Method for producing polymer solid electrolyte

Abstract

The present invention relates to a method for preparing a polymer solid electrolyte, which includes the steps of (S1) preparing a polymer by crosslinking a polyethylene oxide (PEO)-based copolymer containing a crosslinkable functional group, and (S2) vapor-depositing a polar solvent onto the polymer prepared in step (S1), wherein the vapor-deposition step is carried out to satisfy a predetermined relationship, thereby controlling the content of the polar compound in the polymer solid electrolyte.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0132780, filed October 14, 2022, and Korean Patent Application No. 10-2023-0136067, 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 polymer solid electrolyte. [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, a composite electrolyte made of polyethylene oxide (PEO) and lithium salt has the advantage of being more fire-resistant than existing liquid electrolytes, but the high crystallinity of the polyethylene oxide (PEO) makes it difficult to produce a polymer solid electrolyte with improved ionic conductivity. In other words, the high crystallinity of the polymer inhibits the chain mobility of the polymer, restricting the movement of lithium ions within the polymer solid electrolyte, making it difficult to improve the ionic conductivity of the polymer solid electrolyte.

[0006] To overcome these limitations of conventional polymer solid electrolytes, technologies have been developed to improve the ionic conductivity of polymer solid electrolytes by modifying the structure of crystalline polymers or adding a plasticizer to the polymer to improve the mobility of polymer chains. However, solid polymer electrolytes manufactured using the polymer structural modification or plasticizer addition method can have difficulty improving the ionic conductivity above 0.1 mS / cm.

[0007] Attempts have been made to improve ionic conductivity by directly adding a liquid electrolyte or a solvent in a liquid state to the polymer solid electrolyte. However, this can be classified as a technology for electrolytes for semi-solid batteries in which a solid and a liquid coexist, rather than a pure solid electrolyte for all-solid-state batteries. Therefore, safety issues such as leakage of the liquid electrolyte still remain, and the improvement in ionic conductivity may not be sufficient.

[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 to develop a technology that can improve the ionic conductivity of the electrolyte 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

Problems to be Solved by the Invention

[0010] An object of the present invention is to produce a polymer solid electrolyte with improved ionic conductivity by vapor-depositing a polar solvent on a polymer, thereby containing a gaseous polar compound formed by the vapor deposition of a trace amount of the solvent, and to control the behavior of the polar solvent vapor-deposited on the polymer to maximize the degree of improvement in ionic conductivity, and to provide a method for producing a polymer solid electrolyte.

Means for Solving the Problems

[0011] One embodiment of the invention includes: (S1) producing a polymer obtained by cross-linking a PEO (polyethylene oxide)-based copolymer containing a cross-linkable functional group; and (S2) vapor-depositing a polar solvent on the polymer produced in step (S1); and providing a method for producing a polymer solid electrolyte that adjusts the content of the polar compound in the polymer solid electrolyte by proceeding for a time that satisfies the following formula 1:

[0012]

Equation

[0013] In the above formula 1, M(t) is the content of the polar compound contained in the surface or inside of the polymer chain after the polar solvent is vapor-deposited and diffused according to the vapor deposition time, t is the vapor deposition time, K is an empirical rate coefficient, which is a fitting parameter for fitting the content of the polar compound (M(t)), and 0.01 < K < 0.1, and n is a transport exponent, which is a fitting parameter for fitting the content of the polar compound (M(t)), and 0.5 ≤ n < 0.7.

[0014] In the preparation method, the step (S1) may be carried out in the presence of at least one additional agent selected from the group consisting of a crosslinking agent and an initiator, thereby carrying out the crosslinking step.

[0015] In the manufacturing method, a lithium salt may be further added during or before step (S1), and a ceramic compound may be further added during cross-linking in step (S1).

[0016] Meanwhile, in the preparation method, the crosslinkable functional group contained in the PEO-based copolymer can be bonded to the main chain of 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 may be a functional group 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.

[0017] In a specific example, the PEO (polyethylene oxide) copolymer containing the cross-linkable functional group may be a copolymer containing repeating units of the following chemical formulas 1 to 3:

[0018] [ka]

[0019] [ka]

[0020] [ka]

[0021] In the above chemical formulas 1 to 3, R1 is -CH2-O-(CH2-CH2-O) k -R3, k is 0 to 20, R3 is an alkyl group having 1 to 5 carbon atoms, R2 is 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 the 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 1000, and m is an integer of 0 to 1000.

[0022] Meanwhile, in step (S2) of the manufacturing method, vapor of the polar solvent may be deposited on the polymer so that the content of the polar solvent is 0.1 wt % or more and less than 10 wt % based on the total weight of the polymer solid electrolyte.

[0023] The polar solvent corresponds to a polar compound that is vapor-deposited and contained in the polymer solid electrolyte, and may include at least one selected from the group consisting of carbonate-based solvents and sulfonyl-based solvents. 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. [Effects of the Invention]

[0024] According to the method for manufacturing a polymer solid electrolyte according to the present invention, a polar solvent (or polar compound) in a gaseous state can be incorporated into the three-dimensional network structure of the solid electrolyte formed by cross-linking by vapor deposition, or can be bound to the cross-linked polymer.

