Solid-state battery with composite interface and preparation method thereof

Abstract

The invention relates to a solid-state battery with a composite interface and a preparation method of the solid-state battery. The solid-state battery comprises a positive plate, a negative plate, SEI protection layers coated on the positive plate and the negative plate, and a lithium ion conduction agent coating layer between the SEI protection layers. The SEI protective layer is formed by compounding a polymer matrix and an ion conduction lithium salt through a dip-coating method, the lithium ion conduction agent coating layer comprises an electrolyte lithium salt, a tackifier and an oxide solid electrolyte, and the lithium ion conduction agent coating layer is formed by mixing to prepare a lithium ion conduction agent and coating the lithium ion conduction agent. The problems that a traditional battery is lack of flexibility and poor in safety and an existing solid-state battery is high in interface impedance and short in cycle life are solved, cooperation of flexible protection and efficient ion conduction is achieved, the 200-circle cycle capacity retention rate reaches 90% or above, the preparation process is simple and controllable, material compatibility is good, an existing production line does not need to be transformed, industrial popularization is facilitated, and the method is suitable for industrial production. The method is suitable for energy storage scenes such as flexible electronic equipment and electric automobiles.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to a solid-state battery with a composite interface and its preparation method. Background Technology

[0002] In recent years, with the advancement of smart technology, various flexible devices have become the mainstay of the electronics market, leading to a growing demand for energy storage devices with high energy density, low manufacturing costs, and good flexibility. However, traditional lithium-ion battery materials lack flexibility, and the current collector is easily damaged during bending. Poor particle contact in the electrode materials during bending results in contact resistance. Furthermore, traditional liquid batteries, due to poor manufacturing processes or design flaws, or excessive liquid content, can lead to safety hazards such as fire and explosion after battery runaway.

[0003] To address these issues, researchers have begun exploring all-solid-state lithium-ion batteries as a novel energy storage device. All-solid-state lithium-ion batteries are fabricated by coating a solid electrolyte onto a porous substrate or between the positive and negative electrodes. However, current all-solid-state lithium-ion batteries still face several challenges, such as high interfacial impedance leading to low lithium-ion transport efficiency, resulting in poor rate performance and energy efficiency; poor stability of the electrode-solid electrolyte interface, making it prone to contact failure during cycling and affecting lifespan; and high requirements for industrial manufacturing and complex production processes, leading to high manufacturing costs.

[0004] To improve interface performance, existing technologies have introduced a scheme involving a single intermediate layer between the electrode and the solid electrolyte. For example, patent application CN115207475A discloses an ion-conducting polymer composite intermediate layer for solid-state battery packs and its formation method. This method involves converting a fluorinated polymer precursor layer under pressure and heat to form a lithium fluoride composite layer, thereby reducing interface impedance. However, this approach still has significant limitations: setting only a single layer between the electrode and the solid electrolyte cannot simultaneously achieve targeted protection for both the positive and negative electrodes, making it difficult to balance interface stability and ion transport efficiency; the intermediate layer is formed through the conversion of the precursor layer, resulting in poor thickness uniformity and structural controllability, making it impossible to precisely match the protection and conduction requirements of different electrodes; the lack of a dedicated ion conduction enhancement design means that the intermediate layer simultaneously performs both protection and conduction functions, easily leading to a contradiction where excessive protection results in insufficient conduction, and optimized conduction results in weak protection; furthermore, the preparation process requires high pressure and high temperature, resulting in high process complexity and hindering industrialization.

