A composite gel electrolyte and its preparation method and application

Abstract

The present invention discloses a method for preparing a composite gel electrolyte, as well as its preparation method and application. The method comprises the following steps: preparing a polymer solution: mixing a high molecular weight polymer matrix with an organic solvent, stirring and dissolving the mixture at room temperature to obtain a transparent and uniform polymer solution; preparing a composite gel film: adding a metal alkoxide additive to the polymer solution, stirring the mixture evenly, and then standing the mixture to solidify. After the solvent evaporates, a smooth and flexible polymer film is obtained, and the polymer film is then dried; and preparing a composite gel electrolyte: immersing the polymer film in an electrolyte solution, and obtaining a gel polymer electrolyte after the polymer film swells. The composite gel electrolyte prepared by this method can have excellent ionic conductivity, high energy density, and stability, good compatibility with the positive and negative electrodes of lithium batteries, and can exhibit excellent electrochemical performance when applied to lithium metal batteries.

Description

Technical Field

[0001] The present invention belongs to the field of lithium metal battery materials, and in particular relates to a composite gel electrolyte and a preparation method and application thereof. Background Art

[0002] Lithium metal batteries are expected to become the first choice for the next generation of power batteries due to their extremely high theoretical specific capacity and high energy density. However, the lithium metal negative electrode has high reactivity, and uncontrollable dendrite growth during charging and discharging can easily cause battery short circuits, posing a serious safety hazard. In addition, organic liquid electrolytes have low boiling points and flash points. When overcharged or subjected to external collisions, the battery is prone to thermal runaway, causing a series of safety accidents. Compared with organic liquid electrolytes, gel electrolytes can effectively control the flow of liquid solvents and avoid battery leakage problems. In addition, gel electrolytes improve the compatibility of the electrolyte with the lithium negative electrode interface, can inhibit the growth of lithium dendrites, and thus improve the performance of lithium batteries. Currently, the method to improve the mechanical strength and ion conductivity of gel electrolytes is to add inorganic solid fillers. However, inorganic solid fillers agglomerate, producing filler-free areas that are easily recrystallized, reducing the ionic conductivity and toughness of the electrolyte, thereby affecting the energy density and cycle stability of the electrolyte.

[0003] Currently, in order to achieve the commercial application of gel electrolyte systems in lithium batteries, researchers have improved their overall performance through various approaches such as polymer blending and electrolyte interface modification. However, while these methods improve safety and stability, they often sacrifice performance such as ionic conductivity and energy density. Therefore, in the commercialization process of lithium metal batteries, there is an urgent need to optimize polymer electrolytes and prepare gel electrolytes with high stability and excellent electrochemical performance. Summary of the Invention

[0004] The purpose of the present invention is to provide a composite gel electrolyte and its preparation method and application. The composite gel electrolyte prepared by this method can have excellent ionic conductivity, high energy density and stability, good compatibility with the positive and negative electrodes of lithium batteries, and can show excellent electrochemical performance when applied to lithium metal batteries.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a method for preparing a composite gel electrolyte, comprising the following steps:

[0006] (1) Preparation of polymer solution: a polymer matrix and an organic solvent were mixed and stirred at room temperature to dissolve to obtain a transparent and uniform polymer solution; the mass volume ratio of the polymer matrix to the organic solvent was 0.25 g:10 mL;

[0007] (2) Preparation of a composite gel film: adding a metal alkoxide additive to the polymer solution obtained in step (1) at a mass ratio of (0.005-0.01):1, stirring evenly and then standing to solidify, and obtaining a smooth and flexible polymer film after the solvent evaporates, and then drying the polymer film;

[0008] (3) Preparation of composite gel electrolyte: Soak the polymer film prepared in step (2) in an electrolyte for 1-2 hours, and obtain a composite gel electrolyte after the polymer film swells.

[0009] Preferably, in step (2), the metal alkoxide additive is one or more of tetramethyl silicate, tetraethyl silicate, tetrapropyl silicate, tetrabutyl silicate, tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, tetrabutyl titanate, tetraisopropyl titanate, tetrapropyl zirconate, tetrabutyl zirconate, and triisopropyl aluminate.

[0010] Preferably, in step (1), the high molecular polymer matrix is ​​one or more of polyethylene oxide, polypropylene carbonate, polyacrylonitrile, polyurethane, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, and polymethyl methacrylate.

