A solid-state electrolyte porous skeleton and a preparation method and application thereof

Abstract

This invention relates to the technical field of solid electrolyte preparation methods, specifically disclosing a porous framework for a solid electrolyte, its preparation method, and its applications. The framework exhibits a gradient porosity distribution, with 50%-70% porosity on one side and 70%-90% on the other, with an average pore size of 50-100 nm and a total thickness of 25-35 μm. The preparation method involves first mixing a high-dielectric material precursor, solvent, and binder, then coating the mixture onto a substrate surface. Next, it undergoes Joule heat treatment in an anhydrous and oxygen-free atmosphere to raise the temperature to 800-2000℃ and sinter. Finally, the resulting dry film is peeled off from the substrate. The preparation method proposed in this invention is low-cost, highly efficient, and suitable for large-scale continuous production. The resulting porous framework for the solid electrolyte has accurate stoichiometry, high material purity, and small grain size. When fabricated into a solid electrolyte film, it exhibits high ion transport efficiency and good interfacial stability.

Description

Technical Field

[0001] This invention relates to the technical field of solid electrolyte preparation methods, and in particular to a porous framework for a solid electrolyte, its preparation method, and its application. Background Technology

[0002] Compared to traditional liquid electrolyte lithium-ion batteries, all-solid-state lithium batteries offer higher safety and higher energy density, and are considered strong contenders for the next generation of batteries.

[0003] Currently, the conventional method for preparing solid electrolyte frameworks by powder sintering is to use traditional heating furnaces such as muffle furnaces for high-temperature sintering. Since inorganic powders and high dielectric materials are mixed using only a simple mixing method, problems such as powder agglomeration and poor interfacial contact are easily generated during high-temperature sintering. As a result, the inorganic filler cannot fully exert its material properties, and the improvement effect on ion transport efficiency and interfacial stability of the resulting composite solid electrolyte is limited. Moreover, the high-temperature sintering method has the following technical defects: (1) High energy consumption and long time: The use of large-volume heat preservation materials and heating elements results in a large distance between them and the sample, slow heating (about 5-10℃ / min), and a heat preservation time of several hours, resulting in high energy consumption and low efficiency; (2) Volatile material components: Sulfide precursors (such as P2S5) are volatile at high temperatures, and long-term exposure will lead to the loss of P and S, resulting in poor control of the stoichiometry, material purity and electrochemical performance of the obtained solid electrolyte; (3) Large product grains: Long-term high-temperature treatment leads to grain coarsening and wide particle size distribution, which is not conducive to the improvement of ionic conductivity; (4) Unable to scale up continuous production: Existing technologies are mostly batch sintering, and the consistency between batches is difficult to control, which cannot meet the needs of large-scale continuous production for the industrialization of solid electrolytes.

[0004] Based on this, developing a solid electrolyte framework with high ion transport efficiency and interface stability, and overcoming the shortcomings of traditional high-temperature sintering such as high energy consumption, long time, easy volatility of material components, large product grains, and inability to achieve large-scale continuous production, is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] Based on the background technology, this invention provides a porous framework for solid electrolytes, its preparation method, and its application, in order to solve the problems of limited improvement in ion transport efficiency and interface stability of solid electrolyte frameworks prepared by existing technologies, as well as the defects of preparation methods such as high energy consumption, long preparation time, easy volatility of material components, large product grains, and inability to achieve large-scale continuous production.

[0006] To achieve the above objectives, the main technical solutions adopted by the present invention are as follows.

[0007] Firstly, this invention proposes a porous framework for a solid electrolyte, in which the porosity is distributed in a gradient, with the porosity on one side being 50%-70% and the porosity on the other side being 70%-90%.

[0008] In this solid electrolyte porous framework, the porous structure with a gradient porosity eliminates the problems of powder agglomeration and poor interfacial contact that exist in traditional high-temperature sintering technology, allowing the high dielectric precursor to fully perform, increasing ionic conductivity by 1-2 orders of magnitude, and significantly reducing interfacial impedance.

[0009] Furthermore, its average pore size is 50-100 nm.

[0010] Furthermore, its total thickness is 25-35μm.

[0011] Secondly, this invention proposes a method for preparing a porous framework for a solid electrolyte, employing carbon thermal shock ultrafast sintering, specifically including the following steps: S1. The high dielectric material precursor is uniformly mixed with solvent and binder to prepare a casting slurry; S2. The casting paste is coated onto one surface of the substrate to form a uniform wet film; S3. Place the substrate obtained in the previous step in an anhydrous and oxygen-free atmosphere (such as a glove box), and apply Joule heat treatment to the side of the substrate that is not coated with the casting paste. The wet film becomes a dry film after Joule heat treatment. S4. After the dry film cools down, peel it off from the substrate to obtain the final product.

[0012] This invention employs Joule heat treatment, which enables instantaneous high-temperature sintering of graphite. This avoids the volatilization of elements or components in the high-dielectric precursor and helps obtain fine, uniform grains. Furthermore, because Joule heat treatment is applied to the side of the substrate uncoated with the casting paste, the resulting high temperature is distributed in a gradient from the bottom to the top of the wet film, thus forming a gradient porous structure along the thickness direction of the resulting dry film. In addition, this invention can complete sintering within seconds, significantly reducing energy consumption and improving production efficiency.

[0013] Furthermore, in the implementation of this preparation method, the substrate is wound onto an unwinding roller to form an unwinding unit. Following the unwinding unit, a coating unit for applying the cast slurry to the substrate, a sintering unit for Joule heat treatment, a cooling unit for cooling the dry film, a demolding unit for separating the dry film from the substrate, and a winding unit for distributing and rewinding the dry film and substrate are arranged sequentially. Through this apparatus, via... Figure 6 The process flow shown enables continuous and large-scale preparation of porous solid electrolyte frameworks. The roll-to-roll equipment has good batch consistency and is suitable for industrial production. Moreover, the substrate can be recycled after winding, which helps to further reduce production costs.

[0014] Furthermore, in step S3, the Joule heat treatment temperature is 800-2000℃; Preferably, the heating rate of the Joule heat treatment is 190-800℃ / s; Preferably, the Joule heat treatment uses a carbon heating substrate with a thickness of 5-15 mm and a volume resistivity of 0.01-0.5 Ω•cm, and applies a current density of 50-200 A / cm. 2 The DC current can achieve the heating rate required above, so that the temperature of the wet film can be rapidly raised to 800-2000℃ within 1-60s, and the overall energy consumption is low; as for the carbon heating substrate, for example, it is selected from any one of carbon plate, carbon fiber plate, and graphite plate.

