A composite solid electrolyte and preparation method thereof

Abstract

The present invention discloses a composite solid electrolyte and a preparation method thereof, relating to the technical field of secondary batteries. The solid electrolyte is prepared from the following components, measured by weight: 60-80 parts of a PEO matrix, 15-35 parts of a lithium salt, 10-20 parts of a composite modifier, and 3-8 parts of ethoxy(pentafluoro)cyclotriphosphazene. During multiple charge and discharge cycles, the composite solid electrolyte of the present invention can effectively resist interfacial side reactions, maintain stable electrical conductivity and structural integrity, and significantly extend the service life of the battery. At the same time, the electrolyte has good interfacial adaptability, can achieve stable interfacial contact with various positive and negative electrode materials, reduce interfacial impedance, and improve the overall efficiency and reliability of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary batteries, and in particular to a composite solid electrolyte and a preparation method thereof. Background Art

[0002] With the growing global demand for efficient, reliable, and safe energy storage devices, lithium-ion batteries, one of the most widely used battery technologies, have played a vital role in portable electronic devices, electric vehicles, and energy storage systems. However, traditional lithium-ion batteries, primarily using liquid electrolytes, have safety risks such as flammability, leakage, and limited lifespan, which to some extent restrict their wider application.

[0003] In order to solve the above problems, solid electrolytes have received widespread attention as a potential material to replace liquid electrolytes. Compared with liquid electrolytes, solid electrolytes have higher safety, wider electrochemical window and better thermal stability, which can significantly improve the overall performance and service life of the battery. In recent years, the research on solid electrolyte materials has made significant progress, mainly including sulfide, oxide and polymer-based solid electrolytes. However, existing solid electrolytes still face many challenges in terms of ionic conductivity, interface stability and processing technology. For example, the ionic conductivity of some solid electrolyte materials at room temperature is relatively low, which limits their application in high-performance batteries; in addition, the interface compatibility between solid electrolytes and electrode materials is poor, which easily leads to an increase in the internal impedance of the battery, affecting the battery's charge and discharge efficiency and cycle life.

[0004] Solid-state electrolytes are an important component of lithium-ion batteries. Their materials are diverse and can be divided into three categories: sulfide electrolytes, oxide electrolytes, and polymer electrolytes. Each type of material has unique performance advantages and application potential.

[0005] Sulfide electrolytes are known for their high ionic conductivity and good processing properties, and typical representatives include Li 10 GeP2S 12 (LGPS) and Li7P3S 11 (LPS). These materials exhibit excellent lithium ion conductivity at room temperature, typically reaching 10 -3 S / cm or higher, approaching the conductivity level of liquid electrolytes. Furthermore, sulfide electrolytes have low interfacial impedance, facilitating good contact between the electrode and the electrolyte. However, sulfide materials have shortcomings in moisture resistance and chemical stability, and are prone to react with moisture or carbon dioxide in the air, limiting the environmental conditions for their practical application.

[0006] Oxide electrolytes have attracted attention due to their excellent chemical stability and wide electrochemical window. Typical representatives include Li7La3Zr2O12 (LLZO) and Li 1.5 Al 0.5 Ge 1.5 (PO4)3(LAGP). These materials exhibit good stability under high temperature and high voltage conditions and are suitable for the needs of high energy density batteries. Although the ionic conductivity of oxide electrolytes is generally lower than that of sulfide electrolytes, their high mechanical strength helps to inhibit dendrite growth inside the battery and improve safety. However, oxide electrolytes are difficult to process, usually requiring high-temperature sintering, and have poor interface compatibility with certain electrode materials, which increases the complexity of battery manufacturing.

[0007] Polymer electrolytes have become a research hotspot due to their flexibility and processing convenience, with polyethylene oxide (PEO)-based electrolytes being a typical example. The ionic conductivity of polymer electrolytes at room temperature is relatively low, usually around 10 -4 S / cm, but its conductivity can be significantly improved by introducing plasticizers, nanofillers, or cross-linking structures. At the same time, polymer electrolytes have good interfacial compatibility and mechanical flexibility, which helps to achieve a close bond between the electrode and the electrolyte and reduce interfacial impedance.

