Solid electrolyte membrane and all-solid-state battery including the same

Abstract

The present invention relates to a solid electrolyte membrane for an all-solid-state battery, comprising a solid electrolyte in a particle form and an additive having a linear structure, and also relates to an all-solid-state battery comprising the solid electrolyte membrane.

Description

Technical Field

[0001] This application claims priority based on Korean Patent Application No. 10-2021-0114511, filed on August 30, 2021, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a solid electrolyte membrane and an all-solid-state battery comprising the solid electrolyte membrane. Background Art

[0003] A secondary battery is a device that converts external electrical energy into chemical energy, stores it, and generates electricity when needed. It is also called a rechargeable battery, meaning it can be recharged multiple times. Commonly used secondary batteries include lead-acid batteries, nickel-cadmium batteries (NiCd), nickel-metal hydride batteries (NiMH), and lithium secondary batteries. Compared to primary batteries, which are discarded after a single use, secondary batteries offer economic and environmental advantages.

[0004] At the same time, with the gradual development of wireless communication technology, portable devices and automotive accessories need to be lightweight, thin, and miniaturized, and therefore the demand for secondary batteries used as energy sources for these devices is increasing. In particular, as hybrid electric vehicles and electric vehicles are put into practical use to prevent environmental pollution, when using secondary batteries in batteries for these next-generation vehicles, research efforts are devoted to reducing the manufacturing cost and weight of the batteries and extending their lifespan. Among various secondary batteries, lithium secondary batteries, which are lightweight, exhibit high energy density and operating potential, and have a long cycle life, have recently become the focus of attention.

[0005] Generally, a lithium secondary battery is manufactured by mounting an electrode assembly consisting of a negative electrode, a positive electrode, and a separator within a cylindrical or prismatic metal can or an aluminum laminate pouch-type case, and injecting an electrolyte into the electrode assembly.

[0006] However, lithium secondary batteries require a housing with a certain space, such as a cylindrical, square, or pouch-shaped housing, which limits the development of various portable devices. Therefore, a new type of lithium secondary battery that is easily deformable is needed. In particular, the electrolyte contained in lithium secondary batteries needs to have excellent ionic conductivity and no risk of leakage.

[0007] As the electrolyte of conventional lithium secondary batteries, liquid electrolytes in which lithium salts are dissolved in non-aqueous organic solvents are mainly used. However, in the case of such liquid electrolytes, there is a high possibility of degradation of the electrode material and volatilization of the organic solvent. There is also a risk of combustion or explosion due to the increase in ambient temperature and the temperature of the battery itself, and there is also a risk of leakage, making it difficult to implement various types of lithium secondary batteries with high safety.

[0008] Meanwhile, all-solid-state batteries using solid electrolytes have an advantage in that an electrode assembly can be manufactured in a safe and simple form because organic solvents are excluded.

[0009] However, a limitation of all-solid-state batteries is that their actual energy density and output do not reach the level of lithium secondary batteries using conventional liquid electrolytes. In the case of all-solid-state batteries, since the electrolyte membrane containing the solid electrolyte is located between the positive and negative electrodes, it is bulky and heavy compared to conventional lithium secondary batteries, resulting in lower energy density per unit volume and energy density per unit weight. To prevent these problems, if the electrolyte membrane is made thin, a short circuit may occur between the positive and negative electrodes.

[0010] Therefore, it is necessary to develop an electrolyte membrane that has excellent ionic conductivity while maintaining a stable state between electrodes due to its superior mechanical strength.

[0011] [Prior art literature]

[0012] [Patent Document]

[0013] Korean Patent Publication No. 10-2016-0115912

[0014] Korean Patent Registration 10-1512170 Summary of the Invention

[0015] [Technical Issues]

[0016] Therefore, the inventors of the present invention conducted research from various angles to solve the above-mentioned problems. As a result, it was confirmed that when an additive having a linear structure is included in a solid electrolyte membrane, the ion conductivity and strength of a solid electrolyte membrane in the form of a thin film can be improved, thereby completing the present invention.

[0017] Therefore, an object of the present invention is to provide a solid electrolyte membrane for an all-solid-state battery having excellent ionic conductivity and strength.

[0018] In addition, another object of the present invention is to provide an all-solid-state battery including the solid electrolyte membrane.

[0019] [Technical solution]

[0020] In order to achieve the above object, the present invention provides a solid electrolyte membrane for an all-solid-state battery, which comprises a solid electrolyte in a particle form and an additive having a linear structure.

