Method for producing polymer solid electrolytes

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 of related applications This application claims priority rights under Korean Patent Application No. 10-2022-0132780 dated October 14, 2022, and Korean Patent Application No. 10-2023-0136067 dated October 12, 2023, and all content disclosed in the documents of said Korean Patent Applications is incorporated herein by reference.

[0002] This invention relates to a method for producing polymer solid electrolytes. [Background technology]

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

[0004] Lithium-ion batteries using solid electrolytes offer several advantages, including increased battery safety, prevention of electrolyte leakage, improved battery reliability, and ease of manufacturing thin batteries. Furthermore, the ability to use lithium metal as the negative electrode increases energy density, leading to expectations of applications in small secondary batteries and high-capacity secondary batteries for electric vehicles, making them a promising next-generation battery.

[0005] Among solid electrolytes, composite electrolytes of polyethylene oxide (PEO) and lithium salts have the advantage of higher ignition stability compared to existing liquid electrolytes. However, the high crystallinity of polyethylene oxide (PEO) makes it difficult to manufacture polymer solid electrolytes with improved ionic conductivity. In other words, the high crystallinity of polymers inhibits the chain mobility of polymer chains, thus 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, techniques have been developed to improve the ionic conductivity of polymer solid electrolytes by modifying the structure of crystalline polymers or by adding a separate plasticizer to the polymer to improve the mobility of the polymer chains. However, solid polymer electrolytes manufactured using the aforementioned polymer structure modification or plasticizer addition methods may have difficulty achieving an ionic conductivity of 0.1 mS / cm or higher.

[0007] Attempts have been made to improve ionic conductivity by directly adding a liquid electrolyte or solvent in a liquid state to the aforementioned polymer solid electrolyte. However, this is not a solid electrolyte for pure all-solid-state batteries, but rather a technology for electrolytes in semi-solid-state batteries where solid and liquid coexist. As a result, safety issues such as leakage of the liquid electrolyte still exist, and the improvement in ionic conductivity is not always sufficient.

[0008] Therefore, in addition to polymer solid electrolytes produced by structural deformation of polymers, addition of separate plasticizers, or immersion of solid electrolytes in liquid electrolytes, there is a need for the development of technologies that can improve the ionic conductivity of the electrolyte, as well as for pure solid electrolytes 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 vapor-depositing a trace amount of the solvent, and to provide a method for producing a polymer solid electrolyte that can control the behavior of the polar solvent vapor-deposited on the polymer and maximize the degree of improvement in ionic conductivity.

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 a 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 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)), 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)), 0.5 ≤ n < 0.7.

[0014] In the manufacturing method, the step (S1) is carried out in the presence of one or more additional substances selected from the group consisting of a crosslinking agent and an initiator, and the crosslinking step may be carried out.

[0015] Also, in the manufacturing method, a lithium salt may be further added at or before the step (S1), and a ceramic compound may be further added during the crosslinking of the step (S1).

[0016] On the other hand, in the manufacturing method, the crosslinkable functional group contained in the PEO-based copolymer can be bonded via an alkylene linker or an alkylene oxide linker having 0 to 10 carbon atoms (where the alkylene linker having 0 carbon atoms represents a single bond) in the main chain of the PEO-based copolymer, 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)-based copolymer containing the crosslinkable functional group may be a copolymer containing the repeating units of the following Chemical Formulas 1 to 3:

[0018]

Chemical Formula

[0019]

Chemical Formula

[0020]

Chemical Formula

[0021] In the above chemical formulas 1 to 3, R1 is -CH2-O-(CH2-CH2-O) k -R3 is represented, where k is 0 to 20, R3 represents an alkyl group having 1 to 5 carbon atoms, R2 represents a substituent in which one or more crosslinking functional groups selected from the group consisting of hydroxyl group, carboxyl group, isocyanate group, nitro group, cyano group, amine group, amide group, epoxy group, and allyl group are bonded to the polymer chain via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (where the alkylene linker having 0 carbon atoms shows a single bond), l, m, and n are the number of repeats in the repeating unit, where l and n are each independently integers from 1 to 1000, and m is an integer from 0 to 1000.

[0022] On the other hand, in step (S2) of the manufacturing method, the vapor of the polar solvent can be deposited onto the polymer such that the content of the polar solvent is 0.1% by weight or more and less than 10% by weight on a total weight basis of the polymer solid electrolyte.

[0023] Furthermore, the polar solvent may correspond to the polar compound deposited in a gaseous state on the polymer solid electrolyte and may include one or more selected from the group consisting of carbonate-based solvents and sulfonyl-based solvents. More specifically, the polar solvent may include one or more 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 producing polymer solid electrolytes of 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 crosslinking by vapor deposition, or bonded onto the crosslinked polymer.

[0025] As a result, by gradually injecting a small amount of polar solvent in a gaseous state into the solid electrolyte, gelation is prevented, the relaxation time of the internal polymer chains is delayed, and the mobility of the polymer chains is improved, thereby improving ionic conductivity without a decrease in mechanical properties.

[0026] Furthermore, since the tendency for the ionic conductivity of the polymer solid electrolyte to increase differs depending on the method by which the polar solvent diffuses into the polymer after being deposited on it in the vapor deposition process, the effect of improving the ionic conductivity of the polymer solid electrolyte can be maximized by controlling the behavior of the polar solvent that is vapor-deposited and adsorbed within the polymer based on this tendency. Specifically, by controlling the content of the gaseous polar compound according to the vapor deposition time, the ionic conductivity of the polymer solid electrolyte can be more effectively achieved within a desired range.

[0027] Furthermore, the polymer solid electrolyte can exhibit improved ionic conductivity by increasing the mobility of the polymer chains, while maintaining the inherent structural properties of the polymer without deformation or destruction of the material.

