A method for preparing a self-supporting composite diatomaceous membrane and applications thereof

Abstract

A method for preparing a self-supporting silica composite separator and its application includes the following steps: (1) preparing two-dimensional porous silica nanosheets: 1.1 ion exchange exfoliation; 1.2 two-step acid etching; (2) preparing an electrospun composite separator: 2.1 preparing spinning solution; 2.2 preparing composite separator; the self-supporting silica composite separator is a three-dimensional interconnected fiber network structure, and the self-supporting silica composite separator is used as a separator for lithium metal batteries. This invention has the advantages of simple preparation method, three-dimensional interconnected hierarchical porous structure of the prepared self-supporting silica composite separator, high porosity, excellent thermal stability, high ionic conductivity and high lithium ion transport number, which can effectively uniform lithium ion flux, induce the formation of dense and stable LiF-rich SEI film, significantly inhibit lithium dendrite growth, and greatly improve the cycle life, rate performance and safety performance of lithium metal batteries.

Description

Technical Field

[0001] This invention relates to a composite membrane, and more particularly to a method for preparing a self-supporting silica composite membrane and its application. Background Technology

[0002] During repeated charging and discharging of lithium metal batteries, the deposition of lithium ions on the surface of the lithium metal anode is often uneven, which can easily induce uncontrolled growth of lithium dendrites. Lithium dendrites can not only puncture the separator and cause internal short circuits in the battery, but also continuously consume electrolyte and damage the solid electrolyte interface film, leading to reduced battery coulombic efficiency, shortened cycle life, and in severe cases, even causing safety problems such as thermal runaway.

[0003] As a crucial component of lithium metal batteries, the separator significantly impacts the battery's ion transport behavior, cycle stability, rate performance, and safety. While commonly used commercial polyolefin separators possess certain mechanical strength and chemical stability, they suffer from drawbacks such as poor electrolyte wettability, limited ion transport efficiency, insufficient thermal dimensional stability, and difficulty in effectively controlling lithium-ion flux distribution. In lithium metal battery systems, these defects can easily lead to uneven lithium deposition, exacerbated interfacial side reactions, and continuous lithium dendrite growth, making it difficult to meet the application requirements of long cycle life and high safety in lithium metal batteries.

[0004] Therefore, in view of the shortcomings of the prior art, the present invention provides a method for preparing a self-supporting silica composite membrane and its application. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a self-supporting silica composite separator and its application. This invention features a simple preparation method, a three-dimensional interconnected hierarchical porous structure in the prepared self-supporting silica composite separator, high porosity, excellent thermal stability, high ionic conductivity, and high lithium-ion transference number. It can effectively uniformly distribute lithium-ion flux, induce the formation of a dense and stable LiF-rich SEI film, significantly suppress lithium dendrite growth, and substantially improve the cycle life, rate performance, and safety performance of lithium metal batteries.

[0006] The technical solution of this invention: A method for preparing a self-supporting silica composite membrane, comprising the following steps: (1) Preparation of two-dimensional porous silica nanosheets: 1.1 Ion exchange stripping: Vermiculite crystals were dispersed in a saturated sodium chloride solution for ion exchange stripping, then transferred to a lithium chloride solution for secondary stripping. After dialysis to remove impurities, product A was obtained. 1.2 Two-step acid etching: Product A was subjected to two-step acid etching with hydrochloric acid, followed by centrifugation and freeze-drying to obtain two-dimensional porous silica nanosheets; (2) Preparation of electrospun composite membrane: 2.1 Preparation of spinning solution: Two-dimensional porous silica nanosheets were dispersed in a solvent, polyvinylidene fluoride was added, and the mixture was stirred to obtain a spinning solution; 2.2 Preparation of composite membrane: The spinning solution was used to prepare a fiber membrane on the receiving substrate by electrospinning. After vacuum drying and peeling, a silica self-supporting composite membrane was obtained.

[0007] In the aforementioned method for preparing a self-supporting silica composite membrane, step (1) 1.1 ion exchange exfoliation: 8-12 g of vermiculite crystals are dispersed in 250-350 mL of saturated NaCl solution, and exfoliated by stirring in an oil bath at 75-85°C for 24-28 h. After cooling, the mixture is dialyzed until no white precipitate is detected by 0.1-1 mol / L silver nitrate solution, and then filtered and washed. The filter cake is then added to 250-350 mL of saturated lithium chloride solution, and exfoliated by stirring at 75-85°C for 24-28 h. After cooling to 15-25°C, the mixture is filtered, washed, and dialyzed until no white precipitate is detected by 0.1-1 mol / L silver nitrate solution. The mixture is then vacuum filtered to obtain product A.

[0008] In the aforementioned method for preparing a self-supporting silica composite membrane, step (1) involves two steps of acid etching: 1.3–1.7 g of product A is added to 150–200 mL of 34–38 wt.% hydrochloric acid, stirred at 75–85°C for 12–14 h, and washed until the pH reaches 6.8–7; the membrane is then immersed again in 250–350 mL of 34–38 wt.% hydrochloric acid, stirred at 75–85°C for 12–14 h, and washed until the pH reaches 6.8–7; the membrane is then centrifuged at 800–1200 r / min for 8–12 min, and the supernatant is freeze-dried at -10–0°C for 24–26 h to obtain two-dimensional porous silica nanosheets.

[0009] In the aforementioned method for preparing the self-supporting silica composite membrane, the two-dimensional porous silica nanosheets have a thickness of 1.56–1.96 nm and a specific surface area of ​​225–230 m². 2 / g.

[0010] In the aforementioned method for preparing a self-supporting silica composite membrane, step (2) 2.1 involves preparing a spinning solution: 0.2–0.4 g of two-dimensional porous silica nanosheets are dispersed in 2–4 mL of N,N-dimethylformamide, and 0.05–0.1 g of polyvinylidene fluoride is added. The mixture is stirred at 800–1200 r / min for 24–28 h to obtain the spinning solution.

[0011] In the aforementioned method for preparing a self-supporting silica composite membrane, step (2) 2.2 Preparation of the composite membrane: The electrospinning process parameters are: spinning voltage 13-17kV, feed rate 0.8-1.2 mL / h, receiving substrate is aluminum foil, the spinning solution is electrospinned on the receiving substrate to prepare a fiber membrane, vacuum dried at 70-85℃ for 20-28h, peeled off, and a self-supporting silica composite membrane is obtained.

