the low-temperature lithium-ion battery gel electrolyte comprises a gel polymer and a liquid electrolyte;

[0008] The raw materials for preparing the gel polymer include a thermal initiator, an acrylate compound, and a silane compound and / or a fluorocarboxylate compound, that is, the raw materials for preparing the gel polymer include a combination of a thermal initiator, an acrylate compound and a silane compound, or a combination of a thermal initiator, an acrylate compound and a fluorocarboxylate compound, or a combination of a thermal initiator, an acrylate compound, a silane compound and a fluorocarboxylate compound.

[0009] The lithium ion battery gel electrolyte provided by the present invention has higher low-temperature discharge performance through the screening and coordinated compounding of various components, especially the introduction of acrylic acid ester compounds, silane compounds and / or fluorocarboxylic acid ester compounds.

[0010] In the present invention, the acrylate compound is used as a cross-linking agent to form a three-dimensional network cross-linked structure skeleton in the gel; the silane compound is used as a silane coupling agent to provide siloxane functional groups in the gel electrolyte, improve the distribution and contact stress of the gel electrolyte at the interface, enhance the uniformity of the gel at the interface, and ensure the rapid transmission of lithium ions along the channel formed by the gel; the fluorocarboxylate compound provides the gel electrolyte with ionic conductivity at low temperature, provides the electrolyte with excellent low-temperature performance, and high antioxidant capacity.

[0011] As a preferred technical solution of the present invention, the raw materials for preparing the gel polymer include a thermal initiator, an acrylate compound, a silane compound and a fluorocarboxylate compound.

[0012] Acrylate compounds act as cross-linking agents and form a three-dimensional network gel structure after thermal polymerization, which provides gel coating on the surface of battery electrode particles and filling of gaps between particles, alleviates the degradation of the surface of electrode active particles and enhances the mechanical strength and flexibility of the battery.

[0013] The silane compound is preferably a siloxane coupling agent containing an unsaturated functional group, which copolymerizes with the acrylate compound at one end of the unsaturated functional group and enters the network gel structure formed by the acrylate compound. The siloxane therein provides a bridging structure with the inorganic particles, enhances the uniformity of the gel at the interface, generates uniform stress at the particle interface, ensures the rapid transmission of lithium ions along the channel formed by the gel, and makes low-temperature discharge easier.

[0014] Fluorinated carboxylic acid ester compounds have a good dielectric constant at low temperatures, which can ensure that the gel electrolyte has a good conductivity at low temperatures.

[0015] Preferably, the acrylate compound includes any one of pentaerythritol tetraacrylate, pentaerythritol triacrylate, propoxylated (3) glycerol triacrylate, trimethylolpropane triacrylate, tripropylene glycol diacrylate, trimethylolpropane trimethacrylate, and ditrimethylolpropane tetraacrylate, or a combination of at least two thereof.

[0016] Preferably, the silane compounds include KH-560 (3-glycidyloxypropyltrimethoxysilane), KH-561 (3-(2,3-epoxypropyloxy)propyltriethoxysilane), KH-562 (3-(2,3-epoxypropyloxy)propylmethyldimethoxysilane), A-151 (vinyltriethoxysilane), A-171 (vinyltrimethoxysilane), A-172 (vinyltri(β-methoxyethoxy)silane), Any one of KH-580 (3-mercaptopropyl triethoxysilane), KH-590 (3-mercaptopropyl trimethoxysilane), Si-69 (bis-[γ-(triethoxysilyl)propyl] tetrasulfide, KH-570 (3-methacryloxypropyl trimethoxysilane), KH-571 (γ-methacryloxypropyl methyldimethoxysilane), and KH-572 (3-methacryloxypropyl triethoxysilane) or a combination of at least two thereof.

[0017] Preferably, the fluorocarboxylic acid ester compound includes any one of methyl difluoroacetate, methyl trifluoroacetate, ethyl difluoroacetate, ethyl trifluoroacetate, methyl difluoropropionate, methyl trifluoropropionate, ethyl difluoropropionate, ethyl trifluoropropionate, methyl difluorobutyrate, methyl trifluorobutyrate, ethyl difluorobutyrate, and ethyl trifluorobutyrate, or a combination of at least two thereof.