[0005] Therefore, there is an urgent need to develop a method that is simpler to implement, more universal, and can simultaneously construct solid-state batteries with stable interfaces at the positive and negative electrode interfaces of the battery, so as to promote the application of solid-state batteries from the laboratory to large-scale applications. Summary of the Invention

[0006] The present invention aims to provide a solid-state battery with a composite interface and its preparation method. The composite interface consists of an artificial SEI protective layer on the positive electrode side, a high-viscosity lithium-ion conductive agent coating layer, and an artificial SEI protective layer on the negative electrode side. The artificial SEI protective layer uses an organic polymer matrix as a flexible framework and is composed of an inorganic ion-conducting lithium salt. The lithium-ion conductive agent coating layer includes lithium electrolyte, oxide solid electrolyte, and a thickener. The SEI protective layer is prepared by dip-coating, and the lithium-ion conductive agent coating layers are then applied between the SEI protective layers. This achieves a synergistic effect of flexible adaptability, safety protection, and efficient ion transport, while simplifying the process and reducing costs, meeting the large-scale application needs of flexible electronic devices, electric vehicles, and other scenarios.

[0007] The technical solution provided by this invention is as follows: a solid-state battery with a composite interface, comprising a positive electrode and a negative electrode. The first surface of the positive electrode is provided with a first SEI protective layer; The first surface of the negative electrode sheet is provided with a second SEI protective layer; The first surface of the positive electrode is arranged facing the first surface of the negative electrode; A lithium-ion conductive agent coating layer is provided between the first SEI protective layer and the second SEI protective layer; The first SEI protective layer and the second SEI protective layer comprise a polymer matrix and an ion-conducting lithium salt dispersed in the polymer matrix; the lithium ion conductive coating layer comprises an electrolyte lithium salt, a thickener, and an oxide solid electrolyte.

[0008] The composite interface structure of a dual SEI protective layer and a lithium-ion conductive agent coating layer achieves a synergistic effect of flexible protection and efficient ion conduction. The dual SEI protective layer relies on a composite system of polymer matrix and ion-conducting lithium salt to both block short circuits and side reactions between the positive and negative electrodes and ensure ion transport. The conductive agent coating layer, through the combination of electrolyte lithium salt, thickener, and oxide solid electrolyte, reduces interfacial impedance, solving the shortcomings of traditional batteries such as lack of flexibility and poor safety, as well as the low interfacial conduction efficiency of existing solid-state batteries, and significantly improving the overall performance of the battery.

[0009] Preferably, the thickness of the first SEI protective layer is 1-15 μm, the thickness of the second SEI protective layer is 1-15 μm, and the thickness of the lithium ion conductive agent coating layer is 5 μm-50 μm.

[0010] Limiting the reasonable thickness range of the three-layer structure avoids the SEI layer being too thick, which would lead to increased impedance, or too thin, which would result in insufficient protection. At the same time, the thickness of the conductive agent coating layer is controlled to adapt to the ion transport requirements. Matching the thickness parameters ensures tight bonding between layers, reduces interface gaps, improves the uniformity of ion conduction and the cycle stability of the battery, and provides a clear dimensional reference for industrial production.

[0011] Preferably, the mass ratio of the polymer matrix to the ion-conducting lithium salt is 1:0.3~0.6.

[0012] The mass ratio of polymer matrix to ion-conducting lithium salt is optimized to ensure that the SEI protective layer is both flexible enough and has high ion conduction efficiency. The ratio range is precisely matched to meet the synergistic requirements of the flexible framework and functional components, avoiding insufficient conduction due to excessive polymer or structural embrittlement due to excessive lithium salt, thereby improving the structural stability and electrochemical performance of the SEI layer.

[0013] Preferably, the mass ratio of the electrolyte lithium salt, thickener, and oxide solid electrolyte is 10-25:3:10-30.

[0014] By defining the mass ratio range of the three components in the conductive agent, a balance is achieved in terms of high ion concentration, interfacial adhesion, and structural support. The lithium electrolyte provides a sufficient ion source, the tackifier ensures interlayer adhesion, and the oxide solid electrolyte strengthens the structure. Optimizing the ratio avoids excessive tackifier hindering conduction and excessive oxide content increasing impedance, thereby improving the overall compatibility of the conductive agent coating layer.

[0015] Preferably, the polymer matrix is ​​at least one selected from polyvinylidene fluoride, polyacrylic acid, sodium carboxymethyl cellulose, polyimide, and polyacrylonitrile; The ion-conducting lithium salt is at least one of lithium nitride, lithium fluoride, lithium hexafluorophosphate, lithium difluorobis(oxalato)borate, lithium difluorophosphate, and lithium bis(trifluoromethanesulfonyl)imide.

