KR20230086620A - Solid electrolyte and method for preparing the same - Google Patents

Abstract

The present invention relates to a solid electrolyte and a method for manufacturing the same, and more particularly, the solid electrolyte includes a mixed conductive polymer having ion conductivity and electrical conductivity and an inorganic material to enhance adhesion and strength, thereby reducing interfacial resistance. reduced to improve ionic conductivity and electrical conductivity.

Description

Solid electrolyte and its manufacturing method {SOLID ELECTROLYTE AND METHOD FOR PREPARING THE SAME}

The present invention relates to a solid electrolyte and a method for preparing the same.

Various batteries capable of overcoming the limitations of current lithium secondary batteries are being studied in terms of battery capacity, safety, output, large size, and miniaturization.

Representatively, metal-air batteries with a very large theoretical capacity in terms of capacity compared to current lithium secondary batteries, all solid batteries with no risk of explosion in terms of safety, and supercapacitors in terms of output ( Supercapacitor), NaS battery or RFB (redox flow battery) in terms of large size, and thin film battery in terms of miniaturization, continuous research is being conducted.

Among them, the all-solid-state battery refers to a battery in which the liquid electrolyte used in conventional lithium secondary batteries is replaced with a solid electrolyte, and since it does not use a flammable solvent in the battery, ignition or explosion due to the decomposition reaction of the conventional electrolyte does not occur at all. Safety can be greatly improved. In addition, since Li metal or Li alloy can be used as a negative electrode material, there is an advantage in that the energy density for the mass and volume of the battery can be dramatically improved.

As such, the all-solid-state battery has the advantage of improved safety compared to a battery using a conventional liquid electrolyte, but it is not easy to simultaneously secure the ion conductivity and electrical conductivity of the solid electrolyte included in the all-solid-state battery, which is a commercially available solid electrolyte There is a limit to significantly improving the energy density and lifespan of an all-solid-state battery.

In particular, there is a problem in that ionic conductivity and electrical conductivity are slightly lowered due to the interfacial resistance of the solid electrolyte.

Therefore, it is necessary to develop a technology capable of improving ion conductivity and electrical conductivity by reducing the interfacial resistance of the solid electrolyte.

Korean Patent Publication No. 2019-0086775

As a result of various studies to solve the above problems, the inventors of the present invention use mixed conductive polymers, inorganic materials, and lithium salts having ionic conductivity and electrical conductivity characteristics and control them to an appropriate content range, thereby improving electrical conductivity and ionic conductivity. It was confirmed that all excellent solid electrolytes could be prepared.

Accordingly, an object of the present invention is to provide a solid electrolyte having excellent electrical conductivity and ionic conductivity and a method for preparing the same.

Another object of the present invention is to provide an all-solid-state battery including the solid electrolyte.

In order to achieve the above object, the present invention provides a solid electrolyte including a mixed conductive polymer having ion conductivity and electrical conductivity, an inorganic material, and a lithium salt.

The mixed conductive polymer is poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS, poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)), polyacetylene, polyacetylene poly(paraphenylene), poly(paraphenylene) sulfide, polythiophene, polypyrrole, polyisothianaphtalene, polyparaphenylenevinylene (paraphenylene vinylene)), polyaniline (polyaniline) and poly (3,4-ethylenedioxythiophene) (poly (3,4-ethylenedioxythiophene)).

The inorganic material may include at least one selected from the group consisting of oxide-based inorganic materials, nitride-based inorganic materials, and carbide-based inorganic materials.

The oxide-based inorganic material is TiO ₂ , ZnO ₂ , ZnO, SrTiO ₃ , ZrPO ₄ , BaTiO ₃ , KNbO ₃ , Fe ₂ O ₃ , Ta ₂ O ₅ , WO ₃ , SnO ₂ , Bi ₂ O ₃ , NiO, Cu ₂ At least one selected from the group consisting of O, SiO, SiO ₂ , MoS ₂ , RuO ₂ and CeO ₂ ,

The nitride-based inorganic material includes at least one selected from the group consisting of AIN (Aluminium Nitride), BN (Boron Nitride), and Si ₂ N ₄ (Silicon Nitride),

The carbide-based inorganic material may include one or more selected from the group consisting of CuC, AgC, and AuC.

The lithium salt is LiTFSI (Lithium bis(trifluoromethanesulphonyl)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 It may include one or more selected from the group consisting of NLi.

