Composite solid electrolyte membrane and method for manufacturing the same

Abstract

The application relates to the technical field of solid-state batteries, in particular to a composite solid-state electrolyte film and a preparation method thereof. The composite solid-state electrolyte film provided by the application comprises a binder and a sulfide solid-state electrolyte, the binder comprises modified polyisobutylene and polytetrafluoroethylene, wherein the modified polyisobutylene is obtained by polymerization reaction of methyl methacrylate and lithium acrylate with an oxygen negative ion macromolecule prepared from high-activity polyisobutylene as an initiator; the sulfide electrolyte comprises any one of Li7P3S 11 , Li3PS4, Li 10 GeP2S 12 , Li 10 GeP2S 12 , Li6PS5Cl and Li 7‑x PS 6‑x Cl x ; the electrolyte film prepared by the application effectively solves the problem of side reactions of the polytetrafluoroethylene binder in a dry electrode, and has certain mechanical strength, high ionic conductivity and low thickness.

Description

Technical Field

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

[0002] Solid-state electrolyte membranes (SEMs) are a core component of solid-state batteries, serving to separate the positive and negative electrodes to prevent short circuits, allowing ions to pass through while isolating electrons. Sulfide solid-state electrolytes have attracted widespread attention due to their high room-temperature ionic conductivity, and they can form good interfacial contact with electrode materials under certain pressure. An ideal sulfide electrolyte membrane should possess low thickness, good mechanical properties, and high ionic conductivity to improve battery energy density, extend lifespan, and enhance safety. Therefore, achieving a superior electrolyte membrane requires finding a balance between ionic conductivity, mechanical strength, and thickness.

[0003] Currently, the commonly used method for preparing sulfide electrolyte membranes is wet membrane fabrication. However, because sulfide electrolytes are extremely sensitive to polar solvents, the ionic conductivity of wet-processed electrolyte membranes is significantly reduced. Dry membrane fabrication involves mixing a binder with solid electrolyte powder and applying shear force to fibrousize the binder, thereby forming the electrolyte membrane. Compared to wet membrane fabrication, dry membrane fabrication does not require organic solvents, making it environmentally friendly and saving on material, time, and labor costs. Furthermore, many current sulfide electrolyte membranes are typically quite thick and have low ionic conductivity, limiting the potential for further increases in the energy density of assembled all-solid-state batteries. Therefore, developing sulfide electrolyte membranes that combine low thickness, ideal mechanical properties, and high ionic conductivity is crucial.

[0004] Polytetrafluoroethylene (PTFE) is commonly used as a binder in dry membrane fabrication. However, PTFE is prone to reduction reactions at low potentials, and the side of the sulfide electrolyte membrane with a high PTFE content that contacts the negative electrode consumes a large amount of active lithium during the negative electrode lithiation process. This leads to poor contact between the electrolyte membrane and the negative electrode, causing the solid electrolyte membrane to become loose, damaging the battery structure, and degrading battery performance. However, sulfide electrolyte membranes prepared with a small amount of PTFE binder have poor mechanical properties, and their thickness cannot be reduced. Summary of the Invention

[0005] The purpose of this invention is to provide a composite solid electrolyte membrane and its preparation method to solve the problems mentioned in the background art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] Step 1:

[0008] In an argon atmosphere, modified polyisobutylene binder and sulfide electrolyte particles are ground and mixed to obtain composite solid electrolyte powder;

[0009] Step 2:

[0010] A composite solid electrolyte membrane is obtained by adding polytetrafluoroethylene binder to the composite solid electrolyte powder, shearing and mixing, hot extruding to 150~300μm, and rolling to thin to 20~40μm.

