Preparation method of composite gel electrolyte and composite gel electrolyte

Abstract

The invention discloses a preparation method of a composite gel electrolyte and the composite gel electrolyte. The preparation method comprises the following steps: modifying an inorganic oxide, preparing a gel precursor solution, and preparing an organic-inorganic composite gel electrolyte. Epoxy groups are grafted on the surfaces of modified inorganic particles, and the modified inorganic particles serve as hybridization centers to participate in ring-opening polymerization reaction and are combined with polymer molecules to form a cross-linked network, so that the orderliness of polymer chain segments is destroyed, the crystallinity is reduced, a new ion transmission path is provided, particle dispersion and agglomeration are reduced, and the ionic conductivity of electrolyte is promoted to be improved. According to the selected polymerization mode, the common Lewis acid lithium salt in the electrolyte is used as an initiator, additional introduction of the initiator and heating are not needed, and adverse effects such as initiator residue and decomposition gas production can be effectively avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and more specifically, to a preparation method of a composite gel electrolyte and the composite gel electrolyte. Background Art

[0002] In recent years, the rapid development of electric transportation and energy storage industries has also brought about a boom in the development of new energy industries represented by lithium-ion batteries, and the market has also put forward higher performance requirements for existing batteries. Therefore, traditional liquid lithium-ion batteries have been difficult to meet the growing demand for high energy density, high safety performance, and wide temperature range. The development of solid electrolytes is already a general trend. Polymer electrolytes have good flexibility, but they are still lacking in room temperature ionic conductivity; while inorganic solid electrolytes can show better ionic conductivity, but they also create new problems in the interface contact with the electrode. Solid electrolytes of a single nature always have obvious shortcomings, so it is necessary to develop composite electrolytes to achieve a comprehensive improvement in overall performance. On the other hand, most of the gel electrolytes currently studied and prepared are thermally polymerized, which will increase the manufacturing process of the battery. At the same time, the added initiator is prone to produce gas during the heating polymerization process, and the residual initiator will also bring hidden dangers to the performance of the battery.

[0003] Organic / inorganic composite electrolytes are an effective compromise strategy. Prior art 1 (publication number CN105938916A, application date 2016.6.1) uses nano-TiO2 to dope and modify polymer gel electrolytes, which improves the stability and ionic conductivity of gel electrolytes. However, the TiO2 particles used are not modified and have poor affinity. Direct doping and blending lead to a decrease in the film-forming property of polymer electrolytes. The in-situ polymerization method of polymer gel electrolytes can improve the disadvantages of poor interface contact. However, most of the existing work adopts thermal polymerization / photopolymerization, which requires the additional introduction of thermal / photoinitiators. The deterioration of battery performance by residual initiators has always been a problem that has plagued the industry. And they need to be cured by heating or ultraviolet light, which undoubtedly complicates the production process of the battery. Prior art 2 (publication number CN117613365A, application date 2023.12.1) designed an in-situ cross-linked organic-inorganic composite solid electrolyte, and added active nanoparticles to plasticize the polymer, but also did not improve the binding effect between the nanoparticles and the polymer molecules. The nanoparticles will settle on the surface of the positive electrode instead of being evenly dispersed in the polymer matrix, and the polymer precursor used is vinylene carbonate, which still requires the addition of an initiator for heating and polymerization.

[0004] Therefore, there is an urgent need to provide a more efficient and harmless polymerization method and a more effective electrolyte composite method. Summary of the invention

[0005] In view of this, the present invention provides a preparation method of a composite gel electrolyte and a composite gel electrolyte that do not require additional initiator introduction and have milder initiation conditions.

[0006] On the one hand, the present invention provides a preparation method of a composite gel electrolyte, including:

[0007] Modifying the inorganic oxide, including: mixing a coupling agent, a first organic solvent, deionized water and inorganic oxide powder and then dispersing them. Among them, the coupling agent has a bifunctional group, one end reacts with the inorganic substance, and the other end reacts with the organic substance. Heating and stirring the dispersed inorganic oxide slurry, centrifuging, washing and drying after sufficient reaction to obtain modified inorganic oxide powder;

[0008] Preparing a gel precursor solution, including: adding an epoxy monomer and a lithium salt to a second organic solvent to obtain a matrix solution, and adding the modified inorganic oxide powder to the mixed matrix solution for blending and uniformly dispersing to obtain the gel precursor solution;

[0009] Preparing an organic-inorganic composite gel electrolyte, including: injecting the gel precursor solution into a soft-pack battery and standing at room temperature, so that the gel precursor solution undergoes in-situ polymerization inside the battery to obtain an organic-inorganic composite gel electrolyte.

