Composite solid electrolyte layer and method for manufacturing the same

Abstract

The application provides a composite solid electrolyte layer and a preparation method thereof. The preparation method comprises the following steps: S1, coating solid electrolyte raw materials on both side surfaces of an aramid-based film to obtain a composite solid electrolyte layer precursor; S2, covering a release film on at least one side surface of the composite solid electrolyte layer precursor to obtain a laminated structure; and S3, performing first hot roller pressing treatment on the laminated structure, and then peeling off the release film to obtain the composite solid electrolyte layer. The solvent-free solid electrolyte raw materials are used for coating, so that the problem of solvent residue is solved; the aramid-based film can provide a support skeleton for preparing the composite solid electrolyte layer precursor; and the release film can play a role in protecting the composite solid electrolyte layer precursor.

Description

Technical Field

[0001] This invention relates to the field of solid electrolyte technology, and more specifically, to a composite solid electrolyte layer and its preparation method. Background Technology

[0002] Solid-state batteries generally consist of a positive electrode, a negative electrode, and an electrolyte, with the electrolyte being a solid electrolyte material. Solid-state batteries have attracted significant attention in the global energy research field due to their high energy density and good safety performance.

[0003] Solid-state electrolytes, as the core component of solid-state batteries, enable the transfer of lithium ions between the positive and negative electrodes. They also act as a separator to separate the positive and negative electrodes, preventing internal short circuits and ensuring safe battery operation. Currently, developed solid-state electrolytes are mainly classified into three types: inorganic solid-state electrolytes, polymer solid-state electrolytes, and composite solid-state electrolytes. Among them, inorganic solid-state electrolytes, with their high ionic conductivity and thermal stability, have become the primary choice for manufacturing high-performance solid-state batteries. Summary of the Invention

[0004] Traditional inorganic solid electrolytes suffer from brittleness. During production, this brittleness makes it difficult to process the material into thin films, limiting its flexibility in battery design and its ability to be mass-produced. Furthermore, during battery use, the brittleness of inorganic solid electrolytes makes them prone to microcracks under mechanical stress. These microcracks not only reduce the electrolyte's conductivity but also provide pathways for lithium dendrite growth, potentially leading to internal short circuits and threatening battery safety and lifespan.

[0005] Based on this, a composite solid electrolyte layer and its preparation method were researched and developed, which is of great significance for improving its processability, flexibility, mechanical strength and ionic conductivity, thereby improving the safety, cycle stability and service life of solid batteries.

[0006] The main objective of this invention is to provide a composite solid electrolyte layer and its preparation method, in order to solve the problems in the prior art where inorganic solid electrolytes are difficult to process into films, and where inorganic solid electrolyte layers have poor flexibility and mechanical strength, low ionic conductivity, and poor safety, cycle stability, and short service life of solid batteries made from them.

[0007] To achieve the above objectives, the present invention provides a method for preparing a composite solid electrolyte layer, the method comprising: step S1, coating solid electrolyte raw materials on both sides of an aramid-based film to obtain a composite solid electrolyte layer precursor; step S2, covering at least one side of the composite solid electrolyte layer precursor with a release film to obtain a laminated structure; and step S3, subjecting the laminated structure to a first hot rolling treatment, and then peeling off the release film to obtain the composite solid electrolyte layer.

[0008] As one implementation method, the solid electrolyte raw material does not contain liquid.

[0009] As one implementation method, the solid electrolyte raw material does not contain solvent.

[0010] In one embodiment, step S1 further includes: melting the solid electrolyte raw material to obtain a solid electrolyte melt, coating the solid electrolyte melt on both sides of the aramid base film to obtain a composite solid electrolyte layer precursor.

[0011] In one embodiment, the amount of solid electrolyte melt coated on the surface of the aramid-based film is 20 g / m². 2 ~60g / m 2 .

[0012] As one implementation method, the melting treatment temperature is 80℃~250℃ and the time is 1min~30min.

[0013] In one embodiment, the solid electrolyte raw material includes solid electrolyte powder and binder, wherein the weight ratio of solid electrolyte powder to binder is (95-99):(1-5).

[0014] In one embodiment, the solid electrolyte powder is an inorganic solid electrolyte powder; the inorganic solid electrolyte powder is selected from one or more of the group consisting of oxide solid electrolytes, sulfide solid electrolytes and halide solid electrolytes.

[0015] In one implementation, the release film is a solid film without pores; the thickness of the release film is 10μm to 50μm.

[0016] In one embodiment, the release film is made of a first organic polymer material, which is selected from one or more of the group consisting of polyimide, polyethylene terephthalate, polyetheretherketone, polyphenylene sulfide, and poly(p-phenylenebenzodioxazole).

[0017] In one embodiment, the aramid-based membrane is a porous membrane; the porosity of the aramid-based membrane is 50% to 90%.

[0018] In one embodiment, the average pore size of the aramid-based film is 0.1 μm to 2000 μm; the thickness of the aramid-based film is 3 μm to 25 μm.

[0019] In one implementation, the thickness of the composite solid electrolyte layer precursor is 5 μm to 50 μm.

[0020] In one embodiment, step S2 further includes: when the temperature of the composite solid electrolyte layer precursor is 50°C to 250°C, covering at least one side surface of the composite solid electrolyte layer precursor with a release film to obtain a laminated structure.

[0021] In one embodiment, in step S3, the temperature of the first hot rolling treatment is 50°C to 250°C; and / or, the pressure of the first hot rolling treatment is 0.5MPa to 50MPa; and / or, the time of the first hot rolling treatment is 1min to 30min.

[0022] Another aspect of the present invention provides a composite solid electrolyte layer, which is prepared by the preparation method of the composite solid electrolyte layer provided in this application.

[0023] To address the inherent brittleness of existing inorganic solid electrolyte layers and the difficulty in processing inorganic solid electrolytes into films during production, this application provides a method for preparing a composite solid electrolyte layer. Compared to existing methods using solution casting or solution coating to prepare solid electrolyte layers, this application involves covering the surface of the composite solid electrolyte layer precursor with a release film before performing a first hot rolling process. The introduction of the release film inhibits direct contact between the composite solid electrolyte layer precursor and the hot rolling rollers during the first hot rolling process, thereby reducing adhesion and contamination of the precursor and improving its processing performance. Simultaneously, it enhances the purity and structural integrity of the resulting composite solid electrolyte layer, suppressing crack formation during use and thus preventing internal short circuits in the resulting solid-state battery, thereby improving the cycle stability and safety of the solid-state battery. In addition, compared with other types of base films, aramid base films have better flexibility, thermal stability and mechanical properties, which can provide a supporting framework for the preparation of composite solid electrolyte layer precursors, thereby enabling the prepared composite solid electrolyte layer to have both excellent flexibility, mechanical strength and high ionic conductivity. Attached Figure Description