[0028] Furthermore, in the case of a composite solid electrolyte form in which ceramic compounds are further added, improved ionic conductivity can be achieved due to the uniform distribution of the ceramic particles. The polymer solid electrolyte can also exhibit improved ionic conductivity and mechanical properties by containing trace amounts of polar compounds in a gaseous state. [Brief explanation of the drawing]

[0029] [Figure 1] This graph shows the diffusion behavior of the polar solvent in the polymer and the change in the content of the deposited polar compound as a result of the vapor deposition time during the solvent vapor deposition process according to Example 1. [Figure 2] This graph shows the behavior of the polar solvent in the polymer and the change in the content of the impregnated polar compound as the impregnation time during the solvent impregnation process according to Comparative Example 1. [Modes for carrying out the invention]

[0030] The following describes specific embodiments in more detail to help understand the invention.

[0031] Terms and words used herein and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner and concept consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors can appropriately define the concepts of terms in order to best describe their invention.

[0032] The term "bonding" as used herein relates to a form in which a polar compound is "bonded" to a polymer chain, such as a PEO copolymer chain, and "bonding" broadly refers to a form in which a polar solvent molecule, in the gaseous state, is fixed to the polymer chain by vapor deposition of a polar solvent. In other words, "bonding" does not mean that it is limited to a specific type of physical bond, chemical bond, etc., but rather includes a state fixed by various bonds, including these physical and chemical bonds, or a state fixed by simple attachment such as adsorption, or a state in which it is contained within a three-dimensional network structure formed by the crosslinking of the polymer and fixed adjacent to the polymer chain or crosslinking structure.

[0033] As used herein, the term "three-dimensional network structure" refers to a structure comprising a three-dimensional solid-shaped frame and an internal space formed by the frame, wherein the frame may include polymer chains comprising crosslinks formed by the crosslinkable functional groups, for example, crosslinks between crosslinkable functional groups and / or crosslinks between crosslinkable functional groups and crosslinking agents. The three-dimensional network structure may also be referred to as a crosslinked structure.

[0034] In this specification, the presence or inclusion of a polar compound (polar solvent) in a polymer solid electrolyte in a "gaseous state" is distinguished from the case where the polar solvent or the electrolyte containing it is injected in a liquid state. This distinction means that the polar compound is vapor-deposited and exists in a state distinct from the liquid-injected electrolyte immediately after the manufacture of the polymer solid electrolyte or during the charge-discharge process of an all-solid-state secondary battery containing it. However, depending on the storage or operating conditions of the polymer solid electrolyte and / or secondary battery, the vapor-deposited polar compound may be in a locally or temporarily liquefied state. Even in this case, the vapor-deposited polar compound exhibits higher mobility than the polar solvent injected in a liquid state and shows a different state from the liquid polar solvent, and is therefore considered to be present or contained in a "gaseous state."

[0035] As used herein, the term "polymeric solid electrolyte" means a polymeric solid electrolyte comprising, as essential components, (i) a polymer containing a PEO (polyethylene oxide) copolymer having crosslinkable functional groups; and a polar compound; or (ii) a polymeric solid electrolyte comprising a ceramic compound in (i). The polymeric solid electrolyte in (ii), further comprising a ceramic compound in (i), may be referred to as a "composite solid electrolyte."

[0036] On the other hand, conventionally, to improve the ionic conductivity of a solid electrolyte, the solid electrolyte was either immersed in or supported in a liquid electrolyte or solvent, or the liquid electrolyte or solvent was directly injected into the solid electrolyte in a liquid state. When a liquid electrolyte or solvent is directly added to a solid electrolyte in this way, it does have the effect of improving the ionic conductivity of the solid electrolyte, but this is merely an effect of increasing the ionic conductivity of the solid electrolyte due to the high ionic conductivity of the liquid itself, and the degree of improvement is not sufficient, requiring the injection of a considerable amount of liquid electrolyte or solvent. In other words, lithium ion conduction is carried out by the liquid electrolyte added to the solid electrolyte rather than by the intrinsic properties of the solid electrolyte, so it is far from improving the properties of the solid electrolyte itself. Furthermore, when a liquid electrolyte or solvent is directly added or injected into a polymer solid electrolyte in a liquid state, there was a problem in that undesirable side reactions between the polymer and the liquid phase could damage the polymer chains or break bonds within the polymer, disrupting the structure of the solid electrolyte and reducing its ionic conductivity.

[0037] Furthermore, when a solvent or liquid electrolyte is directly injected into a solid electrolyte, the rapid diffusion of liquid phase molecules into the solid electrolyte can cause rapid relaxation of polymer chains, promoting gelation at the surface. This can lead to a decrease in mechanical properties, and problems such as leakage of the liquid electrolyte may not be completely resolved.

[0038] Furthermore, in the case of the conventional technology, Japanese Patent Publication No. 1994-124713, a solvent is vapor-deposited onto a general PEO (polyethylene oxide) polymer, and in this case, there was a problem in that the internal structure of the polymer collapsed due to the lack of a cross-linking structure, and ionic conductivity could not be ensured.

[0039] Therefore, the inventors applied a method of vapor deposition of a polar compound derived from a polar solvent to a polymeric solid electrolyte containing a polymer formed by crosslinking a PEO (polyethylene oxide) copolymer modified with crosslinking functional groups. The polymeric solid electrolyte thus produced contains a polymer containing a PEO copolymer containing crosslinking functional groups, and a polar compound, wherein at least a portion of the crosslinking functional groups form crosslinks with each other, forming a three-dimensional network structure in the polymer, and the polar compound can be contained within the three-dimensional network structure in a gaseous state or exhibit a structure bonded to the polymer chain.

[0040] Such polymeric solid electrolytes were found to exhibit improved ionic conductivity despite containing trace amounts of polar compounds derived from polar solvents in a gaseous state. This is predicted to be because the gaseous polar compounds affect the physical properties of the PEO copolymer, such as its crystallinity, increasing the chain mobility of the polymer chains, thereby improving the lithium ion conductivity contained in the polymeric solid electrolyte.

[0041] The following describes in detail a specific embodiment of the manufacturing method for producing such polymer solid electrolytes.