[0015] Furthermore, the side of the substrate without the wet film faces the carbon heating substrate and the distance between the substrate and the carbon heating substrate does not exceed 3mm; the distance between the substrate and the carbon heating substrate is as close as possible, preferably in direct contact, to ensure efficient heat transfer and avoid large heat loss and uneven or uncontrollable heating of the wet film; Preferably, both surfaces of the substrate are coated with an isolation protective layer; more preferably, the isolation protective layer is a boron nitride coating or an aluminum oxide coating; the isolation protective layer can protect the substrate from corrosion by the solid electrolyte precursor, and also act as a release agent to facilitate the peeling of the porous framework of the solid electrolyte from the substrate; the isolation protective layer on both surfaces allows the substrate to be recycled, avoids repeated rewinding, and helps to reduce production costs; Preferably, when selecting the substrate, a substrate that meets the following performance requirements is more effective: thermal conductivity ≥80W / (m•K), and areal density of 80-170g / m². 2 Substrate materials with tensile strength ≥ 500 MPa, elastic modulus ≥ 210 GPa, and elongation at break ≥ 1.5% are particularly effective. Substrate materials meeting the following performance requirements are especially desirable: tensile strength ≥ 600 MPa, elastic modulus ≥ 240 GPa, and elongation at break ≥ 1.7%. Regarding the specific material of the substrate, high-temperature resistant carbon cloth is preferred. This is a multi-layered mesh structure woven from carbon fibers with a thickness of 0.1-0.5 mm. The carbon fibers have a dense, disordered graphite structure and highly oriented graphite microcrystals, and the packing density of the carbon fibers in the multi-layered mesh structure is 80-170 g / m³. 2 ; Preferably, since impurities such as Fe and S may contaminate the solid electrolyte and thus affect ionic conductivity, or may eventually be incorporated into the cell as part of the solid electrolyte, causing short circuits, the chemical composition of the substrate requires a carbon content ≥99%, ash content ≤500ppm, Fe ≤50ppm, and S ≤0.001%, with ash content ≤400ppm and Fe ≤20ppm being particularly effective. Furthermore, during the Joule heat treatment, the conveyor speed of the substrate relative to the carbon heating substrate is 1-100mm / s, and the effective sintering time is 1-500s; preferably, the conveyor speed of the substrate relative to the carbon heating substrate is 20-40mm / s, and the effective sintering time is 10-25s.

[0016] The specific operation of Joule heat treatment is as follows: the substrate passes through the carbon heating substrate at a certain conveyor belt speed, that is, Joule heat treatment is performed while the substrate is being conveyed. In this technical solution, the conveyor belt speed of the substrate should not be too low. Although a low speed allows for sufficient heat accumulation and more thorough drying of the wet film, it can easily lead to local overheating, deformation or cracking of the dry film. It should also not be too high. If the speed is too high, the heat treatment time will be too short, the heat accumulation will be insufficient, the wet film will not dry thoroughly, and it may cause uneven dry film thickness.

[0017] Furthermore, in step S1, the mass percentage of each component in the casting slurry is as follows: high dielectric precursor 10wt%-30wt%, binder 2wt%-8wt%, solvent 62wt%-88wt%; Preferably, the coating thickness of the casting paste on the substrate is 50-150 μm; Preferably, the relative permittivity εr of the high-dielectric material precursor is greater than 20 and the particle size is 20-500 nm; more preferably, the high-dielectric material precursor is selected from at least one of barium titanate, strontium titanate, lithium niobate, potassium niobate, lead titanate, lead zirconate titanate, and tantalum oxide. Preferably, the adhesive is selected from at least one of polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP). Preferably, the solvent is selected from at least one of N,N-dimethylacetamide, acetone, and anhydrous ethanol.

[0018] The preparation method proposed in this invention has continuous mass production capability. Compared with the traditional sintering method, it has low energy consumption, simple process, and controllable cost. Moreover, its roll-to-roll production method also ensures good batch consistency and is suitable for large-scale industrial production.

[0019] Thirdly, the present invention proposes a composite solid electrolyte film, comprising the above-mentioned solid electrolyte porous framework and polymer electrolyte.

[0020] In this technical solution, the porous framework of the solid electrolyte serves as the structural support, with a total thickness controlled at 25-35 μm. This maintains the mechanical integrity of the composite electrolyte film and constructs a good ion conduction network, thereby balancing strength and ion transport. Its rich porous design can absorb volume changes during charging and discharging, effectively suppressing dendrite penetration. Moreover, the porous structure with a stepped porosity distribution has the following beneficial effects: (1) it optimizes the interface and reduces the electrode / electrolyte interface impedance; (2) it increases the specific surface area and promotes the penetration of polymer electrolyte monomers; (3) it enhances thermal stability and has strong thermal shock resistance.

[0021] Furthermore, the polymer electrolyte is a PVDF-HFP or / and PEO-based solid electrolyte (polyvinylidene fluoride-hexagonal boron nitride or / and polyethylene oxide solid electrolyte), and the mass ratio of the polymer electrolyte to the porous framework of the solid electrolyte is (1-3):1; Preferably, the polymer electrolyte is formed by in-situ solidification of the corresponding polymerization precursor liquid within the porous framework of the solid electrolyte; for example, the polymeric polyelectrolyte is PVDF-HFP, and its preparation method is as follows: first, PVDF-HFP monomer, lithium salt, and thermal initiator are uniformly mixed to form a polymerization precursor liquid, then the porous framework of the solid electrolyte is placed in the polymerization precursor liquid, the polymerization precursor liquid is vacuum-wetted into the pores of the porous framework of the solid electrolyte, and then the temperature is raised to heat the polymer precursor liquid in the pores to solidify in-situ, thereby obtaining a composite solid electrolyte film; Preferably, the polymer electrolyte is further doped with one or more of the following: sulfide solid electrolyte, phosphate solid electrolyte, and garnet-type solid electrolyte.

[0022] Fourth, the present invention proposes an all-solid-state battery, comprising a positive electrode, a negative electrode and the above-mentioned composite solid-state electrolyte film.

[0023] Specifically, taking PVDF-HFP as the polymer electrolyte as an example, the preparation method of the all-solid-state battery is as follows: (1) Take the porous framework of the solid electrolyte prepared in this invention and spread it on the surface of the positive electrode sheet, and press it together; (2) Prepare a polymerization precursor liquid composed of PVDF-HFP monomer, lithium salt and thermal initiator, and vacuum wet the porous framework of the solid electrolyte for 3 min; (3) Heat at 55℃ for 30 min to completely solidify the PVDF-HFP monomer in the pores of the porous framework of the solid electrolyte. At this time, the polymer electrolyte PVDF-HFP is integrated with the porous framework of the solid electrolyte and the positive electrode interface; (4) Stack the negative electrode, add an insulating pad with a thickness of 0.5 mm, and apply a static pressure of 0.4 MPa to pre-bond the solid interface; (5) Seal with a hydraulic sealing machine to obtain a CR2032 button battery, wherein: the sealing pressure is 4.5 MPa and the battery is left to stand at room temperature for 12 h after sealing. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 In Figure A: A is a SEM image of the cross-section of the porous framework of the solid electrolyte obtained in Example 8; BD are SEM images in Figure A transitioning from the side away from the substrate to the side closer to the substrate. Figure 2 In Figure 8: A is a SEM image of the porous framework of the solid electrolyte obtained in Example 8; B is a SEM image of a certain channel in Figure A; C is a composite solid electrolyte film obtained in Example 3; and D is an overall view of Figure C. Figure 3 In the image: A is a SEM image of LiNbO3 powder doped with PVDF-HFP, B is a magnified schematic diagram of a part of A, and C is an overall view of the electrolyte membrane formed using the ordinary powder doping system shown in A. Figure 4 This is a 3D structural schematic diagram of the preparation apparatus used in each embodiment; Figure 5 for Figure 4 Schematic diagram of the structure of the intermediate sintering unit; Figure 6 This is a flowchart illustrating the preparation method proposed in this invention. Figure 7 This is a schematic diagram of small and large cracks used to determine the pass rate of the film layer. Figure 8 The surface condition of the substrate (specification A) used in Example 8 and the substrate (specification B) used in Example 25 after being used 5 times; Figure 9 The results of the chronocurrent test for solid-state battery A are shown. Figure 10 The results of the chronocurrent test for solid-state battery A2; Figure 11 The results of the chronocurrent experiment for solid-state battery B; Figure 12 The results of the chronocurrent experiment for solid-state battery C; Figure 13 A comparison chart of LSV curves for solid-state batteries A, A2, B, and C; Figure 14 A comparison chart of the cycle performance of solid-state batteries A, A2, B, and C; Figure 15A comparison chart of the charge-discharge performance of solid-state batteries A, A2, B, and C at 60℃.

