Solid electrolyte membrane, preparation method thereof and solid-state battery

Abstract

The invention provides a solid-state electrolyte membrane, a preparation method thereof and a solid-state battery. The solid-state electrolyte membrane comprises sulfide electrolyte, a binder, a first additive and a second additive, wherein the first type of additive comprises liquid rubber; the second type of additive comprises a phthalate plasticizer; two additives are added, one additive is liquid rubber, so that structural support is provided in the electrolyte membrane, larger mechanical stress can be borne, crack propagation caused by volume change conduction is reduced, and failure of the electrolyte membrane is avoided; and the other type is a phthalate plasticizer which can be inserted between polymer chains of the liquid rubber and the binder as a small molecule, so that the acting force between molecules is weakened, the flowability of chain segments is improved, and the strength and flexibility of the electrolyte membrane are improved through the synergistic effect of the liquid rubber and the phthalate plasticizer, so that the service life of the electrolyte membrane is prolonged, and the service life of the electrolyte membrane is prolonged. Therefore, the negative electrode with high expansion rate is prevented from cracking.

Description

Technical Field

[0001] The present invention relates to the technical field of solid electrolytes, and in particular to a solid electrolyte membrane and a preparation method thereof, and a solid-state battery. Background Art

[0002] Sulfide solid electrolytes have high ionic conductivity, excellent flexibility and good mechanical processing properties, which are conducive to the preparation of highly densified electrolyte membranes, thereby improving solid-solid interface contact and enhancing the overall performance of the battery.

[0003] In practical applications of sulfide solid-state batteries, the thickness of the sulfide electrolyte membrane is typically controlled below 50 μm to ensure high energy density. Therefore, the ultra-thin sulfide electrolyte membrane needs to be densified, but its strength is still insufficient to accommodate the high expansion rate of the negative electrode. Summary of the Invention

[0004] The embodiments of the present invention provide a solid electrolyte membrane, a preparation method thereof, and a solid-state battery, which can improve the technical problem that the electrolyte membrane has high energy density, thin thickness, and can withstand the volume change stress of a high expansion rate negative electrode.

[0005] In a first aspect, an embodiment of the present invention provides a solid electrolyte membrane, comprising a sulfide electrolyte, a binder, a first type of additive, and a second type of additive; wherein the first type of additive comprises liquid rubber;

[0006] The second type of additives includes phthalate plasticizers.

[0007] In one embodiment, the liquid rubber is a telechelic liquid rubber;

[0008] Preferably, the telechelic liquid rubber has reactive groups, and the reactive groups are located at the end groups of the molecular main chain;

[0009] Preferably, the reactive groups include one or more of hydroxyl, carboxyl, halogen and amino groups.

[0010] In one embodiment, the mass percentage of the first type of additive in the solid electrolyte membrane is 0.01% to 1%;

[0011] Preferably, the mass percentage of the first type of additives in the solid electrolyte membrane is 0.1% to 0.5%.

[0012] In one embodiment, the liquid rubber includes one or more of liquid polybutadiene rubber, liquid polyisoprene rubber, liquid polystyrene-butadiene rubber, silane-modified liquid butadiene rubber, carboxylated liquid isoprene rubber, and liquid farnesene rubber.

[0013] In one embodiment, the mass percentage of the second type of additive in the solid electrolyte membrane is 0.01% to 1%;

[0014] Preferably, the mass percentage of the second type of additive in the solid electrolyte membrane is 0.1% to 0.5%.

[0015] In one embodiment, the phthalate plasticizer includes one or more of tricresyl phosphate, diisononyl phthalate, dioctyl phthalate, tricresyl phosphate, toluene diphenyl phosphate, and dioctyl adipate.

[0016] In one embodiment, the mass percentage of the sulfide electrolyte in the solid electrolyte membrane is 60 wt % to 99 wt %; preferably, the mass percentage of the sulfide electrolyte in the solid electrolyte membrane is 80 wt % to 99 wt %.

[0017] In one embodiment, the particle size of the sulfide electrolyte ranges from 0.5 μm to 20 μm;

[0018] Preferably, the particle size of the sulfide electrolyte ranges from 1 μm to 5 μm.

[0019] In one embodiment, the mass percentage of the binder in the solid electrolyte membrane is 1 wt% to 5 wt%; preferably, the mass percentage of the binder is 1.5 wt% to 2.5 wt%.

[0020] In one embodiment, the relative molecular mass of the binder is 100,000 to 1,000,000; preferably,

[0021] The relative molecular mass of the binder is 300,000 to 500,000.

[0022] In a second aspect, an embodiment of the present invention provides a method for preparing a solid electrolyte membrane, the method comprising the following steps:

[0023] S100, dissolving a binder in a portion of a solvent and stirring to obtain a first mixed solution;

[0024] S200, adding a sulfide electrolyte, remaining solvent, first type additives and second type additives to the first mixed solution, and stirring to obtain a second mixed solution;

[0025] S300 , solidifying the second mixed liquid to obtain the solid electrolyte membrane.

