Composite solid electrolyte for lithium secondary batteries and method for manufacturing the same

Abstract

The present specification relates to a composite solid electrolyte for a lithium secondary battery and a method for producing the same.

Description

[Technical Field] 【0001】 This application claims priority rights under Korean Patent Application No. 10-2022-0067022 dated May 31, 2022, and Korean Patent Application No. 10-2023-0070203 dated May 31, 2023, and incorporates all the contents disclosed in the documents of said Korean Patent Applications as part of this Specification. 【0002】 The present invention relates to a composite solid electrolyte for lithium secondary batteries and a method for producing the same. [Background technology] 【0003】 Lithium-ion batteries, which use liquid electrolytes, have a structure in which the negative and positive electrodes are separated by a separator membrane. If the separator membrane is damaged due to deformation or external impact, a short circuit can occur, which can lead to dangers such as overheating or explosion. Therefore, the development of solid electrolytes that can ensure safety in the field of lithium-ion secondary batteries is a very important issue. 【0004】 Lithium-ion batteries using solid electrolytes offer several advantages: increased battery safety, prevention of electrolyte leakage, improved battery reliability, and the ease of manufacturing thin batteries. Furthermore, the use of lithium metal in the negative electrode allows for increased energy density, making them promising for applications in small secondary batteries as well as high-capacity secondary batteries for electric vehicles, and attracting attention as a next-generation battery. 【0005】 Among solid electrolytes, polymer solid electrolytes can utilize polymer materials with ion-conducting properties, or inorganic materials such as oxides or sulfides with ion-conducting characteristics. Composite solid electrolytes, which are mixtures of polymer and inorganic materials, have also been proposed. 【0006】 Such conventional composite solid electrolytes are manufactured by producing a solution or slurry in which polymers and inorganic substances are mixed and dispersed, and then subjecting the solution to solution casting on a substrate and a high-temperature drying process. However, in the manufacturing technology of conventional composite solid electrolytes, since the uniform dispersion of inorganic substances in the polymer solution is not smooth, a non-uniform distribution of inorganic particles is formed in the composite solid electrolyte, making it difficult to manufacture a composite solid electrolyte with improved ionic conductivity. 【0007】 In order to overcome such limitations of conventional composite solid electrolytes, there is a need for the development of a technology in which polymers and inorganic substances are uniformly dispersed, enabling the improvement of the ionic conductivity of the composite solid electrolyte containing them. 【Prior Art Documents】 【Patent Documents】 【0008】 【Patent Document 1】 Korean Patent Publication No. 2017-0045011 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0009】 An object of the present invention is to provide a composite solid electrolyte with improved ionic conductivity. 【0010】 Another object of the present invention is to provide a method for manufacturing a composite solid electrolyte with improved ionic conductivity. 【0011】 Another object of the present invention is to provide a all-solid-state battery including a composite solid electrolyte with improved ionic conductivity. 【Means for Solving the Problems】 【0012】 To achieve the above objective, the present invention provides a method for producing a composite solid electrolyte for a lithium secondary battery, comprising the steps of: (S1) applying a composite solid electrolyte forming solution containing a first polymer, which is a UV-curable polymer, and a ceramic compound onto a substrate to form a coating film; (S2) irradiating the coating film with ultraviolet light (UV) and then curing it to produce a first composite; (S3) sintering the first composite to produce a ceramic ion conductor; and (S4) immersing the ceramic ion conductor in a solution containing a second polymer and a lithium salt and curing it to produce a second composite. 【0013】 The present invention also provides a composite solid electrolyte for lithium secondary batteries, comprising a ceramic ion conductor containing a ceramic compound; a second polymer; and a lithium salt, wherein the ceramic ion conductor includes a cross-linked bonding structure containing the ceramic compound. 【0014】 The present invention also provides an all-solid-state battery comprising the composite solid electrolyte for lithium secondary batteries. [Effects of the Invention] 【0015】 The composite solid electrolyte according to the present invention can effectively improve lithium ion conduction by forming a ceramic ion conductor using a first polymer, which is a UV-curable polymer, and a ceramic compound. [Modes for carrying out the invention] 【0016】 The present invention will be described in more detail below to aid in understanding the invention. 【0017】 The terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner and concept consistent with the technical idea of ​​the present invention, based on the principle that inventors may appropriately define the concepts of terms in order to best describe their inventions. 【0018】 Method for manufacturing a composite solid electrolyte for lithium secondary batteries A method for producing a composite solid electrolyte according to one embodiment of the present invention may include the following steps: (S1) A step of forming a coating film by applying a composite solid electrolyte-forming solution containing a first polymer, which is a UV-curable polymer, and a ceramic compound onto a substrate; (S2) The step of irradiating the coated film with ultraviolet (UV) light and then curing it to produce the first composite; (S3) The step of sintering the first composite to produce a ceramic ion conductor; (S4) The step of immersing the ceramic ion conductor in a solution containing a second polymer and a lithium salt and curing it to produce a second composite. 