A gel polymer electrolyte precursor, a gel polymer electrolyte, and a battery and a method for manufacturing the same

Abstract

The application discloses a gel polymer electrolyte precursor, a gel polymer electrolyte, and a battery and a preparation method thereof, and aims to provide a gel polymer electrolyte precursor and a gel polymer electrolyte which have excellent flame retardant performance, improve battery safety, avoid the negative influence of flame retardant components on the electrochemical performance of the battery, guarantee the good cycle life of the battery, and have excellent safety performance and electrochemical cycle stability, and can meet the use requirements of high specific energy and large capacity battery cells; the gel polymer electrolyte precursor comprises a first monomer, a second monomer, a third monomer, an initiator, a lithium salt, an organic solvent and an electrolyte additive; after the components are mixed, in-situ solidification molding is performed to obtain the gel polymer electrolyte; the gel polymer electrolyte is filled into a bare battery to obtain a gel polymer battery; and the application belongs to the technical field of batteries.

Description

Technical Field

[0001] This invention relates to lithium-ion battery technology, and more particularly to a gel polymer electrolyte precursor, a gel polymer electrolyte, a battery, and a method for preparing the same. Background Technology

[0002] Semi-solid batteries generally refer to lithium-ion batteries assembled from gel polymer electrolytes. Unlike traditional liquid lithium-ion batteries that use liquid electrolytes and rely on porous membranes for positive and negative electrode isolation, and unlike all-solid batteries that use solid electrolytes entirely, semi-solid batteries combine the advantages of both: on the one hand, gel polymer electrolytes have good flexibility and interfacial compatibility, which can adapt to the volume changes of electrode materials during charging and discharging. At the same time, the gel structure formed by in-situ polymerization can effectively fix the liquid electrolyte, reduce the risk of liquid electrolyte leakage, and improve the overall safety performance of the battery; on the other hand, semi-solid batteries retain a certain proportion of liquid components as lithium-ion transport media. Compared with all-solid batteries, they can achieve higher room temperature ionic conductivity, reduce interfacial impedance, and are more compatible with existing lithium-ion battery production processes. They do not require large-scale modification of existing production lines and have high potential for industrial application.

[0003] Currently, the mainstream approach for semi-solid batteries is based on in-situ solidification technology using gel electrolytes. This technology is compatible with existing processes, retaining high ionic conductivity and solving electrode interface contact problems. It also reduces the fluidity of flammable components, increases the flash point, and enhances internal short-circuit tolerance through polymer networks. However, due to the presence of flammable components, it still cannot meet the safety challenges of high specific energy and large capacity cells.

[0004] To address this, improving the flame retardancy of the electrolyte by adding flame retardants is a current approach to enhancing the safety performance of gel electrolytes. For example, the scheme disclosed in CN202010156622.9 involves blending fluorinated organic reagents with lithium salts, crosslinking agents, etc., and then polymerizing them in situ to form a semi-interpenetrating network flame-retardant gel electrolyte. Fluorine is used to improve thermal and electrochemical stability and safety. However, this type of method introduces flame retardant substances in the form of solvents or additives, which can easily reduce ionic conductivity, increase internal resistance, affect lithium salt dissociation, and hinder the formation of the negative electrode SEI layer, thus reducing battery cycle stability.

[0005] For example, patent CN202111632648.7 discloses a method of homopolymerizing or copolymerizing monomers with gas-phase flame-retardant function to form a gel polymer electrolyte matrix. At high temperature, its condensation reaction produces non-flammable or flame-retardant volatiles, and the endothermic reaction and cross-linking network can insulate against heat and oxygen, and synergistically retard flame. This method mainly uses unsaturated alkane phosphate esters, which has high requirements for the design of the polymerization inhibitor molecules, low flame-retardant efficiency, and limited improvement on battery safety performance.

[0006] Introducing the aforementioned fluorinated organic solvents and monomers with gas-phase flame retardant properties into lithium-ion electrolytes may improve battery safety to some extent, but it can also have a significant negative impact on battery cycle life.