[0024] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0025] Figure 1 The image shows a SEM image of the surface of the composite solid electrolyte layer obtained in Example 1 of this application;

[0026] Figure 2 The electrochemical impedance spectroscopy of the composite solid electrolyte layer prepared in Example 1 of this application is shown. Detailed Implementation

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0028] As described in the background art, existing inorganic solid electrolytes suffer from difficulties in processing into films, poor flexibility and mechanical strength, low ionic conductivity, and poor safety, cycle stability, and short lifespan of solid-state batteries (such as all-solid-state lithium-ion batteries) made from them. To address these technical problems, this application provides a method for preparing a composite solid electrolyte layer, comprising: step S1, coating both sides of an aramid-based film with solid electrolyte raw materials to obtain a composite solid electrolyte layer precursor; step S2, covering at least one side of the composite solid electrolyte layer precursor with a release film to obtain a laminated structure; and step S3, subjecting the laminated structure to a first hot rolling treatment, and then peeling off the release film to obtain the composite solid electrolyte layer.

[0029] It should be noted that the aramid-based film in this application is made of polyphenylene phthalamide.

[0030] Compared to other types of base films, aramid base films possess superior flexibility, thermal stability, and mechanical properties, providing a supporting framework for the preparation of composite solid electrolyte layer precursors. This allows the resulting composite solid electrolyte layer to possess excellent flexibility, mechanical strength, and high ionic conductivity. Step S2 involves covering the surface of the composite solid electrolyte layer precursor with a release film, followed by the first hot rolling treatment in step S3. This first hot rolling treatment increases the compaction density of the composite solid electrolyte layer and improves interfacial stability. The release film inhibits direct contact between the composite solid electrolyte layer precursor and the hot rolling rollers during the first hot rolling process, reducing adhesion and contamination of the precursor, improving its processing performance, and simultaneously enhancing the purity and structural integrity of the resulting composite solid electrolyte layer. This inhibits cracking during use, thereby suppressing internal short circuits in the resulting solid-state battery and improving its cycle stability and safety.

[0031] In one implementation, step S1 further includes: melting the solid electrolyte raw material to obtain a solid electrolyte melt, coating the solid electrolyte melt on both sides of the aramid-based film to obtain a composite solid electrolyte layer precursor. Compared with other methods, the above method is advantageous in obtaining a solvent-free composite solid electrolyte layer precursor, which helps to suppress side reactions between the solid electrolyte and the solvent, suppress micropores and uneven distribution caused by solvent evaporation, suppress solvent residue, improve the uniformity and density of the obtained composite solid electrolyte layer precursor, and also improve the interaction force between the solid electrolyte melt and the aramid-based film, thereby improving the ionic conductivity, mechanical strength and structural stability of the composite solid electrolyte layer, which in turn helps to improve the cycle stability and safety of the solid battery and extend its service life.

[0032] To further suppress side reactions between the solid electrolyte and the solvent, further suppress the formation of micropores and uneven distribution due to solvent evaporation, further suppress solvent residue, and further improve the uniformity and density of the prepared composite solid electrolyte layer precursor, and to further improve the ionic conductivity, mechanical strength, and structural stability of the composite solid electrolyte layer, while also reducing production costs and environmental pollution, as one implementation method, the solid electrolyte raw material is liquid-free; or, the solid electrolyte raw material is solvent-free.

[0033] In one embodiment, the solid electrolyte raw material includes solid electrolyte powder and a binder. Step S1 further includes: mixing the solid electrolyte powder and the binder, and then melting the mixture to obtain a solid electrolyte melt. The solid electrolyte melt is then coated on both sides of the aramid-based film to obtain a composite solid electrolyte layer precursor. Compared with other methods, directly mixing the solid electrolyte powder and the binder and then melting the mixture to obtain a solid electrolyte melt is beneficial for obtaining a solvent-free solid electrolyte melt. This helps to suppress side reactions between the solid electrolyte powder and the solvent, suppress micropores and uneven distribution caused by solvent evaporation, improve the uniformity and density of the obtained composite solid electrolyte layer precursor, and also enhance the interaction force between the solid electrolyte melt and the aramid-based film. Consequently, it helps to improve the ionic conductivity, mechanical strength, and structural stability of the composite solid electrolyte layer.

[0034] To obtain a composite solid electrolyte layer precursor with a more suitable thickness and improve the utilization rate of the solid electrolyte melt, and to further improve the ionic conductivity of the composite solid electrolyte layer, as one implementation method, the coating amount of the solid electrolyte melt on the aramid-based film surface is 20 g / m². 2 ~60g / m 2 or 30g / m2 ~45g / m 2 .

[0035] In one embodiment, the melt treatment temperature is 80℃~250℃, or 100℃~250℃, for 1min~30min; or the temperature is 120℃~200℃, for 5min~20min; or the temperature is 130℃~150℃, for 10min~15min. The melt treatment temperature and time include, but are not limited to, the above ranges. Limiting them to these ranges is beneficial for improving the dispersibility of the solid electrolyte powder and the binder, for suppressing the decomposition side reactions of the binder, and for the binder to better exert its bonding effect. This, in turn, is beneficial for improving the uniformity of the solid electrolyte melt, and consequently, for improving the uniformity and density of the composite solid electrolyte layer precursor.

[0036] In one embodiment, the average particle size of the solid electrolyte powder is 0.1 μm to 10 μm, or 1 μm to 10 μm, or 2 μm to 5 μm. The average particle size of the solid electrolyte powder includes, but is not limited to, the above ranges. Limiting it to these ranges is beneficial for improving the processability of the solid electrolyte powder, for increasing the compaction density of the composite solid electrolyte layer, and for reducing the amount of binder used, thereby improving the utilization rate of the solid electrolyte raw materials and reducing production costs.

[0037] In one embodiment, the weight ratio of solid electrolyte powder to binder is (95-99):(1-5); or (97-99):(1-3). The weight ratio of solid electrolyte powder to binder includes, but is not limited to, the above range. Limiting it to this range is beneficial for improving the processability of the solid electrolyte powder, for increasing the utilization rate of both the solid electrolyte powder and the binder, for reducing the volume and interface of the composite solid electrolyte layer occupied by excessive binder, thereby improving the mechanical strength and ionic conductivity of the composite solid electrolyte layer, and also for increasing the utilization rate of both.

[0038] In one embodiment, the solid electrolyte powder is an inorganic solid electrolyte powder; in another embodiment, the inorganic solid electrolyte powder includes, but is not limited to, one or more of the group consisting of oxide solid electrolytes, sulfide solid electrolytes, and halide solid electrolytes; specifically, oxide solid electrolytes include, but are not limited to, one or more of the group consisting of perovskite solid electrolytes, lithium phosphorus oxynitride solid electrolytes, NASICON-type solid electrolytes, and garnet-type solid electrolytes; sulfide solid electrolytes include, but are not limited to, silver sulfide germanite solid electrolytes and / or Li2S-P2S5 solid electrolytes; halide solid electrolytes are selected from lithium hexachloride (Li3YCl6).

