Solid electrolyte and method for producing the same

Abstract

The object of the present invention is to provide a solid electrolyte with excellent electrical conductivity and ionic conductivity, and a method for producing the same. [Solution] The present invention relates to a solid electrolyte and a method for producing the same, and more specifically, by including a mixed conductive polymer having the properties of ionic conductivity and electrical conductivity and a lithium salt in an appropriate content range, the properties of ionic conductivity and electrical conductivity of the solid electrolyte can all be improved.

Description

[Technical Field]

[0001] This application claims priority rights under Korean Patent Application No. 2021-0174993 dated December 8, 2021, and Korean Patent Application No. 2022-0169870 dated December 7, 2022, and all content disclosed in the documents of the said Korean patent applications is incorporated herein by reference.

[0002] This invention relates to a solid electrolyte and a method for producing the same. [Background technology]

[0003] From the perspectives of battery capacity, safety, output, scaling up, and miniaturization, a variety of batteries are currently being researched that can overcome the limitations of lithium-ion secondary batteries.

[0004] In particular, ongoing research is being conducted on metal-air batteries, which have a much larger theoretical capacity compared to current lithium-ion batteries; all-solid batteries, which do not pose an explosion risk in terms of safety; supercapacitors, which offer high output; NaS batteries or RFB (redox flow batteries), which allow for larger sizes; and thin-film batteries, which enable ultra-miniaturization.

[0005] In this context, all-solid-state batteries refer to batteries that replace the liquid electrolyte used in existing lithium-ion secondary batteries with a solid electrolyte. Because they do not use flammable solvents within the battery, they completely eliminate the risk of ignition or explosion due to the decomposition reaction of the electrolyte, thus significantly improving safety. Furthermore, because lithium metal or lithium alloy can be used as the negative electrode material, they have the advantage of dramatically improving the energy density relative to the mass and volume of the battery.

[0006] While all-solid-state batteries offer advantages such as improved safety compared to conventional batteries using liquid electrolytes, it is not easy to simultaneously ensure both the ionic conductivity and electrical conductivity of the solid electrolyte contained in the all-solid-state battery. Therefore, there are limitations to significantly improving the energy density and lifespan of all-solid-state batteries using commercially available solid electrolytes.

[0007] Therefore, there is a need to develop solid electrolytes that possess both the ionic conductivity and electrical conductivity characteristics required for all-solid-state batteries. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] U.S. Patent Publication No. 2021-0050596 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] As a result of conducting multifaceted research to solve the aforementioned problems, the inventors have confirmed that by using a mixed conductive polymer having both ionic conductivity and electrical conductivity properties and a lithium salt, and controlling their content within an appropriate range, it is possible to produce a solid electrolyte with excellent electrical conductivity and ionic conductivity.

[0010] Therefore, the object of the present invention is to provide a solid electrolyte with excellent electrical conductivity and ionic conductivity, and a method for producing the same.

[0011] Another object of the present invention is to provide an all-solid-state battery containing the solid electrolyte. [Means for solving the problem]

[0012] To achieve the above objective, the present invention provides a solid electrolyte comprising a mixed conductive polymer having ionic conductivity and electrical conductivity properties, and a lithium salt.

[0013] The mixed conductive polymer may contain one or more selected from the group consisting of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)), polyacetylene, poly(paraphenylene)), poly(paraphenylene)sulfide, polythiophene, polypyrrole, polyisothianaphtalene, poly(paraphenylene vinylene)), polyaniline, and poly(3,4-ethylenedioxythiophene) (poly(3,4-ethylenedioxythiophene)).

[0014] The lithium salts mentioned above are LiTFSI (Lithium bis(trifluoromethanesulfonyyl)imide), LiFSI (Lithium bis(fluorosulfonyl)imide), LiNO3, LiOH, LiCl, LiBr, LiI, LiClO4, LiBF4, and LiB 10 Cl 10 It may also contain one or more selected from the group consisting of LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiSCN, LiC(CF3SO2)3, (CF3SO2)2NLi, and (FSO2)2NLi.

[0015] The solid electrolyte may contain 100 parts by weight of the mixed conductive polymer and 5 to 300 parts by weight of lithium salt per 100 parts by weight of the mixed conductive polymer.

[0016] The solid electrolyte may contain 100 to 300 parts by weight of a lithium salt with respect to 100 parts by weight of the mixed conductive polymer and 100 parts by weight of the mixed conductive polymer.

