A method for restoring the ionic conductivity of a sulfide-based solid electrolyte, a sulfide-based solid electrolyte whose ionic conductivity has been restored by this method, and a lithium-ion secondary battery containing this solid electrolyte.

Abstract

The present invention relates to a method for restoring the ionic conductivity of a sulfide-based solid electrolyte, the method comprising the steps of: a) bringing a sulfide-based solid electrolyte whose ionic conductivity has decreased into contact with a solvent having a dielectric constant of less than 7; and b) drying the solid electrolyte that has been in contact with the solvent; a sulfide-based solid electrolyte whose ionic conductivity has been restored by this method; and a lithium ion secondary battery including this solid electrolyte.

Description

[Technical Field]

[0001] This application claims priority rights under Korean Patent Application No. 10-2022-0077323 dated June 24, 2022, and Korean Patent Application No. 10-2023-0075819 dated June 13, 2023, and all content disclosed in the documents of said Korean patent applications is incorporated herein by reference.

[0002] The present invention relates to a method for restoring the ionic conductivity of a sulfide-based solid electrolyte, a sulfide-based solid electrolyte whose ionic conductivity has been restored by this method, and a lithium-ion secondary battery containing this solid electrolyte. [Background technology]

[0003] Due to their high energy density, lithium-ion batteries are used in a variety of applications, including electric automobiles and portable information terminals.

[0004] Conventional lithium-ion rechargeable batteries mostly use liquid electrolytes such as organic solvents, but safety issues such as electrolyte leakage and the resulting fire hazard have been constantly raised. For this reason, interest in all-solid-state batteries that use inorganic solid electrolytes has been growing recently.

[0005] All-solid-state batteries are based on technology that eliminates organic solvents (liquid electrolytes), offering the advantage of being able to manufacture battery cells safely and simply. To improve the performance of such all-solid-state batteries, a solid electrolyte with high ion conductivity and safety is required, and related research is actively being conducted.

[0006] Sulfide-based solid electrolytes have a lithium ion yield (transport number) of approximately 1 and an ionic conductivity of approximately 10 -3Since it is S / cm, it has attracted attention as a solid electrolyte that contributes to the improvement of battery characteristics. Sulfide-based solid electrolytes are manufactured by methods such as the melt quenching method and the solid phase reaction method.

[0007] However, sulfide-based solid electrolytes are likely to react with moisture and have the characteristic that even a small amount of moisture causes changes in shape and properties. For example, sulfide-based solid electrolytes react with moisture in the air to generate hydrogen sulfide (H2S) gas, and have the characteristic that the value of ionic conductivity significantly decreases. Specifically, when a sulfide-based solid electrolyte is exposed to a dry room environment for about 5 hours, the ionic conductivity decreases by 20 to 60%.

[0008] The ionic conductivity of a solid electrolyte has an important influence on the performance of a secondary battery to which the solid electrolyte is applied. Therefore, the ionic conductivity of a solid electrolyte is used as one of the index values for evaluating the performance of a secondary battery.

[0009] Therefore, in order to improve the performance of a secondary battery, in addition to the technology for manufacturing a solid electrolyte with high ionic conductivity, the development of technology for stably maintaining and recovering the ionic conductivity of the manufactured solid electrolyte is also required.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0011] The inventors of the present invention intensively studied a method for recovering the ionic conductivity of a sulfide-based solid electrolyte whose ionic conductivity has decreased due to the external environment, and found that when a sulfide-based solid electrolyte with decreased ionic conductivity is treated with a specific solvent, the ionic conductivity recovers again, and completed the present invention.