[0010] Optionally, the inorganic oxide is at least one of titanium dioxide, silicon dioxide, aluminum oxide, zirconium oxide, lithium titanium aluminum phosphate, lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium lanthanum zirconium titanium oxide.

[0011] Optionally, the coupling agent includes a silane coupling agent, and the first organic solvent includes absolute ethanol.

[0012] Optionally, the silane coupling agent is at least one of 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, dimethoxy(3-glycidoxypropyl)methylsilane, diethoxy(3-glycidoxypropyl)methylsilane.

[0013] Optionally, the modification of the inorganic oxide includes:

[0014] Placing the inorganic oxide powder in a vacuum drying oven at 60°C to 90°C for drying treatment for 8h to 24h;

[0015] Mixing the silane coupling agent, absolute ethanol, deionized water and inorganic oxide powder and then performing ultrasonic dispersion. The dispersed inorganic oxide slurry continues to be heated and stirred at 45°C to 80°C for 2h to 6h to obtain a mixed solution. After sufficient reaction, the mixed solution is centrifuged, washed and dried to obtain modified inorganic oxide powder.

[0016] Optionally, the epoxy monomer is at least one of ethylene oxide, epichlorohydrin, tetrahydrofuran, 1,3-dioxolane, 1,3-dioxane, 1,3-dioxepane, 1,3,5-trioxane, maleic anhydride, succinic anhydride, glutaric anhydride, pentaerythritol glycidyl ether, trimethylolpropane triglycidyl ether, etc.

[0017] Optionally, the lithium salt is at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide.

[0018] Optionally, the second organic solvent is at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, vinylene carbonate.

[0019] Optionally, the preparation of the organic-inorganic composite gel electrolyte is allowed to stand at room temperature for 12 h to 48 h.

[0020] On the other hand, the present invention also provides an application of an in-situ polymerized organic-inorganic composite gel electrolyte in a lithium battery, and the organic-inorganic composite gel electrolyte is prepared by the above preparation method.

[0021] Compared with the prior art, the preparation method of the composite gel electrolyte and the composite gel electrolyte provided by the present invention at least achieve the following beneficial effects:

[0022] The polymerization method selected in the present invention uses a commonly used Lewis acid lithium salt in the electrolyte as an initiator, without the need to additionally introduce an initiator and heating, which can effectively avoid adverse effects such as initiator residue and gas generation by decomposition; in addition, the Lewis acid sites in the inorganic oxide also play a role in initiating the ring-opening polymerization of the epoxy monomer, further improving the polymerization conversion rate of the monomer.

[0023] After modification in the present invention, the surface of the inorganic particles is grafted with epoxy groups, which can participate in the ring-opening polymerization reaction as a hybridization center, combine with polymer molecules to form a cross-linked network, destroy the order of polymer segments, reduce the crystallinity, and provide new ion transport paths, reduce particle dispersion and agglomeration, and promote the improvement of the ionic conductivity of the electrolyte.

[0024] The rigid inorganic oxide filler in the present invention is beneficial to enhancing the mechanical strength of the polymer electrolyte and the electrode / electrolyte interface, and improving the comprehensive mechanical properties of the gel electrolyte.

[0025] Of course, it is not necessary for any product implementing the present invention to simultaneously achieve all the above-mentioned technical effects.

[0026] Through the following detailed description of the exemplary embodiments of the present invention with reference to the accompanying drawings, other features and advantages of the present invention will become clear. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings incorporated in and forming a part of this specification illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0028] Figure 1 It is a flowchart of the preparation method of the composite gel electrolyte provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] Various exemplary embodiments of the present invention will now be described in detail with reference to the drawings. It should be noted that: unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions and values set forth in these embodiments do not limit the scope of the present invention.

[0030] The following description of at least one exemplary embodiment is merely illustrative in nature and in no way serves as a limitation on the present invention, its application or use.

