Composite solid electrolyte membrane, manufacturing method therefor, and all-solid-state battery comprising same

Abstract

The present invention relates to a composite solid electrolyte membrane, a manufacturing method therefor, and an all-solid-state battery comprising same, the composite solid electrolyte membrane comprising: a solid electrolyte membrane including a solid electrolyte and a binder; and an ionic liquid, wherein the solid electrolyte membrane includes a plurality of pores, the ionic liquid is impregnated in the plurality of pores, and the anion of the ionic liquid is (CF3SO2)2N-.

Description

Composite solid electrolyte membrane, method for manufacturing the same, and all-solid-state battery comprising the same

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0021572, dated February 15, 2024, the entire disclosure of which is incorporated herein by reference.

[0002] The present invention relates to a composite solid electrolyte membrane, a method for producing the same, and an all-solid-state battery including the same.

[0003]

[0004] Various batteries are being studied to overcome the limitations of current lithium secondary batteries in terms of battery capacity, safety, output, large-scale development, and miniaturization.

[0005] Representative examples include metal-air batteries with much larger theoretical capacity than lithium secondary batteries, all-solid-state batteries with no risk of explosion in terms of safety, supercapacitors for output, NaS batteries or RFBs (redox flow batteries) for large-scale applications, and thin film batteries for miniaturization, all of which are being continuously researched in academia and industry.

[0006] All-solid-state batteries replace the liquid electrolytes used in conventional lithium secondary batteries with solid electrolytes. Because they do not use flammable solvents, they eliminate the risk of fire or explosion caused by decomposition reactions of conventional electrolytes, significantly improving safety. Furthermore, because lithium metal or lithium alloys can be used as anode materials, they offer the advantage of dramatically improving the battery's energy density relative to its mass and volume.

[0007] To improve the energy density of all-solid-state batteries, the production of solid electrolyte membranes is essential. Conventionally, pellet-shaped solid electrolyte layers were manufactured by controlling solid electrolyte powder under pressure and temperature. These pellet-shaped solid electrolyte layers suffer from brittleness and breakage, and their thicknesses, often exceeding several hundred μm, result in low energy density. Large-area production is difficult, and pore control is challenging.

[0008] Accordingly, processes suitable for mass production, such as slurry application, dry process, and self-supporting membrane manufacturing, are currently being used, and these processes can manufacture solid electrolyte membranes with a thin thickness, which has excellent effects in terms of energy density. However, the solid electrolyte membranes manufactured through these processes contain a large number of pores, and these pores inevitably cause a reduction in the lithium ion migration path. To solve the above problem, an additional process of pressurizing the solid electrolyte membrane was performed, but not only was it difficult to completely control the pores, but if the pressurization was excessively performed, the binder moved within the solid electrolyte membrane, which caused a decrease in ionic conductivity. In addition, as the solid electrolyte membrane became thinner, the problem of a decrease in ionic conductivity also occurred.

[0009] Therefore, there is a need for research on a solid electrolyte membrane that controls the pores of the solid electrolyte membrane and has excellent ionic conductivity even when the solid electrolyte membrane is thin.

[0010]

[0011] [Previous literature]

[0012] [Patent Document]

[0013] Republic of Korea Patent No. 10-2280683

[0014]

[0015] In order to solve the above problems, the inventors of the present invention conducted a multifaceted study and, as a result, manufactured a solid electrolyte membrane in the form of a film including a solid electrolyte and a binder, and then anions (CF3SO2)2N were added to the pores of the solid electrolyte membrane.- The present invention was completed by confirming that high ionic conductivity can be obtained even if the thickness of the composite solid electrolyte membrane is thin by impregnating it with an ionic liquid.

[0016] Accordingly, an object of the present invention is to provide a composite solid electrolyte membrane having excellent ionic conductivity.

[0017] In addition, an object of the present invention is to provide an all-solid-state battery including the composite solid electrolyte membrane.

[0018]

[0019] To achieve the above purpose,

[0020] The present invention relates to a solid electrolyte membrane comprising a solid electrolyte and a binder; and

[0021] A composite solid electrolyte membrane comprising an ionic liquid,

[0022] The above solid electrolyte membrane includes a plurality of pores,

[0023] The above ionic liquid is impregnated into the plurality of pores,

[0024] The anion of the above ionic liquid is (CF3SO2)2N - A composite solid electrolyte membrane is provided.

[0025] In addition, the present invention comprises the steps of (1) manufacturing a solid electrolyte membrane including a plurality of pores using a mixture including a solid electrolyte and a binder; and

[0026] (2) A step of impregnating an ionic liquid into a solid electrolyte membrane including the plurality of pores;

[0027] The anion of the above ionic liquid is (CF3SO2)2N - In addition, the present invention provides a method for manufacturing a composite solid electrolyte membrane.

