Gel electrolyte, preparation method of gel polymer electrolyte and lithium battery

Abstract

The invention discloses a gel electrolyte, a preparation method of a gel polymer electrolyte and a lithium battery, and relates to the technical field of lithium batteries. According to the invention, a strategy of combining a solid electrolyte and a liquid electrolyte is adopted, and a gel polymer electrolyte is formed between the positive electrode and the negative electrode through in-situ curing, so that the interface performance is fundamentally improved; by introducing the silicon dioxide aerogel, the coordination condition of the lithium salt in the system can be changed, so that the conductivity of the system is improved. Through combination with an electrolyte and a lithium salt, the composite electrolyte shows high ionic conductivity, good electrochemical stability, excellent short-circuit resistance and relatively high thermal stability, so that the safety of the lithium ion battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a preparation method of a gel electrolyte, a gel polymer electrolyte and a lithium battery. Background Art

[0002] Lithium-ion batteries play an important role in mobile electronic devices, electric vehicles, and energy storage systems, and electrolytes are a key factor in determining their performance. Currently, liquid electrolytes are widely used in electric vehicles and portable electronic devices due to their high energy density and mature processing technology. However, the leakability and flammability of liquid electrolytes may cause safety issues including explosions. Therefore, solid electrolytes are considered to be a potential solution to this safety issue and make it possible to directly use lithium metal as a negative electrode of the battery. Secondary lithium batteries have high operating voltage and large capacity, thereby achieving high energy density. Although some solid electrolytes exhibit high ionic conductivity at room temperature, their interaction with the electrode interface is poor, which seriously hinders the ion transport between the electrode and the solid electrolyte, resulting in high interfacial impedance, slow lithium ion diffusion, and large overpotential during cycling. At present, interface problems are considered to be the main obstacle to the application of solid-state batteries.

[0003] Gel polymer electrolyte is a network structure composed of a polymer skeleton and a liquid electrolyte plasticizer. The polar functional groups on the polymer skeleton can bind to the liquid electrolyte to provide liquid absorption capacity, while the liquid electrolyte is the main channel for lithium ion transmission. In addition, its soft properties provide good interfacial contact and significantly reduce the interfacial impedance. However, the thermal stability and mechanical properties of gel polymer electrolytes are poor. In order to solve these problems, a support membrane is introduced to form a membrane-supported gel polymer electrolyte. The support membrane provides mechanical properties and thermal stability, and the gel polymer electrolyte provides an ion transmission channel. The combination of the two can greatly improve the performance.

[0004] In order to further improve the interface problem, an in-situ curing method was used to form a gel polymer electrolyte between the positive and negative electrodes. Studies have shown that polymer electrolytes can be prepared by in-situ polymerization by mixing monomers, plasticizer solutions and lithium salts. Compared with traditional polyester-based electrolytes, gel polymer electrolytes prepared by in-situ polymerization exhibit higher discharge capacity and lower overpotential, proving that the in-situ curing method can effectively improve battery performance.

[0005] Recently, a polymer electrolyte supported by a cellulose separator was prepared by in situ polymerization. Compared with externally prepared batteries, the electrolyte exhibited lower interfacial impedance and higher ionic conductivity, which was attributed to its close interfacial contact and the strong dissociation ability of lithium salts during the in situ preparation process. In addition, the support membrane needs to have high thermal stability, good electrochemical stability and excellent liquid absorption capacity. Glass fiber membrane has attracted attention due to its high thermal stability and excellent electrochemical stability. However, its large pore size may cause the active electrode material to penetrate and cause local short circuits, so filling the polymer electrolyte by phase inversion or in situ polymerization is a feasible solution. In addition, due to the poor wettability of solid electrolytes, structural defects are easily formed at the solid-solid contact interface between the positive and negative electrodes, resulting in poor interfacial compatibility, thereby causing higher interfacial impedance.

[0006] In summary, there is an urgent need to improve the interfacial compatibility of gel electrolytes and improve the high-temperature stability of lithium batteries.

[0007] In view of this, the present invention is proposed. Summary of the invention

[0008] The purpose of the present invention is to provide a preparation method of a gel electrolyte, a gel polymer electrolyte and a lithium battery, aiming to solve the problem of interface compatibility and improve the high temperature stability of the lithium battery.

[0009] The present invention is achieved in that:

[0010] In a first aspect, the present invention provides a gel electrolyte for preparing a gel polymer electrolyte after in-situ polymerization, comprising: an electrolyte, a polymer matrix and an inorganic filler, wherein the electrolyte comprises a lithium salt and a solvent;

[0011] Wherein, the polymer matrix includes acrylic monomers, a photoinitiator, a crosslinking agent and a thermal initiator;

[0012] The inorganic filler is silicon dioxide aerogel; the mass ratio of the inorganic filler to the acrylic acid monomer is (0-14):100.