[0026] In the figure: 1. Unwinding unit; 2. Coating unit; 3. Sintering unit; 31. Carbon heating substrate; 32. Thermocouple; 33. Temperature sensor; 34. Glove box; 4. Cooling unit; 5. Demolding unit; 51. Scraping mechanism; 6. Rewinding unit; 7. Substrate; 8. Wet film. Detailed Implementation

[0027] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0028] The following examples and comparative examples illustrate the preparation apparatus used in preparing the porous framework of solid electrolytes. Figure 4 and Figure 5 As shown: It includes an unwinding unit 1, a coating unit 2, a sintering unit 3, a cooling unit 4, a demolding unit 5, and a winding unit 6 arranged in sequence; The unwinding unit 1 unwinds the substrate 7 to continuously feed it, including an unwinding roller wound with the substrate 7. The unwinding roller rotates at a certain speed to achieve continuous feeding of the substrate 7. Both surfaces of the substrate 7 are coated with an isolation protective layer, which is a boron nitride coating. The substrate 7 has a thickness of 0.1-0.5mm and meets the following requirements: thermal conductivity ≥80W / (m•K) and areal density 80-170g / m³. 2 The substrate 7 has a tensile strength ≥ 500 MPa, an elastic modulus ≥ 210 GPa, and an elongation at break ≥ 1.5%; preferably, the substrate 7 has a tensile strength ≥ 600 MPa, an elastic modulus ≥ 240 GPa, and an elongation at break ≥ 1.7%; the substrate 7 has a carbon content ≥ 99%, ash content ≤ 500 ppm, Fe ≤ 50 ppm, and S ≤ 0.001%, preferably ash content ≤ 400 ppm and Fe ≤ 20 ppm, to ensure that harmful impurities are not introduced into the solid electrolyte membrane during the ultrafast sintering process and to prevent short circuits in the battery cell; The coating unit 2 is a prior art, such as an extrusion coating device or a transfer coating device, which continuously coats the solid electrolyte precursor on the substrate 7, thereby forming a wet film 8 on one surface of the substrate 7. The coating unit 2 is also equipped with a coating quality inspection mechanism (prior art, not shown in the figure). Sintering unit 3 primarily sintersulates the wet film 8, i.e., Joule heat treatment, using carbothermal shock for rapid sintering to transform the solid electrolyte precursor into a porous framework for the solid electrolyte. Sintering unit 3 includes a glove box 34 and sintering components housed within it. The sintering components include a carbon heating substrate 31, thermocouples 32, and temperature sensors 33. The carbon heating substrate 31 can be any of carbon fiber plates, carbon plates, carbon cloth, or high-purity graphite plates. Before sintering, the carbon heating substrate 31 is ultrasonically cleaned with an organic solvent to ensure surface cleanliness. Thermocouples 32 and temperature sensors 33 are embedded within the carbon heating substrate 31 and uniformly distributed to ensure consistent surface temperatures in contact with the wet film. Working in conjunction with temperature sensor 33 and closed-loop control, the sintering temperature uniformity is maintained at ±5℃. The carbon heating substrate 31 has a volume resistivity of 0.01-0.5Ω•cm and a thickness of 5-15mm. The substrate 7 is located directly above the carbon heating substrate 31 and is 0-3mm away from it (preferably 0mm, i.e., the substrate 7 is in direct contact with the carbon heating substrate 31). When the wet film passes through the carbon heating substrate 31 of this specification at a linear velocity of 1-100mm / s, the carbon heating substrate 31 generates Joule heat when energized, which can rapidly heat the wet film to 800-2000℃ within 1-60s, thereby rapidly sintering the solid electrolyte precursor to the desired crystalline phase. Cooling unit 4 performs temperature-controlled cooling on the porous framework of the solid electrolyte, ensuring that the temperature of the porous framework is cooled to room temperature and forms a dry film at a certain cooling rate; specifically, the cooling rate of cooling unit 4 is 10. 2 -10 3 The temperature is controlled at ℃ / min and the temperature uniformity is controlled within ±5℃. Such technical parameter settings help the dry film to release thermal stress for a sufficient time, reduce thermal stress peaks, and avoid thermal shock cracking, warping defects, etc. caused by rapid cooling. For example, the cooling unit 4 is specifically a water cooling mechanism and / or an air cooling mechanism, and several uniformly distributed temperature sensors are installed in the cooling unit 4. Demolding unit 5 is used for demolding, that is, separating the solid electrolyte porous skeleton (i.e., dry film) and the substrate 7. The resulting solid electrolyte porous skeleton (hereinafter referred to as: porous skeleton) and the substrate 7 are wound up separately by winding unit 6. Specifically, it includes two floating rollers that can peel the dry film and the substrate 7. The floating rollers also play a tensioning role, so that the dry film and the substrate 7 maintain constant tension (preferably 10-15 N / m) during the winding process to prevent wrinkles or shrinkage. Demolding unit 5 also includes a scraping mechanism 51, which is specifically a scraper. The scraper is set close to the side of the substrate 7 coated with the solid electrolyte precursor. It can quickly scrape off the residual debris on the surface of the substrate 7 to avoid contamination of the production of subsequent batches of solid electrolyte porous skeletons. The winding unit 6 includes two winding sub-units: one winding unit for winding the dry film and the other winding unit for winding the substrate 7.

[0029] The following are the process flows for preparing porous frameworks of solid electrolytes in each embodiment and comparative example. Figure 6 As shown, the process includes the following steps in sequence: unwinding, coating, sintering, cooling, demolding, and rewinding.