[0012] Therefore, the present invention aims to provide a method for restoring the ionic conductivity of a sulfide-based solid electrolyte, a sulfide-based solid electrolyte whose ionic conductivity has been restored by this method, and a lithium-ion secondary battery containing this solid electrolyte. [Means for solving the problem]

[0013] To achieve the above objective, the present invention, a) The step of contacting a sulfide-based solid electrolyte with reduced ionic conductivity with a solvent having a dielectric constant of less than 7; and The present invention provides a method for restoring the ionic conductivity of a sulfide-based solid electrolyte, comprising the step of (b) drying the solid electrolyte that has come into contact with the solvent.

[0014] Furthermore, the present invention is The present invention provides a sulfide-based solid electrolyte in which ionic conductivity has been restored by the method described above.

[0015] Furthermore, the present invention is Positive electrode; negative electrode; comprising a solid electrolyte interposed between the positive electrode and the negative electrode, The solid electrolyte provides a lithium-ion secondary battery containing the solid electrolyte of the present invention. [Effects of the Invention]

[0016] The present invention provides a method for restoring the ionic conductivity of a sulfide-based solid electrolyte, which efficiently restores the ionic conductivity of the solid electrolyte through a simple process.

[0017] Furthermore, the method for restoring ionic conductivity and the sulfide-based solid electrolyte whose ionic conductivity has been restored by this method make it possible to use a solid electrolyte with high ionic conductivity during battery assembly.

[0018] Furthermore, the lithium-ion secondary battery of the present invention provides the effect of improving battery performance by including the solid electrolyte described above. [Brief explanation of the drawing]

[0019] [Figure 1] This graph shows the measured ionic conductivity of solid electrolytes produced in the comparative example, comparative example, and example of the present invention. Modes for carrying out the invention

[0020] The present invention will be described in more detail below.

[0021] The present invention provides a method for restoring the ionic conductivity of a sulfide-based solid electrolyte. a) The step of contacting a sulfide-based solid electrolyte with reduced ionic conductivity with a solvent having a dielectric constant of less than 7; and b) a step of drying the solid electrolyte that has come into contact with the solvent; characterized by comprising these steps.

[0022] In one embodiment of the present invention, the decrease in ionic conductivity in step a) may be due to moisture exposure of the sulfide-based solid electrolyte, and such moisture exposure may be due to moisture exposure due to contact with moisture, exposure to a moisture-containing atmosphere, etc.

[0023] In one embodiment of the present invention, the decrease in ionic conductivity in step a) above may be a decrease of 1-80%, 6-80%, 1-70%, or 6-70%, with respect to the ionic conductivity of the sulfide-based solid electrolyte before exposure to the atmosphere being 100%. Alternatively, it may be a decrease of 6-60%, 10-60%, 20-60%, or 30-50%.

[0024] In one embodiment of the present invention, the recovery of ionic conductivity in step a) above may be achieved by increasing the ionic conductivity of the sulfide-based solid electrolyte whose ionic conductivity has decreased by a range consisting of a lower limit selected from 1%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 25%, 30%, 35%, and 40%, and an upper limit selected from 300%, 250%, 200%, 150%, 100%, 80%, 60%, and 40%. For example, it may be increased by 1 to 300% or 10 to 300%. Furthermore, the ionic conductivity of a sulfide-based solid electrolyte whose ionic conductivity has decreased may be increased to 50-100%, 50-98%, 50-95%, 70-95%, 80-95%, 80-94%, or 85-94%, using the ionic conductivity of the sulfide-based solid electrolyte before the decrease in ionic conductivity (100%) as a baseline.

[0025] Examples of solvents with a dielectric constant of less than 7 include xylene, isobutyl butyrate, anisole, toluene, hexane, heptane, isobutyl isobutyrate (IBIB), decane, dibutyl ether, and butyl bytyrate, which may be used individually or in combination of two or more. In the foregoing, xylene may be ortho, meta, or paraxylene.

[0026] In particular, one or more solvents consisting of xylene, isobutyl butyrate, and anisole may be used more preferably.

[0027] The solvent may more preferably have a dielectric constant of 1 to 5.

