Ionic gel phase change electrolyte, preparation method thereof and lithium battery

Abstract

The present application relates to the technical field of battery, especially to an ionic gel phase change electrolyte, a preparation method thereof and a lithium battery, and provides the ionic gel phase change electrolyte, which comprises the following components in mass fraction: 50-70 parts of ionic liquid, 9-20 parts of organic solvent, 10-20 parts of block copolymer, 5-15 parts of lithium salt, 0.5-4 parts of additive and 0.5-2 parts of crosslinking agent; the general formula of the block copolymer is P(IPOx a -co-NPOx 1‑a ) m -b-PEO k -b-P(IPOx a -co-NPOx 1‑a ) p ; wherein IPOx is isopropyl oxazoline, NPOx is n-propyl oxazoline; a is the mole fraction of IPOx, 0

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to an ion gel phase change electrolyte, its preparation method, and a lithium battery. Background Technology

[0002] With the rapid development and widespread adoption of the new energy vehicle industry, the environmental adaptability and safety of power batteries have become key challenges for the industry's further development. Currently, mainstream liquid electrolyte systems can maintain relative stability at low temperatures, but their safety is relatively poor. While solid-state batteries have significantly improved safety performance, their charge-discharge efficiency and ionic conductivity at low temperatures are generally poor, becoming a major bottleneck restricting their commercial application. Therefore, developing an electrolyte material that can ensure high safety while possessing excellent low-temperature electrochemical performance has become an urgent task to promote the advancement of power battery technology and industrial upgrading. This will not only help alleviate the range anxiety of current new energy vehicle users in extreme environments, but will also provide an important direction for the development of next-generation high-energy-density, high-safety battery systems.

[0003] Smart responsive materials are materials that can sense changes in the external environment (such as temperature, light, force, pH, electric field, magnetic field, etc.) and actively respond intelligently with changes in shape, transparency, etc., achieving a smart closed-loop function of "sensing-response-regulation". Materials exhibiting the LCST (low critical solution temperature) phenomenon are typical smart responsive materials. The core characteristic of this phenomenon is that as the temperature increases, phase separation occurs in the system; as the temperature decreases, the solubility increases, transforming from a two-phase separated state into a completely miscible homogeneous solution. This is the most typical "anomalous" phase behavior of temperature-sensitive polymers and solution systems.

[0004] Ionic gels are soft materials composed of ionic liquids and three-dimensional polymer networks. By immobilizing the ionic liquid in the cross-linked polymer network, the intrinsic advantages of the ionic liquid are retained and enhanced, and it possesses mechanical strength, elasticity and shape stability similar to solids. This material system can be used to construct ionic gel phase change electrolytes.

[0005] The challenges in developing ion-gel phase change electrolytes that combine high safety and low-temperature performance are mainly concentrated in two aspects. First, existing technologies generally favor high-temperature phase changes, making it difficult to achieve low-temperature phase changes in organic solvents. Second, there is the performance balance between mechanical properties and ionic conductivity. Enhancing mechanical properties usually restricts polymer chain movement, hinders ion transport, and leads to a decrease in ionic conductivity. Conversely, increasing the ionic liquid content to improve conductivity often results in a loose material skeleton and deterioration of mechanical properties.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] A first object of the present invention is to provide an ionic gel phase-change electrolyte, which achieves phase change at a low temperature of 10 to 40°C, and can maintain high ionic conductivity before and after the phase change; solves the problem of incompatibility between low-temperature performance and operational safety of batteries.

[0008] A second object of the present invention is to provide a preparation method of the above ionic gel phase-change electrolyte.

[0009] A third object of the present invention is to provide a lithium battery.

[0010] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted: The present invention provides an ionic gel phase-change electrolyte, comprising the following components in parts by mass: 50 to 70 parts of ionic liquid, 9 to 20 parts of organic solvent, 10 to 20 parts of block copolymer, 5 to 15 parts of lithium salt, 0.5 to 4 parts of additive and 0.5 to 2 parts of crosslinking agent; The general formula of the block copolymer is P(IPOx a -co-NPOx 1-a ) m -b-PEO k -b-P(IPOx a -co-NPOx 1-a ) p ; wherein, IPOx is isopropyl oxazoline, NPOx is n-propyl oxazoline; a is the molar fraction of IPOx, 0<a<1; m, p and k are degrees of polymerization, m and p are each independently an integer between 5 and 200, and k is an integer between 20 and 1000.