[0039] Compared to other types, the aforementioned solid electrolyte powders have higher ionic conductivity and chemical stability, which helps to improve the ionic conductivity and structural stability of the composite solid electrolyte layer, thereby improving the cycle stability and safety of solid batteries and extending their service life.

[0040] To improve the bonding performance and thermal stability of the binder, thereby further improving the processability of the composite solid electrolyte layer precursor and further improving the uniformity, density and structural stability of the electrolyte layer, as one embodiment, the binder includes, but is not limited to, one or more of the following groups: polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyacrylate (PAA), polyacrylic acid-acrylate copolymer, polyethylene ester (PET), hydrolyzed polyethylene ester derivatives, polyacrylonitrile (PAN), polyacrylonitrile-vinyl acetate copolymer, thermoplastic polyamide, styrene-butadiene rubber (SBR), hydrogenated styrene-butadiene rubber derivatives, carboxymethyl cellulose (CMC), and hydroxyl-substituted carboxymethyl cellulose derivatives.

[0041] In one implementation method, the release film is a solid, non-porous film. Compared to porous films, using a solid, non-porous film as the release film helps to suppress direct contact between the composite solid electrolyte layer precursor and the hot press roller, and helps to prevent adhesion between the composite solid electrolyte layer precursor and the hot press roller, which could cause damage and contamination. This, in turn, improves its processability, enhances the purity and structural integrity of the composite solid electrolyte layer, and ultimately improves the cycle stability and safety of the solid-state battery.

[0042] In order to better utilize the role of the release film in protecting the precursor of the composite solid electrolyte layer, thereby further inhibiting the adhesion between the precursor of the composite solid electrolyte layer and the hot roller, which would cause damage and contamination, and also to make it easier to peel off after the first hot roller pressing treatment to obtain the composite solid electrolyte layer, as one implementation method, the thickness of the release film is 10μm to 50μm.

[0043] In one embodiment, the release film is made of a first organic polymer material. Specifically, the first organic polymer material includes, but is not limited to, one or more of the group consisting of polyimide (PI), polyethylene terephthalate (PET), polyetheretherketone (PEEK), polyphenylene sulfide (PPS), and poly(p-phenylenebenzodioxazole) (PBO). Compared to other types, the aforementioned first organic polymer materials exhibit superior thermal and chemical stability. Using them as the material for the release film helps to better utilize the release film's function, thereby protecting the composite solid electrolyte layer precursor from damage and contamination during hot rolling, and ultimately improving the purity and structural integrity of the resulting composite solid electrolyte layer.

[0044] In one implementation method, the aramid-based film is a porous film. The porous structure of the aramid-based film is beneficial for providing more filling space for the electrolyte material, thereby improving the mechanical strength while enhancing the flexibility of the composite solid electrolyte layer. It also provides more channels for lithium-ion transport, thereby improving the ionic conductivity of the composite solid electrolyte layer, and ultimately improving the cycle stability and safety of the solid-state battery.

[0045] To further ensure that the solid electrolyte material fills the pores of the aramid-based membrane more fully, providing more channels for lithium-ion transport, thereby further improving the flexibility, mechanical strength, and ionic conductivity of the composite solid electrolyte layer, and further improving the cycle stability and safety of the solid battery, and also to suppress the phenomenon of decreased mechanical strength due to excessive filling of solid electrolyte material, as one implementation method, the porosity of the aramid-based membrane is 50% to 90%, or 50% to 70%.

[0046] In order to provide more suitable space for the filling of solid electrolyte materials and the transport of lithium ions, and in order to further suppress the phenomenon of decreased mechanical strength due to excessive filling of solid electrolyte materials, as an embodiment, the porosity of the aramid-based film is 60% to 65%.

[0047] To provide a more suitable space for the filling of solid electrolyte materials and the transport of lithium ions, and to suppress leakage during coating due to excessively large average pore size, as one embodiment, the average pore size of the aramid-based film is 0.1 μm to 2000 μm; or 10 μm to 1800 μm; or 50 μm to 1300 μm; or 100 μm to 1000 μm; or 200 μm to 600 μm.

[0048] In one embodiment, the thickness of the aramid-based film is 3μm to 25μm, or 8μm to 20μm, or 10μm to 15μm. The thickness of the aramid-based film includes, but is not limited to, the above ranges. Limiting it to these ranges is beneficial for the aramid-based film to possess superior mechanical strength and flexibility, and for providing a more suitable supporting framework for the preparation of the composite solid-state electrolyte layer precursor. This, in turn, helps improve the mechanical strength, flexibility, and ionic conductivity of the composite solid-state electrolyte layer, thereby improving the energy density of the solid-state battery. Furthermore, the aramid-based film of the above thickness also helps to maintain the amount of solid-state electrolyte within a suitable range, thus helping to reduce costs.

[0049] In one implementation, the thickness of the composite solid electrolyte layer precursor is 5 μm to 50 μm, or 10 μm to 40 μm, or 15 μm to 30 μm, or 20 μm to 30 μm. The thickness of the composite solid electrolyte layer precursor includes, but is not limited to, the above ranges. Limiting it to these ranges is beneficial for improving the ionic conductivity of the composite solid electrolyte layer, thereby improving the cycle stability and energy density of the solid-state battery. It also helps to improve the flexibility of the composite solid electrolyte layer while maintaining better mechanical strength, thus helping to suppress the formation of microcracks during use that could cause internal short circuits in the battery, and further improving the safety and cycle stability of the solid-state battery.

[0050] As one embodiment, the preparation method provided in this application further includes: covering at least one surface of the composite solid electrolyte layer precursor with a release film when the temperature of the composite solid electrolyte layer precursor is 50°C to 250°C, thereby obtaining a laminated structure. Compared with other methods, the above method is beneficial to improving the adhesion between the release film and the composite solid electrolyte layer precursor, thus enabling the release film to play a protective role for the composite solid electrolyte layer precursor during the subsequent first hot rolling process, and further improving the purity and structural integrity of the composite solid electrolyte layer.

[0051] As one implementation method, the preparation method of the aramid-based film includes: making C6~C 12 Aromatic diamines and C6-C 12 Aromatic diacyl chlorides undergo polymerization in a solvent to obtain aramid slurry, which is then used to prepare aramid-based films.