[0016] Preferably, the electrolyte lithium salt is at least one of lithium hexafluorophosphate, lithium difluorobis(oxalato)borate, lithium difluorophosphate, and lithium bis(trifluoromethanesulfonyl)imide. The oxide solid electrolyte is at least one of lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium aluminum oxide, lithium lanthanum zirconium gallium oxide, lithium lanthanum titanium oxide, lithium germanium aluminum phosphate, or lithium titanium aluminum phosphate. The tackifier is at least one of polyimide hot melt adhesive, ethylene-vinyl acetate copolymer, styrene-isoprene-styrene block copolymer, polyethylene wax, or polyethylene oxide wax.

[0017] The method for preparing a solid-state battery with a composite interface as described above includes the following steps: 1) The polymer matrix and ion-conducting lithium salt are dissolved in an organic solvent and homogenized to obtain an impregnation and lifting solution; 2) Based on the impregnation and pulling liquid, a uniform liquid film is formed on the first surface of the positive electrode and the first surface of the negative electrode by the impregnation and pulling method; after the positive electrode and the negative electrode covered with the liquid film are heat-treated, a first SEI protective layer is formed on the first surface of the positive electrode and a second SEI protective layer is formed on the first surface of the negative electrode. 3) Dissolve the lithium electrolyte salt in an organic solvent, and then add a thickener and an oxide solid electrolyte in sequence to form a lithium ion conductor; 4) The lithium-ion conductive agent is coated on the first SEI protective layer, the positive and negative electrode sheets are pressed together, and after heating and pressurizing to exhaust the gas, a lithium-ion conductive agent coating layer is formed between the first SEI protective layer and the second SEI protective layer, thus obtaining a solid-state battery with a composite interface.

[0018] The preparation method has a continuous and simple operation. The dip-coating method can precisely control the uniformity of the SEI layer, and the coating method is suitable for the preparation of the conductive agent layer. The process is highly compatible with existing battery production processes, requiring no major modification to the production line and lowering the industrialization threshold. The step-by-step preparation ensures the integrity of each layer structure and stable performance, guaranteeing the consistency and repeatability of the composite interface.

[0019] Preferably, in step 2), the parameters for the immersion and lifting operation are set as follows: immersion speed 1-5 mm / s, immersion time 1-10 min, and lifting speed 1-5 mm / s.

[0020] Limiting the optimized parameter range for impregnation and lifting avoids uneven liquid film due to excessively fast impregnation and lifting speed, and excessive film thickness due to excessively slow impregnation and lifting speed. Parameter adaptation ensures uniform SEI layer thickness and high density, reduces porosity and defects, improves the protective effect and ion conduction efficiency of SEI layer, and provides controllable process parameter basis for large-scale production.

[0021] Preferably, in step 2), the positive and negative electrode plates covered by the liquid film are subjected to heat treatment, specifically as follows: The positive and negative electrode plates covered with liquid film are dried in an oven at 40-60℃; then transferred to a vacuum oven at 70-90℃ to remove residual organic solvents; finally, they are treated in a muffle furnace at 200-300℃ under an argon atmosphere.

[0022] The stepwise heat treatment process first gently removes most of the solvent to avoid surface peeling and cracking, then thoroughly removes residual liquid, and finally strengthens the interlayer bonding; argon atmosphere protection prevents material oxidation, and the temperature range is adapted to the material characteristics, significantly improving the structural stability and density of the SEI layer and avoiding performance degradation caused by improper heat treatment.

[0023] Preferably, in step 4), the exhaust temperature is 70-100℃ and the exhaust pressure is 0.8-1.2MPa.

[0024] Optimizing exhaust temperature and pressure parameters can effectively remove residual gas between layers, avoiding the formation of dead lithium and interface voids; parameter adaptation ensures tight adhesion between the conductive agent coating layer and the double SEI layer, reducing interface impedance, improving battery cycle performance and consistency, and providing a clear standard for process control in industrial production.