[0011] Preferably, in step (1), the organic solvent is one or more of tetrahydrofuran, methanol, ethanol, ether, dichloromethane, chloroform, ethyl acetate, dimethyl sulfoxide, acetone, butanone, N-dimethylformamide, and N-dimethylacetamide.

[0012] Preferably, in step (3), the electrolyte comprises a lithium salt and an organic solvent.

[0013] Preferably, the organic solvent in the electrolyte is one or more of tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, diethylene glycol dimethyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol butyl ether, ethylene glycol dimethyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, and dimethoxypropane.

[0014] Preferably, the lithium salt in the electrolyte is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium trifluoromethylsulfonyl imide, lithium trifluorochloroborate, lithium bisfluorosulfonyl imide, lithium dioxalatoborate, lithium difluorooxalatoborate, and lithium tetracyanoborate.

[0015] Preferably, in step (3), the concentration of the lithium salt in the electrolyte is 0.8-1.5 mol / L.

[0016] The present invention also provides an application of the composite gel electrolyte prepared by the preparation method of the composite gel electrolyte in a lithium metal battery.

[0017] Preferably, the lithium metal battery includes a positive electrode, a negative electrode and a composite gel electrolyte composited between the positive electrode and the negative electrode; the positive electrode active material is one of a sulfur-carbon composite material and an iodine-carbon composite material, and the negative electrode active material is lithium metal or a lithium alloy.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] (1) The present invention introduces functionalized metal alkoxide additives into the polymer matrix and constructs a polyorganometallic oxane network through in situ polymerization, thereby significantly improving the ionic conductivity, cycle stability, and thermal stability of the electrolyte; the room temperature ionic conductivity of the composite gel electrolyte is 1.4×10 -3 ~1.7×10 -3 S / cm, heated at 200℃ for 1h, the composite gel electrolyte maintains excellent stability;

[0020] (2) The composite gel electrolyte of the present invention exhibits good interfacial stability and compatibility with lithium metal, which enables the lithium metal battery to have excellent cycle life and cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a physical picture of the composite gel electrolytes of Comparative Example 1, Comparative Example 2 and Example 1 after thermal stability testing;

[0022] Figure 2 is the cycle curve of the lithium-lithium symmetrical battery assembled in Comparative Example 1, Comparative Example 2 and Example 1;

[0023] Figure 3 These are the charge and discharge curves of lithium batteries assembled using the composite gel electrolyte prepared in Example 1; (a) assembled lithium iron phosphate battery, (b) assembled lithium sulfur battery, and (c) assembled lithium iodine battery. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] In the examples of the present invention, unless otherwise specified, the raw materials and reagents used are commercially available products with a purity of analytical grade or above.

[0026] Example 1

[0027] A method for preparing a composite gel electrolyte comprises the following steps:

[0028] (1) Preparation of polymer solution: 0.25 g of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) was mixed with 10 mL of butanone and stirred at room temperature until dissolved to obtain a transparent and uniform polymer solution with a mass of 8.15 g.

[0029] (2) Preparation of composite gel film: 0.084 g of tetraethyl titanate was added to the polymer solution obtained in step (1), with the mass ratio of the metal alkoxide additive to the polymer solution being 0.01:1, and the mixture was stirred for 12 h to obtain a uniform suspension. The suspension was poured into a polytetrafluoroethylene mold and allowed to stand for solidification. The suspension was placed in a fume hood for 6 h to allow the solvent to evaporate, thereby obtaining a smooth and flexible polymer film. The polymer film was dried in a vacuum oven at 60°C for 1 h.

[0030] (3) Preparation of a composite gel electrolyte: The polymer film prepared in step (2) is immersed in an electrolyte for 1 hour, and a composite gel electrolyte is obtained after the polymer film swells; the electrolyte is composed of lithium bis(fluorosulfonyl)imide, 1,3-dioxolane, and ethylene glycol dimethyl ether, and the concentration of lithium salt in the electrolyte is 1 mol / L.

[0031] Comparative Example 1

[0032] The commercial polyolefin separator is Celgard 2300.

[0033] Comparative Example 2

[0034] The difference from Example 1 is that tetraethyl titanate was not added in Comparative Example 2, and the other preparation processes were the same.