[0008] CN118136940A discloses a PEO-based solid electrolyte and its preparation method. The PEO-based solid electrolyte is prepared by solution casting using polyethylene oxide as the solid electrolyte matrix, lithium bis(trifluoromethanesulfonylimide) as the lithium salt, and acetonitrile as the solvent. The addition of lithium bis(trifluoromethanesulfonylimide) effectively improves the room-temperature ionic conductivity of the polyethylene oxide-based solid electrolyte. By varying the lithium salt ratio, the electrochemical window of the prepared solid electrolyte membrane can be adjusted.

[0009] However, the thermal stability and long-term cycling stability of polymer electrolytes still need to be further improved to meet the requirements of high-performance batteries. Based on this, the present invention proposes a composite solid-state electrolyte and its preparation method, aiming to improve the overall performance of the electrolyte by optimizing the material combination and preparation process, providing an advanced solution for the development of high-performance solid-state batteries. Summary of the Invention

[0010] In order to address the deficiencies in the prior art, the present invention aims to provide a composite solid electrolyte and a method for preparing the same. During multiple charge and discharge cycles, the composite solid electrolyte of the present invention can effectively resist interfacial side reactions, maintain stable electrical conductivity and structural integrity, and significantly extend the service life of the battery. At the same time, the electrolyte has good interfacial adaptability and can achieve stable interfacial contact with various positive and negative electrode materials, reducing interfacial impedance and improving the overall efficiency and reliability of the battery.

[0011] In order to achieve the above object, the present invention adopts the following technical solutions:

[0012] A composite solid electrolyte is prepared from the following components in parts by weight: 60-80 parts of PEO matrix, 15-35 parts of lithium salt, 10-20 parts of composite modifier, and 3-8 parts of ethoxy (pentafluoro) cyclotriphosphazene.

[0013] Preferably, the preparation method of the composite modifier comprises the following steps:

[0014] (1) Dispersing mesoporous silica and KH570 in anhydrous ethanol, adding triethanolamine, and reflux reaction, filtering the product, washing with alcohol, and drying to obtain pretreated silica;

[0015] Introduction of organic functional groups: Hydroxyl groups (-Si-OH) on the mesoporous silica surface react with the alcohol groups in KH570, undergoing dehydration condensation catalyzed by triethanolamine to form silanol bonds (-Si-O-Si-) and immobilize the KH570 molecules. During this process, the allyl termini of KH570 remain unreacted, becoming active sites for subsequent polymerization reactions. Reflux conditions promote the reaction and ensure sufficient coverage of the silica surface with the coupling agent.

[0016] Preferably, in step (1), the usage ratio of mesoporous silica, KH570, anhydrous ethanol and triethanolamine is 10 g: 0.3-3 g: 50-100 mL: 0.15-1.5 mL.

[0017] Preferably, in step (1), the reflux reaction conditions are 50-80° C. for 2-6 hours.

[0018] (2) Dispersing the pretreated silica in ethyl acetate, ultrasonically treating the silica, then adding hexafluorobutyl acrylate and polyethylene glycol methyl ether acrylate, continuously introducing nitrogen, adding azobisisobutyronitrile, stirring to react, cooling, centrifuging, washing, and drying the product to obtain the composite modifier.

[0019] In-situ free radical polymerization forms the polymer layer: The organic functional groups on the pretreated silica surface initiate the free radical polymerization of hexafluorobutyl acrylate (HFMA) and polyethylene glycol methyl ether acrylate (PEGMEMA), forming a uniform polymer layer. Azobisisobutyronitrile (AIBN) decomposes at a suitable temperature to generate free radicals. These radicals initiate the addition polymerization of monomers from the allyl end of KH570, causing chain growth of HFMA and PEGMEMA on the silica surface, forming a dense and well-connected polymer network.