[0028] Since the aforementioned solvent must be non-reactive with the solid electrolyte, a nonpolar or weakly polar solvent may be used. Specifically, a solvent with a dipole moment of 5D or less may be used.

[0029] The method for restoring the ionic conductivity of the sulfide-based solid electrolyte in the present invention can be applied to solid electrolytes in a particulate (powder) state.

[0030] Sulfide-based solid electrolytes have a lithium ion yield (transport number) of approximately 1 and an ionic conductivity of approximately 10. -3 Because of its S / cm ratio, it is attracting attention as a solid electrolyte that contributes to improving battery performance.

[0031] However, sulfide-based solid electrolytes readily react with water, and even a small amount of water can alter their shape and properties, significantly reducing their ionic conductivity. Specifically, when sulfide-based solid electrolytes are exposed to a dry room environment (H2O 100-160 ppm) for 5 hours, their ionic conductivity decreases by 20-60%.

[0032] In the manufacturing process of all-solid-state or semi-solid-state batteries, sulfide-based solid electrolytes are sometimes used immediately after manufacturing, but it is more common for them to undergo a storage process before being used. Therefore, if sulfide-based solid electrolytes whose ionic conductivity has decreased during the storage process are used directly in the manufacture of all-solid-state or semi-solid-state batteries, this can cause a decrease in battery performance.

[0033] The present invention is characterized by providing a solution that can efficiently resolve the aforementioned problems.

[0034] In one embodiment of the present invention, contact between the sulfide-based solid electrolyte and the solvent can be carried out by various methods known in the art. For example, this can be done by mixing the solid electrolyte with the solvent, spraying the solvent onto the solid electrolyte, or immersing the solid electrolyte in the solvent.

[0035] In some cases, it is preferable to carry out the contact between the sulfide-based solid electrolyte and the solvent in such a way that the entire surface of the sulfide-based solid electrolyte becomes wet with the solvent.

[0036] The mixing may usually be carried out for 1 minute or more, preferably for 1 minute to 1 hour, and more preferably for 1 minute to 10 minutes. However, when the amount of the solid electrolyte to be processed increases, the processing time also increases proportionally, so it is not limited to the above time.

[0037] In one embodiment of the present invention, the mixing is preferably carried out by stirring the mixture, and the stirring may be carried out, for example, in the range of 100 rpm to 3000 rpm, preferably 1000 rpm to 2000 rpm.

[0038] In one embodiment of the present invention, the drying is preferably carried out under a vacuum atmosphere.

[0039] The drying method is not particularly limited, but for example, it may be preferably carried out under heating conditions. At this time, the drying temperature may be, for example, 25 to 100 °C, and more preferably 45 to 70 °C.

[0040] In one embodiment of the present invention, the cause of the decrease in the ionic conductivity of the sulfide-based solid electrolyte is not particularly limited. For example, it may be due to the exposure of the sulfide-based solid electrolyte to moisture, and the moisture exposure may be moisture exposure due to contact with moisture, exposure to the atmosphere containing moisture, or the like.

[0041] The present invention can be preferably applied when the ionic conductivity decreases due to contact with the atmosphere containing moisture after the production of the sulfide-based solid electrolyte.

[0042] In one embodiment of the present invention, the sulfide-based solid electrolyte is not particularly limited. For example, Li 10 GeP2S 12 , Li2S-P2S5 glasses, thio-LISICONS, Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li6PS5X (LPSX; X = Cl, Br, I) argyrodites, Li 12-m-x+ (M m+ Y4 2- )Y 2-x 2- X x - (Here, M = Si, Ge, Sn, P, As; Y = O, S, Se, Te; X = Cl, Br, I; 0 ≤ x ≤ 2) may be one or more elements selected from the group consisting of these elements. However, it is not limited to these, and any sulfide-based solid electrolyte can be applied without particular restriction.

[0043] Furthermore, the present invention is This invention relates to a sulfide-based solid electrolyte whose ionic conductivity has been restored by the method described above.