[0052] Aromatic diamines are aromatic compounds containing two amino groups, with their nitrogen atom directly bonded to a carbon atom on the aromatic ring. Aromatic diacyl chlorides are aromatic compounds containing two acyl chloride groups, with the acyl chloride group directly bonded to a carbon atom on the aromatic ring. By polymerizing the above-mentioned aromatic diamines and aromatic diacyl chlorides in a solvent, aramid slurry can be obtained, and then the aramid-based film of this application can be prepared using the aramid slurry. Compared with other methods, the above preparation method is advantageous for obtaining aramid-based films with excellent flexibility, thermal stability, and mechanical properties, thereby providing a more stable and superior supporting framework for the preparation of composite solid electrolyte layer precursors.

[0053] As one implementation method, the preparation method of the aramid-based film includes: making C6~C 12 Aromatic diamines and C6-C 12Aromatic diacyl chlorides undergo polymerization in a solvent to obtain a polymerization reaction system; the polymerization reaction system is neutralized to a pH of 5-7 to obtain a neutralized product system; the neutralized product system is coated onto one side of a substrate, cured, and then peeled off from the substrate to obtain an aramid-based film.

[0054] Make the above C6~C 12 Aromatic diamines and the above C6-C 12 Aromatic diacyl chlorides undergo polymerization in a solvent to obtain a polymerization reaction system. Neutralization treatment adjusts the pH of the polymerization reaction system to a suitable range, yielding a neutralized product system. This process is beneficial for neutralizing acidic substances (such as hydrogen chloride) generated during polymerization, inhibiting the degradation of polymerization products under acidic conditions, and improving subsequent processability. By coating the neutralized product system onto a substrate, allowing it to cure, and then peeling it off, an aramid-based film can be obtained, resulting in a uniformly distributed aramid-based film with high mechanical strength.

[0055] Compared to other methods, the above method for preparing aramid-based films is beneficial for improving the pore structure of aramid-based films, enhancing their chemical stability and mechanical properties (such as flexibility and mechanical strength), thereby improving the flexibility, mechanical strength, and ionic conductivity of the composite solid electrolyte layer. This, in turn, helps improve the cycle stability and safety of solid-state batteries and extends their service life.

[0056] As one implementation method, the preparation method of the aramid-based film further includes: mixing the neutralization product system with a salt and / or a second organic polymer material to obtain an aramid slurry; coating the aramid slurry onto one side surface of a substrate, curing it, and then peeling it off from the substrate to obtain the aramid-based film. Compared with other methods, the introduction of salt and / or a second organic polymer material is beneficial to improving the pore structure of the aramid-based film and to controlling its porosity and pore size within a suitable range, thereby providing more space for the filling of electrolyte materials and the transport of lithium ions. Coating the prepared aramid slurry onto the substrate, curing it, and then peeling it off to obtain the aramid-based film is beneficial to obtaining a uniformly distributed aramid-based film with high mechanical strength.

[0057] In one implementation method, the polymerization reaction temperature is 0℃ to 10℃, and the time is 1h to 8h. The polymerization reaction temperature and time include, but are not limited to, the above ranges. Limiting them to the above ranges is beneficial to suppressing the occurrence of side reactions, improving the reaction efficiency of the polymerization reaction, and thus improving the purity and yield of the aramid product in the polymerization reaction system.

[0058] In one implementation method, the molar ratio of aromatic diamine to aromatic diacyl chloride is 1:(0.99 to 1.01). Compared to other ranges, limiting the molar ratio of aromatic diamine to aromatic diacyl chloride to the above range is beneficial to improving the reaction efficiency of the polymerization reaction, suppressing the occurrence of side reactions, increasing the yield of aramid products in the polymerization reaction system, and also improving the utilization rate of both, thereby helping to reduce production costs.

[0059] In order to obtain aramid-based films with different structures, thereby further improving the flexibility, thermal stability and mechanical properties of aramid-based films, and facilitating the subsequent preparation of composite solid electrolyte layers with better performance, as one embodiment, aromatic diamines include, but are not limited to, one or more of the group consisting of m-phenylenediamine, p-phenylenediamine and 4,4'-diaminodiphenyl ether; aromatic diacyl chlorides include, but are not limited to, one or more of the group consisting of isophthaloyl chloride, terephthaloyl chloride and trimesoyl chloride.

[0060] In one embodiment, the weight ratio of the solvent to the sum of the weights of the aromatic diamine and the aromatic diacyl chloride is (70-90):(5-20). This ratio includes, but is not limited to, the range described above. Limiting it to this range is beneficial for improving the dispersibility of the aromatic diamine and the aromatic diacyl chloride, thereby improving the reaction efficiency of the polymerization reaction.

[0061] In order to further improve the dispersibility of the above-mentioned solid electrolyte raw materials, thereby further improving the reaction efficiency of the polymerization reaction, as an embodiment, the solvent includes, but is not limited to, one or more of the group consisting of N,N-dimethylacetamide (DMAC), N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO).

[0062] In order to neutralize acidic substances (such as hydrogen chloride) generated in the polymerization reaction and thus inhibit the degradation of the polymerization product (aramid) under acidic conditions, as one implementation method, the polymerization reaction system is neutralized with an alkali.

[0063] To improve the efficiency of neutralization treatment, the pH of the neutralization product system is adjusted to a more suitable range, while further inhibiting the degradation of the polymerization product under acidic conditions. As one implementation method, the molar ratio of alkali to aromatic diacyl chloride is (0.5-1):1.

[0064] To further improve the efficiency of neutralization treatment and to further adjust the pH of the neutralization product system to a more suitable range, as one implementation method, the alkali includes, but is not limited to, one or more of the group consisting of calcium hydroxide, lithium hydroxide, calcium carbonate, lithium carbonate, and calcium bicarbonate.

[0065] In one embodiment, the aramid slurry contains 3% to 10 wt% salt and 5 wt% to 20 wt% second organic polymer material. The weight percentages of salt and second organic polymer material include, but are not limited to, the above ranges. Limiting these weight percentages to the above ranges is beneficial for improving the pore structure of the aramid-based film, and for controlling its porosity and pore size within a more suitable range. This provides more space for the filling of the electrolyte material and the transport of lithium ions, thereby improving the ionic conductivity of the composite solid electrolyte layer.

[0066] In order to further improve the pore structure of the aramid-based film and further regulate its porosity and pore size within a more suitable range, thereby further improving the ionic conductivity of the composite solid electrolyte layer, as one embodiment, the salt includes, but is not limited to, one or more of the group consisting of lithium chloride, lithium fluoride, calcium chloride, carbonate, bicarbonate and lithium bis(trifluoromethanesulfonyl)imide (LITFSI).