[0007] Therefore, developing a gel polymer electrolyte that can effectively improve the safety performance of the gel polymer electrolyte without affecting the electrochemical cycle performance of the battery has become an urgent problem to be solved in this field. Summary of the Invention

[0008] To address the aforementioned shortcomings, the first objective of this invention is to provide a gel polymer electrolyte precursor and a gel polymer electrolyte that possess excellent flame retardant properties, enhance battery safety, avoid the negative impact of flame retardant components on battery electrochemical performance, and ensure good battery cycle life.

[0009] The second objective of this invention is to provide a method for preparing the gel polymer electrolyte, which is simple in process, compatible with existing lithium battery production lines, does not require large-scale modification of existing production equipment, and has low industrial production costs.

[0010] A third objective of this invention is to provide a gel polymer battery containing the gel polymer electrolyte, which has excellent safety performance and electrochemical cycle stability, and can meet the requirements for the use of high-energy-density, high-capacity battery cells.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] Therefore, the first technical solution provided by this invention is as follows:

[0013] A gel polymer electrolyte precursor, made from the following raw materials in parts by weight:

[0014] First monomer: 1-8 parts;

[0015] Second monomer: 0.5-5 parts;

[0016] Third monomer: 0.1-6 parts;

[0017] Initiator: 0.01-1 part;

[0018] Lithium salt: 5-25 parts;

[0019] Organic solvent: 50-90 parts;

[0020] Electrolyte additive: 0-10 parts;

[0021] The first monomer is selected from at least one of divinylbenzene, divinyltoluene, divinylnaphthalene, trivinylbenzene, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, N,N'-methylenebisacrylamide, N,N'-divinylethylenediamine, diallyl phthalate, diallyl maleate, and their derivatives.

[0022] The second monomer is selected from at least one of pentaerythritol tetraacrylate ethoxylate, pentaerythritol tetraacrylate propoxylate, bis(trimethylolpropane)tetraacrylate, pentaerythritol triacrylate, trimethylolpropane trimethacrylate, propoxylated glycerol triacrylate, tri(2-hydroxyethyl)isocyanurate triacrylate, trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, and poss-octaacrylate.

[0023] The third monomer is a halogenated acrylate derivative.

[0024] Furthermore, in the aforementioned gel polymer electrolyte precursor, the third monomer is selected from 2-(perfluorooctyl)ethyl methacrylate, perfluoroalkyl ethyl methacrylate, 2-chloroethyl methacrylate, 6-bromohexyl acrylate, 2-bromoethyl methacrylate, 2,4,6-tribromophenyl acrylate, 2,4,6-tribromophenyl methacrylate, pentabromobenzyl acrylate, 3,3,4,4,5,5,6,6,7,7,8,8,8-tetrafluorooctyl acrylate, 2,2,3,3,4,4,4-heptafluorobutyl acrylate, pentabromophenyl methacrylate, and pentabromobenzyl methacrylate. At least one of the following: 2-chloroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 1H,1H-perfluoron-octyl acrylate, 2,3-dibromopropyl acrylate, 1H,1H,11H-perfluoroundecyl methacrylate, 2,2,3,3,4,4,4-heptafluorobutyl methacrylate, 2-methyl-2-(trifluoromethylsulfonamide)propyl methacrylate, 1H,1H,5H-octafluoropentyl acrylate, 3-perfluorohexyl-2-hydroxypropyl acrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, pentafluorophenol acrylate, and hexafluorobutyl methacrylate.

[0025] In this application, the first type of monomer serves as one of the polymer backbones, exhibiting excellent polymerization performance, effectively constructing the polymer network, and providing abundant grafting and crosslinking sites, thus paving the way for the subsequent introduction of functional polymer monomers. The second type of monomer, also serving as the polymer backbone, further enhances the polymerization effect while improving the polymer network structure, forming a richer three-dimensional structure, improving the migration path and coordination structure of lithium ions, and effectively enhancing the migration efficiency of lithium ions. The third type of monomer, serving as a functional monomer, provides flame retardancy and high safety while participating in the formation of positive and negative electrode films, forming an electrolyte film rich in LiBr and LiF inorganic components, thereby improving the cycle performance of the battery under a 4.5V high voltage.