[0031] Technologies, methods and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such technologies, methods and devices should be regarded as part of the specification.

[0032] In all examples shown and discussed herein, any specific values should be construed as merely exemplary and not as a limitation. Thus, other examples of the exemplary embodiments may have different values.

[0033] It should be noted that: like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0034] Combined with Figure 1 , Figure 1 is a flowchart of the preparation method of the composite gel electrolyte provided by the present invention. The preparation method includes the following steps:

[0035] S1. Modify the inorganic oxide, including: mixing a coupling agent, a first organic solvent, deionized water and inorganic oxide powder for dispersion. The coupling agent has a bifunctional group, one end reacts with the inorganic substance and the other end reacts with the organic substance. Heat and stir the dispersed inorganic oxide slurry, and after sufficient reaction, centrifuge, wash and dry to obtain modified inorganic oxide powder;

[0036] S2. Prepare a gel precursor solution, including: adding an epoxy monomer and a lithium salt to a second organic solvent to obtain a matrix solution, and adding the modified inorganic oxide powder to the mixed matrix solution for blending and uniform dispersion to obtain a gel precursor solution;

[0037] S3. Prepare an organic-inorganic composite gel electrolyte, including: injecting a gel precursor solution into a soft-pack battery and standing at room temperature to enable in-situ polymerization of the gel precursor solution inside the battery, thereby obtaining the organic-inorganic composite gel electrolyte.

[0038] Specifically, for S1, the present invention modifies inorganic oxides with a coupling agent. The coupling agent has a bifunctional group. One end reacts with the inorganic substance, and the other end reacts with the organic substance, enabling the coupling agent to act as a "molecular bridge" to connect the inorganic and organic substances and improve the interfacial compatibility between them. The first organic solvent is used to dissolve or disperse the coupling agent and assist in the dispersion of the inorganic oxide powder. Deionized water is used to adjust the pH value of the solution, promote the hydrolysis of the coupling agent, and assist in the dispersion of the inorganic oxide powder. The inorganic oxide powder is the target material to be modified.

[0039] Mix the coupling agent, the first organic solvent, and deionized water in a certain proportion and stir well to promote the hydrolysis and dispersion of the coupling agent. Add the inorganic oxide powder to the above mixture and promote the dispersion of the powder by means such as ultrasonic treatment, stirring, or ball milling to form a uniform slurry. Heat and stir the dispersed inorganic oxide slurry to promote the reaction between the coupling agent and the surface of the inorganic oxide powder. The heating temperature and time should be determined according to the type of the coupling agent and the properties of the inorganic oxide powder. During the heating and stirring process, one end of the coupling agent reacts with functional groups such as hydroxyl groups on the surface of the inorganic oxide powder to form chemical bonding; the other end remains active and waits to react with the organic substance.

[0040] Optionally, the dosage of the silane coupling agent can be between 5 wt.% and 20 wt.%, such as 5 wt.%, 8 wt.%, 10 wt.%, 12 wt.%, 15 wt.%, or 20 wt.%. The mass of the inorganic oxide is between 0.5 wt.% and 5 wt.%, such as 0.5 wt.%, 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, 5 wt.%. Optionally, the volume ratio of absolute ethanol to deionized water is 7:3, the dosage of the silane coupling agent is 12.5 wt.% of absolute ethanol / deionized water, and the mass ratio of the inorganic oxide is 1.25 wt.%.

[0041] After the reaction is completed, the solid and liquid in the slurry are separated by centrifugation. The centrifuged solid is washed with an appropriate amount of solvent (such as ethanol or water) to remove the unreacted coupling agent and other impurities. The washed solid is dried to obtain the modified inorganic oxide powder. The drying temperature and time are determined according to the properties of the inorganic oxide powder to avoid structural damage or agglomeration caused by high temperature. After being modified with the coupling agent, the surface properties of the inorganic oxide powder are changed, and its compatibility and interfacial bonding force with organic substances are improved. The inorganic oxide filler is pre-epoxidized and grafted, and can open the ring and combine with the epoxy monomer in the organic matrix solution to form a more stable and favorable hybrid cross-linked structure.