The solid electrolyte may include 100 parts by weight of the mixed conductive polymer, 2 to 30 parts by weight of an inorganic material, and 5 to 300 parts by weight of a lithium salt based on 100 parts by weight of the mixed conductive polymer.

The solid electrolyte may include 100 parts by weight of the mixed conductive polymer, 2 to 30 parts by weight of a binder, and 100 to 300 parts by weight of a lithium salt based on 100 parts by weight of the mixed conductive polymer.

The solid electrolyte may be a form in which lithium salt is dissociated and included in a mixed conductive polymer matrix including a mixed conductive polymer and an inorganic material.

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

The solid electrolyte may have a thickness of 10 to 60 μm.

The present invention also includes (S1) coating a mixed solution obtained by adding a mixed conductive polymer, an inorganic material, and a lithium salt to a solvent on a substrate; and (S2) drying the coating layer obtained in step (S1).

The coating method includes bar coating, roll coating, spin coating, slit coating, die coating, blade coating, and comma coating. coating), slot die coating, lip coating, or solution casting.

The drying may be performed at 300° C. or less.

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 It may be an acetate film, an ethylene-propylene copolymer film, an ethylene-ethyl acrylate copolymer film, an ethylene-methyl acrylate copolymer film, or a polyimide film.

The solvent is dimethylsulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, xylene, dimethylformamide (N,N-Dimethylmethanamide , DMF), benzene (benzene), tetrahydrofuran (tetrahydrofuran, THF), and may be one or more selected from the group consisting of water.

The present invention also provides an electrode for an all-solid-state battery having a coating layer containing the solid electrolyte.

The electrode may be an anode or a cathode.

The present invention also provides an all-solid-state battery including the electrode.

The solid electrolyte according to the present invention has an effect of improving adhesion and strength due to the inorganic material, thereby reducing interfacial resistance, and thereby improving ionic conductivity and electrical conductivity.

In addition, the solid electrolyte may secure both ion conductivity and electrical conductivity by including a mixed conductive polymer and a lithium salt.

In addition, the ion conductivity and electrical conductivity of the solid electrolyte may be adjusted by controlling the content ratio of the mixed conductive polymer and the lithium salt.

1 is a schematic diagram showing a process of manufacturing a solid electrolyte according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail to aid understanding of the present invention.

Terms or words used in this specification and claims should not be construed as being limited to ordinary or dictionary meanings, and the inventor may appropriately define the concept of terms in order to explain his or her invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

solid electrolyte

The present invention relates to solid electrolytes.

The solid electrolyte according to the present invention includes a mixed conducting polymer, an inorganic material, and a lithium salt. The solid electrolyte may be a polymer solid electrolyte.

The solid electrolyte according to the present invention can improve electrical conductivity and ionic conductivity as the interfacial resistance is reduced by enhancing adhesion and strength by the inorganic material.

The solid electrolyte has a form in which a lithium salt is dissociated in a mixed conductive polymer matrix including a mixed conductive polymer and a binder, and cations and anions of the lithium salt exist in a dissociated state.

In the present invention, the mixed conducting polymer has mixed conducting characteristics including ionic conducting and electronic conducting characteristics, and serves as a conductive material for moving electrons and moving lithium ions. It can simultaneously act as an electrolyte.

The mixed conductive polymer is poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS, poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)), polyacetylene, polyacetylene poly(paraphenylene), poly(paraphenylene) sulfide, polythiophene, polypyrrole, polyisothianaphtalene, polyparaphenylenevinylene (paraphenylene vinylene)), polyaniline (polyaniline) and poly (3,4-ethylenedioxythiophene) (poly (3,4-ethylenedioxythiophene)).

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

In the present invention, the inorganic material may improve ionic conductivity and electrical conductivity by reducing interfacial resistance by improving adhesion and strength of the solid electrolyte.

The inorganic material may include, for example, at least one selected from the group consisting of oxide-based inorganic materials, nitride-based inorganic materials, and carbide-based inorganic materials.

The oxide-based inorganic material is TiO ₂ , ZnO ₂ , ZnO, SrTiO ₃ , ZrPO ₄ , BaTiO ₃ , KNbO ₃ , Fe ₂ O ₃ , Ta ₂ O ₅ , WO ₃ , SnO ₂ , Bi ₂ O ₃ , NiO, Cu ₂ It may include one or more selected from the group consisting of O, SiO, SiO ₂ , MoS ₂ , RuO ₂ and CeO ₂ .