[0026] Furthermore, in the aforementioned gel polymer electrolyte precursor, the initiator is at least one selected from benzoyl peroxide, dicyclohexyl peroxide, tert-butyl peroxide-2-ethylhexanoate, azobisisoheptanenitrile, and azobisisobutyronitrile.

[0027] Furthermore, in the aforementioned gel polymer electrolyte precursor, the organic solvent includes at least one of linear carboxylic acid esters, cyclic carbonates, fluorinated linear carboxylic acid esters, and fluorinated cyclic carbonates.

[0028] Furthermore, in the aforementioned gel polymer electrolyte precursor, the electrolyte additive includes at least one of vinylene carbonate, fluoroethylene carbonate, and vinyl sulfate.

[0029] Furthermore, in the aforementioned gel polymer electrolyte precursor, the lithium salt includes at least one of LiPF6, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium bis(oxalate)borate, LiBF4, and LiClO4.

[0030] The second technical solution provided by this invention is as follows:

[0031] A gel polymer electrolyte is obtained by in-situ polymerization of the gel polymer electrolyte precursor described in the first technical solution.

[0032] The third technical solution provided by this invention is as follows:

[0033] A gel polymer battery includes a bare battery filled with a gel polymer electrolyte as described in the third technical solution.

[0034] The fourth technical solution provided by this invention is as follows:

[0035] A method for preparing a gel polymer battery includes the following steps:

[0036] 1) Weigh each raw material and mix the first monomer, second monomer, third monomer, initiator, lithium salt, organic solvent and electrolyte additive evenly under environmental conditions where the moisture and oxygen content are both less than or equal to 0.01 ppm to obtain the gel polymer electrolyte precursor.

[0037] 2) The gel polymer electrolyte precursor is injected into the assembled bare battery, and after being left to stand and encapsulated, an in-situ polymerization reaction is initiated by heating to obtain a gel cell.

[0038] 3) The gel cell prepared in step 2) is placed under a pressure of 2-100 psi, and then pre-charged, formed, and capacity tested to obtain a gel polymer battery.

[0039] Furthermore, in the above-mentioned method for preparing a gel polymer battery, the in-situ polymerization reaction in step 1) is carried out at a pressure of 2-100 psi and a temperature of 40-80°C for 12-96 h; the standing time in step 2) is 12-48 h at room temperature.

[0040] Compared with the prior art, the technical solution provided by the present invention has the following technical advantages:

[0041] 1. The gel polymer electrolyte provided by this invention constructs a gel polymer network framework through the synergistic construction of three different functional monomers. The first and second monomers can be efficiently cross-linked to construct a stable three-dimensional network structure. The third monomer contains high-nitrogen and halogen functional monomers, which can be grafted onto the polymer framework to exert a gas-phase flame retardant effect, improving the overall thermal stability and safety of the cell. On the other hand, it can participate in the formation of the positive and negative electrode interface film, generating a stable SEI film rich in LiF and lithium halide inorganic components at the interface. This not only inhibits the occurrence of side reactions but also avoids the damage of free flame retardant components to the electrochemical performance of the battery, thus balancing the cell's safety performance and cycle stability. It solves the problem of low flame retardant efficiency of polymeric flame retardant electrolytes and avoids the problem of additive flame retardant electrolytes affecting ionic conductivity and SEI film production.

[0042] 2. The present invention utilizes three types of monomer polymerization and, based on the multi-substitution characteristics of single-molecule structures, constructs a highly cross-linked interpenetrating polymer network. This results in a highly cross-linked polymer structure that effectively enhances the Young's modulus and strength of the gel polymer electrolyte. The gel polymer segments effectively limit the excessive decomposition of organic solvents on the positive and negative electrode sides of the battery, significantly improving the battery's cycle stability. This, in turn, improves the cycle stability and resistance to lithium dendrite formation in lithium-ion batteries.

[0043] 3. The gel polymer battery prepared by the technical solution provided by the present invention has both excellent flame retardant safety and good electrochemical cycle stability, which can meet the application requirements of high specific energy and large capacity battery cells.