[0044] The aforementioned sulfide-based solid electrolyte is a) A step of contacting a sulfide-based solid electrolyte with reduced ionic conductivity with one or more solvents consisting of xylene, isobutyl butyrate, and anisole; and b) The solid electrolyte that has come into contact with the solvent may be manufactured by the step of drying the solid electrolyte.

[0045] Since the aforementioned manufacturing method can be directly applied as described above, any redundant information will be omitted.

[0046] Furthermore, the present invention is Positive electrode; negative electrode; comprising a solid electrolyte interposed between the positive electrode and the negative electrode, The solid electrolyte provides a lithium-ion secondary battery containing the sulfide-based solid electrolyte of the present invention.

[0047] The lithium-ion secondary battery may be an all-solid-state or semi-solid-state battery.

[0048] The following will explain the technical details related to the present invention with specific examples.

[0049] Sulfide solid electrolyte The sulfide-based solid electrolyte according to the present invention includes sulfide-based solid electrolyte particles treated with a solvent as described above, and the particles may be manufactured into a film-like sulfide-based solid electrolyte by a dry or wet process.

[0050] The sulfide-based solid electrolyte may include a mixture in which binder particles are dry-mixed together with the sulfide-based solid electrolyte particles.

[0051] The sulfide-based solid electrolyte may be manufactured by coating a slurry containing a binder and a solvent together with the sulfide-based solid electrolyte particles onto a substrate and drying it.

[0052] The dry process is a method for producing a solid electrolyte sheet by pressurizing solid electrolyte powder, and can be carried out, for example, by a process of stacking solid electrolyte powder, positive electrode active material powder, and negative electrode active material powder, and pressurizing them to produce a cell.

[0053] The solid electrolyte powder may further contain a binder powder. Examples of binder powders used in the dry process include, but are not limited to, PTFE.

[0054] In the above, the binder powder may be included in an amount of 1 to 5 parts by weight based on 100 parts by weight of the solid electrolyte powder.

[0055] The aforementioned wet process is a method for producing a solid electrolyte sheet by coating a substrate with a slurry containing a solvent, a binder, and solid electrolyte powder.

[0056] According to a preferred embodiment of the present invention, the solid electrolyte slurry may contain 40-70% by weight of the solid electrolyte, 1-5% by weight of the binder, and 20-59% by weight of the solvent.

[0057] The binder may be, but is not limited to, acrylonitrile butadiene rubber (NBR), acrylic polymers, or silicone polymers.

[0058] The solvent may include, but is not limited to, xylene, hexane, benzene, anisole, isobutyl isobutyrate, or toluene.

[0059] The sulfide-based solid electrolyte particles are not particularly limited, and any known sulfide-based solid electrolyte particles used in this field may be used. The sulfide-based solid electrolyte particles may be purchased commercially, or amorphous sulfide-based solid electrolyte particles may be manufactured through a crystallization process.

[0060] For example, Li 10 GeP2S 12 Li2S-P2S5 glass, thio-LISICONS, Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 Li6PS5X(LPSX;X=Cl,Br,I) argyrodite, Li 12-m-x + (M m+ Y4 2- )Y 2-x 2- X x - (Here, M = Si, Ge, Sn, P, As; Y = O, S, Se, Te; X = Cl, Br, I; 0 ≤ x ≤ 2) may be one or more types selected from the group consisting of these, etc. However, it is not limited to these, and any sulfide-based solid electrolyte particles may be used without particular restriction.

[0061] The average particle size of the sulfide-based solid electrolyte particles may be within the range used in known all-solid-state or semi-solid-state batteries, for example, 0.1 μm to 10 μm, preferably 1 μm to 3 μm. If the average particle size is less than the above range, there is a risk of particle aggregation, and if it exceeds the above range, the porosity of the manufactured solid electrolyte may be high, leading to a decrease in battery characteristics such as reduced capacity, difficulty in thin-film formation, and disadvantages in terms of the final energy density of the cell. Preferably, these sulfide-based solid electrolyte particles have an ionic conductivity of 1 × 10⁻⁶ -3 Preferably, it is S / cm or higher, 5 × 10 -3 A value of S / cm or higher is even more preferable.