[0025] The beneficial effects of this invention are as follows: 1. Enhanced flexibility and safety: The artificial SEI protective layer uses an organic polymer matrix as a flexible framework and inorganic functional components as the protective core. It not only solves the problems of traditional battery materials being inflexible and easily damaged by bending, but also blocks short circuits and side reactions between the positive and negative electrodes, completely avoiding the risk of fire and explosion caused by liquid electrolytes, and is suitable for flexible electronic devices and large-scale energy storage scenarios.

[0026] 2. Significantly optimized ion conduction efficiency: The high-viscosity, high-ion conduction agent layer provides a high concentration of lithium ions through lithium ion source compounds. Combined with the structural support of the oxide solid electrolyte and the interfacial bonding effect of the thickener, the interfacial impedance is greatly reduced, solving the problems of insufficient ion transport and poor rate performance of existing solid batteries.

[0027] 3. Significantly extended cycle life: The double-layer SEI protective layer and the conductive agent layer form an integrated structure, which improves the contact area and stability between the solid electrolyte and the electrode, reduces side reactions and dead lithium generation during cycling, and the capacity retention rate can reach more than 90% after 200 cycles.

[0028] 4. High industrial feasibility: The SEI layer is prepared by dip-coating method, the process parameters are controllable and the operation is simple. The selected materials are all common types in the industry and have good compatibility with the existing battery production process. There is no need to make major modifications to the production line, which effectively reduces manufacturing costs and is conducive to large-scale promotion.

[0029] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below. Specific embodiments of the present invention are given in detail in the following examples. Detailed Implementation

[0030] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0031] In the following examples and comparative examples, high-nickel NCM ternary cathode material is used as the cathode material and graphite is used as the anode material.

[0032] Example 1 This embodiment provides a solid-state battery with a composite interface, and the preparation steps are as follows: 1) Slowly add polyvinylidene fluoride powder to N-methylpyrrolidone and stir magnetically for 4 hours in a water bath at 50°C to prepare a polyvinylidene fluoride solution with a mass fraction of 2wt%.

[0033] Lithium fluoride nanoparticles were slowly added to the above polyvinylidene fluoride solution at a mass ratio of polyvinylidene fluoride:lithium fluoride = 1:0.5. The mixture was then transferred to a planetary mixer and stirred at 300 rpm for 6 hours. Subsequently, ultrasonic treatment was performed to obtain a stable, uniform impregnation and lifting solution with no obvious sedimentation for later use.

[0034] 2) Fix the positive and negative electrode sheets onto the clamps of the impregnation and pulling machine. Set the impregnation and pulling machine parameters: impregnation speed: 2 mm / s, impregnation time: 1 min, pulling speed: 1 mm / s. Start the equipment, immerse the electrode sheets in the impregnation and pulling solution prepared in step 1), and after a period of time, pull them out of the liquid surface at a constant speed. That is, a uniform liquid film is formed on the first surface of both the positive and negative electrode sheets.

[0035] 3) Place the positive and negative electrode sheets covered with the liquid film in a 50°C oven and dry for 30 min (gently remove most of the solvent and prevent surface peeling and cracking); then transfer them to an 80°C vacuum oven and treat for 2 h to completely remove residual solvent; finally, heat treat them in a muffle furnace at 250°C for 1 h under argon atmosphere (enhance the bonding between the polymer and inorganic particles and induce partial phase change in PVDF to improve the overall stability and density of the protective layer), thus forming a 7 μm thick SEI protective layer on the surface of the positive and negative electrode sheets.

[0036] 4) Dissolve lithium bis(trifluoromethanesulfonylimide) in tetrahydrofuran. After it is fully dissolved, add polyethylene wax as a thickener, and then add lithium titanium aluminum phosphate and mix evenly to obtain a lithium ion conductor. The mass ratio of lithium bis(trifluoromethanesulfonylimide), polyethylene wax and lithium titanium aluminum phosphate is 20:3:20.