[0017] The solid electrolyte may be in a form in which a lithium salt is dissociated and contained inside a mixed conductive polymer matrix.

[0018] The solid electrolyte may be in the form of a solid electrolyte membrane.

[0019] The thickness of the solid electrolyte may be 10 to 60 μm.

[0020] The present invention also provides a method for producing a solid electrolyte, including: (S1) a step of coating a mixed solution obtained by adding a mixed conductive polymer and a lithium salt to a solvent onto a substrate; and (S2) a step of drying the coating layer obtained in the step (S1).

[0021] The coating method may be bar coating, roll coating, spin coating, slit coating, die coating, blade coating, comma coating, slot die coating, lip coating or solution casting.

[0022] The drying may be performed at 300°C or lower.

[0023] The substrate may be stainless steel, polyethylene terephthalate film, polytetrafluoroethylene film, polyethylene film, polypropylene film, polybutene film, polybutadiene film, vinyl chloride copolymer film, polyurethane film, ethylene-vinyl acetate film, ethylene-propylene copolymer film, ethylene-ethyl acrylate copolymer film, ethylene-methyl acrylate copolymer film, or polyimide film.

[0024] The solvent may be one or more selected from the group consisting of dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, xylene, dimethylformamide (N,N-Dimethylformamide, DMF), benzene, tetrahydrofuran (THF), and water.

[0025] The present invention also provides an electrode for an all-solid-state battery having a coating layer containing the solid electrolyte formed on it.

[0026] The electrode may be a positive or negative electrode.

[0027] The present invention also provides an all-solid-state battery including the electrodes. [Effects of the Invention]

[0028] The solid electrolyte according to the present invention comprises a mixed conductive polymer and a lithium salt, and can ensure both electrical conductivity and ionic conductivity.

[0029] Furthermore, the electrical conductivity and ionic conductivity of the solid electrolyte can be adjusted by controlling the content ratio of the mixed conductive polymer and the lithium salt. [Brief explanation of the drawing]

[0030] [Figure 1] This is a schematic diagram illustrating the process of producing a solid electrolyte according to one embodiment of the present invention. [Modes for carrying out the invention]

[0031] The present invention will be described in more detail below to aid in understanding it.

[0032] Terms and words used in this specification and in the claims should not be interpreted restrictively in their usual or dictionary sense, but rather in a sense and concept that is consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors can appropriately define the concepts of terms in order to best describe their invention.

[0033] As used herein, the term "mixed conducting polymer" refers to a polymer that possesses both electrical conductivity and ionic conductivity.

[0034] solid electrolyte This invention relates to solid electrolytes.

[0035] The solid electrolyte according to the present invention comprises a mixed conducting polymer and a lithium salt.

[0036] The solid electrolyte has a form in which lithium salt is dissociated within a matrix formed by a mixed conductive polymer, and the lithium salt exists in a state where its cations and anions are dissociated.

[0037] In the present invention, the mixed conductive polymer has mixed conductive properties that include ionic conductivity and electrical conductivity, and can simultaneously perform the roles of a conductive material that moves electrons and an electrolyte that moves lithium ions.

[0038] The mixed conductive polymer may contain one or more selected from the group consisting of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)), polyacetylene, poly(paraphenylene)), poly(paraphenylene)sulfide, polythiophene, polypyrrole, polyisothianaphtalene, poly(paraphenylene vinylene)), polyaniline, and poly(3,4-ethylenedioxythiophene) (poly(3,4-ethylenedioxythiophene)).

[0039] For example, the mixed conductive polymer may be poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), and in PEDOT:PSS, the weight ratio of PEDOT to PSS may be 1:1 to 4, 1:1.5 to 3.5, 1:2 to 3, or 1:2.5.

[0040] In the present invention, the lithium salt can act as a lithium source that dissociates into a mixed conductive polymer matrix to provide lithium ions.

[0041] The lithium salts mentioned above are LiTFSI (Lithium bis(trifluoromethanesulfonyyl)imide), LiFSI (Lithium bis(fluorosulfonyl)imide), LiNO3, LiOH, LiCl, LiBr, LiI, LiClO4, LiBF4, and LiB 10 Cl 10It may also contain one or more selected from the group consisting of LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiSCN, LiC(CF3SO2)3, (CF3SO2)2NLi, and (FSO2)2NLi.

