CN-121975164-A - Self-supporting sulfide electrolyte membrane and preparation method thereof

Abstract

The invention relates to the technical field of batteries, in particular to a self-supporting sulfide electrolyte membrane and a preparation method thereof. The preparation method comprises the steps of S1, homogenizing a glue solution and sulfide electrolyte to obtain a slurry, S2, coating the slurry on the surface of a substrate, drying and demolding to obtain the self-supporting sulfide electrolyte membrane, wherein the glue solution comprises a nonpolar solvent, a weak polar solvent and a binder, the binder comprises a first polymer and a second polymer, the first polymer has nonpolar property, a molecular chain of the second polymer has a polar structure, and the mass ratio of the first polymer to the second polymer is (0.4-3): 1. The preparation method can realize roll-to-roll continuous production of the self-supporting sulfide electrolyte membrane, can be well separated from a base material, and the prepared self-supporting sulfide electrolyte membrane has excellent ionic conductivity.

Inventors

• YAO YUAN
• ZHANG JINGJING
• LI WANLONG
• LI YUNMING

Assignees

• 蜂巢能源科技股份有限公司

Dates

Publication Date

20260505

Application Date

20260407

Claims (10)

1. 1. The preparation method of the self-supporting sulfide electrolyte membrane is characterized by comprising the following steps: S1, homogenizing glue solution and sulfide electrolyte to obtain slurry; s2, coating the slurry on the surface of a substrate, and then drying and demolding to obtain a self-supporting sulfide electrolyte membrane; Wherein the glue solution comprises a nonpolar solvent, a weak polar solvent and a binder; The binder comprises a first polymer and a second polymer, wherein the first polymer has nonpolar property, the molecular chain of the second polymer has polar structure, and the mass ratio of the first polymer to the second polymer is (0.4-3): 1.
2. 2. The method according to claim 1, wherein, The second polymer has a property of weak polarity; And/or the first polymer comprises a styrenic block copolymer and/or a polyolefin; and/or the second polymer comprises at least one of a hydrogenated nitrile rubber, an acrylate rubber, a polar group grafted styrenic block copolymer, and a polar group grafted polyolefin.
3. 3. The method according to claim 2, wherein, The styrenic block copolymer comprises at least one of styrene-butadiene-styrene, styrene-isoprene-styrene, styrene-ethylene-butylene-styrene, polystyrene-b-poly [ ethylene- (ethylene-propylene) ] -b-polystyrene, and styrene-ethylene-propylene-styrene; and/or the polyolefin comprises at least one of polyethylene, polypropylene, polyisobutylene, and amorphous polyalphaolefin.
4. 4. The method according to claim 2, wherein, The polar groups in the polar group-grafted styrenic block copolymer and the polar group-grafted polyolefin each independently include at least one of a maleic anhydride group, a silane group, an acrylonitrile group, and an acrylate group; And/or the mass grafting rate of the polar groups in the second polymer is 0.1-3%.
5. 5. The method according to claim 1, wherein, The average molecular weight of the first polymer is greater than 200000g/mol; and/or the average molecular weight of the second polymer is 200000g/mol to 1000000g/mol.
6. 6. The method according to claim 1, wherein, The dielectric constant of the nonpolar solvent is less than or equal to 2.5; and/or the weak polar solvent has a dielectric constant of 2-5; And/or the flash point of the nonpolar solvent is more than or equal to 45 ℃; and/or the flash point of the weak polar solvent is more than or equal to 45 ℃; And/or the nonpolar solvent includes at least one of a heavy aromatic hydrocarbon solvent, an alkane solvent, and a mono-olefin solvent; and/or the weak polar solvent comprises an ester solvent and/or an ether solvent.
7. 7. The method according to claim 6, wherein, The heavy aromatic hydrocarbon solvent comprises trimethylbenzene and/or tetramethylbenzene; and/or, the alkane solvent comprises a C10-C15 alkane solvent; and/or, the monoethylenically unsaturated solvent comprises a C10-C15 monoethylenically unsaturated solvent; and/or the ester solvent comprises a C1-C6 fatty alcohol ester of a C4-C10 fatty acid; And/or the ether solvent comprises a C5-C8 aliphatic ether and/or an aromatic ether.
8. 8. The method according to claim 1, wherein, The mass ratio of the nonpolar solvent to the weak polar solvent is (0.4-3) 1; and/or the slurry has a solids content of 40wt% to 70wt%; And/or, the mass content of the binder is 0.1% -5% based on the total mass of the binder and the sulfide electrolyte; And/or the sulfide electrolyte includes at least one of Li 6 PS 5 Cl、Li 10 GeP 2 S 12 、Li 10 SnP 2 S 12 、Li 2 S-P 2 S 5 、Li 2 S-SiS 2 and Li 2 S-B 2 S 3 ; and/or the substrate comprises at least one of an aluminum foil, a PET film and a PP film.
9. 9. The method according to any one of claim 1 to 8, wherein, The preparation method of the glue solution comprises the following steps: (1) Dissolving a first polymer in a nonpolar solvent to obtain a first glue solution; (2) Dissolving a second polymer in a weak polar solvent to obtain a second glue solution; (3) And mixing the first glue solution and the second glue solution to obtain the glue solution.
10. 10. A self-supporting sulfide electrolyte membrane prepared by the method for preparing a self-supporting sulfide electrolyte membrane according to any one of claims 1 to 9.