[0021] Furthermore, the present invention provides an all-solid-state battery comprising a positive electrode, a negative electrode, and a solid electrolyte membrane disposed therebetween, wherein the solid electrolyte membrane is the solid electrolyte membrane of the present invention.

[0022] [Beneficial effects]

[0023] Since the solid electrolyte membrane for an all-solid-state battery of the present invention contains an additive having a linear structure, it has excellent mechanical strength even at a thin thickness of 50 μm or less, and has the effect of improving energy density and ion conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a diagram showing the solid electrolyte membrane for an all-solid-state battery of the present invention.

[0025] Figure 2 This is a diagram showing a solid electrolyte membrane for an all-solid-state battery containing the binder of Comparative Example 2.

[0026] Figure 3 This is a diagram showing a solid electrolyte membrane for an all-solid-state battery including the separator of Comparative Example 4.

[0027] Figure 4 This is a photograph of the solid electrolyte membrane of Example 1.

[0028] Figure 5 This is a SEM photograph of the surface of the solid electrolyte membrane of Example 1.

[0029] Figure 6 This is a photograph of the solid electrolyte membrane of Comparative Example 1.

[0030] Figure 7 This is a photograph of the surface of the solid electrolyte membrane of Comparative Example 1.

[0031] Figure 8 This is a SEM photograph of the surface of the solid electrolyte membrane of Comparative Example 1.

[0032] Figure 9 This is a photograph of the solid electrolyte membrane of Comparative Example 2.

[0033] Figure 10 This is a photograph of the solid electrolyte membrane of Comparative Example 3.

[0034] Figure 11 This is a photograph of the surface of the solid electrolyte membrane of Comparative Example 4.

[0035] Figure 12 This is a SEM photograph of the surface of the solid electrolyte membrane of Comparative Example 4. DETAILED DESCRIPTION

[0036] Hereinafter, the present invention will be described in more detail.

[0037] The terms and words used in this specification and claims should not be construed as limited to common or dictionary terms, but should be construed as meanings and concepts consistent with the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concepts of the terms in order to describe his invention in the best possible manner.

[0038] The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The singular forms "a", "an" and "the" include plural referents unless the context clearly indicates otherwise. It should be understood that the terms used in this specification, such as "including" or "having", are intended to indicate the presence of the features, numbers, steps, operations, components, parts or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0039] Lithium secondary batteries have long been used in small applications such as mobile phones and laptops, but their application has recently expanded to medium and large-scale applications such as electric vehicles and energy storage devices. Unlike small-scale applications, these applications require superior performance and stability due to the harsh operating environment and the need to use more cells.

[0040] In the case of most commercially available lithium secondary batteries, a liquid electrolyte in which lithium salt is dissolved in an organic solvent is used, and the organic solvent contained in the liquid electrolyte is easily volatile and flammable, so there is a potential risk of fire and explosion, and there is a risk of leakage, so long-term reliability is insufficient.

[0041] Therefore, all-solid-state batteries (ALLS) are being developed, replacing the liquid electrolytes of lithium secondary batteries with solid electrolytes. Because ALLS batteries do not contain volatile organic solvents, they pose no risk of explosion or fire and are attracting attention as a way to produce high-output batteries with excellent economic feasibility and productivity.

[0042] For all-solid-state batteries, solid electrolytes require high ionic conductivity and processable mechanical strength. However, to ensure mechanical strength, the thickness of the solid electrolyte membrane in film form must inevitably be increased, resulting in a problem of reduced energy density. Therefore, in order to make the solid electrolyte membrane thinner while ensuring mechanical strength, a solid electrolyte membrane with a film thickness of 50 μm or less, large pores, and high porosity is required. However, porosity has a trade-off relationship with strength and thickness, making it difficult to manufacture films with high porosity.

[0043] Therefore, in the present invention, an additive having a linear structure is incorporated into a solid electrolyte membrane of an all-solid-state battery, thereby aiming to provide a thin-film solid electrolyte membrane having excellent mechanical strength and ionic conductivity.

[0044] The present invention relates to a solid electrolyte membrane for an all-solid-state battery, which comprises a solid electrolyte in a particle form and an additive having a linear structure.

