Method for producing composite solid electrolyte and composite solid electrolyte produced therefrom

Abstract

The present invention relates to a method for manufacturing a composite solid electrolyte and a composite solid electrolyte manufactured by the method. The method includes the steps of: (S1) preparing a mixed solution containing a PEO (polyethylene oxide) copolymer having a cross-linking functional group and a ceramic compound; (S2) unwinding a substrate using an unwinder and feeding the substrate to a transport path; (S3) coating the mixed solution on the substrate to form a coating film; (S4) transporting the substrate with the coated film to a drying section and drying it to form a polymer film; (S5) transporting the polymer film to a deposition section and depositing a polar solvent thereon to form a composite solid electrolyte layer; and (S6) winding and recovering the substrate with the composite solid electrolyte layer using a rewinder.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0132766, filed October 14, 2022, and Korean Patent Application No. 10-2023-0136063, filed October 12, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a method for producing a composite solid electrolyte and a composite solid electrolyte produced therefrom. [Background technology]

[0003] Lithium-ion batteries using liquid electrolytes have a structure in which the negative and positive electrodes are separated by a separator, so if the separator is damaged by deformation or external impact, a short circuit may occur, which can lead to risks such as overheating or explosion. Therefore, the development of a solid electrolyte that can ensure safety is a very important issue in the field of lithium-ion secondary batteries.

[0004] Lithium secondary batteries using solid electrolytes have the advantages of increased battery safety, improved reliability due to the ability to prevent electrolyte leakage, and ease of fabrication of thin batteries. Furthermore, lithium metal can be used as the anode, improving energy density. This makes them attractive for applications such as small secondary batteries and high-capacity secondary batteries for electric vehicles, and they are attracting attention as next-generation batteries.

[0005] Among solid electrolytes, polymer solid electrolytes can be made of ion-conductive polymer materials or inorganic materials such as oxides or sulfides having ion-conductive properties. Composite polymer solid electrolytes that combine polymer materials and inorganic materials have also been proposed.

[0006] These conventional composite polymer solid electrolytes are manufactured by dispersing ceramic powders, such as oxides, in a polymer matrix. They offer advantages over conventional liquid electrolytes, such as higher stability and higher ionic conductivity than solid polymer electrolytes. However, they face challenges, such as the need to meet basic prerequisites, such as improving the dispersion of ceramic particles, such as oxides, in the polymer matrix and optimizing the physical properties of the polymer matrix. In particular, it has been difficult to manufacture composite solid electrolytes with improved ionic conductivity using highly crystalline polymers, such as polyethylene oxide (PEO). The high crystallinity of polymers inhibits polymer chain mobility, limiting the mobility of lithium ions within the solid polymer electrolyte, making it difficult to improve the ionic conductivity of solid polymer electrolytes.

[0007] To overcome these limitations of conventional composite solid electrolytes, techniques have been developed to improve the ionic conductivity of composite solid electrolytes by modifying the structure of crystalline polymers or adding a separate plasticizer to the polymer to improve the mobility of polymer chains. However, solid polymer electrolytes manufactured using these polymer structural modifications or plasticizer addition methods can have difficulty improving ionic conductivity above 1 mS / cm.

[0008] Therefore, in addition to polymer solid electrolytes prepared by modifying the polymer structure, adding a separate plasticizer, or immersing a solid electrolyte in a liquid electrolyte, there is a need for technological development of a method for manufacturing a composite solid electrolyte that can improve the ionic conductivity of the electrolyte and can be continuously processed as a pure solid electrolyte for all-solid-state batteries. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 1994-124713 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention provides a method for producing a composite solid electrolyte that can improve ionic conductivity and be a continuous process, and a composite solid electrolyte produced therefrom. [Means for solving the problem]

[0011] Therefore, one embodiment of the present invention provides a method for manufacturing a composite solid electrolyte, including: (S1) preparing a mixed solution containing a PEO (polyethylene oxide) copolymer having a cross-linkable functional group and a ceramic compound; (S2) unwinding a substrate using an unwinder and feeding the substrate to a transport path; (S3) applying the mixed solution to the substrate to form a coating film; (S4) transporting the substrate with the coated film formed thereon to a drying section and drying it to form a polymer film; (S5) transporting the polymer film to a deposition section and depositing a polar solvent thereon to form a composite solid electrolyte layer; and (S6) winding and recovering the substrate with the composite solid electrolyte layer using a rewinder.

[0012] In the above manufacturing method, the mixed solution in step (S1) may further include one or more selected from the group consisting of a lithium salt, a crosslinking agent, and an initiator. Also, the mixed solution may include 10 to 100 parts by weight, or 10 to 60 parts by weight, of the ceramic compound per 100 parts by weight of the PEO (polyethylene oxide)-based copolymer.

[0013] In addition, in the deposition of step (S5), the polar solvent may be evaporated naturally at room temperature or evaporated by heating, so that gas molecules of the polar solvent may be contained on the surface or inside of the polymer chains.

[0014] Meanwhile, in the above-mentioned preparation method, the cross-linkable functional group is bonded to the PEO-based copolymer via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (however, an alkylene linker having 0 carbon atoms represents a single bond), and can be selected from the group consisting of a hydroxyl group, a carboxyl group, an isocyanate group, a nitro group, a cyano group, an amine group, an amide group, an epoxy group, and an allyl group.

[0015] In a more specific example, the PEO (polyethylene oxide) copolymer may be a copolymer containing repeating units of the following chemical formulas 1 to 3: [Chemical formula 1] [ka] [Chemical formula 2] [ka] [Chemical formula 3] [ka] In the above chemical formulas 1 to 3, R1 is -CH2-O-(CH2-CH2-O) k -R3, k is 0 to 20, and R3 represents an alkyl group having 1 to 5 carbon atoms; R2 represents a substituent in which one or more crosslinkable functional groups selected from the group consisting of a hydroxyl group, a carboxyl group, an isocyanate group, a nitro group, a cyano group, an amine group, an amide group, an epoxy group, and an allyl group are bonded to a polymer chain via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (however, an alkylene linker having 0 carbon atoms represents a single bond); l, m, and n are the repeating numbers of the repeating unit, l and n are each independently an integer of 1 to 1,000, and m is an integer of 0 to 1,000.

[0016] In addition, in the manufacturing method, the gas molecules of the polar solvent are polar compounds, and a composite solid electrolyte can be manufactured in which the content of the polar compound is 0.1 wt % or more and less than 10 wt % based on the total weight of the composite solid electrolyte.

[0017] In this case, the polar solvent may include at least one selected from the group consisting of carbonate-based compounds and sulfonyl-based compounds. More specifically, the polar solvent may include at least one selected from the group consisting of ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), and sulfolane.

[0018] Meanwhile, the ceramic compound may include at least one 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.

[0019] In the manufacturing method, steps (S1) to (S6) may be performed consecutively.

[0020] Meanwhile, another embodiment of the present invention provides a composite solid electrolyte prepared by the method of the above-described embodiment. Such a composite solid electrolyte includes a polymer including a PEO-based copolymer having cross-linkable functional groups; a ceramic compound; and a polar compound, wherein at least a portion of the cross-linkable functional groups form cross-links with each other to form a three-dimensional network structure of the polymer, and the polar compound may be contained in the three-dimensional network structure in a gaseous state or may be bonded to the polymer chain. [Effects of the Invention]

[0021] The method for producing a composite solid electrolyte according to the present invention allows the production of a composite solid electrolyte in a continuous process, making mass production possible.

[0022] In addition, the composite solid electrolyte maintains the inherent structural characteristics of the polymer without deformation or destruction of the polymer chains, and improves the mobility of the polymer chains and the uniform distribution of ceramic particles in the composite solid electrolyte, thereby improving the ionic conductivity of the composite solid electrolyte.