[0012] In the aforementioned method for preparing a self-supporting silica composite membrane, the self-supporting silica composite membrane has a three-dimensional interconnected fiber network structure and a thickness of 26–30 μm.

[0013] The aforementioned application of the self-supporting silica composite separator is as follows: the self-supporting silica composite separator is used as a separator for lithium metal batteries.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses vermiculite crystals as raw material to prepare a self-supporting silica composite membrane (ESPSN) through ion exchange exfoliation, two-step acid etching, preparation of spinning solution, and electrospinning. This method can transform layered vermiculite crystals into two-dimensional porous silica nanosheets (PSN) and combine them with polyvinylidene fluoride (PVDF) to form a self-supporting membrane.

[0015] 2. In this invention, 8–12 g of vermiculite crystals are dispersed in 250–350 mL of saturated NaCl solution, and the mixture is stirred and exfoliated in an oil bath at 75–85°C for 24–28 h. The filter cake is then added to 250–350 mL of saturated lithium chloride solution, and the mixture is stirred and exfoliated again at 75–85°C for another 24–28 h. + and Li + It can gradually penetrate the vermiculite interlayer, weakening the interlayer forces and causing the vermiculite crystals to gradually peel away from a massive, layered structure into a thin-layered structure. The absence of white precipitate after two dialysis analyses using 0.1–1 mol / L silver nitrate solution indicates that dialysis effectively removed Cl. - This reduces the adverse effects of impurity ions on electrochemical performance and provides a basis for obtaining grade A products with uniform structure.

[0016] 3. In this invention, 1.3–1.7 g of product A is added to 150–200 mL of 34–38 wt.% hydrochloric acid, stirred at 75–85°C for 12–14 h, and washed until the pH reaches 6.8–7. Then, it is immersed again in 250–350 mL of 34–38 wt.% hydrochloric acid, stirred at 75–85°C for 12–14 h, and washed until the pH reaches 6.8–7. This two-step acid etching can more thoroughly remove impurities such as Mg and Al from vermiculite, retaining the Si-O-based silicon-oxygen framework and forming a porous structure and surface Si-OH active sites. After centrifugation at 800–1200 r / min for 8–12 min, the supernatant is collected and freeze-dried at -10–0°C for 24–26 h. This helps reduce sheet aggregation, maintain the sheet and pore structure of the two-dimensional porous silica nanosheets, and facilitates uniform dispersion in organic solvents.

[0017] 4. Two-dimensional porous silica nanosheets, with a thickness of 1.56–1.96 nm and a specific surface area of ​​225–230 m² / g. This thin two-dimensional sheet structure shortens the lithium-ion transport path, improving lithium-ion transport capacity. The higher specific surface area provides more electrolyte contact sites and interfacial active sites, thereby enhancing the membrane's adsorption and wetting ability for the electrolyte. Simultaneously, the Si-OH groups on the surface of the two-dimensional porous silica nanosheets enhance their interaction with polar electrolytes.

[0018] 5. In this invention, 0.2–0.4 g of two-dimensional porous silica nanosheets are dispersed in 2–4 mL of N,N-dimethylformamide, and 0.05–0.1 g of polyvinylidene fluoride (PVDF) is added. The mixture is stirred at 800–1200 r / min for 24–28 h to obtain a spinning solution. N,N-dimethylformamide can dissolve PVDF and disperse the two-dimensional porous silica nanosheets. Prolonged stirring is beneficial for improving the uniformity of dispersion of the two-dimensional porous silica nanosheets in the spinning solution. PVDF can impart good flexibility, film-forming properties, and electrochemical stability to the membrane, while the two-dimensional porous silica nanosheets can improve the pore structure and hydrophilicity of the membrane.

[0019] 6. This invention employs electrospinning to prepare a fiber membrane on an aluminum foil receiving substrate. The spinning voltage is 13–17 kV, the feed rate is 0.8–1.2 mL / h, and the membrane is then vacuum-dried at 70–85℃ for 20–28 h before being peeled off to obtain a self-supporting silica composite membrane. Suitable spinning voltage and feed rate facilitate the formation of a continuous and uniform fiber structure, resulting in a uniform distribution of two-dimensional porous silica nanosheets. Vacuum drying removes residual N,N-dimethylformamide, improving the structural stability and electrochemical safety of the membrane.

[0020] 7. The silica self-supporting composite separator features a three-dimensional interconnected fiber network structure with a thickness of 26–30 μm. This ensures self-support and mechanical stability while avoiding excessive ion transport resistance due to excessive separator thickness. The three-dimensional interconnected fiber network structure provides continuous open channels, facilitating rapid electrolyte wetting and storage, and providing continuous channels for lithium-ion migration. This promotes rapid lithium-ion migration within the separator and reduces the impact of anion migration on concentration polarization. Experimental results show that the optimized separator achieves an ionic conductivity of 1.83 mS / cm and a lithium-ion transference number of 0.71, both higher than those of commercial polypropylene separators (0.62 mS / cm, 0.51).

[0021] 8. Due to the stable inorganic silicon-oxygen framework of the two-dimensional porous silica nanosheets, which forms a three-dimensional interconnected fiber network structure with polyvinylidene fluoride, the separator can maintain good structural integrity under high temperature conditions. After heat treatment at 200℃, the silica self-supporting composite separator did not show obvious deformation, shrinkage, or melting, indicating that it can effectively improve the problem of easy shrinkage of traditional polyolefin separators at high temperatures, thereby reducing the risk of separator failure, internal short circuit, and thermal runaway in lithium metal batteries under high temperature environments.

[0022] 9. The self-supporting silica composite membrane prepared by this invention can induce the formation of a dense and stable LiF-rich solid electrolyte interphase (SEI) membrane. The polar oxygen-containing groups on the surface of the two-dimensional porous silica nanosheets can improve the electrolyte distribution and the uniformity of the interfacial reaction, enabling the electrolyte components to undergo a more uniform interfacial reaction on the lithium metal anode surface. Simultaneously, the stable inorganic silicon-oxygen framework facilitates the construction of a uniform ion transport environment, promoting the formation of a stable SEI membrane containing inorganic components such as LiF. The LiF-rich SEI membrane exhibits high mechanical strength and good chemical stability, reducing the continuous decomposition of the electrolyte, decreasing dead lithium and byproduct formation, and maintaining the stability of the lithium metal anode interface during cycling.