[0013] In an optional embodiment, the mass ratio of the inorganic filler to the acrylic monomer is (8-10):100.

[0014] In an optional embodiment, in the polymer matrix, the mass ratio of acrylic monomer, photoinitiator, crosslinker and thermal initiator is 1:(0.01-0.03):(0.01-0.03):(0.01-0.03).

[0015] In an alternative embodiment, the acrylic acid monomer is butyl acrylate;

[0016] and / or, the photoinitiator is 2-hydroxy-2-methylpropiophenone;

[0017] and / or, the cross-linking agent is ethylene glycol dimethacrylate;

[0018] And / or, the thermal initiator is azobisisobutyronitrile.

[0019] In an optional embodiment, the mass ratio of the electrolyte to the acrylic acid monomer is (0.8-1.2): 1; and / or, the lithium salt is selected from at least one of LiPF6 and LiTFSI;

[0020] and / or, the concentration of lithium salt in the electrolyte is 0.8 mol / L-1.2 mol / L;

[0021] And / or, the solvent is selected from at least one of ethylene carbonate and diethyl carbonate.

[0022] In an optional embodiment, the solvent includes ethylene carbonate and diethyl carbonate, and the mass ratio of ethylene carbonate to diethyl carbonate is 1:(0.8-1.2).

[0023] In a second aspect, the present invention provides a method for preparing a gel polymer electrolyte, comprising: immersing a separator in the gel electrolyte of any one of the aforementioned embodiments, and polymerizing under ultraviolet irradiation conditions to obtain a prepolymerized modified separator;

[0024] The pre-polymerized modified separator is assembled into a lithium battery and then heated and polymerized.

[0025] In an optional embodiment, the separator is first immersed in a gel electrolyte for 10 seconds to 3 minutes, and then irradiated with ultraviolet light for 15 minutes to 60 minutes to obtain a pre-polymerized modified separator;

[0026] And / or, the separator is selected from at least one of a glass fiber separator, a polypropylene separator (PP) and a non-woven fabric separator.

[0027] In an optional embodiment, during the heating polymerization, the polymerization temperature is controlled to be 55° C.-65° C., and the polymerization time is 20 min-60 min;

[0028] And / or, assembling the prepolymerized modified separator, the positive electrode, the negative electrode and the electrolyte into a lithium battery.

[0029] In a third aspect, the present invention provides a lithium battery having a gel polymer electrolyte, which is prepared by the preparation method of any one of the aforementioned embodiments.

[0030] The present invention has the following beneficial effects: the present invention adopts a strategy of combining solid electrolyte and liquid electrolyte, forms a gel polymer electrolyte between the positive and negative electrodes by in-situ solidification, and fundamentally improves the interface performance; the introduction of silica aerogel can change the coordination of lithium salts in the system, thereby improving the conductivity of the system. By combining with electrolyte and lithium salt, the composite electrolyte exhibits high ionic conductivity, good electrochemical stability, excellent short-circuit resistance and high thermal stability, thereby improving the safety of lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 The dissolution diagrams of the solutions with silica aerogel dosages of 0.14, 0.12, and 0.1 respectively; (a), (b), and (c) are the dissolution diagrams of 0.14g, 0.12g, and 0.1g respectively;

[0033] Figure 2 Schematic diagram of impedance test of gel electrolyte in SS||SS battery;

[0034] Figure 3 Schematic diagram of the conductivity of gel electrolyte;

[0035] Figure 4 The results of LSV test of gel electrolyte PBA-Base system, PBA-0.08g SiO2 system and PBA-0.1gSiO2 system in Li||SS battery;

[0036] Figure 5 This is a comparison chart of the cycling performance of the gel electrolyte PBA-Base system, PBA-0.08g SiO2 system and PBA-0.1gSiO2 system at 4.2V;

[0037] Figure 6 This is a performance comparison chart of the gel electrolyte PBA-Base system, PBA-0.08g SiO2 system and PBA-0.1gSiO2 system at different rates of 0.1C, 0.2C, 0.5C and 0.1C;

[0038] Figure 7This is a comparison chart of the thermogravimetric properties of the gel electrolyte PBA-Base system, PBA-0.08g SiO2 system and PBA-0.1gSiO2 system. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0040] Since the solid electrolyte has poor wettability, it is easy to form structural defects at the solid-solid contact interface between the positive and negative electrodes, resulting in poor interface compatibility, thereby causing higher interface impedance. To address this problem, the present invention adopts a strategy of combining solid electrolytes with liquid electrolytes, optimizes the composition of gel electrolytes, selects butyl acrylate and the like as a polymer matrix, and introduces liquid electrolytes to form a gel polymer electrolyte between the positive and negative electrodes through in-situ curing, thereby fundamentally improving the interface performance.