[0026] In one embodiment, in step S100, the stirring speed is 300 rpm to 500 rpm; and / or

[0027] The stirring time is 30 min to 120 min; and / or

[0028] In step S200, the stirring speed is 500 rpm to 2000 rpm; and / or

[0029] The stirring time is 5 min to 20 min.

[0030] In a third aspect, an embodiment of the present invention provides a solid-state battery, comprising the solid-state electrolyte membrane as described above.

[0031] Beneficial effects of the embodiments of the present invention:

[0032] In an embodiment of the present invention, two types of additives are added. One type is liquid rubber, which helps to provide structural support in the electrolyte membrane, can withstand greater mechanical stress, reduce crack propagation caused by volume change conduction, and avoid failure of the electrolyte membrane; the other type is phthalate plasticizers, which are small molecules that can be inserted between the polymer chains of liquid rubber and adhesive, weakening the intermolecular forces, which is beneficial to improving the fluidity of the chain segments. The synergistic effect of liquid rubber and phthalate plasticizers helps to improve the strength and flexibility of the electrolyte membrane, thereby coping with the negative electrode with a high expansion rate to avoid cracks. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0034] Figure 1 It is a flow chart of the preparation method provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention. In addition, it should be understood that the specific implementation methods described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention. In the present invention, unless otherwise specified, the directional words used, such as "upper" and "lower", generally refer to the upper and lower parts of the device in actual use or working state, specifically the drawing direction in the accompanying drawings; while "inside" and "outside" refer to the outline of the device.

[0036] In recent years, with the rapid growth in demand for high-energy-density, high-safety, and long-cycle-life batteries in electric vehicles, portable electronic devices, and renewable energy storage systems, traditional lithium-ion batteries have gradually faced technical bottlenecks. Liquid electrolyte systems pose safety risks such as flammability, leakage, and short circuits caused by lithium dendrite growth. Furthermore, energy density is limited by the theoretical capacity of the positive and negative electrode materials and the stability of the electrolyte. Against this backdrop, solid-state batteries, which use non-flammable solid electrolytes instead of traditional liquid electrolytes, are considered a core direction for next-generation energy storage technology.

[0037] Among them, sulfide solid electrolytes have attracted much attention because of their high ionic conductivity, good flexibility and mechanical processing properties, which are conducive to the preparation of highly densified electrolyte layers, thereby improving solid-solid interface contact and enhancing the overall performance of the battery.

[0038] However, in the practical application of sulfide all-solid-state batteries, to increase their energy density, the sulfide electrolyte membrane thickness needs to be below 50μm. Even after densification, the strength of this ultra-thin sulfide electrolyte membrane remains insufficient. Currently, mainstream manufacturers' sulfide solid-state batteries all use silicon-based anodes. Silicon-based anode materials undergo significant volume expansion during charge and discharge, with expansion rates reaching up to 300%, far exceeding the 10% to 12% of traditional graphite anodes. This significant volume change is transmitted to the sulfide electrolyte layer, causing cracks in the sulfide electrolyte layer. These cracks continue to expand during cycling, seriously affecting the battery's cycling performance and safety.

[0039] In view of this, the embodiments of the present application provide a solid electrolyte membrane, a preparation method thereof, and a solid-state battery, aiming to improve the strength and flexibility of the electrolyte membrane, thereby coping with a negative electrode with a high expansion rate to avoid cracks.

[0040] According to a first aspect of this embodiment, a solid electrolyte membrane is provided, which may include a sulfide electrolyte, a binder, a first type of additive and a second type of additive; wherein the first type of additive includes liquid rubber; and the second type of additive includes a phthalate plasticizer.

[0041] By adopting the above scheme, the solid electrolyte membrane of the embodiment of the present application includes two types of additives. One type is liquid rubber, which helps provide structural support in the electrolyte membrane, can withstand greater mechanical stress, reduce crack propagation caused by volume change conduction, and avoid failure of the electrolyte membrane; the other type is phthalate plasticizer, which is a small molecule that can be inserted between the polymer chains of liquid rubber and adhesive, weakening the intermolecular force and helping to improve the fluidity of the chain segments. The synergistic effect of liquid rubber and phthalate plasticizer helps to improve the strength and flexibility of the electrolyte membrane, thereby coping with the high expansion rate of the negative electrode to avoid cracks. In addition, the addition of the above two types of additives can also ensure that the solid electrolyte membrane has a high ionic conductivity.

[0042] Liquid rubber is a viscous, fluid liquid with a molecular weight between 2,000 and 10,000 at room temperature. It can form a three-dimensional network structure through appropriate chemical reactions. Phthalate plasticizers can increase the material's flexibility and durability, while having minimal impact on its transparency.

[0043] In some embodiments of the present application, the liquid rubber is a telechelic liquid rubber.