[0042] In addition, the inorganic oxide raw material of the present invention exhibits Lewis acidity and can provide active sites for initiating the ring-opening polymerization of epoxy monomers; due to their own properties, the selected inorganic oxide raw materials all have hydroxyl groups on the surface, which is unfavorable for the performance of the battery. Therefore, through grafting functional groups, the surface hydroxyl groups can be removed and new epoxy groups can be introduced during the modification process.

[0043] In addition, the rigid inorganic oxide filler is beneficial to enhancing the mechanical strength of the polymer electrolyte and the electrode / electrolyte interface, and improving the comprehensive mechanical properties of the gel electrolyte.

[0044] The present invention introduces inorganic fillers into the polymer electrolyte to form an organic / inorganic composite electrolyte to enhance the mechanical properties and ion transport ability.

[0045] For S2, the epoxy monomer is the main component of the gel precursor solution, and the lithium salt provides lithium ions and affects the electrochemical performance of the gel. The organic solvent dissolves the epoxy monomer and the lithium salt. The modified inorganic oxide powder has good dispersibility and compatibility with the organic matrix. Parameters such as stirring time, temperature, and speed should be determined according to the properties of the epoxy monomer, lithium salt, and solvent to obtain a uniform matrix solution. Generally, the stirring temperature is controlled at room temperature or slightly higher, and the stirring time is sufficient to completely dissolve and mix all components evenly.

[0046] The mass fraction of the epoxy monomer relative to the total electrolyte can be 3 wt.% to 20 wt.%, and optionally, it can be 3 wt.%, 5 wt.%, 8 wt.%, 10 wt.%, 12 wt.%, 15 wt.%, 20 wt.%. Among them, in the examples, the mass fractions of the selected epoxy monomers relative to the total electrolyte are 5 wt.% and 10 wt.%, and the lithium salt concentration is fixed at 1 mol / L. The mass fraction of the modified inorganic oxide powder relative to the epoxy monomer is 1 wt.% to 8 wt.%, for example, it can be 1 wt.%, 2 wt.%, 4 wt.%, 8 wt.%.

[0047] The modified inorganic oxide powder is gradually added to the matrix solution at a certain ratio, and the addition process should be carried out slowly to avoid powder agglomeration and excessive local concentration. In the process of dispersion and mixing, equipment such as a high-speed stirrer, an ultrasonic disperser, or a ball mill is used to disperse the powder evenly in the matrix solution. The dispersion time and intensity should be determined according to the particle size of the powder, the viscosity of the matrix solution, and the required dispersion effect. After sufficient dispersion and mixing, the epoxy monomer, lithium salt, organic solvent, and modified inorganic oxide powder together form a uniform gel precursor solution, which has a certain viscosity and fluidity and provides a basis for the preparation of the subsequent gel electrolyte.

[0048] For S3, epoxy groups are grafted onto the surface of the modified inorganic oxide, which can participate in the ring-opening polymerization reaction as a hybridization center, combine with polymer molecules to form a cross-linked network, disrupt the order of polymer segments, reduce the crystallinity, and provide new ion transport paths, reduce particle dispersion and agglomeration, and promote the improvement of the ionic conductivity of the electrolyte.

[0049] The oxygen atom with a lone pair of electrons in the epoxy structure is attacked by the lewis acidic ion with strong electron-attracting ability, resulting in a ring-opening reaction, and then chain growth occurs to form a polymer. The general chemical reaction formula is as follows:

[0050]

[0051] In the formula, R 1 , R 2 can be an alkylene group or other groups and segments with any structure. The structural expressions of the epoxy monomer and modified inorganic particles selected in the present invention all conform to this general formula, and A + B - represents an initiator.

[0052] The polymerization method selected in the present invention can use the commonly used Lewis acid (lewis) lithium salt in the electrolyte as an initiator, without the need to introduce additional initiators and heating, which can effectively avoid adverse effects such as initiator residue and gas generation due to decomposition. Moreover, the operation process is simple and highly compatible with the existing liquid battery injection process.

[0053] Of course, the Lewis acid sites in the inorganic oxide can also play a role in initiating the ring-opening polymerization of the epoxy monomer, further improving the polymerization conversion rate of the monomer.