[0020] Preferably, in step (2), the usage ratio of pretreated silica, ethyl acetate, hexafluorobutyl acrylate, polyethylene glycol methyl ether acrylate, and azobisisobutyronitrile is 10 g: 100-150 mL: 10-15 mL: 15-20 mL: 0.05-0.5 g.

[0021] Preferably, in step (2), the ultrasonic treatment is performed for 10 to 30 minutes; the stirring reaction conditions are 60 to 75° C. and the stirring reaction is performed for 4 to 12 hours; and the product is washed with ethyl acetate 3 to 5 times.

[0022] Preferably, the lithium salt is one or more of lithium perchlorate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium trifluoromethylsulfonate, lithium bis(oxalatoborate), lithium difluorooxalatoborate and lithium chloride.

[0023] The present invention also claims protection for a method for preparing the composite solid electrolyte, comprising the following steps: adding a PEO matrix to a solvent, mixing uniformly, then adding a lithium salt, a composite modifier, and ethoxy(pentafluoro)cyclotriphosphazene, stirring and dispersing uniformly to obtain a casting slurry, casting the slurry into a film, and after the solvent evaporates, obtaining the composite solid electrolyte.

[0024] Preferably, the solvent is one or more of acetonitrile, acetone, DMF, and NMP; and the mass ratio of the PEO matrix to the solvent is 1:5-10.

[0025] Preferably, the stirring and dispersing conditions are 20-80° C. and 1-12 hours.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention provides a composite solid electrolyte. First, the PEO matrix, as the main component, provides excellent mechanical strength and flexibility, ensuring the structural stability and crack resistance of the electrolyte membrane. The addition of lithium salt significantly improves the ionic conductivity of the electrolyte, ensuring the efficient migration of lithium ions, thereby improving the overall performance and charge and discharge efficiency of the battery. The composite modifier improves the compatibility between the PEO matrix and mesoporous silica by grafting polyethylene glycol methyl ether acrylate and hexafluorobutyl acrylate, optimizes the ion migration path, and reduces the crystallinity of PEO, thereby effectively improving the ionic conductivity of the electrolyte. At the same time, the introduction of ethoxy (pentafluoro) cyclotriphosphazene significantly improves the thermal stability and flame retardant properties of the electrolyte, and enhances the safety of the electrolyte in high temperature and high voltage environments. In summary, the composite solid electrolyte of the present invention, while ensuring high ionic conductivity, greatly improves the safety and stability of the material, and is expected to significantly extend the service life of the battery and improve its overall performance.

[0028] 2. The present invention provides a composite modifier, which first uses KH570 to modify mesoporous silica, thereby enhancing the organic compatibility of the mesoporous silica surface and its interaction with the PEO matrix. Subsequently, hexafluorobutyl acrylate and polyethylene glycol methyl ether acrylate are reacted to form a polymer in situ on the surface of the modified mesoporous silica through an addition reaction. This process not only makes the mesoporous silica more evenly dispersed in the PEO matrix and improves the overall uniformity of the electrolyte, but also reduces the crystallinity of PEO through the grafted polyethylene glycol methyl ether acrylate, thereby promoting ion transport. In addition, the polyfluoro groups in the composite modifier provide additional channels for the diffusion of lithium ions, and lithium ions achieve efficient migration through the adsorption and desorption process with the polyfluoro groups. Fluorocarbon groups, as Lewis basic sites, help adsorb and stabilize lithium ions, optimize their migration paths in the electrolyte, improve overall ionic conductivity, and synergistically improve lithium ion conductivity with polyethylene glycol methyl ether acrylate. Furthermore, the rich pore structure of mesoporous silica nanoparticles provides more lithium ion transmission paths, shortening the transmission distance, making the lithium ion flux more uniform, extending the cycle life, and effectively preventing the rapid formation of lithium dendrites. The modified mesoporous silica significantly improves the thermal and electrochemical stability of the polymer solid electrolyte, broadens its application temperature range, slows the degradation of the electrolyte performance, and enhances the mechanical strength of the solid electrolyte, reducing the risk of lithium dendrite penetration. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. Of course, the specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0030] Unless otherwise specified, the chemical reagents and materials in the present invention are purchased from commercial sources or synthesized from commercially purchased raw materials.