[0045] The additive with a linear structure serves as a framework for maintaining the mechanical strength of the solid electrolyte membrane, which is composed of solid electrolyte particles. Since the additive with a linear structure is evenly distributed throughout the solid electrolyte membrane, it is able to maintain excellent mechanical strength even when the solid electrolyte membrane is thinned to a very low thickness.

[0046] The additive having a linear structure may be in the form of a polymer fiber. If it is a fiber-type polymer, the type is not particularly limited, and fiber-type polymers commonly used in the art may be used. For example, the additive may include at least one selected from polyphenylene sulfide, polyetheretherketone, polyethylene terephthalate, polyimide, polyamide, polysulfone, polyvinylidene fluoride, polyacrylonitrile, polyethylene and polypropylene, preferably polyphenylene sulfide. Polyphenylene sulfide is one of the super engineering plastics and may be the most preferred because it has excellent strength and excellent physical properties, such as flame retardancy, heat resistance and chemical resistance, thereby improving the safety of the solid electrolyte membrane.

[0047] Furthermore, the additive having a linear structure may have an average diameter of 50 nm to 5 μm, preferably 100 nm to 3 μm, and an average length of 500 nm to 5 mm, preferably 500 nm to 1 mm. Furthermore, when the additive has a linear structure, the ratio of the average length to the average diameter (average length / average diameter) may be 5 to 1000, preferably 10 to 200. By having such a diameter and length, the solid electrolyte membrane can obtain improved mechanical strength.

[0048] The linear additive of the present invention does not act as a binder connecting the solid electrolyte particles, but rather as a framework that maintains the structure of the solid electrolyte membrane. Therefore, since the linear additive is not coated on the surface of the solid electrolyte particles, it can improve ionic conductivity compared to solid electrolyte membranes containing a binder. Furthermore, since the binder content is lower than that of conventional solid electrolyte membranes, the content of the solid electrolyte particles can be increased, thereby improving the ionic conductivity of the solid electrolyte membrane.

[0049] That is, the content of the additive having a linear structure may be 0.5 wt%, 1 wt%, 2 wt%, 3 wt% or 4 wt% or more and 1 wt%, 2 wt%, 3 wt%, 4 wt% or 5 wt% or less relative to the total weight of the solid electrolyte membrane. Specifically, the content of the additive having a linear structure may be 0.5 to 5 wt%, preferably 1 to 3 wt%. Within the above range, the solid electrolyte membrane can exhibit mechanical strength and excellent ionic conductivity. If the content of the additive having a linear structure is less than 0.5 wt%, the mechanical strength of the solid electrolyte membrane is reduced, making it difficult to maintain the structure of the solid electrolyte membrane. If the content of the additive having a linear structure exceeds 5 wt%, there may be the following problem: as the content of the solid electrolyte in particulate form decreases, the ionic conductivity of the solid electrolyte membrane is significantly reduced.

[0050] By including the additive having a linear structure, the solid electrolyte membrane for an all-solid-state battery of the present invention can provide a solid electrolyte membrane having excellent mechanical strength and ion conductivity while having a thin membrane.

[0051] More specifically, the ionic conductivity of the solid electrolyte membrane for an all-solid-state battery of the present invention may be 0.01 to 10 mS / cm, preferably 0.1 to 5 mS / cm.

[0052] In the present invention, the mechanical strength of the solid electrolyte membrane for all-solid-state batteries refers to the degree to which the solid electrolyte membrane for all-solid-state batteries can maintain its structure (free-standing).

[0053] The thickness of the solid electrolyte membrane for an all-solid-state battery may be 5 to 50 μm, preferably 10 to 30 μm. As described above, since the solid electrolyte membrane has a thin film thickness, it can exhibit an effect of improving energy density.

[0054] The solid electrolyte in the form of particles may be a sulfide-based solid electrolyte or a polymer-based solid electrolyte, and the sulfide-based solid electrolyte in the form of particles is preferred.

[0055] Sulfide solid electrolyte contains sulfur (S) and has the ionic conductivity of the metal belonging to Group 1 or Group 2 of the periodic table, which may include Li-PS type glass or Li-PS type glass ceramics. Non-limiting examples of such sulfide solid electrolytes may include Li2S-P2S5, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2S5, Li2S-P2S5-SiS2, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2 or Li2S-GeS2-ZnS, and may include one or more of them. However, the present invention is not particularly limited thereto.