[0025] As a result, a small amount of polar solvent is gradually injected into the solid electrolyte in a gaseous state, which prevents gelation and delays the relaxation time of the internal polymer chains, thereby improving the mobility of the polymer chains and improving ionic conductivity without deteriorating mechanical properties.

[0026] In addition, since the tendency of the ionic conductivity of the polymer solid electrolyte to increase varies depending on the manner in which the polar solvent diffuses into the polymer after being deposited on the polymer during the vapor deposition process, the improvement in ionic conductivity of the polymer solid electrolyte can be maximized by controlling the behavior of the polar solvent that is vapor-deposited and adsorbed and diffuses into the polymer based on this tendency. Specifically, the content of the gaseous polar compound can be controlled depending on the vapor deposition time to more effectively achieve the ionic conductivity of the polymer solid electrolyte within a desired range.

[0027] Furthermore, the polymer solid electrolyte maintains the inherent structural characteristics of the polymer without deformation or destruction of the material, and exhibits improved ionic conductivity due to the improved mobility of the polymer chains.

[0028] Furthermore, in the case of a composite solid electrolyte in which a ceramic compound is further added, the uniform distribution of the ceramic particles can further improve ionic conductivity. In addition, the polymer solid electrolyte can exhibit improved ionic conductivity and mechanical properties by containing a trace amount of a polar compound in a gaseous state. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a graph showing the diffusion behavior of a polar solvent in a polymer and the change in the content of deposited polar compounds as a function of vapor deposition time during the solvent vapor deposition process according to Example 1. [Figure 2] 1 is a graph showing the behavior of a polar solvent in a polymer and the change in the content of an impregnated polar compound depending on the impregnation time during the solvent impregnation step according to Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, specific embodiments will be described in more detail to facilitate understanding of the invention.

[0031] 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.

[0032] The term "bonding" used herein, in relation to the form in which a polar compound is "bonded" to a polymer chain, e.g., a PEO-based copolymer chain, broadly refers to a form in which a polar compound in a gaseous state, i.e., a polar solvent molecule, is fixed to a polymer chain by vapor deposition of a 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 located adjacent to the polymer chain or cross-linked structure.

[0033] 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.

[0034] As used herein, the term "existing or containing a polar compound (polar solvent) in a polymer solid electrolyte 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 refers to the polar compound being present in a state distinct from the liquid-injected electrolyte immediately after the preparation of the polymer solid electrolyte or during the charge / discharge process of an all-solid-state secondary battery containing the polymer solid electrolyte. However, depending on the storage or operating conditions of the polymer solid electrolyte and / or secondary battery, the vapor-deposited polar compound may be locally or temporarily liquefied. Even in this case, the vapor-deposited polar compound exhibits higher mobility than the polar solvent injected in a liquid state and thus exhibits a different state from the liquid-state polar solvent, and is therefore also considered to be present or contained in the "gaseous state."

[0035] As used herein, the term "solid polymer electrolyte" refers to a solid polymer electrolyte that includes, as essential components, (i) a polymer including a polyethylene oxide (PEO) copolymer containing a cross-linkable functional group and a polar compound; or (ii) a ceramic compound in addition to (i). The solid polymer electrolyte (ii) that further includes a ceramic compound in addition to (i) may also be referred to as a "composite solid electrolyte."

[0036] Meanwhile, 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 substantial 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 or injecting a liquid electrolyte or solvent directly into a polymer 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 bonds within the polymer, thereby disrupting the structure of the solid electrolyte and resulting in reduced ionic conductivity.

[0037] 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.

[0038] Furthermore, the prior art disclosed in Japanese Patent Application Laid-Open No. 1994-124713 involves vapor deposition of a solvent onto a general PEO (polyethylene oxide) polymer, which has the problem that the internal structure of the polymer collapses due to the lack of a cross-linked structure, making it difficult to ensure ionic conductivity.

[0039] Therefore, the present inventors applied a method of vapor deposition of a polar compound derived from a polar solvent onto a polymer solid electrolyte containing a polymer cross-linked with a polyethylene oxide (PEO)-based copolymer modified with cross-linking functional groups. The polymer solid electrolyte thus prepared includes a polymer containing a PEO-based copolymer containing cross-linking functional groups; and a polar compound, where at least a portion of the cross-linking functional groups form cross-links with each other to form a three-dimensional network structure of the polymer, and the polar compound can be contained within the three-dimensional network structure in a gaseous state or can exhibit a structure bound to the polymer chain.

[0040] It was confirmed that this polymer solid electrolyte exhibits improved ionic conductivity even though it contains a small amount of polar compounds derived from the polar solvent in a gaseous state. This is presumably 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.

[0041] A specific embodiment of a method for producing such a polymer solid electrolyte will now be described in detail.

[0042] Method for producing polymer solid electrolyte According to one embodiment of the present invention, there is provided a method for preparing a polymer solid electrolyte, comprising: (S1) preparing a polymer by crosslinking a polyethylene oxide (PEO)-based copolymer having a crosslinkable functional group; and (S2) vapor-depositing a polar solvent onto the polymer prepared in step (S1); wherein the vapor-deposition step is carried out for a time period that satisfies the following equation 1, thereby controlling the content of the polar compound in the polymer solid electrolyte:

[0043]

number

[0044] In the above formula (1), M(t) is the content of the polar compound contained on the surface or inside of the polymer chain after the polar solvent is vapor-deposited and diffused according to the vapor-deposition time, t is the vapor-deposition time, K is an empirical rate coefficient, which is a fitting parameter for fitting the content of the polar compound (M(t)), where 0.01 < K < 0.1, and n is a transport exponent, which is a fitting parameter for fitting the content of the polar compound (M(t)), where 0.5 ≤ n < 0.7.