[0054] It should be noted that the basic definition of a Lewis acid is a substance that can accept electrons. There are two types of Lewis acid sites in inorganic oxides. One is the surface metal cation, which has Lewis acidity because it has the ability to adsorb anions; the other is the oxygen vacancy formed by the jump of oxygen ions between the lattices. Taking titanium dioxide as an example, the position where titanium ions are located is a Lewis acid site, and the oxygen vacancy is also a Lewis acid site.

[0055] Optionally, the inorganic oxide may be titanium dioxide (TiO 2 ), silicon dioxide (SiO 2 ), aluminum oxide (Al 2 O 3 ), zirconium oxide (ZrO 2 ), lithium aluminum titanium phosphate (LATP), lithium lanthanum zirconium oxide (LLZO), lithium lanthanum titanium oxide (LLTO), lithium lanthanum zirconium titanium oxide (LLZTO), or at least one of them.

[0056] Titanium dioxide (TiO 2 ) has a high melting point, high gloss, and hardness, and has the best opacity, best whiteness and brightness, and semiconductor properties. Silicon dioxide (SiO 2 ) has high fire resistance, high temperature resistance, a small coefficient of thermal expansion, high insulation, corrosion resistance, and other characteristics. Aluminum oxide (Al 2 O 3 ) has high hardness, high melting point, good chemical stability, insulation, and adsorption. Zirconium oxide (ZrO 2 ) has excellent properties such as high hardness, high strength, high toughness, wear resistance, corrosion resistance, and high temperature resistance. It is a good electrical insulator at room temperature, and oxygen ions have a high mobility at high temperatures, showing good oxygen ion conductivity. Lithium aluminum titanium phosphate (LATP) has good chemical stability, high room temperature ionic conductivity, safety and reliability, good mechanical properties, and low internal resistance. Lithium lanthanum zirconium oxide (LLZO) is a solid electrolyte material with high ionic conductivity, high electrochemical stability, and good chemical stability to the cathode material and lithium metal anode. Lithium lanthanum titanium oxide is a compound composed of lithium, lanthanum, titanium, and oxygen elements, and can be used as a cathode material for the manufacture of lithium-ion batteries. Lithium lanthanum zirconium titanium oxide is a solid electrolyte material with excellent properties or used in other high-performance electronic devices. Using inorganic oxides such as titanium dioxide, silicon dioxide, aluminum oxide, zirconium oxide, lithium aluminum titanium phosphate, lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, and lithium lanthanum zirconium titanium oxide in the modification can significantly improve the physical properties, chemical stability, electrical properties, and economic benefits of the material.

[0057] Optionally, the coupling agent includes a silane coupling agent, and the first organic solvent includes absolute ethanol.

[0058] Silane coupling agent is a compound with a special structure. Its molecule contains both a silane part that can react with inorganic materials and an organic functional group part that can react with organic materials. The silane coupling agent can connect inorganic oxides and organic materials like a bridge, making the combination between the two closer. Through the modification of the silane coupling agent, the dispersibility and compatibility of inorganic oxides in organic materials can be improved, thereby enhancing the overall performance of the composite material. The addition of the silane coupling agent can enhance the mechanical strength, heat resistance, aging resistance and other properties of the composite material.

[0059] Absolute ethanol can dissolve the silane coupling agent well, enabling it to be evenly dispersed on the surface of inorganic oxides, which is conducive to the full reaction of the silane coupling agent with inorganic oxides. The addition of absolute ethanol can promote the reaction between the silane coupling agent and inorganic oxides, making the reaction more sufficient and uniform.

[0060] The dosage of absolute ethanol needs to be controlled within a certain range. Too much or too little may affect the modification effect. Excessive absolute ethanol may lead to uneven distribution of the silane coupling agent on the surface of inorganic oxides, while too little may not be able to dissolve the silane coupling agent sufficiently.

[0061] Optionally, the silane coupling agent is at least one of 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, dimethoxy(3-glycidoxypropyl)methylsilane, and diethoxy(3-glycidoxypropyl)methylsilane.

[0062] The glycidyl groups in these silane coupling agents can react with functional groups such as hydroxyl groups on the surface of inorganic oxides to form chemical bond binding, thereby improving the interfacial binding force between inorganic oxides and organic materials and significantly enhancing the modification effect.