[0056] The polymer solid electrolyte is a composite of lithium salt and polymer resin, that is, a polymer electrolyte material formed by adding polymer resin to solvated lithium salt, which can exhibit a thermal conductivity of about 1×10 -7 S / cm or more, preferably about 1×10 - 5 S / cm or above ionic conductivity.

[0057] The limiting examples of polymer resins can include polyether polymers, polycarbonate polymers, acrylic acid ester polymers, polysiloxane polymers, phosphazene polymers, polyethylene derivatives, alkylene oxide derivatives (such as polyethylene oxide), phosphate polymers, poly-stirring lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride and the polymer comprising ion dissociation groups, and can include one or more thereof. In addition, polymer electrolytes are polymer resins, can be branched copolymers, comb-like polymer resins and cross-linked polymer resins such as obtained by copolymerizing an amorphous polymer (such as PMMA, polycarbonate, polysiloxane (pdms) and / or phosphazene) as a comonomer on a PEO (polyethylene oxide) main chain, and can include one or more thereof.

[0058] In the electrolyte of the present invention, the above lithium salt is an ionizable lithium salt and can be represented as Li + The anion of the lithium salt is not particularly limited, but may be, for example, F-, Cl-, Br- - 、I-、NO3 - 、N(CN)2 - 、BF4 - 、ClO4 - PF6 - 、(CF3)2PF4 - 、(CF3)3PF3 - 、(CF3)4PF2- 、(CF3)5PF - 、(CF3)6P - CF3SO3 - CF3CF2SO3 - 、(CF3SO2)2N - 、(FSO2)2N - CF3CF2(CF3)2CO - 、(CF3SO2)2CH - 、(SF5)3C - 、(CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - 、CH3CO2 - 、SCN - 、(CF3CF2SO2)2N - wait.

[0059] The content of the solid electrolyte in the form of particles may be 95 to 99.5% by weight, preferably 97 to 99% by weight, based on the total weight of the solid electrolyte membrane.

[0060] Furthermore, the present invention relates to an all-solid-state battery comprising a positive electrode, a negative electrode, and a solid electrolyte membrane disposed therebetween, wherein the solid electrolyte membrane may be the solid electrolyte membrane of the present invention described above.

[0061] The all-solid-state battery is a lithium secondary battery that is not limited in terms of positive electrode or negative electrode and may be a lithium-air battery, a lithium oxide battery, a lithium-sulfur battery, or a lithium metal battery.

[0062] The positive electrode may include a positive electrode collector and a positive electrode active material coated on one or both surfaces of the positive electrode collector.

[0063] The positive electrode current collector is used to support the positive electrode active material and is not particularly limited, as long as it is electrochemically stable within the voltage range of the lithium secondary battery and has excellent conductivity. For example, the positive electrode current collector can be at least one metal selected from copper, aluminum, stainless steel, titanium, silver, palladium, nickel, alloys thereof, and combinations thereof. The stainless steel can be surface-treated with carbon, nickel, titanium, or silver, and the alloy can preferably be an aluminum-cadmium alloy. In addition, sintered carbon, a non-conductive polymer surface-treated with a conductive material, or a conductive polymer can be used.

[0064] The positive electrode current collector may have fine irregularities formed on its surface to enhance adhesion with the positive electrode active material, and may be formed in various forms such as a film, sheet, foil, grid, net, porous body, foam, non-woven fabric, and the like.

[0065] The positive active material layer may include a positive active material and optionally a conductive material and a binder.

[0066] The positive electrode active material may vary depending on the type of all-solid-state battery. For example, the positive electrode active material may be, but is not limited to: layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), or compounds substituted with one or more transition metals; lithium manganese oxide, such as Li 1+x Mn 2-x O4 (where x = 0-0.33), LiMnO3, LiMn2O3 and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5 and Cu2V2O7; 1-x M x Nickel-type lithium nickel oxide represented by O2 (wherein M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, x = 0.01-0.3); 2-x M x Lithium manganese composite oxide represented by LiNi O2 (wherein M = Co, Ni, Fe, Cr, Zn or Ta, x = 0.01-0.1) or Li2Mn3MO8 (wherein M = Fe, Co, Ni, Cu or Zn); x Mn 2-x Lithium manganese composite oxide with a spinel structure represented by O4; LiCoPO4; LiFePO4; elemental sulfur (S8); and sulfur-based compounds such as Li2S n (n=1), organic sulfur compounds or carbon-sulfur polymers ((C2S x ) n :x=2.5-50,n=2).