[0041] The embodiment of the present invention provides a gel electrolyte. The gel electrolyte can be used to prepare a gel polymer electrolyte through in-situ polymerization. The gel polymer electrolyte includes an electrolyte, a polymer matrix and an inorganic filler. The electrolyte includes a lithium salt and a solvent.

[0042] Among them, the inorganic filler is silica aerogel, which is negatively charged. After being added to the PBA-Base system, due to the mutual attraction between positive and negative charges, the silica aerogel will absorb some of the Li+ in the system, thereby affecting the anions and Li in the system. + Due to its high elastic modulus, high porosity and large internal surface area, silica aerogel provides a large and continuous adsorption surface for lithium ions, forming the characteristics of lithium-rich channels, thereby reducing the resistance to ion migration, which not only significantly improves the ionic conductivity of the electrolyte, but also enhances the rate performance and high voltage performance of the battery.

[0043] In addition to improving electrochemical performance, silica aerogel also has the following advantages: Silica aerogel can also improve thermal stability. Due to its high porosity and large specific surface area, silica aerogel can effectively disperse and absorb heat to prevent local overheating; secondly, the low thermal conductivity of silica aerogel can effectively isolate heat transfer and reduce the diffusion of heat inside the electrolyte, thereby reducing the temperature rise of the system; finally, silica itself has stable chemical properties and is not easy to react with electrolytes. It can maintain structural stability in high temperature environments, so that the performance of the electrolyte will not be affected by decomposition or structural changes.

[0044] The polymer matrix includes acrylic monomers, photoinitiators, cross-linking agents and thermal initiators. The introduction of photoinitiators and thermal initiators can initiate synergistic cooperation through ultraviolet light and heating to prepare gel polymer electrolytes in situ, greatly improve interfacial impedance, and have good flame retardancy and ionic conductivity, so that the prepared lithium battery has good cycle stability, better rate performance and a wider electrochemical window.

[0045] In some embodiments, the acrylic monomer is butyl acrylate (BA). When polybutyl acrylate is used as the polymer matrix material, its flexibility and long side chains can bring good interfacial adhesion. The photoinitiator is 2-hydroxy-2-methylpropiophenone (HMPP), the crosslinker is ethylene glycol dimethacrylate (EDGMA), and the thermal initiator is azobisisobutyronitrile (AIBN).

[0046] Furthermore, in the polymer matrix, the mass ratio of acrylic monomer, photoinitiator, crosslinker and thermal initiator is 1:(0.01-0.03):(0.01-0.03):(0.01-0.03), and the amount of photoinitiator, crosslinker and thermal initiator is preferably within the above range, which can further improve the interfacial properties of the prepared gel polymer electrolyte. Specifically, the amount of photoinitiator, crosslinker and thermal initiator can be the same or different. When the amount of acrylic monomer is 1, the amount of photoinitiator, crosslinker and thermal initiator can independently be 0.01, 0.02, 0.03, etc.

[0047] Furthermore, the mass ratio of the inorganic filler to the acrylic monomer is (0-14):100, such as 0:100, 2:100, 4:100, 6:100, 8:100, 9:100, 10:100, 12:100, 14:100, etc. In a preferred embodiment, the mass ratio of the inorganic filler to the acrylic monomer is (8-10):100, which is more conducive to improving the battery performance within this range, and obtaining better cycle stability, thermal stability and rate performance.

[0048] In some embodiments, the mass ratio of the electrolyte to the acrylic acid monomer is (0.8-1.2):1, such as 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, etc. The lithium salt is selected from at least one of lithium hexafluorophosphate (LiPF6) and LiTFSI, and the lithium salt can be any one or more of the above. The solvent is selected from at least one of ethylene carbonate (EC) and diethyl carbonate (DEC), and the solvent can be any one or more of the above. In a preferred embodiment, the solvent includes ethylene carbonate (EC) and diethyl carbonate (DEC), and the structures of ethylene carbonate (EC) and diethyl carbonate (DEC) are as follows:

[0049]

[0050] The mass ratio of ethylene carbonate to diethyl carbonate is 1:(0.8-1.2), such as 1:0.8, 1:0.9, 1:1.0, 1:1.1, 1:1.2, etc. By adjusting the amount of solvent, the concentration of lithium salt in the electrolyte is 0.8mol / L-1.2mol / L, such as 0.8mol / L, 0.9mol / L, 1.0mol / L, 1.1mol / L, 1.2mol / L, etc. The introduction of a liquid electrolyte containing LiPF6, EC and DEC is conducive to further improving the interfacial properties of the gel electrolyte.

[0051] In summary, the present invention successfully solves the problems of interface compatibility and high temperature stability through innovative design and material selection, and provides a reliable solution for improving the performance of lithium metal batteries. A composite gel polymer electrolyte with excellent mechanical properties was prepared by combining polybutyl acrylate, glass fiber membrane and lithium salt LiPF6 through in-situ polymerization, and introducing silica aerogel as filler.