[0011] Further, the ionic liquid comprises an anion and a cation; the anion comprises F - , [BF4] - , [PF6] - , [NTf2] - and [FSI] - at least one of; the cation comprises a cation having a structure shown in formula (I) and / or formula (II); (I); (II); wherein n is an integer between 1 and 5.

[0012] Further, the organic solvent comprises at least one of tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane and ethylene glycol dimethyl ether.

[0013] Furthermore, the lithium salt includes at least one of LiFSI, LiTFSI, LiDFOB, LiBOB, LiCF3SO3, LiPF6, and LiBF4.

[0014] Further, the crosslinking agent includes at least one of polyethylene glycol diglycidyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, triethylene glycol diacrylate, and diethylene glycol diacrylate.

[0015] Furthermore, the additive includes at least one of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, fluoroethylene glycol dimethyl ether, and tris(trimethylsilyl)phosphate.

[0016] The present invention also provides a method for preparing the ion gel phase change electrolyte as described above, comprising the following steps: The ionic liquid, organic solvent, block copolymer, lithium salt and additives are mixed and then a crosslinking agent is added and mixed to obtain the ion gel phase change electrolyte.

[0017] The present invention also provides a lithium battery, comprising a positive electrode, a negative electrode, and an ion gel phase change electrolyte as described above.

[0018] Furthermore, the positive electrode includes at least one of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, and ternary materials.

[0019] Furthermore, the negative electrode comprises at least one of natural graphite, artificial graphite, silicon, and metallic lithium.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention constructs an ion gel phase change electrolyte based on the low critical solution temperature (LCST) behavior of ion gels. Through the design of block copolymers, a phase change is achieved under low-temperature conditions, enabling the electrolyte to exhibit a high-viscosity fluid state at low temperatures, maintaining good interfacial contact with the electrodes and thus effectively improving the low-temperature performance of the battery. Under high-temperature conditions, it transforms into a stable gel state, significantly enhancing the mechanical stability and safety of the electrolyte. In addition, by constructing a bicontinuous phase structure, the ion transport channels are ensured to remain after the phase change, effectively preventing excessive decrease in ionic conductivity. Detailed Implementation

[0021] Hereinafter, the technical solution of the present invention will be clearly and completely described with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some rather than all embodiments of the present invention. They are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention. If no specific conditions are indicated in the embodiments, the procedures are carried out in accordance with conventional conditions or the conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments used are not specified, they are conventional products that can be obtained commercially.

[0022] In some embodiments of the present invention, there is provided an ionic gel phase-change electrolyte, which comprises the following components in parts by mass: 50 to 70 parts of ionic liquid, 9 to 20 parts of organic solvent, 10 to 20 parts of block copolymer, 5 to 15 parts of lithium salt, 0.5 to 4 parts of additive and 0.5 to 2 parts of crosslinking agent; The general formula of the block copolymer is P(IPOx a -co-NPOx 1-a ) m -b-PEO k -b-P(IPOx a -co-NPOx 1-a ) p ; wherein, IPOx is isopropyl oxazoline, NPOx is n-propyl oxazoline; a is the mole fraction of IPOx, 0<a<1; m, p and k are degrees of polymerization, m and p are each independently an integer between 5 and 200, and k is an integer between 20 and 1000.

[0023] Based on the lower critical solution temperature (LCST) behavior of ionic gels, the present invention constructs an ionic gel phase-change electrolyte, which solves the problem of incompatibility between low-temperature performance and application safety of batteries, which is specifically manifested in the following two aspects: Phase change under low-temperature conditions (10 to 40°C) is realized, and the safe application range of the battery is broadened: by combining ionic liquid, block copolymer, lithium salt and additives, a temperature phase-change electrolyte is prepared and applied to lithium batteries; through gradient design of the copolymerization sequence of the block polymer, and by adjusting the proportion, molecular weight and other parameters of the block copolymer, phase change is realized within the range of 10 to 40°C. Below the phase transition temperature, the electrolyte presents a high-viscosity flow state, has high ionic conductivity, and maintains good contact with electrodes at the same time; above the phase transition temperature, it is an ionic gel and has certain mechanical properties.

[0024] To achieve high ionic conductivity before and after phase transition: By adjusting the block copolymer chain length and polymer molecular structure, a bicontinuous phase structure is constructed, and additives are used to ensure that the lithium-ion transport channels are unobstructed after the electrolyte undergoes phase transition, resulting in high ionic conductivity retention and enabling the battery to maintain good working performance.