[0023] Furthermore, the composite solid electrolyte can exhibit improved ionic conductivity and mechanical properties by containing a trace amount of polar solvent (polar compound) in a gaseous state. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a flowchart of a method for producing a composite solid electrolyte of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, specific embodiments will be described in more detail to facilitate understanding of the invention.

[0026] The terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, in accordance with the principle that an inventor can appropriately define the concept of a term in order to best explain his or her invention.

[0027] The term "polymer film" used in the present invention refers to a film prepared by coating and drying a mixed solution containing a PEO (polyethylene oxide) copolymer containing cross-linkable functional groups and a ceramic compound. Polymer chains containing cross-links due to the cross-linkable functional groups are formed inside the polymer film, and the ceramic compound is dispersed within the internal space of the polymer chains.

[0028] The term "composite solid electrolyte" used in the present invention refers to an electrolyte having a structure in which the polymer film is deposited in a polar solvent and a polar compound, which is a gas molecule of the polar solvent, is contained on the surface or inside of the polymer chain.

[0029] The term "bonding" used herein, in relation to the form in which a polar compound (deposited polar solvent) is "bonded" to a polymer chain, e.g., a PEO-based copolymer chain, broadly refers to a form in which the polar compound in a gaseous state, i.e., the polar solvent molecules, are fixed to the polymer chain by the deposition of the polar solvent. In other words, the term "bonding" does not mean to be limited to a specific type of physical bond, chemical bond, etc., but rather includes a state in which the polar compound is fixed by various bonds including these physical bonds, chemical bonds, etc., a state in which the polar compound is fixed by simple adhesion such as adsorption, or a state in which the polar compound is included in a three-dimensional network structure formed by cross-linking of the polymer and is fixed adjacent to the polymer chain or cross-linked structure.

[0030] The term "three-dimensional network structure" as used herein refers to a structure including a three-dimensional frame and an internal space formed by the frame, and the frame may include polymer chains including crosslinks formed by the crosslinking functional groups, for example, crosslinks between crosslinking functional groups and / or crosslinks between the crosslinking functional groups and a crosslinking agent. The three-dimensional network structure may also be referred to as a crosslinked structure.

[0031] As used herein, the expression "a polar compound (polar solvent) in a composite solid electrolyte exists or is contained in a "gaseous state"" refers to the polar compound being deposited in a vapor state, as opposed to the polar solvent or an electrolyte containing the polar compound being injected in a liquid state. This means that the polar compound exists in a state distinct from the liquid-injected electrolyte immediately after the composite solid electrolyte is manufactured or during the charge / discharge process of an all-solid-state secondary battery containing the composite solid electrolyte. However, depending on the storage or operating conditions of the composite solid electrolyte and / or secondary battery, the deposited polar compound may be locally or temporarily liquefied. Even in this case, the deposited polar compound exhibits higher mobility than the polar solvent injected in a liquid state and thus exhibits a state distinct from the liquid polar solvent, and is therefore also considered to exist or be contained in the "gaseous state."

[0032] Meanwhile, in the past, in order to improve the ionic conductivity of solid electrolytes, composite solid electrolytes have been prepared by dispersing ceramic compounds such as oxides in a polymer matrix. However, such composite solid electrolytes have problems such as reduced ionic conductivity when the oxide-based ceramic particles in the polymer matrix are unevenly distributed or when a highly crystalline polymer such as polyethylene oxide is used as the polymer.

[0033] In addition, conventional methods for improving the ionic conductivity of solid electrolytes have involved immersing or supporting the solid electrolyte in a liquid electrolyte or solvent, or directly injecting the liquid electrolyte or solvent into the solid electrolyte in a liquid state. While adding a liquid electrolyte or solvent directly to a solid electrolyte does improve the ionic conductivity of the solid electrolyte, this improvement is limited to the high ionic conductivity of the liquid itself, and requires the injection of a significant amount of liquid electrolyte. In other words, lithium ion conduction is driven by the liquid electrolyte added to the solid electrolyte rather than the inherent physical properties of the solid electrolyte, and this approach does not improve the physical properties of the solid electrolyte itself. Furthermore, adding a liquid electrolyte or solvent directly to a solid electrolyte in a liquid state can lead to undesired side reactions between the polymer and the liquid phase, damaging the polymer chains or breaking the bonds within the polymer, thereby disrupting the structure of the solid electrolyte and resulting in reduced ionic conductivity.

[0034] In addition, when a solvent or liquid electrolyte is directly injected into a solid electrolyte, the liquid phase molecules rapidly diffuse into the solid electrolyte, causing rapid relaxation of polymer chains and promoting gelation on the surface, which may result in a decrease in mechanical properties and may not completely resolve issues such as leakage of the liquid electrolyte.

[0035] Furthermore, in the case of the prior art disclosed in JP 1994-124713 A, a technique was used in which a solvent was evaporated onto a general PEO (polyethylene oxide) polymer, but in this case, there was a problem that the internal structure of the polymer collapsed and ionic conductivity could not be ensured.

[0036] Therefore, the inventors crosslinked a PEO (polyethylene oxide) copolymer modified with crosslinkable functional groups and mixed a ceramic compound during the crosslinking process to produce a polymer film in which the ceramic compound was uniformly dispersed in the internal space of the polymer chains. Furthermore, the polymer film was exposed to polar solvent vapor, allowing trace amounts of polar solvent gas molecules to bind to or be incorporated into the internal space of the polymer chains.

[0037] The composite solid electrolyte thus prepared includes a polymer including a PEO-based copolymer having cross-linkable functional groups; a ceramic compound; and a polar compound, wherein at least a portion of the cross-linkable functional groups form cross-links with each other to form a three-dimensional network structure of the polymer, and the polar compound may be contained in the three-dimensional network structure in a gaseous state or may exhibit a structure bonded to the polymer chain.

[0038] It was confirmed that this composite solid electrolyte exhibits improved ionic conductivity even though it contains a small amount of polar compounds derived from a polar solvent in a gaseous state. This is believed to be because the polar compounds in the gaseous state affect the physical properties of the PEO-based copolymer, such as its crystallinity, increasing the chain mobility of the polymer, thereby improving the conductivity of the lithium ions contained in the polymer solid electrolyte. Furthermore, this ionic conductivity can be further improved by the uniform dispersion of the ceramic compound.

[0039] Furthermore, the present inventors have developed a method for producing a composite solid electrolyte that exhibits improved ionic conductivity based on the above-mentioned principle, in a continuous process, enabling mass production.

[0040] A method for producing such a composite solid electrolyte will be specifically described below.

[0041] Method for manufacturing composite solid electrolyte One embodiment of the invention provides a method for producing a composite solid electrolyte, an example of which is shown in a flow chart in FIG.

[0042] 1 , the method for manufacturing a composite solid electrolyte according to one embodiment includes: (S1) preparing a mixed solution containing a PEO (polyethylene oxide)-based copolymer having a cross-linkable functional group and a ceramic compound; (S2) unwinding a substrate using an unwinder and feeding the substrate to a transport path; (S3) coating the mixed solution on the substrate to form a coating film; (S4) transporting the substrate with the coated film to a drying section and drying it to form a polymer film; (S5) transporting the polymer film to a deposition section and depositing a polar solvent thereon to form a composite solid electrolyte layer; and (S6) winding and recovering the substrate with the composite solid electrolyte layer using a rewinder. Steps (S1) to (S6) may be performed continuously.

[0043] Hereinafter, each step of the manufacturing method according to one embodiment will be described in more detail.

[0044] In the step (S1), a mixed solution containing a PEO (polyethylene oxide) copolymer having a cross-linkable functional group and a ceramic compound can be prepared.