[0011] Furthermore, in step 1, the preparation method of the modified polyisobutylene binder includes the following steps:

[0012] S1: Under -5~0°C ice-water bath conditions, acrylic acid is added to lithium hydroxide and stirred for 5~10 min to obtain lithium acrylate;

[0013] S2: Under ice-water bath conditions of -5~0°C, sodium borohydride and boron trifluoride-diethyl ether solution were added as solvent in anhydrous tetrahydrofuran and stirred for 3~4 h. Then, tetrahydrofuran solution of highly active polyisobutylene was added and reacted for 20~24 h. The pH of the system was adjusted to 10~12 with sodium hydroxide solution, and hydrogen peroxide solution was added dropwise. The reaction was carried out for 8~10 h. The mixture was washed with water and extracted with diethyl ether. The organic layer was dried, the solvent was removed by rotary evaporation, and the product was dried under vacuum to obtain hydroxyl-terminated polyisobutylene.

[0014] S3: Under nitrogen atmosphere, hydroxyl-terminated polyisobutylene is dispersed in anhydrous tetrahydrofuran and stirred until dissolved. Potassium hydride washed with anhydrous tetrahydrofuran is added, and the mixture is reacted at 45-50°C for 10-12 hours to generate a polyisobutylene-based macromolecular initiator.

[0015] S4: Under argon atmosphere, polyisobutylene macromolecular initiator and methyl methacrylate are dispersed in anhydrous tetrahydrofuran and reacted at 25-30℃ for 2-3 hours. After keeping warm, lithium acrylate is added and the reaction continues for another 2-3 hours. Then, anhydrous methanol is added to terminate the reaction. The reaction solution is added to ice-cold n-hexane to precipitate and vacuum dried to constant weight to obtain modified polyisobutylene binder.

[0016] Furthermore, the polyisobutylene macromolecular initiator, methyl methacrylate, and lithium acrylate react in a weight ratio of (50~60):(5~20):(30~35).

[0017] Furthermore, in step 1, the grinding and mixing speed is 1500~2500 rpm, and the grinding and mixing time is 50~70 min.

[0018] Furthermore, in step 2, the rotation speed of the shear mixing is 3000~5000 rpm, and the shear mixing time is 30~60 min.

[0019] Furthermore, in step 2, the hot extrusion temperature is 80~100℃.

[0020] Furthermore, in step 2, the components in the composite solid electrolyte membrane are, by weight percentage, 0.5-2% modified polyisobutylene binder, 0.05-0.1% polytetrafluoroethylene binder, and the remainder is sulfide electrolyte particles.

[0021] Furthermore, in step 2, the sulfide electrolyte is Li7P3S. 11 Li3PS4, Li 10 GeP2S 12 Li 10 GeP2S 12 Li 7-x PS 6-x Cl x Any one of them.

[0022] Furthermore, the particle size D of the sulfide solid electrolyte 50 The range is 1~10μm.

[0023] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The present invention provides a composite solid electrolyte membrane, comprising a binder and a sulfide solid electrolyte; the binder is modified polyisobutylene and polytetrafluoroethylene. The sulfide solid electrolyte provides good ionic conductivity to the solid electrolyte membrane. By using the sulfide electrolyte as the main raw material of the solid electrolyte membrane, adding a small amount of modified polyisobutylene binder and a very small amount of polytetrafluoroethylene, a high ionic conductivity can be achieved.

[0024] Modified polyisobutylene is produced by reacting highly reactive polyisobutylene with methyl methacrylate and lithium acrylate via hydroboration oxidation, anionic polymerization, and hydrazine oxidation. This invention uses highly reactive polyisobutylene with a molecular weight of 900-1150 g / mol as the raw material, which possesses both good reactivity and excellent mechanical properties. Modified polyisobutylene exhibits good bonding properties; the presence of lithium acrylate in its molecular chain segments constructs a better conductive binder network. The moderate molecular weight and uniform binder distribution ensure minimal loss of ionic conductivity in the sulfide electrolyte particles. There are no significant side reactions among the modified polyisobutylene, polytetrafluoroethylene, and sulfide electrolyte. By applying shear force and mixing, extruding, and calendering, an independently self-supporting sulfide electrolyte membrane can be prepared. During battery charging and discharging, its high mechanical strength and flexibility maintain stable battery operation and the integrity of the electrolyte membrane structure, improving cycle stability.