[0023] 10. The self-supporting silica composite separator prepared by this invention can effectively suppress lithium dendrite growth and improve the stability of the lithium metal anode interface. Two-dimensional porous silica nanosheets have a high specific surface area and abundant Si-OH groups, which can enhance the separator's adsorption and wetting ability for the electrolyte, making the electrolyte distribution more uniform at the separator-lithium metal anode interface. Based on the above effects, lithium ions can reach the lithium metal anode surface more uniformly and deposit, avoiding excessive accumulation of lithium ions in local areas, thereby inhibiting the nucleation and growth of lithium dendrites. Furthermore, the uniform and stable interfacial environment is conducive to a more uniform interfacial reaction of electrolyte components on the lithium metal anode surface, promoting the formation of a dense and stable LiF-rich solid electrolyte interphase (SEI) film. The LiF-rich SEI film has high mechanical strength and good chemical stability, which can reduce the continuous decomposition of the electrolyte and the formation of dead lithium, and maintain the stability of the lithium metal anode interface during cycling. In-situ optical observations show that when using the separator of this invention, the interface of the lithium metal anode remains relatively smooth during continuous deposition, without significant dendritic lithium growth; while when using a commercial polypropylene separator, the surface of the lithium metal anode gradually roughens, accompanied by the formation of moss-like or dendritic lithium deposits. Furthermore, the Li||Li symmetric cell assembled using the separator of this invention achieves a performance of 0.25 mA / cm². 2 The membrane achieves stable lithium deposition / stripping cycling for over 2000 hours at the specified current density, with minimal voltage polarization and low curve fluctuations during cycling, indicating its effective ability to stabilize the lithium deposition / stripping process. Therefore, the silica self-supporting composite membrane prepared in this invention can significantly suppress lithium dendrite growth by promoting uniform lithium deposition and forming a stable LiF-rich SEI film, thereby improving the cycle stability and safety performance of Li||Li symmetric batteries.

[0024] 11. The silica self-supporting composite separator prepared by this invention can improve the rate performance and cycle life of lithium iron phosphate (LFP) lithium metal batteries. Due to its high porosity, good electrolyte wettability, high ionic conductivity, and high lithium-ion transference number, this separator can effectively reduce the battery's internal resistance and interfacial impedance, and improve the transport kinetics of lithium ions between the positive and negative electrodes. In LFP||Li batteries, batteries using the separator of this invention exhibit superior rate performance and capacity retention, indicating that this separator can not only stabilize the lithium metal anode interface but also improve the electrochemical performance of the entire battery under different rate and long-cycle conditions.

[0025] In summary, this invention has the advantages of simple preparation method, three-dimensional interconnected hierarchical porous structure of self-supporting silica composite membrane, high porosity, excellent thermal stability, high ionic conductivity and high lithium ion transference number. It can effectively uniform lithium ion flux, induce the formation of dense and stable LiF-rich SEI film, significantly inhibit lithium dendrite growth, and greatly improve the cycle life, rate performance and safety performance of lithium metal batteries. Attached Figure Description

[0026] Figure 1 This is a flowchart of the present invention for preparing a self-supporting silica composite membrane (ESPSN) using two-dimensional porous silica nanosheets (PSN) and polyvinylidene fluoride (PVDF) as raw materials by electrospinning. Figure 2 These are scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscope (TEM), and atomic force microscope (AFM) images of the PSNs prepared in Examples 1-5 of this invention; wherein... Figure 2 a is the SEM image of PSN. Figure 2 b is the distribution diagram of EDS elements in PSN. Figure 2 c is the TEM image of PSN. Figure 2 d is the AFM diagram of PSN; Figure 3 These are the Fourier transform infrared (FTIR), X-ray diffraction (XRD), nitrogen adsorption-desorption curves, and pore size distribution diagrams of the PSNs prepared in Examples 1-5 of this invention; wherein... Figure 3 a is the FTIR plot of PSN. Figure 3 b is the XRD pattern of PSN and layered vermiculite (VS). Figure 3 c is the nitrogen adsorption-desorption curve of PSN. Figure 3 d is the pore size distribution diagram of PSN; Figure 4 These are morphology, pore structure, wettability, and ion transport properties of the ESPSN-3 membrane prepared in Example 3 of this invention and a commercial polypropylene (PP) membrane; wherein... Figure 4 a is a surface SEM image of ESPSN-3. Figure 4 b is a cross-sectional SEM image of ESPSN-3. Figure 4 c is the pore size distribution diagram of PP and ESPSN-3. Figure 4 d represents the porosity diagram of PP and ESPSN-3. Figure 4 e represents the electrolyte contact angle diagram for PP and ESPSN-3. Figure 4 f is a graph showing the ionic conductivity and lithium-ion transference number of PP and ESPSN-3; Figure 5 These are thermal stability test graphs for PP and ESPSN-3; among them Figure 5 a is a digital photograph of PP after being treated at room temperature, 100℃ for 1 h, and 200℃ for 1 h. Figure 5 b is a digital photograph of ESPSN-3 after being treated at room temperature, 100℃ for 1 h, and 200℃ for 1 h; Figure 6These are in-situ optical microscopic observations of the lithium metal anode deposition process using ESPSN-3 and PP, as well as the cycle voltage curves of the Li||Li symmetric battery; among which... Figure 6 a shows in-situ optical microscopic observations of the lithium metal anode during the deposition process at 0 min, 15 min, and 30 min using ESPSN-3. Figure 6 b shows in-situ optical microscopic observations of the lithium metal anode deposition process at 0 min, 15 min, and 30 min when using PP. Figure 6 c represents a Li||Li symmetric cell assembled using PP and ESPSN-3 at 0.25 mA·cm⁻¹. -2 Long-cycle voltage curves under current density; Figure 7 These are surface morphology and solid electrolyte interphase (SEI) composition analysis diagrams of lithium metal anodes using ESPSN-3 and PP; among them... Figure 7 a is a SEM image of the lithium metal anode after using ESPSN-3. Figure 7 b is a SEM image of the lithium metal anode after using PP. Figure 7 c is the F 1s X-ray photoelectron spectroscopy (XPS) spectrum of the lithium metal anode after using ESPSN-3 and PP. Figure 7 d is the Li 1s XPS diagram of the lithium metal anode after using ESPSN-3 and PP; Figure 8 This is a graph showing the electrochemical performance of a lithium iron phosphate (LFP||Li) lithium metal battery assembled using PP and ESPSN-3; where... Figure 8 a is the electrochemical impedance spectroscopy of an LFP||Li battery assembled using PP and ESPSN-3. Figure 8 b is the rate performance graph of LFP||Li cells assembled using PP and ESPSN-3. Figure 8 c shows the long-cycle performance of LFP||Li cells assembled using PP and ESPSN-3 at 30℃. Figure 8 d is a graph showing the long-cycle performance of LFP||Li batteries assembled using PP and ESPSN-3 at 50℃. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0028] Example 1: A method for preparing a self-supporting silica composite membrane, comprising the following steps: (1) Preparation of two-dimensional porous silica nanosheets: 1.1 Ion exchange stripping: 8 g of vermiculite crystals were dispersed in 250 mL of saturated NaCl solution and stripped by stirring in an oil bath at 75 °C for 24 h. After cooling, the mixture was dialyzed until no white precipitate was detected by 0.1–1 mol / L silver nitrate solution. The mixture was then filtered and washed. The filter cake was then added to 250 mL of saturated lithium chloride solution and stripped by stirring at 75 °C for 24 h. After cooling to 15 °C, the mixture was filtered, washed, and dialyzed until no white precipitate was detected by 0.1–1 mol / L silver nitrate solution. The mixture was then vacuum filtered to obtain product A. 1.2 Two-step acid etching: Add 1.3g of product A to 150 mL of 34 wt.% hydrochloric acid, stir at 75℃ for 12 h, and wash until pH reaches 6.8; immerse again in 250 mL of 34 wt.% hydrochloric acid, stir at 75℃ for 12 h, and wash until pH reaches 6.8; centrifuge at 800 r / min for 8 min, take the supernatant and freeze-dry at -10℃ for 24 h to obtain two-dimensional porous silica nanosheets.

