Gel electrolyte and preparation method and application thereof

Abstract

The invention belongs to the technical field of batteries, and particularly relates to a gel electrolyte as well as a preparation method and application thereof. The gel electrolyte mainly comprises a first monomer, a second monomer, an initiator and an electrolyte, the first monomer is selected from one of pentaerythritol tetraacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate and allyl methacrylate; the second monomer is selected from one of triallyl phosphate, triallyl phosphate and triethyl phosphate; the mass ratio of the first monomer to the second monomer is (1.5-2): (1-1.5). The invention also provides a preparation method and application of the gel electrolyte. According to the gel electrolyte as well as the preparation method and the application thereof, the prepared gel electrolyte is high in conductivity and good in thermal safety capability, and meanwhile, the intrinsic safety capability of a gel electrolyte cell is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of batteries, and in particular relates to a gel electrolyte and a preparation method and application thereof. Background Art

[0002] In recent years, the application of lithium-ion batteries has developed rapidly. Against the background of the rapid development of industries such as electric vehicles, electric light vehicles, power tools, consumer electronics and new energy storage, the comprehensive advantages of lithium-ion batteries are in line with the downstream fields' increasing demand for large capacity, high power, service life and environmental protection, and have broad application prospects and market prospects.

[0003] However, most lithium-ion batteries on the market at this stage use liquid electrolytes, mainly because of their high conductivity, wettability and low interfacial impedance, but liquid electrolytes have a low flash point and are flammable, which greatly increases the safety risks of lithium-ion batteries. When using gel electrolytes, the electrolyte forms a gel substance after gelation, forming a three-dimensional network structure to lock the residual liquid electrolyte, so that the liquid electrolyte no longer has fluidity, avoiding leakage and other problems, thereby greatly improving the safety performance of the battery. However, the current gel electrolytes have the disadvantages of low conductivity and large DC impedance, which have a deterioration in the rate performance, DC internal resistance (DCR), cycle, and fast charging performance of the gel electrolyte battery obtained after injection into the battery cell.

[0004] Patent CN114824460A discloses a method for preparing an in-situ synthesized high-performance gel electrolyte, wherein an olefin monomer is mixed with an organic electrolyte, an initiator is added, and a gel electrolyte is formed by post-treatment. The olefin monomer is an acrylate monomer, including one or more of polyethylene glycol diacrylate, polyethylene glycol acrylate, polyethylene glycol dimethacrylate, pentaerythritol tetraacrylate, and trimethylolpropane triacrylate. Although the gel electrolyte prepared by this method has good conductivity and thermal stability, no thermal stabilizer is added during the preparation process, and the thermal stability can be further improved. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a gel electrolyte and a preparation method and application thereof, with the aim of making the prepared gel electrolyte have high conductivity and good thermal safety, while improving the intrinsic safety of the gel electrolyte battery cell.

[0006] In order to achieve the above-mentioned purpose, the present invention provides a gel electrolyte, comprising a first monomer, a second monomer, an initiator and an electrolyte; the first monomer is selected from one of pentaerythritol tetraacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate and allyl methacrylate; the second monomer is selected from one of triallyl phosphate, tripropylene phosphite and triethyl phosphite; the mass ratio of the first monomer to the second monomer is 1.5-2:1-1.5.

[0007] The first monomer and the second monomer can work synergistically to improve the conductivity of the gel electrolyte and improve the thermal safety capability. The first monomer acts as a cross-linking body to build a three-dimensional structure in the gel electrolyte, locking the liquid electrolyte in a mesh shape, and has good ion conductivity. The second monomer acts as a thermal stabilizer, which can inhibit the conversion of CO to CO2 when absorbing heat, thereby improving the thermal safety capability of the gel electrolyte. When the gel electrolyte is injected into the battery cell, the intrinsic safety capability of the battery cell is improved.

[0008] Furthermore, the electrolyte includes a solvent and an electrolyte.

[0009] Furthermore, the solvent is obtained by mixing ethylene carbonate, ethyl methyl carbonate, diethyl carbonate and fluoroethylene carbonate in proportion.