[0018] Preferably, the thermal initiator includes any one of azobisisobutyronitrile, dibenzoyl peroxide, di(4-tert-butylcyclohexyl)peroxydicarbonate, dodecanoyl peroxide, and diisopropyl peroxydicarbonate, or a combination of at least two thereof.

[0019] Preferably, the raw materials for preparing the gel polymer include, by weight: 0.5-10 parts of acrylate compounds (e.g., 0.5 parts, 1 parts, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, etc.), 0-10 parts of silane compounds (e.g., 0 parts, 0.1 parts, 0.2 parts, 0.3 parts, 0.5 parts, 1 parts, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, etc.), 0-30 parts of fluorocarboxylate compounds (e.g., 0 parts, 0.2 parts, 0.3 parts, 0.5 parts, etc.), , 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, etc.), 0.05-2 parts of thermal initiator (for example, 0.05 parts, 0.08 parts, 0.1 parts, 0.3 parts, 0.5 parts, 0.8 parts, 1 part, 1.2 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 2 parts, etc.), and the amount of silane compound and fluorocarboxylate compound cannot be 0 parts at the same time.

[0020] Preferably, the liquid electrolyte comprises a lithium salt, a film-forming additive and an organic solvent.

[0021] Preferably, the lithium salt includes any one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluorophosphoryl)imide, lithium bis(oxalatoborate), lithium hexafluorophosphate or lithium tetrafluoroborate, or a combination of at least two thereof.

[0022] Preferably, the lithium salt is, for example, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluorophosphoryl)imide, lithium bis(oxalatoborate), lithium hexafluorophosphate, lithium tetrafluoroborate, a combination of lithium bis(trifluoromethanesulfonyl)imide and lithium bis(trifluorophosphoryl)imide.

[0023] Preferably, the film-forming additive includes any one of vinylene carbonate, fluoroethylene carbonate, vinyl sulfate, 1,3-propane sultone, lithium bis(oxalatoborate), lithium tetrafluoroborate, 1,3-propenyl-sultone, methylene disulfonate, lithium difluorophosphate or lithium difluorooxalatoborate, or a combination of at least two thereof.

[0024] Preferably, the organic solvent includes any one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl acetate, ethyl propionate, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,2-dimethoxyethane, acetone, acetonitrile, methyl acetate, ethyl acetate, methyl propionate, tetrahydrofuran or 2-methyltetrahydrofuran, or a combination of at least two thereof.

[0025] Preferably, the organic solvent is, for example, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl acetate, ethyl propionate, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,2-dimethoxyethane, acetone, acetonitrile, methyl acetate, ethyl acetate, methyl propionate, tetrahydrofuran, 2-methyltetrahydrofuran, ethylene carbonate and ethyl methyl carbonate, ethylene carbonate and propylene carbonate, dimethyl carbonate and diethyl carbonate, ethyl methyl carbonate and ethyl acetate, ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, or a combination of ethyl methyl carbonate, ethyl acetate and ethyl propionate.

[0026] Preferably, the raw materials for preparing the low-temperature lithium-ion battery gel electrolyte include the following components by weight percentage:

[0027]

[0028] The rest is organic solvent;

[0029] Furthermore, the added amounts of the silane compound and the fluorocarboxylate compound cannot be zero at the same time.

[0030] Preferably, the raw materials for preparing the low-temperature lithium-ion battery gel electrolyte are measured by weight percentage, and the amount of lithium salt used can be 5%, 6%, 7%, 8%, 9%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 45%, etc., and the amount of film-forming additives used can be 5%, 6%, 7%, 8%, 9%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 45%, etc. The amount of the thermal initiator can be 0.05%, 0.08%, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc. The amount of the acrylate compound can be 0.5 %, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, etc., and the amount of silane compound can be 0, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 1 0%, etc., the amount of the fluorocarboxylate compound can be 0, 0.3%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, etc., and the rest is an organic solvent, and the added amounts of the silane compound and the fluorocarboxylate compound cannot be 0 at the same time.

[0031] In a second aspect, the present invention provides a method for preparing a low-temperature lithium-ion battery gel electrolyte as described in the first aspect, the preparation method comprising the following steps:

[0032] (1) mixing a raw material for preparing a liquid electrolyte, a thermal initiator, an acrylate compound, and a silane compound and / or a fluorocarboxylate compound to obtain a mixed solution;

[0033] (2) Injecting the mixed solution into a battery cell, and after standing for a while, performing heat-pressing to initiate polymerization to form the low-temperature lithium-ion battery gel electrolyte in the battery cell.