[0031] PEO molecular weight 60000Da-8000000Da, purchased from Aladdin Chemical;

[0032] The pore size of mesoporous silica is 2-10nm, the diameter is 100-300nm, and the specific surface area is ≥900m 2 / g, purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.

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

[0034] (1) Dispersing 10 g of mesoporous silica and 0.3-3 g of KH570 in 50-100 mL of anhydrous ethanol, adding 0.15-1.5 mL of triethanolamine, and reacting at 50-80° C. for 2-6 h. Filtering, washing with alcohol, and drying the product to obtain pretreated silica;

[0035] (2) dispersing 10 g of pretreated silica into 100-150 mL of ethyl acetate, ultrasonically treating for 10-30 min, then adding 10-15 mL of hexafluorobutyl acrylate and 15-20 mL of polyethylene glycol methyl ether acrylate, continuously introducing nitrogen, adding 0.05-0.5 g of azobisisobutyronitrile, stirring at 60-75° C. for 4-12 h, cooling the product, centrifuging, washing with ethyl acetate 3-5 times, and drying to obtain the composite modifier;

[0036] (3) Add 60 to 80 parts of PEO matrix to 300 to 800 parts of solvent and mix them evenly. Then add 15 to 35 parts of lithium salt, 10 to 20 parts of composite modifier, and 3 to 8 parts of ethoxy (pentafluoro) cyclotriphosphazene. Stir and disperse at 20 to 80° C. for 1 to 12 hours to obtain a casting slurry. The slurry is cast into a film. After the solvent evaporates, the composite solid electrolyte is obtained.

[0037] The solvent is one or more of acetonitrile, acetone, DMF, and NMP; the lithium salt is one or more of lithium perchlorate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium trifluoromethylsulfonate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, and lithium chloride.

[0038] The present invention will be further described below with reference to specific examples.

[0039] Example 1

[0040] A method for preparing a composite solid electrolyte comprises the following steps:

[0041] (1) Disperse 10 g of mesoporous silica and 3 g of KH570 in 100 mL of anhydrous ethanol, add 1.5 mL of triethanolamine, and reflux at 80 °C for 2 h. Filter the product, wash with alcohol, and dry it to obtain pretreated silica.

[0042] (2) 10 g of pretreated silica was dispersed in 100 mL of ethyl acetate and ultrasonically treated for 30 min. Then, 15 mL of hexafluorobutyl acrylate and 15 mL of polyethylene glycol methyl ether acrylate were added, nitrogen was continuously introduced, 0.5 g of azobisisobutyronitrile was added, and the mixture was stirred at 75° C. for 4 h. The product was cooled, centrifuged, washed three times with ethyl acetate, and dried to obtain the composite modifier.

[0043] (3) 80 g of PEO matrix was added to 400 g of acetonitrile and mixed evenly. Then, 35 g of lithium hexafluorophosphate, 20 g of composite modifier, and 8 g of ethoxy (pentafluoro) cyclotriphosphazene were added and stirred and dispersed at 80° C. for 2 h to obtain a casting slurry. The slurry was cast into a film. After the solvent evaporated, the composite solid electrolyte was obtained.

[0044] Example 2

[0045] A method for preparing a composite solid electrolyte comprises the following steps:

[0046] (1) Disperse 10 g of mesoporous silica and 2 g of KH570 in 100 mL of anhydrous ethanol, add 1.0 mL of triethanolamine, and reflux at 70 °C for 4 h. Filter the product, wash with alcohol, and dry it to obtain pretreated silica.