[0028]

[0029] In addition, the present invention provides an all-solid-state battery including a positive electrode, a negative electrode, and a solid electrolyte membrane interposed therebetween,

[0030] The above solid electrolyte membrane provides an all-solid-state battery, which is a composite solid electrolyte membrane of the present invention.

[0031]

[0032] The composite solid electrolyte membrane of the present invention has an anion (CF3SO2)2N in the pores of the solid electrolyte membrane. - By impregnating the ionic liquid, the ion conductive area reduced by the pores can be improved, and thus the ion conductivity can be excellent.

[0033]

[0034] Figure 1 is a photograph showing the impregnation of an ionic liquid (PMIM TFSI) into a solid electrolyte membrane.

[0035] Figure 2 is a photograph showing the impregnation of an ionic liquid (EMIM TFSI) into a solid electrolyte membrane.

[0036] Figure 3 is an SEM photograph of the solid electrolyte membrane of Comparative Example 1.

[0037] Figure 4 is a photograph showing the impregnation of an ionic liquid (EMIM BF4) into a solid electrolyte membrane.

[0038] Figure 5 is a photograph showing the impregnation of an ionic liquid (EMIM DCA) into a solid electrolyte membrane.

[0039] Figure 6 is a photograph evaluating the side reaction according to the type of anion of the solid electrolyte membrane and ionic liquid.

[0040] Figure 7 is a graph of the ionic conductivity of the composite solid electrolyte membranes of Examples 1 and 2 and the solid electrolyte membrane of Comparative Example 1.

[0041]

[0042] Hereinafter, the present invention will be described in more detail.

[0043]

[0044] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0045] The terminology used in the present invention is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In the present invention, it should be understood that the terms "comprise" or "have" are intended to specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0046]

[0047] Composite solid electrolyte membrane

[0048] The present invention relates to a solid electrolyte membrane comprising a solid electrolyte and a binder; and

[0049] A composite solid electrolyte membrane comprising an ionic liquid,

[0050] The above solid electrolyte membrane includes a plurality of pores,

[0051] The above ionic liquid is impregnated into the plurality of pores,

[0052] The anion of the above ionic liquid is (CF3SO2)2N - It relates to a composite solid electrolyte membrane.

[0053]

[0054] The above solid electrolyte membrane may be manufactured from a mixture containing a solid electrolyte and a binder, and may be in the form of a film.

[0055] The above solid electrolyte may include a sulfide-based solid electrolyte.

[0056] The above sulfide-based solid electrolyte contains sulfur (S) and has the ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and may include Li-PS-based glass or Li-PS-based glass ceramic.

[0057] Specifically, the sulfide-based solid electrolyte is Li a PS b X(0 <a≤6, 0<b≤5, X=Cl, Br 또는 I), Li2S-P2S5, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2S5, Li2S-P2S5-SiS2, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2및 Li2S-GeS2-ZnS로 이루어진 군으로부터 선택되는 1종 이상을 포함하는 것일 수 있으며, 바람직하게는 Li a PS b X(0 <a≤6, 0<b≤5, X=Cl, Br 또는 I)일 수 있다. 상기 Li a PS b X(0 <a≤6, 0<b≤5, X=Cl, Br 또는 I)는 아지로다이트형(Argyrodite type) 고체 전해질일 수 있다. 또한, 보다 바람직하게는 Li6PS5Cl, Li6PS5Br 및 Li6PS5I로 이루어진 군으로부터 선택되는 1종 이상을 포함할 수 있다. 또한, 상기 황화물계 고체 전해질은 미량의 원소들이 도핑된 형태일수 있으며, 예를 들어 Li6PS5Cl에 브롬(Br)이 추가적으로 도핑된 것일 수 있다.

[0058] The above binder is not particularly limited in type as long as it is used in the art.

[0059] For example, one or two selected from the group consisting of nitrile butadiene rubber (NBR), acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), butadiene rubber (BR), styrene-butadiene-styrene copolymer (SBS), polybutadiene (PAN), styrene-ethylene / butylene-styrene block copolymer (SEBS), silicone rubber (SR), hydrogenated nitrile butadiene rubber (HNBR), poly(ethylene vinyl acetate) (PEVA), poly(methyl methacrylate) (PMMA), polyisobutene (PIB), and polyacrylate, or copolymers thereof, may be used, but the present invention is not limited thereto, and it may be preferable to use nitrile butadiene rubber.