[0067] Carbonates and bicarbonates can neutralize some of the residual acidic substances in the neutralization reaction system, generating carbon dioxide and producing bubbles, thereby forming micron- to millimeter-sized pores in situ. To further improve the pore structure of the aramid-based film, as one embodiment, carbonates include, but are not limited to, one or more of the group consisting of lithium carbonate and / or calcium carbonate; bicarbonates include, but are not limited to, one or more of the group consisting of calcium bicarbonate and / or potassium bicarbonate.

[0068] In order to further improve the pore structure of the aramid-based film and provide more space for the filling of electrolyte materials and the transport of lithium ions, thereby further improving the ionic conductivity of the composite solid electrolyte layer, as one embodiment, the second organic polymer material includes, but is not limited to, one or more of the group consisting of polyethylene oxide (PEO), polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), polyacrylic acid (PAA) and polyvinyl alcohol (PVA).

[0069] To obtain an aramid-based film with more suitable thickness, pore size, and porosity, as one implementation method, the coating amount of aramid paste on the substrate surface is 10 g / m². 2 ~80g / m 2 or 20g / m 2 ~70g / m 2 ; or 30g / m 2 ~60g / m 2 ; or 40g / m 2 ~50g / m 2 .

[0070] As one implementation method, the aramid slurry can be cured using a coagulation bath or set at 100–250°C. Compared to other methods, the above methods are advantageous in improving the efficiency of curing and setting, and in obtaining an aramid-based film with a more uniform pore distribution.

[0071] In one embodiment, the surface of the substrate is a smooth surface or a surface with protrusions. Compared with other types of substrates, using the above-mentioned type of substrate is beneficial to improving the pore structure of the aramid film and to obtaining an aramid film with a more uniform pore distribution.

[0072] In one implementation, in step S3, the temperature of the first hot rolling treatment is 50℃~250℃; or 70℃~200℃; or 100℃~180℃; or 120℃~150℃. The temperature of the first hot rolling treatment includes, but is not limited to, the above ranges. Limiting it to the above ranges is beneficial to improving the efficiency of the first hot rolling treatment, to softening the solid electrolyte material, thereby improving the interfacial bonding force between the layers in the laminated structure, and further beneficial to improving the ionic conductivity and structural stability of the composite solid electrolyte layer. At the same time, it is also beneficial to reduce the pressure and time of the first hot rolling treatment.

[0073] In order to further improve the efficiency of the first hot rolling process, further soften the solid electrolyte material, thereby further improve the interfacial bonding force between the layers in the laminated structure, and also to further reduce the pressure and time of the first hot rolling process, as one embodiment, the temperature of the first hot rolling process is 130°C to 140°C.

[0074] In one embodiment, the pressure of the first hot rolling treatment is 0.5 MPa to 50 MPa; or 5 MPa to 40 MPa; or 10 MPa to 30 MPa; or 15 MPa to 25 MPa. The pressure of the first hot rolling treatment includes, but is not limited to, the above ranges. Limiting it to the above ranges is beneficial to improving the efficiency of the first hot rolling treatment, to increasing the compaction density of the composite solid electrolyte layer, to reducing its interfacial impedance, thereby improving the ionic conductivity of the composite solid electrolyte layer, and at the same time, to suppressing damage to the aramid film caused by excessive pressure.

[0075] In one embodiment, the time for the first hot rolling treatment is 1 min to 30 min; or 5 min to 30 min; or 10 min to 25 min; or 10 min to 15 min. The time for the first hot rolling treatment includes, but is not limited to, the above ranges. Limiting it to the above ranges is beneficial to improving the compaction density of the composite solid electrolyte layer, reducing its interfacial impedance, improving its ionic conductivity, and also helps to suppress damage to the aramid film caused by excessively long hot rolling treatment.

[0076] A second aspect of this application also provides a composite solid electrolyte layer, which is prepared by the method described above for preparing the composite solid electrolyte layer provided in this application.

[0077] It should be noted that, due to the special nature of the solid electrolyte field and the limitations of existing testing and characterization methods, it is difficult to comprehensively and quantitatively characterize the complex microstructure of the composite solid electrolyte layer prepared above. However, experiments show that the composite solid electrolyte layer provided in this application has better processability, flexibility, mechanical strength, and ionic conductivity compared to traditional inorganic solid electrolyte layers. No solvent was introduced during the preparation of the composite solid electrolyte layer in this application. This suppresses side reactions between the solid electrolyte and the solvent, and also inhibits the formation of micropores and uneven distribution due to solvent evaporation, thereby improving the ionic conductivity and mechanical strength of the composite solid electrolyte layer. Furthermore, compared to other types of base films, aramid base films have superior flexibility, thermal stability, and mechanical properties. Introducing them into the composite solid electrolyte layer provides a supporting framework for the precursor preparation, enabling the composite solid electrolyte layer to possess excellent flexibility, mechanical strength, and high ionic conductivity. The introduction of release film can suppress the direct contact between the composite solid electrolyte layer precursor and the hot press roller during the hot rolling process, thereby reducing the adhesion and contamination of the composite solid electrolyte layer precursor, improving its processing performance, thereby improving the purity and structural integrity of the composite solid electrolyte layer, suppressing the generation of microcracks during use, and thus suppressing the internal short circuit of the solid battery made from it, improving the cycle stability and safety of the solid battery.

[0078] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0079] It should be noted that the composite solid electrolyte layer prepared in all embodiments of this application and the solid electrolyte layer prepared in the comparative example were subjected to the following tests: (1) Electrochemical impedance spectroscopy was performed using an electrochemical workstation at a frequency of 0.1 Hz to 1 MHz. Based on the measured electrochemical impedance, the ionic conductivity of the composite solid electrolyte layer and the solid electrolyte layer was calculated according to formula (I). (I), where σ is the ionic conductivity (mS / cm), d is the thickness of the composite solid electrolyte layer and the solid electrolyte layer (cm), Z is the electrochemical impedance (Ω), and S is the cross-sectional area of ​​the composite solid electrolyte layer and the solid electrolyte layer (cm²). 2 (2) Test the tensile strength according to the method in GB / T 1040.3-2006 "Determination of tensile properties of plastics");

[0080] The average pore size of the aramid-based membrane was measured using a pore size analyzer conforming to ASTM F316; the porosity of the aramid-based membrane was calculated according to formula (II). (II), where P is the porosity (%), m is the mass of the aramid-based film (g), and ρ is the density of the aramid-based film (g / cm³). 3 V is the volume of the aramid-based film (cm³). 3 ).