[0044] In some embodiments of the present application, the telechelic liquid rubber has reactive groups, and the reactive groups are located at the end groups of the molecular main chain.

[0045] By adopting the above scheme, the telechelic liquid rubber is a liquid polymer with reactive functional groups at both ends of the molecule. Through the chain extension and cross-linking reaction of the reactive functional groups, a closed cross-linked network without molecular ends can be obtained, which helps to improve the strength of the solid electrolyte membrane.

[0046] Specifically, the reactive groups are located at the end groups of the main chain of the molecule, indicating that there are fewer branches in the molecular structure and a higher content of end group branches. The end group branches can participate in free radical cross-linking reactions to form a dynamic cross-linking network, which helps to improve the elastic modulus and creep resistance of the solid electrolyte membrane.

[0047] In some embodiments of the present application, the reactive group may include one or more of a hydroxyl group, a carboxyl group, a halogen group, and an amino group.

[0048] In some embodiments of the present application, the halo group is a bromo group.

[0049] By adopting the above scheme, since the telechelic liquid rubber has fluidity at room temperature, the hydroxyl, carboxyl, halogen and amino groups as reactive groups can have little effect on the processing viscosity of the reaction system, and can exhibit Newtonian fluid behavior during the shear process, which helps to make the reaction system more processable.

[0050] In some embodiments of the present application, the mass percentage of the first type of additive in the solid electrolyte membrane is 0.01% to 1%. Furthermore, the mass percentage of the first type of additive in the solid electrolyte membrane is 0.1% to 0.5%. For example, the mass percentage of the first type of additive in the solid electrolyte membrane is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or any value between two adjacent values.

[0051] By adopting the above solution and adding an appropriate amount of the first type additive, the strength of the electrolyte membrane can be improved. However, if the amount of the first type additive is too large, the solid electrolyte membrane will become hard and brittle. If the amount of the first type additive is too small, the strength of the solid electrolyte membrane will not be enhanced.

[0052] In some embodiments of the present application, the liquid rubber may include one or more of liquid polybutadiene rubber, liquid polyisoprene rubber, liquid polystyrene-butadiene rubber, silane-modified liquid butadiene rubber, carboxylated liquid isoprene rubber, and liquid farnesene rubber.

[0053] It should be noted that the above liquid rubbers have the following common properties: polymers with fluidity and viscosity at room temperature, when subjected to external forces, not only exhibit viscosity but also elasticity and plasticity.

[0054] It can be understood that the molecular chain of liquid polybutadiene rubber has a high 1,4-structure content, high cross-linking efficiency, and good network density, which significantly improves the tensile strength and crack resistance of the membrane, making it suitable for negative electrodes with high expansion rates.

[0055] Silane-modified liquid butadiene rubber is obtained by modifying liquid butadiene rubber with silane. The molecular chain contains Si-O bonds, which can improve the interfacial compatibility with sulfide electrolytes, reduce interfacial defects, and enhance the overall density of the solid electrolyte membrane.

[0056] Carboxylated liquid polyisoprene rubber, the polarity of the carboxyl group makes the rubber more compatible with polar binders. At the same time, it can enhance the interfacial bonding force with sulfide electrolytes through hydrogen bonding, which is beneficial to improving the stability of the slurry and the uniformity of film formation.

[0057] The unsaturated double bond structure of liquid farnesene rubber provides unique flexibility and low-temperature performance. Even at low temperatures, it maintains the mobility of the molecular segments, preventing hardening and brittleness of the electrolyte membrane and improving the battery's cycling stability in low-temperature environments.

[0058] In some embodiments of the present application, the mass percentage of the second type of additive in the solid electrolyte membrane is 0.01% to 1%. The mass percentage of the second type of additive in the solid electrolyte membrane is 0.1% to 0.5%. For example, the mass percentage of the second type of additive in the solid electrolyte membrane is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, and any value between two adjacent values.

[0059] By adopting this approach, an appropriate amount of the second type of additive can be inserted between the molecular chains of the first type of additive and the binder, weakening the van der Waals forces without affecting the overall cross-linked network, thereby helping to improve the flexibility of the electrolyte membrane. However, the content of the second type of additive should not be too high, as it will cause the electrolyte membrane to soften excessively.

[0060] In some embodiments of the present application, the phthalate plasticizer may include one or more of tricresyl phosphate, diisononyl phthalate, dioctyl phthalate, tricresyl phosphate, diphenyl methyl phosphate, and dioctyl adipate.

[0061] By adopting the above scheme, the above-mentioned phthalate plasticizers are all low-molecular-weight organic compounds, which can be inserted between the molecular chains of the first type of additives and binders, helping to weaken the intermolecular van der Waals forces, thereby making the chain segments easier to slide, thereby compensating for the defect of increased brittleness of the electrolyte membrane due to the addition of the first type of additives.