The nitride-based inorganic material may include one or more selected from the group consisting of AIN (Aluminium Nitride), BN (Boron Nitride), and Si ₂ N ₄ (Silicon Nitride).

The carbide-based inorganic material may include at least one selected from the group consisting of CuC, AgC, and AuC.

In addition, the inorganic material may be included in an amount of 2 to 30 parts by weight based on 100 parts by weight of the mixed conductive polymer. Specifically, the content of the inorganic material may be 2 parts by weight or more, 3 parts by weight or more, 4 parts by weight or more, 5 parts by weight or more, 7 parts by weight or more, or 10 parts by weight or more, 15 parts by weight or less, 20 parts by weight or less, 25 parts by weight or less or 30 parts by weight or less. If the content of the inorganic material is less than 2 parts by weight, the degree of improvement in the adhesion and strength of the solid electrolyte is insignificant, and the effect of reducing interface resistance may not be good, and if it exceeds 30 parts by weight, it is difficult to disperse the inorganic particles in the polymer. Since is agglomerated, a uniform solid electrolyte membrane is not generated, and rather, ion conductivity and electrical conductivity may be lowered.

In the present invention, the lithium salt may serve as a lithium source allowing lithium ions to exist by dissociating in the mixed conductive polymer matrix.

The lithium salt is LiTFSI (Lithium bis(trifluoromethanesulphonyl)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 It may include one or more selected from the group consisting of NLi.

In addition, the lithium salt may be included in an amount of 5 to 300 parts by weight based on 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, , 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 ionic conductivity may be significantly reduced due to a small amount of lithium source, and if the content is greater than 300 parts by weight, the ion conductivity may decrease due to precipitation of excess lithium salt that has not been dissociated from the mixed conductive polymer. .

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

In the present invention, the solid electrolyte may have a thickness of 10 to 60 μm. Specifically, the solid electrolyte may have a thickness of 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. When the thickness of the solid electrolyte is less than 10 μm, strength may be weakened, and when the thickness is greater than 60 μm, energy density may be reduced.

Manufacturing method of solid electrolyte

The present invention also relates to a method for producing a solid electrolyte, which includes (S1) coating a mixed solution obtained by adding a mixed conductive polymer, an inorganic material, and a lithium salt to a solvent on a substrate; and (S2) drying the coating layer obtained in step (S1).

Hereinafter, the manufacturing method of the solid electrolyte according to the present invention for each step will be described in more detail.

In the present invention, in the step (S1), a mixed solution obtained by adding a mixed conductive polymer, an inorganic material, and a lithium salt to a solvent may be coated on the substrate. The types and contents of the mixed conductive polymer, inorganic material, and lithium salt are as described above.

1 is a schematic diagram showing a process of forming a coating layer for manufacturing a solid electrolyte film on a substrate according to an embodiment of the present invention.

Referring to FIG. 1, after preparing a mixed conductive polymer solution by dissolving a mixed conductive polymer in a solvent, a first mixed solution may be obtained by mixing a lithium salt (Polymer/Li salt solution). ).

The mixing may be performed until the first mixed solution is uniformly visible to the naked eye. For example, the mixing may be performed for 8 to 16 hours, specifically, the mixing time may be 8 hours or more, 9 hours or more, or 10 hours or more, and may be 14 hours or less, 15 hours or less, or 16 hours or less. there is. If the mixing time is less than 8 hours, the first mixed solution cannot be made uniform, and if the mixing time exceeds 16 hours, even if the mixing time is increased, there is no significant change in the uniformity of the first mixed solution, so the efficiency can be reduced in terms of fairness. there is.

Thereafter, an inorganic material (ceramic) is mixed with the first mixed solution (Polymer/Li salt solution) to obtain a second mixed solution (Polymer/Li salt/Ceramic solution), and then coated on the substrate.

The solvent is not particularly limited as long as it dissolves and/or disperses the mixed conductive polymer, inorganic material, and lithium salt to form a solution. For example, the solvent may be dimethylsulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, xylene, dimethylformamide (N , N-Dimethylmethanamide (DMF), benzene (benzene), tetrahydrofuran (tetrahydrofuran, THF), and may be one or more selected from the group consisting of water. The amount of the solvent used may be adjusted in consideration of the coating thickness of the coating layer, physical properties of the solid electrolyte to be prepared, and the like.