[0030] 1. Discussion on the influence of high-dielectric material precursor type on the electrochemical performance of composite solid electrolyte thin films Example 1

[0031] The porous framework of the solid electrolyte was prepared according to the following procedure: S1. BaTiO3 with a particle size of about 200 nm is uniformly mixed with a 1:1 volume ratio of N,N-dimethylformamide and acetone as a mixed solvent and a binder of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP, with a molar ratio of VDF to HFP of 9:1) to prepare a casting slurry. The addition amounts of BaTiO3, mixed solvent, and binder are 20wt%: 5wt%: 75wt% respectively. S2. The casting paste is coated onto one surface of the substrate 7 to form a uniform wet film, and the coating thickness of the wet film is controlled to be 100 μm; the substrate 7 is a carbon cloth with a thickness of 0.2 mm and meets the following requirements: thermal conductivity of 120 W / (m•K) and areal density of 130 g / m³. 2 Tensile strength ≥ 2500 MPa, elastic modulus 250 GPa, elongation at break ≥ 1.7%; carbon content of base material 7 ≥ 99.6%, ash content ≤ 500 ppm, Fe ≤ 50 ppm, S ≤ 0.001%; S3. A 10mm thick carbon fiber plate with a volume resistivity of 0.3Ω•cm is placed inside the glove box. The substrate 7 moves at a speed of 50mm / s relative to the carbon fiber plate, and the side of the substrate 7 without a wet film is in contact with the carbon fiber plate. A current density of 110A / cm is applied. 2 The DC current heats the wet film to 1350℃ within 3s and then continues to sinter for 15s, with a heating rate of 450℃ / s. After Joule heat treatment, the wet film becomes a dry film. S4. After the dry film cools, it is peeled off from the substrate 7 to obtain a solid electrolyte porous framework: the porosity of the solid electrolyte porous framework is distributed in a gradient in the thickness direction, with a porosity of 61% on the side close to the substrate 7 and 83% on the opposite side, an average pore size of 97 nm, and a total thickness of 25 μm (Note: When measuring porosity, a cross-section in the thickness direction of the solid electrolyte porous framework is taken, and the cross-section is divided into three equal parts: upper, middle, and lower. The porosity at 10 different positions in the upper and lower parts is measured by SEM, and the average value is taken as the final porosity; the same applies below). The composite solid electrolyte membrane was prepared as follows: VDF and HFP were mixed in a 9:1 molar ratio and dissolved in DMF. The monomer concentration in the monomer solution was 20 wt%. Then, 0.5 wt% AIBN initiator was added and mixed well. LiTFSI was then added to make the LiTFSI concentration 1 M (M represents mol / L) to obtain a polymerization precursor solution. The polymerization precursor solution was vacuum-impregnated into the porous framework of the solid electrolyte for 3 min, and then heated at 55 °C for 30 min to completely solidify the monomer inside the pores in situ. The membrane was then immersed in a methanol solution for 48 h to replace DMF, and then vacuum-dried at 60 °C. Finally, it was hot-pressed at 10 MPa at 120 °C for 5 min to obtain the composite solid electrolyte membrane with a mass ratio of PVDF-HFP to the porous framework of the solid electrolyte of 2:1.

[0032] Example 2

[0033] Compared with Example 1, the high dielectric precursor was changed from "BaTiO3" to "SrTiO3", while all other aspects remained the same as in Example 1.

[0034] Example 3

[0035] Compared with Example 1, the high dielectric precursor was changed from "BaTiO3" to "LiNbO3", while all other aspects remained the same as in Example 1.

[0036] The porosity of the obtained solid electrolyte porous framework is gradient-distributed in the thickness direction, with a porosity of 51% on the side near the substrate 7 and 89% on the opposite side, an average pore size of 70 nm, and a total thickness of 28 μm.

[0037] Example 4

[0038] Compared with Example 1, the high dielectric material precursor was changed from "BaTiO3" to "KNbO3", while all other aspects remained the same as in Example 1.

[0039] Example 5

[0040] Compared with Example 1, the high dielectric material precursor was changed from "BaTiO3" to "Ta2O5", while all other aspects remained the same as in Example 1.

[0041] Comparative Example 1 Preparation of pure polymer electrolyte: PVDF-HFP (obtained by copolymerizing VDF and HFP at a molar ratio of 9:1) was dry-mixed with LiTFSI (mass ratio of PVDF-HFP to LiTFSI was 3:1), then placed into a mold and hot-pressed into a film using a hot press. The film was then sintered in a muffle furnace at 1350°C for 15 seconds. Compared to Example 1, no high-dielectric precursor material was added when preparing the porous framework of the solid electrolyte; all other aspects remained the same as in Example 1. The specific composition of the casting slurry in Examples 1-5 and Comparative Example 1 is shown in Table 1. For ease of listing, "high-dielectric precursor material" is abbreviated as "HDO", "solvent" as "L", "binder" as "BM", "N,N-dimethylformamide" as "DMF", "acetone" as "ACE", and "polyvinylidene fluoride-hexafluoropropylene" as "PVDF-HFP".

[0042] The electrochemical performance of the composite solid electrolyte films prepared in Examples 1-5 and Comparative Example 1 was tested and compared with that of the corresponding ordinary powder doping system (i.e., PVDF-HFP powder, LiTFSI, and high dielectric precursor were dry mixed evenly in a mass ratio of 6:2:2, then loaded into a mold, hot-pressed into a film by a hot press, and then sintered in a muffle furnace at 1350°C for 15s). The specific results are shown in Table 2 (room temperature 25°C) and Table 3 (high temperature 60°C).

[0043] Table 1. Composition of cast slurry in Examples 1-5 and Comparative Example 1

[0044] Table 2. Electrochemical performance of the composite solid electrolyte films prepared in Examples 1-5 and Comparative Example 1 at room temperature (25°C)

[0045] Table 3. Electrochemical performance of the composite solid electrolyte films prepared in Examples 1-5 and Comparative Example 1 at a high temperature of 60°C.

[0046] As shown in Tables 2 and 3, for the same high-dielectric material precursor, the system of this invention (solid electrolyte porous framework + in-situ polymer electrolyte) exhibits significantly higher ionic conductivity and lower bulk impedance and electrode interface impedance at both room temperature (25℃) and high temperature (60℃) compared to the ordinary powder doping system (inorganic powder + polymer electrolyte). This is because the porous structure with a gradient porosity distribution within the solid electrolyte porous framework of this invention eliminates powder agglomeration and constructs long-distance ion transport channels. Figure 2 and Figure 3 As shown: Taking the porous framework of solid electrolyte with added LiNbO3 obtained in Example 3 as an example, the composite solid electrolyte film formed by in-situ polymerization and curing of polymer electrolyte PVDF-HFP on it has a smoother and more uniform surface and no particle agglomeration phenomenon compared with the electrolyte film formed by using a common powder doping system.

[0047] The system of this invention is applicable to all high-dielectric oxides, with LiNbO3 exhibiting the best overall performance. All high-dielectric oxides used in the system of this invention can sustainably achieve lithium salt dissociation, accelerated lithium-ion migration, and polysulfide anchoring, making it suitable for all-solid-state lithium-sulfur batteries operating in both room temperature and high temperature environments.