【0019】 Conventional composite solid electrolytes were manufactured by coating a substrate with a solution or slurry containing a mixture of polymers and inorganic materials, and then drying it using methods such as solution casting. However, this method had the problem that the ionic conductivity of the solid electrolyte was not improved due to the non-uniform dispersion and precipitation of inorganic materials within the polymer solution. 【0020】 To improve this, the inventors have created a composite solid electrolyte in which particles of the ceramic compound are uniformly dispersed in a ceramic ion conductor manufactured using a first polymer, which is a UV-curable polymer, and a ceramic compound, thereby improving ionic conductivity. 【0021】 In the method for producing the composite solid electrolyte, the first composite is produced by irradiating a solution containing a first polymer, which is a UV-curable polymer, and a ceramic compound with ultraviolet light, and then curing it, thereby uniformly dispersing the ceramic compound in the first polymer solution. By producing a ceramic ion conductor in which the ceramic compound particles are uniformly dispersed, the ion conduction of lithium ions can be improved, and a composite solid electrolyte with improved ionic conductivity can be produced. 【0022】 The method for producing the composite solid electrolyte according to the present invention will be described in more detail below, step by step. 【0023】 In the present invention, in step (S1), a composite solid electrolyte forming solution containing a first polymer, which is a UV-curable polymer, and a ceramic compound can be applied to a substrate to form a coated film. 【0024】 The first polymer may be a UV-curable polymer. The UV-curable polymer refers to a polymer that forms photocrosslinks using ultraviolet (UV) light. When the UV-curable polymer is irradiated with ultraviolet (UV) light in the presence of a photoinitiator, a photopolymerization reaction is initiated, and photocrosslinks can be formed. Therefore, the UV-curable polymer may have the property of exhibiting maximum absorbance in at least a portion of the wavelength range or the entire range of the ultraviolet (e.g., wavelengths from 300 nm to 400 nm) region in its absorbance spectrum with respect to wavelength. 【0025】 The first polymer may contain one or more selected from the group consisting of polyisocyanurate (PIR), epoxy, polyurethane, polyacrylate, and poly(methyl methacrylate, PMMA). 【0026】 Examples of UV-curable acrylate monomers in the aforementioned polyacrylate include hexanediol diacrylate (HDDA), tripropylene glycol diacrylate (TPGDA), ethylene glycol diacrylate (EGDA), trimethylolpropane triacrylate (TMPTA), trimethylolpropane ethoxylated triacrylate (TMPEOTA), glycerol propoxylated triacrylate (GPTA), pentaerythritol tetraacrylate (PETA), and dipentaerythritol hexaacrylate (DPHA). However, the polyacrylate is not limited to these examples, and any acrylate monomer commonly used in this field can be used without particular restriction. 【0027】 The composite solid electrolyte forming solution may further contain a photopolymerization initiator. Examples of the photopolymerization initiator include, but are not limited to, 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]2-methyl-1-propanone, methylbenzoyl formate, α,α-dimethoxy-α-phenylacetophenone, 2-benzoyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone, 2-methyl-1-[4[(methylthio)phenyl]-2(4-morpholinyl)-1-propanone diphenyl(2,4,6-trimethylbenzoyl)-phosphine oxide, or bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide. Furthermore, commercially available photopolymerization initiators such as Irgacure 184, Irgacure 500, Irgacure 651, Irgacure 369, Irgacure 907, Darocur 1173, Darocur MBF, Irgacure 819, Darocur TPO, and Esacure KIP 100F can be used. The photopolymerization initiators can be used alone or in mixtures of two or more different types. 【0028】 The content of the photoinitiator may be 1.0 to 5.0% by weight based on the content of the first polymer. If the content of the photoinitiator is less than 1.0% by weight or more than 5.0% by weight based on the content of the first polymer, crosslinking between the first polymer and the ceramic compound may not be formed, making it difficult to form a crosslinked film. 【0029】 The ceramic compound may be an oxide-based or phosphate-based solid electrolyte. The oxide-based or phosphate-based solid electrolyte may be a garnet-type lithium-lanthanum-zirconium oxide system (LLZO,Li7La3Zr2O 12 ), perovskite-type lithium-lanthanum-titanium oxide system (LLTO, Li 3x La 2 / 3-xTiO3), phosphate-based NASICON-type lithium-aluminum-titanium phosphate system (LATP, Li 1+x Al x Ti 2-x (PO4)3), lithium-aluminum-germanium phosphate system (LAGP, Li 1.5 Al 0.5 Ge 1.5 (PO4)3), lithium-silicon-titanium phosphate system (LSTP, LiSiO2TiO2(PO4)3) and lithium-lanthanum-zirconium-titanium oxide system (LLZTO) compounds, and one or more may be selected from the group consisting of. Since the oxide-based or phosphate-based solid electrolyte has a very high grain boundary resistance, a sintering process is required at 1000 °C or higher. This causes problems such as lithium volatilization problems, phase transitions, and impurity phase formation at high temperatures. However, oxide-based or phosphate-based solid electrolytes generally have a maximum ionic conductivity value of 10 -4 ~10 -3 S / cm at room temperature, are stable in the high voltage region, and have the advantages of being stable in air and easy to synthesize and handle. 【0030】 Therefore, by mixing the first polymer according to the present invention with a different substance and manufacturing a hybrid solid electrolyte, the drawbacks of each material can be complemented. 【0031】 The oxide-based or phosphate-based solid electrolyte does not easily burn or cause ignition even under high temperature conditions of 400 °C or higher, so it has high thermal stability. Therefore, when the ceramic ion conductor contains the oxide-based or phosphate-based solid electrolyte, it can improve not only the mechanical strength of the composite solid electrolyte for lithium secondary batteries but also the thermal stability and ionic conductivity. 