In addition, the concentration of the first mixed solution and the second mixed solution is not particularly limited as long as the coating process can be performed. For example, the concentration of the first mixed solution and the second 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% It may be less than or equal to 30%. If the concentration of the mixed solution of the first mixed solution and the second mixed solution is less than 0.5%, the coating layer formed is too thin, and if it exceeds 30%, it may be difficult to uniformly form the coating layer. Concentrations of the first mixed solution and the second mixed solution may be the same or different.

The coating method includes bar coating, roll coating, spin coating, slit coating, die coating, blade coating, and comma coating. coating), slot die coating, lip coating, or solution casting, but is not limited thereto as long as the coating method can form a coating layer on the substrate.

In addition, the substrate is not particularly limited as long as it is a substrate that can be used to form the 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 , an ethylene-vinyl acetate film, an ethylene-propylene copolymer film, an ethylene-ethyl acrylate copolymer film, an ethylene-methyl acrylate copolymer film, or a polyimide film.

In the present invention, in the step (S2), the coating layer obtained in the step (S1) may be dried.

The drying is not particularly limited as long as the drying method can form a coating layer for forming a solid electrolyte by evaporating the solvent included in the coating layer. For example, the drying may be performed at 300° C. or less. Specifically, the drying temperature may be 300 °C or less, 200 °C or less, 150 °C or less, or 100 °C or less. The drying temperature may vary depending on the type of solvent and drying conditions. For example, vacuum drying may be performed at 100° C. or less. In addition, when the solvent is acetone or alcohol, it may be performed at 100 ° C or less. 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 may be, for example, 60°C or higher.

In the present invention, step (S3) may be additionally performed after step (S2), and in step (S3), after drying of step (S2), the coating layer is separated from the substrate and solidified. electrolytes can be obtained.

All-solid-state battery electrode and all-solid-state battery including 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 may be an anode or a cathode.

In the present invention, the positive electrode may include a positive electrode active material layer and a coating layer including the solid electrolyte formed on one surface of the positive electrode active material layer. The coating layer may be formed by attaching the solid electrolyte prepared by the above-described manufacturing method to the cathode active material layer, or may be formed by a coating method commonly used in the art. For example, the coating method is a spin method, a dipping method, a spray method, a roll court method, a gravure printing method, a bar court method, a die It may be a coating method, a comma coating method, or a combination thereof. The coating layer including the solid electrolyte may be in the form of a solid electrolyte membrane.

In addition, a positive electrode current collector may be additionally 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.

The cathode active material layer includes a cathode active material, a binder, and a conductive material.

In addition, the positive electrode active material is not particularly limited as long as it is a material capable of reversibly occluding and releasing lithium ions, and examples thereof include lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), Li[Ni _x Co _y Mn _z M _v ]O ₂ (Wherein, M is any one or two or more elements selected from the group consisting of Al, Ga, and In; 0.3≤x<1.0, 0≤y, z≤0.5, 0≤v≤0.1, x+y+z+v=1), Li(Li _a M _ba-b' M'_b' )O _2-c A _c (wherein 0≤a≤0.2, 0.6≤ b≤1, 0≤b'≤0.2, 0≤c≤0.2; M includes Mn and at least one selected from the group consisting of Ni, Co, Fe, Cr, V, Cu, Zn, and Ti; ; M' is at least one selected from the group consisting of Al, Mg, and B, and A is at least one selected from the group consisting of P, F, S, and N.) or layered compounds such as one or more compounds substituted with transition metals; lithium manganese oxides such as Li _1+y Mn _2-y O ₄ (where y is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , and LiMnO ₂ ; lithium copper oxide (Li ₂ CuO ₂ ); vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , and Cu ₂ V ₂ O ₇ ; Ni site type lithium nickel oxide represented by the formula LiNi _1-y MyO ₂ (where M=Co, Mn, Al, Cu, Fe, Mg, B or Ga, and y is 0.01 to 0.3); Formula LiMn _2-y M _y O ₂ (wherein M is Co, Ni, Fe, Cr, Zn or Ta and y is from 0.01 to 0.1) or Li ₂ Mn ₃ MO ₈ (wherein M is Fe, Co, Ni, Cu or Zn) lithium manganese composite oxide; LiMn ₂ O ₄ in which Li part of the formula is substituted with an alkaline earth metal ion; disulfide compounds; Fe ₂ (MoO ₄ ) ₃ etc. are mentioned, but it is not limited only to these.