[0048] 2. Discussion on Joule heat treatment conditions (1) In Examples 6-12 below, LiNbO3 was used as a high dielectric material precursor. The current density during Joule heat treatment was used as a single variable to investigate the effect of current density on the grain size of the porous framework of the solid electrolyte and the electrochemical performance of the composite solid electrolyte film.

[0049] Example 6

[0050] Compared with Example 1, the specific conditions for Joule heat treatment are as follows: (1) a high-purity graphite plate with a thickness of 10 mm, a volume resistivity of 0.02 Ω•cm, a carbon content of ≥99.95%, and an ash content of ≤300ppm is used as the carbon heating substrate; (2) a substrate 7 with a thickness of 0.3 mm and an areal density of 120 g / m³ is used. 2 1. Tensile strength is 3200MPa, carbon content is ≥99.9%, and ash content is ≤400ppm; (3) The applied DC current density is 80A / cm 2 The conveyor belt speed was 30 mm / s, and the wet film was heated to 1200°C and sintered for 15 seconds at a heating rate of 320°C / s. All other aspects were the same as in Example 1.

[0051] Example 7

[0052] Compared to Example 6, the DC current density during Joule heat treatment was reduced from 110 A / cm². 2 Adjusted to 100A / cm 2The wet film was heated to 1200°C at a heating rate of 410°C / s and sintered for 15s, with the rest being consistent with Example 1.

[0053] Example 8

[0054] Compared to Example 6, the DC current density during Joule heat treatment was reduced from 110 A / cm². 2 Adjusted to 120A / cm 2 The wet film was heated to 1200°C at a heating rate of 500°C / s and sintered for 15s, with the rest being consistent with Example 1.

[0055] The microstructure of the obtained solid electrolyte porous framework is as follows Figure 1 and Figure 2 As shown: the porosity on the side closer to the substrate 7 is 70%, the porosity on the side farther from the substrate 7 is 81%, the average pore size is 74nm, and the total thickness is 30μm.

[0056] Example 9

[0057] Compared to Example 6, the DC current density during Joule heat treatment was reduced from 110 A / cm². 2 Adjusted to 140A / cm 2 The wet film was heated to 1200°C at a heating rate of 590°C / s and sintered for 15s, with the rest being consistent with Example 1.

[0058] Example 10

[0059] Compared to Example 6, the DC current density during Joule heat treatment was reduced from 110 A / cm². 2 Adjusted to 160A / cm 2 The wet film was heated to 1200°C at a heating rate of 680°C / s and sintered for 15s, with the rest being consistent with Example 1.

[0060] Example 11

[0061] Compared to Example 6, the DC current density during Joule heat treatment was reduced from 110 A / cm². 2 Adjusted to 50A / cm 2 The wet film was heated to 1200°C at a heating rate of 190°C / s and sintered for 15s, with the rest being consistent with Example 1.

[0062] Example 12

[0063] Compared to Example 6, the DC current density during Joule heat treatment was reduced from 110 A / cm². 2 Adjusted to 200A / cm 2The wet film was heated to 1200°C at a heating rate of 800°C / s and sintered for 15s, with the rest being consistent with Example 1.

[0064] The relevant performance test results of Examples 6-12 are shown in Table 4. Among them, the membrane layer qualification rate test is as follows: (1) Calculation formula: membrane layer qualification rate = number of qualified membranes / total number of sampled membranes × 100%; (2) Judgment criteria: no through cracks, no holes, no peeling, no large-area edge damage; the length of small dispersed cracks is < 2mm; the above requirements are met to be qualified membranes; (3) Sampling: along the length of the roll material, cut 10cm×10cm standard sample every 10cm; 20 samples are continuously sampled for a single process; (4) as Figure 7 As shown: When judging, the small crack shown in the left figure is judged using a microscope, and the larger crack shown in the right figure is judged using a film ruler.

[0065]

[0066] As can be seen from Table 4, the current density of direct current is between 50-200 A / cm². 2 The obtained composite solid electrolyte film has a high film yield, and the preferred current density is 100-140 A / cm². 2 120A / cm is a preferred choice 2 At this point, the heating rate reaches 500℃ / s, which can take into account both the crystallinity and grain size of the porous framework of the solid electrolyte, thereby achieving optimal ion transport performance.

[0067] (2) In Examples 13-18 below, LiNbO3 was used as a high dielectric material precursor. The sintering temperature during Joule heat treatment was used as a single variable to investigate the effect of sintering temperature on the grain size of the porous framework of the solid electrolyte and the electrochemical performance of the composite solid electrolyte film.

[0068] Example 13

[0069] Compared to Example 8, the sintering temperature was adjusted to 1000℃, while all other aspects remained the same as in Example 8.

[0070] Example 14

[0071] Compared to Example 8, the sintering temperature was adjusted to 1100°C, while all other aspects remained the same as in Example 8.

[0072] Example 15

[0073] Compared to Example 8, the sintering temperature was adjusted to 1300°C, while all other aspects remained the same as in Example 8.

[0074] Example 16

[0075] Compared to Example 8, the sintering temperature was adjusted to 1400°C, while all other aspects remained the same as in Example 8.

[0076] Example 17

[0077] Compared to Example 8, the sintering temperature was adjusted to 800°C, while all other aspects remained the same as in Example 8.

[0078] Example 18

[0079] Compared to Example 8, the sintering temperature was adjusted to 2000℃, while all other aspects remained the same as in Example 8.

[0080] The relevant performance test results of Examples 13-18 are shown in Table 5.

[0081]

[0082] As shown in Table 5, when the sintering temperature is within the range of 800-2000℃, the crystallinity of the obtained solid electrolyte porous framework is above 70%, and the film qualification rate of the composite solid electrolyte film is above 72%. Within the above sintering range, lower sintering temperatures lead to insufficient sintering and lower crystallinity of the solid electrolyte porous framework, resulting in lower conductivity of the obtained composite solid electrolyte film. Higher sintering temperatures, on the other hand, can lead to excessive grain growth and coarsening, as well as increased interfacial impedance. The preferred sintering temperature is 1100-1300℃, and particularly preferred is 1200℃. At this temperature, high crystallinity of LiNbO3 can be achieved while inhibiting excessive grain growth and ensuring unobstructed ion transport channels.

[0083] (3) In Examples 19-24 below, LiNbO3 was used as a high dielectric material precursor. The belt speed of the substrate relative to the carbon heating substrate during Joule heat treatment was used as a single variable to investigate the effect of belt speed on the grain size of the porous framework of the solid electrolyte and the electrochemical performance of the composite solid electrolyte film.

[0084] Example 19

[0085] Compared with Example 8, the tape speed of the substrate 7 relative to the carbon fiber plate is 10 mm / s and the effective sintering time is 44.5 s, while the rest are the same as in Example 8.

[0086] Example 20

[0087] Compared with Example 8, the tape speed of the substrate 7 relative to the carbon fiber plate is 20 mm / s and the effective sintering time is 22.4 s, while the rest are the same as in Example 8.