[0029] (2) Preparation of electrospun composite membrane: 2.1 Preparation of spinning solution: 0.2 g of two-dimensional porous silica nanosheets were dispersed in 2 mL of N,N-dimethylformamide, and 0.05 g of polyvinylidene fluoride was added. The mixture was stirred at 800 r / min for 24 h to obtain the spinning solution. 2.2 Preparation of composite membrane: The electrospinning process parameters are as follows: spinning voltage 13kV, feed rate 0.8mL / h, receiving substrate is aluminum foil, the spinning solution is used to prepare fiber membrane on the receiving substrate by electrospinning, vacuum drying at 70℃ for 20h, peeling, to obtain silica self-supporting composite membrane.

[0030] Example 2: A method for preparing a self-supporting silica composite membrane, comprising the following steps: (1) Preparation of two-dimensional porous silica nanosheets: 1.1 Ion exchange stripping: 9 g of vermiculite crystals were dispersed in 270 mL of saturated NaCl solution and stripped by stirring in an oil bath at 78 °C for 25 h. After cooling, the mixture was dialyzed until no white precipitate was detected by 0.1–1 mol / L silver nitrate solution. The mixture was then filtered and washed. The filter cake was then added to 270 mL of saturated lithium chloride solution and stripped by stirring at 78 °C for 25 h. After cooling to 17 °C, the mixture was filtered, washed, and dialyzed until no white precipitate was detected by 0.1–1 mol / L silver nitrate solution. The mixture was then vacuum filtered to obtain product A. 1.2 Two-step acid etching: Add 1.4 g of product A to 160 mL of 35 wt.% hydrochloric acid, stir at 78℃ for 12.5 h, and wash until pH reaches 6.9; immerse again in 260 mL of 35 wt.% hydrochloric acid, stir at 78℃ for 12.5 h, and wash until pH reaches 6.9; centrifuge at 900 r / min for 9 min, take the supernatant and freeze-dry at ~7℃ for 25 h to obtain two-dimensional porous silica nanosheets.

[0031] (2) Preparation of electrospun composite membrane: 2.1 Preparation of spinning solution: 0.25 g of two-dimensional porous silica nanosheets were dispersed in 2.5 mL of N,N-dimethylformamide, and 0.065 g of polyvinylidene fluoride was added. The mixture was stirred at 900 r / min for 25 h to obtain the spinning solution. 2.2 Preparation of composite membrane: The electrospinning process parameters are as follows: spinning voltage 14 kV, feed rate 0.9 mL / h, receiving substrate is aluminum foil, the spinning solution is used to prepare fiber membrane on the receiving substrate by electrospinning, vacuum drying at 78℃ for 24h, peeling, to obtain silica self-supporting composite membrane.

[0032] Example 3: A method for preparing a self-supporting silica composite membrane, comprising the following steps: (1) Preparation of two-dimensional porous silica nanosheets: 1.1 Ion exchange stripping: 10 g of vermiculite crystals were dispersed in 300 mL of saturated NaCl solution and stripped by stirring in an oil bath at 80 °C for 26 h. After cooling, the crystals were dialyzed until no white precipitate was detected by 0.1–1 mol / L silver nitrate solution. The crystals were then filtered and washed. The filter cake was then added to 300 mL of saturated lithium chloride solution and stripped by stirring at 80 °C for 26 h. After cooling to 20 °C, the crystals were filtered, washed, and dialyzed until no white precipitate was detected by 0.1–1 mol / L silver nitrate solution. The crystals were then vacuum filtered to obtain product A. 1.2 Two-step acid etching: Add 1.5 g of product A to 180 mL of 36 wt.% hydrochloric acid, stir at 80℃ for 13 h, and wash until pH reaches 6.9; immerse again in 300 mL of 36 wt.% hydrochloric acid, stir at 80℃ for 13 h, and wash until pH reaches 6.9; centrifuge at 1000 r / min for 10 min, take the supernatant and freeze-dry at ~5℃ for 25 h to obtain two-dimensional porous silica nanosheets.

[0033] (2) Preparation of electrospun composite membrane: 2.1 Preparation of spinning solution: 0.3 g of two-dimensional porous silica nanosheets were dispersed in 3 mL of N,N-dimethylformamide, and 0.08 g of polyvinylidene fluoride was added. The mixture was stirred at 1000 r / min for 26 h to obtain the spinning solution. 2.2 Preparation of composite membrane: The electrospinning process parameters are as follows: spinning voltage 15kV, feed rate 1 mL / h, receiving substrate is aluminum foil, the spinning solution is used to prepare fiber membrane on the receiving substrate by electrospinning, vacuum drying at 80℃ for 25 h, peeling, to obtain silica self-supporting composite membrane (ESPSN-3).