[0060] In addition, a polymer formed by adding a polymer resin to a solvated lithium salt, i.e. a composite of a lithium salt and a polymer resin as a binder, can be used, and about 1x10 -7 S / cm or more, preferably about 1x10 -5 It may have an ionic conductivity of S / cm or more.

[0061] Non-limiting examples of the polymer resin include polyether polymers, polycarbonate polymers, acrylate polymers, polysiloxane polymers, phosphazene polymers, polyethylene derivatives, alkylene oxide derivatives such as polyethylene oxide, phosphate ester polymers, polyagitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, polymers containing ionic dissociative groups, etc., and one or more of these may be included. In addition, examples include branched copolymers, comb-like polymers, and cross-linked polymer resins, which copolymerize amorphous polymers such as PMMA, polycarbonate, polysiloxane (PDMS), and / or phosphazene into a polyethylene oxide (PEO) main chain as comonomers. One or more of these may be included.

[0062] The above lithium salt is an ionizable lithium salt, Li + X - It can be expressed as . There is no particular limitation on the anion of these lithium salts, but F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C -, (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , (CF3CF2SO2)2N - Examples include:

[0063] The above solid electrolyte and binder can be mixed in a weight ratio of 95:5 to 99.5:0.5. By mixing in the above weight ratio, a solid electrolyte membrane for an all-solid-state battery that can be maintained in a film form while minimizing the content of the binder that acts as a resistance to ionic conductivity can be manufactured.

[0064] In one embodiment, the above film-shaped solid electrolyte membrane may be manufactured by pressurizing a mixture comprising the solid electrolyte and a binder. In another embodiment, the above film-shaped solid electrolyte membrane may be manufactured by preparing a slurry comprising the solid electrolyte and a binder, and then applying and drying the same.

[0065] The solvent used in the above slurry is not particularly limited in type as long as it can disperse the solid electrolyte and binder, and examples thereof include xylene, hexane, benzene, anisole, isobutyl isobutyrate, toluene, and butyl butyrate.

[0066] The above film-shaped solid electrolyte membrane can form multiple pores when the mixture is pressurized or the solvent of the slurry evaporates. Due to these multiple pores, the movement path of lithium ions is reduced, which reduces the ionic conductivity of the solid electrolyte membrane. The present invention attempts to solve this problem by impregnating an ionic liquid into the multiple pores formed in the solid electrolyte membrane. When the ionic liquid is impregnated into the multiple pores formed in the solid electrolyte membrane, it can provide an additional movement path for lithium ions without interfering with the movement path of lithium ions. Therefore, the present invention can provide a composite solid electrolyte membrane with excellent ionic conductivity.

[0067] Therefore, the composite solid electrolyte membrane of the present invention includes an ionic liquid, and the ionic liquid may be impregnated into a plurality of pores of the solid electrolyte membrane. In addition, the anion of the ionic liquid is (CF3SO2)2N. - (bis(trifluoromethanesulfonyl)imide) , TFSI - ) may be. The anion of the above ionic liquid is (CF3SO2)2N - It does not cause side reactions with the solid electrolyte membrane, and the affinity between the solid electrolyte membrane and the ionic liquid is excellent, so that the impregnation of the ionic liquid into the multiple pores formed in the solid electrolyte membrane occurs very well, which can improve the ionic conductivity of the composite solid electrolyte membrane. If the anion of the ionic liquid is (CF3SO2)2N - Otherwise, a side reaction may occur with the solid electrolyte membrane, and the affinity between the solid electrolyte membrane and the ionic liquid may be poor, so that the ionic liquid may not be impregnated into the multiple pores formed in the solid electrolyte membrane, resulting in a leakage phenomenon, and thus, the performance of the all-solid-state battery may deteriorate.

[0068] The cation of the above ionic liquid may be at least one selected from the group consisting of pyrrolidimium, piperidinium, imidazolium, phosphonium, ammonium, and pyridinium.

[0069] The total volume of the plurality of pores may be 1 to 50 volume% with respect to the total volume of the solid electrolyte membrane.

[0070] In order to impregnate the ionic liquid into the plurality of pores formed in the above solid electrolyte membrane, the ionic liquid may be included in an amount equal to the volume of the pores. The ionic liquid may be included in an amount of 3 to 50 parts by weight, and preferably 4 to 30 parts by weight, based on 100 parts by weight of the solid electrolyte.

[0071] In addition, the ionic liquid can be impregnated at 80 to 100 volume% with respect to the pore volume of the solid electrolyte membrane, and preferably 95 to 100 volume%.

[0072] The composite solid electrolyte membrane of the present invention is in the form of a film, and the pores of the solid electrolyte membrane including a plurality of pores are impregnated with an ionic liquid, and the anion of the ionic liquid is (CF3SO2)2N - As described above, the composite solid electrolyte membrane of the present invention can provide an additional movement path of lithium ions without interfering with the movement path of lithium ions, and thus can have high ionic conductivity.