[0025] In some embodiments of the present invention, in the ion gel phase change electrolyte, typically but not limitingly, for example, the mass fraction of the ionic liquid can be 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, and any value between any two of these; the mass fraction of the organic solvent can be 9 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, and any value between any two of these; the mass fraction of the block copolymer can be 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, and any value between any two of these; the mass fraction of the lithium salt can be 5 parts, 7 parts, 8 parts, 11 parts, 13 parts, 15 parts, and any value between any two of these; the mass fraction of the additive can be 0.5 parts, 1 part, 2 parts, 3 parts, 4 parts, and any value between any two of these; the mass fraction of the crosslinking agent can be 0.5 parts, 0.8 parts, 1 part, 2 parts, and any value between any two of these.

[0026] In some embodiments of the invention, in the block copolymer, typically but not limitingly, for example, a can be any value between 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and any two thereof; m and p can each independently be any value between 5, 10, 30, 50, 70, 90, 110, 130, 150, 170, 200, and any two thereof; m and p can be the same or different; k can be any value between 20, 100, 300, 500, 800, 1000, and any two thereof.

[0027] In some embodiments of the present invention, the block copolymer P(IPOx) a -co-NPOx 1-a ) m -b-PEO k -bP(IPOx a -co-NPOx 1-a ) p The preparation method of the ABA-type triblock copolymer includes the following steps: S1, dihydroxy-terminated PEO and p-toluenesulfonyl chloride (TsCl) were reacted in anhydrous dichloromethane at 20-30°C for 20-30 h under triethylamine catalysis to obtain PEO(OTs)2 activated by p-toluenesulfonate; wherein the molar ratio of PEO (based on hydroxyl groups), TsCl and triethylamine was 1:3:4. S2, PEO(OTs)2, IPOx and NPOx activated by p-toluenesulfonate were reacted in anhydrous acetonitrile at 95~105℃ for 45~50h to obtain a block copolymer; wherein the molar ratio (m, p, a) of PEO(OTs)2, IPOx and NPOx activated by p-toluenesulfonate were adjusted according to the target degree of polymerization and copolymer composition.

[0028] By designing a gradient of the copolymerization sequence of block copolymers and controlling the ratio of IPOx (isopropyl oxazoline) to NPOx (n-propyl oxazoline), the continuous variation of polymer chain segments is achieved, overcoming the limitation of the narrow phase transition temperature range of traditional random copolymerization systems and realizing precise control of phase transition temperature.

[0029] By utilizing the distinct temperature response characteristics of P(IPOx-co-NPOx) and PEO in ionic liquids in block copolymers, a bicontinuous phase structure was constructed in which the "polymer rigid skeleton enriched phase" and the "ionic liquid conductive enriched phase" interpenetrate each other. During the process of heating to LCST, P(IPOx-co-NPOx) rapidly aggregates, while PEO maintains good affinity with the ionic liquid, ensuring that the lithium-ion transport channel remains unobstructed, thus achieving a perfect decoupling of high ionic conductivity and mechanical strength.

[0030] P(IPOx a -co-NPOx 1-a ) m -b-PEO k -bP(IPOx a -co-NPOx 1-a ) p In-situ reinforcement mechanism of triblock copolymers in ionic liquid systems: At low temperatures, ionic liquid cations adsorb onto polymer segments through strong ion-dipole interactions to form a solvation layer, resulting in a high-viscosity fluid. When the temperature rises to the LCST range, the P(IPOx-co-NPOx) blocks collapse and aggregate into physically cross-linked microdomains, which both tighten the PEO midsegments to build a high-strength and tough network and enhance the cross-linking effect through dipole interactions. Dipole interaction inhibits chain segment relaxation, enabling in-situ sol-gel transformation and ultimately obtaining an ionic gel with both high ionic conductivity and excellent mechanical strength.

[0031] In some embodiments of the present invention, the ionic liquid includes anions and cations; the anions include F... - [BF4] - [PF6] - [NTf2] - and [FSI] - At least one of the following; the cation includes a cation having the structure shown in formula (I) and / or formula (II); (I); (II); where n is an integer between 1 and 5, for example, 1, 2, 3, 4 or 5.

[0032] In some embodiments of the present invention, the organic solvent includes ether solvents.

[0033] In some embodiments of the present invention, the organic solvent includes at least one of tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, and ethylene glycol dimethyl ether.

[0034] In some embodiments of the present invention, the lithium salt includes at least one of LiFSI, LiTFSI, LiDFOB, LiBOB, LiCF3SO3, LiPF6 and LiBF4.