[0034] The low-temperature lithium ion battery gel electrolyte provided by the invention is prepared based on in-situ polymerization.

[0035] Preferably, the standing time is 40 to 50 h, for example, 40 h, 41 h, 42 h, 43 h, 44 h, 45 h, 46 h, 47 h, 48 h, 49 h or 50 h.

[0036] Preferably, the hot pressing is carried out in a forming cabinet.

[0037] Preferably, the hot pressing temperature is 70-90°C, for example, 70°C, 72°C, 74°C, 76°C, 78°C, 80°C, 82°C, 84°C, 86°C, 88°C or 90°C, and the hot pressing time is 0.2-2h, for example, 0.2h, 0.5h, 1h, 1.5h, 2h, etc.

[0038] The key point of the present invention is that a three-dimensional cross-linked bridging structure with a silicon-oxygen bond is formed in the battery through in-situ polymerization, which can enhance the interaction at the interface and promote the generation of uniform stress on the particle surface. The siloxane bond solves the problem of incomplete gel polymerization and ensures that Li + The rapid transmission makes the battery have smaller interface impedance and better low-temperature discharge performance, and the fluorinated carboxylic acid ester compounds provide better conductivity at low temperatures.

[0039] In a third aspect, the present invention provides a use of the low-temperature lithium-ion battery gel electrolyte as described in the first aspect in a lithium-ion battery (eg, a lithium-ion silicon negative electrode battery, etc.).

[0040] Preferably, the battery containing the low-temperature lithium-ion battery gel electrolyte in the battery core is placed at room temperature and then subjected to conventional formation, high-temperature aging, vacuum pumping and capacity separation, and finally battery packaging to prepare a finished lithium-ion battery.

[0041] Preferably, the voltage upper limit of the conventional formation is 3.8V, and the charging current is 0.1C and 0.2C.

[0042] Preferably, the high temperature aging temperature is 40-50°C, for example, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C or 50°C, and the high temperature aging time is 20-30h, for example, 20h, 21h, 22h, 23h, 24h, 25h, 26h, 27h, 28h, 29h or 30h, etc.

[0043] Preferably, the vacuum degree of the vacuum pumping is 70-100 kPa, for example, 70 kPa, 75 kPa, 80 kPa, 85 kPa, 90 kPa, 95 kPa, 100 kPa, etc., and the vacuum pumping time is 3-10 s, for example, 3 s, 4 s, 5 s, 6 s, 7 s, 8 s, 9 s or 10 s, etc.

[0044] Compared with the prior art, the present invention has at least the following beneficial effects:

[0045] The lithium ion battery gel electrolyte provided by the present invention has higher low-temperature discharge performance through the screening and coordinated compounding of various components, especially the introduction of acrylic acid ester compounds, silane compounds and / or fluorocarboxylic acid ester compounds. DETAILED DESCRIPTION

[0046] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0047] Example 1

[0048] In this embodiment, a low-temperature lithium-ion battery gel electrolyte is provided, wherein the low-temperature lithium-ion battery gel electrolyte comprises a gel polymer and a liquid electrolyte;

[0049] The raw materials for preparing the low-temperature lithium-ion battery gel electrolyte include the following components by weight percentage:

[0050]

[0051] The rest is organic solvent;

[0052] Among them, the lithium salt is lithium hexafluorophosphate; the film-forming additive is a mixture of vinylene carbonate, lithium difluorophosphate and lithium difluorooxalatoborate in a mass ratio of 2:1:1; the thermal initiator is azobisisobutyronitrile; the acrylate compound is pentaerythritol tetraacrylate; the silane compound is 3-methacryloxypropyltrimethoxysilane; and the organic solvent is a mixed solvent of vinyl carbonate and ethyl methyl carbonate in a mass ratio of 3:7.

[0053] The preparation method comprises the following steps:

[0054] (1) mixing an organic solvent and a lithium salt, and stirring until the lithium salt is completely dissolved; then adding a film-forming additive and a thermal initiator, and stirring thoroughly; finally adding an acrylic acid ester compound and a silane compound, and stirring thoroughly to obtain a mixed solution;

[0055] (2) The mixed solution is injected into a battery cell, allowed to stand for 45 hours, and then hot-pressed in a formation cabinet at 85° C. for 0.5 hours to initiate polymerization, thereby forming the low-temperature lithium-ion battery gel electrolyte in the battery cell.