[0037] 5) A lithium-ion conductive agent is coated on the surface of the positive electrode, and the positive and negative electrode sheets are stacked and pressed together. A pressure of 1MPa is applied at 80°C to expel the gas on the surface of the electrode sheets, preventing the formation of dead lithium on the electrode surface and affecting the battery performance. A lithium-ion conductive agent coating layer is formed between the SEI protective layer of the positive electrode and the SEI protective layer of the negative electrode, resulting in a solid-state battery with a composite interface.

[0038] Example 2 This embodiment provides a solid-state battery with a composite interface. Its preparation steps are basically the same as those in Example 1, except that in step 1), lithium fluoride is replaced with bis(trifluoromethanesulfonylimide) lithium.

[0039] Example 3 This embodiment provides a solid-state battery with a composite interface. Its preparation steps are basically the same as those in Embodiment 1, except that in step 1), polyvinylidene fluoride is replaced with polyimide.

[0040] Example 4 This embodiment provides a solid-state battery with a composite interface. Its preparation steps are basically the same as those in Embodiment 1, except that in step 1), the mass ratio of polyvinylidene fluoride to lithium fluoride is adjusted from 1:0.5 to 1:0.3.

[0041] Example 5 This embodiment provides a solid-state battery with a composite interface. Its preparation steps are basically the same as those in Embodiment 1, except that in step 2), the parameters of the dip-pull machine are changed: the pulling speed is changed to 1 mm / s, and the thickness of the SEI protective layer after heat treatment in step 3) is 14 μm.

[0042] Example 6 This embodiment provides a solid-state battery with a composite interface. Its preparation steps are basically the same as those in Embodiment 1, except that in step 2), the parameters of the dip-coating machine are changed to 5 mm / s, and the thickness of the SEI protective layer after heat treatment in step 3) is 1 μm.

[0043] Example 7 This embodiment provides a solid-state battery with a composite interface. The preparation steps are basically the same as those in Embodiment 1, except that in step 4), the mass ratio of bis(trifluoromethanesulfonylimide) lithium, polyethylene oxide wax, and lithium titanium aluminum phosphate is 10:3:20.

[0044] Example 8 This embodiment provides a solid-state battery with a composite interface. The preparation steps are basically the same as those in Example 1, except that in step 4), the mass ratio of bis(trifluoromethanesulfonylimide) lithium, polyethylene oxide wax, and lithium titanium aluminum phosphate is 15:3:20.

[0045] Example 9 This embodiment provides a solid-state battery with a composite interface. The preparation steps are basically the same as those in Example 1, except that in step 4), the mass ratio of bis(trifluoromethanesulfonylimide) lithium, polyethylene oxide wax, and lithium titanium aluminum phosphate is 25:3:20.

[0046] Example 10 This embodiment provides a solid-state battery with a composite interface. The preparation steps are basically the same as those in Embodiment 1, except that in step 4), the mass ratio of bis(trifluoromethanesulfonylimide) lithium, polyethylene oxide wax, and lithium titanium aluminum phosphate is 20:3:10.

[0047] Example 11 This embodiment provides a solid-state battery with a composite interface. The preparation steps are basically the same as those in Embodiment 1, except that in step 4), the mass ratio of bis(trifluoromethanesulfonylimide) lithium, polyethylene oxide wax, and lithium titanium aluminum phosphate is 15:3:30.

[0048] Example 12 This embodiment provides a solid-state battery with a composite interface. Its preparation steps are basically the same as those in Embodiment 1, except that in step 2), the parameters of the dip-coating machine are changed to 5 min, and the thickness of the SEI protective layer after heat treatment in step 3) is 15 μm.

[0049] Comparative Example 1 This comparative example provides a solid-state battery whose preparation steps are basically the same as those in Example 1, except that steps 1), 2), and 3) are not performed, and the positive and negative electrode sheets are not covered with an SEI protective layer.