【0032】 The substrate is not particularly limited as long as it can serve as a support to which the composite solid electrolyte forming solution is applied. For example, the substrate may be stainless steel (SS), 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. 【0033】 Furthermore, the coating method is not particularly limited as long as it is a method that can coat the composite solid electrolyte forming solution onto the substrate in the form of a film. For example, 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. 【0034】 In the present invention, in step (S2), the coated film can be irradiated with ultraviolet light (UV) and then cured to produce the first composite. 【0035】 Conventional composite solid electrolytes are manufactured by first preparing a solution by mixing and dispersing polymers and inorganic materials, then coating the solution onto a substrate using methods such as solution casting, and finally producing a composite solid electrolyte film through a drying process. However, such composite solid electrolytes have problems such as the inorganic materials not being uniformly dispersed in the polymer solution, resulting in a non-uniform distribution of inorganic particles in the final composite solid electrolyte film, low ionic conductivity, and long manufacturing times. 【0036】 Therefore, the inventors have used the first polymer, which is a UV-curable polymer, to enable uniform dispersion of the ceramic compound particles within the first composite through UV curing in a short time, thereby completing a composite solid electrolyte with improved ionic conductivity. 【0037】 The wavelength of ultraviolet (UV) light used in the curing reaction may be between 200 and 400 nm. 【0038】 In the first composite, the ceramic compound may be present in amounts of 1 part by weight or more but less than 10 parts by weight per 1 part by weight of the first polymer. More specifically, the weight ratio of the first polymer to the ceramic compound may be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, or 1:9. If the ceramic compound is present in amounts of less than 1 part by weight per 1 part by weight of the first polymer, after the sintering process in step (S4) below, the bonding between the ceramic compounds does not occur smoothly, making it difficult to form a cross-linked ceramic ion conductor structure. Furthermore, the mechanical properties are also weak, easily crumbling or breaking, and there is a problem in that the composite solid electrolyte cannot be manufactured. Moreover, if the ceramic compound is present in amounts exceeding 10 parts by weight per 1 part by weight of the first polymer, the ceramic compound is not uniformly dispersed within the first polymer, and a phenomenon of aggregation occurs where the ceramic compound particles clump together. This leads to phase separation between the first polymer and the aggregated ceramic compound particles, resulting in the production of a composite solid electrolyte with reduced ionic conductivity. 【0039】 In the present invention, in step (S3), the first composite can be sintered to produce a ceramic ion conductor. 【0040】 Here, sintering refers to the process of applying sufficient temperature and pressure to create a harder aggregate of particles from the first composite. 【0041】 The ceramic ion conductor can be manufactured by sintering the first composite to thermally decompose the components of the first polymer, and then sintering the remaining ceramic compound particles. 【0042】 After the sintering process, the first polymer acts as a support so that the particles of the ceramic compound can be linked together, and the particles of the ceramic compound can be linked together to form a ceramic ion conductor having a single cross-linked bonding structure. 【0043】 The ceramic ion conductor can play a role in forming an ion conduction path for lithium ions. 【0044】 The sintering can be carried out by appropriately selecting conditions that allow the components of the first polymer to thermally decompose, causing the ceramic compound particles to link together and form an ion conductor with a cross-linked structure. For example, the sintering temperature can be 800°C to 1300°C, and specifically, the sintering temperature may be 850°C or higher, 900°C or higher, 950°C or higher, or 1300°C or lower, 1250°C or lower, or 1200°C or lower. 【0045】 In the present invention, in step (S4), the ceramic ion conductor can be immersed in and cured in a solution containing the second polymer and a lithium salt to produce the second composite. 【0046】 The second composite can be used to produce a composite solid electrolyte with improved ionic conductivity by including the ceramic ion conductor. 【0047】 The second polymer exhibits excellent solubility and dissociation of lithium salts, and when the second polymer and lithium salt are mixed, there are no side reactions with the ceramic compound. The polymer solution penetrates well into the ceramic ion conductor, making it a polymer that facilitates the production of the final composite solid electrolyte. Specific examples of the second polymer include polyvinyl alcohol (PVA), polyethylene oxide (PEO), polyacrylate, poly(methyl methacrylate, PMMA), poly(4-styrenesulfonyl(trifluoromethylsulfonyl)imide (PSTFSI), polyurethane, nylon, poly(dimethylsiloxane), gelatin, methylcellulose, agar, dextrin, poly(vinylpyrrolidone), poly(acrylamide), poly(acrylic acid), starch-carboxymethylcellulose, and hyaluronic acid-methylcellulose. It may also contain one or more selected from the group consisting of acid-methylcellulose, chitosan, poly(N-isopropylacrylamide), and amino-terminated polyethylene glycol (amino-terminated PEG). 【0048】 In the present invention, the lithium salt is contained in a dissociated state within the structure formed by the ceramic ion conductor, thereby improving the ionic conductivity of the composite solid electrolyte. Furthermore, the lithium salt is mainly dissociated within the second polymer, and in step (S3), it can play a role in compensating for the loss of lithium ions generated from the ceramic compound particles during the high-temperature sintering process. 