[0063] Optionally, the modification of inorganic oxides includes:

[0064] Put the inorganic oxide powder in a vacuum drying oven at 60°C to 90°C and carry out drying treatment for 8h to 24h;

[0065] Mix the silane coupling agent, absolute ethanol, deionized water and the inorganic oxide powder and then carry out ultrasonic dispersion. The well-dispersed inorganic oxide slurry is continuously heated and stirred at 45°C to 80°C for 2h to 6h to obtain a mixed solution. After full reaction, the mixed solution is centrifuged, washed and dried to obtain the modified inorganic oxide powder.

[0066] The inorganic oxide powder is placed in a vacuum drying oven at 60°C to 90°C and dried for 8h to 24h to ensure that the moisture in the powder is completely removed.

[0067] Modify the inorganic oxide. The heating temperature can be 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, or any value between 45°C and 80°C. The heating and stirring time can be 2h, 3h, 4h, 5h, 6h, or any value between 2h and 6h. The heating temperature range and stirring time within this range can ensure that the silane coupling agent reacts fully with the inorganic oxide powder.

[0068] Optionally, the epoxy monomer is at least one of ethylene oxide, epichlorohydrin, tetrahydrofuran, 1,3-dioxolane, 1,3-dioxane, 1,3-dioxepane, 1,3,5-trioxane, maleic anhydride, succinic anhydride, glutaric anhydride, pentaerythritol glycidyl ether, and trimethylolpropane triglycidyl ether.

[0069] Ethylene oxide, epichlorohydrin, tetrahydrofuran, 1,3-dioxolane, 1,3-dioxane, 1,3-dioxepane, 1,3,5-trioxane, maleic anhydride, succinic anhydride, glutaric anhydride, pentaerythritol glycidyl ether, and trimethylolpropane triglycidyl ether all have excellent insulation properties and adhesion capabilities and can all be used as the main components of the gel precursor solution.

[0070] Optionally, the lithium salt is at least one of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium tetrafluoroborate (LiBF4), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium perchlorate (LiClO4), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0071] Lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium tetrafluoroborate (LiBF4), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium perchlorate (LiClO4), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) are all lithium salts of Lewis acids and can be used as initiators. Without the need to introduce additional initiators and heating, they can effectively avoid adverse effects such as initiator residue and gas generation due to decomposition. Of course, as lithium salts, they have high stability and can endow lithium-ion batteries with good long-term cycling performance.

[0072] Optionally, the second organic solvent is at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and vinylene carbonate.

[0073] These organic solvents have good solubility and can dissolve the epoxy monomer and the crosslinking agent.

[0074] Optionally, during the preparation of the organic-inorganic composite gel electrolyte, it is left to stand at room temperature for 12h to 48h.

[0075] For example, it can be left standing at room temperature for 12 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h, 45 h, 48 h, or any value between 12 h and 48 h, which can ensure that the gel precursor solution is fully infiltrated and diffused inside the battery, promoting the in-situ polymerization reaction between the organic polymer and the inorganic additive in the gel precursor solution to form an organic-inorganic composite gel electrolyte with excellent performance and stability.

[0076] On the other hand, the present invention also provides an application of the in-situ polymerized organic-inorganic composite gel electrolyte in a lithium battery, and the in-situ polymerized organic-inorganic composite gel electrolyte is prepared by the above preparation method.

[0077] Of course, in addition to the organic-inorganic composite gel electrolyte, the lithium battery also has components such as a positive electrode, a negative electrode, and a separator. In the present invention, the electrolyte is replaced by the organic-inorganic composite gel electrolyte. The lithium battery has the beneficial effects of the above preparation method, which will not be elaborated here.

[0078] Example 1:

[0079] Step 1: First, take 0.5 g of nano-TiO 2 powder, place it in a vacuum drying oven at 80 °C and dry it for 12 h for later use. Prepare a 40 mL anhydrous ethanol / deionized water mixed solution according to a volume ratio of 7:3, and then add the dried TiO 2 powder and 50 mg of 3-glycidoxypropyltrimethoxysilane thereto, and perform ultrasonic dispersion for 30 min for sufficient hydrolysis. Transfer the dispersed TiO 2 slurry to a three-necked flask, heat it to 60 °C and carry out heating and stirring reaction for 4 h. After the reaction is completed and the three-necked flask is cooled, centrifuge the mixed solution, wash it with anhydrous ethanol, and dry it to obtain the modified nano-TiO 2 powder.