[0010] Furthermore, the above ratio is ethylene carbonate:ethyl methyl carbonate:diethyl carbonate:fluoroethylene carbonate=2:2:2:1.

[0011] Furthermore, the electrolyte is one of LiPF6, LiFSI and LiTFSI.

[0012] Furthermore, the initiator is one of azobisisobutyronitrile and azobisisoheptanenitrile; the mass of the initiator is 0.1% of the mass of the electrolyte.

[0013] The present invention also provides a method for preparing the above-mentioned gel electrolyte, comprising the following steps:

[0014] Step S1, preparing an electrolyte;

[0015] Step S2, adding the first monomer and the second monomer into the electrolyte to obtain a mixed electrolyte;

[0016] Step S3, adding an initiator to the mixed electrolyte and stirring the mixture to obtain a gel electrolyte.

[0017] Furthermore, the gel electrolyte is in a flowing state.

[0018] The present invention also provides an application of a gel electrolyte in a gel electrolyte battery cell. The gel electrolyte is injected into the battery cell for copolymerization reaction to obtain the gel electrolyte battery cell.

[0019] Furthermore, the copolymerization reaction temperature is 35-60° C., and the time is 8-72 hours; preferably, the copolymerization reaction temperature is 45° C., and the time is 48 hours.

[0020] Beneficial Effects

[0021] In the gel electrolyte of the present invention, the first monomer and the second monomer work synergistically to improve the conductivity and thermal safety of the gel electrolyte. The first monomer acts as a cross-linking body to build a three-dimensional structure in the gel electrolyte, locks the liquid electrolyte in a mesh shape, and has good ion conductivity. The second monomer acts as a thermal stabilizer and can inhibit the conversion of CO into CO2 when absorbing heat, thereby improving the thermal safety of the gel electrolyte. When the gel electrolyte is injected into the battery cell, the intrinsic safety of the gel electrolyte battery cell is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The figure is a reaction flow chart for the copolymerization of the first monomer and the second monomer. DETAILED DESCRIPTION

[0023] The present invention is further illustrated by specific examples below. These examples are exemplary and are intended to illustrate the problem and explain the present invention, but are not intended to be limiting.

[0024] Example 1

[0025] A gel electrolyte comprises a first monomer, a second monomer, an initiator and an electrolyte; the first monomer is selected from one of pentaerythritol tetraacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate and allyl methacrylate; the second monomer is selected from one of triallyl phosphate, triallyl phosphite and triethyl phosphite; the mass ratio of the first monomer to the second monomer is 1.5-2:1-1.5.

[0026] The first monomer and the second monomer can work synergistically to improve the conductivity of the gel electrolyte and improve the thermal safety capability. The first monomer acts as a cross-linking body to build a three-dimensional structure in the gel electrolyte, locking the liquid electrolyte in a mesh shape, and has good ion conductivity. The second monomer acts as a thermal stabilizer, which can inhibit the conversion of CO to CO2 when absorbing heat, thereby improving the thermal safety capability of the gel electrolyte. When the gel electrolyte is injected into the battery cell, the intrinsic safety capability of the battery cell is improved.

[0027] The electrolyte includes a solvent and an electrolyte.

[0028] The solvent is obtained by mixing ethylene carbonate, ethyl methyl carbonate, diethyl carbonate and fluoroethylene carbonate in proportion.

[0029] The ratio is ethylene carbonate:ethyl methyl carbonate:diethyl carbonate:fluoroethylene carbonate=2:2:2:1.

[0030] The electrolyte is one of LiPF6, LiFSI and LiTFSI.

[0031] The initiator is one of azobisisobutyronitrile and azobisisoheptanenitrile; the mass of the initiator is 0.1% of the mass of the electrolyte.

[0032] Example 2

[0033] A method for preparing a gel electrolyte comprises the following steps:

[0034] Step S1, ethylene carbonate, ethyl methyl carbonate, diethyl carbonate, and fluoroethylene carbonate are mixed in a volume ratio of 2:2:2:1 to prepare a solvent, and electrolyte LiPF6 is added to the solvent so that the concentration of electrolyte LiPF6 in the electrolyte is 1 mol / L, thereby preparing an electrolyte;

[0035] Step S2, adding 2 g of pentaerythritol tetraacrylate and 1 g of triallyl phosphate to 100 g of the electrolyte to obtain a mixed electrolyte;

[0036] Step S3, adding 0.1 g of azobisisobutyronitrile (AIBN) to the mixed electrolyte, stirring evenly, to obtain a gel electrolyte.