[0025] Compared with the traditional polytetrafluoroethylene (PTFE) preparation of sulfide electrolyte membranes, the use of mixed dual binders not only reduces the content of conventional PTFE binders in sulfide electrolyte membranes, but also allows the sulfide electrolyte to still be fiberized into a membrane through the dual binders. This results in a composite solid electrolyte membrane with improved strength and further reduced thickness. It also solves the shortcomings of PTFE binders in dry electrodes and improves the adhesion and electrochemical stability of sulfide electrolyte membranes.

[0026] Furthermore, the modified polyisobutylene binder and polytetrafluoroethylene binder used in this invention have lower operating temperatures, resulting in a lower film formation temperature for the composite solid electrolyte membrane; the resulting solid electrolyte membrane is thinner, which can improve the energy density of the battery. Attached Figure Description

[0027] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0028] Figure 1 These are electron microscope images of the composite solid electrolyte membranes in Embodiment 1(a) and Comparative Example 1(b) of the present invention;

[0029] Figure 2 This is a long-cycle test diagram of a solid-state battery made of a composite solid-state electrolyte membrane in Embodiment 1 of the present invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Materials and sources used in this invention: The sulfide electrolyte is Li 5.5 PS 4.5 Cl 1.5 Particle size D 50 The molecular weight is 5μm and it comes from Wuhan Tianshi Kefeng New Energy Technology Co., Ltd.; the high-activity polyisobutylene comes from Zhangjiagang Fengtong Chemical Co., Ltd., with an average molecular weight of 900~1150; the polytetrafluoroethylene comes from DuPont, USA, with the product number MP1300; and the polyisobutylene binder comes from Wuxi Bingju Trading Co., Ltd., with the product number JINEX6130.

[0032] Example 1: A method for preparing a composite solid electrolyte membrane, comprising the following steps:

[0033] Step 1:

[0034] S1: Under -5°C ice-water bath conditions, acrylic acid was added to lithium hydroxide and stirred for 5 min to obtain lithium acrylate;

[0035] S2: Under -5°C ice-water bath conditions, sodium borohydride and boron trifluoride-ethyl ether solution were added to anhydrous tetrahydrofuran as solvent and stirred for 3 h. Then, a tetrahydrofuran solution of highly active polyisobutylene was added and reacted for 20 h. The pH of the system was adjusted to 10 with sodium hydroxide solution, and hydrogen peroxide solution was added dropwise. The reaction was carried out for 8 h. The mixture was washed with water and extracted with ether. The organic layer was dried, the solvent was removed by rotary evaporation, and the product was dried under vacuum to obtain hydroxyl-terminated polyisobutylene.

[0036] S3: Under nitrogen atmosphere, hydroxyl-terminated polyisobutylene is dispersed in anhydrous tetrahydrofuran and stirred until dissolved. Potassium hydride washed with anhydrous tetrahydrofuran is added, and the mixture is reacted at 45°C for 10 hours to generate a polyisobutylene-based macromolecular initiator.

[0037] S4: Under argon atmosphere, polyisobutylene macromolecular initiator and methyl methacrylate were dispersed in anhydrous tetrahydrofuran and reacted at 25°C for 2 hours. After maintaining the temperature, lithium acrylate was added and the reaction continued for another 2 hours. Anhydrous methanol was then added to terminate the reaction. The reaction solution was added to ice-cold n-hexane to precipitate the product and vacuum dried to constant weight to obtain modified polyisobutylene binder. The polyisobutylene macromolecular initiator, methyl methacrylate, and lithium acrylate were reacted in a weight ratio of 50:20:30.

[0038] Step 2:

[0039] In an argon atmosphere, modified polyisobutylene binder and sulfide electrolyte particles are ground and mixed to obtain a composite solid electrolyte powder. The grinding and mixing speed is 1500 rpm and the grinding and mixing time is 50 min. Polytetrafluoroethylene binder is added to the composite solid electrolyte powder and sheared and mixed at a speed of 3000 rpm for 30 min. The mixture is then hot-extruded at 80°C to a thickness of 150 μm and thinned by rolling to obtain a composite solid electrolyte membrane. The composite solid electrolyte membrane contains, by weight percentage, 2% modified polyisobutylene binder, 0.1% polytetrafluoroethylene binder, and the remainder being sulfide electrolyte particles.