[0073] Additionally, the thickness of the composite solid electrolyte membrane may be 10 to 200 μm. Therefore, the composite solid electrolyte membrane of the present invention can have high ionic conductivity even with a thin thickness.

[0074]

[0075] Method for manufacturing a composite solid electrolyte membrane

[0076] In addition, the present invention relates to a method for manufacturing a composite solid electrolyte membrane of the present invention described above,

[0077] (1) a step of manufacturing a solid electrolyte membrane including a plurality of pores using a mixture including a solid electrolyte and a binder; and

[0078] (2) A step of impregnating an ionic liquid into a solid electrolyte membrane including the plurality of pores; wherein the anion of the ionic liquid is (CF3SO2)2N - It could be.

[0079]

[0080] The above step (1) may be a step of manufacturing a solid electrolyte membrane including a plurality of pores using a mixture including a solid electrolyte and a binder.

[0081] The above solid electrolyte membrane may be manufactured by pressurizing a mixture containing a solid electrolyte and a binder, or by manufacturing a slurry containing the solid electrolyte and a binder and then applying and drying the same.

[0082] In the process of pressurizing the mixture including the solid electrolyte and binder, or in the process of drying the slurry, a plurality of pores can be formed in the solid electrolyte membrane.

[0083] The above step (2) is a step of impregnating an ionic liquid into a solid electrolyte membrane including a plurality of pores manufactured in the above step (1), and the ionic liquid may be impregnated into a plurality of pores formed in the solid electrolyte membrane.

[0084] In addition, the anion of the ionic liquid is (CF3SO2)2N - , and the ionic liquid, the content of the ionic liquid, the pore volume of the solid electrolyte membrane, and the degree to which the ionic liquid is impregnated into the pores are the same as described above.

[0085]

[0086] If a mixture containing a solid electrolyte, a binder, and an ionic liquid is prepared and a composite solid electrolyte membrane is prepared using the mixture, the binder and the ionic liquid may phase separate as the mixture dries, resulting in a composite solid electrolyte membrane having a very uneven surface. In addition, pores may be formed in the composite solid electrolyte membrane as the solvent of the mixture evaporates. Although the ionic liquid included in the mixture may be impregnated into some of the pores of the solid electrolyte membrane, the ionic liquid cannot be impregnated at 80 to 100% by volume with respect to the pore volume of the solid electrolyte membrane, as in the composite solid electrolyte membrane of the present invention. That is, if a composite solid electrolyte membrane is prepared using a mixture containing a solid electrolyte, a binder, and an ionic liquid, pores are re-formed in the composite solid electrolyte membrane during the drying process, and it is difficult for the ionic liquid present in the mixture to impregnate all of the re-formed pores, resulting in a composite solid electrolyte membrane having multiple pores. When pores are formed in a composite solid electrolyte membrane, the movement path of lithium ions is reduced, so it can exhibit very low ionic conductivity.

[0087] On the other hand, if an ionic liquid is impregnated into the pores formed in the solid electrolyte membrane after manufacturing the solid electrolyte membrane, a composite solid electrolyte membrane can be provided in which the ionic liquid is impregnated at 80 to 100% by volume based on the pore volume of the solid electrolyte membrane. Therefore, the composite solid electrolyte membrane of the present invention can have very excellent ionic conductivity.

[0088]

[0089] All-solid-state batteries

[0090] In addition, the present invention relates to an all-solid-state battery including a positive electrode, a negative electrode, and a solid electrolyte membrane interposed therebetween, wherein the solid electrolyte membrane may be the composite solid electrolyte membrane of the present invention described above.

[0091] The above all-solid-state battery is a lithium secondary battery, and there is no limitation on the positive or negative electrode, and it may be a lithium-air battery, a lithium oxide battery, a lithium-sulfur battery, or a lithium metal battery.

[0092]

[0093] The above positive electrode may include a positive electrode current collector and a positive electrode active material layer applied to one or both sides of the positive electrode current collector.

[0094] The above positive electrode current collector is intended to support the positive electrode active material layer, and is not particularly limited as long as it has excellent conductivity and is electrochemically stable in the voltage range of the lithium secondary battery. For example, the positive electrode current collector may be any one metal selected from the group consisting of copper, aluminum, stainless steel, titanium, silver, palladium, nickel, alloys thereof, and combinations thereof. The stainless steel may be surface-treated with carbon, nickel, titanium, or silver. As the alloy, an aluminum-cadmium alloy may be preferably used. In addition, calcined carbon, a non-conductive polymer surface-treated with a conductive material, or a conductive polymer may be used.