[0044] 4. The gel polymer electrolyte preparation method provided by the present invention can be directly adapted to the existing lithium battery production process without the need for large-scale modification of existing equipment, resulting in low production costs and easy industrialization. Attached Figure Description

[0045] Figure 1 These are the electrochemical window curves of Example 21 and Comparative Examples 1 and 2 of the present invention;

[0046] Figure 2 These are the cycling curves at 4.4V for the batteries prepared in Example 21 of this invention and Comparative Examples 1 and 2.

[0047] Figure 3 These are the cycling curves at 4.5V for the batteries prepared in Example 21 of this invention and Comparative Examples 1 and 2.

[0048] Figure 4 This is the voltage-temperature curve of needle penetration under a full charge condition of 4.5V in Embodiment 21 of the present invention;

[0049] Figure 5 This is the voltage-temperature curve of Comparative Example 1 of the present invention under a full charge condition of 4.5V, obtained by needle penetration.

[0050] Figure 6 This is the voltage-temperature curve of Comparative Example 2 of the present invention under a full charge condition of 4.5V, obtained by needle penetration. Detailed Implementation

[0051] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions of embodiments are for the purpose of helping to understand the present invention, but do not constitute a limitation thereof.

[0052] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments can be purchased through conventional commercial channels unless otherwise specified.

[0053] Example 1

[0054] This embodiment provides a gel polymer electrolyte precursor. Under environmental conditions where the moisture and oxygen content are both ≤0.01ppm, 0.106g of the first monomer N,N'-methylenebisacrylamide, 0.053g of the second monomer bis(trimethylolpropane)tetraacrylate, 0.053g of the third monomer 2,4,6-tribromophenylacrylate, 0.02g of azobisisobutyronitrile, 0.84g of lithium hexafluorophosphate, 0.05g of lithium difluorooxalate borate, and 5.2g of mixed solvent are mixed evenly to obtain the gel polymer electrolyte precursor.

[0055] The mixed solvent is composed of fluoroethylene carbonate (FEC) and ethyl methyl carbonate (EMC) in a mass ratio of 2:8.

[0056] Example 2

[0057] This embodiment provides a gel polymer electrolyte precursor. Under environmental conditions where the moisture and oxygen content are both ≤0.01ppm, 0.8g of the first monomer ethylene glycol diacrylate, 0.5g of the second monomer pentaerythritol tetraacrylate, 0.6g of the third monomer 2-(perfluorooctyl)ethyl methacrylate, 0.1g of benzoyl peroxide, 2.5g of lithium bis(trifluoromethanesulfonyl)imide, 0.1g of vinylene carbonate, and 9.0g of mixed solvent are mixed evenly to obtain the gel polymer electrolyte precursor.

[0058] The mixed solvent consists of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a mass ratio of 3:7.

[0059] Example 3

[0060] This embodiment provides a gel polymer electrolyte precursor, which is prepared by uniformly mixing 0.1g of the first monomer divinylbenzene, 0.05g of the second monomer trimethylolpropane triacrylate, 0.01g of the third monomer 2-chloroethyl acrylate, 0.001g of azobisisoheptanenitrile, 0.5g of lithium bis(fluorosulfonyl)imide, 1.0g of vinyl sulfate, and 5.0g of mixed solvent under environmental conditions where the moisture and oxygen content are both ≤0.01ppm.

[0061] The mixed solvent consists of fluoroethylene carbonate (FEC) and diethyl carbonate (DEC) in a mass ratio of 1:9.

[0062] Example 4

[0063] This embodiment provides a gel polymer electrolyte precursor. Under environmental conditions where the moisture and oxygen content are both ≤0.01ppm, 0.2g of the first monomer divinylbenzene, 0.2g of N,N'-methylenebisacrylamide, 0.25g of the second monomer pentaerythritol triacrylate, 0.3g of the third monomer perfluoroalkyl ethyl methacrylate, 0.05g of tert-butyl peroxide-2-ethylhexanoate, 1.5g of LiBF4, 0.5g of fluoroethylene carbonate, and 7.0g of mixed solvent are mixed evenly to obtain the gel polymer electrolyte precursor.