[0062] The sulfide-based solid electrolyte may further contain other known solid electrolyte particles in addition to the solid electrolyte particles described above, for example, an inorganic solid electrolyte or an organic solid electrolyte.

[0063] Examples of the inorganic solid electrolytes include Li2O-B2O3, Li2O-B2O3-P2O5, Li2O-V2O5-SiO2, Li3PO4, Li2O-Li2WO4-B2O3, LiPON, LiBON, Li2O-SiO2, LiI, Li3N, and Li5La3Ta2O. 12 Li7La3Zr2O 12 Li6BaLa2Ta2O 12 Li3PO (4-3 / 2w) N W (w is w<1), Li 3.6 Si 0.6 P 0.4 You may also use O4 or similar.

[0064] As the organic solid electrolyte, for example, a mixture of lithium salt with polymer-based materials such as polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, polyagitation lysine, polyester sulfide, polyvinyl alcohol, or polyvinylidene fluoride may be used.

[0065] Manufacturing of all-solid-state batteries The all-solid-state battery according to the present invention can be manufactured with a structure comprising a positive electrode and a negative electrode, with the aforementioned sulfide-based solid electrolyte disposed between them.

[0066] The all-solid-state battery is manufactured, for example, through a dry compression process in which electrodes and a solid electrolyte are manufactured in powder form, then placed into a predetermined mold and pressed, or through a slurry coating process in which a slurry containing a solid electrolyte, a solvent, and a binder is manufactured, coated onto electrodes or release paper, and then dried. The method for manufacturing an all-solid-state battery having the above configuration is not particularly limited in the present invention and can be carried out by methods known in the art.

[0067] As an example, the all-solid-state battery can be manufactured by placing a solid electrolyte between the positive and negative electrodes, compressing and molding the assembly to form a cell, placing the assembled cell inside an outer casing, and then sealing it by heat compression or the like. As the outer casing, laminate cases made of aluminum, stainless steel, cylindrical or rectangular metal containers, or pouch-type containers such as aluminum pouches may be used.

[0068] The structure, components, and manufacturing method of the all-solid-state battery described above can be freely adapted to the known art of this field.

[0069] <Positive electrode> The positive electrode of the all-solid-state battery according to the present invention is not particularly limited, and any positive electrode known in this art may be used without restriction. Specifically, a positive electrode in which a positive electrode active material is laminated on a positive electrode current collector may be used.

[0070] As the positive electrode current collector, a material that does not cause chemical changes in the battery and has high conductivity may be used. For example, stainless steel, aluminum, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. may be used.

[0071] The positive electrode active material may vary depending on the application of the lithium secondary battery, such as LiNi 0.8-x Co 0.2 Al x O2, LiCo x Mn y O2, LiNi x Co y O2, LiNi x Mn y O2, LiNi x Co y Mn z O2, LiCoO2, LiNiO2, LiMnO2, LiFePO4, LiCoPO4, LiMnPO4, and Li4Ti5O 12 and other lithium metal oxides (0 < x, y, or z < 1); chalcogenides such as Cu2Mo6S8, FeS, CoS, and NiS; or oxides, sulfides, or halides of scandium, ruthenium, titanium, vanadium, molybdenum, chromium, manganese, iron, cobalt, nickel, copper, zinc, etc. Although it may be used, it is not limited to these. As the oxide or sulfide, TiS2, ZrS2, RuO2, Co3O4, Mo6S8, V2O5, etc. may be used.