[0095] The above-mentioned positive electrode current collector can form fine irregularities on its surface to strengthen the bonding strength with the positive electrode active material, and can be used in various forms such as a film, sheet, foil, mesh, net, porous body, foam, and non-woven fabric.

[0096] The above positive electrode active material layer may include a positive electrode active material and optionally a conductive material and a binder.

[0097] The above positive electrode active material may vary depending on the type of all-solid-state battery. For example, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; chemical formula Li 1+x Mn 2-xLithium manganese oxides such as O4(0≤x≤0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-x M x Ni-site lithium nickel oxide represented by O2 (M = Co, Mn, Al, Cu, Fe, Mg, B or Ga; 0.01≤x≤0.3); chemical formula LiMn 2-x M x Lithium manganese composite oxides expressed as O2 (M = Co, Ni, Fe, Cr, Zn or Ta; 0.01≤x≤0.1) or Li2Mn3MO8 (M = Fe, Co, Ni, Cu or Zn); LiNi x Mn 2-x Lithium manganese composite oxide with spinel structure represented by O4; LiCoPO4; LiFePO4; Elemental sulfur (S8); Li2S n (n=1), organosulfur compounds or carbon-sulfur polymers (C2S x ) n : It may include sulfur series compounds such as x=2.5 ~ 50, n=2), but is not limited to these.

[0098] The above conductive material is a material that electrically connects the electrolyte and the positive electrode active material and serves as a path for electrons to move from the current collector to the positive electrode active material. Any material that does not cause chemical changes in a lithium secondary battery and has porosity and conductivity can be used without restriction.

[0099] For example, the conductive material may be a porous carbon-based material, such as carbon black, graphite, graphene, activated carbon, carbon fiber, etc.; metallic fibers such as metal mesh; metallic powders such as copper, silver, nickel, aluminum, etc.; or organic conductive materials such as polyphenylene derivatives. The conductive materials may be used alone or in combination.

[0100] Current commercially available products include acetylene black series (such as those from Chevron Chemical Company or Gulf Oil Company), Ketjen Black EC series (from Armak Company), Vulcan XC-72 (from Cabot Company), and Super P (from MMM). Examples include acetylene black, carbon black, and graphite.

[0101] In addition, the binder increases the bonding strength between the components constituting the positive electrode and between them and the current collector, and any binder known in the industry can be used.

[0102] For example, the binder may be a fluororesin binder including polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE); a rubber binder including styrene butadiene rubber (SBR), acrylonitrile-butidiene rubber, and styrene-isoprene rubber; a cellulose binder including carboxyl methyl cellulose (CMC), starch, hydroxy propyl cellulose, and regenerated cellulose; a polyalcohol binder; a polyolefin binder including polyethylene and polypropylene; a polyimide binder; a polyester binder; and a silane binder. One, two or more mixtures or copolymers selected from the group consisting of may be used.

[0103]

[0104] The above-mentioned negative electrode may include a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector. In addition, the negative electrode, like the positive electrode, may include a conductive material and a binder as needed. In this case, the negative electrode current collector, conductive material, and binder are as described above.

[0105] The above negative active material is lithium ion (Li + ) can be reversibly intercalated or deintercalated, or any material that can react with lithium ions to form a reversibly lithium-containing compound.

[0106] For example, the negative active material may be at least one carbon-based material selected from the group consisting of crystalline artificial graphite, crystalline natural graphite, amorphous hard carbon, low-crystalline soft carbon, carbon black, acetylene black, Ketjen black, Super-P, graphene, and fibrous carbon, Si-based material, Li xFe2O3(0≤x≤1), Li x WO2(0≤x≤1), Sn x Me 1-x Me´ y O z (Me: Mn, Fe, Pb, Ge; Me´: Al, B, P, Si, elements of group 1, 2, and 3 of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 규소계 합금; 주석계 합금; SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료; 티타늄 산화물; 리튬 티타늄 산화물 등을 포함할 수 있지만, 이들만으로 한정되는 것은 아니다.

[0107] Additionally, the negative electrode may include a negative electrode current collector and a coating layer including metal-carbon composite particles positioned on the negative electrode current collector. This may mean an anodeless electrode that does not include a negative electrode active material.

[0108] The above negative electrode may be such that when the all-solid-state battery is charged, lithium ions pass through the coating layer to reach the surface of the negative electrode current collector, and these are deposited to form a lithium metal layer.

[0109] The above metal-carbon composite particles may have a form in which carbon particles and metal particles are attached to each other or one surface is coated with the other, and may be physically or chemically bonded.