In addition, 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 cathode active material may be 40% by weight or more or 50% by weight or more, and may be 70% by weight or less or 80% by weight or less. If the content of the cathode active material is less than 40% by weight, connectivity between the wet cathode active material layer and the dry cathode active material layer may be insufficient, and if the content of the cathode active material is greater than 80% by weight, mass transfer resistance may increase.

In addition, the binder is a component that assists in the bonding of the positive electrode active material and the conductive material and the bonding to the current collector, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile Butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluorine rubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene/propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene , polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethylcellulose , hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethylsucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, consisting of polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride and poly(vinylidene fluoride)-hexafluoropropene It may contain one or more selected from the group. Preferably, the binder may include at least one selected from the group consisting of styrene-butadiene rubber, polytetrafluoroethylene, carboxymethylcellulose, polyacrylic acid, lithium polyacrylate, and polyvinylidene fluoride.

In addition, the binder may be included in an amount of 1 wt% to 30 wt% based on the total weight of the positive electrode active material layer, and specifically, the content of the binder may be 1 wt% or more or 3 wt% or more, and 15 wt% or less than or equal to 30% by weight. If the content of the binder is less than 1% by weight, the adhesive strength between the positive electrode active material and the positive electrode current collector may be reduced, and if the content exceeds 30% by weight, the adhesive strength is improved, but the content of the positive electrode active material is reduced accordingly, and battery capacity may be lowered.

In addition, 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 change in 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 summer black; a carbon-based material whose crystal structure is graphene or graphite; conductive fibers such as carbon fibers and metal fibers; fluorinated carbon; metal powders such as aluminum powder and nickel powder; conductive whiskeys such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; And conductive polymers such as polyphenylene derivatives; may be used alone or in combination of two or more, but are not necessarily limited thereto.

The conductive material may be typically included in an amount of 0.5% to 30% by weight based on the total weight of the cathode active material layer, and specifically, the content of the conductive material may be 0.5% by weight or more or 1% by weight or more, and 20% by weight or less or It may be up to 30% by weight. If the content of the conductive material is too small, less than 0.5% by weight, it is difficult to expect an effect of improving electrical conductivity or the electrochemical characteristics of the battery may be deteriorated. Capacity and energy density may be lowered. A method of including the conductive material in the positive electrode is not particularly limited, and a conventional method known in the art, such as coating on a positive electrode active material, may be used.

In addition, the cathode current collector supports the cathode active material layer and serves to transfer electrons between an external conductor and the cathode active material layer.

The positive current collector is not particularly limited as long as it does not cause chemical change in the all-solid-state battery and has high electronic conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, copper or stainless steel surface treated with carbon, nickel, silver, etc., aluminum-cadmium alloy, etc. may be used as the anode current collector. can

The cathode current collector may have a fine concavo-convex structure or a 3-dimensional porous structure on the surface of the cathode current collector in order to enhance bonding strength with the cathode active material layer. Accordingly, the cathode current collector may include various forms such as a film, sheet, foil, mesh, net, porous material, foam, and nonwoven fabric.

The positive electrode as described above may be prepared according to a conventional method, and specifically, a composition for forming a positive electrode active material layer prepared by mixing a positive electrode active material, a conductive material, and a binder in an organic solvent is coated on a positive electrode current collector, dried, and selectively In order to improve the electrode density, it can be manufactured by compression molding on the current collector. At this time, as the organic solvent, it is preferable to use an organic solvent capable of uniformly dispersing the cathode active material, the binder, and the conductive material and easily evaporating. Specifically, acetonitrile, methanol, ethanol, tetrahydrofuran, water, isopropyl alcohol, etc. are mentioned.

In the present invention, the negative electrode may have a negative electrode active material layer and a coating layer including the solid electrolyte formed on one surface of the negative electrode active material layer. A method of forming the coating layer may be the same as a method of forming the coating layer at the anode.

In addition, an anode current collector may be additionally formed on the other surface of the anode active material layer. At this time, the negative electrode current collector and the negative electrode active material are not particularly limited as long as they are commonly used in all-solid-state batteries.

The anode active material layer includes an anode active material, a binder, and a conductive material.