[0056] In this embodiment, a lithium ion gel battery is also provided, and a preparation method thereof comprises the following steps:

[0057] The gel battery after thermal polymerization is placed at room temperature and then subjected to conventional formation, with the upper limit of the formation voltage being 3.8V and the charging current being 0.1C and 0.2C;

[0058] The formed battery is subjected to high temperature aging at 45°C for 24 hours.

[0059] After aging, vacuum pumping is performed with a vacuum degree of 88 kPa and a vacuum pumping time of 5 s. The film formation potential data is checked, the battery quality is checked, and the battery liquid absorption amount is estimated.

[0060] Finally, the battery is divided into different capacities, with the currents being 0.2C and 0.5C respectively. After two weeks of cyclic charge and discharge, the battery manufacturing process is completed and a finished lithium-ion gel battery is obtained.

[0061] Examples 2-8, Comparative Example 1

[0062] The only difference between Examples 2-8 and Comparative Example 1 and Example 1 is that the types and / or amounts (%) of the polymerization monomers of the gel polymer are different, as shown in Table 1. The contents not shown in Table 1 are deemed to be the same as those in Example 1; the “ / ” in Table 1 indicates that the corresponding raw materials are not added.

[0063] The preparation method is as in Example 1.

[0064] Test cell information

[0065] The battery cells used in the above embodiments and comparative examples are: positive electrode material ternary 811 (Rongbai Technology), negative electrode material S420A (B&T), and the separator is a polypropylene separator. It should be noted that the electrolyte provided in the present invention is not only suitable for S420A negative electrode, but also has the effect of protecting the particle surface in negative electrodes with higher silicon content or graphite negative electrodes.

[0066] Performance Testing

[0067] Test method for low temperature discharge performance

[0068] The battery cell is charged to 4.2V at 1C constant current and constant voltage at an ambient temperature of 25±2, with a cut-off current of 0.05C. It is placed in a -10℃ or -20℃ low-temperature box for 4h, and discharged at 0.2C to a cut-off voltage of 2.75V to obtain the low-temperature discharge capacity.

[0069] The performance test results are shown in Table 1.

[0070] Table 1

[0071]

[0072] It can be seen from Table 1 that the batteries prepared by the gel electrolyte provided by the embodiments of the present invention have good low-temperature discharge performance (-10°C discharge capacity retention rate: 87.3% to 94.2%, preferably 93.4% to 94.2%; -20°C discharge capacity retention rate: 78.9% to 92.1%, preferably 91.0% to 92.1%).

[0073] Compared with Example 1, the low-temperature discharge performance of the battery prepared by the gel electrolyte provided in Comparative Example 1 is significantly deteriorated.

[0074] The applicant declares that the present invention uses the above-mentioned embodiments to illustrate the low-temperature lithium-ion battery gel electrolyte and its preparation method and application, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A low-temperature lithium-ion battery gel electrolyte, characterized in that: The low-temperature lithium-ion battery gel electrolyte comprises a gel polymer and a liquid electrolyte; The raw materials for preparing the gel polymer include a thermal initiator, an acrylate compound, and a silane compound and / or a fluorocarboxylate compound.

2. The low-temperature lithium-ion battery gel electrolyte according to claim 1, characterized in that: The raw materials for preparing the gel polymer include a thermal initiator, an acrylate compound, a silane compound and a fluorocarboxylate compound.