[0064] The mixed solvent consists of fluorinated ethylene carbonate (FEC) and ethyl methyl carbonate (EMC) in a mass ratio of 4:6.

[0065] Example 5

[0066] This embodiment provides a gel polymer electrolyte precursor. Under environmental conditions where the moisture and oxygen content are both ≤0.01ppm, 0.2g of the first monomer 1,6-hexanediol diacrylate, 0.1g of the second monomer dipentaerythritol hexaacrylate, 0.6g of the third monomer 3,3,4,4,5,5,6,6,7,7,8,8,8-tetrafluorooctyl acrylate, 0.08g of dicyclohexyl peroxide dicarbonate, 1.0g of lithium bis(oxalate)borate, 0.4g of vinylene carbonate, 0.4g of vinyl sulfate, and 8.0g of mixed solvent are mixed evenly to obtain the gel polymer electrolyte precursor.

[0067] The mixed solvent consists of propylene carbonate (PC) and ethyl methyl carbonate (EMC) in a mass ratio of 5:5.

[0068] Example 6

[0069] This embodiment provides a gel polymer electrolyte precursor. Under environmental conditions where the moisture and oxygen content are both ≤0.01ppm, 0.05g of the first monomer trivinylbenzene, 0.025g of the second monomer poss-octaacrylate, 0.005g of the third monomer 2-bromoethyl methacrylate, 0.005g of azobisisobutyronitrile, 1.25g of LiClO4, 0.05g of fluoroethylene carbonate, 0.3g of vinylene carbonate, and 8.5g of mixed solvent are mixed evenly to obtain the gel polymer electrolyte precursor.

[0070] The mixed solvent consists of fluoroethylene carbonate (FEC), ethylene carbonate (EC), and dimethyl carbonate (DMC) in a mass ratio of 2:3:5.

[0071] Example 7

[0072] This embodiment provides a gel polymer electrolyte precursor. Under environmental conditions where the moisture and oxygen content are both ≤0.01ppm, 0.3g of the first monomer diethylene glycol dimethacrylate, 0.15g of the second monomer propoxyglycerol triacrylate, 0.2g of the third monomer 2,2,3,3,4,4,4-heptafluorobutyl acrylate, 0.03g of azobisisobutyronitrile, 1.0g of LiPF6, and 6.5g of mixed solvent are mixed evenly to obtain the gel polymer electrolyte precursor.

[0073] The mixed solvent consists of fluoroethylene carbonate (FEC) and ethyl methyl carbonate (EMC) in a mass ratio of 2:8.

[0074] Example 8

[0075] This embodiment provides a gel polymer electrolyte precursor. Under environmental conditions where the moisture and oxygen content are both ≤0.01ppm, 0.5g of the first monomer N,N'-divinylethylenediamine, 0.3g of the second monomer tris(2-hydroxyethyl)isocyanurate triacrylate, 0.4g of the third monomer pentabromobenzyl acrylate, 0.02g of benzoyl peroxide, 0.02g of azobisisobutyronitrile, 1.8g of lithium bis(pentafluoroethylsulfonyl)imide, 1.0g of fluoroethylene carbonate, and 5.5g of mixed solvent are mixed evenly to obtain the gel polymer electrolyte precursor.

[0076] The mixed solvent consists of ethylene carbonate (EC), fluoroethylene carbonate (FEC), and diethyl carbonate (DEC) in a mass ratio of 1:4:5.

[0077] Example 9

[0078] The only difference between this embodiment and Example 1 is that the amount of the third monomer 2-(perfluorooctyl)ethyl methacrylate added is 0.106g, while all other conditions remain the same as in Example 1.

[0079] Example 10

[0080] The difference between this embodiment and Example 1 is that the amount of the third monomer 2-(perfluorooctyl)ethyl methacrylate added is 0.159g, while all other conditions are the same as in Example 1.