【0049】 The aforementioned lithium salts are (CF3SO2)2NLi (Lithium bis(trifluoromethanesulfonyl)imide, LiTFSI), (FSO2)2NLi (Lithium bis(fluorosulfonyl)imide, LiFSI), LiNO3, LiOH, LiCl, LiBr, LiI, LiClO4, LiBF4, 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, and LiC(CF3SO2)3. 【0050】 The ceramic ion conductor manufactured in step (S3) can be immersed in or coated with a solution containing the second polymer and lithium salt, and then cured. The immersion or coating and curing can be repeated multiple times. 【0051】 The curing in step (S4) above can be thermal curing or UV curing. 【0052】 The UV curing process is as described above. 【0053】 The aforementioned thermosetting step allows for the production of a second composite having ion conductivity while the ceramic ion conductor is immersed in a solution containing the second polymer and lithium salt and the curing process is carried out. 【0054】 The thermosetting step may, but is not limited to, be carried out at 50°C to 150°C. For example, the thermosetting step may, but is not limited to, being carried out at 50°C to 150°C, 60°C to 150°C, 70°C to 150°C, 80°C to 150°C, 90°C to 150°C, 100°C to 150°C, 50°C to 140°C, 50°C to 130°C, 50°C to 120°C, 50°C to 110°C, or 50°C to 100°C. If the thermosetting step is carried out below the temperature range, the formation of the second composite may be incomplete, and if it is carried out above the temperature range, the thermal decomposition of the second polymer and lithium salt may make it difficult to produce the composite solid electrolyte. 【0055】 The molar concentration ([G]) of the second polymer and the molar ratio ([Li] / [G]) of lithium ([Li]) in the lithium salt may be between 0.1 and 0.5, specifically, 0.1 or more, 0.2 or more, or 0.3 or more, and may be 0.4 or less, or 0.5 or less. If the molar ratio ([Li] / [G]) is less than 0.1, the lithium salt content decreases, which may lower the ionic conductivity of the composite solid electrolyte. If the molar ratio ([Li] / [G]) exceeds 0.5, the ionic conductivity may decrease due to lithium ion aggregation. Therefore, the composite solid electrolyte according to the present invention requires the second polymer and an appropriate amount of lithium salt in the composition of the second composite. 【0056】 Composite solid electrolyte for lithium secondary batteries The composite solid electrolyte for lithium secondary batteries according to the present invention comprises a ceramic ion conductor containing a ceramic compound; a second polymer; and a lithium salt; wherein the ceramic ion conductor may include a cross-linked bonding structure containing the ceramic compound. 【0057】 Conventional composite solid electrolytes were manufactured by coating a substrate with a solution or slurry containing a mixture of polymers and inorganic materials, using methods such as solution casting, and then drying the mixture. However, this method had the problem that the ionic conductivity of the solid electrolyte was not improved due to the non-uniform dispersion and precipitation of inorganic materials within the polymer solution. 【0058】 To improve this, the present invention aims to provide a composite solid electrolyte comprising a ceramic ion conductor, a polymer, and a lithium salt, which include a cross-linking structure that forms an ion conduction path for lithium ions. The ceramic ion conductor has ceramic compound particles uniformly dispersed inside it and can play a role in improving the ionic conductivity of the composite solid electrolyte. 【0059】 In one embodiment of the present invention, the ceramic ion conductor may include a crosslinked bonding structure comprising the ceramic compound. 【0060】 The ceramic ion conductor may include a single cross-linking structure formed by the interconnection of particles of the ceramic compound. The first polymer acts as a support, enabling the particles of the ceramic compound to connect with one another. 【0061】 The ceramic ion conductor can play a role in forming an ion conduction path for lithium ions. 【0062】 The specific method for manufacturing the aforementioned ceramic ion conductor is as described above. 【0063】 The first polymer may contain one or more selected from the group consisting of polyisocyanurate (PIR), epoxy, polyurethane, polyacrylate, and poly(methyl methacrylate, PMMA). 【0064】 Examples of UV-curable acrylate monomers in the aforementioned polyacrylate include hexanediol diacrylate (HDDA), tripropylene glycol diacrylate (TPGDA), ethylene glycol diacrylate (EGDA), trimethylolpropane triacrylate (TMPTA), trimethylolpropane ethoxylated triacrylate (TMPEOTA), glycerol propoxylated triacrylate (GPTA), pentaerythritol tetraacrylate (PETA), and dipentaerythritol hexaacrylate (DPHA). However, the polyacrylate is not limited to these examples, and any acrylate monomer commonly used in this field can be used without particular restriction. 【0065】 The ceramic compound may be an oxide-based or phosphate-based solid electrolyte. The oxide-based or phosphate-based solid electrolyte may be a garnet-type lithium-lanthanum-zirconium oxide system (LLZO,Li7La3Zr2O 12 ), perovskite-type lithium-lanthanum-titanium oxide system (LLTO, Li 3x La 2 / 3-x TiO3), phosphate-based NASICON type lithium aluminum titanium phosphate (LATP, Li 1+x Al x Ti 2-x (PO4)3), Lithium-aluminum-germanium phosphate system (LAGP,Li 1.5 Al 0.5 Ge 1.5One or more compounds may be selected from the group consisting of (PO4)3), lithium-silicon-titanium phosphate (LSTP, LiSiO2TiO2(PO4)3), and lithium-lanthanum-zirconium-titanium oxide (LLZTO) compounds. The oxide-based or phosphate-based solid electrolytes have very high grain boundary resistance, requiring a sintering process at 1000°C or higher. This results in problems such as lithium volatilization at high temperatures, phase transitions, and impurity phase formation. However, oxide-based or phosphate-based solid electrolytes generally have a maximum temperature of 10°C at room temperature. -4 ~10 -3 It has an ionic conductivity value of S / cm, is stable in the high-voltage range, is stable in air, and has the advantages of being easy to synthesize and handle. Therefore, by mixing the first polymer according to the present invention with other materials to produce a hybrid solid electrolyte, the shortcomings of each material can be compensated for. 