[0040] Example 2: A method for preparing a composite solid electrolyte membrane, comprising the following steps:

[0041] Step 1:

[0042] S1: Under -3°C ice-water bath conditions, acrylic acid was added to lithium hydroxide and the mixture was stirred for 8 min to obtain lithium acrylate;

[0043] S2: Under -4°C ice-water bath conditions, sodium borohydride and boron trifluoride-diethyl ether solution were added to anhydrous tetrahydrofuran as solvent and stirred for 3.5 h. Then, a tetrahydrofuran solution of highly active polyisobutylene was added and reacted for 23 h. The pH of the system was adjusted to 11.5 with sodium hydroxide solution, and hydrogen peroxide solution was added dropwise. The reaction was carried out for 9 h. The mixture was washed with water and extracted with diethyl ether. The organic layer was dried, the solvent was removed by rotary evaporation, and the product was dried under vacuum to obtain hydroxyl-terminated polyisobutylene.

[0044] S3: Under nitrogen atmosphere, hydroxyl-terminated polyisobutylene is dispersed in anhydrous tetrahydrofuran and stirred until dissolved. Potassium hydride washed with anhydrous tetrahydrofuran is added, and the mixture is reacted at 48°C for 11 hours to generate a polyisobutylene-based macromolecular initiator.

[0045] S4: Under argon atmosphere, polyisobutylene macromolecular initiator and methyl methacrylate were dispersed in anhydrous tetrahydrofuran and reacted at 28°C for 2.5 h. After maintaining the temperature, lithium acrylate was added and the reaction continued for another 2.5 h. Anhydrous methanol was then added to terminate the reaction. The reaction solution was added to ice-cold n-hexane to precipitate the product and dried under vacuum to constant weight to obtain modified polyisobutylene binder. The polyisobutylene macromolecular initiator, methyl methacrylate, and lithium acrylate were reacted in a weight ratio of 57:10:33.

[0046] Step 2:

[0047] In an argon atmosphere, modified polyisobutylene binder and sulfide electrolyte particles are ground and mixed to obtain a composite solid electrolyte powder. The grinding and mixing speed is 2000 rpm and the grinding and mixing time is 60 min. Polytetrafluoroethylene binder is added to the composite solid electrolyte powder and sheared and mixed at a speed of 4000 rpm for 45 min. The mixture is then hot-extruded at 90°C to a thickness of 280 μm and thinned by rolling to obtain a composite solid electrolyte membrane. The composite solid electrolyte membrane contains, by weight percentage, 1.5% modified polyisobutylene binder, 0.08% polytetrafluoroethylene binder, and the remainder being sulfide electrolyte particles.

[0048] Example 3: A method for preparing a composite solid electrolyte membrane, comprising the following steps:

[0049] Step 1:

[0050] S1: Under 0°C ice-water bath conditions, acrylic acid was added to lithium hydroxide and stirred for 10 min to obtain lithium acrylate;

[0051] S2: Under 0°C ice-water bath conditions, sodium borohydride and boron trifluoride-ethyl ether solution were added to anhydrous tetrahydrofuran as solvent and stirred for 4 h. Then, a tetrahydrofuran solution of highly active polyisobutylene was added and reacted for 24 h. The pH of the system was adjusted to 12 with sodium hydroxide solution, and hydrogen peroxide solution was added dropwise. The reaction was carried out for 10 h. The mixture was washed with water and extracted with ether. The organic layer was dried, the solvent was removed by rotary evaporation, and the product was dried under vacuum to obtain hydroxyl-terminated polyisobutylene.

[0052] S3: Under nitrogen atmosphere, hydroxyl-terminated polyisobutylene is dispersed in anhydrous tetrahydrofuran and stirred until dissolved. Potassium hydride washed with anhydrous tetrahydrofuran is added, and the mixture is reacted at 50°C for 12 hours to generate a polyisobutylene-based macromolecular initiator.