The anode active material includes a material capable of reversibly intercalating or deintercalating lithium (Li ⁺ ), a material capable of reacting with lithium ions to reversibly form a lithium-containing compound, lithium metal, or a lithium alloy. can include

The material capable of reversibly intercalating or deintercalating lithium ions (Li ⁺ ) may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. A material capable of reversibly forming a lithium-containing compound by reacting with the lithium ion (Li ⁺ ) may be, for example, tin oxide, titanium nitrate, or silicon. The lithium alloy is, for example, lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium ( It may be an alloy of a metal selected from the group consisting of Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al), and tin (Sn).

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

The negative active material may be included in an amount of 40 to 80% by weight based on the total weight of the negative active material layer. Specifically, the content of the negative electrode active material may be 40% by weight or more or 50% by weight or more, and may be 70% by weight or less or 80% by weight or less. If the content of the negative active material is less than 40% by weight, connectivity between the wet negative active material layer and the dry negative active material layer may be insufficient, and if the content is greater than 80% by weight, mass transfer resistance may increase.

In addition, the binder is as described above in the positive electrode active material layer.

In addition, the conductive material is as described above for the positive electrode active material layer.

In addition, the anode current collector is not particularly limited as long as it does not cause chemical change in the battery and has conductivity. For example, the anode current collector is copper, stainless steel, aluminum, nickel, titanium, burnt carbon, or copper. B. Surface treatment of carbon, nickel, titanium, silver, etc. on the surface of stainless steel, aluminum-cadmium alloy, etc. may be used. In addition, the anode current collector, like the cathode current collector, may be used in various forms such as a film, sheet, foil, net, porous material, foam, nonwoven fabric, etc. having fine irregularities formed on the surface thereof.

The manufacturing method of the negative electrode is not particularly limited, and may be prepared by forming a negative electrode active material layer on a negative electrode current collector using a method of forming a layer or film commonly used in the art. For example, methods such as compression, coating, and deposition may be used. In addition, a case in which a metal lithium thin film is formed on a metal plate by initial charging after assembling a battery in a state in which the lithium thin film is not present on the negative electrode current collector is also included in the negative electrode of the present invention.

The present invention also relates to an all-solid-state battery comprising the electrode for an all-solid-state battery.

At least one of the positive electrode and the negative electrode included in the all-solid-state battery may be formed with a coating layer containing the solid electrolyte as described above.

Since the solid electrolyte exhibits excellent characteristics in both ion conductivity and electrical conductivity, it is applied to an all-solid-state battery in the form of a coating layer formed on a positive electrode and/or a negative electrode, thereby improving the performance and lifespan characteristics of the all-solid-state battery.

Hereinafter, preferred embodiments are presented to aid understanding of the present invention, but the following examples are merely illustrative of the present invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present invention. It goes without saying that changes and modifications fall within the scope of the appended claims.

In the following Examples and Comparative Examples, solid electrolytes for all-solid-state batteries were prepared according to the weight ratio of the electrically conductive polymer, inorganic material, and lithium salt as shown in Table 1 below.

solid electrolyte mixed conducting polymers mineral lithium salt weight ratio
(Mixed Conductive Polymer: Lithium Salt: Inorganic) Example 1 PEDOT:PSS ZnO LiTFSI 27.5:55:1 Example 2 PEDOT:PSS ZnO LiTFSI 11:22:1 Example 3 PEDOT:PSS SiO ₂ LiTFSI 11:22:1 Example 4 polypyrrole ZnO LiTFSI 11:22:1 Comparative Example 1 PEO - LiTFSI 10:1 Comparative Example 2 PEDOT:PSS - - - Comparative Example 3 - ZnO - - Comparative Example 4 - SiO ₂ - - Comparative Example 5 PEDOT:PSS ZnO - 11:1 Comparative Example 6 - ZnO LiTFSI 22:1

Example 1

5 g of a PEDOT:PSS solution (Sigma-Aldrich, 1.1 wt%), which is a mixed conductive polymer, and 0.11 g of LiTFSI (Sigma-Aldrich), a lithium salt, are sufficiently stirred for 12 hours to obtain a first mixed solution, followed by inorganic ZnO (Sigma-Aldrich) 2 mg was added to obtain a second mixed solution. The second mixed solution was coated on a stainless steel foil with a doctor blade to form a coating layer. The weight ratio ((PEDOT:PSS):LiTFSI:SBR) of the mixed conductive polymer, lithium salt, and inorganic material is 27.5:55:1. The weight ratio of PEDOT and PSS is 1:2.5.