[0110] The above carbon particles may include natural graphite, artificial graphite, hard carbon, soft carbon, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, carbon nanotubes, fullerene, carbon fiber, and fluorocarbon.

[0111] The above metal particles are lithium-philic metals, for example, Ni, Cu, Ag, Au, Pt, Al, Zn, Bi, etc., and may be one or a combination of two or more thereof. By introducing a metal having the above lithium-philic properties, it is advantageous to form a stable and uniform lithium layer on the surface of the current collector.

[0112] The above negative electrode may be manufactured by mixing a binder solution and the composite particles to prepare a slurry for forming a coating layer, and then applying and drying the slurry on a negative electrode current collector. In this case, the binder may be a conventional binder used in the art.

[0113]

[0114] The manufacture of the above all-solid-state battery is not particularly limited in the present invention, and a known method can be used.

[0115] For example, a composite solid electrolyte membrane is placed between the positive and negative electrodes, and then compressed to assemble the cell. The assembled cell is then installed within an outer packaging material and sealed by heating and compression, etc. The outer packaging material can be a laminate pack made of aluminum, stainless steel, or a metal container, such as a cylindrical or square container.

[0116] For example, the positive and negative electrodes are manufactured through a slurry coating process in which a slurry composition containing each electrode active material, solvent, and binder is manufactured, coated, and then dried.

[0117] Methods for coating the electrode slurry on the current collector include a method of distributing the electrode slurry on the current collector and then uniformly dispersing it using a doctor blade or the like, die casting, comma coating, screen printing, etc. In addition, the electrode slurry may be formed on a separate substrate and then bonded to the current collector by pressing or lamination. At this time, the final coating thickness can be controlled by adjusting the concentration of the slurry solution or the number of coatings.

[0118] The drying process is a process of removing the solvent and moisture within the slurry to dry the slurry coated on the metal collector. This process may vary depending on the solvent used. For example, it is performed in a vacuum oven at 50 to 200°C. Examples of drying methods include drying using warm air, hot air, or low-humidity air, vacuum drying, and drying using irradiation with (far) infrared rays or electron beams. The drying time is not particularly limited, but is typically performed within the range of 30 seconds to 24 hours.

[0119] After the above drying process, a cooling process may be further included, and the cooling process may be slow cooling to room temperature so that the recrystallized structure of the binder is well formed.

[0120] Additionally, if necessary, after the drying process, a rolling process may be performed to compress the electrode to a desired thickness by passing it between two high-temperature heated rolls to increase the capacity density of the electrode and enhance the adhesion between the current collector and the active materials. The rolling process is not particularly limited in the present invention, and any known pressing process is possible. For example, it may be performed by passing it between rotating rolls or using a flat plate press.

[0121] The shape of the above-mentioned all-solid-state battery is not particularly limited, and can be made into various shapes such as cylindrical, laminated, and coin-shaped.

[0122]

[0123] Hereinafter, preferred examples are presented to help understand the present invention, but the following examples are only 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 technical idea of ​​the present invention, and it is also natural that such changes and modifications fall within the scope of the appended patent claims.

[0124]

[0125] Example 1. Preparation of composite solid electrolyte membrane

[0126] Nitrile butadiene rubber was used as a binder, and a binder solution was prepared by mixing the binder and toluene at a weight ratio of 3:97. Argyrodite (Li6PS5Cl) was used as a solid electrolyte, and a slurry for preparing a solid electrolyte membrane was prepared by mixing the solid electrolyte with the binder solution. At this time, the weight ratio of the binder to the solid electrolyte was 3:97.

[0127] The above slurry for manufacturing a solid electrolyte membrane was applied and dried on a release film to manufacture a solid electrolyte membrane including a plurality of pores, and the total volume of the formed pores was 30% by volume with respect to the total volume of the solid electrolyte membrane.

[0128] 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide (PMIM TFSI) was used as the ionic liquid.

[0129] 1.2 μL of ionic liquid was used so that the ionic liquid could be impregnated at 100% by volume with respect to the pore volume of the above solid electrolyte membrane, and a composite solid electrolyte membrane was manufactured by impregnating the solid electrolyte membrane with the ionic liquid.

[0130] As a result of calculating the weight difference between the solid electrolyte membrane and the composite solid electrolyte membrane, it was confirmed that the ionic liquid was impregnated at 100% by volume with respect to the pore volume of the solid electrolyte membrane.

[0131] Figure 1 is a photograph showing the impregnation of an ionic liquid into a solid electrolyte membrane. The ionic liquid, PMIM TFSI, showed excellent affinity with the solid electrolyte membrane and a low contact angle, and it was confirmed that the impregnation of the ionic liquid into the solid electrolyte membrane proceeded smoothly.