[0081] Example 1

[0082] A method for preparing a composite solid electrolyte layer includes the following steps:

[0083] (1) Preparation of aramid-based film: 441g of m-phenylenediamine was dissolved in 5.16kg of N,N-dimethylacetamide (DMAC) to obtain a mixture. Under stirring and nitrogen atmosphere, 828g of isophthaloyl chloride was added dropwise to the mixture to carry out a polymerization reaction to obtain a polymerization reaction system containing meta-aramid. The polymerization reaction system was neutralized with 245g of calcium hydroxide to obtain a neutralized product system. The obtained neutralized product system was mixed with polyethylene oxide (PEO, number average molecular weight of 8000) to obtain an aramid slurry, wherein PEO accounted for a certain percentage of the weight of the aramid slurry. The percentage content is 10wt%; the aramid slurry is coated on the polytetrafluoroethylene board; after coating, it is placed in a coagulation bath with 45% water content (the coagulation bath consists of 55wt% DMAC and 45wt% water) for curing treatment. After curing treatment, the coating layer is stretched in the transverse and longitudinal directions respectively, then washed with water, dried and shaped, and peeled off from the substrate to obtain a 15μm thick aramid base film. The porosity of the aramid base film in this embodiment is measured to be 60%, and the average pore size is 200μm.

[0084] (2) A solid electrolyte powder of Li6PS5Cl (average particle size of 3 μm) and a binder of polyethylene oxide (PEO, weight average molecular weight of 500,000) with a weight ratio of 95:5 were placed in a twin-screw extruder and melted at 180°C for 5 min to obtain a solid electrolyte melt. The solid electrolyte melt was extruded and coated on both sides of the aramid-based film obtained in step (1) to obtain a composite solid electrolyte layer precursor with a thickness of 30 μm. The coating amount of the solid electrolyte melt on the surface of the aramid-based film was 20 g / m. 2 ;

[0085] (3) When the temperature of the composite solid electrolyte layer precursor is 100℃, a polyethylene ester (PET) release film with a thickness of 20μm is covered on the side of the composite solid electrolyte layer precursor away from the aramid base film to obtain a laminated structure.

[0086] (4) The laminated structure obtained in step (3) was subjected to a first hot rolling treatment for 10 minutes at 200℃ and 50MPa. After the first hot rolling treatment was completed, the PET release film was peeled off to obtain a composite solid electrolyte layer with a thickness of 30μm.

[0087] The scanning electron microscope image of the surface of the composite solid electrolyte layer prepared in Example 1 is shown below. Figure 1 As shown, by Figure 1 It can be seen that under high temperature and high pressure, the Li6PS5Cl solid electrolyte powder softens and fills into the aramid base film, forming a dense and interconnected structure, which facilitates the rapid transport of lithium ions. The aramid base film acts as a skeleton, providing mechanical support and flexibility for the composite solid electrolyte layer.

[0088] The electrochemical impedance spectroscopy (EIS) spectrum of the composite solid electrolyte layer prepared in Example 1 is as follows: Figure 2 As shown, the impedance of the composite solid electrolyte layer is 20Ω, and its ionic conductivity is calculated to be 0.4mS / cm according to formula (I).

[0089] Example 2

[0090] A method for preparing a composite solid electrolyte layer includes the following steps:

[0091] (1) Preparation of aramid-based film: 441g of m-phenylenediamine was dissolved in 5.16kg In N,N-dimethylacetamide (DMAC), a mixture was obtained. Under stirring and a nitrogen atmosphere, 828g of isophthaloyl chloride was added dropwise to the mixture to carry out a polymerization reaction, resulting in a polymerization reaction system containing meta-aramid. The polymerization reaction system was neutralized with 200g of calcium hydroxide to obtain a neutralized product system. The obtained neutralized product system was mixed evenly with 162g of calcium bicarbonate to obtain an aramid slurry. The aramid slurry was coated onto a polytetrafluoroethylene (PTFE) substrate. After coating, the solvent was evaporated at 170°C for 3 minutes. The coated layer was then stretched in both the transverse and longitudinal directions. The residual solvent was removed by washing with water at 25°C. The substrate was dried and shaped at 100°C. After peeling off from the substrate, a 20μm thick aramid base film was obtained. The porosity of the aramid base film was measured to be 50% and the average pore size was 500μm using the same test method as in Example 1.

[0092] (2) A mixture of LATP solid electrolyte powder (average particle size of 10 μm) and binder polymethyl methacrylate (PMMA) (weight average molecular weight of 100,000) in a weight ratio of 95:5 was placed in a twin-screw extruder and melted at 180°C for 10 min to obtain a solid electrolyte melt. The solid electrolyte melt was extruded and coated onto both sides of the aramid-based film obtained in step (1) to obtain a composite solid electrolyte layer precursor with a thickness of 30 μm. The coating amount of the solid electrolyte melt on the surface of the aramid-based film was 30 g / m. 2 ;

[0093] (3) When the temperature of the composite solid electrolyte layer precursor is 150°C, a polyethylene ester (PET) release film with a thickness of 20 μm is covered on the side of the composite solid electrolyte layer precursor away from the aramid base film to obtain a laminated structure.

[0094] (4) The laminated structure obtained in step (3) was subjected to a first hot rolling treatment for 10 minutes at 250℃ and 50MPa. After the first hot rolling treatment was completed, the PET release film was peeled off to obtain a composite solid electrolyte layer with a thickness of 35μm.

[0095] Example 3

[0096] A method for preparing a composite solid electrolyte layer includes the following steps:

[0097] (1) Preparation of aramid-based film: 441g of m-phenylenediamine was dissolved in 5.16kg of N,N-dimethylacetamide (DMAC) to obtain a mixture. Under stirring and a nitrogen atmosphere, 828g of isophthaloyl chloride was added dropwise to the mixture to carry out a polymerization reaction, resulting in a polymerization reaction system containing meta-aramid. The polymerization reaction system was neutralized with 245g of calcium hydroxide powder to obtain a neutralized product system. The neutralized product system was coated onto a polytetrafluoroethylene (PTFE) vinyl plate, wherein the PTFE vinyl plate has two-dimensional closely packed cylindrical protrusions with a diameter of 1mm and a height of 100μm. The resulting aramid-based film has uniformly sized and evenly distributed pores. After coating, it is dried in a vacuum oven at 100°C for 30 minutes. After washing with water, it is peeled off from the substrate to obtain a 15μm thick aramid-based film. The porosity of the aramid-based film is measured to be 70%, and the average pore size is 850μm. The aramid-based film has a multi-level structure of macropores and micropores, and the volume ratio of macropores to micropores is 5:3. It should be noted that in this application, macropores refer to pores with a pore size > 1μm, and micropores refer to pores with a pore size < 1μm.