Thereafter, the solid electrolyte membrane was prepared by vacuum drying at 100° C. for one day to remove the solvent in the second mixed solution.

Example 2

A solid electrolyte membrane was prepared in the same manner as in Example 1, except that the weight ratio of the mixed conductive polymer, lithium salt, and inorganic material ((PEDOT:PSS):LiTFSI:SBR) was 11:22:1.

Example 3

A solid electrolyte membrane was prepared in the same manner as in Example 1, except that SiO ₂ was used instead of ZnO as an inorganic material.

Example 4

A solid electrolyte and an all-solid-state battery were prepared in the same manner as in Example 2, except that polypyrrole was used instead of PEDOT:PSS as the mixed conductive polymer.

Comparative Example 1

A solid electrolyte membrane was prepared in the same manner as in Example 1, except that PEO was used instead of the mixed conductive polymer, inorganic materials were not used, and the weight ratio of PEO and lithium salt was set to 10:1.

Comparative Example 2

A solid electrolyte membrane was prepared in the same manner as in Example 1, except that only PEDOT:PSS, a mixed conductive polymer, was used.

Comparative Example 3

After fastening to a jig using only inorganic ZnO, pellets were produced in a state in which 10 MPa was applied.

Comparative Example 4

After fastening to a jig using only inorganic SiO ₂ , pellets were produced in a state in which 10 MPa was applied.

Comparative Example 5

A solid electrolyte membrane was prepared in the same manner as in Example 1, except that no lithium salt was used and the weight ratio of the mixed conductive polymer and the inorganic material was 11:1.

Comparative Example 6

A solid electrolyte membrane was prepared in the same manner as in Example 1, except that the mixed conductive polymer was not used and the weight ratio of the inorganic material and the lithium salt was 22:1.

Experimental Example 1: Solid Electrolyte Evaluation

For the solid electrolytes prepared in Examples and Comparative Examples, ionic conductivity and electrical conductivity were tested as follows, and the results are shown in Table 2 below.

(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. At this time, the measurement frequency was set to an amplitude range of 500 KHz to 20 MHz as an applied condition, and impedance was measured using BioLogic's VMP3. Using Equation 1 below, the resistance of the solid electrolyte membrane was obtained from the intersection (Rb) where the semicircle or straight line of the measured impedance trajectory meets the real axis, and the ionic conductivity (σ) of the solid electrolyte membrane was calculated from the area and thickness of the sample.

[Equation 1]

σ: ionic conductivity

Rb: Intersection of the impedance locus with the real axis

A: the area of the sample

t: thickness of the sample

(2) Electrical conductivity (S)

Manufactured with the same structure as the coin cell manufactured when measuring the ionic conductivity Cyclic voltammetry measurement (-0.1V to 0.1V) was performed on the coin cell, and electrical conductivity was calculated using Equation 2 below.

[Equation 2]

S = A/V * Film thickness/film dimension

A: current

V: voltage

Film thickness: the thickness of the sample

Film dimension: the area of the sample

measured temperature
(℃) thickness
(μm) ionic conductivity
(S/cm) electrical conductivity
(S/cm) Example 1 25 23 3.28 x 10 ^-5 2.595 x 10 ^-5 Example 2 25 19 3.59 x 10 ^-5 2.824 x 10 ^-5 Example 3 25 22 3.55 x 10 ^-5 2.799 x 10 ^-5 Example 4 25 45 9.12 x 10 ^-6 2.775 x 10 ^-7 Comparative Example 1 25 43 9.26 x 10 ^-8 8.778 x 10 ^-11 Comparative Example 2 25 11 - 2.716 x 10 ^-6 Comparative Example 3 25 689 - - Comparative Example 4 25 721 - - Comparative Example 5 25 32 - - Comparative Example 6 25 755 - -

As described in Table 2, it can be seen that the solid electrolyte membranes of Examples 1 to 4 exhibit higher ion conductivity and electrical conductivity than those of Comparative Example, since they contain the mixed conductive polymer, lithium salt, and inorganic material in an appropriate weight ratio.

In addition, it was confirmed that the conventional PEO-based solid electrolyte exhibited superior ion conductivity and electrical conductivity compared to Comparative Example 1.