[0035] In some embodiments of the present invention, the crosslinking agent includes at least one selected from polyethylene glycol diglycidyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, triethylene glycol diacrylate, and diethylene glycol diacrylate.

[0036] In some embodiments of the present invention, the additive includes at least one selected from 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, fluoroethylene glycol dimethyl ether, and tris(trimethylsilyl)phosphate.

[0037] In some embodiments of the present invention, a method for preparing the above-mentioned ion gel phase change electrolyte is also provided, comprising the following steps: After mixing ionic liquid, organic solvent, block copolymer, lithium salt and additives, a crosslinking agent is added and mixed again to obtain ion gel phase change electrolyte.

[0038] In some embodiments of the present invention, a lithium battery is also provided, comprising a positive electrode, a negative electrode, and the above-described ion gel phase change electrolyte.

[0039] The application of the ion gel phase change electrolyte of the present invention in lithium batteries solves the problem of incompatibility between low-temperature performance and safety of lithium batteries.

[0040] In some embodiments of the present invention, the positive electrode includes at least one of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, and ternary materials.

[0041] In some embodiments of the present invention, the negative electrode includes at least one of natural graphite, artificial graphite, silicon, and metallic lithium.

[0042] In some embodiments of the present invention, the lithium battery further includes a separator, which includes at least one of polyethylene, polypropylene, polyimide, polyamide and polytetrafluoroethylene.

[0043] This invention does not impose strict limitations on the positive electrode, negative electrode, and separator of lithium batteries; conventional products can be used.

[0044] Some embodiments of the present invention also provide a method for preparing the above-mentioned lithium battery, comprising the following steps: The above-mentioned ion gel phase change electrolyte is added to the battery casing composed of positive electrode, negative electrode and separator to assemble a lithium battery.

[0045] Block copolymer P(IPOx) a -co-NPOx 1-a ) m -b-PEO k -bP(IPOx a -co-NPOx 1-a ) p The preparation method includes the following steps: S1, dihydroxy-terminated PEO and p-toluenesulfonyl chloride (TsCl) were reacted in anhydrous dichloromethane at 25°C for 24 h under triethylamine catalysis to obtain a reaction solution; wherein the molar ratio of dihydroxy-terminated PEO (based on hydroxyl groups), TsCl and triethylamine was 1:3:4, and the mass ratio of anhydrous dichloromethane to dihydroxy-terminated PEO was 60:1. The reaction solution was quenched with deionized water, washed successively with saturated sodium bicarbonate solution and saturated brine, dried with anhydrous magnesium sulfate, concentrated and precipitated in excess ice-cold ether to obtain PEO(OTs)2 activated by p-toluenesulfonate. S2. Under nitrogen protection, PEO(OTs)2, IPOx, and NPOx are reacted in anhydrous acetonitrile at 100°C for 48 hours to obtain a reaction solution; the molar ratio (m, p, a) of PEO(OTs)2, IPOx, and NPOx is adjusted according to the target degree of polymerization and copolymer composition; the mass ratio of anhydrous acetonitrile to PEO(OTs)2 is 11:1; Deionized water was added to the reaction solution to terminate the polymerization (the amount of water was 0.5 to 1 times the mass of PEO(OTs)2). The solution was concentrated by rotary evaporation to 1 / 5 to 1 / 3 of its original volume. The solution was then precipitated in excess diethyl ether. The precipitate was redissolved in dichloromethane (the mass ratio of dichloromethane to PEO(OTs)2 was 5:1 to 10:1) and then precipitated again in excess diethyl ether. The solution was then dried under vacuum to obtain the target block copolymer.

[0046] The block copolymers in each embodiment and comparative example were all prepared according to the above method, and the molar ratio or mass ratio of reactants and solvents remained consistent. Only the degree of polymerization of PEO and the molar ratio of monomers (m, p, a) were adjusted according to the target degree of polymerization and copolymer composition of each embodiment.

[0047] Example 1 The method for preparing ion-gel phase change electrolyte provided in this embodiment includes the following steps: In an argon-filled glove box (at a constant temperature of 5°C), 60 parts of ionic liquid, 10 parts of tetrahydrofuran, 15 parts of block copolymer, 12 parts of LiFSI, and 1.5 parts of fluorinated ethylene glycol dimethyl ether were added sequentially to a beaker. The mixture was stirred for 4-6 hours until a completely clear solution was formed. Then, 1.5 parts of polyethylene glycol diglycidyl ether were added and the mixture was stirred for 0.5 hours to obtain an ion gel phase change electrolyte. Among them, the cation of ionic liquid is n is 3; the anion is [NTf2]. - ; The block copolymer is P(IPOx) a -co-NPOx 1-a ) m -b-PEO k -bP(IPOx a -co-NPOx 1-a ) p , a=0.5, m=100, k=300, p=100.