[0045] The mixed solution can be prepared by mixing the PEO-based copolymer and the ceramic compound in a solvent, and additionally mixing at least one of a lithium salt, a crosslinker, and an initiator. The lithium salt can be mixed to form an electrolyte, and the crosslinker and / or initiator can be mixed to form crosslinks in the PEO-based copolymer.

[0046] The solvent is not particularly limited as long as it can dissolve the PEO copolymer and one or more of the lithium salt, crosslinker, and initiator and can be easily removed by a drying process. For example, the solvent may be acetonitrile, methanol, ethanol, tetrahydrofuran, water, isopropyl alcohol, dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), or N,N-dimethyl formamide (DMF). These solvents are reaction media for crosslinking and are distinct from polar solvents contained in liquid electrolytes, and are completely removed by drying after crosslinking.

[0047] The concentration of the mixed solution can be appropriately adjusted taking into consideration the smooth progress of the molding process for preparing the composite solid electrolyte. Specifically, the concentration of the mixed solution may refer to the concentration (w / w%) of the polymer in the mixed solution. In this case, the concentration of the polymer may be the concentration of the PEO-based copolymer. For example, the concentration of the mixed solution may be 5 wt% to 20 wt%, specifically, 5 wt% or more, 7 wt% or more, or 9 wt% or more, or 13 wt% or less, 17 wt% or less, or 20 wt% or less. If the concentration of the mixed solution is less than 5 wt%, the concentration may be excessively diluted, resulting in a decrease in the mechanical strength of the composite solid electrolyte or in the possibility of it running off when applied to a substrate. If the concentration is more than 20 wt%, it may be difficult to dissolve the lithium salt in the mixed solution to the desired concentration, or the viscosity may be high, reducing solubility and making it difficult to apply the solution in the form of a uniform thin film.

[0048] The cross-linking functional groups may be of two or more types. The cross-linking functional groups may be the same or different, and preferably different. When the cross-linking functional groups are different, the PEO copolymer may contain multiple types of repeating units each containing these functional groups. Furthermore, when multiple types of cross-linking functional groups are contained, it may be easier to control the mobility and ionic conductivity of the polymer chain.

[0049] The cross-linkable functional group means a functional group that can form a cross-link between itself and / or with itself via a cross-linking agent, and can be attached to the main chain of a polymer chain in the form of a side chain.

[0050] Specifically, the cross-linkable functional group may be directly bonded to the main chain of the PEO copolymer or may be bonded via an alkylene or alkylene oxide linker. Therefore, the cross-linkable functional group can be bonded via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (however, an alkylene linker having 0 carbon atoms represents a single bond), and may be one or more groups selected from the group consisting of a hydroxyl group, a carboxyl group, an isocyanate group, a nitro group, a cyano group, an amine group, an amide group, an epoxy group, and an allyl group.

[0051] In a more specific embodiment, the PEO-based copolymer containing cross-linkable functional groups may be a copolymer containing repeating units of the following chemical formulas 1 to 3: [Chemical formula 1] [ka] [Chemical formula 2] [ka] [Chemical formula 3] [ka] In the above chemical formulas 1 to 3, R1 is -CH2-O-(CH2-CH2-O) k -R3, k is 0 to 20, and R3 represents an alkyl group having 1 to 5 carbon atoms; R2 represents a substituent in which one or more crosslinkable functional groups selected from the group consisting of a hydroxyl group, a carboxyl group, an isocyanate group, a nitro group, a cyano group, an amine group, an amide group, an epoxy group, and an allyl group are bonded to a polymer chain via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (however, an alkylene linker having 0 carbon atoms represents a single bond); l, m, and n are the repeating numbers of the repeating unit, l and n are each independently an integer of 1 to 1,000, and m is an integer of 0 to 1,000.

[0052] For example, the cross-linkable functional group of R2 may form a polymer having a matrix form of a three-dimensional network structure formed by the cross-linking. The formation of the three-dimensional network structure by the cross-linking may improve the mechanical properties of the composite solid electrolyte, and the gaseous polar compound may be contained or bonded within the three-dimensional network structure, thereby providing a composite solid electrolyte with improved ionic conductivity.

[0053] It is also clear that the PEO copolymer may contain two or more repeating units of Formula 3, in which R2 is a different cross-linking functional group, and may also contain one or more repeating units of Formula 2.

[0054] If l, m, and n are each less than 1, the molecular weight is small, making it difficult to form a polymer, and if l, m, and n are each more than 1000, the viscosity increases, reducing solubility during preparation of the polymer solution, making film formation for producing a solid electrolyte difficult. In particular, if the number of repeating units of Formula 3 containing a cross-linking functional group among l, m, and n exceeds 1000, the degree of cross-linking increases excessively, reducing the mobility of the polymer chain and potentially reducing the ionic conductivity of the composite solid electrolyte.

[0055] As used herein, a "hydroxy group" refers to an --OH group.

[0056] As used herein, a "carboxyl group" refers to a -COOH group.

[0057] As used herein, an "isocyanate group" refers to a -N=C=O group.

[0058] As used herein, a "nitro group" refers to the -NO2 group.

[0059] As used herein, a "cyano group" refers to a -CN group.

[0060] As used herein, an "amide group" refers to -C(=O)NR'R", where R' and R" are each independently hydrogen or a C1-C5 alkyl group, or R' and R" together with the N atom to which they are attached can form a heterocycle having C4-C8 atoms in the ring structure.

[0061] In this specification, the "amine group" may be selected from the group consisting of monoalkylamine groups, monoarylamine groups, monoheteroarylamine groups, dialkylamine groups, diarylamine groups, diheteroarylamine groups, alkylarylamine groups, alkylheteroarylamine groups, and arylheteroarylamine groups. The number of carbon atoms is not particularly limited, but preferably 1 to 30. Specific examples of the amine group include, but are not limited to, methylamine groups, dimethylamine groups, ethylamine groups, diethylamine groups, phenylamine groups, naphthylamine groups, biphenylamine groups, dibiphenylamine groups, anthracenylamine groups, 9-methylanthracenylamine groups, diphenylamine groups, phenylnaphthylamine groups, ditolylamine groups, phenyltolylamine groups, triphenylamine groups, biphenylnaphthylamine groups, phenylbiphenylamine groups, biphenylfluorenylamine groups, phenyltriphenylenylamine groups, and biphenyltriphenylenylamine groups. Furthermore, the term "amino group" refers to -NH.

[0062] As used herein, an "allyl group" refers to the group -CH2-CH=CH2.

[0063] The weight-average molecular weight (Mw) of the copolymers including Formulas 1-3 may be 100,000 g / mol to 2,000,000 g / mol, specifically, 100,000 g / mol or more, 200,000 g / mol or more, or 300,000 g / mol or more, or 1,600,000 g / mol or less, 1,800,000 g / mol or less, or 2,000,000 g / mol or less. If the weight-average molecular weight (Mw) of the copolymer is less than 100,000 g / mol, the mechanical properties of the film required to form the composite solid electrolyte may not be sufficient. If the weight-average molecular weight (Mw) of the copolymer is more than 2,000,000 g / mol, the viscosity increases, reducing solubility during the preparation of the polymer solution, making it difficult to form the polymer film required to produce the composite solid electrolyte. In addition, during the preparation of the polymer film, the ionic conductivity of the composite solid electrolyte may decrease due to a decrease in chain mobility caused by an increase in crystallinity within the film. In particular, when the repeating number of repeating units containing cross-linking functional groups among l, m, and n exceeds 1,000, the degree of cross-linking increases excessively, reducing polymer chain mobility and decreasing the ionic conductivity of the composite solid electrolyte.

[0064] The copolymer may also be a random copolymer or a block copolymer.