[0053] S4: Under argon atmosphere, polyisobutylene macromolecular initiator and methyl methacrylate were dispersed in anhydrous tetrahydrofuran and reacted at 30°C for 3 hours. After maintaining the temperature, lithium acrylate was added and the reaction continued for another 3 hours. Anhydrous methanol was then added to terminate the reaction. The reaction solution was added to ice-cold n-hexane to precipitate the product and dried under vacuum to constant weight to obtain modified polyisobutylene binder. The polyisobutylene macromolecular initiator, methyl methacrylate, and lithium acrylate were reacted in a weight ratio of 60:5:35.

[0054] Step 2:

[0055] In an argon atmosphere, modified polyisobutylene binder and sulfide electrolyte particles are ground and mixed to obtain a composite solid electrolyte powder. The grinding and mixing speed is 2500 rpm and the grinding and mixing time is 70 min. Polytetrafluoroethylene binder is added to the composite solid electrolyte powder and sheared and mixed at a speed of 5000 rpm for 60 min. The mixture is then hot-extruded at 100°C to a thickness of 300 μm and thinned by rolling to obtain a composite solid electrolyte membrane. The components in the composite solid electrolyte membrane are, by weight percentage, 0.5% modified polyisobutylene binder, 0.1% polytetrafluoroethylene binder, and the remainder is sulfide electrolyte particles.

[0056] Comparative Example 1: No modified polyisobutylene binder was added, and all other parameters were the same as in Example 1.

[0057] Under an argon atmosphere, sulfide electrolyte particles are ground at a speed of 1500 rpm for 50 min. Polytetrafluoroethylene (PTFE) binder is added and sheared at a speed of 3000 rpm for 30 min. The mixture is then hot-extruded at 80°C to a thickness of 150 μm, followed by roll thinning to obtain a composite solid electrolyte membrane. The composite solid electrolyte membrane contains, by weight percentage, 0.1% PTFE binder and 99.9% sulfide electrolyte particles.

[0058] Experiment: The performance of the composite solid electrolyte membrane was tested, and the experimental results are shown in Table 1.

[0059] Composite solid electrolyte membrane thickness test: The thickness of the composite solid electrolyte membranes in Examples 1-3 was tested using SEM.

[0060] Ionic conductivity test: At 30°C, the ionic conductivity of the composite solid electrolyte membranes prepared in Examples 1-3 was tested by assembling a sulfide electrolyte membrane with a stainless steel sheet as a blocking battery.

[0061] Cyclic performance testing: At 25°C, the composite solid electrolyte membrane prepared in Example 1 was matched with NCM90 cathode material and pre-lithiated Al-based anode, and the assembled battery was tested on the LAND battery testing system. The battery's long-cycle specific capacity was tested under a current density of 0.1C.

[0062] Table 1. Test results of various properties of composite solid electrolyte membrane

[0063]

[0064] Conclusion: The data from Examples 1-3 show that the composite solid electrolyte membrane prepared by this invention has both high ionic conductivity and low thickness.

[0065] Data from Example 1 and Comparative Example 1 show that, compared to Comparative Example 1 where only polytetrafluoroethylene (PTFE) was added as a binder, the addition of modified polyisobutylene (PIB) binder in Example 1 resulted in a more uniform distribution of the moderately molecular weight PIB in the sulfide electrolyte particles, with less reduction in ionic conductivity. The addition of PIB significantly reduced the thickness of the composite solid electrolyte membrane, demonstrating that the mechanical properties of the composite solid electrolyte membrane were improved. During the roll forming thinning process, the dual-binder fiberization system ensured that the composite electrolyte membrane did not crack during thinning, thus reducing its thickness.

[0066] Electrochemical data from Example 1 show that the composite solid electrolyte membrane prepared in this invention can maintain structural integrity and exhibit minimal capacity loss during long-term battery cycling. In contrast, the battery assembled with the composite solid electrolyte membrane in Comparative Example 1 experienced a short circuit in the first cycle due to the poor strength of the composite solid electrolyte membrane, failing to maintain stability during long-term battery cycling.