[0081] Example 11

[0082] Example 11 provides a gel polymer electrolyte, which is obtained by in-situ polymerization of the gel polymer electrolyte precursor prepared in Example 1. Specifically, the gel polymer electrolyte precursor is placed at room temperature for 24 hours, then placed under 10 psi pressure and 45°C for 48 hours to allow the electrolyte precursor to fully solidify. After solidification and cooling, the gel polymer electrolyte is obtained.

[0083] Examples 12-20

[0084] Examples 12-20 provide a gel polymer electrolyte, which is obtained by in-situ polymerization of any gel polymer electrolyte precursor prepared in Examples 2-10. The corresponding relationship is shown in Table 1.

[0085] Table 1

[0086] Example The gel polymer electrolyte precursor used Example 12 Gel polymer electrolyte precursor prepared in Example 2 Example 13 Gel polymer electrolyte precursor prepared in Example 3 Example 14 Gel polymer electrolyte precursor prepared in Example 4 Example 15 Gel polymer electrolyte precursor prepared in Example 5 Example 16 Gel polymer electrolyte precursor prepared in Example 6 Example 17 Gel polymer electrolyte precursor prepared in Example 7 Example 18 Gel polymer electrolyte precursor prepared in Example 8 Example 19 Gel polymer electrolyte precursor prepared in Example 9 Example 20 Gel polymer electrolyte precursor prepared in Example 10

[0087] Example 21

[0088] This embodiment provides a gel polymer battery, which is prepared by the following steps: the gel polymer electrolyte prepared in Example 11 is added into the dry cell of a 1Ah lithium cobalt oxide / graphite soft-pack bare battery, and after rapid encapsulation, it is placed at room temperature for 24 hours. Then, the cell is placed in an environment of 10psi pressure and 45°C for 48 hours to allow the electrolyte precursor to fully solidify. After the solidified cell cools down, the gel polymer battery is obtained.

[0089] Examples 22-30

[0090] Examples 22-30: Preparation of Gel Polymer Batteries. The gel polymer electrolyte prepared in any of Examples 12-20 was injected into a 1Ah lithium cobalt oxide / graphite soft-pack bare battery cell. After rapid encapsulation, the cell was first left to stand at room temperature for 12-48 hours. Subsequently, the cell was placed in an environment with a pressure of 2-100 psi and a temperature of 40-80°C and left to stand for 12-96 hours to allow the electrolyte precursor to fully solidify. After the cell cooled to room temperature, the target gel polymer battery was obtained. The correspondence between the examples is detailed in Table 2.

[0091] Table 2

[0092] Example The gel polymer electrolyte used Place (h) Pressure (psi) Temperature (°C) Settling time (h) Example 22 Gel polymer electrolyte prepared in Example 12 12 100 40 96 Example 23 Gel polymer electrolyte prepared in Example 13 20 88 50 84 Example 24 Gel polymer electrolyte prepared in Example 14 24 70 70 72 Example 25 Gel polymer electrolyte prepared in Example 15 36 60 80 60 Example 26 Gel polymer electrolyte prepared in Example 16 24 50 50 48 Example 27 Gel polymer electrolyte prepared in Example 17 40 10 50 36 Example 28 Gel polymer electrolyte prepared in Example 18 48 2 40 24 Example 29 Gel polymer electrolyte prepared in Example 19 24 10 45 48 Example 30 Gel polymer electrolyte prepared in Example 20 24 10 45 48

[0093] Comparative Example 1

[0094] Under environmental conditions where both moisture and oxygen content are ≤0.01ppm, 0.84g of lithium hexafluorophosphate, 0.05g of lithium difluorooxalate borate, and 5.2g of a mixed solvent consisting of fluoroethylene carbonate (FEC) and ethyl methyl carbonate (EMC) in a mass ratio of 2:8 (2:8 mass ratio) were mixed evenly to obtain a liquid electrolyte.

[0095] The liquid electrolyte prepared in Comparative Example 1 was added into the dry cell of a 1Ah lithium cobalt oxide / graphite soft-pack bare battery. After rapid encapsulation, the cell was placed at room temperature for 24 hours, and then placed under 10psi pressure and 30℃ temperature for 48 hours to obtain the battery.