【0066】 In one embodiment of the present invention, the composite solid electrolyte for the lithium secondary battery may include a ceramic ion conductor; a second polymer; and a lithium salt. 【0067】 The ceramic ion conductor is as described above. 【0068】 The second polymer exhibits excellent solubility and dissociation of lithium salts, and when the second polymer and lithium salt are mixed, there are no side reactions with the ceramic compound. The polymer solution penetrates well into the ceramic ion conductor, making it a polymer that facilitates the production of the final composite solid electrolyte. Specific examples of the second polymer include polyvinyl alcohol (PVA), polyethylene oxide (PEO), polyacrylate, poly(methyl methacrylate, PMMA), poly(4-styrenesulfonyl(trifluoromethylsulfonyl)imide (PSTFSI), polyurethane, nylon, poly(dimethylsiloxane), gelatin, methylcellulose, agar, dextrin, poly(vinylpyrrolidone), poly(acrylamide), poly(acrylic acid), starch-carboxymethylcellulose, and hyaluronic acid-methylcellulose. It may also contain one or more selected from the group consisting of acid-methylcellulose, chitosan, poly(N-isopropylacrylamide), and amino-terminated polyethylene glycol (amino-terminated PEG). 【0069】 In the present invention, the lithium salt is contained in a dissociated state within the structure formed by the ceramic ion conductor, thereby improving the ionic conductivity of the composite solid electrolyte. 【0070】 The aforementioned lithium salts are (CF3SO2)2NLi (Lithium bis(trifluoromethanesulfonyl)imide, LiTFSI), (FSO2)2NLi (Lithium bis(fluorosulfonyl)imide, LiFSI), LiNO3, LiOH, LiCl, LiBr, LiI, LiClO4, LiBF4, 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, and LiC(CF3SO2)3. 【0071】 The molar concentration ([G]) of the second polymer and the molar ratio ([Li] / [G]) of lithium ([Li]) in the lithium salt may be between 0.1 and 0.5, specifically, 0.1 or more, 0.2 or more, or 0.3 or more, and may be 0.4 or less, or 0.5 or less. If the molar ratio ([Li] / [G]) is less than 0.1, the lithium salt content decreases, which may lower the ionic conductivity of the composite solid electrolyte. If the molar ratio ([Li] / [G]) exceeds 0.5, the ionic conductivity may decrease due to lithium ion aggregation. Therefore, the composite solid electrolyte according to the present invention requires the second polymer and an appropriate amount of lithium salt in the composition of the second composite. 【0072】 In the present invention, the composite solid electrolyte may be in the form of a free-standing film. The free-standing film refers to a film that can maintain its film form on its own at room temperature and pressure without the need for a separate support. 【0073】 The aforementioned freestanding film exhibits elasticity, minimizes brittleness, and possesses the properties of a support that stably contains lithium ions, making it a suitable form for use as a composite solid electrolyte. 【0074】 In the present invention, the ionic conductivity of the composite solid electrolyte is 10 -5 It may be S / cm or higher. 【0075】 As mentioned above, despite being a solid electrolyte, the composite solid electrolyte exhibits ionic conductivity at a level equivalent to or higher than that of conventional liquid electrolytes, thereby improving the performance of all-solid-state batteries. 【0076】 All solid state battery The present invention also relates to an all-solid-state battery comprising a composite solid electrolyte, wherein the all-solid-state battery comprises a negative electrode, a positive electrode, and a composite solid electrolyte interposed between the negative electrode and the positive electrode, and the composite solid electrolyte has the characteristics described above. 【0077】 Specifically, the composite solid electrolyte includes a ceramic ion conductor, which improves the ion conduction of lithium ions, making it suitable as an electrolyte for all-solid-state batteries. 【0078】 In the present invention, the positive electrode included in the all-solid-state battery includes a positive electrode active material layer, and the positive electrode active material layer may be formed on one surface of the positive electrode current collector. 【0079】 The positive electrode active material layer comprises a positive electrode active material, a binder, and a conductive material. 【0080】 Furthermore, the positive electrode active material is not particularly limited as long as it is a material capable of reversibly intercalating and releasing 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 one 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 b-a-b’ M'b’ )O 2-c A c (In 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.) A layered compound such as the above, or a compound substituted with one or more transition metals; chemical formula Li 1+y Mn 2-y Lithium manganese oxides such as O4 (where y is 0-0.33), 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 = 0.01-0.3); chemical formula LiMn 2-y M y Examples include, but are not limited to, lithium manganese composite oxides represented as O2 (where M = Co, Ni, Fe, Cr, Zn, or Ta, and y = 0.01-0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu, or Zn); LiMn2O4 in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion; disulfide compounds; Fe2(MoO4)3, etc. 【0081】 Furthermore, the positive electrode active material may be present 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, 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 connectivity between the wet positive electrode active material layer and the dry positive electrode active material layer may be insufficient, and if it exceeds 80% by weight, the mass transfer resistance may increase. 【0082】 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, polyphosphazene, and polyacrylic acid. The binder may contain one or more selected from the group consisting of lilonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethylcellulose, hydroxypropylcellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethyl scrophulari, 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 contain one or more selected from the group consisting of styrene-butadiene rubber, polytetrafluoroethylene, carboxymethylcellulose, polyacrylic acid, lithium polyacrylate, and polyvinylidene fluoride. 