[0072] The shape of the positive electrode active material is not particularly limited and may be particulate, for example, spherical, elliptical, rectangular parallelepiped, etc. The average particle diameter of the positive electrode active material may be within the range of 1 to 50 μm, but is not limited thereto.

[0073] The positive electrode may further contain a binder. As the binder, a fluorine-containing binder such as polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); one or more selected from the group consisting of polyacrylonitrile (PAN), nitrile butadiene rubber (NBR), styrene-butadiene-styrene copolymer (SBS), polybutadiene, styrene-ethylene-butylene-styrene copolymer (SEBS), silicone rubber (SR), hydrogenated nitrile butadiene rubber (HNBR), poly(ethylene vinyl acetate) (PEVA), poly(methyl methacrylate) (PMMA), polyisobutene (PIB), etc. may be used. However, it is not limited to these.

[0074] The content of the binder is not particularly limited as long as it is sufficient to fix the positive electrode active material, and may be, for example, in the range of 0 to 10% by weight relative to the entire positive electrode.

[0075] The positive electrode may further contain a conductive material, such as nickel powder, cobalt oxide, titanium oxide, or carbon. The carbon may be one or more selected from the group consisting of Ketjenblack, acetylene black, furnace black, graphite, carbon fiber, and fullerene.

[0076] The content of the conductive material may be selected considering other battery conditions such as the type of conductive material, and may be included in a range of 1 to 10% by weight relative to the entire positive electrode.

[0077] The positive electrode may also further contain a sulfide-based solid electrolyte in an amount of about 20% by weight.

[0078] <Negative electrode> The negative electrode of the all-solid-state battery according to the present invention is not particularly limited, and any negative electrode known in this art may be used without restriction. Specifically, lithium metal may be laminated alone on a negative electrode current collector, or a negative electrode with laminated negative electrode active material may be used, or only a current collector may be used (anodless), or a protective layer may be applied thereon.

[0079] The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the all-solid-state battery and is conductive. For example, stainless steel, aluminum, titanium, calcined carbon, copper or stainless steel surface treatment with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. Furthermore, the negative electrode current collector may be in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric, with fine irregularities formed on its surface, similar to the positive electrode current collector.

[0080] As the negative electrode active material, one or more selected from the group consisting of lithium metal, lithium alloy, lithium metal composite oxide, lithium-containing titanium composite oxide (LTO), and combinations thereof may be used.

[0081] The lithium alloy may be an alloy composed of lithium and at least one metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Al, and Sn.

[0082] The lithium metal composite oxide is an oxide (MeO x ) of any one metal selected from the group consisting of lithium and Si, Sn, Zn, Mg, Cd, Ce, Ni, and Fe, and as an example, it may be LixFe2O3 (0 < x ≦ 1) or LixWO2 (0 < x ≦ 1).

[0083] Also, as the negative electrode active material, Sn x Me 1-x Me’ y O z (Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8) and other metal composite oxides; oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5 may be used, and a carbon-based negative electrode active material such as crystalline carbon, amorphous carbon, or a carbon composite may be used alone or in combination of two or more.

[0084] The negative electrode can be manufactured by a method known in this field.

[0085] Hereinafter, examples will be given and described in detail to specifically explain the present invention. However, the examples according to the present invention can be deformed into various other forms, and the scope of the present invention should not be construed as being limited to the examples described below. The examples of the present invention are provided to more fully explain the present invention to those with average knowledge in the industry.

[0086] <Sulfide-based solid electrolytes used in the examples and comparative examples> In the examples and comparative examples of the present invention, an argyrodite-based solid electrolyte (manufacturer: Mitsui) was purchased and used.

[0087] Control Example 1: Measurement of ionic conductivity of sulfide-based solid electrolytes The purchased argyrodite-based solid electrolyte powder was formed into pellets at 360 MPa under conditions where it was not exposed to the atmosphere, and its ionic conductivity was measured by sandwiching it between stainless steel electrodes. The ionic conductivity was 3.06 mS / cm.