[0088] Example 21

[0089] Compared with Example 8, the tape speed of the substrate 7 relative to the carbon fiber plate is 40 mm / s and the effective sintering time is 11 s, while the rest are the same as in Example 8.

[0090] Example 22

[0091] Compared with Example 8, the tape speed of the substrate 7 relative to the carbon fiber plate is 50 mm / s and the effective sintering time is 8.8 s, while the rest are the same as in Example 8.

[0092] Example 23

[0093] Compared with Example 8, the tape speed of the substrate 7 relative to the carbon fiber plate is 1 mm / s and the effective sintering time is 442 s, while the rest are the same as in Example 8.

[0094] Example 24

[0095] Compared with Example 8, the tape speed of the substrate 7 relative to the carbon fiber plate is 100 mm / s and the effective sintering time is 4.4 s, while the rest are the same as in Example 8.

[0096] The relevant performance test results of Examples 19-24 are shown in Table 6.

[0097]

[0098] As can be seen from Table 6, when the conveyor speed of the substrate 7 relative to the carbon fiber plate is controlled at 1-100 mm / s, the yield of the composite solid electrolyte film is relatively high. Within the above conveyor speed range, although the sintering is sufficient at lower conveyor speeds, the production efficiency is low and the film is prone to over-sintering defects. Higher conveyor speeds will lead to insufficient sintering, poor film surface temperature uniformity, and a significant decrease in electrochemical performance. The preferred conveyor speed is 20-40 mm / s, and particularly preferred is 30 mm / s. At this speed, the composite solid electrolyte film has the best overall performance, which can achieve high-efficiency roll-to-roll continuous production while ensuring the sintering uniformity and performance consistency of the entire film.

[0099] (4) In the following Examples 25, 26 and Comparative Example 2, LiNbO3 was used as a high dielectric material precursor. The specifications of the substrate 7 during Joule heat treatment were taken as a single variable to investigate the influence of the specifications of the substrate 7 on the grain size of the porous framework of the solid electrolyte and the electrochemical performance of the composite solid electrolyte film.

[0100] Example 25

[0101] The substrate 7 used in Example 8 is referred to as "Specification A". Compared with Example 8, "Specification A" is adjusted to "Specification B". The specific technical parameters of "Specification B" are: substrate 7 thickness 0.1 mm, areal density 80 g / m³. 2The tensile strength is 1800MPa, the carbon content is ≥99.5%, the ash content is ≤800ppm, and the rest are consistent with Example 8.

[0102] The porosity of the obtained solid electrolyte porous framework is gradient-distributed in the thickness direction, with a porosity of 67% on the side near the substrate 7 and 70% on the opposite side, an average pore size of 62 nm, and a total thickness of 28 μm.

[0103] Example 26

[0104] The substrate 7 used in Example 8 is referred to as "Specification A". Compared with Example 8, "Specification A" is adjusted to "Specification C". The specific technical parameters of "Specification C" are: substrate 7 thickness 0.5 mm, areal density 170 g / m³. 2 The tensile strength is 4500MPa, the carbon content is ≥99.9%, the ash content is ≤400ppm, and the rest are consistent with Example 8.

[0105] The porosity of the obtained solid electrolyte porous framework is gradient-distributed in the thickness direction, with a porosity of 59% on the side near the substrate 7 and 84% on the opposite side, an average pore size of 50 nm, and a total thickness of 32 μm.

[0106] Comparative Example 2 The substrate 7 used in Example 8 is referred to as "Specification A". Compared with Example 8, "Specification A" is adjusted to "Specification D". The specific technical parameters of "Specification D" are: substrate 7 thickness 0.2 mm, areal density 100 g / m³. 2 The tensile strength is 1200MPa, the carbon content is ≥99%, the ash content is ≤2000ppm, the Fe content is ≥100ppm, and the rest are consistent with Example 8.

[0107] The relevant performance test results of Examples 25, 26, and Comparative Example 2 are shown in Table 7.

[0108]

[0109] As shown in Table 7: the thin substrate shown in specification B has a high film breakage rate and poor cycle life due to difficulty in demolding; the thick substrate shown in specification C is easy to demold, and the film integrity and cycle life are significantly improved compared to specification B; the substrate shown in specification A has the best overall performance, with excellent electrochemical performance, and is extremely easy to demold, resulting in good film integrity and long cycle life; Figure 8 As shown: After 5 cycles of use, the substrate shown in specification A remained intact, while the thinner substrate shown in specification B exhibited obvious multi-directional cracks. Therefore, the optimal specifications for substrate 7 are a thickness of 0.3 mm and a surface density of 120 g / m³. 2With a tensile strength of 3200MPa, carbon content ≥99.9%, and ash content ≤400ppm, it meets the mechanical requirements of continuous roll-to-roll production while ensuring heat transfer efficiency and product purity.

[0110] (5) In Examples 27 and 28 below, LiNbO3 was used as a high dielectric material precursor. The specifications of the carbon heating substrate during Joule heat treatment were taken as a single variable to investigate the influence of the specifications of the carbon heating substrate on the grain size of the porous framework of the solid electrolyte and the electrochemical performance of the composite solid electrolyte film.

[0111] Example 27

[0112] Compared with Example 8, the "high-purity graphite plate" was changed to a "conductive carbon plate". The technical parameters of the conductive carbon plate are: thickness 5mm, volume resistivity 0.01Ω•cm, carbon content ≥99%, ash content ≤1000ppm, and the rest are consistent with Example 8.

[0113] Example 28

[0114] Compared with Example 8, the "high-purity graphite plate" was changed to "carbon fiber plate". The technical parameters of the carbon fiber plate are: thickness 15mm, volume resistivity 0.5Ω•cm, carbon content ≥99.5%, ash content ≤800ppm, and the rest are consistent with Example 8.

[0115] The relevant performance test results of Examples 27 and 28 are shown in Table 8.

[0116]

[0117] As can be seen from Table 8, the optimal choice for carbon heating substrate is a 10mm thick high-purity graphite plate, which can achieve stable second-level heating, while ensuring the temperature uniformity of the entire film layer, and the impurity content is extremely low, so it will not contaminate the solid electrolyte.

[0118] In summary, through five series of Joule heat treatment condition optimization experiments, the present invention yields the preferred conditions and optimal values ​​for Joule heat treatment, as shown in Table 9.

[0119]

[0120] 3. Battery performance verification 3.1 Battery fabrication and experimental process The cathode materials used were two mainstream types: commercially available NCM811 high-nickel ternary cathode and LFP lithium iron phosphate cathode. Separate samples were prepared with unified process parameters: the mass ratio of active material, conductive carbon (SP), and binder (PVDF) was 90:6:4. NMP was used as the solvent, and the mixture was stirred at high speed to form a homogenized slurry. The slurry was then coated onto the surface of the aluminum current collector using a doctor blade, pre-dried at 80℃ for 120 min, and then vacuum-baked at 120℃ for 12 h to remove residual solvent. The compacted density was 3.4 g / cm³ for NCM811. 3 LFP is 2.3 g / cm³ 3 ; Stamped 12mm diameter positive electrode discs, with an electrode surface loading of 2.0mAh / cm². 2 ,spare.