[0065] Meanwhile, the composite solid electrolyte may include a ceramic compound having lithium ion transport ability for improving the conductivity of lithium ions, preferably containing lithium atoms and capable of transporting lithium ions without storing lithium, thereby improving the ionic conductivity of the composite solid electrolyte.

[0066] In addition, the ceramic compound may be included in the polymer film formed by cross-linking induced during drying in step (S4) in a state of being uniformly dispersed in the internal spaces of the cross-linked polymer chains. The ceramic compound is mixed together during the formation of the mixed solution, and can be uniformly dispersed without agglomeration in the internal spaces between the cross-linked polymer chains. Such a uniformly dispersed ceramic compound may be advantageous for improving the mechanical strength and ionic conductivity of the composite solid electrolyte.

[0067] The ceramic compound may also be in the form of particles. Due to its morphological characteristics, the ceramic compound may be contained in a more uniformly dispersed state within the composite polymer solid electrolyte. The ceramic compound particles may be spherical, and their diameter may be 100 nm to 1000 nm. If the diameter is less than 100 nm, the amorphization effect due to reduced crystallinity of the polymer is minimal. If the diameter is more than 1000 nm, aggregation between particles may increase, reducing dispersibility and making uniform dispersion difficult.

[0068] The ceramic compound may be an oxide-based or phosphate-based compound, and may be an oxide-based solid electrolyte in the form of, for example, lithium metal oxide or lithium metal phosphate. More specifically, the ceramic compound may be a garnet-type lithium-lanthanum-zirconium oxide (LLZO, Li7La3Zr2O 12 ) compounds, perovskite-type lithium-lanthanum-titanium oxides (LLTO, Li3xLa 2 / 3-x TiO3) compounds, phosphate-based NASICON-type lithium-aluminum-titanium phosphate (LATP, Li 1+x Al x Ti 2-x (PO4)3) compounds, lithium-aluminum-germanium phosphate system (LAGP, Li 1.5 Al 0.5 Ge 1.5The solid electrolyte may be one or more selected from the group consisting of lithium-lanthanum-zirconium-titanium oxide (LLZTO) compounds, lithium-silicon-titanium phosphate (LSTP, LiSiOTiO(PO)) compounds, and lithium-lanthanum-zirconium-titanium oxide (LLZTO) compounds. More preferably, one or more oxide-based solid electrolytes 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) can be used.

[0069] The oxide-based solid electrolyte made of the oxide-based or phosphate-based compound generally has a maximum resistance of 10 -4 ~10 -3 It has an ionic conductivity of 100 S / cm, is stable in the high voltage range, is stable in air, and has the advantages of being easy to synthesize and handle.

[0070] Therefore, when the composite solid electrolyte further contains the ceramic compound, the drawbacks of the polymer-based solid electrolyte can be overcome.

[0071] In addition, the ceramic compound has high high-temperature stability because it does not easily burn or ignite even at high temperatures of 400° C. or higher. Therefore, when the composite solid electrolyte contains the ceramic compound, it is possible to improve the mechanical strength of the composite solid electrolyte as well as its high-temperature stability and ionic conductivity.

[0072] The ceramic compound may be contained in an amount of 10 to 100 parts by weight, or 10 to 60 parts by weight, relative to 100 parts by weight of the PEO copolymer containing a cross-linkable functional group.

[0073] If the ceramic compound is contained in an excessively small amount, the polymer crystallinity and amorphous effect of the ceramic compound may be reduced, resulting in a small increase in the ionic conductivity of the composite solid electrolyte, and the mechanical properties may not reach the expected level due to the formation of a composite.

[0074] If the ceramic compound is contained in an excessively large amount, the ceramic compound may not be uniformly dispersed in the polymer, and the ceramic compound particles may aggregate and clump together, resulting in a composite solid electrolyte with reduced ionic conductivity.

[0075] In one embodiment of the present invention, the lithium salt can be used as a raw material for forming an electrolyte. The lithium salt is contained in the internal space between the polymer chains in a dissociated ionic state, thereby improving the ionic conductivity of the composite solid electrolyte. At least a portion of the cations and / or anions dissociated from the lithium salt are present in a state bound to the polymer chains, and can exhibit mobility during charge / discharge of the battery.

[0076] The lithium salts include (CF3SO2)2NLi (Lithium bis(trifluoromethanesulphonyl)imide, LiTFSI), (FSO2)2NLi (Lithium bis(fluorosulfonyl)imide, LiFSI), LiNO3, LiOH, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl 10 , LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiSCN, LiC(CF3SO2)3, lithium chloroborane, lithium lower aliphatic carboxylate, and lithium tetraphenylborate.

[0077] The lithium salt may be contained in an amount of 25 to 45 parts by weight relative to 100 parts by weight of the PEO-based copolymer having a cross-linkable functional group, specifically, 25 parts by weight or more, 30 parts by weight or more, or 35 parts by weight or more, or 40 parts by weight or less, or 45 parts by weight or less. If the content of the lithium salt is less than 25 parts by weight, the ionic conductivity of the composite solid electrolyte may decrease, and if it exceeds 45 parts by weight, the mechanical strength may decrease.

[0078] The crosslinking agent can form a crosslink with the crosslinkable functional group, and the crosslink may be a hydrogen bond, a bond due to Lewis acid-base interaction, an ionic bond, a coordinate bond, or a bond formed by radical polymerization.

[0079] The crosslinking agent is not particularly limited as long as it can form a crosslink with the crosslinkable functional group. For example, the crosslinking agent may be trimethylolpropane trimethacrylate, polyethylene glycol diacrylate (poly(ethylene glycol) diacrylate), polyethylene glycol dimethacrylate (poly(ethylene glycol) dimethacrylate), ethylene glycol dimethylacrylate (hereinafter referred to as "EGDMA"), 1,3-diisopropenylbenzene (DIP), 1,4-diacryloyl piperazine, 2-(diethylamino)ethyl methacrylate, 2,6-bisacryloylamidopyridine, 3-(acryloxy)-2-hydroxypropyl methacrylate, 3,5-bis(acrylamido)benzoic acid (3,5-bis(acrylamido)benzoic acid, 3-aminopropyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-methylacryloxypropyl trimethoxysilane, bis-(1-(tert-butylperoxy)-1-methylethyl)-benzene, dicumyl peroxide, dimethacrylate, divinylbenzene, ethylene glycol maleic rosinate acrylate, glycidilmethacrylate, hydroxyquinoline, iphenyldiethoxysilane, maleic rosin glycol acrylate, methylene bisacrylamide, N,N'-1,4-phenylenediacrylamine, N,O-bisacryloyl-phenylalaninol, N,O-bismethacryloylethanolamineThe crosslinking agent may be one or more polyfunctional crosslinking agents selected from the group consisting of 0-bismethacryloyl ethanolamine, pentaerythritol triacrylate, phenyltrimethoxysilane, tetramethoxysilane, tetramethylene, tetraethoxysilane, and triallyl isocyanurate, for example, a polyvalent compound having two or more functional groups.

[0080] The crosslinking agent may be included in an amount of 1 to 30 parts by weight based on 100 parts by weight of the PEO copolymer having a crosslinkable functional group. If the content of the crosslinking agent is less than 1 part by weight, crosslinking with the crosslinkable functional group may not be sufficient, while if the content is more than 30 parts by weight, crosslinking may be excessive, which may reduce the mobility of the polymer chain and thereby reduce ion conductivity.

[0081] In one embodiment of the present invention, the initiator induces a radical polymerization reaction between the cross-linkable functional groups to form cross-links between the cross-linkable functional groups. The functional group that enables the radical polymerization reaction may be a functional group containing vinyl at its terminal, or may be, for example, an allyl group.