[0062] It should be noted that the isononyl side chains in diisononyl phthalate (DIP) increase steric hindrance, forming stronger intermolecular entanglements with the 1,4-structure in the liquid rubber, which helps improve the tensile strength and crack resistance of the electrolyte membrane. Furthermore, DIP has a low polarity and minimal interference with the ionic conduction of the sulfide electrolyte. At an addition level of 0.1% to 0.5%, ionic conductivity is barely affected.

[0063] Both tricresyl phosphate and tricresyl phosphate contain phosphorus-oxygen polar groups, which have better compatibility with polar binders. They can enhance the interfacial bonding strength between the sulfide electrolyte membrane and the binder through hydrogen bonding, which is beneficial to reduce the conductive path defects caused by particle agglomeration, thereby improving the ion conduction uniformity of the electrolyte membrane.

[0064] The molecular chain of dioctyl adipate is more flexible and has a lower glass transition temperature. It can maintain excellent flexibility in low-temperature environments, thereby improving the cycle stability of the battery in low-temperature environments.

[0065] According to different usage requirements, different second-category additives can be selected to meet the above requirements.

[0066] In some embodiments of the present application, the mass percentage of the sulfide electrolyte in the solid electrolyte membrane is 60% to 99%. Further, the mass percentage of the sulfide electrolyte in the solid electrolyte membrane is 80% to 99%. Exemplarily, the mass percentage of the sulfide electrolyte in the solid electrolyte membrane is 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, and any value between two adjacent values.

[0067] By adopting the above solution, the sulfide electrolyte is the main ion conductor. The high proportion of sulfide electrolyte in the solid electrolyte membrane helps to ensure that it forms a continuous and dense three-dimensional ion conductive network within the membrane, reducing the obstruction of ion migration by inactive ingredients such as binders and additives. At the same time, the high content of sulfide electrolyte helps to reduce the porosity of the densified electrolyte membrane, thereby increasing the contact area between the electrolyte membrane and the positive and negative electrode materials by 20% to 30%, reducing interfacial resistance and improving the battery's charge and discharge efficiency.

[0068] Furthermore, sulfide electrolytes are inherently brittle. While the sulfide electrolyte content in the examples of this application is relatively high, the addition of the first and second additives helps balance the strength and flexibility of the electrolyte membrane, enabling it to withstand the stress changes caused by the high expansion rate of the negative electrode. Furthermore, the high sulfide electrolyte content also helps increase the density of active materials within the electrolyte membrane, thereby improving the overall energy density of the battery.

[0069] In some embodiments of the present application, the sulfide electrolyte may include Li2S-SiS2, Li2S-P2S5-LiI, Li2S-SiS2-LiI, Li4SnS4-LiI, 90(0.8Li2S-0.2P2S5)·5LiI, 80Li2S-20P2S5, Li3PS4, Li7P3S 11 , 9Li2S·3P2S5·Ni3S2, Li6PS5Cl, Li6PS5Br, Li6PS5I, Li5.5PS 4.5 Cl 1.5 、Li 5.7 PS 4.7 Cl 1.3 、Li 10 GeP2S 12 、Li 3.25 Ge 0.25 P 0.75 S4, Li 6.6 Ge 0.6 P 0.4S5I. Further preferably, the sulfide electrolyte may include Li6PS5Cl, Li6PS5Br, Li6PS5I, Li 5.5 PS 4.5 Cl 1.5 、Li 5.7 PS 4.7 Cl 1.3 One or more of; Further preferably, the sulfide electrolyte can be Li 5.5 PS 4.5 Cl 1.5 .

[0070] In some embodiments of the present application, the particle size of the sulfide electrolyte may range from 0.5 μm to 20 μm. Further, the particle size of the sulfide electrolyte may range from 1 μm to 5 μm. For example, the particle size of the sulfide electrolyte may range from 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, and any value between two adjacent values.

[0071] By adopting the above scheme, the particle size range of the sulfide electrolyte is moderate. Under the action of the first type of additives, the second type of additives and the binder, a densely packed structure can be formed, and the ion conduction path is continuous without obvious grain boundary barriers. In addition, after densification, the sulfide electrolyte particles of suitable particle size have a grain boundary thickness of less than 10nm, and the barrier for lithium ions to cross the grain boundary is reduced. In particular, the ionic conductivity remains above 20% in low temperature environments. If the particle size of the sulfide electrolyte is too large, it may cause the sulfide electrolyte particles themselves to be brittle, and the negative electrode with a high expansion rate may be easily "cracked" when expanding, forming an initial crack source.

[0072] In some embodiments of the present application, the mass percentage of the binder in the solid electrolyte membrane is 1 wt% to 5 wt%. Further, the mass percentage of the binder in the solid electrolyte membrane is 1.5 wt% to 2.5 wt%. Exemplarily, the mass percentage of the binder in the solid electrolyte membrane is 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2.0 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, and any value between two adjacent values.