【0083】 Furthermore, the binder may be present 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 improves, but the content of the positive electrode active material decreases accordingly, which may reduce the battery capacity. 【0084】 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, does not induce chemical changes in the battery, and has excellent electrical conductivity. Typically, graphite or conductive carbon can be used, for example: graphite such as natural graphite or 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; 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. These can be used individually or in combination of two or more, but are not necessarily limited to these. 【0085】 The conductive material may typically be present 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, 1% or more by weight, 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, and the capacity and energy density may decrease. The method for incorporating the conductive material into the positive electrode is not significantly limited, and conventional methods known in the art, such as coating the positive electrode active material, can be used. 【0086】 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. 【0087】 The positive electrode current collector is not particularly limited as long as it does not induce chemical changes 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., and aluminum-cadmium alloy can be used as the positive electrode current collector. 【0088】 The positive electrode current collector may have a fine uneven surface or a three-dimensional porous structure to enhance the bonding force with the positive electrode active material layer. As a result, the positive electrode current collector can take various forms such as film, sheet, foil, mesh, net, porous material, foam, or nonwoven fabric. 【0089】 The positive electrode described above can be manufactured according to 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 compressing the current collector to improve electrode density. In this case, it is desirable 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. 【0090】 In the present invention, the negative electrode included in the all-solid-state battery includes a negative electrode active material layer, and the negative electrode active material layer may be formed on one surface of the negative electrode current collector. 【0091】 The 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. 【0092】 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 nitrate, or silicon. 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). 【0093】 Preferably, the negative electrode active material may be lithium metal, and more specifically, it may be in the form of a lithium metal thin film or lithium metal powder. 【0094】 The negative electrode active material may be present 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% by weight or more, or 50% by weight or more, or 70% by weight or less, or 80% by weight or less. If the content of the negative electrode active material is less than 40% by weight, the connectivity between the wet negative electrode active material layer and the dry negative electrode active material layer may be insufficient, and if it exceeds 80% by weight, the mass transfer resistance may increase. 【0095】 Furthermore, the binder is as described above in the positive electrode active material layer. 【0096】 Furthermore, the conductive material is as described above in the positive electrode active material layer. 【0097】 Furthermore, the negative electrode current collector is not particularly limited as long as it does not induce a chemical change in the battery and is conductive. 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, similar to 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. 【0098】 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 a layer or film formation method commonly used in the industry. For example, methods such as crimping, coating, and vapor deposition can be used. Furthermore, the negative electrode of the present invention is also included in the case where a metallic lithium thin film is formed on a metal plate by initial charging after the battery has been assembled without a lithium thin film on the negative electrode current collector. 【0099】 Furthermore, the present invention provides a battery module including the all-solid-state battery as a unit battery, a battery pack including the battery module, and a device including the battery pack as a power source. 【0100】 Specific examples of the aforementioned devices include, but are not limited to, power tools powered by battery-powered motors; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters; electric golf carts; and power storage systems. Preferred embodiments are shown below to aid in understanding the present invention, but these embodiments are 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 such changes and modifications will naturally fall within the scope of the attached claims. 【0101】 The following are preferred embodiments to aid in understanding the present invention, but these embodiments are provided to make the present invention easier to understand and are not limited thereto. 【0102】 In the following examples and comparative examples, ceramic ion conductors containing polymers, ceramic compounds, etc., as shown in Table 1 were manufactured, and composite solid electrolytes containing these were produced. 【0103】 [Table 1] 【0104】 Example 1: Production of a composite solid electrolyte (1) Manufacturing of the first complex A solution containing thiol-ene polyisocyanurate (PIR) and LLZO powder, a ceramic compound, was prepared. 1% by weight of 2-hydroxy-2-methyl-1-phenyl-1-propanone was added to the solution as a photoinitiator. The weight ratio of PIR to LLZO was 1:2. 【0105】 The aforementioned solution was applied to a substrate, SS foil, by a bar coating method, then irradiated with ultraviolet (UV) light and cured to induce cross-linking of PIR, thereby producing a network-shaped composite. 