[0045] In such a manufacturing method, the above formula (1) is a model that predicts the form (n) of the behavior of the diffusion of the polar solvent based on the correlation between the vapor-deposition time (t) of the polar solvent and the content (M(t)) of the polar compound contained or bonded in the polymer solid electrolyte in a gaseous state by vapor deposition. Since the content (M(t)) of the polar compound is related to the ionic conductivity of the polymer solid electrolyte, by controlling the vapor-deposition time and the content (M(t)) of the polar compound thereby according to the relationship of the above formula (1), the degree of improvement of the ionic conductivity of the polymer solid electrolyte can be improved.

[0046] The above formula (1) is determined based on the fact that in the vapor-deposition step of vapor-depositing the polar solvent so that a polar compound is contained on the surface or inside of the polymer chain, after the polar solvent is adsorbed on the polymer, the form of the diffusion behavior is related to the vapor-deposition time and the content of the polar compound.

[0047] For example, when the polar solvent is vapor-deposited, adsorbed into the polymer, and then diffuses, it exhibits Fickian diffusion behavior. Due to Fickian diffusion, the polar solvent gradually diffuses within the polymer, forming a uniform concentration profile. This allows for the inclusion of trace amounts of polar compounds on the surface or inside of the polymer chains, improving the fluidity of the polymer chains without distorting the internal structure of the polymer, thereby improving the ionic conductivity of the polymer solid electrolyte.

[0048] In contrast, if the polar solvent is simply injected or immersed in a liquid state into the polymer instead of vapor deposition, the polar solvent exhibits non-Fickian diffusion behavior similar to Case II diffusion. Due to Case II diffusion or non-Fickian diffusion behavior similar to Case II diffusion, the polar solvent is rapidly absorbed into the polymer, causing gelation on the polymer surface. The non-uniform concentration distribution within the polymer reduces polymer chain mobility, which can result in a limited increase in the ionic conductivity of the polymer solid electrolyte.

[0049] The vapor deposition process can be performed to form a trace amount of a polar compound on the surface or inside of the polymer chains, which can improve the ionic conductivity of the polymer solid electrolyte. Furthermore, the vapor deposition process allows the polar solvent to gradually diffuse inside the polymer, thereby forming a uniform concentration distribution of the polar solvent within the polymer, which ultimately increases the fluidity of the polymer chains and improves the ionic conductivity.

[0050] Hereinafter, each step of the manufacturing method according to one embodiment will be described in more detail.

[0051] In the step (S1), a polymer in which a PEO (polyethylene oxide) copolymer containing a crosslinkable functional group is crosslinked can be prepared.

[0052] The cross-linking in step (S1) may be carried out in the presence of one or more additional agents selected from the group consisting of a cross-linking agent and an initiator.

[0053] In addition, to form the polymer solid electrolyte, a lithium salt may be further added to the PEO-based copolymer having crosslinkable functional groups during or before the crosslinking reaction step (S1).

[0054] Furthermore, a ceramic compound may be added in step (S1) to form the polymer solid electrolyte.

[0055] Alternatively, the crosslinking may be formed during the drying process after a polymer solution containing the PEO copolymer is applied to a substrate to form a coating film.

[0056] Specifically, the polymer solution can be prepared by mixing the PEO-based copolymer in a solvent, and may additionally be prepared by mixing and dissolving a crosslinker, an initiator, and / or a lithium salt together.

[0057] The solvent is not particularly limited as long as it can dissolve the PEO copolymer, crosslinker, initiator, and / or lithium salt 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. After crosslinking, they are completely removed by drying or other methods.

[0058] The concentration of the polymer solution can be appropriately adjusted taking into consideration the smooth progress of the molding process for preparing the polymer solid electrolyte. Specifically, the concentration of the polymer solution may refer to the concentration (w / w%) of the polymer in the polymer solution. The concentration of the polymer may refer to the concentration of the PEO-based copolymer. For example, the concentration of the polymer 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 polymer solution is less than 5 wt%, the concentration may be excessively diluted, resulting in a decrease in the mechanical strength of the polymer solid electrolyte or in the possibility of it running off when applied to a substrate. If the concentration exceeds 20 wt%, it may be difficult to dissolve the lithium salt in the polymer solution to the desired concentration, or the viscosity may be high, reducing solubility or making it difficult to apply the solution in the form of a uniform thin film.

[0059] The substrate is not particularly limited as long as it serves as a support for the coating film. For example, the substrate may be SUS (stainless steel), a polyethylene terephthalate film, a polytetrafluoroethylene film, a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a vinyl chloride copolymer film, a polyurethane film, an ethylene-vinyl acetate film, an ethylene-propylene copolymer film, an ethylene-ethyl acrylate copolymer film, an ethylene-methyl acrylate copolymer film, or a polyimide film.