[0082] The initiator is not particularly limited as long as it is an initiator that can induce a radical polymerization reaction between the cross-linking functional groups. For example, the initiator may include one or more selected from the group consisting of benzoyl peroxide, azobisisobutyronitrile, lauroyl peroxide, cumene hydroperoxide, diisopropylphenyl hydroperoxide, tert-butyl hydroperoxide, p-menthane hydroperoxide, and 2,2'-azobis(2-methylpropionitrile).

[0083] The initiator can be used in an amount of 0.5 to 2 parts by weight per 100 parts by weight of the PEO copolymer containing cross-linking functional groups, and when used in this range, it can induce a radical polymerization reaction between the cross-linking functional groups to efficiently form cross-links.

[0084] Meanwhile, in the step (S2), the substrate can be unwound using the unwinder and supplied to the transport path.

[0085] The rewinder rewinds and supplies the substrate wound in a roll shape to a predetermined transport path, and may rewind and supply the substrate by its own drive. In addition, in step (S6), the substrate may be rewinded and supplied by the drive force of a rewinder that winds the substrate on which the composite solid electrolyte layer is formed.

[0086] Thus, the fabrication of the composite solid electrolyte according to one embodiment may be a roll-to-roll process.

[0087] The substrate is not particularly limited as long as it serves as a support for the coating film, and may be in the form of a film. For example, the substrate may be SUS (stainless use steel), polyethylene terephthalate film, polytetrafluoroethylene film, polyethylene film, polypropylene film, polybutene film, polybutadiene film, vinyl chloride copolymer film, polyurethane film, ethylene-vinyl acetate film, ethylene-propylene copolymer film, ethylene-ethyl acrylate copolymer film, ethylene-methyl acrylate copolymer film, or polyimide film.

[0088] Meanwhile, in the step (S3), the mixed solution may be continuously coated on the substrate to form a coating film.

[0089] The coating method is not particularly limited as long as it can form a coating film from the mixed solution on the substrate, and may be, for example, bar coating, roll coating, spin coating, slit coating, die coating, blade coating, comma coating, slot die coating, lip coating, spray coating, or solution casting.

[0090] As a specific example of the coating method, a solution casting method can be used. More specifically, the mixed solution prepared in step (S1) is placed in a mixer, and the mixer is then positioned above a substrate, and the mixed solution is continuously cast onto the substrate supplied in a unidirectional transport path to form a coating film.

[0091] In step (S4), the coating film formed on the substrate may be transferred to a drying section and dried to form a polymer film.

[0092] The drying method can be a hot air drying method in which hot air is used to dry the coated film at a certain temperature range, but is not limited to these examples and any method can be used as long as it can dry the coated film on the substrate film on which the coated film has been formed.

[0093] Specifically, the drying may be performed at 50° C. to 250° C. Specifically, the drying temperature may be 50° C. or higher, 70° C. or higher, or 90° C. or higher, or 120° C. or lower, 150° C. or lower, 200° C. or lower, or 250° C. or lower. If the drying temperature is lower than 50° C., the coating film formed by applying the mixed solution to the substrate may not dry sufficiently and may flow off as a liquid phase. If the drying temperature exceeds 250° C., the coating film applied to the substrate may be damaged or foamed, preventing the formation of a smooth coating film.

[0094] Alternatively, the drying may include primary drying and secondary drying, in which the primary drying removes a portion of the solvent contained in the coating film to form a film, and the secondary drying forms crosslinks between the crosslinkable functional groups induced by the initiator and / or between the crosslinkable functional groups and the crosslinking agent.

[0095] The primary drying can be carried out at room temperature for 5 to 20 hours, and the secondary drying can be carried out at 50 to 250° C. When the drying process is carried out through the primary and secondary drying steps, a uniform film can be formed and internal cross-linking can be more effectively formed.

[0096] In addition, the drying section is not limited to one stage, and if the drying path is long, the drying section may be formed in multiple stages to improve drying efficiency, for example, three or more stages of drying section may be formed.

[0097] As a result of the drying process, a cross-linking reaction occurs in the polymer film, resulting in polymer chains containing cross-links. The cross-links may include cross-links between cross-linkable functional groups and / or cross-links between the cross-linkable functional groups and a cross-linking agent. For example, at least some of the cross-linkable functional groups may form cross-links with each other via the cross-linking agent to form the three-dimensional network structure described above.

[0098] The cross-linking bond between the cross-linkable functional groups may be a urethane cross-linking bond, an ester cross-linking bond, a hydrogen bond, a bond formed by a radical polymerization reaction of a vinyl group at the end of an allyl group (-CH-CH=CH), or the like, but is not limited to these examples.

[0099] The crosslinking bond between the crosslinkable functional group and the crosslinking agent may be a hydrogen bond, a bond due to Lewis acid-base interaction, an ionic bond, a coordinate bond, or a bond formed by radical polymerization.

[0100] In the internal space of the polymer chains where cross-linking is formed, for example, in a three-dimensional network structure, the ceramic compound may be uniformly dispersed, or the lithium salt may be dissociated and contained in an ionic state.

[0101] Meanwhile, in step (S5), the polymer film is transferred to a deposition section and a polar solvent is deposited thereon to prepare a composite solid electrolyte.

[0102] The vapor deposition may be performed by naturally evaporating the polar solvent at room temperature or by evaporating the polar solvent by heating, and bonding the gas molecules of the polar solvent to the polymer chains inside the polymer film or by incorporating the gas molecules of the polar solvent into the internal space of the polymer chains.

[0103] In this way, the polar solvent may be placed at room temperature or evaporated by heating, so that the polar solvent is uniformly dispersed on the surface and / or inside of the polymer, and gas molecules of the polar solvent may be bound to the polymer chains or may be uniformly dispersed in the internal space of the polymer chains.

[0104] When the polar solvent is placed at room temperature during the deposition, a small amount of polar solvent with a low boiling point can be gradually infiltrated into the solid electrolyte at room temperature, effectively inducing a conformational change in the cross-linked polymer chains in the solid film.

[0105] Furthermore, the deposition rate can be increased by heating the polar solvent during the deposition. The heating temperature is not particularly limited as long as it is a temperature at which the polar solvent can undergo a phase change to vapor, and may be, for example, 30°C to 80°C. While typical PEO copolymers melt at 60°C, the PEO copolymers modified with cross-linking functional groups exhibit improved heat resistance and can withstand temperatures up to 80°C when a cross-linked structure is formed, further increasing the deposition rate. Furthermore, the heating method is not limited as long as it can supply energy sufficient to generate vapor. Examples of suitable heating methods include, but are not limited to, direct heating using a burner or fan, and indirect heating using a heater or steam tube.

[0106] If the heating temperature is too high, the temperature may exceed the boiling point of the polar solvent or cause deformation of the polymer, and it may be difficult to control the evaporation rate of the polar solvent during deposition. Therefore, in order to deposit a small amount of polar solvent, it is preferable to perform deposition at a heating temperature within the appropriate range as defined above.

[0107] As described above, composite solid electrolytes can be prepared that contain polar compounds, such as gas molecules of polar solvents, bonded to cross-linked polymer chains or contained within the interior spaces of the polymer chains by vapor deposition.

[0108] The polar compound may be gas molecules of a polar solvent used in the deposition process, and may be adsorbed onto the polymer during deposition and then diffused into the polymer chains, thereby being contained on the surface or inside of the polymer chains. Specifically, the polar compound may be bound to the polymer chains or dispersed in the internal space between the polymer chains.

[0109] The polar compound may be bonded to the polymer chain or dispersed in the internal space between the polymer chains, thereby improving the ionic conductivity of the final composite solid electrolyte.