[0088] Control Examples 2-4: Measurement of ionic conductivity immediately after manufacturing of sulfide-based solid electrolytes The purchased argyrodite-based solid electrolyte powder was mixed with each of the solvents listed in Table 1 below, while not exposed to the atmosphere, and mixed at 2,000 rpm for 6 minutes. Then, it was dried under vacuum conditions at 100°C for 6 hours.

[0089] Each of the dried solid electrolyte powders was formed into pellets, sandwiched between stainless steel electrodes, and its ionic conductivity was measured. The results are shown in Table 1 below.

[0090] [Table 1]

[0091] From the aforementioned experiment, it was confirmed that when a sulfide-based solid electrolyte not exposed to moisture is treated with a solvent with a dielectric constant of less than 7, there is almost no change in ionic conductivity compared to the case without solvent treatment in Control Example 1. This difference is likely due to a decrease in ionic conductivity caused by contact with air and impurities during solvent treatment.

[0092] Comparative Example 1: Measurement of ionic conductivity of sulfide-based solid electrolytes after storage The argyrodite-based solid electrolyte powder was exposed to air for 5 hours in a dry room (H2O 100-160 ppm level). The exposed solid electrolyte powder was then formed into pellets and sandwiched between stainless steel electrodes for measurement of ionic conductivity. The ionic conductivity was 1.99 mS / cm.

[0093] The results of the above experiment confirmed that the ionic conductivity decreased by 35% compared to the electrical conductivity of control example 1.

[0094] Examples 1-3: Measurement of ionic conductivity of sulfide-based solid electrolytes after storage and solvent mixing treatment. A sulfide-based solid electrolyte, exposed to air in the same manner as in Comparative Example 1, was mixed with each of the solvents listed in Table 2 below and mixed at 2,000 rpm for 6 minutes. The mixture was then dried under vacuum conditions at 100°C for 6 hours.

[0095] Each of the dried solid electrolyte powders was formed into pellets, sandwiched between stainless steel electrodes, and its ionic conductivity was measured. The results are shown in Table 2 below.

[0096] [Table 2]

[0097] From the above experiment, it can be confirmed that the ionic conductivity of the sulfide-based solid electrolyte, which decreased due to exposure to the dry room (a 35% decrease), recovered to 94% of that of the solid electrolyte measured without exposure to the dry room (control example 1) by the solvent treatment.

[0098] Example 4 and Comparative Example 2: Manufacturing of All-Solid-State Batteries An all-solid-state battery was manufactured using the sulfide-based solid electrolyte used for measuring ionic conductivity in the aforementioned Control Example 1 (Control Example 5).

[0099] Furthermore, an all-solid-state battery was manufactured using the sulfide-based solid electrolyte used for measuring ionic conductivity in Comparative Example 1 (Comparative Example 2).

[0100] Furthermore, an all-solid-state battery was manufactured using the sulfide-based solid electrolyte used for measuring ionic conductivity in Example 3 (Example 4).

[0101] (1) Manufacturing of all-solid electrolytes Slurry compositions were prepared by mixing the sulfide-based solid electrolyte powder used for measuring ionic conductivity in Control Example 1, the sulfide-based solid electrolyte powder used for measuring ionic conductivity in Example 3, and the sulfide-based solid electrolyte powder used for measuring ionic conductivity in Comparative Example 1 with a rubber-based binder and xylene as a solvent in a weight ratio of 55:2:43. Each slurry composition was coated onto release paper by the Tape-cast method and then dried at 100°C under vacuum for 6 hours. Subsequently, a 30 μm thick solid electrolyte film was formed by pressurizing at 500 MPa. After that, the release paper was removed and the free-standing sulfide-based solid electrolyte film was applied to a cell.