[0060] The coating method is not particularly limited as long as it can form a coating film by coating the polymer 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.

[0061] The coating film formed on the substrate by such a coating method can be formed into a polymer from which the residual solvent has been completely removed by a drying process. The drying can be divided into a primary drying process and a secondary drying process to prevent shrinkage of the polymer due to rapid evaporation of the solvent. The primary drying process can remove a portion of the solvent by drying at room temperature, and the secondary drying process can completely remove the solvent by high-temperature drying in a vacuum. The high-temperature drying can be performed at a temperature of 80°C to 130°C. If the high-temperature drying temperature is less than 80°C, the residual solvent cannot be completely removed, and if it exceeds 130°C, the polymer will shrink, making it difficult to form a uniform electrolyte membrane.

[0062] In one embodiment of the present invention, 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-based copolymer may contain multiple types of repeating units each containing one of these functional groups. In addition, 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.

[0063] The cross-linkable functional group means a functional group capable of forming a cross-link between itself and / or each other via a cross-linking agent, and can be bonded to the main chain of a polymer chain in the form of a side chain.

[0064] 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.

[0065] 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:

[0066] [ka]

[0067] [ka]

[0068] [ka]

[0069] 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.

[0070] 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 polymer solid electrolyte, and the inclusion or bonding of the gaseous polar compound within the three-dimensional network structure may provide a polymer solid electrolyte with improved ionic conductivity.

[0071] 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.

[0072] 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 a polymer solution, making molding for preparing a polymer 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 polymer chains and decreasing the ionic conductivity of the polymer solid electrolyte.

[0073] As used herein, a "hydroxy group" refers to an --OH group.

[0074] As used herein, a "carboxyl group" refers to a -COOH group.

[0075] As used herein, an "isocyanate group" refers to a -N=C=O group.

[0076] As used herein, a "nitro group" refers to the -NO2 group.

[0077] As used herein, a "cyano group" refers to a -CN group.

[0078] 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.

[0079] 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.

[0080] As used herein, an "allyl group" refers to the group -CH2-CH=CH2.

[0081] 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 resulting polymer solid electrolyte may not be satisfactory. If the weight-average molecular weight (Mw) of the copolymer is more than 2,000,000 g / mol, the viscosity increases, reducing solubility during polymer solution preparation, making molding for producing a polymer solid electrolyte difficult. In addition, the ionic conductivity of the polymer solid electrolyte may decrease due to a decrease in chain mobility caused by an increase in crystallinity within the polymer solid electrolyte.

[0082] In particular, when the repeating number of the repeating unit of Formula 3 containing a cross-linking functional group among l, m, and n exceeds 1000, the degree of cross-linking increases excessively, which may reduce the mobility of the polymer chain and decrease the ionic conductivity of the polymer solid electrolyte.

[0083] The copolymer may also be a random copolymer or a block copolymer.

[0084] In one embodiment of the present invention, the polymer solid electrolyte may include cross-links between cross-linkable functional groups. The polymer solid electrolyte may further include a cross-linking agent, thereby further including cross-links between the cross-linking agent and the cross-linkable functional groups. 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.

[0085] 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.

[0086] Furthermore, when a crosslinking agent is added in the process of producing the polymer solid electrolyte, a crosslinking bond may be formed between the crosslinking agent and the crosslinkable functional group, and the crosslinking bond 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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, paramethane hydroperoxide (p-methyl hydroperoxide), and 2,2'-azobis(2-methylpropionitrile).

[0091] 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.

[0092] In one embodiment of the present invention, 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 polymer 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 are therefore mobile during charge / discharge of the battery.

[0093] 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, and 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.

[0094] 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 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 polymer solid electrolyte may decrease, and if it exceeds 45 parts by weight, the mechanical strength may decrease.

[0095] Meanwhile, in the manufacturing method according to the embodiment described above, the ceramic compound has a lithium ion transfer ability for improving the conductivity of lithium ions, and preferably contains lithium atoms and has a function of transferring lithium ions without storing lithium, thereby improving the ionic conductivity of the polymer solid electrolyte in the form of a composite solid electrolyte.

[0096] The ceramic compound may be contained in the internal space of the cross-linked polymer chains, for example, in the three-dimensional network structure, in a uniformly dispersed state. The ceramic compound may be added during the cross-linking process and be uniformly dispersed without clumps in the internal space of the polymer chains formed by cross-linking. Such a uniformly dispersed ceramic compound may be advantageous for improving the mechanical strength and ionic conductivity of the polymer solid electrolyte.

[0097] 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 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, while if the diameter is more than 1000 nm, the dispersibility may be reduced due to increased aggregation between particles, making uniform dispersion difficult.

[0098] The ceramic chemicals may be oxide-based or phosphate-based compounds, and may be oxide-based solid electrolytes in the form of, for example, lithium metal oxide or lithium metal phosphate. More specifically, the ceramic compounds may be 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.

[0099] The oxide-based or phosphate-based oxide-based solid electrolyte 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.

[0100] 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 polymer solid electrolyte contains the ceramic compound, it is possible to improve the mechanical strength of the solid electrolyte as well as the high-temperature stability and ionic conductivity.

[0101] 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.