[0110] Such a composite solid electrolyte is substantially free of a liquid solvent or electrolyte solution, but contains a trace amount of a polar compound contained or bonded in a gaseous state by the deposition. Such a composite solid electrolyte can be identified, for example, by the absence of a liquid component on the surface of the electrolyte layer when an electrolyte layer containing the composite solid electrolyte is separated from an all-solid-state battery or the like and observed with the naked eye or an electron microscope. In contrast, when a liquid polar solvent or electrolyte solution is injected into the composite solid electrolyte, a liquid component or a component exhibiting wettability can be observed on the surface of the electrolyte layer. Furthermore, a composite solid electrolyte containing the polar compound in a gaseous state by vapor deposition exhibits significantly higher ionic conductivity than a composite solid electrolyte containing the polar compound in a gaseous state by vapor deposition. A comparison of ionic conductivities also confirms the existence of a composite solid electrolyte containing the polar compound in a gaseous state by vapor deposition.

[0111] Specifically, the polar compounds bound to the polymer chains or contained in the internal spaces between the polymer chains act as plasticizers within the polymer, plasticizing the polymer. The plasticized polymer increases the amorphous region within the polymer, improving the mobility of the polymer chains. The improved mobility of the polymer chains increases the ion hopping effect within the polymer, improving the ionic conductivity of the composite solid electrolyte.

[0112] In addition, the polar compound can act as an intermediate for smooth ion transport through ion hopping. Because the affinity between lithium ions and polar compounds is stronger than the affinity between lithium ions and the ether oxygen of the PEO-based copolymer, lithium ions can be transported more quickly and easily within the polymer with the polar compound adsorbed. In other words, the inflow of polar compounds, which are polar solvent molecules, into the polymer increases the cation solvation effect of lithium ions, improving ion mobility and, therefore, the ionic conductivity of the composite solid electrolyte.

[0113] The polar solvent or the corresponding polar compound may include one or more compounds selected from the group consisting of carbonate compounds and sulfonyl compounds.

[0114] Specifically, the polar compound may include one or more compounds selected from the group consisting of ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), and sulfolane, or a combination thereof.

[0115] The content of the polar compound may be 0.1 wt % or more and less than 10 wt % based on the total weight of the composite solid electrolyte. For example, the content of the polar compound may be 0.1 wt % or more, 1 wt % or more, or 8 wt % or less, 9 wt % or less, or less than 10 wt %. If the content of the polar compound is less than 0.1 wt %, it is difficult to induce a change in chain conformation within the polymer, and the ionic conductivity of the composite solid electrolyte is not improved. If the content of the polar compound is 10 wt % or more, the solid electrolyte contains too much liquid, exhibiting the properties of a semi-solid battery. In addition, gelation of the polymer may reduce the mechanical strength of the composite solid electrolyte.

[0116] Additionally, in the step (S6), the substrate including the composite solid electrolyte layer may be wound and recovered using a rewinder.

[0117] The rewinder can wind the substrate including the composite solid electrolyte layer into a roll shape and recover it, and can wind the substrate including the composite solid electrolyte layer by driving itself.

[0118] The recovered substrate containing the composite solid electrolyte layer can be used as it is, or the composite solid electrolyte can be used in the form of a free-standing film by additionally performing a step of separating the composite solid electrolyte layer from the substrate.

[0119] The freestanding film refers to a film that can maintain its film form by itself at room temperature and pressure without a separate support, i.e., without a substrate.

[0120] In the manufacturing method according to the embodiment described above, the steps (S1) to (S6) may be performed continuously, so that the composite solid electrolyte can be manufactured in a continuous process.

[0121] Composite solid electrolyte The composite solid electrolyte manufactured according to the above-described embodiment includes a polymer including a polyethylene oxide (PEO)-based copolymer having cross-linkable functional groups; a ceramic compound; and a polar compound, wherein at least a portion of the cross-linkable functional groups form cross-links with each other, so that the polymer forms a three-dimensional network structure, and the polar compound may be contained in the three-dimensional network structure in a gaseous state or may have a structure bonded to the polymer chain.

[0122] In the composite solid electrolyte, the three-dimensional network structure may include a three-dimensional frame and an internal space formed by an upper frame, the frame including polymer chains including cross-links formed by the cross-linking functional groups, and the internal space may include a ceramic compound or a polar compound in a gaseous state obtained by vapor deposition.

[0123] The cross-linking bonds formed by the cross-linking functional groups forming the frame may include cross-linking bonds between the cross-linking functional groups and / or cross-linking bonds between the cross-linking functional groups and a cross-linking agent.

[0124] The ceramic compound is dispersed in the internal space of the three-dimensional network structure, allowing the ceramic compound to be uniformly dispersed. The uniformly dispersed ceramic compound morphology can further improve the mechanical strength and ionic conductivity of the composite solid electrolyte.

[0125] In addition, the polymer chain may be bonded to a polar compound in a gaseous state, or the internal space of the polymer chain may contain a polar compound in a gaseous state. In this case, the manner in which the polar compound is bonded to the polymer chain is not particularly limited as long as the polar compound is fixed to the polymer chain. In other words, the bond may include both physical and chemical bonds.

[0126] The form, structure, and types and contents of the constituent components of the composite solid electrolyte are as described above.

[0127] All solid state battery An additional embodiment of the invention also relates to an all-solid-state battery including the composite solid electrolyte, the all-solid-state battery including a negative electrode, a positive electrode, and a composite solid electrolyte interposed between the negative electrode and the positive electrode, wherein the solid electrolyte is manufactured according to one of the above-described embodiments.

[0128] Specifically, the composite solid electrolyte has a three-dimensional network structure of polymer chains as described above, and the ceramic compound is uniformly contained in the internal spaces of the polymer chains. Polar compounds, which are gas molecules of a polar solvent, are bonded to the polymer chains or contained in the internal spaces of the polymer chains through a deposition process, thereby improving mechanical properties and ionic conductivity, making the composite solid electrolyte suitable for use as an electrolyte for all-solid-state batteries.

[0129] Meanwhile, the positive electrode included in the all-solid-state battery may include a positive electrode active material layer, and the positive electrode active material layer may be formed on one surface of a positive electrode current collector.

[0130] The positive electrode active material layer includes a positive electrode active material, a binder, and a conductive material.

[0131] The positive electrode active material is not particularly limited as long as it is a material that can reversibly absorb and release lithium ions, and examples thereof include lithium cobalt oxide (LiCoO), lithium nickel oxide (LiNiO), Li[Ni x Co y Mn z M v ]O2 (wherein M is any 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, and x+y+z+v=1), Li (Li a M b-a-b’ M' b’ )O 2-c A c (wherein 0≦a≦0.2, 0.6≦b≦1, 0≦b'≦0.2, 0≦c≦0.2; M 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); layered compounds and compounds substituted with one or more transition metals, such as those represented by the formula Li 1+y Mn 2-y Lithium manganese oxides such as LiMnO4 (where y is 0-0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, and Cu2V2O7; and the chemical formula LiNi 1-y Ni-site lithium nickel oxide represented by 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 of such compounds include, but are not limited to, lithium manganese composite oxides expressed as LiMnO2 (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; and Fe2(MoO4)3.

[0132] The positive electrode active material may be included in an amount of 40 to 80 wt % based on the total weight of the positive electrode active material layer. Specifically, the content of the positive electrode active material may be 40 wt % or more or 50 wt % or more, or 70 wt % or less or 80 wt % or less. If the content of the positive electrode active material is less than 40 wt %, the connectivity between the positive electrode active materials may be insufficient, and if it exceeds 80 wt %, the mass transfer resistance may be high.