[0073] By adopting the above scheme, a suitable content of binder can improve the flexibility and tensile strength of the sulfide electrolyte. However, if the content of the binder is too high, the ionic conductivity of the sulfide electrolyte will be reduced.

[0074] In some embodiments of the present application, the relative molecular mass of the binder is 100,000 to 1,000,000. Further, the relative molecular mass of the binder is 300,000 to 500,000. Exemplarily, the relative molecular mass of the binder is 300,000, 320,000, 350,000, 380,000, 400,000, 420,000, 450,000, 470,000, 500,000, and any value between two adjacent values.

[0075] By adopting the above scheme, the relative molecular weight is within the appropriate range, indicating that the binder's molecular chain length is moderate, which helps to form moderate entanglements between chains. This can not only fix the sulfide electrolyte particles through physical cross-linking, but also retain a certain degree of chain segment mobility, which helps to achieve a balance between strength and toughness. If the molecular weight of the binder is too small, the molecular chains may be too short, the interchain entanglement force is weak, and the resulting bonding network is loose, resulting in insufficient tensile strength of the electrolyte membrane and difficulty in withstanding the expansion stress of the high expansion rate negative electrode. If the molecular weight of the binder is too large, the molecular chains will be too long, the interchain entanglement will be excessive, and the rigid network will be formed, which will reduce flexibility. At the same time, high entanglement will also make it difficult for plasticizers to insert between molecular chains, weakening the plasticizing effect.

[0076] In some embodiments of the present application, the binder may include at least one of styrene-butylene-styrene copolymer (SEBS), ethylene butadiene rubber (SBR), butadiene rubber (BR), polyisobutylene (PIB), nitrile rubber (NBR), polytetrafluoroethylene (PTFE), polyvinyl acetate (PVA), polyvinyl butyral (PVB), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), polyacrylonitrile (PAN), styrene-butadiene-styrene block copolymer (SBS), and styrene-ethylene / propylene-styrene block copolymer (SEPS).

[0077] According to a second aspect of the embodiment of the present application, a preparation method is provided, referring to Figure 1 , the preparation method may comprise the following steps:

[0078] S100, dissolving a binder in a portion of a solvent and stirring to obtain a first mixed solution;

[0079] S200, adding a sulfide electrolyte, remaining solvent, first type additives and second type additives to the first mixed solution, and stirring to obtain a second mixed solution;

[0080] S300 , solidifying the second mixed liquid to obtain a solid electrolyte membrane.

[0081] By adopting the above scheme, the binder is first dissolved in part of the solvent, which helps to allow the two to be initially cross-linked through chain segment entanglement + reactive groups to obtain a first mixed liquid. Then, the sulfide electrolyte, the remaining solvent, the first type of additives and the second type of additives are added to the first mixed liquid, which helps to avoid uneven dispersion of particles due to the addition of the sulfide electrolyte. The second mixed liquid is then solidified to obtain a solid electrolyte membrane. The above preparation method is simple and efficient.

[0082] In some embodiments of the present application, in step S100, the stirring speed is 300 rpm to 500 rpm. Further, in step S100, the stirring speed is 350 rpm to 450 rpm. Exemplarily, the stirring speed is 350 rpm, 360 rpm, 370 rpm, 380 rpm, 390 rpm, 400 rpm, 410 rpm, 420 rpm, 430 rpm, 440 rpm, 450 rpm, and any value between two adjacent values.

[0083] By adopting the above scheme, the purpose of step S100 is to dissolve the binder in a portion of the solvent. Selecting a moderate rotation speed of 300 rpm to 500 rpm helps ensure that the binder is fully dissolved while preventing decomposition of the first type of additive, thereby forming a uniform first mixed liquid. If the rotation speed is too low, insufficient dissolution may occur; if the rotation speed is too high, bubbles may be introduced or molecular chains may break.

[0084] In some embodiments of the present application, in step S100, the stirring time is 30 min to 120 min. Further, the stirring time is 50 min to 100 min. Exemplarily, the stirring time is 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, and any value between two adjacent values.

[0085] In some embodiments of the present application, in step S200, the stirring speed is 500 rpm to 2000 rpm. Further, the stirring speed is 800 rpm to 1500 rpm. Exemplarily, the stirring speed is 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, 1500 rpm, and any value between two adjacent values.

[0086] By adopting the above scheme, a large amount of sulfide electrolyte is added in step S200, and a relatively high speed of stirring is required to disperse the sulfide electrolyte. A relatively high speed helps to break up the agglomeration of the electrolyte particles and promote coating, but an excessively high speed may cause particle breakage or excessive evaporation of the solvent. It is necessary to balance the dispersion effect and particle integrity.

[0087] In some embodiments of the present application, the stirring time is 5 min to 20 min. Further, the stirring time is 8 min to 15 min. Exemplarily, the stirring time is 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, and any value between two adjacent values.