[0102] If the ceramic compound is contained in an excessively small amount, the polymer crystallinity and amorphous effect of the ceramic compound are reduced, resulting in a small increase in the ionic conductivity of the polymer solid electrolyte, and the mechanical properties may not reach the expected level due to the formation of a composite.

[0103] 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 solid electrolyte with reduced ionic conductivity.

[0104] Meanwhile, in step (S2), a polar solvent is vapor-deposited onto the polymer prepared in step (S1), thereby producing a polymer solid electrolyte in which gas molecules of the polar solvent are bound to the polymer chains or the gaseous polar compound is contained within the internal space of the polymer chains, e.g., a three-dimensional network structure. In this case, the gas molecules of the polar solvent may correspond to the polar compound.

[0105] In this case, the vapor deposition step may be performed for a time period that satisfies the following equation 1 to control the content of the polar solvent (or gaseous polar compound) in the polymer solid electrolyte:

[0106]

number

[0107] In the above formula 1, M(t) is the content of the polar compound on the surface or inside of the polymer chain after the polar solvent is vapor-deposited and diffused depending on the vapor deposition time; t is the vapor deposition time, K is the empirical rate coefficient, a fitting parameter for fitting the content of polar compounds (M(t)), and is 0.01 <K<0.1であり、 n is the transport exponent, which is a fitting parameter for fitting the polar compound content (M(t)), and is 0.5≦n<0.7.

[0108] M(t) refers to the content of gaseous polar compounds contained on or within the polymer chains after the polar solvent is vapor-deposited and diffused depending on the vapor deposition time. The content of the polar compounds increases in proportion to the vapor deposition time (t) at the beginning of vapor deposition. However, after a certain vapor deposition time (t), the increase rate decreases and the content tends to converge to a specific value. Because the adsorption and desorption behavior of the polar solvent is similar within the polymer, M(t) can be measured using a desorption amount measurement device. For example, M(t) can be obtained by measuring the desorption amount of the polar solvent over time while heating at 60°C using an MS-70 analyzer (AND, Japan). Preferably, the content of the polar compounds may be 0.1 wt% or more and less than 10 wt%. For example, the content of the polar compounds may be 0.1 wt% or more, 1 wt% or more, or 5 wt% or less, 6 wt% or less, 7 wt% or less, 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 formation within the polymer, and the ionic conductivity of the polymer solid electrolyte is not improved. If the content of the polar compound is 10 wt% or more, the polymer solid electrolyte has a high liquid content, exhibiting the properties of a semi-solid battery, and further, the mechanical strength of the polymer solid electrolyte is reduced due to gelation of the polymer.

[0109] The t represents the vapor deposition time. It may represent the time elapsed since the vapor deposition begins. The method or device for measuring the vapor deposition time is not particularly limited. For example, the vapor deposition time can be measured using various means capable of determining the time at a specific point in time.

[0110] The K is an empirical rate coefficient and corresponds to a fitting parameter for fitting the polar compound content (M(t)) using Equation 1. The K is directly related to the polar compound content (M(t)) adsorbed by the polymer when the polar solvent is vapor-deposited. The range of K required in the solvent vapor deposition process of the present invention is 0.01 <K<0.1であってもよい。

[0111] The n is a transport exponent and corresponds to a fitting parameter for fitting the polar compound content (M(t)) using Equation 1. The n is related to the tendency and behavior of the polar solvent to diffuse within the polymer after vapor deposition, and the range of n required in the solvent vapor deposition process of the present invention is 0.5≦n<0.7. When the n is within this range, Fickian diffusion behavior can be exhibited.

[0112] The vapor deposition can be performed by contacting the vapor of the polar solvent generated by heating or at room temperature with the polymer and allowing it to penetrate into the polymer. In this way, by vapor deposition at room temperature or by heating, the gaseous polar compound can be uniformly diffused on the surface and / or inside of the polymer, and the polar compound gas molecules can be bound to the polymer chains or can be contained in the interior space of the polymer chains in a uniformly dispersed or diffused form.

[0113] When the polar solvent is placed at room temperature during vapor deposition, a small amount of the polar solvent with a low boiling point gradually vaporizes at room temperature and penetrates into the polymer, effectively inducing a conformational change in the cross-linked polymer chains within the polymer.

[0114] Furthermore, heating the polar solvent during the vapor deposition can improve the vapor deposition rate. The heating temperature is not particularly limited as long as it is a temperature at which the polar solvent can change phase to vapor, and may be, for example, 30°C to 80°C. While typical PEO melts at 60°C, the PEO copolymer modified with cross-linking functional groups has improved heat resistance and can withstand temperatures up to 80°C when a cross-linked structure is formed, further increasing the vapor deposition rate. The heating method is not limited as long as it can provide energy to generate vapor. Examples of suitable methods include, but are not limited to, direct heating using a burner or fan, or indirect heating using a heater or steam tube.

[0115] If the heating temperature is too high, the polar solvent may boil above its boiling point, the solvent may undergo structural changes, or polymer deformation may occur. Furthermore, it is difficult to control the evaporation rate of the polar solvent during vapor deposition. Therefore, in order to vapor deposit a small amount of polar solvent, it is preferable to perform vapor deposition at a heating temperature within the appropriate range as defined above.