[0132]

[0133] Example 2. Preparation of composite solid electrolyte membrane

[0134] A composite solid electrolyte membrane was manufactured in the same manner as in Example 1, except that 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI) was used as the ionic liquid.

[0135] As a result of calculating the weight difference between the solid electrolyte membrane and the composite solid electrolyte membrane, it was confirmed that the ionic liquid was impregnated at 100% by volume with respect to the pore volume of the solid electrolyte membrane.

[0136] Figure 2 is a photograph showing the impregnation of an ionic liquid into a solid electrolyte membrane. The ionic liquid, EMIM TFSI, has excellent affinity with the solid electrolyte membrane, so the ionic liquid exhibits a low contact angle, and it was confirmed that the impregnation of the ionic liquid into the solid electrolyte membrane proceeds smoothly.

[0137]

[0138] Comparative Example 1. Manufacturing of a solid electrolyte membrane

[0139] Nitrile butadiene rubber was used as a binder, and a binder solution was prepared by mixing the binder and toluene at a weight ratio of 3:97. Argyrodite (Li6PS5Cl) was used as a solid electrolyte, and a slurry for preparing a solid electrolyte membrane was prepared by mixing the solid electrolyte with the binder solution. At this time, the weight ratio of the binder to the solid electrolyte was 3:97.

[0140] The above slurry for manufacturing a solid electrolyte membrane was applied and dried on a release film to manufacture a solid electrolyte membrane including a plurality of pores, and the total volume of the formed pores was 30% by volume with respect to the total volume of the solid electrolyte membrane.

[0141] Figure 3 is an SEM photograph observing the surface of a solid electrolyte membrane, and it was confirmed that the surface was uniform and pores were formed.

[0142]

[0143] Comparative Example 2. Preparation of a composite solid electrolyte membrane

[0144] A composite solid electrolyte membrane was manufactured in the same manner as in Example 1, except that 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM BF4) was used as the ionic liquid.

[0145] Figure 4 is a photograph showing the impregnation of an ionic liquid into a solid electrolyte membrane. The ionic liquid, EMIM BF4, had poor affinity with the solid electrolyte membrane, so the ionic liquid showed a high contact angle, and it was confirmed that the ionic liquid was not impregnated into the solid electrolyte membrane.

[0146]

[0147] Comparative Example 3. Manufacturing of a Composite Solid Electrolyte Membrane

[0148] A composite solid electrolyte membrane was manufactured in the same manner as in Example 1, except that 1-ethyl-3-methylimidazolium dicyanamide (EMIM DCA) was used as the ionic liquid.

[0149] Figure 5 is a photograph showing the impregnation of an ionic liquid into a solid electrolyte membrane. The ionic liquid, EMIM DCA, had poor affinity with the solid electrolyte membrane, so the ionic liquid showed a high contact angle, and it was confirmed that the ionic liquid was not impregnated into the solid electrolyte membrane.

[0150]

[0151] Therefore, the anion of the ionic liquid is (CF3SO2)2N - It was found that the ionic liquid had excellent affinity with the solid electrolyte membrane and was impregnated at 100% by volume with respect to the pore volume of the solid electrolyte membrane.

[0152] On the other hand, the anion of the ionic liquid is (CF3SO2)2N - Otherwise, it was found that the ionic liquid did not impregnate into the pores formed in the solid electrolyte membrane due to poor affinity with the solid electrolyte membrane.

[0153]

[0154] Experimental Example 1. Evaluation of side reactions between solid electrolyte membranes and ionic liquids

[0155] 5 mg of solid electrolyte (Li6PS5Cl) and the ionic liquids used in Examples 1 and 2 and Comparative Examples 2 and 3 were each mixed. The state of the mixture was observed after 24 hours, and is shown in Fig. 6.

[0156] The ionic liquids of Examples 1 and 2, PMIM TSFI and EMIM TFSI, did not undergo a side reaction with the solid electrolyte and thus did not undergo discoloration. On the other hand, it was confirmed that the ionic liquids of Comparative Examples 2 and 3, EMIM BF4 and EMIM DCA, underwent a side reaction with the solid electrolyte and thus discoloration occurred.

[0157] Therefore, the anion of the ionic liquid is (CF3SO2)2N - It was confirmed that a composite solid electrolyte membrane could be manufactured because no side reaction occurred with the solid electrolyte. On the other hand, the anion of the ionic liquid (CF3SO2)2N - Otherwise, it was confirmed that not only would the ionic liquid not be impregnated into the pores formed in the solid electrolyte membrane, but also a side reaction would occur with the solid electrolyte membrane, making it impossible to manufacture a composite solid electrolyte membrane.