[0035] The commercial polyolefin separator of Comparative Example 1, the gel electrolyte prepared in Comparative Example 2 and Example 1 were placed at room temperature and 200°C, and the appearance of the electrolyte was recorded. Figure 1 As shown. Figure 1 It can be seen that the commercial polyolefin separator of Comparative Example 1 is severely curled and deformed at a high temperature of 200°C, the single-component gel electrolyte prepared in Comparative Example 2 undergoes thermal shrinkage at a high temperature of 200°C, and the composite gel electrolyte prepared in Example 1 maintains its original size at a high temperature of 200°C and maintains excellent stability.

[0036] Assembly of lithium-lithium symmetrical batteries: The assembly of the batteries needs to be carried out in a glove box filled with an argon protective atmosphere. The battery is assembled using a pair of metal lithium sheets as electrodes. The gel polymer electrolyte is cut into the size of a button battery separator. The cut composite gel electrolyte is used to replace the separator and electrolyte in the battery to assemble a solid-state lithium battery.

[0037] The electrochemical test of the lithium-lithium symmetrical battery of this embodiment was carried out on a LAND test system, with the test temperature maintained at 25°C and the current density at 1 mA / cm 2 , lithium deposition capacity is 1mAh / cm 2 The results are as follows Figure 2As shown, the lithium-lithium symmetric cells using the polyolefin separator of Comparative Example 1 and the single-component gel electrolyte of Comparative Example 2 experienced battery failure and short circuit after 75 and 110 hours of cycling, respectively. However, the time-voltage curve of the lithium-lithium symmetric cell assembled in Example 1 with the tetraethyl titanate additive remained stable after 400 hours of cycling. The composite gel electrolyte prepared in Example 1 exhibited a more stable voltage curve than those in Comparative Examples 1 and 2, demonstrating that the composite gel electrolyte prepared in this example, containing a metal alkoxide additive, can consistently improve the cycling stability and cycle life of the battery.

[0038] Assembly of stainless steel symmetrical cells: The cell assembly needs to be carried out in a glove box filled with an argon protective atmosphere. The cell is assembled using a pair of stainless steel sheets as electrodes. The gel polymer electrolyte is cut into the size of a button cell separator. The cut composite gel electrolyte is used to replace the separator and electrolyte in the cell to assemble a stainless steel symmetrical cell.

[0039] The electrochemical test of the stainless steel battery in this example was carried out on a CHI760E electrochemical workstation, and the test temperature was kept constant at 25°C. The room temperature ionic conductivity of the composite gel electrolyte was measured to be 1.7×10 -3 S / cm, it can be seen that the composite gel electrolyte containing metal alkoxide additives prepared in this embodiment has high ionic conductivity and can significantly improve the electrochemical performance and cycle performance of the battery.

[0040] Assembly of lithium batteries: The assembly of batteries needs to be carried out in a glove box filled with argon protective atmosphere. The lithium battery is assembled with metallic lithium sheets as the negative electrode, and lithium iron phosphate, sulfur, and iodine as the positive electrodes. The composite gel electrolyte is cut into the size of a button battery separator, and the cut composite gel electrolyte is used to assemble a solid-state lithium battery.

[0041] The electrochemical test of the lithium battery of this embodiment was carried out on the LAND test system, and the test temperature was kept constant at 25°C. Figure 3 As shown, the lithium iron phosphate battery using the composite gel electrolyte has a discharge specific capacity of 131 mAh / g at a 1C rate, the lithium sulfur battery using the composite gel electrolyte has a discharge specific capacity of 1180 mAh / g at a 0.5C rate, and the lithium iodine battery using the composite gel electrolyte has a discharge specific capacity of 175 mAh / g at a 1C rate. It can be seen that the composite gel electrolyte containing metal alkoxide additives prepared in this embodiment has good compatibility and adaptability with a variety of positive electrode materials (such as lithium iron phosphate positive electrode, sulfur positive electrode, iodine positive electrode), and the cycle stability of the lithium battery is good.

[0042] Example 2

[0043] A method for preparing a composite gel electrolyte comprises the following steps:

[0044] (1) Preparation of polymer solution: 0.25 g of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) was mixed with 10 mL of butanone and stirred at room temperature until dissolved to obtain a transparent and uniform polymer solution with a mass of 8.15 g.