[0080] Step 2: Weigh 7.96 g of lithium hexafluorophosphate and add it to 50 mL of a mixed solvent of ethylene carbonate (EC) / dimethyl carbonate (DMC) (volume ratio of 1:1). After stirring until the lithium salt is completely dissolved, add 7.53 g of 1,3-dioxolane and continue to stir and mix evenly. Subsequently, add 0.151 g of the modified nano-TiO 2 powder, and stir and disperse it evenly to obtain a gel precursor solution.

[0081] Step 3: Inject the gel precursor solution into the soft-pack battery according to the injection process of conventional liquid electrolytes. The positive electrode plate of the soft-pack battery is prepared by mixing nickel cobalt manganese ternary material, binder polyvinylidene fluoride, and conductive agent carbon black in a certain proportion. The negative electrode plate is prepared by mixing silicon-carbon material, binder styrene-butadiene rubber, and conductive agent carbon nanotube in a certain proportion. The positive and negative electrode plates and the separator are combined into a soft-pack battery through the stacking process. After the injection is completed, vacuum sealing is carried out, and it is left standing at room temperature for 48 h to allow the gel precursor solution to fully infiltrate the battery core and undergo in-situ polymerization to form an in-situ polymerized organic / inorganic composite gel electrolyte.

[0082] Example 2:

[0083] The method of this example is the same as that of Example 1, except that the addition amounts of 1,3-dioxolane and nano-TiO 2 powder are 3.54 g and 0.035 g, respectively.

[0084] Example 3:

[0085] The method of this example is the same as that of Example 1, except that the addition amount of nano-TiO 2 powder is 0.075 g.

[0086] Example 4:

[0087] The method of this example is the same as that of Example 1, except that the addition amount of nano-TiO 2 powder is 0.301 g.

[0088] Example 5:

[0089] The method of this example is the same as that of Example 1, except that the addition amount of nano-TiO 2 powder is 0.602 g.

[0090] Example 6:

[0091] The method of this example is the same as that of Example 1, except that the added modified inorganic oxide powder is nano-Al 2 O 3 .

[0092] Example 7:

[0093] The method of this example is the same as that of Example 1, except that the added modified inorganic oxide powder is nano-LATP.

[0094] Comparative Example 1:

[0095] This example is for the preparation of a single polymer gel electrolyte, which is different from Example 1 in that no inorganic oxide powder is added.

[0096] Comparative Example 2:

[0097] Compared with Example 1, the difference in this example is that the TiO used 2 was directly added to the mixed solvent containing the gel monomer without being treated by silane modification.

[0098] Various performance tests were carried out on the above examples and comparative examples, and the results are shown in Table 1.

[0099] Table 1: Performance test results of each example and comparative example

[0100]

[0101] It can be seen from Example 1 and Comparative Example 1 that the introduction of inorganic oxides can significantly improve the ionic conductivity of the gel electrolyte and reduce the internal resistance of the battery. This is because the inorganic oxides themselves can promote the ring-opening polymerization of epoxy monomers as Lewis acids, improving the polymerization conversion rate. Even for the inorganic fillers introduced by a simple blending method (Comparative Example 2), it can also play a certain role in reducing the crystallinity of the polymer electrolyte and increasing the ionic conductivity. The rigid inorganic fillers can effectively enhance the polymer matrix and the electrode / electrolyte interface, thus improving the cycle performance of the battery.

[0102] Compared with Comparative Example 2, after being treated by silane modification in Example 1, epoxy groups are grafted onto the surface of the inorganic oxide particles, which can participate in the ring-opening polymerization reaction as a hybridization center and combine with polymer molecules to form a more stable cross-linked network. While realizing the improvement of the mechanical strength and ionic conductivity of the organic / inorganic composite electrolyte, it also shows better lipophilicity, which is beneficial to the uniform dispersion of inorganic powder in the electrolyte and reduces the interfacial impedance. The addition ratio of inorganic oxides also has an obvious influence on the performance of the composite gel electrolyte. Excessive addition of inorganic fillers in Example 4 and Example 5 may lead to uneven dispersion of particles in the matrix and agglomeration, increasing the interfacial impedance. While too little addition of inorganic fillers will also result in insufficient hybridization cross-linking strength of the composite gel electrolyte and a decline in the long-term stability of battery cycling.