[0047] (2) 10 g of pretreated silica was dispersed in 100 mL of ethyl acetate, and ultrasonically treated for 20 min. Then, 15 mL of hexafluorobutyl acrylate and 15 mL of polyethylene glycol methyl ether acrylate were added, and nitrogen was continuously introduced. 0.4 g of azobisisobutyronitrile was added, and the mixture was stirred at 70° C. for 6 h. The product was cooled, centrifuged, washed with ethyl acetate three times, and dried to obtain the composite modifier.

[0048] (3) 70 g of PEO matrix was added to 350 g of acetonitrile and mixed evenly. Then, 30 g of lithium hexafluorophosphate, 16 g of composite modifier, and 6 g of ethoxy (pentafluoro) cyclotriphosphazene were added and stirred and dispersed at 60° C. for 6 h to obtain a casting slurry. The slurry was cast into a film. After the solvent evaporated, the composite solid electrolyte was obtained.

[0049] Example 3

[0050] A method for preparing a composite solid electrolyte comprises the following steps:

[0051] (1) Disperse 10 g of mesoporous silica and 1 g of KH570 in 100 mL of anhydrous ethanol, add 0.5 mL of triethanolamine, and reflux at 60 °C for 5 h. Filter the product, wash with alcohol, and dry it to obtain pretreated silica.

[0052] (2) 10 g of pretreated silica was dispersed in 100 mL of ethyl acetate, and ultrasonically treated for 30 min. Then, 10 mL of hexafluorobutyl acrylate and 20 mL of polyethylene glycol methyl ether acrylate were added, and nitrogen was continuously introduced. 0.3 g of azobisisobutyronitrile was added, and the mixture was stirred at 65° C. for 10 h. The product was cooled, centrifuged, washed with ethyl acetate three times, and dried to obtain the composite modifier.

[0053] (3) 60 g of PEO matrix was added to 300 g of acetonitrile and mixed evenly. Then, 25 g of lithium hexafluorophosphate, 14 g of composite modifier, and 5 g of ethoxy (pentafluoro) cyclotriphosphazene were added and stirred and dispersed at 40° C. for 10 h to obtain a casting slurry. The slurry was cast into a film. After the solvent evaporated, the composite solid electrolyte was obtained.

[0054] Example 4

[0055] A method for preparing a composite solid electrolyte comprises the following steps:

[0056] (1) Disperse 10 g of mesoporous silica and 0.3 g of KH570 in 100 mL of anhydrous ethanol, add 0.15 mL of triethanolamine, and reflux at 50 °C for 6 h. Filter the product, wash with alcohol, and dry it to obtain pretreated silica.

[0057] (2) 10 g of pretreated silica was dispersed in 100 mL of ethyl acetate, and ultrasonically treated for 30 min. Then, 10 mL of hexafluorobutyl acrylate and 20 mL of polyethylene glycol methyl ether acrylate were added, and nitrogen was continuously introduced. 0.05 g of azobisisobutyronitrile was added, and the mixture was stirred at 60° C. for 12 h. The product was cooled, centrifuged, washed with ethyl acetate three times, and dried to obtain the composite modifier.

[0058] (3) 60 g of PEO matrix was added to 300 g of acetonitrile and mixed evenly. Then, 15 g of lithium hexafluorophosphate, 10 g of composite modifier, and 3 g of ethoxy (pentafluoro) cyclotriphosphazene were added and stirred and dispersed at 20° C. for 12 h to obtain a casting slurry. The slurry was cast into a film. After the solvent evaporated, the composite solid electrolyte was obtained.

[0059] Comparative Example 1

[0060] A method for preparing a solid electrolyte comprises the following steps:

[0061] (1) Disperse 10 g of mesoporous silica and 3 g of KH570 in 100 mL of anhydrous ethanol, add 1.5 mL of triethanolamine, and reflux at 80 °C for 2 h. Filter the product, wash with alcohol, and dry it to obtain pretreated silica.