[0042] Furthermore, the lithium salt may be included in an amount of 5 to 300 parts by weight per 100 parts by weight of the mixed conductive polymer. Specifically, the content of the lithium salt may be 5 parts by weight or more, 10 parts by weight or more, 20 parts by weight or more, 30 parts by weight or more, 40 parts by weight or more, 50 parts by weight or more, 70 parts by weight or more, or 100 parts by weight or more, and may be 120 parts by weight or less, 130 parts by weight or less, 140 parts by weight or less, 150 parts by weight or less, 200 parts by weight or less, 250 parts by weight or less, or 300 parts by weight or less. If the content of the lithium salt is less than 5 parts by weight, the lithium source may be small and the ionic conductivity may decrease significantly, and if it exceeds 300 parts by weight, excess lithium salt that has not been dissociated in the mixed conductive polymer may precipitate and the ionic conductivity may decrease.

[0043] In the present invention, the solid electrolyte may be used as an electrolyte in an all-solid-state battery in the form of a solid electrolyte membrane, or it may be applied to an electrode. When the solid electrolyte is applied to an electrode, it may be formed on or inside the active material layer of the positive or negative electrode.

[0044] In the present invention, the thickness of the solid electrolyte may be 10 to 60 μm. Specifically, the thickness of the solid electrolyte may be 10 μm or more, 15 μm or more, or 20 μm or more, and may be 40 μm or less, 50 μm or less, or 60 μm or less. If the thickness of the solid electrolyte is less than 10 μm, the strength may be weaker, and if it exceeds 60 μm, the energy density may decrease.

[0045] Method for producing solid electrolytes The present invention also relates to a method for producing a solid electrolyte, the method for producing the solid electrolyte comprising: (S1) a step of coating a substrate with a mixed solution obtained by adding a mixed conductive polymer and a lithium salt to a solvent; and (S2) a step of drying the coating layer obtained in step (S1).

[0046] The method for producing a solid electrolyte according to the present invention will be described in more detail below, step by step.

[0047] In the present invention, in step (S1), a mixed solution containing a mixed conductive polymer and a lithium salt can be coated onto a substrate. The types and contents of the mixed conductive polymer and lithium salt are as described above.

[0048] Figure 1 is a schematic diagram showing the process of forming a coating layer on a substrate according to one embodiment of the present invention.

[0049] Referring to Figure 1, a polymer solution can be obtained by dissolving a mixed conductive polymer in a solvent to produce a polymer solution, and then mixing it with a lithium salt (Li salt) to obtain a polymer / Li salt solution.

[0050] The mixing can be carried out until the mixed solution appears uniform to the naked eye. For example, the mixing can be carried out for 8 to 16 hours, and specifically, the mixing time may be 8 hours or more, 9 hours or more, or 10 hours or more, or 14 hours or less, 15 hours or less, or 16 hours or less. If the mixing time is less than 8 hours, the mixed solution will not become uniform, and if it exceeds 16 hours, even if the mixing time increases, there will not be a significant change in the uniformity of the first mixed solution, which may reduce efficiency in terms of process performance.

[0051] Furthermore, the solvent is not particularly limited as long as it is a solvent that can dissolve and / or disperse the mixed conductive polymer and lithium salt to form a solution. For example, the solvent may be one or more selected from the group consisting of dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, xylene, dimethylformamide (N,N-Dimethylformamide, DMF), benzene, tetrahydrofuran (THF), and water. The amount of solvent used can be adjusted considering the thickness of the coating layer, the physical properties of the solid electrolyte produced, and so on.

[0052] Furthermore, the concentration of the mixed solution is not particularly limited as long as it is sufficient to carry out the coating process. For example, the concentration of the mixed solution may be 0.5% to 30%, specifically 0.5% or more, 1% or more, or 3% or more, or 10% or less, 20% or less, or 30% or less. If the concentration of the mixed solution is less than 0.5%, the resulting coating layer will be too thin, and if it exceeds 30%, it may be difficult to form a uniform coating layer.

[0053] The coating method may be bar coating, roll coating, spin coating, slit coating, die coating, blade coating, comma coating, slot die coating, lip coating, or solution casting, but is not limited to any coating method that can form a coating layer on the substrate.