[0048] The lithium battery preparation method provided in this embodiment includes the following steps: The above-mentioned ion gel phase change electrolyte is added to a battery casing composed of a lithium iron phosphate cathode, a lithium metal anode, and a polyethylene separator to assemble a lithium battery.

[0049] Example 2 The method for preparing ion-gel phase change electrolyte provided in this embodiment includes the following steps: In an argon-filled glove box (at a constant temperature of 5°C), 63 parts of ionic liquid, 9 parts of 2-methyltetrahydrofuran, 12 parts of block copolymer, 8 parts of LiTFSI, 5 parts of LiFSI, 1 part of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and 0.8 parts of fluoroethylene glycol dimethyl ether were added sequentially to a beaker. The mixture was stirred for 4-6 hours until a completely clear solution was formed. Then, 1.2 parts of polyethylene glycol diglycidyl ether were added and the mixture was stirred for 0.5 hours to obtain an ion gel phase change electrolyte. Among them, the cation of ionic liquid is n is 5; the anion is [FSI]. - ; The block copolymer is P(IPOx) a -co-NPOx 1-a ) m -b-PEO k -bP(IPOx a -co-NPOx 1-a ) p, a=0.3, m=80, k=300, p=80.

[0050] The method for preparing the lithium battery provided in this embodiment is the same as in Embodiment 1.

[0051] Example 3 The method for preparing ion-gel phase change electrolyte provided in this embodiment includes the following steps: In an argon-filled glove box (at a constant temperature of 5°C), 55 parts of ionic liquid, 13 parts of ethylene glycol dimethyl ether, 18 parts of block polymer, 10 parts of LiPF6, and 2 parts of tris(trimethylsilyl)phosphate were added sequentially to a beaker. The mixture was stirred for 4-6 hours until a completely clear solution was formed. Then, 2 parts of triethylene glycol diacrylate were added and stirred for 0.5 hours to obtain an ion gel phase change electrolyte. Among them, the cation of ionic liquid is n is 3; the anion is F - ; The block copolymer is P(IPOx) a -co-NPOx 1-a ) m -b-PEO k -bP(IPOx a -co-NPOx 1-a ) p , a=0.7, m=150, k=500, p=120.

[0052] The method for preparing the lithium battery provided in this embodiment is the same as in Embodiment 1.

[0053] Comparative Example 1 The preparation method of the ion gel phase change electrolyte provided in this comparative example includes the following steps: In an argon-filled glove box (at a constant temperature of 5°C), 61.5 parts of ionic liquid, 10 parts of tetrahydrofuran, 15 parts of block copolymer, 12 parts of LiFSI, and 1.5 parts of fluorinated ethylene glycol dimethyl ether were added sequentially to a beaker. The mixture was stirred for 4-6 hours until a completely clear solution was formed, thus obtaining an ion gel phase change electrolyte. Among them, the cation of ionic liquid is n is 3; the anion is [NTf2]. - ; The block copolymer is P(IPOx) a -co-NPOx 1-a ) m -b-PEO k -bP(IPOx a -co-NPOx 1-a ) p , a=0.5, m=100, k=300, p=100.

[0054] The method for preparing the lithium battery provided in this comparative example is the same as that in Example 1.

[0055] Comparative Example 2 The preparation method of the ion gel phase change electrolyte provided in this comparative example includes the following steps: In an argon-filled glove box (at a constant temperature of 5°C), 75 parts of ionic liquid, 9 parts of 2-methyltetrahydrofuran, 8 parts of LiTFSI, 5 parts of LiFSI, 1 part of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and 0.8 parts of fluoroethylene glycol dimethyl ether were added sequentially to a beaker. The mixture was stirred for 4-6 hours until a completely clear solution was formed. Then, 1.2 parts of polyethylene glycol diglycidyl ether were added and the mixture was stirred for 0.5 hours to obtain an ion gel phase change electrolyte. Among them, the cation of ionic liquid is n is 5; the anion is [FSI]. - .

[0056] The method for preparing the lithium battery provided in this comparative example is the same as that in Example 1.