[0133] Furthermore, the binder is a component that aids in bonding the positive electrode active material to the conductive material and the current collector, and is selected from the group consisting of styrene-butadiene rubber, acrylated 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, polyacrylonitrile, The binder may include at least one selected from the group consisting of nitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene. Preferably, the binder may include at least one selected from the group consisting of styrene-butadiene rubber, polytetrafluoroethylene, carboxymethyl cellulose, polyacrylic acid, lithium polyacrylate, and polyvinylidene fluoride.

[0134] The binder may be included in an amount of 1 wt % to 30 wt % based on the total weight of the positive electrode active material layer. Specifically, the binder content may be 1 wt % or more, or 3 wt % or more, or 15 wt % or less, or 30 wt % or less. If the binder content is less than 1 wt %, the adhesive strength between the positive electrode active material and the positive electrode current collector may be reduced. If the binder content exceeds 30 wt %, the adhesive strength is improved, but the content of the positive electrode active material may be reduced accordingly, resulting in a reduced battery capacity.

[0135] 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, has excellent electrical conductivity without inducing chemical changes in the battery, and typically includes graphite or conductive carbon. Examples of the conductive material include graphite such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, denka black, thermal black, channel black, furnace black, and lamp black; carbon-based materials having a graphene or graphite crystal structure; 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 may be used alone or in combination, but are not necessarily limited thereto.

[0136] The conductive material may typically be included in an amount of 0.5 wt % to 30 wt % based on the total weight of the positive electrode active material layer. Specifically, the content of the conductive material may be 0.5 wt % or more, or 1 wt % or more, or 20 wt % or less, or 30 wt % or less. If the content of the conductive material is too low, such as less than 0.5 wt %, it may be difficult to expect an improvement in electrical conductivity or the electrochemical characteristics of the battery may be deteriorated. If the content of the conductive material is too high, such as more than 30 wt %, the amount of positive electrode active material may be relatively reduced, resulting in reduced capacity and energy density. The method for incorporating the conductive material into the positive electrode is not particularly limited, and conventional methods known in the art, such as coating the positive electrode active material, may be used.

[0137] The positive electrode current collector supports the positive electrode active material layer and plays a role in transferring electrons between an external conductor and the positive electrode active material layer.

[0138] The positive electrode current collector is not particularly limited as long as it has high electronic conductivity without inducing chemical changes in the all-solid-state battery, and examples of the positive electrode current collector include copper, stainless steel, aluminum, nickel, titanium, palladium, baked carbon, copper or stainless steel surface-treated with carbon, nickel, silver, or the like, and aluminum-cadmium alloys.

[0139] The positive electrode current collector may have a micro-irregular structure or a three-dimensional porous structure on its surface to strengthen the bonding strength with the positive electrode active material layer, and may include various forms such as a film, sheet, foil, mesh, net, porous body, foam, or nonwoven fabric.

[0140] Such a positive electrode can be manufactured by a conventional method. Specifically, the positive electrode active material layer-forming composition is prepared by mixing a positive electrode active material, a conductive material, and a binder in an organic solvent, and then coated and dried on a positive electrode current collector. Optionally, the composition can be compression-molded onto the current collector to improve electrode density. In this case, it is preferable to use an organic solvent that can uniformly disperse the positive electrode active material, binder, and conductive material and that is easily evaporated. Specific examples include acetonitrile, methanol, ethanol, tetrahydrofuran, water, and isopropyl alcohol.

[0141] Meanwhile, the negative electrode included in the all-solid-state battery may include a negative electrode active material layer, and the negative electrode active material layer may be formed on one surface of a negative electrode current collector.

[0142] The negative electrode active material is lithium (Li +The lithium ion-containing compound may include a material capable of reversibly intercalating or deintercalating lithium ions, a material capable of reacting with lithium ions to reversibly form a lithium-containing compound, lithium metal, or a lithium alloy.

[0143] The lithium ion (Li + The material capable of reversibly inserting or de-inserting lithium ions (Li) may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. + The material capable of reacting with lithium (Li) to reversibly form a lithium-containing compound 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).

[0144] Preferably, the negative electrode active material may be lithium metal, specifically in the form of a lithium metal thin film or lithium metal powder.

[0145] The negative electrode active material may be included in an amount of 40 to 80 wt % based on the total weight of the negative electrode active material layer. Specifically, the content of the negative electrode active material may be 40 wt % or more, or 50 wt % or more, or 70 wt % or less, or 80 wt % or less. If the content of the negative electrode active material is less than 40 wt %, 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 wt %, the mass transfer resistance may be high.

[0146] The binder is the same as that described above in the positive electrode active material layer.

[0147] Furthermore, the conductive material is as described above in the positive electrode active material layer.

[0148] The negative electrode current collector is not particularly limited as long as it is conductive and does not induce chemical changes in the battery, and examples of the negative electrode current collector that can be used include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. Furthermore, similar to the positive electrode current collector, the negative electrode current collector can be in various forms such as a film, sheet, foil, net, porous material, foam, nonwoven fabric, etc., with fine irregularities formed on the surface.

[0149] The method for manufacturing the negative electrode is not particularly limited, and the negative electrode may 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 art, such as compression bonding, coating, deposition, etc. Furthermore, the negative electrode of the present invention also includes a battery in which a thin lithium film is formed on the metal plate by initial charging after assembling the battery without a thin lithium film on the negative electrode current collector.

[0150] According to additional embodiments of the present invention, there are provided a battery module including the all-solid-state battery as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source.

[0151] Specific examples of the device include, but are not limited to, power tools powered by a battery-powered motor; 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.

[0152] Preferred examples will be presented below to aid in understanding the invention. However, the following examples are provided merely to facilitate understanding of the invention, and the invention is not limited thereto.

[0153] In the following examples and comparative examples, a polymer solid electrolyte containing a polymer including a copolymer and an organic solvent was produced as shown in Table 1 below.

[0154] Example Example 1: Preparation of composite solid electrolyte Step 1) Preparation of mixed solution A polyethylene oxide (PEO)-based copolymer of the following formula 1a was prepared: [Chemical formula 1a] [ka] In the above chemical formula 1a, R1 is -CH2-O-(CH2-CH2-O) k R2 is -CH2-O-CH2-CH=CH2, k is 2, the ratio of l:m:n is 85:13:2, and the weight average molecular weight (Mw) of the copolymer is about 2,000,000 g / mol.

[0155] The copolymer of formula 1a has an allyl group as a cross-linking functional group linked via a methylene oxide linker.

[0156] The polyethylene oxide copolymer was mixed with trimethylolpropane trimethacrylate as a crosslinker, benzoyl peroxide as an initiator, LiTFSI as a lithium salt, and LSTP as a ceramic compound in acetonitrile as a solvent to prepare a mixed solution of the polymer and the ceramic compound, which was then stirred for 24 hours using a magnetic bar. The mixed solution of the polyethylene oxide copolymer and the ceramic compound was prepared by mixing 100 parts by weight of the polyethylene oxide copolymer with 20 parts by weight of trimethylolpropane trimethacrylate as a crosslinker, 1 part by weight of benzoyl peroxide as an initiator, 36 parts by weight of LiTFSI as a lithium salt, and 40 parts by weight of LSTP as a ceramic compound. The acetonitrile solvent was used to prepare a mixed solution with 11.1 wt% polyethylene oxide copolymer as a polymer and 14.9 wt% polyethylene oxide copolymer as a polymer and 14.9 wt% ceramic compound.

[0157] Step 2) Supply of substrate The SUS foil of the base film was fed to a unidirectional transport path by a rewinding machine.

[0158] Step 3) Formation of coating film The mixed solution was placed in a mixer and then coated onto a SUS foil, which was a base film fed in a unidirectional transport path by a rewinder, by a solution casting method to form a coating film.