[0052] An embodiment of the present invention provides a method for preparing a gel polymer electrolyte, comprising:

[0053] S1. UV polymerization

[0054] The separator is immersed in the gel electrolyte provided in the embodiment of the present invention, and polymerization is initiated by a photoinitiator under ultraviolet irradiation conditions to obtain a prepolymerized modified separator.

[0055] In some embodiments, the diaphragm can be first soaked in the gel electrolyte for 10s-3min, and then UV-irradiated for 15min-60min to obtain a pre-polymerized modified diaphragm. Soaking first and then UV-polymerizing can allow the reaction to proceed fully. Specifically, the soaking time in the gel electrolyte can be 10s, 20s, 30s, 1min, 2min, 3min, etc.; the UV lamp power of the UV irradiation is 40W, the wavelength is 385nm, and the irradiation time can be 15min, 20min, 30min, 40min, 50min, 60min, etc.

[0056] In some embodiments, the diaphragm is selected from at least one of glass fiber diaphragm, PP, and non-woven fabric, and the material of the diaphragm can be any one or more of the above. In lithium batteries, the physical structure and chemical stability of the diaphragm are key factors affecting high temperature performance. Since silicon-containing compounds have good high temperature resistance, the present invention uses glass fiber as the diaphragm material and introduces silica aerogel as filler, which is evenly distributed inside the diaphragm, thereby improving the high temperature resistance of the battery.

[0057] It should be noted that the silicon-oxygen bonds in the glass fibers can interact with lithium ions to form continuous lithium ion transmission channels, thereby giving the composite material a wide electrochemical stability window and a higher lithium ion migration number, which can provide thermal stability and electrochemical stability.

[0058] S2. Heating and polymerization after assembly

[0059] The prepolymerized modified diaphragm is assembled into a lithium battery by conventional methods, and then heated and polymerized, and prepared by an in-situ polymerization method to obtain a gel polymer electrolyte with good chemical stability. By the in-situ curing polymerization method, the gel electrolyte liquid precursor is directly added during the battery assembly process, and the liquid precursor is completely polymerized by thermal initiation, cross-linking or adding an initiator. Since the injected electrolyte is liquid, it can fully penetrate into the pores of the electrode material, so that the in-situ formed gel electrolyte is tightly combined with the electrode material, achieving good interface compatibility and low interface impedance.

[0060] In some embodiments, during the heating polymerization, the polymerization temperature is controlled to be 55°C-65°C, and the polymerization time is 20min-60min, and the acrylic acid monomer is fully polymerized by adjusting the polymerization temperature and time. Specifically, the polymerization temperature can be 55°C, 58°C, 60°C, 63°C, 65°C, etc., and the polymerization time can be 20min, 30min, 40min, 50min, 60min, etc.

[0061] There is no limit to the assembly method of lithium batteries. Lithium batteries are assembled using prepolymer modified diaphragms, positive electrodes, negative electrodes and electrolytes. Specifically, lithium metal batteries can be assembled according to negative electrode shells, shrapnel, gasket, lithium sheet, electrolyte, prepolymer modified diaphragms, electrolyte, LFP811 positive electrode sheet and positive electrode shell. The negative electrode shell and positive electrode shell can be commonly used lithium battery CR2032 battery shells; the shrapnel material of lithium ion button batteries is usually stainless steel, and its main function is to support the battery during the battery assembly process to prevent the battery from being flattened during the pressure battery step, thereby protecting the internal components from being crushed; the gasket material can be stainless steel, and its function is to isolate the positive and negative electrodes, prevent short circuits, and improve the safety and cycle life of the battery; the electrolyte can be a mixture of LiPF6, EC, and DEC, with a LiPF6 concentration of 1M and a volume ratio of EC to DEC of 1:1.

[0062] The present invention provides a lithium battery with a gel polymer electrolyte, which is prepared by the preparation method provided by the present invention. The in-situ prepared battery exhibits excellent interface contact performance, good cycle stability and rate performance, further indicating that the in-situ polymerization method can significantly improve battery performance.

[0063] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0064] Example 1

[0065] This embodiment provides a method for preparing a gel polymer electrolyte, the steps are as follows:

[0066] (1) Providing a gel electrolyte liquid system

[0067] In an argon-filled glove box with an atmosphere where the oxygen and water content are both lower than 0.1 ppm, the organic solvents butyl acrylate BA, 2-hydroxy-2-methylpropiophenone (HMPP), ethylene glycol dimethacrylate (EDGMA), and azobisisobutyronitrile (AIBN) are firstly mixed uniformly according to the weights of 1 g, 0.02 g, 0.02 g, and 0.02 g, respectively, and then 1 g of 1.0 M LiPF6 in ECDEC 1:1 electrolyte (the concentration of LiPF6 is 1 mol / L, and the volume ratio of EC to DEC is 1:1) is added, and the mixture is thoroughly stirred and dissolved uniformly until the electrolyte is clear and transparent to obtain a gel electrolyte liquid system, namely, the PBA-Base system (unpolymerized).