[0067] The conductive material is a material serving as an electron movement path from the current collector to the cathode active material by electrically connecting the electrolyte and the cathode active material, and is not particularly limited as long as it has porosity and conductivity without causing chemical changes in the lithium secondary battery.

[0068] For example, porous carbon-based materials can be used as conductive materials. Such carbon-based materials include carbon black, graphite, graphene, activated carbon, and carbon fibers. Other materials that can be used include metal fibers, such as metal mesh; metal powders, such as copper, silver, nickel, and aluminum; and organic conductive materials, such as polyphenylene derivatives. Conductive materials can be used alone or in combination.

[0069] Products currently sold as conductive materials may include acetylene black series (products from Chevron Chemical Company or Gulf Oil Company), Ketjen Black EC series (products from Armak Company), Vulcan XC-72 (products from Cabot Company), and Super P (products from MMM). For example, acetylene black, carbon black, graphite, etc. may be used.

[0070] In addition, the positive electrode may further include a binder. The binder enhances the binding force between the components constituting the positive electrode and between them and the current collector, and any binder known in the art may be used as the binder.

[0071] For example, the adhesive can be: a fluororesin adhesive, including polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE); a rubber adhesive, including styrene-butadiene rubber (SBR), nitrile rubber and styrene-isoprene rubber; a cellulose adhesive, including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose and regenerated cellulose; a polyol adhesive; a polyolefin adhesive, including polyethylene and polypropylene; a polyimide adhesive; a polyester adhesive; and a silane adhesive, or a mixture or copolymer of two or more thereof.

[0072] The negative electrode includes a negative electrode current collector and a negative electrode active material formed on the negative electrode current collector. In addition, if necessary, the negative electrode can (like the positive electrode) include a conductive material and a binder. In this case, the negative electrode current collector, the conductive material and the binder are as described above.

[0073] The negative electrode active material can be a material that can reversibly insert or remove lithium ions (Li + ), or any material capable of reacting with lithium ions to reversibly form a lithium-containing compound.

[0074] For example, the negative electrode active material may include, but is not limited to, at least one carbon-based material selected from the group consisting of crystalline artificial graphite, crystalline natural graphite, amorphous hard carbon, low crystallinity soft carbon, carbon black, acetylene black, Ketjen black, Super-P, graphene, and fiber carbon, Si-based materials, metal composite oxides such as LixFe2O3 (0≤x≤1), Li x WO2(0≤x≤1), Sn x Me 1-x Me' y O z(Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of Groups 1, 2, and 3 of the periodic table, halogens; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8); lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5; conductive polymers such as polyacetylene; lithium cobalt nickel-based materials; titanium oxides; lithium titanium oxides, etc.

[0075] The manufacturing of the all-solid-state battery is not particularly limited in the present invention and known methods can be used.

[0076] For example, the battery cell is assembled by placing a solid electrolyte film between the positive electrode and the negative electrode and then pressing them into shape. After the assembled battery cell is installed in an external material, it is sealed by thermal compression or the like. A laminated package or a cylindrical or square metal container made of aluminum, stainless steel, etc. is used for the external material.

[0077] For example, the electrodes of the positive electrode and the negative electrode are manufactured by the following slurry coating process: preparing a composition in the form of a slurry containing each electrode active material, a solvent, and an adhesive and coating with it, and then drying it.

[0078] The method of coating the electrode slurry on the current collector may include a method of dispensing the electrode slurry on the current collector and uniformly dispersing the electrode slurry using a doctor blade or the like, and methods such as die casting, comma coating, and screen printing. In addition, after molding on a separate substrate, the electrode slurry can be bonded to the current collector by pressing or laminating. In this case, the thickness of the finally to-be-coated layer can be adjusted by adjusting the concentration of the slurry, the number of coatings, etc.

[0079] The drying process is a process for removing the solvent and moisture in the slurry to dry the slurry coated on the metal current collector, and it can vary depending on the solvent used. For example, the drying process is carried out in a vacuum oven at 50 to 200 °C. Examples of the drying method may include a drying method by warm air, hot air, or low-humidity air, a vacuum drying method, and a drying method using (far) infrared radiation or electron beam irradiation. The drying time is not particularly limited, but it is usually in the range of 30 seconds to 24 hours.

[0080] After the drying process, a cooling process may be further included, and the cooling process may be a cooling process of slowly cooling to room temperature so that a recrystallization structure of the adhesive is well formed.