[0054] Furthermore, the substrate is not particularly limited as long as it is a substrate that can be used to form a coating layer. For example, the substrate may be stainless steel, polyethylene terephthalate film, polytetrafluoroethylene film, polyethylene film, polypropylene film, polybutene film, polybutadiene film, vinyl chloride copolymer film, polyurethane film, ethylene-vinyl acetate film, ethylene-propylene copolymer film, ethylene-ethyl acrylate copolymer film, ethylene-methyl acrylate copolymer film, or polyimide film.

[0055] In the present invention, in step (S2), the coating layer obtained in step (S1) can be dried.

[0056] The drying method is not particularly limited as long as it can evaporate the solvent contained in the coating layer and form a film (layer). For example, the drying may be carried out at 300°C or below. Specifically, the drying temperature may be 300°C or below, 200°C or below, 150°C or below, or 100°C or below. The drying temperature may also vary depending on the type of solvent and the drying conditions. For example, in the case of vacuum drying, it can be carried out at 100°C or below. Also, if the solvent is acetone or alcohol, it can be carried out at 100°C or below. If the drying temperature exceeds 300°C, the solid electrolyte may be thermally decomposed. The lower limit of the drying temperature is not particularly limited, but it may be, for example, 60°C or above.

[0057] In the present invention, after step (S2), step (S3) can be further carried out, in which, after drying in step (S2), the coating layer can be separated from the substrate to obtain a solid electrolyte.

[0058] Electrodes for all-solid-state batteries and all-solid-state batteries containing the same The present invention also relates to an electrode for an all-solid-state battery having a coating layer containing the solid electrolyte. The electrode is a positive electrode or a negative electrode.

[0059] In the present invention, the positive electrode may include a positive electrode active material layer and a coating layer containing the solid electrolyte formed on one surface of the positive electrode active material layer. The coating layer may be formed by attaching a solid electrolyte produced by the manufacturing method as described above to the positive electrode active material layer, or may be formed by a coating method commonly used in the art. For example, the coating method may be a spin method, a dipping method, a spray method, a roll coating method, a gravure printing method, a bar coating method, a die coating method, a comma coating method, or a mixed method thereof. The coating layer containing the solid electrolyte may be in the form of a solid electrolyte membrane.

[0060] Also, a positive electrode current collector may be further formed on the other surface of the positive electrode active material layer. At this time, the positive electrode current collector and the positive electrode active material are not particularly limited as long as they are commonly used in all-solid-state batteries.

[0061] The positive electrode active material layer includes a positive electrode active material, a binder, and a conductive material.

[0062] Also, the positive electrode active material is not particularly limited as long as it can reversibly occlude and release lithium ions. For example, lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), Li[Ni x Co y Mn z M v O2 (in the above formula, M is any one selected from the group consisting of Al, Ga, and In or two or more elements thereof; 0.3 ≦ x < 1.0, 0 ≦ y, z ≦ 0.5, 0 ≦ v ≦ 0.1, and x + y + z + v = 1), Li(Li a M b-a-b' M'b' )O 2-c A c Layered compounds such as (wherein the above formula, 0≦a≦0.2, 0.6≦b≦1, 0≦b'≦0.2, 0≦c≦0.2; M comprises Mn and one or more elements selected from the group consisting of Ni, Co, Fe, Cr, V, Cu, Zn, and Ti; M' is one or more elements selected from the group consisting of Al, Mg, and B, and A is one or more elements selected from the group consisting of P, F, S, and N), or compounds substituted with one or more transition metals; chemical formula Li 1+y Mn 2-y Lithium manganese oxides such as O4 (where y is 0 or 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-y Ni-site type lithium nickel oxide represented as MyO2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and y is 0.01 to 0.3); chemical formula LiMn 2-y M y Lithium manganese composite oxides represented as O2 (where M is Co, Ni, Fe, Cr, Zn, or Ta, and y is 0.01 to 0.1) or Li2Mn3MO8 (where M is Fe, Co, Ni, Cu, or Zn); LiMn2O4 in which part of the Li in the chemical formula is replaced with an alkaline earth metal ion; disulfide compounds; Fe2(MoO4)3, etc. are examples, but are not limited to these.

[0063] Furthermore, the positive electrode active material may be included in an amount of 40 to 80% by weight based on the total weight of the positive electrode active material layer. Specifically, the content of the positive electrode active material may be 40% or more by weight or 50% or more by weight, or 70% or less by weight or 80% or less by weight. If the content of the positive electrode active material is less than 40% by weight, the battery performance may decrease, and if it exceeds 80% by weight, the mass transfer resistance may increase.