[0096] Comparative Example 2

[0097] The difference between Comparative Example 1 and Example 1 is that Comparative Example 2 only added the first monomer and the second monomer, without adding the third monomer, while the other conditions remained the same as in Example 1.

[0098] The gel polymer electrolyte prepared in Comparative Example 2 was added into the dry cell of a 1Ah lithium cobalt oxide / graphite soft-pack bare battery. After rapid encapsulation, the cell was placed at room temperature for 24 hours. Then, the cell was placed under 10psi pressure and 45℃ temperature for 48 hours to allow the electrolyte precursor to fully solidify. After the solidified cell cooled, the gel polymer battery was obtained.

[0099] To demonstrate the performance of the technical solution provided in this application, performance tests and data are presented below.

[0100] 1. Electrochemical stability window test

[0101] The electrochemical stability window of the three-electrode beaker cells (Li / / Li / / Pt) assembled in Example 21, Comparative Examples 1 and 2 was tested, and the test results are as follows: Figure 1 As shown. From Figure 1 It can be seen that the electrochemical stability window of the gel polymer electrolyte in Example 21 reached 6V, which is significantly better than 5.6V in Comparative Example 1 and 5.78V in Comparative Example 2.

[0102] 2. Cyclic life test

[0103] The batteries prepared in Example 21, Comparative Examples 1 and 2 were subjected to cyclic testing under constant current and constant voltage charging (500mA) and constant current discharging (500mA) conditions at 2.5-4.5V. The test results are as follows. Figure 2 As shown.

[0104] Table 3

[0105] 100-cycle capacity retention 200-cycle capacity retention 300-cycle capacity retention Example 21 97.43% 89.72 80.97% Example 29 96.59% 88.65% 78.64% Example 30 95.54% 85.34% 74.56% Comparative Example 1 96.98% 76.03% 0% Comparative Example 2 96.58% 0% 0%

[0106] from Figure 2 , Figure 3 It can be seen that the gel polymer battery prepared in Example 21 has more stable cycle life at a charging cutoff voltage of 4.5V; while under the same test conditions, the cycle life of the batteries prepared in Comparative Examples 1 and 2 is significantly lower than that of Example 21. This indicates that in the 4.5V-level lithium graphite cobalt oxide system, the liquid electrolyte undergoes severe side reactions, causing a rapid decline in cycle performance, while the gel polymer electrolyte can effectively suppress the effects of the liquid electrolyte side reactions, thereby improving cycle performance. Furthermore, the gel polymer electrolyte containing a third monomer significantly improves the cycle life of the battery under a charging cutoff voltage of 4.5V.

[0107] 3. Needle prick test

[0108] The batteries prepared in Example 21 and Comparative Examples 1 and 2 were subjected to a nail penetration test under a full charge condition of 4.5V. The test results of Example 21 and Comparative Examples 1 and 2 are as follows: Figure 4 , Figure 5 , Figure 6 As shown. From Figure 4It can be seen that the gel polymer battery prepared in Example 21 passed the nail penetration test, and after the nail penetration test, the temperature rise was less than 20 degrees Celsius, the voltage dropped from 4.5V to 4.3V and remained stable; under the same test conditions, the batteries prepared in Comparative Examples 1 and 2 caught fire and exploded during the test, and the voltage dropped to zero instantly. This indicates that the gel polymer electrolyte containing the third monomer can greatly improve the safety of the battery.

[0109] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A gel polymer electrolyte precursor, characterized in that, Made from the following raw materials in parts by weight: First monomer: 1-8 parts; Second monomer: 0.5-5 parts; Third monomer: 0.1-6 parts; Initiator: 0.01-1 part; Lithium salt: 5-25 parts; Organic solvent: 50-90 parts; Electrolyte additive: 0-10 parts; The first monomer is selected from at least one of divinylbenzene, divinyltoluene, divinylnaphthalene, trivinylbenzene, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, N,N'-methylenebisacrylamide, N,N'-divinylethylenediamine, diallyl phthalate, diallyl maleate, and their derivatives. The second monomer is selected from at least one of pentaerythritol tetraacrylate ethoxylate, pentaerythritol tetraacrylate propoxylate, bis(trimethylolpropane)tetraacrylate, pentaerythritol triacrylate, trimethylolpropane trimethacrylate, propoxylated glycerol triacrylate, tri(2-hydroxyethyl)isocyanurate triacrylate, trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, and poss-octaacrylate. The third monomer is a halogenated acrylate derivative.