[0042] Method for producing polymer solid electrolytes According to one embodiment of the present invention, a method for producing a polymer solid electrolyte is provided, comprising the steps of (S1) producing a polymer by crosslinking PEO (polyethylene oxide) copolymers containing crosslinkable functional groups; and (S2) vapor deposition of a polar solvent onto the polymer produced in step (S1), wherein the vapor deposition step is carried out for a time satisfying the following formula 1 to adjust 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 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 and 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 and 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 resulting content (M(t)) of the polar compound according to the relationship of the above formula (1), the degree of improvement of the ionic conductivity of the polymer solid electrolyte can be enhanced.

[0046] The above formula (1) is determined based on the fact that in the vapor-deposition process of vapor-depositing the polar solvent so that a polar compound is contained in 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 and adsorbed onto the polymer, it exhibits Fickian diffusion behavior. Due to Fickian diffusion behavior, the polar solvent gradually diffuses within the polymer, forming a uniform concentration profile. This makes it possible to adjust the amount of polar compound contained on the surface or inside the polymer chain, improving only the fluidity of the polymer chain without deforming 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 the polymer in a liquid state 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 by the polymer, leading to gelation on the polymer surface. This results in a non-uniform concentration distribution within the polymer, which reduces the chain mobility of the polymer chains and may not significantly increase the ionic conductivity of the polymer solid electrolyte.

[0049] The vapor deposition process can be carried out to form a trace amount of a polar compound on the surface or inside the polymer chain, which can improve the ionic conductivity of the polymer solid electrolyte. Furthermore, the vapor deposition process can be carried out to allow the polar solvent to gradually diffuse inside the polymer, thereby creating a uniform concentration distribution of the polar solvent within the polymer, ultimately increasing the fluidity of the polymer chain and improving its ionic conductivity.

[0050] The manufacturing method of one embodiment will be described in more detail below, step by step.

[0051] In step (S1) above, a polymer can be produced by crosslinking PEO (polyethylene oxide) copolymers containing crosslinkable functional groups.

[0052] The crosslinking in step (S1) can be carried out in the presence of one or more additional substances selected from the group consisting of crosslinking agents and initiators.

[0053] Furthermore, in order to form the polymer solid electrolyte, when the crosslinking reaction step of step (S1) is carried out, or in a step prior to that, a lithium salt may be further added to the PEO copolymer having the crosslinkable functional group.

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

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

[0056] Specifically, the polymer solution can be produced by mixing the PEO-based copolymer with a solvent, and may also be produced by mixing and dissolving a crosslinking agent, an initiator, and / or a lithium salt together.

[0057] The solvent is not particularly limited as long as it can dissolve the PEO copolymer, crosslinking agent, initiator, and / or lithium salt in a mixture and can be easily removed by a drying step. For example, the solvent may be acetonitrile, methanol, ethanol, tetrahydrofuran, water, isopropyl alcohol, dimethyl sulfoxide (DMSO), methylpyrrolidone (NMP), or dimethylformamide (DMF). Such a solvent is a reaction medium for crosslinking and is distinct from polar solvents contained in liquid electrolytes, etc., and is completely removed by drying or other means after crosslinking.

[0058] The concentration of the polymer solution can be appropriately adjusted, taking into consideration the degree to which the molding process for manufacturing the polymer solid electrolyte can proceed smoothly. Specifically, the concentration of the polymer solution may mean the concentration of polymer (w / w%) in the polymer solution. The concentration of polymer may also mean the concentration of PEO copolymer. For example, the concentration of the polymer solution may be 5% to 20% by weight, and specifically, it may be 5% or more by weight, 7% or more by weight, or 9% or more by weight, or 13% or less by weight, 17% or less by weight, or 20% or less by weight. If the concentration of the polymer solution is less than 5% by weight, the concentration may be excessively diluted, reducing the mechanical strength of the polymer solid electrolyte or causing it to flow off the substrate when applied. If it exceeds 20% by weight, it may be difficult to dissolve the lithium salt in the polymer solution at the desired concentration, the viscosity may be high, reducing solubility, or it may be difficult to apply it in a uniform thin film form.

[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 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.

[0060] Furthermore, the coating method is not particularly limited as long as it is a method that can form a coating film by applying the polymer solution onto the substrate. For example, the coating method may be bar coating, roll coating, spin coating, slit coating, die coating, blade coating, comma coating, slot die coating, lip coating, spray coating, or solution casting.

[0061] The coating film formed on the substrate by this coating method can be formed into a polymer from which the residual solvent has been completely removed by a drying process. To prevent shrinkage of the polymer due to rapid evaporation of the solvent, the drying process can be divided into a primary drying process and a secondary drying process. The primary drying process can remove part of the solvent by drying at room temperature, and the secondary drying process can completely remove the solvent by high-temperature vacuum drying. The high-temperature drying may be carried out at a temperature of 80°C to 130°C. If the high-temperature drying temperature is below 80°C, the residual solvent may not be completely removed, and if it exceeds 130°C, the polymer may shrink, making it difficult to form a uniform electrolyte film.

[0062] In one embodiment of the invention, there may be two or more types of crosslinking functional groups. The crosslinking functional groups may be the same as or different from each other, and preferably different. If the crosslinking functional groups are different, the PEO copolymer may contain multiple types of repeating units, each containing one of these functional groups. Furthermore, if multiple types of crosslinking functional groups are included, it may become easier to control the mobility and ionic conductivity of the polymer chain.

[0063] The aforementioned crosslinkable functional group refers to a functional group that can form crosslinks between itself and / or with other functional groups via a crosslinking agent, and can be attached to the main chain of a polymer chain in the form of a side chain.

[0064] Specifically, the crosslinkable functional group may be directly bonded to the main chain of the PEO copolymer, but it can also be bonded via an alkylene or alkylene oxide linker. For this reason, the crosslinkable 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 shows a single bond), and may be one or more selected from the group consisting of hydroxyl group, carboxyl group, isocyanate group, nitro group, cyano group, amine group, amide group, epoxy group, and allyl group.