[0158]

[0159] Experimental Example 2. Measurement of ionic conductivity

[0160] The ionic conductivity of the composite solid electrolyte membranes of Examples 1 and 2 and the solid electrolyte membrane of Comparative Example 1 was measured.

[0161] The ionic conductivity was calculated using the following mathematical formula 1 after measuring the resistance of the composite solid electrolyte membranes of Examples 1 and 2 and the solid electrolyte membrane of Comparative Example 1.

[0162] [Mathematical Formula 1]

[0163]

[0164] (σ = ionic conductivity, L = thickness of composite solid electrolyte membrane (Examples 1 and 2) or solid electrolyte membrane (Comparative Example 1), R = resistance, A = area of ​​composite solid electrolyte membrane (Examples 1 and 2) or solid electrolyte membrane (Comparative Example 1))

[0165] Composite solid electrolyte membrane of Example 1 (area 78.5 mm 2X thickness 0.006 cm (error ±5 μm)) was prepared. It was manufactured in the form of titanium / composite solid electrolyte membrane of Example 1 / titanium, and after pressurization, an AC voltage was applied to the titanium, and the temperature condition was 25°C. The application conditions were set to an amplitude of 5 to 10 mV and a measurement frequency range of 1 Hz to 3 MHz.

[0166] In addition, ionic conductivity was measured using the composite solid electrolyte membrane of Example 2 and the solid electrolyte membrane of Comparative Example 1 instead of the composite solid electrolyte membrane of Example 1, and the results are shown in Table 1 and Figure 7 below.

[0167]

[0168] Resistance Ionic Conductivity Example 13.73 Ω 2.01 mS / cm Example 23.09 Ω 2.23 mS / cm Comparative Example 14.7 Ω 1.44 mS / cm

[0169] The composite solid electrolyte membranes of Examples 1 and 2 showed lower resistance and higher ionic conductivity than the solid electrolyte membrane of Comparative Example 1. The composite solid electrolyte membranes of Examples 1 and 2 had ionic liquids impregnated into the pores formed in the solid electrolyte membrane, and as the ionic liquids were impregnated into the pores, they could provide additional migration paths without obstructing the path of lithium ions, thereby showing high ionic conductivity. On the other hand, the solid electrolyte membrane of Comparative Example 1 did not impregnate the pores with ionic liquids, and therefore, it was found that the pores obstructed the migration path of lithium ions, resulting in lower ionic conductivity than Examples 1 and 2.

Claims

1. A solid electrolyte membrane comprising a solid electrolyte and a binder; and A composite solid electrolyte membrane comprising an ionic liquid, The above solid electrolyte membrane includes a plurality of pores, The above ionic liquid is impregnated into the plurality of pores, The anion of the above ionic liquid is (CF3SO2)2N - In, composite solid electrolyte membrane.

2. In paragraph 1, A composite solid electrolyte membrane, wherein the cation of the ionic liquid is at least one selected from the group consisting of pyrrolidinium, piperidinium, imidazolium, phosphonium, ammonium, and pyridinium.

3. In paragraph 1, A composite solid electrolyte membrane, wherein the ionic liquid is contained in an amount of 3 to 50 parts by weight per 100 parts by weight of the solid electrolyte.

4. In paragraph 1, A composite solid electrolyte membrane, wherein the total volume of the plurality of pores is 1 to 50% by volume with respect to the total volume of the solid electrolyte membrane.

5. In paragraph 4, A composite solid electrolyte membrane, wherein the ionic liquid is impregnated at 80 to 100 volume% of the pore volume of the solid electrolyte membrane.

6. In paragraph 1, The above solid electrolyte is a composite solid electrolyte membrane that is a sulfide-based solid electrolyte.

7. In paragraph 1, A composite solid electrolyte membrane having a thickness of 10 to 200 μm. 8.(1) A step of manufacturing a solid electrolyte membrane including a plurality of pores using a mixture including a solid electrolyte and a binder; and (2) A step of impregnating an ionic liquid into a solid electrolyte membrane including the plurality of pores; The anion of the above ionic liquid is (CF3SO2)2N - A method for manufacturing a composite solid electrolyte membrane according to claim 1.

9. In paragraph 8, A method for manufacturing a composite solid electrolyte membrane, wherein the ionic liquid is impregnated into a plurality of pores of the solid electrolyte membrane.

10. An all-solid-state battery comprising a positive electrode, a negative electrode, and a solid electrolyte membrane interposed between them, An all-solid-state battery, wherein the above solid electrolyte membrane is a composite solid electrolyte membrane of claim 1.

Images