Although the present invention has been described above with limited examples and drawings, the present invention is not limited thereto, and is described below and the technical spirit of the present invention by those skilled in the art to which the present invention belongs. Of course, various modifications and variations are possible within the scope of equivalents of the claims to be made.

Claims (18)

A solid electrolyte comprising a mixed conductive polymer, an inorganic material, and a lithium salt having ion conductivity and electrical conductivity characteristics. According to claim 1,
The mixed conductive polymer is poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS, poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)), polyacetylene, polyacetylene poly(paraphenylene), poly(paraphenylene) sulfide, polythiophene, polypyrrole, polyisothianaphtalene, polyparaphenylenevinylene (paraphenylene vinylene)), polyaniline (polyaniline) and poly (3,4-ethylenedioxythiophene) (poly (3,4-ethylenedioxythiophene)), a solid electrolyte comprising at least one selected from the group consisting of. According to claim 1,
The inorganic material is a solid electrolyte comprising at least one selected from the group consisting of oxide-based inorganic materials, nitride-based inorganic materials, and carbide-based inorganic materials. According to claim 3,
The oxide-based inorganic material is TiO ₂ , ZnO ₂ , ZnO, SrTiO ₃ , ZrPO ₄ , BaTiO ₃ , KNbO ₃ , Fe ₂ O ₃ , Ta ₂ O ₅ , WO ₃ , SnO ₂ , Bi ₂ O ₃ , NiO, Cu ₂ At least one selected from the group consisting of O, SiO, SiO ₂ , MoS ₂ , RuO ₂ and CeO ₂ ,
The nitride-based inorganic material includes at least one selected from the group consisting of AIN (Aluminium Nitride), BN (Boron Nitride), and Si ₂ N ₄ (Silicon Nitride),
The carbide-based inorganic material is a solid electrolyte comprising at least one selected from the group consisting of CuC, AgC and AuC. According to claim 1,
The lithium salt is LiTFSI (Lithium bis(trifluoromethanesulphonyl)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 A solid electrolyte comprising at least one member selected from the group consisting of NLi. According to claim 1,
The solid electrolyte is
A solid electrolyte comprising 100 parts by weight of the mixed conductive polymer, 2 to 30 parts by weight of an inorganic material, and 5 to 300 parts by weight of a lithium salt based on 100 parts by weight of the mixed conductive polymer. According to claim 1,
The solid electrolyte is
A solid electrolyte comprising 100 parts by weight of the mixed conductive polymer, 2 to 30 parts by weight of a binder, and 100 to 300 parts by weight of a lithium salt based on 100 parts by weight of the mixed conductive polymer. According to claim 1,
The solid electrolyte is a solid electrolyte in which a lithium salt is dissociated and included in a mixed conductive polymer matrix including a mixed conductive polymer and an inorganic material. According to claim 1,
The solid electrolyte is a solid electrolyte in the form of a solid electrolyte membrane. According to claim 1,
The thickness of the solid electrolyte is 10 to 60 ㎛, the solid electrolyte. (S1) coating a mixed solution obtained by adding a mixed conductive polymer, an inorganic material, and a lithium salt to a solvent on a substrate; and
(S2) drying the coating layer obtained in step (S1); a method of manufacturing a solid electrolyte according to claim 1 including. According to claim 11,
The coating method includes bar coating, roll coating, spin coating, slit coating, die coating, blade coating, and comma coating. coating), slot die coating, lip coating, or solution casting, which is a method for producing a solid electrolyte. According to claim 11,
The drying is a method for producing a solid electrolyte, which is performed at 300 ° C or less. According to claim 11,
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 An acetate film, an ethylene-propylene copolymer film, an ethylene-ethyl acrylate copolymer film, an ethylene-methyl acrylate copolymer film, or a polyimide film, a method for producing a solid electrolyte. According to claim 11,
The solvent is dimethylsulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, xylene, dimethylformamide (N,N-Dimethylmethanamide , DMF), benzene (benzene), tetrahydrofuran (tetrahydrofuran, THF) and at least one selected from the group consisting of water, a method for producing a solid electrolyte. An electrode for an all-solid-state battery having a coating layer comprising the solid electrolyte of claim 1. The electrode according to claim 16, wherein the electrode is an anode or a cathode. An all-solid-state battery comprising the electrode of claim 16.

Images