[0065] In a more specific embodiment, the PEO copolymer containing the crosslinkable functional group 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 is represented, where k is 0 to 20, and R3 represents an alkyl group with 1 to 5 carbon atoms. R2 represents a substituent in which one or more crosslinking functional groups selected from the group consisting of hydroxyl groups, carboxyl groups, isocyanate groups, nitro groups, cyano groups, amine groups, amide groups, epoxy groups, and allyl groups are bonded to the polymer chain via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (where the alkylene linker having 0 carbon atoms shows a single bond). l, m, and n are the number of repetitions in the repeating unit, where l and n are independent integers between 1 and 1000, and m is an integer between 0 and 1000.

[0070] For example, the crosslinking functional group of R2 can form a polymer having a matrix form of a three-dimensional network structure formed by the crosslinking. The formation of the three-dimensional network structure by the crosslinking can improve the mechanical properties of the polymer solid electrolyte, and a polymer solid electrolyte with improved ionic conductivity can be provided by containing or bonding the gaseous polar compound within such a three-dimensional network structure.

[0071] Furthermore, it is obvious that the PEO copolymer may also contain two or more repeating units of chemical formula 3 in which R2 is a different crosslinking functional group, and may also contain one or more repeating units of chemical formula 2.

[0072] If l, m, and n are each less than 1, forming a polymer is difficult due to the small molecular weight. If l, m, and n are each greater than 1000, the viscosity increases, reducing solubility during the production of polymer solutions and potentially making molding for the production of polymer solid electrolytes difficult. In particular, if the number of repeating units of chemical formula 3 containing crosslinking functional groups exceeds 1000 among l, m, and n, the degree of crosslinking may increase excessively, reducing the mobility of the polymer chains and decreasing the ionic conductivity of the polymer solid electrolyte.

[0073] In this specification, "hydroxyl group" refers to the -OH group.

[0074] In this specification, "carboxyl group" refers to a -COOH group.

[0075] In this specification, "isocyanate group" refers to a -N=C=O group.

[0076] In this specification, "nitro group" refers to the -NO2 group.

[0077] In this specification, "cyano group" refers to a -CN group.

[0078] In this specification, "amide group" refers to -C(=O)NR'R'', where R' and R'' are independently hydrogen or C1-C5 alkyl groups, or R' and R'' can form a heterocycle having C4-C8 atoms in the ring structure together with the N atom to which they are attached.

[0079] In this specification, "amine group" may be selected from the group consisting of monoalkylamine group; monoarylamine group; monoheteroarylamine group; dialkylamine group; diarylamine group; diheteroarylamine group; alkylarylamine group; alkylheteroarylamine group; and arylheteroarylamine group, and the number of carbon atoms is not particularly limited, but is preferably 1 to 30. Specific examples of the amine group include, but are not limited to, methylamine group, dimethylamine group, ethylamine group, diethylamine group, phenylamine group, naphthylamine group, biphenylamine group, dibiphenylamine group, anthracenylamine group, 9-methyl-anthracenylamine group, diphenylamine group, phenylnaphthylamine group, ditolylamine group, phenyltolylamine group, triphenylamine group, biphenylnaphthylamine group, phenylbiphenylamine group, biphenylfluorenylamine group, phenyltriphenylenylamine group, and biphenyltriphenylenylamine group. Furthermore, "amino group" refers to -NH2.

[0080] In this specification, "allyl group" refers to the -CH2-CH=CH2 group.

[0081] The weight-average molecular weight (Mw) of the copolymer containing chemical formulas 1 to 3 may be between 100,000 g / mol and 2,000,000 g / mol, and more specifically, it may be 100,000 g / mol or more, 200,000 g / mol or more, or 300,000 g / mol or more, and may be 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 polymer solid electrolyte produced may not be met. If the weight-average molecular weight (Mw) of the copolymer exceeds 2,000,000 g / mol, the solubility decreases during the production of the polymer solution due to increased viscosity, which may make molding for the production of polymer solid electrolytes difficult. Furthermore, 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, if the number of repeating units of chemical formula 3 containing crosslinking functional groups among l, m, and n exceeds 1000, the degree of crosslinking may increase excessively, reducing the mobility of the polymer chain and decreasing the ionic conductivity of the polymer solid electrolyte.

[0083] Furthermore, the copolymer may be a random copolymer or a block copolymer.

[0084] In one embodiment of the invention, the polymer solid electrolyte may include crosslinking bonds between crosslinkable functional groups. Furthermore, the polymer solid electrolyte may further include a crosslinking agent, thereby further including crosslinking bonds between the crosslinking agent and the crosslinkable functional groups. For example, at least some of the crosslinkable functional groups may form crosslinking bonds with each other via the crosslinking agent to form the three-dimensional network structure described above.

[0085] The crosslinking between the aforementioned crosslinkable functional groups may be urethane bonds, ester bonds, hydrogen bonds, or bonds formed by radical polymerization reactions involving vinyl groups at the allyl group (-CH2-CH=CH2) termini, but are not limited to these examples.

[0086] Furthermore, when a crosslinking agent is added in the manufacturing process of the polymer solid electrolyte, a crosslink bond may be formed between the crosslinking agent and the crosslinkable functional group, and the crosslink bond may be formed by hydrogen bonding, Lewis acid-base interaction bonding, ionic bonding, coordination bonding, or radical polymerization.

[0087] The crosslinking agent is not particularly limited as long as it is a crosslinking agent capable of forming crosslink bonds with the crosslinkable functional group. For example, the crosslinking agent is trimethylolpropane trimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, ethylene glycol dimethyl acrylate (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(acrylamide)benzoic acid (3,5-bis(acrylamido)benzoic acid, 3-aminopropyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-methylacryloxypropyltrimethoxysilane, bis-(1-(tert-butylperoxy)-1-methylethyl)-benzene, dicumyl peroxide, dimethacrylate, divinylbenzene, ethylene glycol maleic rosinate acrylate N,O-bisacryloylphenylalaninol, N,O-bismethacryloylethanolamineOne or more polyfunctional crosslinking agents selected from the group consisting of O-bismethacryloyl ethanolamine, pentaerythritol triacrylate, phenyltrimethoxysilane, tetramethoxysilane, tetramethylene, tetraethoxysilane, and triallyl isocyanurate, for example, a polyvalent compound with two or more functions.