[0088] In some embodiments of the present application, the solvent can be selected from one or more of anisole, isobutyl isobutyrate, toluene, xylene, methyl acetate, ethyl acetate, hexane, and n-heptane. Preferably, the solvent can be a mixture of anisole and xylene.

[0089] In some embodiments of the present application, in step S300, the second mixed solution is coated on PET by blade coating, and then vacuum dried to obtain an electrolyte membrane.

[0090] In some embodiments of the present application, the drying temperature is 90° C. to 120° C., and the drying time is 30 min to 60 min.

[0091] According to a third aspect of an embodiment of the present application, a solid-state battery is provided, comprising the solid-state electrolyte membrane as described above.

[0092] By adopting the above scheme, since the solid electrolyte membrane has excellent strength and flexibility, it can cope with the negative electrode with a high expansion rate to avoid cracks. The solid-state battery includes the aforementioned solid electrolyte membrane, so that the prepared solid-state battery maintains good strength and brittleness resistance, thereby improving the battery's cycle performance and safety performance.

[0093] In some embodiments of the present application, a solid-state battery may be composed of a positive electrode current collector, a positive electrode plate, the aforementioned solid electrolyte membrane, a negative electrode plate, and a negative electrode current collector.

[0094] Wherein, the positive electrode current collector can be selected from aluminum foil, carbon foil or stainless steel foil;

[0095] The positive electrode plate can be made of a positive electrode active material and a positive electrode conductive agent. The positive electrode active material can be selected from LiCoO2, LiFePO4 or a nickel-cobalt-manganese ternary positive electrode material according to actual conditions.

[0096] The positive electrode conductive agent can be selected from one or more of acetylene black, graphite, Super P or conductive fiber according to actual conditions.

[0097] The negative electrode current collector can be made of copper foil, carbon foil or stainless steel.

[0098] The negative electrode plate can be made of either graphite or silicon.

[0099] The present invention is described in detail below by means of specific examples, which are only some examples of the present invention and are not intended to limit the present invention. The raw materials used in the following examples, unless otherwise specified, are all commercially available products.

[0100] Example 1

[0101] A solid electrolyte membrane is prepared by the following steps:

[0102] S100, dissolving 2 g of styrene-butadiene-styrene block copolymer in 38 g of anisole solution, adding a magnetic stirring rotor, placing on a magnetic stirrer, and stirring at 25° C. for 2 h to obtain a first mixed solution with a concentration of 5%; the relative molecular mass of the styrene-butadiene-styrene block copolymer is 4000;

[0103] S200, taking 5 g of the first mixed solution and placing it in a stirring tank, adding 16.33 g (98%) of sulfide electrolyte, 5 g of anisole, 0.082 g (0.49%) of the first type additive and 0.012 g (0.1%) of the second type additive thereto, and stirring at 2000 rpm / min for 5 min to obtain a second mixed solution; the sulfide electrolyte adopts Li5.5PS4.5Cl1.5 with a particle size of 1.2 μm;

[0104] S300, coating the second mixed solution on a stainless steel substrate with a 150 μm scraper, and then vacuum drying at 120° C. for 24 h to obtain a solid electrolyte membrane;

[0105] Among them, the first type of additive uses liquid butadiene rubber LBR-300;

[0106] The second type of additive uses diisononyl phthalate.

[0107] Example 2

[0108] A solid electrolyte membrane is different from Example 1 in that the type of liquid rubber is different. In this example, the liquid rubber is carboxylated liquid isoprene rubber LIR-30.

[0109] Example 3

[0110] A solid electrolyte membrane is different from Example 1 in that the type of phthalate plasticizer is different. In this example, the phthalate plasticizer is dioctyl phthalate.

[0111] Example 4

[0112] A solid electrolyte membrane is different from Example 1 in that the mass percentage of the binder is different. In this example, the mass percentage of the styrene-butadiene-styrene block copolymer is 1%.

[0113] Example 5

[0114] A solid electrolyte membrane differs from Example 1 in that the mass percentage of the binder is different. In this example, the mass percentage of the styrene-butadiene-styrene block copolymer is 2.5%.

[0115] Example 6

[0116] A solid electrolyte membrane differs from Example 1 in that the mass percentages of some ingredients in the formula are different. In this example, the mass percentage of styrene-butadiene-styrene block copolymer is 5%, and the mass percentage of sulfide electrolyte is 94.5%.

[0117] Example 7

[0118] A solid electrolyte membrane differs from Example 1 in that the mass percentages of some ingredients in the formula are different. In this example, the mass percentage of styrene-butadiene-styrene block copolymer is 1.5%, the mass percentage of sulfide electrolyte is 98%, and the mass ratio of the first type of additive to the second type of additive is 4.9:1; wherein the first type of additive is liquid butadiene;

[0119] The second type of additive uses diisononyl phthalate.

[0120] Example 8

[0121] A solid electrolyte membrane is different from Example 1 in that the mass ratio of the first type of additive to the second type of additive is 1:1, the mass of the first type of additive is 0.0416 g, and the mass of the second type of additive is 0.0416 g.