3. The low-temperature lithium-ion battery gel electrolyte according to claim 1 or 2, characterized in that: The acrylate compound includes any one of pentaerythritol tetraacrylate, pentaerythritol triacrylate, propoxylated (3) glycerol triacrylate, trimethylolpropane triacrylate, tripropylene glycol diacrylate, trimethylolpropane trimethacrylate, and ditrimethylolpropane tetraacrylate, or a combination of at least two thereof; Preferably, the silane compound includes any one of KH-560, KH-561, KH-562, A-151 (vinyl triethoxysilane), A-171, A-172, KH-580, KH-590, Si-69 (bis-[γ-(triethoxysilyl)propyl] tetrasulfide, KH-570, KH-571, KH-572, or a combination of at least two thereof; Preferably, the fluorocarboxylic acid ester compound includes any one of methyl difluoroacetate, methyl trifluoroacetate, ethyl difluoroacetate, ethyl trifluoroacetate, methyl difluoropropionate, methyl trifluoropropionate, ethyl difluoropropionate, ethyl trifluoropropionate, methyl difluorobutyrate, methyl trifluorobutyrate, ethyl difluorobutyrate, and ethyl trifluorobutyrate, or a combination of at least two thereof; Preferably, the thermal initiator includes any one of azobisisobutyronitrile, dibenzoyl peroxide, di(4-tert-butylcyclohexyl)peroxydicarbonate, dodecanoyl peroxide, and diisopropyl peroxydicarbonate, or a combination of at least two thereof.

4. The low-temperature lithium-ion battery gel electrolyte according to any one of claims 1 to 3, characterized in that: The raw materials for preparing the gel polymer include, by weight, 0.5-10 parts of acrylate compounds, 0-10 parts of silane compounds, 0-30 parts of fluorocarboxylate compounds, and 0.05-2 parts of thermal initiator, and the amounts of silane compounds and fluorocarboxylate compounds cannot be 0 parts at the same time.

5. The low-temperature lithium-ion battery gel electrolyte according to any one of claims 1 to 4, characterized in that: The liquid electrolyte comprises a lithium salt, a film-forming additive and an organic solvent.

6. The low-temperature lithium-ion battery gel electrolyte according to claim 5, characterized in that: The lithium salt includes any one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluorophosphoryl)imide, lithium bis(oxalatoborate), lithium hexafluorophosphate or lithium tetrafluoroborate, or a combination of at least two thereof; Preferably, the film-forming additive includes any one of vinylene carbonate, fluoroethylene carbonate, vinyl sulfate, 1,3-propane sultone, lithium bis(oxalatoborate), lithium tetrafluoroborate, 1,3-propenyl-sultone, methylene disulfonate, lithium difluorophosphate or lithium difluorooxalatoborate, or a combination of at least two thereof; Preferably, the organic solvent includes any one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl acetate, ethyl propionate, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,2-dimethoxyethane, acetone, acetonitrile, methyl acetate, ethyl acetate, methyl propionate, tetrahydrofuran or 2-methyltetrahydrofuran, or a combination of at least two thereof.

7. The low-temperature lithium-ion battery gel electrolyte according to any one of claims 1 to 6, characterized in that: The raw materials for preparing the low-temperature lithium-ion battery gel electrolyte include the following components by weight percentage: Lithium salt 5%-45%; Film-forming additives 0.1%-10%; Thermal initiator 0.05%-2%; Acrylate compounds 0.5%-10%; The rest is organic solvent; Furthermore, the added amounts of the silane compound and the fluorocarboxylate compound cannot be zero at the same time.

8. A method for preparing a low-temperature lithium-ion battery gel electrolyte as claimed in any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: (1) mixing a raw material for preparing a liquid electrolyte, a thermal initiator, an acrylate compound, and a silane compound and / or a fluorocarboxylate compound to obtain a mixed solution; (2) The mixed solution is injected into a battery cell, and after standing for a while, heat-pressing and initiating polymerization is performed to form the low-temperature lithium-ion battery gel electrolyte in the battery cell.

9. The preparation method according to claim 8, characterized in that: The standing time is 40 to 50 hours; Preferably, the hot pressing is carried out in a forming cabinet; Preferably, the hot pressing temperature is 70-90° C., and the hot pressing time is 0.2-2 h.

10. Use of the low-temperature lithium-ion battery gel electrolyte according to any one of claims 1 to 7 in a lithium-ion battery; Preferably, the battery containing the low-temperature lithium-ion battery gel electrolyte in the battery core is placed at room temperature, and then subjected to conventional formation, high-temperature aging, vacuum pumping and capacity separation, and finally battery packaging to prepare a finished lithium-ion battery; Preferably, the voltage upper limit of the conventional formation is 3.8V, and the charging current is 0.1C and 0.2C; Preferably, the high temperature aging temperature is 40-50°C, and the high temperature aging time is 20-30h; Preferably, the vacuum degree of the vacuum pumping is 70-100 kPa, and the vacuum pumping time is 3-10 s.

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