[0088] Furthermore, the crosslinking agent may be present in an amount of 1 to 30 parts by weight per 100 parts by weight of the PEO copolymer containing the crosslinking functional group. If the amount of the crosslinking agent is less than 1 part by weight, sufficient crosslinking with the crosslinking functional group may not occur, and if it exceeds 30 parts by weight, excessive crosslinking may occur, which may actually decrease the mobility of the polymer chain and thus lower the ionic conductivity.

[0089] In one embodiment of the invention, the initiator induces a radical polymerization reaction between the crosslinkable functional groups to form crosslinks between the crosslinkable functional groups. The functional group that enables the radical polymerization reaction may be a functional group containing vinyl at its terminal end, or it may be, for example, an allyl group.

[0090] The initiator is not particularly limited as long as it is an initiator capable of inducing a radical polymerization reaction between the crosslinking 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-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 the crosslinking functional group. When used within this range, it is possible to induce radical polymerization reactions between the crosslinking functional groups and efficiently form crosslinks.

[0092] In one embodiment of the invention, the lithium salt is contained in a dissociated ionic state within the internal space between the polymer chains, thereby improving the ionic conductivity of the polymer solid electrolyte. At least some of the cations and / or anions dissociated from the lithium salt remain bound to the polymer chains and can exhibit mobility during charging and discharging of the battery.

[0093] The lithium salts mentioned above are (CF3SO2)2NLi (Lithium bis(trifluoromethanesulfonyyl)imide, LiTFSI), (FSO2)2NLi (Lithium bis(fluorosulfonyl)imide, LiFSI), LiNO3, LiOH, LiCl, LiBr, LiI, LiClO4, LiBF4, and LiB 10 Cl 10It may contain one or more selected from the group consisting of LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiSCN, LiC(CF3SO2)3, lithium chloroborane, lithium lower aliphatic carboxylate, and lithium tetraphenylborate.

[0094] Furthermore, the lithium salt may be present in 25 to 45 parts by weight per 100 parts by weight of the PEO copolymer containing the crosslinking functional group, and more specifically, it may be present in 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 lithium salt content 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] On the other hand, in the manufacturing method of the embodiment described above, the ceramic compound has lithium ion transfer capability to improve lithium ion conductivity, preferably contains lithium atoms and does not store lithium, but has the function of moving lithium ions, thereby improving the ionic conductivity of the polymer solid electrolyte in the form of a composite solid electrolyte.

[0096] Furthermore, the ceramic compound may be included in a state where it is uniformly dispersed within the internal space of the crosslinked polymer chain, for example, within the three-dimensional network structure. The ceramic compound can be added together in the crosslinking process and dispersed uniformly without clumping within the internal space of the polymer chain formed by the crosslinking. Such a ceramic compound may be advantageous in improving the mechanical strength and ionic conductivity of the polymer solid electrolyte due to its uniform dispersion form.

[0097] Also, the ceramic compound may be in particle form. Due to the morphological feature of particles, it may be contained in a more uniformly dispersed state within the polymer solid electrolyte. The particles of the ceramic compound 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 the reduction of polymer crystallinity is slight. If it exceeds 1000 nm, the dispersibility may decrease due to increased aggregation between particles, and it may be difficult to disperse uniformly.

[0098] The ceramic compound may be an oxide-based or phosphate-based compound. For example, it may become an oxide-based solid electrolyte in the form of a lithium metal oxide or a lithium metal phosphate. More specifically, the ceramic compound is a garnet (Garnet)-type lithium-lanthanum-zirconium oxide-based (LLZO, Li7La3Zr2O 12 ) compound, a perovskite (perovskite)-type lithium-lanthanum-titanium oxide-based (LLTO, Li3xLa 2 / 3-x TiO3) compound, a phosphate (phosphate)-based NASICON (NASICON)-type lithium-aluminum-titanium phosphate-based (LATP, Li 1+x Al x Ti 2-x (PO4)3) compound, a lithium-aluminum-germanium phosphate-based (LAGP, Li 1.5 Al 0.5 Ge 1.5One or more compounds may be selected from the group consisting of (PO4)3) compounds, lithium-silicon-titanium phosphate (LSTP, LiSiO2TiO2(PO4)3) 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 aforementioned oxide-based or phosphate-based oxide-based solid electrolytes generally have a maximum temperature of 10°C at room temperature. -4 ~10 -3 It has an ionic conductivity value of S / cm, is stable in the high-voltage range, and has the advantages of being stable in air, easy to synthesize, and easy to handle.

[0100] Furthermore, the ceramic compound does not easily burn or ignite even under high-temperature conditions of 400°C or higher, thus exhibiting high high-temperature stability. Therefore, when the polymer solid electrolyte contains the ceramic compound, it is possible to improve not only the mechanical strength of the solid electrolyte but also its high-temperature stability and ionic conductivity.

[0101] The ceramic compound may be present in an amount of 10 to 100 parts by weight, or 10 to 60 parts by weight, per 100 parts by weight of the PEO copolymer containing the crosslinking functional group.

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

[0103] If the ceramic compound is present in an excessively large amount, the ceramic compound will not be uniformly dispersed within the polymer, and the ceramic compound particles will aggregate and clump together, resulting in the production of a solid electrolyte with reduced ionic conductivity.

[0104] On the other hand, in step (S2), a polar solvent can be vapor-deposited onto the polymer produced in step (S1) to produce a polymer solid electrolyte in which polar solvent gas molecules are bonded to the polymer chain, or in which a gaseous polar compound is contained within the internal space of the polymer chain, for example, within a three-dimensional network structure. In this case, the gaseous molecules of the polar solvent can correspond to the polar compound.

[0105] At this time, the vapor deposition step can be advanced for a time that satisfies the following equation 1 to adjust the content of the polar solvent (or polar compound in gaseous state) in the polymer solid electrolyte:

[0106]

number

[0107] In formula 1 above, M(t) is the content of the polar compound contained on the surface or inside the polymer chain after the polar solvent has been 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, a fitting parameter for fitting the content of polar compounds (M(t)), where 0.5 ≤ n < 0.7.