[0121] The negative electrode is SiO2-based. The process parameters are: the mass ratio of SiO2, conductive carbon and CMC binder is 85:8:7. Copper foil is coated with aqueous slurry, vacuum dried and rolled, and then punched into 14mm negative electrode discs for later use.

[0122] Solid-state battery assembly: (1) Solid-state battery A: Take the porous framework of solid electrolyte prepared in Example 8, spread it on the surface of the positive electrode sheet, the positive electrode active material is high nickel ternary positive electrode NCM811, and press it together; Prepare in-situ polymerization precursor solution: Mix VDF and HFP in a molar ratio of 9:1 and dissolve them in DMF. The concentration of monomer in the monomer solution is 20wt%. Then add 0.5wt% AIBN initiator and mix well. Then add LiTFSI to make the concentration of LiTFSI 1. M; The precursor liquid of the in-situ polymerization is vacuum-wetted into the porous framework of the solid electrolyte for 3 min, and then heated at 55℃ for 30 min. The monomers inside the pores are completely solidified in-situ. The mass ratio of the composite electrolyte PVDF-HFP to the porous framework of the solid electrolyte is 2:1, so as to achieve the integrated bonding of the composite electrolyte with the framework and the positive electrode interface; the negative electrode is stacked, an insulating gasket with a thickness of 0.5 mm is added, and a static pressure of 0.4 MPa is applied to pre-bond the solid interface; the CR2032 button battery is packaged by a hydraulic sealing machine with a packaging pressure of 4.5 MPa. After packaging, it is left to stand at room temperature for 12 h to complete the interface wetting, in preparation for subsequent electrochemical testing; (2) The assembly method of solid battery A2 is similar to that of solid battery A, but the positive electrode active material is adjusted to lithium iron phosphate LFP; (3) The positive and negative electrodes of solid battery B and solid battery C are consistent with those of solid battery A. The difference lies in the structure of the electrolyte layer: the electrolyte layer of solid battery B is obtained by directly doping LiNbO3 powder into the polymer, and the electrolyte layer of solid battery C is pure polymer.

[0123] 3.2 Battery Electrochemical Performance Testing Electrochemical impedance spectroscopy (EIS): Using a Salartron electrochemical testing platform, an AC voltage signal with an amplitude of 5mV is applied to the two electrodes of the battery. The frequency of the AC signal is continuously changed from a high frequency of 1MHz to a low frequency of 0.1Hz. The battery system exhibits different AC current signal responses at different frequencies, allowing the calculation of the battery impedance at different frequencies. By analyzing the impedance changes, information such as the ionic conductivity and interfacial impedance of the solid electrolyte can be obtained.

[0124] Constant current charge and discharge test: Using the Beidou charge and discharge platform, constant current charge and discharge is performed by controlling the magnitude and direction of the current between the two electrodes of the battery, and the voltage change curve between the positive and negative electrodes over time is recorded. Information such as charge and discharge voltage curves, charge and discharge capacity and cycle stability of different battery systems can be obtained.

[0125] Potential scanning test: Using the Salartron electrochemical testing platform, the voltage between the two electrodes of the battery is changed at a certain rate. By recording the change curve of the current between the two electrodes with voltage (or time), the battery system is analyzed to determine whether an electrochemical reaction occurs and to determine the voltage range in which the electrochemical reaction occurs.

[0126] 3.3 Results of Comprehensive Electrochemical Performance Tests of the Battery Through such Figures 9-12 The chronocurrent test results and Evans formula are shown in Table 10. The lithium-ion transference number of the four solid-state batteries is calculated. The composite electrolyte film structure obtained by in-situ curing polymer electrolyte with porous framework of solid electrolyte in Example 8 of this invention is adapted to the volume expansion characteristics of SiO2 negative electrode, which greatly improves the lithium transference number. Relying on the interface modification effect of LiNbO3, the electrochemical withstand voltage window is widened, the volume deformation of SiO2 lithium insertion and extraction is alleviated, and it is adapted to the use requirements of high nickel high voltage positive electrode + silicon oxygen negative electrode long-term energy storage cell.

[0127]

[0128] In Table 10, the electrochemical stability window was obtained through linear voltammetric scanning (LSV) testing. The test conditions were 60℃, scan rate 5mV / s, and voltage scan range 2.0-5.0V. The LSV curves are shown below. Figure 13As shown: (1) In solid-state battery A, the porous framework of LiNbO3 solid electrolyte has high dielectric and oxidation resistance characteristics, which can block PVDF-HFP polymer from directly contacting the high voltage positive electrode surface and inhibit polymer oxidation and decomposition. The NCM811 matching system window can reach 4.85V, and the LFP matching system can reach 4.90V. It can be fully adapted to the high voltage high nickel ternary positive electrode charging and discharging conditions, with no electrolyte decomposition and no interface side oxidation reaction; (2) In solid-state battery B, due to the use of ordinary powder doping system, the nano LiNbO3 powder is unevenly dispersed and has agglomeration defects. Therefore, it cannot fully cover the positive electrode interface. Under high voltage, the polymer is easily oxidized and decomposed. The window is only 4.20V. Under high voltage charging conditions, the electrolyte is easily degraded; (3) In solid-state battery C, due to the lack of inorganic oxidation-resistant filler, PVDF-HFP is easily oxidized under high voltage. The electrochemical window is only 3.85V. It can only be adapted to low voltage graphite negative electrode system and cannot be adapted to high voltage NCM811+SiO2 composite cell system. Clearly, the solid-state battery using the porous framework of the solid electrolyte of this invention exhibits the best electrochemical performance.

[0129] 3.4 Battery Long Cycle Stability Test like Figure 14 As shown: Solid-state battery A, with a capacity retention rate of up to 87.5% after 500 cycles, and an interface impedance increase of only 14% after cycling, demonstrates that the porous framework of the solid electrolyte can buffer the volume expansion of lithium intercalation and deintercalation at the SiO2 negative electrode, with no cracking at the solid-solid interface and controllable interface side reactions; Solid-state battery A2, with a capacity retention rate of up to 90.2% after 500 cycles, and an interface impedance increase of only 11% after cycling, shows excellent LFP positive electrode structure stability, and the solid electrolyte porous framework synergistically releases the deformation stress of the SiO2 negative electrode, with uniform SEI film growth at the interface and minimal increase in cycle polarization, making it suitable for long-life solid-state energy storage cells; Solid-state battery B, due to the inability of the powder to adapt to the deformation stress of SiO2, is prone to interface peeling, resulting in a precipitous capacity decrease after 290 cycles, with a capacity retention rate of only 53.2% after 500 cycles, and severe fragmentation of the negative electrode interface; Solid-state battery C, due to insufficient polymer mechanical strength, cannot buffer SiO2 expansion, resulting in interface debonding failure after 155 cycles, severe polarization, and inability to achieve long-term cycling. Clearly, the solid-state battery using the porous framework of the solid electrolyte of this invention exhibits the best cycle performance.