[0122] Example 9

[0123] A solid electrolyte membrane is different from Example 1 in that the mass ratio of the first type of additive to the second type of additive is 1.5:1, the mass of the first type of additive is 0.05 g, and the mass of the second type of additive is 0.0333 g.

[0124] Example 10

[0125] A solid electrolyte membrane is different from Example 1 in that the mass ratio of the first type of additive to the second type of additive is 6:1, the mass of the first type of additive is 0.0714 g, and the mass of the second type of additive is 0.0119 g.

[0126] Example 11

[0127] A solid electrolyte membrane is different from Example 1 in that the mass ratio of the first type of additive to the second type of additive is 8:1, the mass of the first type of additive is 0.0740 g, and the mass of the second type of additive is 0.0093 g.

[0128] Comparative Example 1

[0129] A solid electrolyte membrane is prepared by the following steps:

[0130] S100, dissolving 2 g of styrene-butadiene-styrene block copolymer in 38 g of anisole solution, adding a magnetic stirring rotor, placing on a magnetic stirrer, and stirring at 25° C. for 2 h to obtain a first mixed solution with a concentration of 5%;

[0131] S200, taking 5 g of the first mixed solution and placing it in a stirring tank, adding 12.25 g of sulfide electrolyte and 5 g of anisole thereto, and stirring at 2000 rpm / min for 5 min to obtain a second mixed solution;

[0132] S300, coating the second mixed solution on a stainless steel substrate with a 150 μm scraper, and then vacuum drying at 120° C. for 24 h to obtain a solid electrolyte membrane.

[0133] Comparative Example 2

[0134] A solid electrolyte membrane is prepared by the following steps:

[0135] S100, dissolving 2 g of styrene-butadiene-styrene block copolymer in 38 g of anisole solution, adding a magnetic stirring rotor, placing on a magnetic stirrer, and stirring at 25° C. for 2 h to obtain a first mixed solution with a concentration of 5%;

[0136] S200, taking 5 g of the first mixed solution and placing it in a stirring tank, adding 11.125 g of sulfide electrolyte, 5 g of anisole and 0.125 g of the second type additive thereto, and stirring at 2000 rpm / min for 5 min to obtain a second mixed solution;

[0137] S300, coating the second mixed solution on a stainless steel substrate with a 150 μm scraper, and then vacuum drying at 120° C. for 24 h to obtain a solid electrolyte membrane;

[0138] Among them, the second type of additive uses diisononyl phthalate.

[0139] Performance testing:

[0140] (1) Strength: Cut the electrolyte membrane into standard-sized rectangular specimens and clamp the specimens in the upper and lower clamps of a universal material testing machine. Apply tension to the specimen at a constant rate until the specimen breaks. Record the force-displacement curve during the stretching process and calculate the tensile strength.

[0141] (2) Flexibility: Wrap the film sample around a shaft with a diameter of 5 mm to 10 mm and observe whether cracks or breakage occur.

[0142] (3) Ionic conductivity: The electrolyte membrane was cut into small discs with a diameter of 1 cm, placed in a mold, and pressurized to 5T. The electrolyte membrane will separate from the substrate to form a self-supporting membrane. The electrolyte sheet without the substrate was then placed in the mold and pressurized to 5T. The screws were tightened and an AC impedance test was performed using an electrochemical workstation at 0.1Hz~1MHZ and a voltage disturbance of 5mV. After the test, the electrolyte sheet was removed from the mold and its thickness was measured using a micrometer. The ionic conductivity was obtained according to the formula σ=L / (R*S), where L is the thickness of the electrolyte sheet, R is the resistance (obtained from the electrochemical workstation test), and S is the area of ​​the electrolyte sheet.

[0143] The test results are shown in Table 1:

[0144] Table 1

[0145]

[0146] Comparing Example 1 with Comparative Examples 1-2, Example 1 employs the synergistic effect of liquid butadiene rubber and diisononyl phthalate. As shown in Table 1, the resulting solid electrolyte membrane exhibits high strength, good flexibility, and high ionic conductivity. This is because the liquid rubber provides structural support, allowing it to withstand greater mechanical stress, while the diisononyl phthalate can intercalate between the molecular chains of the liquid rubber and the binder, improving the fluidity of the chain segments. This synergistic effect helps improve the strength and flexibility of the electrolyte membrane while also ensuring high ionic conductivity.

[0147] Compared with Example 1, Example 2-3 changes the type of liquid rubber, and Example 3 changes the type of phthalate plasticizer. Combined with Table 1, it can be seen that the strength of the electrolyte membranes of Examples 2-3 is maintained at a high level; moreover, the electrolyte membranes of Examples 1-3 can be wound on a shaft with a smaller diameter and bent without breaking, and have good flexibility; and can ensure that the electrolyte membrane has a high ionic conductivity.