[0108] The aforementioned M(t) represents the content of the polar compound in a gaseous state contained on or inside the polymer chain after the polar solvent has been vapor-deposited and diffused, depending on the vapor deposition time. The content of the polar compound increases in proportion to the vapor deposition time (t) in the initial stages of vapor deposition, but after a certain vapor deposition time (t) has elapsed, the rate of increase decreases and tends to converge to a specific value. Since the adsorption and desorption behavior of the polar solvent is similar inside the polymer, the aforementioned M(t) can be measured using a desorption amount measuring device. For example, the aforementioned M(t) can be obtained by measuring the amount of desorption of the polar solvent over time while simultaneously heating at 60°C using an MS-70 analyzer (AND, Japan). Preferably, the content of the polar compound may be 0.1% by weight or more and less than 10% by weight. For example, the content of the polar compound may be 0.1% by weight or more, 1% by weight or more, 2% by weight or more, or 5% by weight or less, 6% by weight or less, 7% by weight or less, 8% by weight or less, 9% by weight or less, or less than 10% by weight. When the content of the polar compound is less than 0.1% by weight, it is difficult to induce a change in the chain configuration (chaincon formation) within the polymer, and the ionic conductivity of the polymer solid electrolyte does not improve. When the content of the polar compound is 10% by weight or more, the polymer solid electrolyte has a high liquid content, exhibiting the properties of a semi-solid battery, and there is a problem that the mechanical strength of the polymer solid electrolyte decreases due to the gelation of the polymer.

[0109] The aforementioned t represents the vapor deposition time. It may also represent the time elapsed from the start of vapor deposition. The method or apparatus for measuring the vapor deposition time is not particularly limited. For example, the vapor deposition time can be measured using various means that can confirm the time at a specific point in time.

[0110] The aforementioned K is an empirical rate coefficient and corresponds to a fitting parameter for fitting the content of the polar compound (M(t)) using Equation 1. The aforementioned K is directly related to the content of the polar compound (M(t)) adsorbed when the polar solvent is vapor-deposited onto the polymer, and 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 value of n is a transport exponent, which corresponds to a fitting parameter for fitting the content of the polar compound (M(t)) using Equation 1. The value of 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 n falls within this range, Fickian diffusion behavior can be observed.

[0112] The vapor deposition described above can be carried out by bringing the vapor of the polar solvent, generated by heating the polar solvent at room temperature or by other means, into contact with the polymer and allowing it to penetrate inside. In this way, by leaving it at room temperature or by vapor deposition by heating, the polar compound in a gaseous state may be uniformly diffused onto the surface and / or inside the polymer, and the polar compound gas molecules may be bonded to the polymer chain or uniformly dispersed or diffused within the internal space of the polymer chain.

[0113] When a polar solvent is left at room temperature during vapor deposition, a small amount of polar solvent with a low boiling point can be gradually vaporized at room temperature and allowed to penetrate into the polymer, effectively inducing a change in the conformation of the cross-linked polymer chains within the polymer.

[0114] Furthermore, when heating the polar solvent during vapor deposition, the vapor deposition rate can be improved. In this case, the heating temperature is not particularly limited as long as it is a temperature at which the polar solvent can undergo a phase change into vapor, and may be, for example, 30°C to 80°C. General PEO melts at 60°C, but PEO copolymers modified with the crosslinking functional group have improved heat resistance and can withstand up to 80°C when forming a crosslinked structure, so the vapor deposition rate can be further increased. Also, the heating method is not limited as long as it can supply the energy to generate vapor. For example, direct heating methods such as burners or furnaces, or indirect heating methods such as heaters or steam tubes can be used, but the method is not limited to these examples.

[0115] When heating, if the temperature is excessively high, the solvent may boil above its boiling point, structural changes may occur in the solvent, or deformation of the polymer may be induced. This has the disadvantage of making it difficult to control the evaporation rate of the polar solvent during vapor deposition. Therefore, in order to perform vapor deposition with 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 described above, polymer solid electrolytes can be produced by vapor deposition, which can either bond to the crosslinked polymer chains or contain polar solvent molecules, or polar compounds, within the internal space between polymer chains.

[0117] According to the above-described method for producing a polymer solid electrolyte, the degree of improvement in the 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 determined by formula 1 and the polar compound in the gaseous state contained in the polymer solid electrolyte.

[0118] Polymer solid electrolyte The polymeric solid electrolyte produced by the embodiments described above comprises a polymer including a PEO (polyethylene oxide) copolymer containing crosslinkable functional groups, and a polar compound, wherein at least a portion of the crosslinkable functional groups of the copolymer form crosslink bonds with each other, so that the polymer forms a three-dimensional network structure, and the polar compound may be contained within the three-dimensional network structure in a gaseous state or have a structure bonded to the polymer chain.

[0119] Furthermore, in the polymer solid electrolyte, at least a portion of the crosslinkable functional groups can form crosslink bonds with each other via a crosslinking agent, and the polymer solid electrolyte may further contain a lithium salt.

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

[0121] On the other hand, the types and contents of each component of the polymer solid electrolyte have already been described above, so no further explanation regarding this will be provided.

[0122] In the solid electrolyte described above, the gaseous polar compound may be dispersed between polymer chains forming the three-dimensional network structure, or it may be adsorbed or bound to the surface or interior of the polymer chains. Such a polar compound is a gaseous molecule of a polar solvent used in the vapor deposition process, and after the gaseous molecule of the polar solvent is adsorbed onto the polymer during vapor deposition, it can diffuse into the interior of the polymer chains. As a result, a solid electrolyte with the above structure can be produced. By including the polar compound in a form that is bound to the polymer chains or dispersed in the internal space between polymer chains, the ionic conductivity of the final produced polymer solid electrolyte can be improved.