[0130] 3.5 Battery Rate Charge / Discharge Performance Test (60℃) like Figure 15As shown: Solid-state battery A retains 80% of its capacity at 0.5C discharge rate and 68% at 1C rate; Solid-state battery B, with its traditional powder-doped electrolyte exhibiting hindered ion transport and high interfacial impedance, retains less than 41% of its capacity at 1C rate; Solid-state battery C, with its polymer electrolyte exhibiting extremely poor mechanical and ion conductivity, suffers from a precipitous capacity decay at high rates. Furthermore, the LFP cathode exhibits superior structural stability compared to the NCM811 cathode, and when combined with the porous framework of the solid-state electrolyte obtained in Example 8, it demonstrates optimal high-rate performance. It is evident that the hierarchically interconnected gradient channels within the porous framework of the solid-state electrolyte can rapidly conduct lithium ions, while simultaneously leveraging the rigid LiNbO3 framework to share the lithium insertion / extraction expansion stress of the SiO2 anode, resulting in low polarization at high current.

[0131] 3.6 Interface stability and side reaction suppression performance Assemble a SiO2||NCM811 half-cell, 0.1 mA / cm 2 Constant current polarization test: The composite electrolyte film obtained in Example 8 maintained a stable polarization voltage of 31 mV, and after 1100 h of stable cycling, there was no interface peeling or continuous side reactions. In contrast, the composite electrolyte obtained using a traditional powder doping system had a polarization voltage of 82 mV, and after 530 h of cycling, a thick SEI film continuously formed at the negative electrode interface, resulting in a continuous surge in impedance. It is evident that the porous framework of the solid electrolyte of this invention can uniformly control the lithium-ion flux, optimize the morphology of the SiO2 negative electrode SEI film, generate a dense and thin SEI, and suppress continuous side reactions at the negative electrode.

[0132] In summary, the performance comparison of solid-state batteries A, B, and C shows that the porous framework of the solid electrolyte prepared in this invention can eliminate the powder agglomeration problem present in traditional powder doping systems, promote the full play of the piezoelectric / paraelectric / lithium salt dissociation effect of high dielectric materials, thereby improving ionic conductivity, reducing interfacial impedance, and significantly improving long-cycle stability and interfacial stability.

[0133] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions, and variations to the above embodiments within the scope of the present invention. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples.

Claims

1. A porous framework for a solid electrolyte, characterized in that: The porosity within it exhibits a gradient distribution, with 50%-70% porosity on one side and 70%-90% porosity on the opposite side.

2. The porous framework of the solid electrolyte according to claim 1, characterized in that: The average pore size is 50-100 nm.

3. The porous framework of the solid electrolyte according to claim 1, characterized in that: Total thickness 25-35μm.

4. A method for preparing a porous framework of a solid electrolyte as described in any one of claims 1-3, characterized in that: The following steps are included: S1. The high dielectric material precursor is uniformly mixed with solvent and binder to prepare a casting slurry; S2. The casting paste is coated onto one surface of the substrate to form a wet film; S3. Place the substrate obtained in the previous step in an anhydrous and oxygen-free atmosphere, and apply Joule heat treatment to the side of the substrate that is not coated with the casting paste. The wet film becomes a dry film after Joule heat treatment. S4. After the dry film cools down, peel it off from the substrate to obtain the final product.

5. The method for preparing a porous framework for a solid electrolyte according to claim 4, characterized in that: In step S3, the Joule heat treatment temperature is 800-2000℃; Preferably, the heating rate of the Joule heat treatment is 190-800℃ / s; Preferably, the Joule heat treatment uses a carbon heating substrate with a thickness of 5-15 mm and a volume resistivity of 0.01-0.5 Ω•cm, and applies a current density of 50-200 A / cm. 2 DC current.

6. The method for preparing a porous framework for a solid electrolyte according to claim 5, characterized in that: The side of the substrate without the wet film faces the carbon heating substrate and the distance between the substrate and the carbon heating substrate does not exceed 3mm. Preferably, both surfaces of the substrate are coated with an isolation and protective layer; more preferably, the isolation and protective layer is a boron nitride coating or an aluminum oxide coating; Preferably, the substrate has a thermal conductivity ≥80 W / (m•K) and an areal density of 80-170 g / m³. 2 The substrate has a tensile strength ≥ 500 MPa, an elastic modulus ≥ 210 GPa, and an elongation at break ≥ 1.5%; more preferably, the substrate has a tensile strength ≥ 600 MPa, an elastic modulus ≥ 240 GPa, and an elongation at break ≥ 1.7%. Preferably, the carbon content of the substrate is ≥99%, the ash content is ≤500ppm, the Fe content is ≤50ppm, and the S content is ≤0.001%; ​​more preferably, the ash content of the substrate is ≤400ppm and the Fe content is ≤20ppm.

7. The method for preparing a porous framework for a solid electrolyte according to claim 5, characterized in that: During the Joule heat treatment, the conveyor speed of the substrate relative to the carbon heating substrate is 1-100 mm / s, and the effective sintering time is 1-500 s; Preferably, the conveyor speed of the substrate relative to the carbon heating substrate is 20-40 mm / s, and the effective sintering time is 10-25 s.

8. The method for preparing a porous framework for a solid electrolyte according to claim 1, characterized in that: In step S1, the mass percentage of each component in the casting slurry is as follows: high dielectric precursor 10wt%-30wt%, binder 2wt%-8wt%, solvent 62wt%-88wt%; Preferably, the coating thickness of the casting paste on the substrate is 50-150 μm; Preferably, the high-dielectric material precursor has a relative permittivity εr > 20 and a particle size of 20-500 nm; more preferably, the high-dielectric material precursor is selected from at least one of barium titanate, strontium titanate, lithium niobate, potassium niobate, lead titanate, lead zirconate titanate, and tantalum oxide. Preferably, the adhesive is selected from at least one of PAA, CMC, PVDF, and PVDF-HFP; Preferably, the solvent is selected from at least one of N,N-dimethylacetamide, acetone, and anhydrous ethanol.

9. A composite solid electrolyte thin film, characterized in that: Includes the solid electrolyte porous framework and polymer electrolyte as described in any one of claims 1-3; Preferably, the polymer electrolyte is a PVDF-HFP or / and PEO-based solid electrolyte, and the mass ratio of the polymer electrolyte to the porous framework of the solid electrolyte is (1-3):1; Preferably, the polymer electrolyte is formed by in-situ solidification of the corresponding polymerization precursor liquid within the porous framework of the solid electrolyte; Preferably, the polymer electrolyte is further doped with one or more of the following: sulfide solid electrolyte, phosphate solid electrolyte, and garnet-type solid electrolyte.

10. An all-solid-state battery, characterized in that: It includes a positive electrode, a negative electrode, and a composite solid electrolyte film as described in claim 9.

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