[0045] (2) Preparation of composite gel film: 0.042 g of tetrabutyl zirconate was added to the polymer solution obtained in step (1), with the mass ratio of the metal alkoxide additive to the polymer solution being 0.005:1, and the mixture was stirred for 12 h to obtain a uniform suspension. The suspension was poured into a polytetrafluoroethylene mold and allowed to stand for solidification. The suspension was placed in a fume hood for 6 h to allow the solvent to evaporate, thereby obtaining a smooth and flexible polymer film. The polymer film was dried in a vacuum oven at 60°C for 1 h.

[0046] (3) Preparation of a composite gel electrolyte: The polymer film prepared in step (2) is immersed in an electrolyte for 2 hours, and a composite gel electrolyte is obtained after the polymer film swells; the electrolyte is composed of lithium bis(fluorosulfonyl)imide, 1,3-dioxolane, and ethylene glycol dimethyl ether, and the concentration of lithium salt in the electrolyte is 1.5 mol / L.

[0047] The assembly process of the lithium-lithium symmetrical battery, the assembly process of the stainless steel symmetrical battery, and the assembly process of the lithium battery are all referred to Example 1.

[0048] The electrochemical test of the lithium-lithium symmetrical battery of this embodiment was carried out on a LAND test system, with the test temperature maintained at 25°C and the current density at 1 mA / cm 2 , lithium deposition capacity is 1mAh / cm 2 The time-voltage curve of the lithium-lithium symmetrical battery assembled with tetrabutyl zirconate additive in this embodiment remains stable after 350 hours of cycling. The composite gel electrolyte prepared in this embodiment exhibits a more stable voltage curve than Comparative Examples 1 and 2, which shows that the composite gel electrolyte containing metal alkoxide additives prepared in this embodiment can stably improve the cycle stability and cycle life of the battery.

[0049] The electrochemical test of the stainless steel battery in this example was carried out on a CHI760E electrochemical workstation, and the test temperature was kept constant at 25°C. The room temperature ionic conductivity of the composite gel electrolyte was measured to be 1.5×10 -3 S / cm, it can be seen that the composite gel electrolyte containing metal alkoxide additives prepared in this embodiment has high ionic conductivity and can significantly improve the electrochemical performance and cycle performance of the battery.

[0050] The electrochemical tests of the lithium battery of this embodiment were conducted on a LAND test system, and the test temperature was maintained at a constant temperature of 25°C. The lithium iron phosphate battery using the composite gel electrolyte had a discharge capacity of 126 mAh / g at a 1C rate, the lithium sulfur battery using the composite gel electrolyte had a discharge capacity of 1096 mAh / g at a 0.5C rate, and the lithium iodine battery using the composite gel electrolyte had a discharge capacity of 172 mAh / g at a 1C rate. This shows that the composite gel electrolyte containing a metal alkoxide additive prepared in this embodiment has good compatibility and adaptability with a variety of positive electrode materials (such as lithium iron phosphate positive electrode, sulfur positive electrode, and iodine positive electrode), and the lithium battery has good cycle stability.

[0051] Example 3

[0052] A method for preparing a composite gel electrolyte comprises the following steps:

[0053] (1) Preparation of polymer solution: 0.25 g of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) was mixed with 10 mL of butanone and stirred at room temperature until dissolved to obtain a transparent and uniform polymer solution with a mass of 8.15 g.

[0054] (2) Preparation of composite gel film: 0.0625 g of tetraethyl silicate was added to the polymer solution obtained in step (1), with the mass ratio of the metal alkoxide additive to the polymer solution being 0.0076:1, and the mixture was stirred for 12 h to obtain a uniform suspension. The suspension was poured into a polytetrafluoroethylene mold and allowed to stand for solidification. The suspension was placed in a fume hood for 6 h to allow the solvent to evaporate, thereby obtaining a smooth and flexible polymer film. The polymer film was dried in a vacuum oven at 60°C for 1 h.

[0055] (3) Preparation of a composite gel electrolyte: The polymer film prepared in step (2) is immersed in an electrolyte for 1.5 hours, and a composite gel electrolyte is obtained after the polymer film swells; the electrolyte is composed of lithium hexafluorophosphate, 1,4-dioxane, and diethylene glycol dimethyl ether, and the concentration of lithium salt in the electrolyte is 0.8 mol / L.