【0106】 (2) Manufacturing of ceramic ion conductors The composite was separated from the substrate, heated from room temperature to 800°C at a rate of 1°C / min, and then sintered at 800°C for 2 hours to thermally decompose the PIR components. A ceramic ion conductor was then produced by sintering the remaining LLZO particles. 【0107】 (3) Manufacturing of complex solid electrolytes A solution containing PVA and LiTFSI was prepared (where the molar ratio of "O" in PVA and "Li" in the lithium salt ([Li] / [O]) was 0.4), the ceramic ion conductor was immersed in the prepared solution, dried at room temperature for 12 hours, and then dried in a vacuum drying oven at 100°C for 12 hours to completely remove the residual solvent, after which a composite solid electrolyte was produced. 【0108】 Example 2 A composite solid electrolyte was prepared in the same manner as in Example 1, except that LSTP was used instead of the ceramic compound LLZO. 【0109】 Example 3 A composite solid electrolyte was prepared in the same manner as in Example 1, except that the weight ratio of the UV-curable polymer (PIR) and the ceramic compound (LLZO) was 1:10. 【0110】 Example 4 A composite solid electrolyte was prepared in the same manner as in Example 1, except that the weight ratio of UV-curable polymer (PIR) and ceramic compound (LLZO) was 10:1. 【0111】 Example 5 A composite solid electrolyte was prepared in the same manner as in Example 1, except that the photoinitiator content was 0.1% by weight. 【0112】 Example 6 A composite solid electrolyte was prepared in the same manner as in Example 1, except that a photoinitiator content of 0.4% by weight was used. 【0113】 Example 7 A composite solid electrolyte was prepared in the same manner as in Example 1, except that the molar ratio ([Li] / [O]) of "O" in PVA and "Li" in the lithium salt was 0.08. 【0114】 Example 8 A composite solid electrolyte was prepared in the same manner as in Example 1, except that the molar ratio ([Li] / [O]) of "O" in PVA and "Li" in the lithium salt was 0.52. 【0115】 Example 9 A composite solid electrolyte was prepared in the same manner as in Example 1, except that PEO was used instead of polymer PVA. 【0116】 Example 10 A composite solid electrolyte was prepared in the same manner as in Example 1, except that PIR was used instead of polymer PVA. 【0117】 Comparative Example 1 A composite solid electrolyte was manufactured in the same manner as in Example 1, except that the post-sintering step was omitted after the composite fabrication. 【0118】 Comparative Example 2 A composite solid electrolyte was manufactured in the same manner as in Comparative Example 2, except that instead of curing after irradiation with ultraviolet (UV) light, it was dried at 80°C for 2 hours. 【0119】 Experimental example Experimental Example 1 To measure the ionic conductivity of the composite solid electrolytes in film form produced in the examples and comparative examples, 1.7671 cm² was used. 2 The composite solid electrolyte was punched out in a circular shape, and the punched-out composite solid electrolyte was placed between two sheets of stainless steel (SS) to manufacture a coin cell. 【0120】 Using an electrochemical impedance spectrometer (EIS, VM3, Bio Logic Science Instrument), the resistance was measured at 25°C with an amplitude of 10mV and a scan range of 500kHz to 20MHz. The ionic conductivity of the composite solid electrolyte was then calculated using Equation 1 below. 【0121】 [Formula 1] 【number】 【0122】 In the above formula 1, σ i R is the ionic conductivity (S / cm) of the composite solid electrolyte, R is the resistance (Ω) of the composite solid electrolyte measured by the electrochemical impedance spectrometer, L is the thickness (μm) of the composite solid electrolyte, and A is the area (cm²) of the composite solid electrolyte. 2 ) means. 【0123】 The ionic conductivity of the composite solid electrolyte calculated using Equation 1, the feasibility of hydrogel formation, the feasibility of freestanding film formation, and the results of observing the appearance of the composite solid electrolyte are shown in Table 2 below. At this time, the feasibility of freestanding film formation (formed: O, not formed: X) and the appearance of the composite solid electrolyte were observed with the naked eye. 【0124】 [Table 2] 【0125】 As shown in Table 2 above, it was confirmed that a ceramic ion conductor can be formed by applying a sintering process after curing a solution obtained by mixing the first polymer, which is a UV-curable polymer, and a ceramic compound in an appropriate weight ratio, and then applying a sintering process (Examples 1-10). 【0126】 In Examples 3 and 4, it was confirmed that ceramic ion conductors were not formed when the weight ratio of the first polymer, which is a UV-curable polymer, to the ceramic compound was greater than 1:10 or less than 10:1. Therefore, it was confirmed that in order to form the ceramic ion conductor according to the present invention, the weight ratio of the first polymer and the ceramic compound must be within an appropriate range. 【0127】 In Examples 5 and 6, it was confirmed that crosslinked films could not be manufactured without an appropriate amount of photoinitiator. 【0128】 In Examples 7 and 8, it was confirmed that when the concentrations of the second polymer and lithium salt deviated from the range of 0.1 to 0.5 during the production of the composite solid electrolyte, film formation was not possible, and the resulting mixture was unsuitable for the production of the desired composite solid electrolyte. 【0129】 Through Comparative Examples 1 and 2, it was found that even if a UV-curable polymer is used, if UV irradiation and curing are not performed, or if a sintering process is not applied, ceramic ion conductors or crosslinked films cannot be formed. 【0130】 In summary, even though the present invention has been described by limited embodiments and drawings, the present invention is not limited thereto, and various modifications and variations are possible by persons with ordinary skill in the art to which the present invention pertains, within the equivalent scope of the technical concept of the present invention and the claims described below.