[0062] (2) 10 g of pretreated silica was dispersed in 100 mL of ethyl acetate, and ultrasonically treated for 30 min. Then, 15 mL of hexafluorobutyl acrylate was added, nitrogen was continuously introduced, 0.5 g of azobisisobutyronitrile was added, and the mixture was stirred at 75° C. for 4 h. The product was cooled, centrifuged, washed with ethyl acetate three times, and dried to obtain the composite modifier.

[0063] (3) 80 g of PEO matrix was added to 400 g of acetonitrile and mixed evenly. Then, 35 g of lithium hexafluorophosphate, 20 g of composite modifier, and 8 g of ethoxy (pentafluoro) cyclotriphosphazene were added and stirred and dispersed at 80° C. for 2 h to obtain a casting slurry. The slurry was cast into a film. After the solvent evaporated, the solid electrolyte was obtained.

[0064] Comparative Example 2

[0065] A method for preparing a solid electrolyte comprises the following steps:

[0066] (1) Disperse 10 g of mesoporous silica and 3 g of KH570 in 100 mL of anhydrous ethanol, add 1.5 mL of triethanolamine, and reflux at 80 °C for 2 h. Filter the product, wash with alcohol, and dry it to obtain pretreated silica.

[0067] (2) 10 g of pretreated silica was dispersed in 100 mL of ethyl acetate, and ultrasonically treated for 30 min. Then, 15 mL of polyethylene glycol methyl ether acrylate was added, nitrogen was continuously introduced, 0.5 g of azobisisobutyronitrile was added, and the mixture was stirred at 75° C. for 4 h. The product was cooled, centrifuged, washed with ethyl acetate three times, and dried to obtain the composite modifier.

[0068] (3) 80 g of PEO matrix was added to 400 g of acetonitrile and mixed evenly. Then, 35 g of lithium hexafluorophosphate, 20 g of composite modifier, and 8 g of ethoxy (pentafluoro) cyclotriphosphazene were added and stirred and dispersed at 80° C. for 2 h to obtain a casting slurry. The slurry was cast into a film. After the solvent evaporated, the solid electrolyte was obtained.

[0069] Comparative Example 3

[0070] A method for preparing a solid electrolyte comprises the following steps:

[0071] (1) Disperse 10 g of mesoporous silica and 3 g of KH570 in 100 mL of anhydrous ethanol, add 1.5 mL of triethanolamine, and reflux at 80 °C for 2 h. Filter the product, wash with alcohol, and dry it to obtain pretreated silica.

[0072] (2) 80 g of PEO matrix was added to 400 g of acetonitrile and mixed evenly. Then, 35 g of lithium hexafluorophosphate, 20 g of pretreated silica, and 8 g of ethoxy (pentafluoro) cyclotriphosphazene were added and stirred and dispersed at 80° C. for 2 h to obtain a casting slurry. The slurry was cast into a film. After the solvent evaporated, the solid electrolyte was obtained.

[0073] The solid electrolyte membranes prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were made into 20 mm × 75 mm strip specimens. The initial distance between the clamps was set to 50 ± 5 mm. The two ends of the specimen were placed in the upper and lower ends of the clamps in turn, and the clamps were clamped. During the process, the specimen and the clamps were ensured to be in the same vertical direction, and the force was uniform without obvious tensile deformation. After the preparation was completed, the tensile strength test was carried out at a rate of 150 ± 10 mm / min.

[0074] The solid electrolytes obtained in the examples and comparative examples were made into films with a thickness of 60±3 μm. The testing was performed using an MTS CMT4000 electronic testing machine. The maximum load when a needle with a spherical tip (curvature radius R: 0.5 mm) and a diameter of 1 mm was inserted into the film at a speed of 2 mm / s was measured to test its penetration resistance.