2. The gel polymer electrolyte precursor according to claim 1, characterized in that, The third monomer is selected from 2-(perfluorooctyl)ethyl methacrylate, perfluoroalkyl ethyl methacrylate, 2-chloroethyl methacrylate, 6-bromohexyl methacrylate, 2-bromoethyl methacrylate, 2,4,6-tribromophenyl methacrylate, 2,4,6-tribromophenyl methacrylate, pentabromobenzyl methacrylate, 3,3,4,4,5,5,6,6,7,7,8,8,8-tetrafluorooctyl methacrylate, 2,2,3,3,4,4,4-heptafluorobutyl methacrylate, pentabromophenyl methacrylate, pentabromobenzyl methacrylate, and 2-chloroethylmethyl methacrylate. The ester, 2,2,3,3-tetrafluoropropyl methacrylate, 1H,1H-perfluoron-octyl acrylate, 2,3-dibromopropyl acrylate, 1H,1H,11H-perfluoroundecyl methacrylate, 2,2,3,3,4,4,4-heptafluorobutyl methacrylate, 2-methyl-2-(trifluoromethylsulfonamide)propyl methacrylate, 1H,1H,5H-octafluoropentyl acrylate, 3-perfluorohexyl-2-hydroxypropyl acrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, pentafluorophenol acrylate, and hexafluorobutyl methacrylate.

3. The gel polymer electrolyte precursor according to claim 1, characterized in that, The initiator is selected from at least one of benzoyl peroxide, dicyclohexyl peroxide, tert-butyl peroxide-2-ethylhexanoate, azobisisoheptanenitrile, and azobisisobutyronitrile.

4. The gel polymer electrolyte precursor according to claim 1, characterized in that, The organic solvent includes at least one of linear carboxylic acid esters, cyclic carbonates, fluorinated linear carboxylic acid esters, and fluorinated cyclic carbonates.

5. The gel polymer electrolyte precursor according to claim 1, characterized in that, The electrolyte additive includes at least one of vinylene carbonate, fluoroethylene carbonate, and vinyl sulfate.

6. The gel polymer electrolyte precursor according to claim 1, characterized in that, The lithium salts include at least one of LiPF6, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium bis(oxalate)borate, LiBF4, and LiClO4.

7. A gel polymer electrolyte, characterized in that, It is obtained by in-situ polymerization of the gel polymer electrolyte precursor according to any one of claims 1-6.

8. A gel polymer battery, comprising a bare battery, characterized in that, The bare battery is filled with the gel polymer electrolyte of claim 7.

9. A method for preparing a gel polymer battery as described in claim 8, characterized in that, Includes the following steps: 1) Weigh each raw material according to the mass fractions specified in claim 1, and mix the first monomer, the second monomer, the third monomer, the initiator, the lithium salt, the organic solvent and the electrolyte additive evenly under environmental conditions where the moisture and oxygen contents are both less than or equal to 0.01 ppm, to obtain the gel polymer electrolyte precursor; 2) The gel polymer electrolyte precursor is injected into the assembled bare battery, and after being left to stand and encapsulated, an in-situ polymerization reaction is initiated by heating to obtain a gel cell. 3) The gel cell prepared in step 2) is placed under a pressure of 2-100 psi, and then pre-charged, formed, and capacity tested to obtain a gel polymer battery.

10. The method for preparing a gel polymer battery according to claim 9, characterized in that, The in-situ polymerization reaction described in step 1) is carried out at a pressure of 2-100 psi and a temperature of 40-80℃ for 12-96 hours; the standing time described in step 2) is 12-48 hours at room temperature.

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