[0159] Step 4) Polymer film manufacturing The coating film formed on the substrate film fed in a unidirectional transport path by the rewinder was transported to a drying section and subjected to primary drying at room temperature for 12 hours and secondary drying at 100°C for 3 hours to prepare a polymer film with a thickness of 200 μm.

[0160] 5) Preparation of composite solid electrolyte after deposition The polymer film was transferred to a deposition zone and deposition was carried out.

[0161] The deposition was carried out by filling the bottom of the chamber in the deposition section with EMC (ethyl methyl carbonate) solvent and naturally evaporating it at room temperature for 72 hours. The EMC vapor was then introduced into the interior of a polymer film that was transferred to the top of the chamber, and the EMC molecules were deposited so that they bound to the polymer chains inside the polymer film or were located in the internal spaces of the polymer chains, thereby producing a composite solid electrolyte layer.

[0162] Step 6) Freestanding film-type composite solid electrolyte fabrication The substrate film including the prepared composite solid electrolyte layer was wound up using a rewinder and then recovered, and the substrate film was peeled off to prepare a composite solid electrolyte in the form of a free-standing film.

[0163] Comparative Example: Comparative Example 1: Composite solid electrolyte containing only modified PEO (no liquid) A composite solid electrolyte was prepared in the same manner as in Example 1, except that step 5) of Example 1, in which the EMC solvent was deposited, was not performed.

[0164] Comparative Example 2: Modified PEO + Liquid-Rich Composite Solid Electrolyte A composite solid electrolyte was prepared in the same manner as in Example 1, except that the EMC solvent was directly injected into the composite solid electrolyte prepared in step 1) of Example 1.

[0165] Comparative Example 3: Composite solid electrolyte deposited with unmodified PEO + ceramic compound + organic solvent A composite solid electrolyte was prepared in the same manner as in Example 1, except that a polyethylene oxide (PEO) homopolymer (weight average molecular weight: approximately 4,000,000 g / mol) without a substituted crosslinkable functional group was used, and a crosslinking agent and an initiator were not added.

[0166] Comparative Example 4: Modified PEO + organic solvent deposited polymer solid electrolyte A solid electrolyte was prepared in the same manner as in Example 1, except that no ceramic compound was added.

[0167] Experimental Example Experimental Example 1: Measurement of polar compound content The polar compound content can be measured by monitoring the weight of the liquid phase evaporating over time while heating the solid electrolyte test piece using a balance. For example, a heated electronic balance (AND Corp. MS-70) can be used to monitor the weight of the liquid phase evaporating over time while heating the test piece at a temperature of 55 to 70°C or at 60°C. When the amount of polar compound evaporating over time reaches saturation, the saturation amount is considered to be the total amount of polar compound contained within the solid electrolyte. In the examples and comparative examples, the polar compound may be ethyl methyl carbonate (EMC).

[0168] Experimental Example 2: Measurement of ionic conductivity of composite (or polymer) solid electrolytes To measure the ionic conductivity of the film-type solid electrolytes prepared in the Examples and Comparative Examples, a test was conducted using a test piece of 1.7671 cm 2 The solid electrolyte was formed on the lower substrate of a coin cell of the same size, and then SUS was used as a blocking electrode to prepare a coin cell for measuring ionic conductivity.

[0169] Resistance was measured using an electrochemical impedance spectrometer (EIS, VM3, Bio Logic Science Instrument) at 25°C with an amplitude of 10 mV and a scan range of 1 Hz to 0.1 MHz, and the ionic conductivity of the solid electrolyte was calculated using the following Equation 1:

[0170] [Formula 1]

number

[0171] Table 1 below shows the content of EMC deposited (or contained) in the composite (or polymer) solid electrolyte and the measurement results of ionic conductivity.

[0172] [Table 1]

[0173] Referring to Table 1, it was confirmed that the continuously produced composite solid electrolytes of the Examples exhibited superior ionic conductivity compared to the solid electrolytes of the Comparative Examples.

Claims

1. (S1) preparing a mixed solution containing a PEO (polyethylene oxide) copolymer containing a cross-linkable functional group and a ceramic compound; (S2) unwinding the substrate using an unwinder and supplying it to a transport path; (S3) applying the mixed solution onto the substrate to form a coating film; (S4) transferring the substrate on which the coating film is formed to a drying section and drying the substrate to form a polymer film; (S5) transferring the polymer film to a deposition section and depositing a polar solvent therein to form a composite solid electrolyte layer; and (S6) using a rewinder to wind and recover the substrate including the composite solid electrolyte layer.

2. 2. The method of claim 1, wherein the mixed solution in step (S1) further comprises at least one selected from the group consisting of a lithium salt, a crosslinking agent, and an initiator.

3. 2. The method of claim 1, wherein the mixed solution contains 10 to 100 parts by weight of the ceramic compound with respect to 100 parts by weight of a PEO (polyethylene oxide) copolymer.

4. 2. The method of claim 1, wherein the deposition in step (S5) comprises naturally evaporating the polar solvent at room temperature or evaporating the polar solvent by heating to include gas molecules of the polar solvent on the surface or inside of the polymer chains.

5. the cross-linkable functional group is bonded to the PEO-based copolymer via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (wherein an alkylene linker having 0 carbon atoms represents a single bond); 2. The method for producing a composite solid electrolyte according to claim 1, wherein the group is selected from the group consisting of a hydroxyl group, a carboxyl group, an isocyanate group, a nitro group, a cyano group, an amine group, an amide group, an epoxy group, and an allyl group.

6. 2. The method for producing a composite solid electrolyte according to claim 1, wherein the PEO (polyethylene oxide) copolymer is a copolymer containing repeating units of the following chemical formulas 1 to 3: [Chemical formula 1] 【Chemical 1】 [Chemical formula 2] 【Chemistry 2】 [Chemical formula 3] 【Chemistry 3】 In the above chemical formulas 1 to 3, R １ is -CH ２ -O-(CH ２ -CH ２ -O) ｋ -R ３ where k is 0 to 20, and R ３ represents an alkyl group having 1 to 5 carbon atoms, R ２ represents a substituent in which one or more crosslinkable functional groups selected from the group consisting of a hydroxyl group, a carboxyl group, an isocyanate group, a nitro group, a cyano group, an amine group, an amide group, an epoxy group, and an allyl group are bonded to a polymer chain via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (however, an alkylene linker having 0 carbon atoms represents a single bond), l, m, and n are the number of repeating units, l and n are each independently an integer of 1 to 1,000, and m is an integer of 0 to 1,000.

7. the gas molecules of the polar solvent are polar compounds, 2. The method for producing a composite solid electrolyte according to claim 1, wherein the content of the polar compound is 0.1 wt % or more and less than 10 wt % based on the total weight of the composite solid electrolyte.

8. The method for producing a composite solid electrolyte according to claim 1 , wherein the polar solvent includes at least one selected from the group consisting of carbonate-based compounds and sulfonyl-based compounds.

9. 2. The method for producing a composite solid electrolyte according to claim 1, wherein the polar solvent comprises at least one selected from the group consisting of ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), and sulfolane.

10. 2. The method for producing a composite solid electrolyte according to claim 1, wherein the ceramic compound comprises at least one 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.

11. The method for preparing a composite solid electrolyte according to claim 1, wherein steps (S1) to (S6) are performed continuously.

12. A composite solid electrolyte produced by the method according to any one of claims 1 to 11.

13. polymers, including PEO-based copolymers containing cross-linkable functional groups; ceramic compounds; and polar compounds; at least a part of the cross-linking functional groups form cross-links with each other, and the polymer forms a three-dimensional network structure; The composite solid electrolyte according to claim 12 , wherein the polar compound is contained in the three-dimensional network structure in a gaseous state or is bonded to the polymer chain.

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