[0037] Example 3

[0038] A method for preparing a gel electrolyte comprises the following steps:

[0039] Step S1, ethylene carbonate, ethyl methyl carbonate, diethyl carbonate, and fluoroethylene carbonate are mixed in a volume ratio of 2:2:2:1 to prepare a solvent, and electrolyte LiPF6 is added to the solvent so that the concentration of electrolyte LiPF6 in the electrolyte is 1 mol / L, thereby preparing an electrolyte;

[0040] Step S2, adding 1.9 g of methyl methacrylate and 1 g of triethyl phosphite to 100 g of the electrolyte to obtain a mixed electrolyte;

[0041] Step S3, adding 0.1 g of azobisisobutyronitrile (AIBN) to the mixed electrolyte, stirring evenly, to obtain a gel electrolyte.

[0042] Example 4

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

[0044] Step S1, ethylene carbonate, ethyl methyl carbonate, diethyl carbonate, and fluoroethylene carbonate are mixed in a volume ratio of 2:2:2:1 to prepare a solvent, and electrolyte LiPF6 is added to the solvent so that the concentration of electrolyte LiPF6 in the electrolyte is 1 mol / L, thereby preparing an electrolyte;

[0045] Step S2, adding 2 g of methyl methacrylate and 1 g of triallyl phosphate to 100 g of the electrolyte to obtain a mixed electrolyte;

[0046] Step S3, adding 0.1 g of azobisisobutyronitrile (AIBN) to the mixed electrolyte, stirring evenly, to obtain a gel electrolyte.

[0047] Comparative Example 1

[0048] A method for preparing a gel electrolyte comprises the following steps:

[0049] Step S1, ethylene carbonate, ethyl methyl carbonate, diethyl carbonate, and fluoroethylene carbonate are mixed in a volume ratio of 2:2:2:1 to prepare a solvent, and electrolyte LiPF6 is added to the solvent so that the concentration of electrolyte LiPF6 in the electrolyte is 1 mol / L, thereby preparing an electrolyte;

[0050] Step S2, adding 1 g of pentaerythritol tetraacrylate and 2 g of triallyl phosphate to 100 g of the electrolyte to obtain a mixed electrolyte;

[0051] Step S3, adding 0.1 g of azobisisobutyronitrile (AIBN) to the mixed electrolyte, stirring evenly, to obtain a gel electrolyte.

[0052] Comparative Example 2

[0053] A method for preparing a gel electrolyte comprises the following steps:

[0054] Step S1, ethylene carbonate, ethyl methyl carbonate, diethyl carbonate, and fluoroethylene carbonate are mixed in a volume ratio of 2:2:2:1 to prepare a solvent, and electrolyte LiPF6 is added to the solvent so that the concentration of electrolyte LiPF6 in the electrolyte is 1 mol / L, thereby preparing an electrolyte;

[0055] Step S2, adding 2 g of pentaerythritol tetraacrylate and 2 g of triallyl phosphate to 100 g of the electrolyte to obtain a mixed electrolyte;

[0056] Step S3, adding 0.1 g of azobisisobutyronitrile (AIBN) to the mixed electrolyte, stirring evenly, to obtain a gel electrolyte.

[0057] Analysis of performance and safety performance of gel electrolyte battery cells

[0058] The gel electrolytes obtained in Example 2, Example 3, Example 4, Comparative Example 1 and Comparative Example 2 were injected into battery cells for copolymerization. The copolymerization temperature was 45° C. for 48 hours to obtain gel electrolyte battery cells. The performance and safety performance of the obtained gel electrolyte battery cells were analyzed. The performance and safety performance of the gel electrolyte battery cells can be reflected by cycle data and hot box safety data. The data are summarized in Table 1.