[0116] As previously described, polymer solid electrolytes can be prepared with polar compounds, such as polar solvent molecules, attached to cross-linked polymer chains or contained within the internal spaces between the polymer chains by vapor deposition.

[0117] According to the above-described method for producing a polymer solid electrolyte, the degree of improvement in ionic conductivity of the polymer solid electrolyte can be maximized in the vapor deposition step (S2) based on the correlation between the vapor deposition time defined by Equation 1 and the gaseous polar compound contained in the polymer solid electrolyte.

[0118] Polymer solid electrolyte The polymer solid electrolyte manufactured according to the above-described embodiment includes a polymer including a polyethylene oxide (PEO) copolymer containing cross-linkable functional groups; and a polar compound, wherein at least a portion of the cross-linkable functional groups of the copolymer form cross-links with each other, causing the polymer to form 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.

[0119] In addition, in the polymer solid electrolyte, at least a portion of the cross-linkable functional groups may form cross-links with each other via a cross-linking agent, and the polymer solid electrolyte may further include a lithium salt.

[0120] Furthermore, the polymer solid electrolyte may be a composite solid electrolyte further including a ceramic compound.

[0121] Meanwhile, the types and contents of the components of the polymer solid electrolyte have been described above, and therefore, further explanations thereon will be omitted.

[0122] In the solid electrolyte, the gaseous polar compound may be dispersed among the polymer chains forming the three-dimensional network structure, or may be adsorbed or bound to the surface or interior of the polymer chains. Such polar compounds are gas molecules of the polar solvent used in the vapor deposition process, and can be adsorbed to the polymer during vapor deposition and then diffused into the interior of the polymer chains. As a result, a solid electrolyte having the above structure can be manufactured. The polar compound may be bound to the polymer chains or dispersed in the internal space between the polymer chains, thereby improving the ionic conductivity of the final polymer solid electrolyte.

[0123] Such a polymer 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 vapor deposition. Such a polymer 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 same 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 a solid electrolyte, a liquid component or a component exhibiting wettability can be observed on the surface of the electrolyte layer. Furthermore, a polymer solid electrolyte containing the polar compound in a gaseous state by vapor deposition exhibits significantly higher ionic conductivity than a polymer solid electrolyte containing the polar compound in a gaseous state by vapor deposition. A comparison of ionic conductivities also confirms the existence of a polymer solid electrolyte containing the polar compound in a gaseous state by vapor deposition.

[0124] Specifically, polar compounds bound to the polymer chains or contained in the internal space between the polymer chains can act as plasticizers to plasticize the polymer. The plasticized polymer increases the amorphous region inside, improving the mobility of the polymer chains. The improved mobility of the polymer chains increases the ion hopping effect inside the polymer, improving the ionic conductivity of the polymer solid electrolyte.

[0125] 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 influx of polar compounds into the polymer increases the cation solvation effect of lithium ions, improving ion mobility and, therefore, the ionic conductivity of the polymer solid electrolyte.

[0126] The polar compound may be one or more compounds selected from the group consisting of carbonate compounds and sulfonyl compounds.

[0127] 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.

[0128] 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 solid electrolyte. For example, the content of the polar compound may be 0.1 wt % or more, 1 wt % or more, or 5 wt % or less, 6 wt % or less, 7 wt % or less, 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 polymer solid electrolyte is not improved. If the content of the polar compound is 10 wt % or more, the polymer solid electrolyte contains too much liquid, exhibiting the properties of a semi-solid battery and also reducing the mechanical strength of the polymer solid electrolyte due to gelation of the polymer.

[0129] all solid state battery An additional embodiment of the invention also relates to an all-solid-state battery including the solid electrolyte, the all-solid-state battery including a negative electrode, a positive electrode, and a solid electrolyte interposed between the negative electrode and the positive electrode, wherein the solid electrolyte is produced according to the above-described embodiment.

[0130] Specifically, the solid electrolyte includes a polymer in which a polyethylene oxide (PEO) copolymer containing a cross-linkable functional group is cross-linked and a gaseous polar compound, and the gaseous polar compound is contained or bonded thereto, and optionally, a ceramic compound is uniformly dispersed therein to improve ionic conductivity, making the solid electrolyte suitable for use as an electrolyte for an all-solid-state battery.

[0131] 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.

[0132] The positive electrode active material layer includes a positive electrode active material, a binder, and a conductive material.

[0133] The positive electrode active material is not particularly limited as long as it is a material capable of reversibly absorbing and releasing lithium ions, and examples thereof include lithium cobalt oxide, lithium nickel oxide, Li[NixCoyMnzMv]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(LiaMb-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 to 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-yNi-site lithium nickel oxide represented by MyO2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and y = 0.01 to 0.3); chemical formula LiMn 2-y M y Examples of suitable lithium manganese composite oxides include, but are not limited to, lithium manganese composite oxides expressed as Li2Mn3MO8 (where M is Co, Ni, Fe, Cr, Zn, or Ta, and y is 0.01 to 0.1) or Li2Mn3MO8 (where M is Fe, Co, Ni, Cu, or Zn); LiMn2O4, in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion; disulfide compounds; and Fe2(MoO4)3.