[0068] (2) UV polymerization

[0069] The polymerization process is as follows: first, take out a glass fiber membrane with a thickness of 2.7 μm, soak the front and back sides of the glass fiber membrane in the prepared gel electrolyte liquid system for 30 seconds, then place it in the solar panel, turn on the ultraviolet light for 25 minutes to complete the initial polymerization.

[0070] (3) Heating and polymerization after assembly

[0071] After the battery is assembled, it is baked in an oven at 60°C for 30 minutes, and the polymerization is completed. The battery assembly process is as follows:

[0072] Li||LFP811 battery: In a glove box filled with argon, use the preliminarily polymerized glass fiber (GF) as the separator, the lithium iron phosphate positive electrode material LFP811 as the positive electrode, and lithium metal as the negative electrode. Add the above electrolyte (1.0M LiPF6 in EC DEC1:1 electrolyte) and assemble the lithium metal battery according to the negative electrode shell, shrapnel, gasket, lithium sheet, 40μL electrolyte, separator, 40μL electrolyte, LFP811 positive electrode sheet, and positive electrode shell. After assembly, put the battery in an oven at 60℃ for 30min.

[0073] Li||Li battery: Except that the positive electrode sheet LFP811 is replaced with a lithium sheet, the other components are the same as the Li||LFP811 battery.

[0074] Li||SS battery: Except that the positive electrode LFP811 is replaced with a stainless steel gasket, the other components are the same as the Li||LFP811 battery.

[0075] SS||SS battery: Both the positive electrode LFP811 and the negative electrode lithium metal are replaced with stainless steel gaskets.

[0076] Example 2

[0077] This embodiment provides a method for preparing a gel polymer electrolyte, the steps are as follows:

[0078] (1) Providing a gel electrolyte liquid system

[0079] The preparation scheme of the gel electrolyte is as follows: in an argon-filled glove box with an atmosphere where the oxygen and water content are both lower than 0.1 ppm, first, the organic solvents butyl acrylate BA, 2-hydroxy-2-methylpropiophenone (HMPP), ethylene glycol dimethacrylate (EDGMA), and azobisisobutyronitrile (AIBN) are mixed uniformly according to the weights of 1g, 0.02g, 0.02g, and 0.02g, respectively, and then 1g of 1.0M LiPF6in EC DEC 1:1 electrolyte is added, and the mixture is fully stirred and dissolved until the electrolyte is clear and transparent, and then 0.02g of silica aerogel is added, and the mixture is fully stirred and dissolved to obtain a PBA-0.02g SiO2 system.

[0080] (2) UV polymerization

[0081] Refer to Example 1.

[0082] (3) Heating and polymerization after assembly

[0083] After the battery is assembled, it is baked in an oven at 60°C for 30 minutes, and the polymerization is completed. The battery assembly process is as follows:

[0084] Li||Li battery: Except that the positive electrode sheet LFP811 is replaced with a lithium sheet, the other components are the same as the Li||LFP811 battery.

[0085] Li||SS battery: Except that the positive electrode LFP811 is replaced with a stainless steel gasket, the other components are the same as the Li||LFP811 battery.

[0086] SS||SS battery: Both the positive electrode LFP811 and the negative electrode lithium metal are replaced with stainless steel gaskets.

[0087] Example 3

[0088] This embodiment provides a method for preparing a gel polymer electrolyte, the steps are as follows:

[0089] (1) Providing a gel electrolyte liquid system

[0090] The preparation scheme of the gel electrolyte is as follows: in an argon-filled glove box with an atmosphere where the oxygen and water content are both lower than 0.1 ppm, first, the organic solvents butyl acrylate BA, 2-hydroxy-2-methylpropiophenone (HMPP), ethylene glycol dimethacrylate (EDGMA), and azobisisobutyronitrile (AIBN) are mixed uniformly according to the weights of 1g, 0.02g, 0.02g, and 0.02g, respectively, and then 1g of 1.0M LiPF6in EC DEC 1:1 electrolyte is added, and the mixture is thoroughly stirred and dissolved until the electrolyte is clear and transparent, and then 0.04g of silica aerogel is added, and the mixture is thoroughly stirred and dissolved to obtain a PBA-0.04g SiO2 system.

[0091] (2) UV polymerization

[0092] Refer to Example 1.

[0093] (3) Heating and polymerization after assembly

[0094] The polymerization process is the same as in Example 1.

[0095] Li||Li battery: Same as implementation 1.

[0096] Li||SS battery: same as Example 1.

[0097] SS||SS battery: same as Example 1.