[0056] The assembly process of the lithium-lithium symmetrical battery, the assembly process of the stainless steel symmetrical battery, and the assembly process of the lithium battery are all referred to Example 1.

[0057] The electrochemical test of the lithium-lithium symmetrical battery of this embodiment was carried out on a LAND test system, with the test temperature maintained at 25°C and the current density at 1 mA / cm 2 , lithium deposition capacity is 1mAh / cm 2The time-voltage curve of the lithium-lithium symmetrical battery assembled with tetraethyl silicate additive in this embodiment remains stable after 400 hours of cycling. The composite gel electrolyte prepared in this embodiment exhibits a more stable voltage curve than Comparative Examples 1 and 2, which shows that the composite gel electrolyte containing metal alkoxide additives prepared in this embodiment can stably improve the cycle stability and cycle life of the battery.

[0058] The electrochemical test of the stainless steel battery in this example was carried out on a CHI760E electrochemical workstation, and the test temperature was kept constant at 25°C. The room temperature ionic conductivity of the composite gel electrolyte was measured to be 1.46×10 -3 S / cm, it can be seen that the composite gel electrolyte containing metal alkoxide additives prepared in this embodiment has high ionic conductivity and can significantly improve the electrochemical performance and cycle performance of the battery.

[0059] The electrochemical tests of the lithium battery of this embodiment were conducted on a LAND test system, with the test temperature maintained at a constant temperature of 25°C. The lithium iron phosphate battery using the composite gel electrolyte had a discharge capacity of 122 mAh / g at a 1C rate, the lithium sulfur battery using the composite gel electrolyte had a discharge capacity of 1022 mAh / g at a 0.5C rate, and the lithium iodine battery using the composite gel electrolyte had a discharge capacity of 170 mAh / g at a 1C rate. This shows that the composite gel electrolyte containing a metal alkoxide additive prepared in this embodiment has good compatibility and adaptability with a variety of positive electrode materials (such as lithium iron phosphate positive electrode, sulfur positive electrode, and iodine positive electrode), and the lithium battery has good cycle stability.

[0060] Example 4

[0061] A method for preparing a composite gel electrolyte comprises the following steps:

[0062] (1) Preparation of polymer solution: 0.25 g of polyethylene oxide pyrrole (PEO) was mixed with 10 mL of NN dimethylformamide and stirred at room temperature until dissolved to obtain a transparent and uniform polymer solution with a mass of 9.74 g.

[0063] (2) Preparation of composite gel film: 0.074 g of tetraethyl silicate was added to the polymer solution obtained in step (1), with the mass ratio of the metal alkoxide additive to the polymer solution being 0.0076:1, and the mixture was stirred for 12 h to obtain a uniform suspension. The suspension was poured into a polytetrafluoroethylene mold and allowed to stand for solidification. The suspension was placed in a fume hood for 6 h to allow the solvent to evaporate, thereby obtaining a smooth and flexible polymer film. The polymer film was dried in a vacuum oven at 60° C. for 1 h.

[0064] (3) Preparation of a composite gel electrolyte: The polymer film prepared in step (2) is immersed in an electrolyte for 2 hours, and a composite gel electrolyte is obtained after the polymer film swells; the electrolyte is composed of lithium hexafluorophosphate, 1,3-dioxolane, and ethylene glycol dimethyl ether, and the concentration of lithium salt in the electrolyte is 1.5 mol / L.

[0065] The assembly process of the lithium-lithium symmetrical battery, the assembly process of the stainless steel symmetrical battery, and the assembly process of the lithium battery are all referred to Example 1.

[0066] The electrochemical test of the lithium-lithium symmetrical battery of this embodiment was carried out on a LAND test system, with the test temperature maintained at 25°C and the current density at 1 mA / cm 2 , lithium deposition capacity is 1mAh / cm 2 The time-voltage curve of the lithium-lithium symmetrical battery assembled with tetraethyl silicate additive in this embodiment remained stable after 320 hours of cycling. The composite gel electrolyte prepared in this embodiment showed a more stable voltage curve compared with Comparative Examples 1 and 2. This shows that the composite gel electrolyte containing metal alkoxide additives prepared in this embodiment can stably improve the cycle stability and cycle life of the battery.