[0064] Furthermore, the binder contains components that assist in the bonding of the positive electrode active material to conductive materials and to the current collector, such as styrene-butadiene rubber, acrylic styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile-butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphagen, and polyacrylic. The binder may include one or more selected from the group consisting of polynitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethylcellulose, hydroxypropylcellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethylsucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene. Preferably, the binder may include one or more selected from the group consisting of styrene-butadiene rubber, polytetrafluoroethylene, carboxymethylcellulose, polyacrylic acid, lithium polyacrylate, and polyvinylidene fluoride.

[0065] Furthermore, the binder may be included in an amount of 1% to 30% by weight based on the total weight of the positive electrode active material layer. Specifically, the binder content may be 1% or more by weight, 3% or more by weight, 15% or less by weight, or 30% or less by weight. If the binder content is less than 1% by weight, the adhesive strength between the positive electrode active material and the positive electrode current collector may decrease. If it exceeds 30% by weight, the adhesive strength will improve, but the content of the positive electrode active material will decrease accordingly, which may result in a lower battery capacity.

[0066] Furthermore, the conductive material is not particularly limited as long as it prevents side reactions in the internal environment of the all-solid-state battery and has excellent electrical conductivity without causing chemical changes to the battery. Typically, graphite or conductive carbon can be used, for example, graphite such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, Denka black, thermal black, channel black, furnace black, lamp black, and thermal black; carbon-based materials whose crystalline structure is graphene or graphite; conductive fibers such as carbon fibers and metal fibers; carbon fluoride; metal powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives; can be used alone or in mixtures of two or more, but are not necessarily limited to these.

[0067] The conductive material can typically be included in an amount of 0.5% to 30% by weight based on the total weight of the positive electrode active material layer. Specifically, the content of the conductive material may be 0.5% or more by weight, or 1% or more by weight, or 20% or less by weight, or 30% or less by weight. If the content of the conductive material is too low (less than 0.5% by weight), it may be difficult to expect an improvement in electrical conductivity, or the electrochemical properties of the battery may deteriorate. If it is too high (more than 30% by weight), the amount of positive electrode active material will be relatively small, which may reduce the capacity and energy density. The method for incorporating the conductive material into the positive electrode is not particularly limited, and conventional methods known in the art, such as coating the positive electrode active material, can be used.

[0068] Furthermore, the positive electrode current collector supports the positive electrode active material layer and plays a role in transferring electrons between the external conductor and the positive electrode active material layer.

[0069] The positive electrode current collector is not particularly limited as long as it has high electronic conductivity without causing chemical changes to the all-solid-state battery. For example, copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, silver, etc., and aluminum-cadmium alloys can be used as the positive electrode current collector.

[0070] The positive electrode current collector may have a fine uneven surface or a three-dimensional porous structure to strengthen the bonding force with the positive electrode active material layer. This allows the positive electrode current collector to take on a variety of forms, such as film, sheet, foil, mesh, net, porous material, foam, or nonwoven fabric.

[0071] The positive electrode described above can be manufactured by conventional methods. Specifically, it can be manufactured by mixing a positive electrode active material, a conductive material, and a binder in an organic solvent to produce a composition for forming a positive electrode active material layer, which is then coated onto a positive electrode current collector and dried, and then selectively compress-molded onto the current collector to improve electrode density. In this case, it is preferable to use an organic solvent that can uniformly disperse the positive electrode active material, binder, and conductive material and that evaporates easily. Specifically, examples include acetonitrile, methanol, ethanol, tetrahydrofuran, water, and isopropyl alcohol.

[0072] In the present invention, the negative electrode may include a negative electrode active material layer and a coating layer containing the solid electrolyte formed on one surface of the negative electrode active material layer. The method for forming the coating layer is the same as the method for forming the coating layer on the positive electrode.

[0073] Furthermore, a negative electrode current collector may be formed on another surface of the negative electrode active material layer. In this case, the negative electrode current collector and the negative electrode active material are not particularly limited as long as they are those commonly used in all-solid-state batteries.

[0074] The negative electrode active material layer comprises a negative electrode active material, a binder, and a conductive material.