[0098] Example 4

[0099] This embodiment provides a method for preparing a gel polymer electrolyte, the steps are as follows:

[0100] (1) Providing a gel electrolyte liquid system

[0101] The preparation scheme of the gel electrolyte is as follows: in an argon-filled glove box with an atmosphere where the oxygen and water content are both lower than 0.1 ppm, first, the organic solvents butyl acrylate BA, 2-hydroxy-2-methylpropiophenone (HMPP), ethylene glycol dimethacrylate (EDGMA), and azobisisobutyronitrile (AIBN) are mixed uniformly according to the weights of 1g, 0.02g, 0.02g, and 0.02g, respectively, and then 1g of 1.0M LiPF6in EC DEC 1:1 electrolyte is added, and the mixture is fully stirred and dissolved until the electrolyte is clear and transparent, and then 0.06g of silica aerogel is added, and the mixture is fully stirred and dissolved to obtain a PBA-0.06g SiO2 system.

[0102] (2) UV polymerization

[0103] Refer to Example 1.

[0104] (3) Heating and polymerization after assembly

[0105] The polymerization process is the same as in Example 1.

[0106] Li||Li battery: Same as implementation 1.

[0107] Li||SS battery: same as Example 1.

[0108] SS||SS battery: same as Example 1.

[0109] Example 5

[0110] This embodiment provides a method for preparing a gel polymer electrolyte, the steps are as follows:

[0111] (1) Providing a gel electrolyte liquid system

[0112] The preparation scheme of the gel electrolyte is as follows: in an argon-filled glove box with an atmosphere where the oxygen and water content are both lower than 0.1 ppm, first, the organic solvents butyl acrylate BA, 2-hydroxy-2-methylpropiophenone (HMPP), ethylene glycol dimethacrylate (EDGMA), and azobisisobutyronitrile (AIBN) are mixed uniformly according to the weights of 1g, 0.02g, 0.02g, and 0.02g, respectively, and then 1g of 1.0M LiPF6in EC DEC 1:1 electrolyte is added, and the mixture is fully stirred and dissolved until the electrolyte is clear and transparent, and then 0.08g of silica aerogel is added, and the mixture is fully stirred and dissolved to obtain a PBA-0.08g SiO2 system.

[0113] (2) UV polymerization

[0114] Refer to Example 1.

[0115] (3) Heating and polymerization after assembly

[0116] The polymerization process is the same as in Example 1.

[0117] Li||LFP811 battery: same as Example 1.

[0118] Li||Li battery: same as Example 1.

[0119] Li||SS battery: same as Example 1.

[0120] SS||SS battery: same as Example 1.

[0121] Example 6

[0122] This embodiment provides a method for preparing a gel polymer electrolyte, the steps are as follows:

[0123] (1) Providing a gel electrolyte liquid system

[0124] The preparation scheme of the gel electrolyte is as follows: in an argon-filled glove box with an atmosphere where the oxygen and water content are both lower than 0.1 ppm, first, the organic solvents butyl acrylate BA, 2-hydroxy-2-methylpropiophenone (HMPP), ethylene glycol dimethacrylate (EDGMA), and azobisisobutyronitrile (AIBN) are mixed uniformly according to the weights of 1g, 0.02g, 0.02g, and 0.02g, respectively, and then 1g of 1.0M LiPF6in EC DEC 1:1 electrolyte is added, and the mixture is fully stirred and dissolved until the electrolyte is clear and transparent, and then 0.1g of silica aerogel is added, and the mixture is fully stirred and dissolved to obtain a PBA-0.1g SiO2 system.

[0125] (2) UV polymerization

[0126] Refer to Example 1.

[0127] (3) Heating and polymerization after assembly

[0128] The polymerization process is the same as in Example 1.

[0129] Li||LFP811 battery: same as Example 1.

[0130] Li||Li battery: same as Example 1.

[0131] Li||SS battery: same as Example 1.

[0132] SS||SS battery: same as Example 1.

[0133] Example 7

[0134] The present embodiment provides a gel electrolyte liquid system, and the preparation scheme of the gel electrolyte is as follows: in an atmosphere filled with argon gas and in which the content of oxygen and water are both lower than 0.1 ppm, firstly, the organic solvents butyl acrylate BA, 2-hydroxy-2-methylpropiophenone (HMPP), ethylene glycol dimethacrylate (EDGMA), and azobisisobutyronitrile (AIBN) are uniformly mixed according to the weights of 1 g, 0.02 g, 0.02 g, and 0.02 g, respectively, and then 1 g of 1.0 M LiPF6 in EC DEC 1:1 electrolyte is added, and the mixture is fully stirred and dissolved until the electrolyte is clear and transparent, and then 0.12 g of silica aerogel is added, and the mixture is stirred and dissolved to obtain a PBA-0.12 g SiO2 system.