[0123] Such polymer solid electrolytes contain substantially no liquid solvent or electrolyte, but include trace amounts of polar compounds contained or bonded in a gaseous state by vapor deposition. Such polymer solid electrolytes can be identified, for example, by observing the electrolyte layer containing them with the naked eye or an electron microscope after separation from an all-solid-state battery; no liquid components are observed on the surface of the electrolyte layer. In contrast, when a liquid polar solvent or electrolyte is injected into a solid electrolyte, liquid components or wettable components can be observed on the surface of the electrolyte layer. Furthermore, polymer solid electrolytes containing the polar compound in a gaseous state through vapor deposition exhibit significantly higher ionic conductivity compared to those in which a liquid polar solvent or electrolyte is injected. Such comparisons of ionic conductivity can also confirm the presence of the polar compound in a gaseous state through vapor deposition.

[0124] Specifically, polar compounds that are bound to the polymer chains or contained in the internal spaces between the polymer chains act as plasticizers, causing the polymer to plasticize. The plasticized polymer has an increased amount of amorphous regions inside, which improves the mobility of the polymer chains. This improved mobility increases the ion hopping effect within the polymer, thereby improving the ionic conductivity of the polymer solid electrolyte.

[0125] Furthermore, the polar compound can act as an intermediate for smooth ion transfer through ion hopping. Since the affinity between lithium ions and the polar compound is stronger than the affinity between lithium ions and the ether oxygen of the PEO copolymer, lithium ions can be transferred more quickly and easily within the polymer on which the polar compound is adsorbed. In other words, the influx of the polar compound into the polymer increases the cation solvation effect of lithium ions, improving ion mobility and thereby improving the ionic conductivity of the polymer solid electrolyte.

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

[0127] Specifically, the polar compound may include one or more 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% by weight or more and less than 10% by weight on a total weight basis of the solid electrolyte. For example, the content of the polar compound may be 0.1% by weight or more, 1% by weight or more, 2% by weight or more, or 5% by weight or less, 6% by weight or less, 7% by weight or less, 8% by weight or less, 9% by weight or less, or less than 10% by weight. If the content of the polar compound is less than 0.1% by weight, it is difficult to induce a change in the chain conformation of the polymer, and the ionic conductivity of the polymer solid electrolyte does not improve. If the content of the polar compound is 10% by weight or more, the polymer solid electrolyte has a high liquid content, exhibiting the properties of a semi-solid battery, and there is a problem that the mechanical strength of the polymer solid electrolyte decreases due to the gelation of the polymer.

[0129] All solid state battery An additional embodiment of the invention also relates to an all-solid-state battery comprising a solid electrolyte, the all-solid-state battery comprising a negative electrode, a positive electrode, and a solid electrolyte interposed between the negative electrode and the positive electrode, the solid electrolyte being manufactured according to the embodiment described above.

[0130] Specifically, the solid electrolyte contains a polymer formed by crosslinking a PEO (polyethylene oxide) copolymer containing crosslinkable functional groups, and a polar compound in a gaseous state. The polar compound in a gaseous state is contained or bonded to the solid electrolyte, and the ceramic compound is selectively and uniformly dispersed, improving ionic conductivity. Therefore, it is suitable as an electrolyte for an all-solid-state battery.

[0131] On the other hand, 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 the positive electrode current collector.

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

[0133] Furthermore, the positive electrode active material is not particularly limited as long as it is a material capable of reversibly intercalating and releasing lithium ions, for example, lithium cobalt oxide, lithium nickel oxide, Li[NixCoyMnzMv]O2 (wherein M is one or more elements selected from the group consisting of Al, Ga, and In; 0.3≦x<1.0, 0≦y, z≦0.5, 0≦v≦0.1, x+y+z+v=1), Li(LiaMb-a-b'M'b')O2 2-c A c Layered compounds such as (wherein 0≦a≦0.2, 0.6≦b≦1, 0≦b'≦0.2, and 0≦c≦0.2; M comprises Mn and one or more selected from the group consisting of Ni, Co, Fe, Cr, V, Cu, Zn, and Ti; M' is one or more selected from the group consisting of Al, Mg, and B, and A is one or more selected from the group consisting of P, F, S, and N) or compounds substituted with one or more transition metals; chemical formula Li 1+y Mn 2-y Lithium manganese oxides such as O4 (where y is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-yNi-site type lithium nickel oxide represented as 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 Lithium manganese composite oxides represented as O2 (where M = Co, Ni, Fe, Cr, Zn, or Ta, and y = 0.01 to 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 alkaline earth metal ions; disulfide compounds; Fe2(MoO4)3, etc., are examples, but are not limited to these.

[0134] Furthermore, the positive electrode active material may be present in an amount of 40 to 80% by weight based on the total weight of the positive electrode active material layer. Specifically, the content of the positive electrode active material may be 40% or more by weight, 50% or more by weight, or 70% or less by weight, or 80% or less by weight. If the content of the positive electrode active material is less than 40% by weight, the connectivity and electrical properties between the positive electrode active materials may be insufficient, and if it exceeds 80% by weight, the mass transfer resistance may increase.

[0135] Furthermore, the binder is a component that assists in the bonding of the positive electrode active material to conductive materials and to the current collector, and includes styrene-butadiene rubber, acrylic styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile-butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile The binder may include one or more selected from the group consisting of tolyl, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethylcellulose, hydroxypropylcellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethylsucrose, 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 one or more selected from the group consisting of styrene-butadiene rubber, polytetrafluoroethylene, carboxymethylcellulose, polyacrylic acid, lithium polyacrylate, and polyvinylidene fluoride.

[0136] Furthermore, the binder may be present in an amount of 1% to 30% by weight based on the total weight of the positive electrode active material layer. Specifically, the binder content may be 1% or more by weight, 3% or more by weight, 15% or less by weight, or 30% or less by weight. If the binder content is less than 1% by weight, the adhesive strength between the positive electrode active material and the positive electrode current collector may decrease. If it exceeds 30% by weight, the adhesive strength will improve, but the amount of positive electrode active material will decrease accordingly, which may reduce the 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 and has excellent electrical conductivity without inducing chemical changes in the battery. Typically, graphite or conductive carbon can be used, for example, graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, Denka black, thermal black, channel black, furnace black, and lamp black; carbon-based materials whose crystalline structure is graphene or graphite; conductive fibers such as carbon fibers and metal fibers; carbon fluoride; metal powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives; which can be used alone or in mixtures of two or more, but are not necessarily limited to these.