[0075] The aforementioned negative electrode active material is lithium (Li + This may include materials that can be reversibly intercalated or deintercalated, materials that can react with lithium ions to reversibly form lithium-containing compounds, lithium metals, or lithium alloys.

[0076] The aforementioned lithium ion (Li + The material that can reversibly insert or remove lithium ions (Li) may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. + A substance that can reversibly form a lithium-containing compound by reacting with ) may be, for example, tin oxide, titanium nitride, or silicone. The lithium alloy may be, for example, an alloy of lithium (Li) and a metal selected from the group consisting of sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al), and tin (Sn).

[0077] Preferably, the negative electrode active material may be a lithium metal, and specifically, it may be in the form of a lithium metal thin film or lithium metal powder.

[0078] The negative electrode active material may be included in an amount of 40 to 80% by weight based on the total weight of the negative electrode active material layer. Specifically, the content of the negative electrode active material may be 40% or more by weight, 50% or more by weight, or 70% or less by weight, or 80% or less by weight. If the content of the negative electrode active material is less than 40% by weight, the battery performance may decrease, and if it exceeds 80% by weight, the mass transfer resistance may increase.

[0079] Furthermore, the binder is as described above in the positive electrode active material layer.

[0080] Furthermore, the conductive material is as described above in the positive electrode active material layer.

[0081] Furthermore, the negative electrode current collector is not particularly limited as long as it is conductive without causing a chemical change in the battery. For example, the negative electrode current collector can be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloy. Also, like the positive electrode current collector, the negative electrode current collector can be made of various forms such as films, sheets, foils, nets, porous materials, foams, or nonwoven fabrics with fine irregularities formed on their surface.

[0082] The method for manufacturing the negative electrode is not particularly limited, and it can be manufactured by forming a negative electrode active material layer on a negative electrode current collector using methods for forming layers or films commonly used in the industry. For example, methods such as compression, coating, and vapor deposition can be used. Furthermore, the negative electrode of the present invention is also included in cases where a metallic lithium thin film is formed on a sheet metal by initial charging after the battery has been assembled without a lithium thin film on the negative electrode current collector.

[0083] The present invention also relates to an all-solid-state battery, including electrodes for the all-solid-state battery.

[0084] One or more of the positive and negative electrodes in the all-solid-state battery may have a coating layer formed on it that contains the solid electrolyte described above.

[0085] Since the solid electrolyte exhibits excellent ionic conductivity and electrical conductivity, applying it to an all-solid-state battery in the form of a coating layer formed on the positive and / or negative electrodes can improve the performance and lifespan characteristics of the all-solid-state battery.

[0086] The following are preferred embodiments to aid in understanding the present invention. However, these embodiments are merely illustrative of the present invention, and it will be obvious to those skilled in the art that various changes and modifications are possible within the scope of the present invention and the technical concept, and that such changes and modifications will naturally fall within the scope of the appended claims.

[0087] In the following examples and comparative examples, solid electrolytes were prepared according to the weight ratios of the mixed conductive polymer and lithium salt as shown in Table 1 below.

[0088] [Table 1]

[0089] Example 1 A mixed solution was obtained by thoroughly stirring 5 g of a solution of the mixed conductive polymer PEDOT:PSS (Sigma-Aldrich, 1.1 wt%) and 0.11 g of the lithium salt LiTFSI for 12 hours to obtain a mixed solution. This solution was then coated onto stainless steel foil using a doctor blade to form a coating layer. The weight ratio of the mixed conductive polymer to the lithium salt ((PEDOT:PSS):LiTFSI) was 5:1. The weight ratio of PEDOT to PSS was 1:2.5.

[0090] Subsequently, the mixture was vacuum-dried at 100°C for one day to remove the solvent from the mixed solution and produce a solid electrolyte membrane.

[0091] Example 2 A solid electrolyte membrane was manufactured in the same manner as in Example 1, except that the weight ratio of the mixed conductive polymer to the lithium salt ((PEDOT:PSS):LiTFSI) was set to 1:1.

[0092] Example 3 A solid electrolyte membrane was manufactured in the same manner as in Example 1, except that the weight ratio of the mixed conductive polymer to the lithium salt ((PEDOT:PSS):LiTFSI) was set to 1:2.

[0093] Example 4 A solid electrolyte membrane was manufactured in the same manner as in Example 1, except that LiNO3 was used as the lithium salt and the weight ratio of the mixed conductive polymer to the lithium salt ((PEDOT:PSS):LiNO3) was set to 5:1.