[0034] Example 4: A method for preparing a self-supporting silica composite membrane, comprising the following steps: (1) Preparation of two-dimensional porous silica nanosheets: 1.1 Ion exchange stripping: 11 g of vermiculite crystals were dispersed in 320 mL of saturated NaCl solution and stripped by stirring in an oil bath at 82 °C for 27 h. After cooling, the mixture was dialyzed until no white precipitate was detected by 0.1–1 mol / L silver nitrate solution. The mixture was then filtered and washed. The filter cake was then added to 320 mL of saturated lithium chloride solution and stripped by stirring at 82 °C for 27 h. After cooling to 24 °C, the mixture was filtered, washed, and dialyzed until no white precipitate was detected by 0.1–1 mol / L silver nitrate solution. The mixture was then vacuum filtered to obtain product A. 1.2 Two-step acid etching: Add 1.6 g of product A to 190 mL of 37 wt.% hydrochloric acid, stir at 82℃ for 13.5 h, and wash until pH reaches 6.9; immerse again in 320 mL of 37 wt.% hydrochloric acid, stir at 82℃ for 13.5 h, and wash until pH reaches 6.9; centrifuge at 1100 r / min for 11 min, take the supernatant and freeze-dry at ~3℃ for 25.5 h to obtain two-dimensional porous silica nanosheets.

[0035] (2) Preparation of electrospun composite membrane: 2.1 Preparation of spinning solution: 0.35 g of two-dimensional porous silica nanosheets were dispersed in 3.5 mL of N,N-dimethylformamide, and 0.0875 g of polyvinylidene fluoride was added. The mixture was stirred at 1100 r / min for 27 h to obtain the spinning solution. 2.2 Preparation of composite membrane: The electrospinning process parameters are as follows: spinning voltage 16kV, feed rate 1.1 mL / h, receiving substrate is aluminum foil, the spinning solution is used to prepare fiber membrane on the receiving substrate by electrospinning, vacuum drying at 82℃ for 27 h, peeling, to obtain silica self-supporting composite membrane.

[0036] Example 5: A method for preparing a self-supporting silica composite membrane, comprising the following steps: (1) Preparation of two-dimensional porous silica nanosheets: 1.1 Ion exchange exfoliation: 12 g of vermiculite crystals were dispersed in 350 mL of saturated NaCl solution and exfoliated by stirring in an oil bath at 85 °C for 28 h. After cooling, the crystals were dialyzed until no white precipitate was detected by 0.1–1 mol / L silver nitrate solution. The crystals were then filtered and washed. The filter cake was then added to 350 mL of saturated lithium chloride solution and exfoliated by stirring at 85 °C for 28 h. After cooling to 25 °C, the crystals were filtered, washed, and dialyzed until no white precipitate was detected by 0.1–1 mol / L silver nitrate solution. The crystals were then vacuum filtered to obtain product A. 1.2 Two-step acid etching: 1.7 g of product A was added to 200 mL of 38 wt.% hydrochloric acid and stirred at 85°C for 14 h. The mixture was then washed until the pH reached 7. The mixture was then immersed in 350 mL of 38 wt.% hydrochloric acid and stirred at 85°C for 14 h. The mixture was then washed until the pH reached 7. The mixture was centrifuged at 1200 r / min for 12 min. The supernatant was then freeze-dried at 0°C for 26 h to obtain two-dimensional porous silica nanosheets.

[0037] (2) Preparation of electrospun composite membrane: 2.1 Preparation of spinning solution: 0.4 g of two-dimensional porous silica nanosheets were dispersed in 4 mL of N,N-dimethylformamide, and 0.1 g of polyvinylidene fluoride was added. The mixture was stirred at 1200 r / min for 28 h to obtain the spinning solution. 2.2 Preparation of composite membrane: The electrospinning process parameters are as follows: spinning voltage 17kV, feed rate 1.2 mL / h, receiving substrate is aluminum foil, the spinning solution is used to prepare fiber membrane on the receiving substrate by electrospinning, vacuum drying at 85℃ for 28 h, peeling, to obtain silica self-supporting composite membrane.

[0038] Application example: The silica self-supporting composite separator prepared in Example 3 was applied to lithium iron phosphate lithium metal batteries.

[0039] Using lithium iron phosphate (LFP) electrodes as the positive electrode, lithium metal sheets as the negative electrode, and the self-supporting silica composite membrane prepared in Example 3 as the separator, LFP||Li batteries were assembled in an inert atmosphere glove box. Meanwhile, LFP||Li batteries assembled with commercial PP membranes served as a control group to evaluate the application effect of the self-supporting silica composite membrane prepared in Example 3 in lithium metal batteries.

[0040] Experiments have shown that: 1. Figure 1 This is a flowchart illustrating the preparation of a self-supporting silica composite membrane (ESPSN) using two-dimensional porous silica nanosheets (PSN) and polyvinylidene fluoride (PVDF) as raw materials via electrospinning. Figure 1As can be seen, two-dimensional porous silica nanosheets (PSN) are first dispersed in a solvent system containing polyvinylidene fluoride (PVDF), and after thorough stirring, a uniform spinning solution is formed. Subsequently, under electrospinning, the spinning solution is stretched into continuous fibers and deposited on an aluminum foil receiving substrate to obtain a self-supporting silica composite separator (ESPSN). This figure illustrates that this invention does not simply coat PSN onto the surface of a commercial separator, but rather uses electrospinning to uniformly distribute PSN and PVDF to form a fiber network, thereby constructing a self-supporting composite separator with a three-dimensional interconnected structure. This structure ensures both good flexibility and integrity of the separator, while also forming continuous open channels, providing pathways for electrolyte wetting, storage, and lithium-ion migration. Therefore, Figure 1 This demonstrates that the preparation method of the present invention has a simple process and a reasonable structural design, which can provide a foundation for improving the ion transport capability and interface stability of lithium metal batteries in the future.