[0135] Example 8

[0136] The present embodiment provides a gel electrolyte liquid system, and the preparation scheme of the gel electrolyte is as follows: in an argon-filled glove box in an atmosphere where the oxygen and water contents are both lower than 0.1 ppm, firstly, the organic solvents butyl acrylate BA, 2-hydroxy-2-methylpropiophenone (HMPP), ethylene glycol dimethacrylate (EDGMA), and azobisisobutyronitrile (AIBN) are uniformly mixed according to the weights of 1 g, 0.02 g, 0.02 g, and 0.02 g, respectively, and then 1 g of 1.0 M LiPF6 in EC DEC 1:1 electrolyte is added, and the mixture is thoroughly stirred and dissolved until the electrolyte is clear and transparent, and then 0.14 g of silica aerogel is added, and the mixture is stirred and dissolved to obtain a PBA-0.14 g SiO2 system.

[0137] Test example

[0138] (1) The dissolution of the silica aerogels in different dosages of Examples 6-8 was tested. The results are as follows Figure 1 shown.

[0139] Figure 1 The dissolution of the solution of the silica aerogel of the present invention at the dosage of 0.14, 0.12, and 0.1 is shown. It was found that: 0.14g of silica aerogel cannot be fully dissolved in the electrolyte; 0.12g of silica aerogel can be dissolved in the electrolyte, but the overall viscosity is too large and will adhere to the wall of the container; 0.1g of silica aerogel can be fully and evenly dissolved in the electrolyte system. Therefore, the subsequent electrochemical performance test uses a silica aerogel dosage of 0-10% by mass ratio to the monomer.

[0140] (2) The impedance of the SS||SS battery prepared in Examples 1-6 was tested. The results are as follows Figure 2 shown.

[0141] Figure 2 A schematic diagram showing the impedance test of the gel electrolyte of the present invention in a SS||SS battery. As can be seen from the figure, as the amount of silica aerogel increases, the impedance of the prepared gel electrolyte becomes lower.

[0142] (3) The conductivity of the gel electrolyte prepared in step (1) of Example 1-6 was tested. The results are as follows: Figure 3 shown.

[0143] Figure 3 The conductivity of the gel electrolyte of the present invention is shown in the figure. As can be seen from the figure, as the amount of silica aerogel increases, the conductivity of the prepared gel electrolyte becomes higher. Among them, the conductivity of the PBA-0.1g SiO2 system is the best, with a maximum of 1.36x10 -3 S / cm, while the PBA-Base system is 0.61x10-3 S / cm, which is increased by about 2 times.

[0144] (4) The Li||SS batteries obtained in Example 1, Example 5 and Example 6 were subjected to LSV (Linear Sweep Voltammetry) test. The results are as follows: Figure 4 shown.

[0145] Figure 4 The gel electrolyte PBA-Base system, PBA-0.08g SiO2 system and PBA-0.1g SiO2 system of the present invention are subjected to LSV test in Li||SS battery. It is usually judged that when the current changes greatly, it proves that a relatively serious oxidation has occurred at the electrolyte interface, which is also the oxidation potential of the electrolyte. As can be seen from the figure, the PBA-Base system begins to undergo oxidation reaction at a voltage of about 4.6V, while the PBA-0.08g SiO2 system and the PBA-0.1g SiO2 system begin to undergo oxidation reaction at a voltage of about 4.2V, indicating that although the addition of silica aerogel will appropriately reduce the oxidation potential, the overall oxidation potential of the system is relatively high and the electrochemical window is relatively wide.

[0146] (5) The battery performance of the Li||LFP811 battery obtained in Example 1, Example 5 and Example 6 at 4.2V is as follows Figure 5 shown.

[0147] Figure 5 The figure shows the cycle performance comparison of the gel electrolyte PBA-Base system, PBA-0.08g SiO2 system and PBA-0.1g SiO2 system at 4.2V. As can be seen from the figure, the PBA-0.08g SiO2 system and the PBA-0.1g SiO2 system show a longer cycle life at a voltage of 4.2V, which can significantly improve the cycle stability of lithium metal batteries under high voltage.

[0148] (6) The rate performance of the Li||LFP811 battery obtained in Example 1, Example 5 and Example 6 is as follows: Figure 6 shown.

[0149] Figure 6 The performance comparison diagram of the gel electrolyte PBA-Base system, PBA-0.08g SiO2 system and PBA-0.1gSiO2 system of the present invention at different rates of 0.1C, 0.2C, 0.5C and 0.1C is shown. As can be seen from the figure, the overall rate performance of the three systems is excellent, and with the increase of the silica aerogel content, the rate performance gradually improves.

[0150] (7) The thermal stability of the PBA system obtained in step (1) of Example 1, Example 5 and Example 6 was tested. The results are as follows: Figure 7 shown.