[0148] Compared with Examples 1 and 4-6, Examples 4-6 change the mass percentage of the binder. Combined with the test results in Table 1, it can be seen that if the binder content is too low, the strength of the electrolyte membrane will be low, and a self-supporting membrane cannot be formed. During winding, cracks are prone to appear on the surface of the electrolyte membrane, and the membrane cannot be wound. If the binder content is too high, although the electrolyte membrane can be guaranteed to have a higher strength, its ionic conductivity is greatly lost, and the battery cell performance is poor.

[0149] Comparing Example 1 with Examples 7-11, Examples 7-11 vary the mass ratio of the first type of additive to the second type of additive, with the mass ratio between the two being 2:1 to 8:1, preferably 4.9:1. If the mass ratio of the first type of additive to the second type of additive is less than 2:1, the higher the content of the second type of additive, the more likely the second type of additive is to float to the surface, affecting the ionic conductivity and strength of the electrolyte membrane. If the mass ratio of the first type of additive to the second type of additive is greater than 8:1, the higher the content of the first type of additive, the less the amount of the second type of additive added to ensure that the molecular chain is fully filled with small molecules, affecting the ionic conductivity and strength of the electrolyte membrane.

[0150] The embodiments of the present invention are described in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas. At the same time, for those skilled in the art, according to the ideas of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A solid electrolyte membrane, characterized in that The solid electrolyte membrane includes a sulfide electrolyte, a binder, a first type of additive and a second type of additive; wherein the first type of additive includes liquid rubber; The second type of additives includes phthalate plasticizers.

2. The solid electrolyte membrane according to claim 1, characterized in that The liquid rubber is a telepawl type liquid rubber; Preferably, the telechelic liquid rubber has reactive groups, and the reactive groups are located at the end groups of the molecular main chain; Preferably, the reactive groups include one or more of hydroxyl, carboxyl, halogen and amino groups.

3. The solid electrolyte membrane according to claim 1 or 2, characterized in that The mass percentage of the first type of additive in the solid electrolyte membrane is 0.01% to 1%; Preferably, the mass percentage of the first type of additives in the solid electrolyte membrane is 0.1% to 0.5%.

4. The solid electrolyte membrane according to claim 3, characterized in that The liquid rubber includes one or more of liquid polybutadiene rubber, liquid polyisoprene rubber, liquid polystyrene-butadiene rubber, silane-modified liquid butadiene rubber, carboxylated liquid isoprene rubber, and liquid farnesene rubber.

5. The solid electrolyte membrane according to claim 1 or 2, characterized in that The mass percentage of the second type of additive in the solid electrolyte membrane is 0.01% to 1%; Preferably, the mass percentage of the second type of additive in the solid electrolyte membrane is 0.1% to 0.5%.

6. The solid electrolyte membrane according to claim 5, characterized in that The phthalate plasticizer includes one or more of tricresyl phosphate, diisononyl phthalate, dioctyl phthalate, tricresyl phosphate, diphenyl methyl phosphate, and dioctyl adipate.

7. The solid electrolyte membrane according to claim 1 or 2, characterized in that The mass percentage of the sulfide electrolyte in the solid electrolyte membrane is 60 wt% to 99 wt%; preferably, the mass percentage of the sulfide electrolyte in the solid electrolyte membrane is 80 wt% to 99 wt%.

8. The solid electrolyte membrane according to claim 7, characterized in that The particle size of the sulfide electrolyte ranges from 0.5 μm to 20 μm; Preferably, the particle size of the sulfide electrolyte ranges from 1 μm to 5 μm.

9. The solid electrolyte membrane according to claim 1, characterized in that The mass percentage of the binder in the solid electrolyte membrane is 1 wt% to 5 wt%; preferably, the mass percentage of the binder is 1.5 wt% to 2.5 wt%.

10. The solid electrolyte membrane according to claim 9, characterized in that The relative molecular mass of the binder is 100,000 to 1,000,000; preferably, The relative molecular mass of the binder is 300,000 to 500,000.

11. The method for preparing a solid electrolyte membrane according to any one of claims 1 to 10, characterized in that: The preparation method comprises the following steps: S100, dissolving a binder in a portion of a solvent and stirring to obtain a first mixed solution; S200, adding a sulfide electrolyte, remaining solvent, first type additives and second type additives to the first mixed solution, and stirring to obtain a second mixed solution; S300 , solidifying the second mixed liquid to obtain the solid electrolyte membrane.

12. The method for preparing a solid electrolyte membrane according to claim 11, wherein: In the step S100, the stirring speed is 300 rpm to 500 rpm; and / or The stirring time is 30 min to 120 min; and / or In step S200, the stirring speed is 500 rpm to 2000 rpm; and / or The stirring time is 5 min to 20 min.

13. A solid-state battery, characterized in that: The solid-state battery comprises the solid electrolyte membrane according to any one of claims 1 to 10.

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