[0050] Comparative Example 2 This comparative example provides a solid-state battery whose preparation steps are basically the same as those in Example 1, except that steps 4) and 5) are not performed, and no lithium-ion conductive agent coating layer is prepared between the SEI protective layers of the positive and negative electrodes.

[0051] The above embodiments and comparative examples were assembled into pouch cells, and performance tests were conducted, as follows: Within a voltage range of 2.5-4.2V, the battery was subjected to a 200-cycle charge / discharge test at 1C. The highest internal and external surface temperatures and capacity retention were recorded. The test results are shown in Table 1. Table 1. Electrochemical performance of solid-state batteries prepared in each embodiment and comparative example. Comparative Example 1 (without SEI protective layer) had a capacity retention rate of only 20.1% after 200 cycles and a coulombic efficiency of 53.2%, which was significantly lower than all examples with double SEI protective layers. This proves that the SEI protective layer formed on the positive and negative electrodes can effectively block short circuits and side reactions between the positive and negative electrodes, reduce electrode losses during cycling, and is the key to improving battery stability. Comparative Example 2 (without lithium-ion conductive agent coating) could not complete 200 cycles and could only record the first discharge capacity, indicating that the conductive agent coating is the core channel for efficient lithium-ion transport between the two SEI layers. Without it, ion transport is blocked and the battery fails quickly. Examples 1-3, 7-8, 11, and 13 all achieved a capacity retention rate of over 91% after 200 cycles, with an initial discharge capacity ≥203mAh / g. This demonstrates that the integrated structure of the double SEI protective layer and the lithium-ion conductive agent coating layer achieves a synergistic effect of flexible protection and efficient ion conduction, solving the problems of high interface impedance and short cycle life of existing solid-state batteries.

[0052] The performance differences between Examples 1 (PVDF+LiF), 2 (PVDF+lithium bis(trifluoromethanesulfonylimide), and 3 (polyimide+LiF) are minimal (retention rate 92.1%-93.1%). The polymer matrix and the ion-conducting lithium salt combination all exhibit good compatibility, forming a dense and flexible protective layer suitable for different material requirements. Example 4, with a reduced lithium fluoride content compared to the examples, shows a decrease in retention rate to 89.5%, indicating that within this range, a higher lithium salt content results in stronger ion conduction efficiency.

[0053] A performance comparison of Examples 1 (7 μm film thickness) and 6 (1 μm film thickness) shows that the coulombic efficiency is only 72.5% with a film thickness of 1 μm, failing to complete 200 cycles. This is attributed to insufficient protection due to the thin film thickness, making interface failure more likely. The retention rate of Example 5 (14 μm film thickness) drops to 50.1%, and the initial discharge capacity decreases significantly. Similarly, the retention rate and initial discharge capacity of Example 12 (15 μm film thickness) also decrease significantly. This indicates that an excessively thick SEI layer increases the ion transport path length, leading to increased impedance.

[0054] Examples 7-9 show the effect of the electrolyte lithium salt ratio on electrochemical performance. When the electrolyte lithium salt ratio is too low, the cycle retention rate is much lower than 93.1% of Example 1, indicating that the ion concentration is insufficient and cannot meet the lithium ion transport requirements during cycling. On the other hand, excessive electrolyte lithium salt will lead to interface polarization, so the retention rate of Example 9 drops to 87.5%.

[0055] The retention rates after 200 cycles in Examples 10 and 11 were 82.5% and 86.4%, respectively, both lower than the 93.1% in Example 1. This indicates that when the proportion of oxide solid electrolyte is too low, the structural support is insufficient, while when it is too high, it increases the viscosity of the conductive agent and hinders ion migration.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention according to the description and above. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, based on the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A solid-state battery with a composite interface, comprising a positive electrode and a negative electrode, characterized in that, The first surface of the positive electrode is provided with a first SEI protective layer; The first surface of the negative electrode sheet is provided with a second SEI protective layer; The first surface of the positive electrode is arranged facing the first surface of the negative electrode; A lithium-ion conductive agent coating layer is provided between the first SEI protective layer and the second SEI protective layer; The first SEI protective layer and the second SEI protective layer comprise a polymer matrix and an ion-conducting lithium salt dispersed in the polymer matrix; the lithium ion conductive coating layer comprises an electrolyte lithium salt, a thickener, and an oxide solid electrolyte.