[0081] Furthermore, if necessary, in order to increase the capacity density of the electrode and increase the adhesion between the current collector and the active material after the drying process, a roll pressing process may be performed, wherein the electrode is passed between two rollers heated at a high temperature and compressed to a desired thickness. In the present invention, the roll pressing process is not particularly limited, and known roll pressing processes are feasible. For example, the roll pressing process is performed by passing between rotating rollers or by using a flat press.

[0082] The shape of the all-solid-state battery is not particularly limited and may have various shapes such as a cylindrical shape, a stacked type, and a coin type.

[0083] Hereinafter, preferred embodiments of the present invention will be described to facilitate understanding of the present invention. However, it will be apparent to those skilled in the art that the following embodiments are illustrative of the present invention and that various changes and modifications may be made within the scope and spirit of the present invention. Such changes and modifications are within the scope of the appended claims.

[0084] <Manufacturing of solid electrolyte membranes for all-solid-state batteries>

[0085] Example 1

[0086] 98.5 wt % of argyrodite (Li 6 PS 5 Cl) as a solid electrolyte and 1.5 wt % of polyphenylene sulfide as an additive having a linear structure were dispersed in anisole and stirred to prepare a slurry for forming a solid electrolyte layer.

[0087] Polyethylene terephthalate was used as a release film, and the slurry for forming the solid electrolyte layer was applied on the release film, vacuum dried at 100° C. for 12 hours, and then roll-pressed to form a solid electrolyte membrane for an all-solid-state battery with a thickness of 38 μm.

[0088] Example 2

[0089] A solid electrolyte membrane for an all-solid-state battery having a thickness of 45 μm was prepared in the same manner as in Example 1, except that 97 wt % of argyrodite (Li 6 PS 5 Cl) and 3 wt % of polyphenylene sulfide were used.

[0090] Example 3

[0091] A solid electrolyte membrane for an all-solid-state battery having a thickness of 40 μm was prepared in the same manner as in Example 1, except that 95 wt % of argyrodite (Li 6 PS 5 Cl) and 5 wt % of polyphenylene sulfide were used.

[0092] Comparative Example 1

[0093] Only argyrodite (Li6PS5Cl) was used as a solid electrolyte and filled between titanium molds (Ti molds) to prepare a solid electrolyte membrane for all-solid-state batteries with a thickness of 732 μm.

[0094] Comparative Example 2

[0095] 95 wt % of argyrodite (Li 6 PS 5 Cl) as a solid electrolyte and 5 wt % of polytetrafluoroethylene as a binder were dispersed in anisole and stirred to prepare a slurry for forming a solid electrolyte layer.

[0096] A slurry for forming a solid electrolyte layer was applied onto a release film made of polyethylene terephthalate and vacuum-dried at 100° C. for 12 hours to prepare a solid electrolyte membrane for an all-solid-state battery having a thickness of 50 μm.

[0097] Comparative Example 3

[0098] The same procedure as in Comparative Example 1 was performed except that 97 wt% of argyrodite (Li6PS5Cl) and 3 wt% of polytetrafluoroethylene were used. However, due to the low content of the binder, the strength was reduced and the structure could not be maintained, resulting in cracks.

[0099] Comparative Example 4

[0100] A solid electrolyte membrane for an all-solid-state battery having a thickness of 49 μm was prepared in the same manner as in Example 1, except that a nonwoven fabric (porosity of 48%, thickness of 38 μm) was used instead of the additive having a linear structure.

[0101] Experimental Example 1. Measuring the ionic conductivity of a solid electrolyte membrane for all-solid-state batteries

[0102] The ionic conductivities of the solid electrolyte membranes for all-solid-state batteries prepared in Examples 1 to 3 and Comparative Examples 1, 2, and 4 were measured.

[0103] After the solid electrolyte membranes for all-solid-state batteries of Examples 1 to 3 and Comparative Examples 1, 2 and 4 were respectively placed between SUS, the ionic resistance was measured by impedance spectroscopy at room temperature, and the values ​​of ionic conductivity were calculated. The results are shown in Table 1 below.