[0098] (2) A mixture of Li6PS5Cl solid electrolyte powder (average particle size of 5 μm) with binder polyethylene oxide (PEO, weight average molecular weight of 500,000) and lithium bis(trifluoromethanesulfonyl)imide (LITFSI) in a weight ratio of 95:5 (PEO to LITFSI weight ratio of 1:0.3) was placed in a twin-screw extruder; it was melted at 100°C for 30 min to obtain a solid electrolyte melt; the solid electrolyte melt was extruded and coated on both sides of the aramid-based film obtained in step (1) to obtain a composite solid electrolyte layer precursor with a thickness of 30 μm, wherein the coating amount of the solid electrolyte melt on the surface of the aramid-based film was 20 g / m 2 ;

[0099] (3) When the temperature of the composite solid electrolyte layer precursor is 100℃, a polyethylene ester (PET) release film with a thickness of 20μm is covered on the side of the composite solid electrolyte layer precursor away from the aramid base film to obtain a laminated structure.

[0100] (4) The laminated structure obtained in step (3) was subjected to a first hot rolling treatment for 10 minutes at 50℃ and 50MPa. After the first hot rolling treatment was completed, the PET release film was peeled off to obtain a composite solid electrolyte layer with a thickness of 28μm.

[0101] Example 4

[0102] The difference from Example 1 is that step (2) is to melt at 80°C for 30 minutes to obtain a solid electrolyte melt, and the remaining steps are the same as in Example 1.

[0103] Example 5

[0104] The difference from Example 1 is that step (2) involves melting at 250°C for 1 minute to obtain a solid electrolyte melt, while the remaining steps are the same as in Example 1.

[0105] Example 6

[0106] The difference from Example 1 is that step (2) is to melt at 40°C for 45 minutes to obtain a solid electrolyte melt, and the remaining steps are the same as in Example 1.

[0107] Example 7

[0108] The difference from Example 1 is that in step (1), the weight percentage of polyethylene oxide (PEO) in the aramid slurry is 5 wt%, and the porosity of the aramid-based film obtained therefrom is 50%, with an average pore size of 20 μm. The remaining steps are the same as in Example 1.

[0109] Example 8

[0110] The difference from Example 1 is that in step (1), the weight percentage of polyethylene oxide (PEO) in the aramid slurry is 15wt%, the porosity of the aramid base film obtained in step (1) is 90%, the average pore size is 21μm, and the remaining steps are the same as in Example 1.

[0111] Example 9

[0112] The difference from Example 1 is that in step (1), polyethylene oxide (PEO) was not introduced into the aramid slurry, and the coagulation bath consisted of 35 wt% DMAC and 65 wt% water. The porosity of the aramid-based membrane obtained was 45%, and the average pore size was 0.2 μm. The remaining steps were the same as in Example 1.

[0113] Example 10

[0114] The difference from Example 1 is that in step (2), the weight ratio of Li6PS5Cl solid electrolyte powder to binder polyethylene oxide (PEO) is 99:1, and the remaining steps are the same as in Example 1.

[0115] Example 11

[0116] The difference from Example 1 is that in step (2), the weight ratio of Li6PS5Cl solid electrolyte powder to binder polyethylene oxide (PEO) is 90:10, and the remaining steps are the same as in Example 1.

[0117] Example 12

[0118] The difference from Example 1 is that in step (4), the temperature of the first hot roller pressing treatment is 250°C, the pressure is 0.5MPa, and the time is 30min. The remaining steps are the same as in Example 1.

[0119] Example 13

[0120] The difference from Example 1 is that in step (4), the temperature of the first hot roller pressing treatment is 130°C, the pressure is 25MPa, and the time is 15min. The remaining steps are the same as in Example 1.

[0121] Example 14

[0122] The difference from Example 1 is that in step (4), the temperature of the first hot roller pressing treatment is 40°C, the pressure is 0.3MPa, and the time is 35min. The remaining steps are the same as in Example 1.

[0123] Comparative Example 1

[0124] The difference from Example 1 is that steps (2) and (3) are omitted. Li6PS5Cl solid electrolyte powder and polyethylene oxide (PEO, weight average molecular weight 500,000) in a weight ratio of 95:5 are dissolved in acetonitrile to obtain a slurry with a solid content of 50wt%, and then... 2 The coating amount is to coat the slurry onto both sides of the aramid-based film obtained in step (1), and dry it at 50°C for 1 hour to obtain a solid electrolyte layer precursor with a thickness of 30 μm; the remaining steps are the same as in Example 1.

[0125] Comparative Example 2

[0126] The difference from Example 1 is that step (3) is omitted, and the composite solid electrolyte layer precursor obtained in step (2) is directly subjected to the first hot rolling treatment. This comparative example does not use a release film to protect the composite solid electrolyte layer precursor, which causes the composite solid electrolyte layer precursor to stick to the hot rolling roller, making it impossible to obtain a solid electrolyte layer.

[0127] The test results are shown in Table 1.

[0128] Table 1

[0129]

[0130] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0131] Comparing Example 1 and Comparative Example 1, it can be seen that under the same aramid-based film and the same hot rolling process, the thickness and tensile strength of the solid electrolyte layer do not change significantly. However, the ionic conductivity of Example 1 is much higher than that of Comparative Example 1. This is because Example 1 did not introduce a solvent when preparing the composite solid electrolyte layer, thereby suppressing side reactions between the solid electrolyte and the solvent, suppressing the formation of micropores and uneven distribution due to solvent evaporation, and thus improving the uniformity and density of the obtained composite solid electrolyte layer, thereby improving the ionic conductivity of the composite solid electrolyte layer. In addition, compared with Comparative Example 1, Example 1 did not introduce a solvent, thereby reducing production costs, reducing waste liquid generation, and reducing waste liquid treatment costs.

[0132] Comparing Example 1 and Comparative Example 2, it can be seen that the introduction of the release film can suppress the direct contact between the composite solid electrolyte layer precursor and the hot press roller during the first hot roll pressing process, improve its processing performance, and at the same time reduce the adhesion and contamination of the composite solid electrolyte layer precursor, thereby improving the purity and structural integrity of the composite solid electrolyte layer.

[0133] Comparing Examples 1 to 3, it can be seen that the ionic conductivity of Example 2 is worse than that of Examples 1 and 3. This is because Examples 1 and 3 use sulfide solid electrolytes, while Example 2 uses oxide solid electrolytes. The ionic conductivity of sulfide solid electrolytes is higher than that of oxide solid electrolytes. Therefore, the ionic conductivity of Example 2 is lower than that of Examples 1 and 3. Thus, it can be seen that the preparation method of the composite solid electrolyte layer provided in this application is applicable to various types of inorganic solid electrolytes.