[0103] It can be seen from the test results of Example 1, Example 6, and Example 7 that by selecting different types of inorganic oxides for modification and combination, the comprehensive performance of the composite gel electrolyte can be effectively improved, indicating that the organic / inorganic composite gel electrolyte preparation technology adopted in the present invention has relatively general applicability.

[0104] Although some specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are only for illustration and not for limiting the scope of the present invention. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A method for preparing a composite gel electrolyte, characterized in that: include: Modifying the inorganic oxide, comprising: mixing a coupling agent, a first organic solvent, and deionized water with inorganic oxide powder and dispersing the mixture, wherein the coupling agent has a bifunctional group, one end of which reacts with inorganic matter and the other end of which reacts with organic matter, heating and stirring the dispersed inorganic oxide slurry, centrifuging, washing, and drying the mixture after sufficient reaction to obtain modified inorganic oxide powder; Preparing a gel precursor solution, comprising: adding epoxy monomer and lithium salt into a second organic solvent to obtain a matrix solution, adding the modified inorganic oxide powder into the mixed matrix solution, blending and dispersing the mixture evenly to obtain the gel precursor solution; The method for preparing an organic-inorganic composite gel electrolyte comprises: injecting the gel precursor solution into a soft-pack battery, and standing the battery at room temperature so that the gel precursor solution undergoes in-situ polymerization inside the battery to obtain an organic-inorganic composite gel electrolyte.

2. The method for preparing the composite gel electrolyte according to claim 1, characterized in that: The amount of the inorganic oxide is 0.5wt.% to 5wt.%, and the inorganic oxide is at least one of titanium dioxide, silicon dioxide, aluminum oxide, zirconium oxide, lithium aluminum titanium phosphate, lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, and lithium lanthanum zirconium titanium oxide.

3. The method for preparing the composite gel electrolyte according to claim 1, characterized in that: The coupling agent includes a silane coupling agent, the amount of the silane coupling agent is 5wt.% to 20wt.%, and the first organic solvent includes anhydrous ethanol.

4. The method for preparing the composite gel electrolyte according to claim 3, characterized in that: The silane coupling agent is at least one of 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, dimethoxy(3-glycidyloxypropyl)methylsilane and diethoxy(3-glycidyloxypropyl)methylsilane.

5. The method for preparing the composite gel electrolyte according to claim 3, characterized in that: The inorganic oxide is modified, comprising: The inorganic oxide powder is vacuum dried at 60°C to 90°C for 8h to 24h; The silane coupling agent, anhydrous ethanol, deionized water and inorganic oxide powder are mixed and ultrasonically dispersed. The dispersed inorganic oxide slurry is further heated and stirred at 45°C to 80°C for 2h to 6h to obtain a mixed solution. After sufficient reaction, the mixed solution is centrifuged, washed and dried to obtain modified inorganic oxide powder.

6. The method for preparing the composite gel electrolyte according to claim 1, characterized in that: The epoxy monomer is at least one of ethylene oxide, epichlorohydrin, tetrahydrofuran, 1,3-dioxolane, 1,3-dioxane, 1,3-dioxepane, 1,3,5-trioxane, maleic anhydride, succinic anhydride, glutaric anhydride, pentaerythritol glycidyl ether, trimethylolpropane triglycidyl ether, etc.; the mass fraction of the epoxy monomer relative to the total electrolyte is 3wt.% to 20wt.%.

7. The method for preparing the composite gel electrolyte according to claim 1, characterized in that: The lithium salt is at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium perchlorate, and lithium bis(trifluoromethanesulfonyl)imide.

8. The method for preparing the composite gel electrolyte according to claim 1, characterized in that: The second organic solvent is at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and vinylene carbonate.

9. The method for preparing the composite gel electrolyte according to claim 1, characterized in that: The prepared organic-inorganic composite gel electrolyte is allowed to stand at room temperature for 12 hours to 48 hours.

10. A composite gel electrolyte, characterized in that: The composite gel electrolyte is prepared by the preparation method according to any one of claims 1 to 9.

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