[0041] 2. Figure 2 These are scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscope (TEM), and atomic force microscope (AFM) images of the PSNs prepared in Examples 1-5 of this invention; wherein... Figure 2 a is the SEM image of PSN. Figure 2 b is the distribution diagram of EDS elements in PSN. Figure 2 c is the TEM image of PSN. Figure 2 d is the AFM chart of PSN. (From...) Figure 2 As can be seen, PSN exhibits a distinct lamellar structure, resembling a two-dimensional material composed of many thin sheets. This indicates that after ion exchange exfoliation and two-step acid etching, the original vermiculite gradually transformed from a relatively thick layered mass into a thinner two-dimensional lamellar structure. Figure 2 As can be seen from b, the Si and O elements in the PSN are relatively evenly distributed, indicating that the material mainly retains the Si-O silicon-oxygen framework after acid etching. Meanwhile, impurity elements such as Mg and Al are significantly reduced, indicating that the two-step acid etching effectively removes metallic impurities from the vermiculite, resulting in a more uniform composition of the obtained PSN. Figure 2 As can be seen from c, the PSN sheets are relatively thin and have clear edges, further proving that they have a typical two-dimensional nanosheet structure. Figure 2 As can be seen from d, the thickness of PSN is approximately 1.76 nm, indicating that it belongs to a single-layer or few-layer nanosheet. For membrane materials, the thinner the sheet, the shorter the transport path for lithium ions; at the same time, two-dimensional sheets can provide a larger contact area, which is beneficial for adsorbing electrolyte and providing more ion transport interfaces. Therefore, through Figure 2 It can be demonstrated that the present invention successfully prepared a thin and homogenized PSN, providing a material basis for the subsequent construction of ESPSN with high wettability and high ion transport capability.

[0042] 3. Figure 3 These are the Fourier transform infrared (FTIR), X-ray diffraction (XRD), nitrogen adsorption-desorption curves, and pore size distribution diagrams of the PSNs prepared in Examples 1-5 of this invention; wherein... Figure 3 a is the FTIR plot of PSN. Figure 3 b is the XRD pattern of PSN and vermiculite raw materials. Figure 3 c is the nitrogen adsorption-desorption curve of PSN. Figure 3 d is the pore size distribution diagram of PSN; from Figure 3 As can be seen, characteristic signals such as Si-O-Si and Si-OH are present in the PSN. Si-O-Si indicates that the material retains a silicon-oxygen framework, while Si-OH indicates the presence of oxygen-containing active groups on the PSN surface. Si-OH has strong polarity and can enhance the interaction between the PSN and the polar electrolyte, acting as "water absorption sites," making it easier for the electrolyte to spread and enter the membrane channels. Figure 3 As can be seen from b, the XRD diffraction peaks of PSN show significant changes compared to vermiculite, especially the shifts or intensities of diffraction peaks related to the layered structure. Changes in the position of XRD peaks reflect changes in the interlayer spacing: when diffraction peaks shift to lower angles, it usually indicates an increase in interlayer spacing, meaning that the originally tightly stacked layers are being stretched or peeled off. This result suggests that ion exchange exfoliation and acid etching can weaken the interlayer forces of the original vermiculite, promoting layer peeling and the formation of a two-dimensional structure. Figure 3 c shows that PSN exhibits significant nitrogen adsorption-desorption behavior, with a specific surface area of ​​approximately 230.9 m². 2 The / g indicates that the material has a large number of porous structures and contact surfaces both internally and on the surface. A larger specific surface area means a greater contact area per unit mass of material, which is beneficial for adsorbing more electrolyte. Further... Figure 3 As can be seen from d, the PSN exhibits mesoporous distribution characteristics, indicating that the acid etching process not only removes impurity elements but also introduces porous channels into the layered structure. Figure 3 It can be demonstrated that PSN simultaneously possesses a two-dimensional sheet structure, Si-OH oxygen-containing functional groups, and a porous structure. These features can synergistically enhance electrolyte adsorption capacity, improve membrane wettability, and provide more channels for lithium-ion transport.

[0043] Figure 4 These are morphology, pore structure, wettability, and ion transport properties of the ESPSN-3 membrane prepared in Example 3 of this invention and a commercial polypropylene (PP) membrane; wherein... Figure 4 a is a surface SEM image of ESPSN-3. Figure 4 b is a cross-sectional SEM image of ESPSN-3. Figure 4 c is the pore size distribution diagram of PP and ESPSN-3. Figure 4d represents the porosity diagram of PP and ESPSN-3. Figure 4 e represents the electrolyte contact angle diagram for PP and ESPSN-3. Figure 4 f is a graph showing the ionic conductivity and lithium-ion transference number of PP and ESPSN-3; from Figure 4 As can be seen, the surface of ESPSN-3 is composed of a large number of interwoven fibers, forming a continuous three-dimensional porous network structure. This structure is similar to interconnected "fiber channels," providing pathways for electrolyte entry and lithium-ion migration. Figure 4 As can be seen from b, ESPSN-3 has a complete cross-sectional structure with a thickness of approximately 26.4 μm, close to the thickness of commercial PP membranes (approximately 25 μm). This indicates that although the membrane possesses a self-supporting three-dimensional network structure, it does not significantly increase the membrane thickness. Excessive membrane thickness increases the distance lithium ions must travel, thus increasing battery resistance. Therefore, ESPSN-3 maintains a thickness close to that of PP while preserving structural integrity, which is beneficial for balancing safety and electrochemical performance. Figure 4 As can be seen from c, compared with PP, ESPSN-3 has a pore size distribution that is more suitable for electrolyte wetting and ion transport, indicating that its pore structure is more conducive to electrolyte entry into the membrane interior. Figure 4 As can be seen from d, the porosity of ESPSN-3 is approximately 59.14%, higher than that of PP (42.65%). Porosity can be understood as the "proportion of voids" within the membrane; the higher the porosity, the more electrolyte the membrane can store, and the smoother the lithium-ion transport. Figure 4 As can be seen, the electrolyte contact angle of ESPSN-3 is approximately 17.2°, significantly lower than that of PP (45.6°). A smaller contact angle indicates that electrolyte droplets spread more easily on the membrane surface, resulting in better membrane wettability; therefore, ESPSN-3 is more easily wetted by the electrolyte than PP. Figure 4 As can be seen from f, the ionic conductivity of ESPSN-3 is approximately 1.83 mS / cm. -1 0.62 mS cm higher than PP -1 This indicates that lithium ions pass through ESPSN-3 more quickly; simultaneously, the lithium ion transference number of ESPSN-3 is approximately 0.71, higher than that of PP (0.51), indicating that lithium ions account for a higher proportion during ion migration, which can reduce concentration polarization caused by anion migration. Figure 4 It can be demonstrated that ESPSN-3 is superior to PP in terms of porosity, wettability, ionic conductivity and lithium-ion transference number, which helps to reduce lithium-ion transport resistance and allows lithium ions to pass through the separator more uniformly and quickly, thereby improving the dynamic performance of lithium metal batteries.