[0067] The electrochemical test of the stainless steel battery in this example was carried out on a CHI760E electrochemical workstation, and the test temperature was kept constant at 25°C. The room temperature ionic conductivity of the composite gel electrolyte was measured to be 1.6×10 -3 S / cm, it can be seen that the composite gel electrolyte containing metal alkoxide additives prepared in this embodiment has high ionic conductivity and can significantly improve the electrochemical performance and cycle performance of the battery.

[0068] The electrochemical tests of the lithium battery of this embodiment were conducted on a LAND test system, and the test temperature was maintained at a constant temperature of 25°C. The lithium iron phosphate battery using the composite gel electrolyte had a discharge capacity of 125 mAh / g at a 1C rate, the lithium sulfur battery using the composite gel electrolyte had a discharge capacity of 990 mAh / g at a 0.5C rate, and the lithium iodine battery using the composite gel electrolyte had a discharge capacity of 185 mAh / g at a 1C rate. This shows that the composite gel electrolyte containing a metal alkoxide additive prepared in this embodiment has good compatibility and adaptability with a variety of positive electrode materials (such as lithium iron phosphate positive electrode, sulfur positive electrode, and iodine positive electrode), and the lithium battery has good cycle stability.

Claims

1. A method for preparing a composite gel electrolyte, characterized in that: The following steps are involved: (1) Preparation of polymer solution: a polymer matrix and an organic solvent were mixed and stirred at room temperature to dissolve to obtain a transparent and uniform polymer solution; the mass volume ratio of the polymer matrix to the organic solvent was 0.25 g:10 mL; (2) Preparation of a composite gel film: adding a metal alkoxide additive to the polymer solution obtained in step (1) at a mass ratio of (0.005-0.01):1, stirring evenly and then standing to solidify, and obtaining a smooth and flexible polymer film after the solvent evaporates, and then drying the polymer film; (3) Preparation of composite gel electrolyte: Soak the polymer film prepared in step (2) in an electrolyte for 1-2 hours, and obtain a composite gel electrolyte after the polymer film swells.

2. The method for preparing a composite gel electrolyte according to claim 1, wherein: In step (2), the metal alkoxide additive is one or more of tetramethyl silicate, tetraethyl silicate, tetrapropyl silicate, tetrabutyl silicate, tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, tetrabutyl titanate, tetraisopropyl titanate, tetrapropyl zirconate, tetrabutyl zirconate, and triisopropyl aluminate.

3. The method for preparing a composite gel electrolyte according to claim 1 or 2, wherein: In step (1), the high molecular polymer matrix is ​​one or more of polyethylene oxide, polypropylene carbonate, polyacrylonitrile, polyurethane, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, and polymethyl methacrylate.

4. The method for preparing a composite gel electrolyte according to claim 1 or 2, wherein: In step (1), the organic solvent is one or more of tetrahydrofuran, methanol, ethanol, ether, dichloromethane, chloroform, ethyl acetate, dimethyl sulfoxide, acetone, butanone, N-dimethylformamide, and N-dimethylacetamide.

5. The method for preparing a composite gel electrolyte according to claim 1 or 2, characterized in that: In step (3), the electrolyte includes a lithium salt and an organic solvent.

6. The method for preparing a composite gel electrolyte according to claim 5, characterized in that: The organic solvent in the electrolyte is one or more of tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, diethylene glycol dimethyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol butyl ether, ethylene glycol dimethyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, and dimethoxypropane.

7. The method for preparing a composite gel electrolyte according to claim 5, characterized in that: The lithium salt in the electrolyte is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium trifluoromethylsulfonyl imide, lithium trifluorochloroborate, lithium bisfluorosulfonyl imide, lithium dioxalatoborate, lithium difluorooxalatoborate, and lithium tetracyanoborate.

8. The method for preparing a composite gel electrolyte according to claim 5, characterized in that: In step (3), the concentration of the lithium salt in the electrolyte is 0.8-1.5 mol / L.

9. Use of the composite gel electrolyte prepared by the method for preparing the composite gel electrolyte according to any one of claims 1 to 8 in a lithium metal battery.

10. Use of the composite gel electrolyte in a lithium metal battery according to claim 9, characterized in that: The lithium metal battery includes a positive electrode, a negative electrode and a composite gel electrolyte composited between the positive electrode and the negative electrode; the positive electrode active material is one of a sulfur-carbon composite material and an iodine-carbon composite material, and the negative electrode active material is lithium metal or a lithium alloy.

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