[0067] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0068] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a composite solid electrolyte membrane, characterized in that: Includes the following steps: Step 1: In an argon atmosphere, modified polyisobutylene binder and sulfide electrolyte particles are ground and mixed to obtain composite solid electrolyte powder; The preparation method of the modified polyisobutylene adhesive includes the following steps: S1: Under -5~0°C ice-water bath conditions, acrylic acid is added to lithium hydroxide and stirred for 5~10 min to obtain lithium acrylate; S2: Under ice-water bath conditions of -5~0°C, sodium borohydride and boron trifluoride-diethyl ether solution were added as solvent in anhydrous tetrahydrofuran and stirred for 3~4 h. Then, tetrahydrofuran solution of highly active polyisobutylene was added and reacted for 20~24 h. The pH of the system was adjusted to 10~12 with sodium hydroxide solution, and hydrogen peroxide solution was added dropwise. The reaction was carried out for 8~10 h. The mixture was washed with water and extracted with diethyl ether. The organic layer was dried, the solvent was removed by rotary evaporation, and the product was dried under vacuum to obtain hydroxyl-terminated polyisobutylene. S3: Under nitrogen atmosphere, hydroxyl-terminated polyisobutylene is dispersed in anhydrous tetrahydrofuran and stirred until dissolved. Potassium hydride washed with anhydrous tetrahydrofuran is added, and the mixture is reacted at 45-50°C for 10-12 hours to generate a polyisobutylene-based macromolecular initiator. S4: Under argon atmosphere, polyisobutylene macromolecular initiator and methyl methacrylate were dispersed in anhydrous tetrahydrofuran and reacted at 25-30℃ for 2-3 hours. After maintaining the temperature, lithium acrylate was added and the reaction continued for another 2-3 hours. Then, anhydrous methanol was added to terminate the reaction. The reaction solution was added to ice-cold n-hexane to precipitate the product and vacuum dried to constant weight to obtain the modified polyisobutylene binder; Step 2: A composite solid electrolyte membrane is obtained by adding polytetrafluoroethylene binder to the composite solid electrolyte powder, shearing and mixing, hot extruding to 150~300μm, and rolling to thin to 20~40μm.

2. The method for preparing a composite solid electrolyte membrane according to claim 1, characterized in that: In S4, polyisobutylene macromolecular initiator, methyl methacrylate, and lithium acrylate react in a weight ratio of (50~60):(5~20):(30~35).

3. The method for preparing a composite solid electrolyte membrane according to claim 1, characterized in that: In step 1, the grinding and mixing speed is 1500~2500 rpm, and the grinding and mixing time is 50~70 min.

4. The method for preparing a composite solid electrolyte membrane according to claim 1, characterized in that: In step 1, the sulfide electrolyte particles are Li7P3S. 11 Li3PS4, Li 10 GeP2S 12 Li 10 GeP2S 12 Li 7-x PS 6-x Cl x Any one of them.

5. The method for preparing a composite solid electrolyte membrane according to claim 1, characterized in that: In step 1, the particle size D of the sulfide electrolyte particles 50 The range is 1~10μm.

6. The method for preparing a composite solid electrolyte membrane according to claim 1, characterized in that: In step 2, the rotation speed of the shear mixing is 3000~5000 rpm, and the shear mixing time is 30~60 min.

7. The method for preparing a composite solid electrolyte membrane according to claim 1, characterized in that: In step 2, the hot extrusion temperature is 80~100℃.

8. The method for preparing a composite solid electrolyte membrane according to claim 1, characterized in that: In step 2, the composite solid electrolyte membrane contains, by weight percentage, 0.5-2% modified polyisobutylene binder, 0.05-0.1% polytetrafluoroethylene binder, and the remainder is sulfide electrolyte particles.

9. The composite solid electrolyte membrane prepared by the preparation method according to any one of claims 1 to 8.

Images