[0059] In Example 2, the first monomer is pentaerythritol tetraacrylate, and the second monomer is triallyl phosphate, and the mass ratio of the two is 2:1. In Example 3, the first monomer is methyl methacrylate, and the second monomer is triethyl phosphite, and the mass ratio of the two is 1.9:1. In Example 4, the first monomer is methyl methacrylate, and the second monomer is triallyl phosphate, and the mass ratio of the two is 2:1. In Comparative Example 1, the mass ratio of the first monomer pentaerythritol tetraacrylate and the second monomer triallyl phosphate is 1:2, and in Comparative Example 2, the mass ratio of the first monomer pentaerythritol tetraacrylate and the second monomer triallyl phosphate is 1:1. After the mass ratio of the first monomer and the second monomer was changed in the examples and comparative examples, the performance and safety performance of the prepared gel electrolyte battery cells also differed. The conductivity of the gel electrolyte cells of Example 2, Example 3 and Example 4 is higher than 9.0 mS / cm, and the conductivity is high, and is significantly higher than the conductivity of the gel electrolyte cells of Comparative Example 1 and Comparative Example 2. In addition, the hot box passing temperature is above 160° C. At the same time, the gel electrolyte cell of Example 2 has a cycle performance of 80% after 800 cycles, the gel electrolyte cells of Example 3 and Example 4 have a cycle performance of 80% after 700 cycles, and the gel electrolyte cells of Comparative Example 1 and Comparative Example 2 have a cycle performance of 80% after 600 cycles and 550 cycles, respectively. The cycle performance of the gel electrolyte cells of Example 2, Example 3 and Example 4 is significantly higher than that of the gel electrolyte cells of Comparative Example 1 and Comparative Example 2. Therefore, when preparing the gel electrolyte solution, the first monomer and the second monomer are added, and the mass ratio of the first monomer to the second monomer is 1.5-2:1-1.5, the gel electrolyte cell has high conductivity, good thermal safety performance, and improved intrinsic safety capability.

[0060] Table 1 Gel electrolyte battery performance and safety performance data

[0061]

[0062]

Claims

1. A gel electrolyte, characterized in that: The invention comprises a first monomer, a second monomer, an initiator and an electrolyte; the first monomer is selected from one of pentaerythritol tetraacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate and allyl methacrylate; the second monomer is selected from one of triallyl phosphate, triallyl phosphite and triethyl phosphite; the mass ratio of the first monomer to the second monomer is 1.5-2:1-1.

5.

2. The gel electrolyte according to claim 1, characterized in that: The electrolyte solution includes a solvent and an electrolyte.

3. The gel electrolyte according to claim 2, characterized in that: The solvent is obtained by mixing ethylene carbonate, ethyl methyl carbonate, diethyl carbonate and fluoroethylene carbonate in a certain proportion.

4. The gel electrolyte according to claim 3, characterized in that: The ratio is ethylene carbonate:ethyl methyl carbonate:diethyl carbonate:fluoroethylene carbonate=2:2:2:

1.

5. The gel electrolyte according to claim 2, characterized in that: The electrolyte is one of LiPF6, LiFSI and LiTFSI.

6. The gel electrolyte according to claim 1, characterized in that: The initiator is one of azobisisobutyronitrile and azobisisoheptanenitrile; the mass of the initiator is 0.1% of the mass of the electrolyte.

7. A method for preparing a gel electrolyte according to any one of claims 1 to 6, characterized in that: The steps include: Step S1, preparing an electrolyte; Step S2, adding the first monomer and the second monomer into the electrolyte to obtain a mixed electrolyte; Step S3, adding an initiator to the mixed electrolyte and stirring the mixture to obtain a gel electrolyte.

8. The method for preparing the gel electrolyte according to claim 7, characterized in that: The gel electrolyte is in a flowing state.

9. Application of a gel electrolyte in a gel electrolyte battery cell, characterized in that: After the gel electrolyte solution of claim 8 is injected into the battery cell, the first monomer and the second monomer are copolymerized to obtain the gel electrolyte battery cell.

10. The use of the gel electrolyte according to claim 9 in a gel electrolyte battery cell, characterized in that: The copolymerization reaction temperature is 35-60° C., and the time is 8-72 hours; preferably, the copolymerization reaction temperature is 45° C., and the time is 48 hours.

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