[0151] Figure 7 The thermogravimetric performance comparison diagram of the gel electrolyte PBA-Base system, PBA-0.08g SiO2 system and PBA-0.1gSiO2 system of the present invention is shown. As can be seen from the figure, with the addition of silica aerogel, the mass loss rate and mass loss percentage of the electrolyte at high temperature are reduced, indicating an improvement in thermal stability.

[0152] From the above test results we can see that:

[0153] (1) Compared with the PBA-Base system, the gel electrolyte with silica aerogel filler added in the present invention utilizes the high porosity and large internal surface area of ​​the aerogel to provide a large and continuous adsorption surface for lithium ions, forming the characteristics of lithium-rich channels. By assembling Li||LFP811 batteries with different electrolyte systems and conducting long cycle tests and rate performance tests at 4.2V, it was found that the capacity of the battery of the PBA-Base system began to decay significantly after about 10 cycles, while the PBA-0.08g SiO2 and PBA-0.1g SiO2 systems were able to cycle more stably; the rate performance of the PBA-0.08g SiO2 and PBA-0.1g SiO2 systems was significantly better than that of the PBA-Base system. This shows that the addition of silica not only significantly improves the ionic conductivity of the electrolyte, but also enhances the rate performance and cycle stability of the battery.

[0154] (2) Compared with the PBA-Base system, the gel electrolyte system of the present invention can improve the thermal stability of the electrolyte itself. By performing thermogravimetric analysis on the PBA-Base, PBA-0.08g SiO2 and PBA-0.1g SiO2 systems, it was found that the higher the silica aerogel content of the system, the better the thermal stability.

[0155] (3) Compared with the traditional synthesis of polymer electrolytes, the present invention adopts an in-situ synthesis method to achieve complete polymerization of the electrolyte, which can greatly improve the contact between the electrolyte and the positive and negative electrodes, thereby reducing the interface impedance.

[0156] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A gel electrolyte for preparing a gel polymer electrolyte after in-situ polymerization, characterized in that: include: An electrolyte, a polymer matrix and an inorganic filler, wherein the electrolyte comprises a lithium salt and a solvent; Wherein, the polymer matrix comprises acrylic monomers, photoinitiators, crosslinking agents and thermal initiators; The inorganic filler is silicon dioxide aerogel; the mass ratio of the inorganic filler to the acrylic acid monomer is (0-14):

100.

2. The gel electrolyte according to claim 1, characterized in that The mass ratio of the inorganic filler to the acrylic monomer is (8-10):

100.

3. The gel electrolyte according to claim 1, characterized in that In the polymer matrix, the mass ratio of the acrylic monomer, the photoinitiator, the crosslinking agent and the thermal initiator is 1:(0.01-0.03):(0.01-0.03):(0.01-0.03).

4. The gel electrolyte according to claim 1 or 3, characterized in that: The acrylic acid monomer is butyl acrylate; And / or, the photoinitiator is 2-hydroxy-2-methylpropiophenone; And / or, the cross-linking agent is ethylene glycol dimethacrylate; And / or, the thermal initiator is azobisisobutyronitrile.

5. The gel electrolyte according to claim 1, characterized in that: The mass ratio of the electrolyte to the acrylic acid monomer is (0.8-1.2):1; And / or, the lithium salt is selected from at least one of LiPF6 and LiTFSI; and / or, the concentration of the lithium salt in the electrolyte is 0.8 mol / L-1.2 mol / L; And / or, the solvent is selected from at least one of ethylene carbonate and diethyl carbonate.

6. The gel electrolyte according to claim 5, characterized in that The solvent includes ethylene carbonate and diethyl carbonate, and the mass ratio of ethylene carbonate to diethyl carbonate is 1:(0.8-1.2).

7. A method for preparing a gel polymer electrolyte, characterized in that: include: Immersing the separator in the gel electrolyte according to any one of claims 1 to 6, and polymerizing under ultraviolet irradiation to obtain a prepolymerized modified separator; The prepolymerized modified separator is assembled into a lithium battery and then heated for polymerization.

8. The preparation method according to claim 7, characterized in that: First, the separator is immersed in the gel electrolyte for 10 seconds to 3 minutes, and then irradiated with ultraviolet light for 15 minutes to 60 minutes to obtain the prepolymerized modified separator; And / or, the separator is selected from at least one of a glass fiber separator, a polypropylene separator and a non-woven fabric separator.

9. The preparation method according to claim 7, characterized in that: During the heating polymerization process, the polymerization temperature is controlled to be 55°C-65°C, and the polymerization time is 20min-60min; And / or, assembling the prepolymer modified separator, the positive electrode, the negative electrode and the electrolyte into a lithium battery.

10. A lithium battery having a gel polymer electrolyte, characterized in that: It is prepared by the preparation method described in any one of claims 7 to 9.

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