[0134] 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 and the electrical properties may be insufficient, and if it exceeds 80 wt %, the mass transfer resistance may be high.

[0135] Furthermore, the binder is a component that assists in binding 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 styrene-butadiene rubber, polytetrafluoroethylene, carboxymethyl cellulose, 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.

[0136] 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.

[0137] 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.

[0138] 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.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] Such a positive electrode can be manufactured by a conventional method. Specifically, a positive electrode active material, a conductive material, and a binder are mixed in an organic solvent to form a positive electrode active material layer. The resulting composition is then applied to a positive electrode current collector, dried, and optionally, compressed into a current collector to improve electrode density. Preferably, the organic solvent used is one that can uniformly disperse the positive electrode active material, binder, and conductive material and is easily evaporated. Specific examples include acetonitrile, methanol, ethanol, tetrahydrofuran, water, isopropyl alcohol, dimethyl sulfoxide (DMSO), and N-methyl-2-pyrrolidone (NMP).

[0143] 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.

[0144] The negative electrode active material may include a material capable of reversibly intercalating or deintercalating lithium (Li+), a material capable of reversibly forming a lithium-containing compound by reacting with lithium ions, lithium metal, or a lithium alloy.

[0145] 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 ions (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).

[0146] Preferably, the negative electrode active material may be lithium metal, specifically in the form of a lithium metal thin film or lithium metal powder.

[0147] 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 electrical properties may be insufficient, and if it exceeds 80 wt %, the mass transfer resistance may be high.

[0148] The binder is the same as that described above in the positive electrode active material layer.

[0149] Furthermore, the conductive material is as described above in the positive electrode active material layer.

[0150] 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.

[0151] 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 case where a thin metallic lithium film is formed on a metal plate by initial charging after a battery is assembled without a thin lithium film on the negative electrode current collector.

[0152] Meanwhile, 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.

[0153] 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.

[0154] 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.

[0155] In the following examples and comparative examples, when preparing the polymer solid electrolyte and the composite solid electrolyte, Example 1 and Comparative Example 1 were carried out using a "solvent vapor deposition method" in which a polar solvent was vapor-deposited, and Example 2 and Comparative Example 2 were carried out using a "solvent impregnation method" in which the electrolyte was impregnated with a polar solvent.

[0156] Furthermore, all of the solid electrolytes prepared in the following Examples and Comparative Examples belong to the category of polymer solid electrolytes. However, Example 2 and Comparative Example 2 are the same as Example 1 and Comparative Example 1 except that a ceramic compound is added, and for the purpose of distinguishing them, the terms "polymer solid electrolyte" and "composite solid electrolyte" are used.

[0157] Example Example 1: Preparation of polymer solid electrolyte 1) Preparation of polymers including copolymers A polyethylene oxide (PEO)-based copolymer of the following formula 1a was prepared:

[0158] [ka]

[0159] 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.

[0160] The copolymer of formula 1a has an allyl group linked via a methylene oxide linker as a cross-linking functional group.

[0161] The polyethylene oxide copolymer was mixed with trimethylolpropane trimethacrylate as a crosslinker, benzoyl peroxide as an initiator, and LiTFSI as a lithium salt in acetonitrile as a solvent to prepare a polymer solution, which was then stirred for 24 hours using a magnetic bar. The polymer solution had a composition of 100 parts by weight of the polyethylene oxide copolymer, 20 parts by weight of trimethylolpropane trimethacrylate as a crosslinker, 1 part by weight of benzoyl peroxide as an initiator, and 36.5 parts by weight of the lithium salt, and acetonitrile was used as a solvent so that the concentration of the polyethylene oxide copolymer in the polymer solution was 10.4%.

[0162] The prepared polymer solution was solution-cast onto the lower substrate of a coin cell, and then primarily dried at room temperature for 12 hours, followed by secondary drying at 100°C for 12 hours to induce cross-linking, thereby preparing an electrolyte film with a thickness of 200 μm.

[0163] 2-step) Preparation of polymer solid electrolyte The polymer was attached to the upper plate of a chamber, and the lower part of the chamber was filled with ethyl methyl carbonate (EMC) solvent. The solution was allowed to evaporate at room temperature for 72 hours, and then ethyl methyl carbonate (EMC) vapor was introduced into the interior of the polymer attached to the upper part of the chamber to deposit it on the polymer, producing a polymer solid electrolyte.

[0164] Example 2: Preparation of composite solid electrolyte In step 1) of Example 1, a composite solid electrolyte was prepared in the same manner as in Example 1, except that a mixed solution was prepared by mixing 20 parts by weight of a crosslinking agent, trimethylolpropane trimethacrylate, 1 part by weight of an initiator, benzoyl peroxide, 36 parts by weight of a lithium salt, and 40 parts by weight of a ceramic compound, LSTP, with 100 parts by weight of a polyethylene oxide copolymer, and an acetonitrile solvent was used so that the concentration of the polymeric polyethylene oxide copolymer in the mixed solution was 11.1% and the concentrations of the polymeric polyethylene oxide copolymer and the ceramic compound were 14.9%.

[0165] Comparative Example Comparative Example 1: Modified PEO + Liquid-Rich Polymer Solid Electrolyte A polymer solid electrolyte was prepared in the same manner as in Example 1, except that EMC solvent was directly injected into the polymer solid electrolyte prepared in step 1) of Example 1.