[0075] The solid electrolytes prepared in each embodiment and comparative example were assembled into soft-pack batteries with a graphite negative electrode sheet and a ternary positive electrode sheet under the same conditions. At a temperature of 25°C±2°C, in the first step, charging was performed at 0.1C or a specified current to the termination voltage, with a cutoff current of 0.01C, and the battery was allowed to stand for 30 minutes; in the second step, discharging was performed at 0.1C to the final discharge voltage (2.75V), recording the discharge capacity, and allowing the battery to stand for 30 minutes; the first and second steps were repeated, and the cycle performance of the battery was tested for 300 cycles.

[0076] After the composite solid electrolyte membrane is pressed into a sheet, it is placed in a mold sleeve at 60°C and pressurized. An AC impedance spectrum test is performed using an impedance analyzer, and the ionic conductivity of the electrolyte material is calculated based on the impedance value.

[0077] The solid electrolyte membrane was cut into discs with a diameter of 100 mm, placed in an oven at 150° C. for 1 h, taken out, and the diameter of the discs was measured again to calculate the thermal shrinkage of the solid electrolyte membrane.

[0078] The specific test results are shown in Table 1.

[0079] Table 1 Solid electrolyte performance test results

[0080]

[0081] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A composite solid electrolyte, characterized in that The invention is prepared from the following components in parts by weight: 60-80 parts of PEO matrix, 15-35 parts of lithium salt, 10-20 parts of composite modifier, and 3-8 parts of ethoxy (pentafluoro) cyclotriphosphazene; The preparation method of the composite modifier comprises the following steps: (1) Dispersing mesoporous silica and KH570 in anhydrous ethanol, adding triethanolamine, reflux reaction, filtering the product, washing with alcohol, and drying to obtain pretreated silica; (2) The pretreated silica is dispersed in ethyl acetate, ultrasonically treated, and then hexafluorobutyl acrylate and polyethylene glycol methyl ether acrylate are added, nitrogen is continuously introduced, azobisisobutyronitrile is added, and the reaction is stirred. The product is cooled, centrifuged, washed, and dried to obtain the composite modifier.

2. The composite solid electrolyte according to claim 1, characterized in that In step (1), the usage ratio of mesoporous silica, KH570, anhydrous ethanol, and triethanolamine is 10 g: 0.3-3 g: 50-100 mL: 0.15-1.5 mL.

3. The composite solid electrolyte according to claim 1, characterized in that In step (1), the reflux reaction conditions are 50-80° C. for 2-6 h.

4. The composite solid electrolyte according to claim 1, characterized in that In step (2), the usage ratio of pretreated silica, ethyl acetate, hexafluorobutyl acrylate, polyethylene glycol methyl ether acrylate, and azobisisobutyronitrile is 10 g: 100-150 mL: 10-15 mL: 15-20 mL: 0.05-0.5 g.

5. The composite solid electrolyte according to claim 1, characterized in that In step (2), ultrasonic treatment is performed for 10 to 30 minutes; the stirring reaction conditions are 60 to 75° C. and the stirring reaction is performed for 4 to 12 hours; and the product is washed with ethyl acetate 3 to 5 times.

6. The composite solid electrolyte according to claim 1, characterized in that The lithium salt is one or more of lithium perchlorate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonylimide), lithium bis(fluorosulfonylimide), lithium trifluoromethylsulfonate, lithium bis(oxalatoborate), lithium difluorooxalatoborate and lithium chloride.

7. A method for preparing the composite solid electrolyte according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: adding a PEO matrix into a solvent, mixing the mixture evenly, then adding a lithium salt, a composite modifier, and ethoxy (pentafluoro) cyclotriphosphazene, stirring and dispersing the mixture evenly to obtain a casting slurry, casting the slurry into a film, and obtaining the composite solid electrolyte after the solvent evaporates.

8. The preparation method according to claim 7, characterized in that The solvent is one or more of acetonitrile, acetone, DMF, and NMP; and the mass ratio of the PEO matrix to the solvent is 1:5-10.

9. The preparation method according to claim 7, characterized in that The stirring and dispersion conditions are 20~80℃ and 1~12h.

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