[0044] 5. Figure 5 These are thermal stability test graphs for PP and ESPSN-3; among them Figure 5a is a digital photograph of PP after being treated at room temperature, 100℃ for 1 h, and 200℃ for 1 h. Figure 5 b shows digital photographs of ESPSN-3 after treatment at room temperature, 100℃ for 1 h, and 200℃ for 1 h; by Figure 5 As can be seen, PP shrinks significantly after high-temperature treatment, especially after 1 hour at 200℃, exhibiting severe deformation and even melting, indicating the poor thermal dimensional stability of traditional polyolefin separators. For lithium metal batteries, the separator, located between the positive and negative electrodes, primarily prevents direct contact between them while allowing lithium ions to pass through. If the separator shrinks or melts at high temperatures, the positive and negative electrodes may come into direct contact, potentially leading to internal short circuits or even thermal runaway. Figure 5 As can be seen from b, ESPSN-3 maintained a relatively complete circular membrane morphology after treatment at 100℃ for 1 h and 200℃ for 1 h, without significant shrinkage or melting. This result indicates that PSN possesses a stable inorganic silicon-oxygen framework, and its introduction into the PVDF fiber network can support the membrane structure like a "heat-resistant scaffold," thereby significantly improving the membrane's heat resistance and dimensional stability. Figure 5 It can be proven that ESPSN-3 can effectively improve the problem of PP shrinkage at high temperatures, thereby reducing the risk of short circuits and thermal runaway caused by separator failure in lithium metal batteries under high temperature conditions.

[0045] 6. Figure 6 These are in-situ optical microscopic observations of the lithium metal anode deposition process using ESPSN-3 and PP, as well as long-cycle voltage curves of Li||Li symmetric cells; among them Figure 6 a shows in-situ optical microscopic observations of the lithium metal anode during the deposition process at 0 min, 15 min, and 30 min using ESPSN-3. Figure 6 b shows in-situ optical microscopic observations of the lithium metal anode deposition process at 0 min, 15 min, and 30 min when using PP. Figure 6 c represents a Li||Li symmetric cell assembled using PP and ESPSN-3 at 0.25 mA cm⁻¹. -2 Long-cycle voltage curve at current density; from Figure 6 As can be seen, during the continuous lithium deposition process, the lithium metal anode interface remained relatively flat when using ESPSN-3. No obvious dendritic lithium growth or severe interface undulations were observed during the observation periods of 0 min, 15 min, and 30 min, indicating that ESPSN-3 can enable lithium ions to reach the lithium metal surface more uniformly, thereby promoting uniform lithium deposition. This can be understood as follows: if lithium ions reach the anode uniformly, they will deposit like a uniformly spread metal layer; if there are too many lithium ions in local areas, needle-like or dendritic lithium structures are more likely to grow. Figure 6As can be seen from b, when using PP, the surface of the lithium metal anode gradually becomes rougher with the extension of deposition time, and obvious moss-like or dendritic lithium deposits appear. This indicates that PP is difficult to effectively uniformly distribute lithium-ion flux, easily leading to excessively rapid local lithium deposition and inducing dendrite growth. Further analysis... Figure 6 c shows that the Li||Li symmetric cell assembled using ESPSN-3 achieves a performance of 0.25 mA cm⁻¹. -2 Stable lithium deposition / stripping cycling exceeding 2000 h can be achieved at current densities, with minimal voltage polarization and stable curves during cycling. Li||Li symmetric cells can be used to directly observe the stability of repeated lithium metal anode deposition and stripping; a smoother curve indicates a more stable lithium deposition / stripping process, while greater voltage fluctuations indicate a less stable interface. In contrast, symmetric cells using PP exhibit shorter cycle times and larger voltage fluctuations, indicating that PP struggles to maintain a stable lithium metal interface over extended periods. Figure 6 It can be demonstrated that ESPSN-3 can effectively suppress lithium dendrite growth and reduce interfacial polarization during lithium deposition / stripping, thereby significantly improving the cycle stability of Li||Li symmetric cells.

[0046] 7. Figure 7 These are surface morphology and solid electrolyte interphase (SEI) film composition analysis diagrams of lithium metal anodes using ESPSN-3 and PP; among them... Figure 7 a is a SEM image of the lithium metal anode after using ESPSN-3. Figure 7 b is a SEM image of the lithium metal anode after using PP. Figure 7 c is the F 1s X-ray photoelectron spectroscopy (XPS) spectrum of the lithium metal anode after using ESPSN-3 and PP. Figure 7 d shows the Li 1s XPS diagram of the lithium metal anode after using ESPSN-3 and PP. Figure 7 As can be seen, the lithium metal anode surface is relatively smooth and dense after using ESPSN-3, without a large number of pores or severely fragmented structures, indicating that the lithium deposition / stripping process is more uniform and stable. Figure 7 As can be seen from b, the lithium metal anode surface is rough after using PP, with obvious pores, cracks, and uneven deposition structure, indicating that PP is difficult to maintain a stable lithium metal interface. Further analysis... Figure 7 The F 1s spectrum of c shows that the LiF signal on the lithium metal anode surface is more pronounced after using ESPSN-3, indicating that ESPSN-3 is beneficial for the formation of a LiF-rich SEI film. Figure 7The Li 1s spectrum of d also shows that the LiF-related signal is more prominent after using ESPSN-3, further proving that it can promote the formation of a LiF-rich interface layer. The SEI film can be understood as a protective film formed on the surface of the lithium metal anode. If this film is dense and stable, it can reduce the continued decomposition of the electrolyte and prevent lithium deposition from becoming increasingly uneven. LiF is a common and stable inorganic SEI component with good chemical stability and mechanical strength, which helps to improve the stability of the SEI film. Figure 7 It can be demonstrated that ESPSN-3 can not only improve the surface morphology of lithium metal anodes, but also promote the formation of stable SEI films rich in LiF, thus explaining why it suppresses lithium dendrites and improves the cycle stability of Li||Li symmetric batteries.