[0166] Comparative Example 2: Modified PEO + Liquid-Rich Composite Solid Electrolyte A composite solid electrolyte was prepared in the same manner as in Example 2, except that the EMC solvent was directly injected into the composite solid electrolyte prepared in step 1) of Example 2.

[0167] Experimental example Experimental Example 1: Confirmation of the correlation between the content of polar compounds and the diffusion behavior of polar solvents The correlation between the diffusion behavior of polar solvents and ionic conductivity was confirmed by fitting the measured polar compound content (M(t)) with fitting parameters K and n using Equation 1 below:

[0168]

number

[0169] In the above formula 1, M(t) is the content of the polar compound on the surface or inside of the polymer chain after the polar solvent is vapor-deposited and diffused depending on the vapor deposition time; t is the vapor deposition time, K is the empirical rate coefficient, a fitting parameter for fitting the content of polar compounds (M(t)), and is 0.01 <K<0.1であり、 n is the transport exponent, which is a fitting parameter for fitting the polar compound content (M(t)), and is 0.5≦n<0.7.

[0170] In the above formula (1), the polar compound content (M(t)) can be measured by using a balance to monitor the weight of the liquid phase evaporating over time while heating the solid electrolyte test piece. For example, using a heated electronic balance (AND Corp. MS-70), the test piece can be heated at a temperature of 55 to 70°C or at 60°C while monitoring the weight of the liquid phase evaporating over time. When the amount of polar compound evaporating over time reaches saturation, the saturation amount at that time 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).

[0171] Using the above equation 1, a graph was created showing the correlation between the measured polar compound content (M(t)) and the amount of change (ΔM(t)) when the vapor deposition time (t) was between 0 and 500 seconds (Figures 1 and 2), and the fitting parameters K and n, which indicate the behavior of the polar solvent, were obtained.

[0172] FIG. 1 is a graph showing the change in the diffusion behavior of the polar solvent in the polymer and the content of the vapor-deposited polar compound as a function of vapor deposition time during the solvent vapor deposition process according to Example 1 of the present invention, and FIG. 2 is a graph showing the change in the behavior of the polar solvent in the polymer and the content of the impregnated polar compound as a function of impregnation time during the solvent impregnation process according to Comparative Example 1 of the present invention.

[0173] Referring to FIGS. 1 and 2, both Example 1 and Comparative Example 1 correspond to graphs of the function of Equation 1. The diffusion behavior of the polar solvent vapor-deposited on the polymer in Example 1 is similar to Fickian diffusion, while the diffusion behavior of the polar solvent impregnated in the polymer in Comparative Example 1 is similar to non-Fickian diffusion, which suggests that gelation will occur.

[0174] The fitting parameters K and n were determined while fitting the graphs of FIGS. 1 and 2, and the results are shown in Table 1 below.

[0175] The ionic conductivity was determined by the following method.

[0176] To measure the ionic conductivity of the polymer solid electrolytes prepared in the examples and comparative examples, a 1.7671 cm 2 The polymer solid electrolyte was formed on the lower substrate of a coin cell of the same size, and then SUS was used as an inert electrode (blocking electrode) to prepare a coin cell for measuring ionic conductivity.

[0177] 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 polymer solid electrolyte was calculated using the following Equation 2:

[0178]

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[0179] In the above formula 2,

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[0180] [Table 1]

[0181] As shown in Table 1, when comparing Example 1 and Comparative Example 1, which are both polymer solid electrolytes, Example 1, which was subjected to a vapor deposition process, had a higher solubility than Comparative Example 1, which was subjected to a solvent impregnation method.

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Claims

1. (S1) preparing a polymer crosslinked from a PEO (polyethylene oxide) copolymer containing a crosslinkable functional group; and (S2) vapor-depositing a polar solvent onto the polymer prepared in (S1); The vapor deposition step is carried out for a time period that satisfies the following formula 1, thereby controlling the content of the polar compound in the polymer solid electrolyte: [Equation 1] In the above formula 1, M(t) is the content of the polar compound on the surface or inside of the polymer chain after the polar solvent is vapor-deposited and diffused depending on the vapor deposition time; t is the vapor deposition time, K is an empirical rate coefficient, which is a fitting parameter for fitting the content of polar compounds (M(t)), and is 0.01<K<0.1; n is a transport exponent, which is a fitting parameter for fitting the polar compound content (M(t)), and is 0.5≦n<0.

7.

2. The method for preparing a polymer solid electrolyte according to claim 1 , wherein step (S1) is performed in the presence of at least one additional agent selected from the group consisting of a crosslinking agent and an initiator.

3. The method for preparing a polymer solid electrolyte according to claim 1 , wherein a lithium salt is further added before or during step (S1).

4. The method of claim 1 , wherein a ceramic compound is further added during the cross-linking in step (S1).

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 polymer 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 polymer 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 1】 【Chemistry 2】 【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. 2. The method of claim 1, wherein in step (S2), the vapor of the polar solvent is deposited on the polymer so that the content of the polar solvent is 0.1 wt % or more and less than 10 wt % based on the total weight of the polymer solid electrolyte.

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

9. 9. The method for producing a polymer 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.

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