[0102] (2) Manufacturing of all-solid-state batteries The sulfide-based solid electrolyte membranes manufactured as described above were stacked in the order of positive electrode (NCM811), solid electrolyte membrane, and negative electrode (Li metal). After pressurizing at a pressure of 200 MPa, current collectors were attached to the positive and negative electrodes, and the cells were assembled into aluminum pouch cells to produce all-solid-state batteries for Control Example 5, Example 4, and Comparative Example 2, respectively.

[0103] Experimental Example 1: Evaluation of the characteristics of all-solid-state batteries The Coulomb efficiencies of the all-solid-state batteries in Control Example 5, Example 4, and Comparative Example 2 were compared. The life characteristics of each battery in Control Example 5, Example 4, and Comparative Example 2 were measured at 60°C using a 1C charge / discharge method during 0.05C charging and discharging, and the life performance of the batteries was evaluated. The results are shown in Table 3 below.

[0104] [Table 3]

[0105] As a result of the above evaluation, it was confirmed that the sulfide-based solid electrolyte (Example 3) whose ionic conductivity was restored by the method of the present invention did not degrade the quality of the battery compared to the solid electrolyte (Control Example 1) in which the ionic conductivity was not reduced.

Claims

1. a) A step of contacting a sulfide-based solid electrolyte with reduced ionic conductivity with one or more solvents selected from the group consisting of xylene, anisole, and isobutyl isobutyrate (IBIB); and b) A method for restoring the ionic conductivity of a sulfide-based solid electrolyte, comprising the step of drying the solid electrolyte that has come into contact with the solvent.

2. The method for restoring ionic conductivity according to claim 1, characterized in that the decrease in ionic conductivity in step a) above is caused by the exposure of water in the sulfide-based solid electrolyte.

3. The method for restoring ionic conductivity according to claim 1, characterized in that the decrease in ionic conductivity in step a) above is caused by exposure of the sulfide-based solid electrolyte to air containing moisture.

4. The method for restoring ionic conductivity according to claim 1, characterized in that the decrease in ionic conductivity in step a) above is a decrease from 1% to 80%, with the ionic conductivity of the sulfide-based solid electrolyte before exposure to the atmosphere being 100%.

5. The method for restoring ionic conductivity according to claim 1, characterized in that the restoration of ionic conductivity in step a) increases the ionic conductivity of a sulfide-based solid electrolyte whose ionic conductivity has decreased from 1% to 300%.

6. The method for restoring the ionic conductivity of a solid electrolyte according to claim 1, characterized in that the contact between the sulfide-based solid electrolyte and the solvent is carried out by mixing the solid electrolyte with the solvent, spraying the solvent onto the solid electrolyte, or immersing the solid electrolyte in the solvent.

7. The method for restoring the ionic conductivity of a solid electrolyte according to claim 1, characterized in that the contact between the sulfide-based solid electrolyte and the solvent is carried out such that the entire surface of the sulfide-based solid electrolyte becomes wet with the solvent.

8. The method for restoring the ionic conductivity of a solid electrolyte according to claim 1, characterized in that the drying is performed under a vacuum atmosphere.

9. The sulfide-based solid electrolyte is Li １０ GeP ２ S １２ 、 Li ２ S-P ２ S ５ glass, thio-LISICONs, Li ９．５４ Si １．７４ P １．４４ S １１．７ Cl ０．３ 、 Li ６ PS ５ X (LPSX; X = Cl, Br, I) argyrodite, and Li １２－ｍ－ｘ ＋ (M ｍ＋ S ４ ２－ )S ２－ｘ ２－ X ｘ － (where M = Si, Ge, Sn, P, As; X = Cl, Br, I; 0 ≦ x ≦ 2), and is one or more selected from the group consisting of, the method for recovering the ionic conductivity of the solid electrolyte according to claim 1.

10. A method for producing a sulfide-based solid electrolyte with restored ionic conductivity, comprising the step of restoring the ionic conductivity of the sulfide-based solid electrolyte by the method according to any one of claims 1 to 9.

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