[0094] Example 5 A solid electrolyte membrane was manufactured in the same manner as in Example 1, except that LiOH was used as the lithium salt and the weight ratio of the mixed conductive polymer to the lithium salt ((PEDOT:PSS):LiOH) was set to 5:1.

[0095] Example 6 A solid electrolyte membrane was fabricated in the same manner as in Example 1, except that LiFSI was used as the lithium salt and the weight ratio of the mixed conductive polymer to the lithium salt ((PEDOT:PSS):LiFSI) was set to 1:2.

[0096] Example 7 A solid electrolyte membrane was manufactured in the same manner as in Example 1, except that polypyrrole was used as the polymer and the weight ratio of the mixed conductive polymer to the lithium salt (polypyrrole:LiTFSI) was set to 2:1.

[0097] Example 8 A solid electrolyte membrane was manufactured in the same manner as in Example 1, except that polypyrrole was used as the polymer and the weight ratio of the polymer to the lithium salt (polypyrrole: LiTFSI) was set to 1:2.

[0098] Example 9 A solid electrolyte membrane was manufactured in the same manner as in Example 1, except that the weight ratio of polymer to lithium salt ((PEDOT:PSS):LiTFSI) was set to 1:3.

[0099] Example 10 A solid electrolyte membrane was manufactured in the same manner as in Example 1, except that the weight ratio of polymer to lithium salt ((PEDOT:PSS):LiTFSI) was set to 10:1.

[0100] Comparative Example 1 A solid electrolyte membrane was manufactured in the same manner as in Example 1, except that PEO was used as the polymer.

[0101] Comparative Example 2 A solid electrolyte membrane was manufactured in the same manner as in Example 1, except that lithium salts were not used.

[0102] Comparative Example 3 A solid electrolyte membrane was manufactured in the same manner as in Example 1, except that the weight ratio of the polymer to the lithium salt ((PEDOT:PSS and PEO):LiTFSI) was set to 1:1. In this case, (PEDOT:PSS):PEO was a mixed polymer mixed in a weight ratio of 7:3.

[0103] Experimental Example 1: Evaluation of the physical properties of solid electrolytes The solid electrolyte membranes produced in the examples and comparative examples were subjected to tests for ionic conductivity and electrical conductivity as described below, and the results are shown in Table 2.

[0104] (1) Ionic conductivity After forming a coin cell by contacting the solid electrolyte membrane with a stainless steel plate, an AC voltage was applied at room temperature. The measurement frequency was set to an amplitude range of 500 kHz to 20 MHz under the applied conditions, and the impedance was measured using a BioLogic VMP3. Using Equation 1 below, the resistance of the solid electrolyte membrane was determined from the intersection points (Rb) where the semicircles and straight lines of the measured impedance trajectories meet the real axis, and the ionic conductivity (σ) of the solid electrolyte membrane was calculated from the sample width and thickness.

[0105] [Formula 1]

number

[0106] (2) Electrical conductivity (S) Cyclic voltammetry (-0.1V to 0.1V) was performed on coin cells fabricated with the same structure as those used in the aforementioned ionic conductivity measurement, and the electrical conductivity (S, S / cm) was calculated using the following equation 2.

[0107] [Formula 2] S=A / V × Film thickness / film dimension A: Current V: Voltage Film thickness: Sample thickness Film dimension: Sample size

[0108] [Table 2]

[0109] As shown in Table 2 above, as in Examples 1 to 10, solid electrolyte membranes containing a mixed conductive polymer and a lithium salt in an appropriate weight ratio exhibit excellent ionic conductivity and electrical conductivity.

[0110] Furthermore, as can be seen in Examples 1 to 3, when using the same mixed conductive polymer and lithium salt, it can be observed that both ionic conductivity and electrical conductivity increase together as the lithium salt content increases.

[0111] However, as can be seen in Example 9, if the lithium salt content increases excessively compared to the mixed conductive polymer, the ionic conductivity and electrical conductivity actually decrease.

[0112] Furthermore, as can be seen in Example 10, even if the content of the mixed conductive polymer increases excessively compared to the lithium salt, the ionic conductivity and electrical conductivity decrease.