2. The solid-state battery with a composite interface according to claim 1, characterized in that, The thickness of the first SEI protective layer is 1-15 μm, the thickness of the second SEI protective layer is 1-15 μm, and the thickness of the lithium ion conductive agent coating layer is 5 μm-50 μm.

3. A solid-state battery with a composite interface according to claim 1, characterized in that, The mass ratio of the polymer matrix to the ion-conducting lithium salt is 1:0.3~0.

6.

4. A solid-state battery with a composite interface according to claim 1, characterized in that, The mass ratio of the electrolyte lithium salt, thickener, and oxide solid electrolyte is 10-25:3:10-30.

5. A solid-state battery with a composite interface according to claim 1, characterized in that, The polymer matrix is ​​at least one of polyvinylidene fluoride, polyacrylic acid, sodium carboxymethyl cellulose, polyimide, and polyacrylonitrile; The ion-conducting lithium salt is at least one of lithium nitride, lithium fluoride, lithium hexafluorophosphate, lithium difluorobis(oxalato)borate, lithium difluorophosphate, and lithium bis(trifluoromethanesulfonyl)imide.

6. A solid-state battery with a composite interface according to claim 1, characterized in that, The electrolyte lithium salt is at least one of lithium hexafluorophosphate, lithium difluorobis(oxalato)borate, lithium difluorophosphate, and lithium bis(trifluoromethanesulfonyl)imide. The oxide solid electrolyte is at least one of lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium aluminum oxide, lithium lanthanum zirconium gallium oxide, lithium lanthanum titanium oxide, lithium germanium aluminum phosphate, or lithium titanium aluminum phosphate. The tackifier is at least one of polyimide hot melt adhesive, ethylene-vinyl acetate copolymer, styrene-isoprene-styrene block copolymer, polyethylene wax, or polyethylene oxide wax.

7. A method for preparing a solid-state battery with a composite interface according to any one of claims 1-6, characterized in that, Includes the following steps: 1) The polymer matrix and ion-conducting lithium salt are dissolved in an organic solvent and homogenized to obtain an impregnation and lifting solution; 2) Based on the impregnation and pulling liquid, a uniform liquid film is formed on the first surface of the positive electrode and the first surface of the negative electrode by the impregnation and pulling method; after the positive electrode and the negative electrode covered with the liquid film are heat-treated, a first SEI protective layer is formed on the first surface of the positive electrode and a second SEI protective layer is formed on the first surface of the negative electrode. 3) Dissolve the lithium electrolyte salt in an organic solvent, and then add a thickener and an oxide solid electrolyte in sequence to form a lithium ion conductor; 4) The lithium-ion conductive agent is coated on the first SEI protective layer, the positive and negative electrode sheets are pressed together, and after heating and pressurizing to exhaust the gas, a lithium-ion conductive agent coating layer is formed between the first SEI protective layer and the second SEI protective layer, thus obtaining a solid-state battery with a composite interface.

8. The method for preparing a solid-state battery with a composite interface according to claim 7, characterized in that, In step 2), the parameters for the immersion and lifting operation are set as follows: immersion speed 1-5 mm / s, immersion time 1-10 min, and lifting speed 1-5 mm / s.

9. The method for preparing a solid-state battery with a composite interface according to claim 7, characterized in that, Step 2) involves heat-treating the positive and negative electrode plates covered by the liquid film, as follows: The positive and negative electrode plates covered with liquid film are dried in an oven at 40-60℃; then transferred to a vacuum oven at 70-90℃ to remove residual organic solvents; finally, they are treated in a muffle furnace at 200-300℃ under an argon atmosphere.

10. The method for preparing a solid-state battery with a composite interface according to claim 7, characterized in that, In step 4), the exhaust temperature is 70-100℃ and the exhaust pressure is 0.8-1.2MPa.

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