Description

Self-supporting sulfide electrolyte membrane and preparation method thereof Technical Field The invention relates to the technical field of batteries, in particular to a self-supporting sulfide electrolyte membrane and a preparation method thereof. Background At present, the film forming mode of the solid electrolyte is mainly divided into dry film forming and wet coating. The dry film forming is to introduce binder into solid electrolyte, then to obtain self-supporting electrolyte film through mixing, shearing and repeated rolling, and the film forming is environment friendly, has no solvent introduction, but has high porosity, and the electrolyte film assembled with cell produced through dry process has low yield and short circuit, and the wet coating is to form slurry with certain solid content through introducing binder and solvent into solid electrolyte powder, and to coat the slurry onto the base material to form electrolyte film with electrolyte and base material integrated. However, wet coating has the defects that the mechanical strength of an electrolyte membrane is poor, roll-to-roll film cannot be realized, a transfer process is additionally required to be added, electrolyte is transferred to the surface of a positive electrode or a negative electrode from a substrate, and the production efficiency is low. Disclosure of Invention The invention aims to solve the problems that the mechanical strength of a membrane obtained by the existing wet coating cannot realize roll-to-roll film formation, the transfer printing process is needed, and continuous and large-scale production is seriously hindered, and provides a self-supporting sulfide electrolyte membrane and a preparation method thereof. The preparation method of the self-supporting sulfide electrolyte membrane can realize roll-to-roll continuous production of the self-supporting sulfide electrolyte membrane, can be well separated from a base material, and has excellent ionic conductivity. As described above, the existing solid electrolyte membrane mainly has the inherent defects of two technical routes, namely, on one hand, the membrane obtained by the dry film forming process has high porosity, which leads to easy short circuit and low yield of the battery, and on the other hand, the traditional wet coating process can obtain a uniform and compact membrane layer, but the membrane has poor mechanical strength, cannot be directly rolled up, and needs a transfer printing procedure in the preparation process. According to the invention, the nonpolar solvent and the weak polar solvent are adopted, the nonpolar first polymer and the polar second polymer are matched, the proportion of the nonpolar first polymer and the polar second polymer is controlled, a stable slurry system can be constructed in the homogenate, so that the adhesion between the dried membrane and the substrate can realize a roll-to-roll continuous process, the membrane can be completely peeled from the substrate during final demolding, and the electrochemical performance of the final membrane can be improved by the slurry system. Based on this, the first aspect of the present invention provides a method for producing a self-supporting sulfide electrolyte membrane, the method comprising: S1, homogenizing glue solution and sulfide electrolyte to obtain slurry; s2, coating the slurry on the surface of a substrate, and then drying and demolding to obtain a self-supporting sulfide electrolyte membrane; Wherein the glue solution comprises a nonpolar solvent, a weak polar solvent and a binder; The binder comprises a first polymer and a second polymer, wherein the first polymer has nonpolar property, the molecular chain of the second polymer has polar structure, and the mass ratio of the first polymer to the second polymer is (0.4-3): 1. In some of these embodiments, the second polymer has a weak polar nature. In some embodiments thereof, the first polymer comprises a styrenic block copolymer and/or a polyolefin. In some embodiments thereof, the second polymer comprises at least one of a hydrogenated nitrile rubber, an acrylate rubber, a polar group grafted styrenic block copolymer, and a polar group grafted polyolefin. In some embodiments thereof, the styrenic block copolymer comprises at least one of styrene-butadiene-styrene, styrene-isoprene-styrene, styrene-ethylene-butylene-styrene, polystyrene-b-poly [ ethylene- (ethylene-propylene) ] -b-polystyrene, and styrene-ethylene-propylene-styrene. In some embodiments thereof, the polyolefin comprises at least one of polyethylene, polypropylene, polyisobutylene, and amorphous polyalphaolefin. In some of these embodiments, the polar groups in the polar group-grafted styrenic block copolymer and the polar group-grafted polyolefin each independently include at least one of a maleic anhydride group, a silane group, an acrylonitrile group, and an acrylate group. In some embodiments, the mass grafting of polar groups in the second polymer is from