[0113] Furthermore, as shown in Comparative Example 1, it can be seen that using an excessive amount of PEO instead of a mixed conductive polymer significantly reduces both ionic and electrical conductivity.

[0114] Furthermore, as in Comparative Example 2, it was impossible to measure ionic conductivity without using a lithium salt.

[0115] Furthermore, as in Comparative Example 3, when a mixed conductive polymer and PEO are used together, both ionic conductivity and electrical conductivity are found to decrease.

[0116] Although the present invention has been described above, even with limited embodiments and drawings, the present invention is not limited thereto, and of course, various modifications and variations are possible within the equivalent scope of the technical concept of the present invention and the following claims by persons with ordinary skill in the art to which the present invention pertains.

Claims

1. A solid electrolyte containing a mixed conductive polymer having ionic conductivity and electrical conductivity properties, and a lithium salt.

2. The aforementioned mixed conductive polymer is poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)), polyacetylene, poly(paraphenylene), poly(paraphenylene) sulfide, polythiophene, polypyrrole, polyisocyanaphthalene, poly(paraphenylene) vinylene The solid electrolyte according to claim 1, comprising one or more selected from the group consisting of vinylene, polyaniline, and poly(3,4-ethylenedioxythiophene).

3. The lithium salt is one or more selected from the group consisting of LiTFSI (Lithium bis(trifluoromethanesulfonyl)imide), LiFSI (Lithium bis(fluorosulfonyl)imide), LiNO ３ , LiOH, LiCl, LiBr, LiI, LiClO ４ , LiBF ４ , LiB １０ Cl １０ , LiPF ６ , LiCF ３ SO ３ , LiCF ３ CO ２ , LiAsF ６ , LiSbF ６ , LiAlCl ４ , CH ３ SO ３ Li, CF ３ SO ３ Li, LiSCN, LiC(CF ３ SO ２ ) ３ , (CF ３ SO ２ ) ２ NLi and (FSO ２ ) ２ NLi, and the solid electrolyte according to claim 1, which contains one or more selected from the group consisting of

4. The solid electrolyte according to claim 1, wherein the solid electrolyte comprises 100 parts by weight of the mixed conductive polymer and 5 to 300 parts by weight of lithium salt per 100 parts by weight of the mixed conductive polymer.

5. The solid electrolyte according to claim 1, wherein the solid electrolyte comprises 100 parts by weight of the mixed conductive polymer and 100 to 300 parts by weight of lithium salt per 100 parts by weight of the mixed conductive polymer.

6. The solid electrolyte according to claim 1, wherein the solid electrolyte is in a form in which a lithium salt is dissociated and contained within a mixed conductive polymer matrix.

7. The solid electrolyte according to claim 1, wherein the solid electrolyte is in the form of a solid electrolyte membrane.

8. The solid electrolyte according to claim 1, wherein the thickness of the solid electrolyte is 10 to 60 μm.

9. (S1) A step of coating a substrate with a mixed solution obtained by adding a mixed conductive polymer and a lithium salt to a solvent; and A method for producing a solid electrolyte, comprising the step of (S2) drying the coating layer obtained in step (S1);

10. The method for producing a solid electrolyte according to claim 9, wherein the coating method is bar coating, roll coating, spin coating, slit coating, die coating, blade coating, comma coating, slot die coating, lip coating, or solution casting.

11. The method for producing a solid electrolyte according to claim 9, wherein the drying is performed at 300°C or below.

12. The method for producing a solid electrolyte according to claim 9, wherein the substrate is stainless steel, polyethylene terephthalate film, polytetrafluoroethylene film, polyethylene film, polypropylene film, polybutene film, polybutadiene film, vinyl chloride copolymer film, polyurethane film, ethylene-vinyl acetate film, ethylene-propylene copolymer film, ethylene-ethyl acrylate copolymer film, ethylene-methyl acrylate copolymer film, or polyimide film.

13. The method for producing a solid electrolyte according to claim 9, wherein the solvent is one or more selected from the group consisting of dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, xylene, dimethylformamide (N,N-dimethylformamide, DMF), benzene, tetrahydrofuran (THF), and water.

14. An electrode for an all-solid-state battery having a coating layer formed on which the solid electrolyte described in claim 1 is contained.

15. The electrode according to claim 14, wherein the electrode for the all-solid-state battery is either a positive electrode or a negative electrode.

16. A solid-state battery comprising the electrode described in claim 15.

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