[0047] 8. Figure 8 This is a graph showing the electrochemical performance of a lithium iron phosphate (LFP||Li) lithium metal battery assembled using PP and ESPSN-3; where... Figure 8 a is the electrochemical impedance spectroscopy of an LFP||Li battery assembled using PP and ESPSN-3. Figure 8 b is the rate performance graph of LFP||Li cells assembled using PP and ESPSN-3. Figure 8 c shows the long-cycle performance of LFP||Li cells assembled using PP and ESPSN-3 at 30℃. Figure 8 Figure d shows the long-cycle performance of LFP||Li cells assembled using PP and ESPSN-3 at 50℃. Figure 8 As can be seen, the LFP||Li battery using ESPSN-3 exhibits lower impedance, indicating smoother lithium-ion transport and interfacial reactions. Therefore, ESPSN-3 can improve electrolyte wettability and lithium-ion transport behavior, reducing resistance to ion migration and interfacial reactions within the battery. Figure 8 As can be seen from b, at different rate rates, the battery using ESPSN-3 exhibits better discharge capacity and capacity recovery capability. Rate performance reflects the battery's ability to operate at higher currents; the higher the rate, the greater the requirement for rapid lithium-ion transport. ESPSN-3 can maintain more efficient lithium-ion transport under higher current charge and discharge conditions, thus exhibiting better rate performance. Figure 8 As can be seen from c, under long-term cycling conditions at 30℃, the battery using ESPSN-3 exhibits slower capacity decay and better cycle stability than PP, indicating that ESPSN-3 can improve battery cycle life by stabilizing the lithium metal anode interface and improving ion transport. Figure 8As can be seen from d, at a relatively high temperature of 50℃, the battery using ESPSN-3 still maintains good cycle stability, while the PP battery shows more significant capacity decay. This indicates that the thermal stability and interface stabilization of ESPSN-3 can improve the battery's operational stability under high-temperature conditions. Figure 8 It can be demonstrated that ESPSN-3, as a separator for lithium metal batteries, can reduce interface impedance, improve rate performance, and enhance the long-cycle stability of LFP||Li batteries at 30℃ and 50℃.

[0048] The applicant has also conducted the above-described modifications on the self-supporting silica composite membranes prepared in other embodiments. Figures 4-8 The experimental tests and analyses yielded results comparable to those of the tests and analyses described above.

Claims

1. A method for preparing a self-supporting silica composite membrane, characterized by comprising the following steps: (1) Preparation of two-dimensional porous silica nanosheets: 1.1 Ion exchange stripping: Vermiculite crystals were dispersed in a saturated sodium chloride solution for ion exchange stripping, then transferred to a lithium chloride solution for secondary stripping. After dialysis to remove impurities, product A was obtained. 1.2 Two-step acid etching: Product A was subjected to two-step acid etching with hydrochloric acid, followed by centrifugation and freeze-drying to obtain two-dimensional porous silica nanosheets; (2) Preparation of electrospun composite membrane: 2.1 Preparation of spinning solution: Two-dimensional porous silica nanosheets were dispersed in a solvent, polyvinylidene fluoride was added, and the mixture was stirred to obtain a spinning solution; 2.2 Preparation of composite membrane: The spinning solution was used to prepare a fiber membrane on the receiving substrate by electrospinning. After vacuum drying and peeling, a silica self-supporting composite membrane was obtained.

2. The method for preparing the self-supporting silica composite membrane according to claim 1, characterized in that: In step (1), 1.1 Ion exchange stripping: 8-12 g of vermiculite crystals are dispersed in 250-350 mL of saturated NaCl solution, and stripped by stirring in an oil bath at 75-85°C for 24-28 h. After cooling, the crystals are dialyzed until no white precipitate is detected by 0.1-1 mol / L silver nitrate solution. The crystals are then filtered and washed. The filter cake is then added to 250-350 mL of saturated lithium chloride solution, and stripped by stirring at 75-85°C for 24-28 h. After cooling to 15-25°C, the crystals are filtered, washed, and dialyzed until no white precipitate is detected by 0.1-1 mol / L silver nitrate solution. The crystals are then vacuum filtered to obtain product A.

3. The method for preparing the self-supporting silica composite membrane according to claim 1, characterized in that: In step (1), the two-step acid etching process is as follows: 1.3-1.7 g of product A is added to 150-200 mL of 34-38 wt.% hydrochloric acid, stirred at 75-85℃ for 12-14 h, and washed until the pH reaches 6.8-7; the product is then immersed in 250-350 mL of 34-38 wt.% hydrochloric acid again, stirred at 75-85℃ for 12-14 h, and washed until the pH reaches 6.8-7; the product is then centrifuged at 800-1200 r / min for 8-12 min, and the supernatant is freeze-dried at -10-0℃ for 24-26 h to obtain two-dimensional porous silica nanosheets.

4. The method for preparing the self-supporting silica composite membrane according to claim 3, characterized in that: The two-dimensional porous silica nanosheets have a thickness of 1.56–1.96 nm and a specific surface area of ​​225–230 m². 2 / g.

5. The method for preparing the self-supporting silica composite membrane according to claim 1, characterized in that: In step (2), 2.1, the spinning solution is prepared by dispersing 0.2-0.4 g of two-dimensional porous silica nanosheets in 2-4 mL of N,N-dimethylformamide, adding 0.05-0.1 g of polyvinylidene fluoride, and stirring at 800-1200 r / min for 24-28 h to obtain the spinning solution.

6. The method for preparing the self-supporting silica composite membrane according to claim 1, characterized in that: In step (2), 2.2, the composite membrane is prepared by electrospinning with the following process parameters: spinning voltage 13-17kV, feed rate 0.8-1.2mL / h, receiving substrate is aluminum foil, the spinning solution is electrospinned on the receiving substrate to prepare a fiber membrane, vacuum dried at 70-85℃ for 20-28h, peeled off, and a silica self-supporting composite membrane is obtained.

7. The method for preparing the self-supporting silica composite membrane according to claim 1, characterized in that: The self-supporting silica composite membrane has a three-dimensional interconnected fiber network structure and a thickness of 26–30 μm.

8. The application of the self-supporting silica composite membrane according to any one of claims 1-7, characterized in that, The self-supporting silica composite separator is used as a separator for lithium metal batteries.

Images