Claims

[Claim 1] (S1) A step of forming a coating film by applying a composite solid electrolyte-forming solution containing a first polymer, which is a UV-curable polymer, and a ceramic compound onto a substrate; (S2) The step of irradiating the coated film with ultraviolet light (UV) and then curing it to produce the first composite; (S3) The step of sintering the first composite to produce a ceramic ion conductor; (S4) The step of immersing and curing the ceramic ion conductor in a solution containing a second polymer and a lithium salt to produce a second composite; A method for manufacturing a composite solid electrolyte for lithium secondary batteries. [Claim 2] The method for producing a composite solid electrolyte for a lithium secondary battery according to claim 1, wherein the first polymer comprises one or more selected from the group consisting of polyisocyanurate (PIR), epoxy, polyurethane, polyacrylate, and polymethyl methacrylate (PMMA). [Claim 3] The method for producing a composite solid electrolyte for a lithium secondary battery according to claim 1, wherein the ceramic compound comprises one or more selected from the group consisting of lithium-lanthanum-zirconium oxide (LLZO), lithium-silicon-titanium phosphate (LSTP), lithium-lanthanum-titanium oxide (LLTO), lithium-aluminum-titanium phosphate (LATP), lithium-aluminum-germanium phosphate (LAGP), and lithium-lanthanum-zirconium-titanium oxide (LLZTO) compounds. [Claim 4] The method for producing a composite solid electrolyte for a lithium secondary battery according to claim 1, wherein the ceramic compound is contained in an amount of 1 part by weight or more and less than 10 parts by weight per 1 part by weight of the first polymer. [Claim 5] The second polymer is polyvinyl alcohol (PVA), polyethylene oxide (PEO), polyacrylate, poly(methyl methacrylate) (PMMA), poly(4-styrenesulfonyl(trifluoromethylsulfonyl)imide (PSTFSI), polyurethane, nylon, poly(dimethylsiloxane), gelatin, methylcellulose, agar, dextrin, poly(vinylpyrrolidone) (poly(vinyl A method for producing a composite solid electrolyte for a lithium secondary battery according to claim 1, comprising one or more selected from the group consisting of pyrrolidone), poly(acrylamide), poly(acrylic acid), starch-carboxymethylcellulose, hyaluronic acid-methylcellulose, chitosan, poly(N-isopropylacrylamide), and amino-terminated polyethylene glycol. [Claim 6] The lithium salt is (CF ３ SO ２ ), ２ NLi (lithium bis(trifluoromethanesulfonyl)imide (LiTFSl), (FSO ２ ), ２ NLi (lithium bis(fluorosulfonyl)imide (LiFSI), LiNO ３ , LiOH, LiCl, LiBr, Lil, LiC10 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 and LiC(CF[[ID=4**5]] ３ SO ２ ), ３ The method for producing a composite solid electrolyte for a lithium secondary battery according to claim 1, comprising one or more selected from the group consisting of [Claim 7] The method for producing a composite solid electrolyte for a lithium secondary battery according to claim 1, wherein the molar ratio of lithium ([Li]) of the lithium salt to the molar concentration ([G]) of the second polymer is 0.1 to 0.

5. [Claim 8] The method for producing a composite solid electrolyte for a lithium secondary battery according to claim 1, wherein the composite solid electrolyte for the lithium secondary battery is in the form of a freestanding film. [Claim 9] The ionic conductivity of the composite solid electrolyte for the lithium secondary battery is 1.0 x 10⁻¹⁰ －５ A method for producing a composite solid electrolyte for a lithium secondary battery according to claim 1, wherein the S / cm is 1 or higher.

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