[0057] Comparative Example 3 The preparation method of the ion gel phase change electrolyte provided in this comparative example includes the following steps: In an argon-filled glove box (at a constant temperature of 5°C), 60 parts of ionic liquid, 10 parts of tetrahydrofuran, 15 parts of block copolymer, 12 parts of LiFSI, and 1.5 parts of fluorinated ethylene glycol dimethyl ether were added sequentially to a beaker. The mixture was stirred for 4-6 hours until a completely clear solution was formed. Then, 1.5 parts of polyethylene glycol diglycidyl ether were added and the mixture was stirred for 0.5 hours to obtain an ion gel phase change electrolyte. Among them, the cation of ionic liquid is n is 3; the anion is [NTf2]. - ; The block copolymer is P(IPOx) a -co-NPOx 1-a ) m -b-PEO k -bP(IPOx a -co-NPOx 1-a ) p , a=0, m=100, k=300, p=100.

[0058] The method for preparing the lithium battery provided in this comparative example is the same as that in Example 1.

[0059] Test case The performance of the ion gel phase change electrolytes of Examples 1-3 and Comparative Examples 1-3 was tested, and the results are shown in Table 1.

[0060] Phase transition temperature test: determined by measuring the electrolyte transmittance. The transmittance of the electrolyte is measured using a variable-temperature UV-Vis spectrometer. The electrolyte is placed on the instrument's heating stage and heated at a rate of 1°C / min. The transmittance curve is recorded, and the temperature at which the transmittance reaches 0 is defined as the phase transition temperature.

[0061] Ionic conductivity test: A 2cm² area... 2 Stainless steel gaskets and electrolytes are assembled into a battery. The battery is placed in a low-temperature test chamber at -20°C for 3 hours. An electrochemical workstation is connected, and a sinusoidal voltage signal with an amplitude of 20mV is applied. The frequency range of the test is between 4MHz and 100mHz. The resistance of the electrolyte is recorded, and the ionic conductivity is calculated.

[0062] Table 1

[0063] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. An ion-gel phase change electrolyte, characterized in that, Based on parts by mass, it includes the following components: The mixture contains 50-70 parts ionic liquid, 9-20 parts organic solvent, 10-20 parts block copolymer, 5-15 parts lithium salt, 0.5-4 parts additives, and 0.5-2 parts crosslinking agent. The general formula of the block copolymer is P(IPOx a -co-NPOx 1-a ) m -b-PEO k -b-P(IPOx a -co-NPOx 1-a ) p ; wherein, IPOx is isopropyl oxazoline, NPOx is n-propyl oxazoline; a is the mole fraction of IPOx, 0<a<1; m, p and k are degrees of polymerization, m and p are each independently an integer between 5 and 200, and k is an integer between 20 and 1000.

2. The ion-gel phase change electrolyte according to claim 1, characterized in that, The ionic liquid comprises anions and cations; the anions include F... - [BF4] - [PF6] - [NTf2] - and [FSI] - At least one of the following; the cation includes a cation having the structure shown in formula (I) and / or formula (II); (I); (II); where n is an integer between 1 and 5.

3. The ion-gel phase change electrolyte according to claim 1, characterized in that, The organic solvent includes at least one of tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, and ethylene glycol dimethyl ether.

4. The ion-gel phase change electrolyte according to claim 1, characterized in that, The lithium salt includes at least one of LiFSI, LiTFSI, LiDFOB, LiBOB, LiCF3SO3, LiPF6, and LiBF4.

5. The ion-gel phase change electrolyte according to claim 1, characterized in that, The crosslinking agent includes at least one of polyethylene glycol diglycidyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, triethylene glycol diacrylate, and diethylene glycol diacrylate.

6. The ion-gel phase change electrolyte according to claim 1, characterized in that, The additive includes at least one of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, fluoroethylene glycol dimethyl ether, and tris(trimethylsilyl)phosphate.

7. The method for preparing the ion-gel phase change electrolyte according to any one of claims 1 to 6, characterized in that, Includes the following steps: The ionic liquid, organic solvent, block copolymer, lithium salt and additives are mixed and then a crosslinking agent is added and mixed to obtain the ion gel phase change electrolyte.

8. A lithium battery, characterized in that, It includes a positive electrode, a negative electrode, and an ion gel phase change electrolyte as described in any one of claims 1 to 6.

9. The lithium battery according to claim 8, characterized in that, The positive electrode includes at least one of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, and ternary materials.

10. The lithium battery according to claim 8, characterized in that, The negative electrode includes at least one of natural graphite, artificial graphite, silicon, and metallic lithium.

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