[0104] Table 1

[0105] Thickness (μm) <![CDATA[Area (cm 2 )]]> Resistance (Ohm) Ionic conductivity (mS / cm) Example 1 38 1.77 3 0.72 Example 2 45 1.77 3.8 0.67 Example 3 40 1.77 4.2 0.54 Comparative Example 1 732 1.77 23.4 1.77 Comparative Example 2 50 1.77 8.2 0.35 Comparative Example 4 49 1.77 10.7 0.26

[0106] The results in Table 1 demonstrate that the solid electrolyte membranes of Examples 1 to 3, each containing a linear additive supporting the solid electrolyte, exhibit excellent ionic conductivity. Furthermore, it was found that the structure (free-standing) of the solid electrolyte membrane was maintained even with the addition of a small amount of additive, from 0.5 to 5% by weight.

[0107] Meanwhile, in the case of Comparative Example 1, which used only a solid electrolyte, when slurry coating was performed to produce a thin film, the film broke, and it was impossible to measure ionic conductivity. When a solid electrolyte membrane of the aforementioned thickness was produced using a mold for measuring ionic conductivity, high ionic conductivity was exhibited. That is, Comparative Example 1 had high ionic conductivity, but it was found that it was impossible to form a thin film.

[0108] In the case of the solid electrolyte membrane of Comparative Example 2 using a binder instead of the additive having a linear structure, it was found that the ionic conductivity was lower than that of the solid electrolyte membrane of Example 3 using the same amount of the additive having a linear structure, and the solid electrolyte membrane of Comparative Example 3 failed to maintain the structure of the solid electrolyte membrane due to the low binder content.

[0109] Comparative Example 4, which used a nonwoven fabric instead of a linear additive, exhibited lower ionic conductivity than Examples 1-3. This result occurred because the solid electrolyte was difficult to completely fill the pores between the fibers, despite the nonwoven fabric being connected in a linear structure. Using a nonwoven fabric can also limit the bonding strength between the electrodes.

[0110] Therefore, it can be seen that the solid electrolyte membrane for an all-solid-state battery of the present invention can be thinned and exhibits high ion conductivity.

Claims

1. A solid electrolyte membrane for an all-solid-state battery, comprising a solid electrolyte in a particle form and an additive having a linear structure; in, The content of the additive having a linear structure is 1 wt % to 5 wt % based on the total weight of the solid electrolyte membrane for an all-solid-state battery; wherein the additive having a linear structure has an average length of 500 nm to 5 mm and an average diameter of 50 nm to 5 μm; Wherein, the thickness of the solid electrolyte membrane for all-solid-state batteries is 5 μm to 50 μm; wherein the additive does not serve as a binder connecting the solid electrolyte in the form of particles, but serves as a framework for maintaining the structure of the solid electrolyte membrane; wherein the ratio of the average length to the average diameter of the additive having a linear structure is 10 to 200; The additive having a linear structure includes at least one selected from the group consisting of polyphenylene sulfide, polyetheretherketone and polysulfone.

2. The solid electrolyte membrane for an all-solid-state battery according to claim 1, wherein The additive having a linear structure is in the form of polymer fibers.

3. The solid electrolyte membrane for an all-solid-state battery according to claim 1, wherein The additive having a linear structure is present in an amount of 1 wt % to 3 wt % based on the total weight of the solid electrolyte membrane for an all-solid-state battery.

4. The solid electrolyte membrane for an all-solid-state battery according to claim 1, wherein The additive having a linear structure further includes at least one selected from the group consisting of polyethylene terephthalate, polyimide, polyamide, polyvinylidene fluoride, polyacrylonitrile, polyethylene, and polypropylene.

5. The solid electrolyte membrane for an all-solid-state battery according to claim 1, wherein The additive having a linear structure has an average length of 500 nm to 1 mm and an average diameter of 100 nm to 3 μm.

6. The solid electrolyte membrane for an all-solid-state battery according to claim 1, wherein The solid electrolyte is a sulfide-based solid electrolyte or a polymer-based solid electrolyte.

7. The solid electrolyte membrane for an all-solid-state battery according to claim 1, wherein The thickness of the solid electrolyte membrane for an all-solid-state battery is 10 μm to 30 μm.

8. The solid electrolyte membrane for an all-solid-state battery according to claim 1, wherein The ionic conductivity of the solid electrolyte membrane for an all-solid-state battery is 0.01 mS / cm to 10 mS / cm.

9. An all-solid-state battery, comprising a positive electrode, a negative electrode, and a solid electrolyte membrane disposed between the positive electrode and the negative electrode, wherein: The solid electrolyte membrane is the solid electrolyte membrane according to any one of claims 1 to 8.

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