[0134] Comparing Examples 1, 4 to 6, it can be seen that the melting temperature in Example 5 is the maximum value within the preferred range of this application. According to the data in Table 1, at this temperature, due to the increase in side reactions between the binder and electrolyte powder, the ionic conductivity and mechanical strength of the composite solid electrolyte layer begin to decrease. In Example 6, the melting temperature is too low (outside the preferred range of this application), resulting in incomplete melting of the binder and solid electrolyte powder, failing to form a continuous ion transport path, thus leading to a decrease in ionic conductivity. Simultaneously, due to incomplete melting of the binder, the adhesion between the solid electrolytes is insufficient, resulting in a decrease in the mechanical strength of the composite solid electrolyte layer. Therefore, compared to other ranges, limiting the melting temperature and time to the range described above is beneficial for improving the dispersibility of the solid electrolyte powder and binder, suppressing the decomposition side reactions of the binder, allowing the binder to better exert its adhesive effect, and improving the uniformity of the solid electrolyte melt. This, in turn, improves the uniformity and density of the composite solid electrolyte layer, and consequently, enhances its mechanical strength and ionic conductivity.

[0135] Comparing Examples 1, 7 to 9, it can be seen that in Example 8, due to the higher porosity of its aramid-based film, the ionic conductivity is correspondingly increased. However, with the increase in porosity, the structural stability of the aramid-based film decreases, resulting in a significant decrease in the mechanical strength of the composite solid electrolyte. In Example 9, the aramid-based film has a lower porosity and a smaller average pore size (both are outside the preferred range of this application), which restricts the ion transport path and consequently reduces its ionic conductivity. Therefore, compared to other ranges, limiting the porosity and average pore size of the aramid-based film to the ranges described above in this application is beneficial for providing more filling space for the solid electrolyte material, allowing it to fill the pores of the aramid-based film more fully. This provides more channels for lithium ion transport, thereby improving the flexibility, mechanical strength, and ionic conductivity of the composite solid electrolyte layer. It also helps to suppress the decrease in mechanical strength caused by excessive filling of the solid electrolyte material.

[0136] Comparing Examples 1, 10, and 11, it can be seen that Example 11, due to the excessive amount of binder added (outside the preferred range of this application), results in increased thickness and decreased tensile strength. Furthermore, the excessive binder occupies the filling space of the inorganic solid electrolyte, leading to a decrease in its ionic conductivity. Therefore, compared to other ranges, limiting the weight ratio of solid electrolyte powder to binder within the range described above is beneficial in two ways: firstly, it improves the utilization rate of both components and the processability of the solid electrolyte powder; secondly, it reduces the volume and interface of the composite solid electrolyte layer occupied by excessive binder, thereby improving the mechanical strength and ionic conductivity of the composite solid electrolyte layer.

[0137] Comparing Examples 1, 12 to 14, it can be seen that in Example 14, the relatively low temperature and pressure of the hot rolling process (all values ​​outside the preferred range of this application) resulted in insufficient adhesion between the interfaces of the composite solid electrolyte layer, forming voids and defects. This increased the resistance to ion migration, leading to a decrease in conductivity. Therefore, compared to other ranges, limiting the temperature, pressure, and time of the first hot rolling process to the ranges described above is beneficial for softening the solid electrolyte material, improving the interfacial bonding force between layers in the laminated structure, increasing the compaction density of the composite solid electrolyte layer, reducing its interfacial impedance, and consequently improving the ionic conductivity and structural stability of the composite solid electrolyte layer.

[0138] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0139] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a composite solid electrolyte layer, characterized in that, The preparation method includes: Step S1: Coat both sides of the aramid-based membrane with solid electrolyte raw materials to obtain a composite solid electrolyte layer precursor. Step S2: A release film is coated on at least one surface of the composite solid electrolyte layer precursor to obtain a laminated structure; Step S3: Perform a first hot rolling process on the laminated structure, and then peel off the release film to obtain the composite solid electrolyte layer.

2. The method for preparing the composite solid electrolyte layer according to claim 1, characterized in that, The solid electrolyte raw material in step S1 does not contain liquid.

3. The method for preparing the composite solid electrolyte layer according to claim 1, characterized in that, The solid electrolyte raw material in step S1 does not contain solvent.

4. The method for preparing the composite solid electrolyte layer according to claim 3, characterized in that, Step S1 further includes: melting the solid electrolyte raw material to obtain a solid electrolyte melt, coating the solid electrolyte melt on both sides of the aramid base film to obtain the composite solid electrolyte layer precursor.

5. The method for preparing the composite solid electrolyte layer according to claim 4, characterized in that, The amount of the solid electrolyte melt coated on the surface of the aramid-based film is 20 g / m. 2 ~60g / m 2 .

6. The method for preparing the composite solid electrolyte layer according to claim 4, characterized in that, The melting treatment is performed at a temperature of 80℃ to 250℃ for a time of 1 min to 30 min.

7. The method for preparing the composite solid electrolyte layer according to claim 1, characterized in that, The solid electrolyte raw material includes solid electrolyte powder and binder, and the weight ratio of solid electrolyte powder to binder is (95-99):(1-5).

8. The method for preparing the composite solid electrolyte layer according to claim 7, characterized in that, The solid electrolyte powder is an inorganic solid electrolyte powder; the inorganic solid electrolyte powder is selected from one or more of the group consisting of oxide solid electrolytes, sulfide solid electrolytes and halide solid electrolytes.

9. The method for preparing the composite solid electrolyte layer according to claim 1, characterized in that, The release film is a solid film without pores; and / or, the thickness of the release film is 10 μm to 50 μm.

10. The method for preparing the composite solid electrolyte layer according to claim 1, characterized in that, The release film is made of a first organic polymer material, which is selected from one or more of the group consisting of polyimide, polyethylene terephthalate, polyether ether ketone, polyphenylene sulfide, and poly(p-phenylenebenzodioxazole).

11. The method for preparing the composite solid electrolyte layer according to claim 1, characterized in that, The aramid-based membrane is a porous membrane; the porosity of the aramid-based membrane is 50% to 90%.

12. The method for preparing the composite solid electrolyte layer according to claim 1, characterized in that, The aramid-based film has an average pore size of 0.1 μm to 2000 μm; and / or, the aramid-based film has a thickness of 3 μm to 25 μm.

13. The method for preparing the composite solid electrolyte layer according to claim 1, characterized in that, The thickness of the composite solid electrolyte layer precursor is 5 μm to 50 μm.

14. The method for preparing the composite solid electrolyte layer according to claim 1, characterized in that, Step S2 further includes: when the temperature of the composite solid electrolyte layer precursor is 50°C to 250°C, covering at least one side surface of the composite solid electrolyte layer precursor with the release film to obtain the laminated structure.

15. The method for preparing the composite solid electrolyte layer according to claim 1, characterized in that, In step S3, the temperature of the first hot rolling treatment is 50℃~250℃; and / or, the pressure of the first hot rolling treatment is 0.5MPa~50MPa; and / or, the time of the first hot rolling treatment is 1min~30min.

16. A composite solid electrolyte layer, characterized in that, The composite solid electrolyte layer is prepared by the method described in any one of claims 1 to 15.

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