[0138] The conductive material may typically be present in an amount of 0.5% to 30% by weight based on the total weight of the positive electrode active material layer. Specifically, the content of the conductive material may be 0.5% or more by weight, 1% or more by weight, 20% or less by weight, or 30% or less by weight. If the content of the conductive material is excessively low, less than 0.5% by weight, it may be difficult to expect an improvement in electrical conductivity, or the electrochemical properties of the battery may deteriorate. If it is excessively high, exceeding 30% by weight, the amount of positive electrode active material may be relatively reduced, leading to a decrease in capacity and energy density. The method for incorporating the conductive material into the positive electrode is not significantly limited, and conventional methods known in the art, such as coating the positive electrode active material, can be used.

[0139] Furthermore, the positive electrode current collector supports the positive electrode active material layer and plays a role in transferring electrons between the external conductor and the positive electrode active material layer.

[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. For example, copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, silver, etc., and aluminum-cadmium alloys can be used as the positive electrode current collector.

[0141] The positive electrode current collector may have a fine uneven surface or a three-dimensional porous structure to enhance the bonding force with the positive electrode active material layer. This allows the positive electrode current collector to take on a variety of forms, such as film, sheet, foil, mesh, net, porous material, foam, or nonwoven fabric.

[0142] Such positive electrodes can be manufactured by conventional methods. Specifically, a composition for forming a positive electrode active material layer, prepared by mixing a positive electrode active material, a conductive material, and a binder in an organic solvent, is applied to a positive electrode current collector and dried, and then selectively compressed and 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 evaporates easily. Specifically, examples include acetonitrile, methanol, ethanol, tetrahydrofuran, water, isopropyl alcohol, dimethyl sulfoxide (DMSO), and methylpyrrolidone (NMP, N-Methyl-2-Pyrrolidone).

[0143] On the other hand, 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 the negative electrode current collector.

[0144] The negative electrode active material may include a material into which lithium (Li+) can be reversibly intercalated or deintercalated, a material that can react with lithium ions to reversibly form a lithium-containing compound, a lithium metal, or a lithium alloy.

[0145] The material in which lithium ions (Li+) can be reversibly inserted into or removed from may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. The material in which lithium ions (Li+) can be reversibly reacted to 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) with 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, and more specifically, it may be in the form of a lithium metal thin film or lithium metal powder.

[0147] The negative electrode active material may be present in an amount of 40 to 80% by weight based on the total weight of the negative electrode active material layer. Specifically, the content of the negative electrode active material may be 40% or more by weight, 50% or more by weight, or 70% or less by weight, or 80% or less by weight. If the content of the negative electrode active material is less than 40% by weight, the electrical properties may not be sufficient, and if it exceeds 80% by weight, the mass transfer resistance may increase.

[0148] Furthermore, the binder in the positive electrode active material layer is as described above.

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

[0150] Furthermore, the negative electrode current collector is not particularly limited as long as it is conductive without inducing a chemical change in the battery. For example, the negative electrode current collector can be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloy. In addition, the negative electrode current collector can be made of various forms such as films, sheets, foils, nets, porous materials, foams, and nonwoven fabrics with fine irregularities formed on their surface, similar to the positive electrode current collector.

[0151] The method for manufacturing the negative electrode is not particularly limited, and it can be manufactured by forming a negative electrode active material layer on a negative electrode current collector using methods for forming layers or films commonly used in the industry. For example, methods such as crimping, coating, or vapor deposition may be used. Furthermore, the negative electrode of the present invention is also included in the case where a metallic lithium thin film is formed on a metal plate by initial filling after the battery is assembled without a lithium thin film on the negative electrode current collector.

[0152] On the other hand, according to an additional embodiment of the invention, a battery module including the all-solid-state battery as a unit battery, a battery pack including the battery module, and a device including the battery pack as a power source are provided.

[0153] Specific examples of the aforementioned devices include, but are not limited to, power tools powered by battery-powered motors; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters; electric golf carts; and power storage systems.

[0154] The following examples are provided to facilitate understanding of the invention, but these examples are provided only to make the invention easier to understand, and the invention is not limited thereto.

[0155] In the following examples and comparative examples, when producing the polymer solid electrolyte and the composite solid electrolyte, Example 1 and Comparative Example 1 were carried out using the "solvent vapor deposition method," which involves vapor deposition of a polar solvent, while Example 2 and Comparative Example 2 were carried out using the "solvent impregnation method," which involves impregnation with a polar solvent.

[0156] Furthermore, while all solid electrolytes produced in the following examples and comparative examples belong to the category of polymer solid electrolytes, Example 2 and Comparative Example 2 are the same as Example 1 and Comparative Example 1, but with the addition of a ceramic compound. For the purpose of distinguishing between them, the terms "polymer solid electrolyte" and "composite solid electrolyte" were used, respectively.

[0157] Examples Example 1: Production of polymer solid electrolytes Step 1) Production of polymers including copolymers A polyethylene oxide (PEO) copolymer of the following chemical formula 1a was prepared:

[0158] [ka]

[0159] In the above chemical formula 1a, R1 is -CH2-O-(CH2-CH2-O) k The copolymer is -CH3, R2 is -CH2-O-CH2-CH=CH2, k is 2, the l:m:n ratio is 85:13:2, and the weight-average molecular weight (Mw) of the copolymer is approximately 2,000,000 g / mol.

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

[0161] A polymer solution was prepared by mixing the polyethylene oxide copolymer with acetonitrile as the solvent, trimethylolpropane trimethacrylate as a crosslinking agent, benzoyl peroxide as an initiator, and LiTFSI as a lithium salt. This solution was then stirred for 24 hours using a magnetic bar. At this time, the composition of the polymer solution was such that 100 parts by weight of the polyethylene oxide copolymer was mixed with 20 parts by weight of the crosslinking agent trimethylolpropane trimethacrylate, 1 part by weight of the initiator benzoyl peroxide, and 36.5 parts by weight of the lithium salt, and acetonitrile solvent was used so that the concentration of the polyethylene oxide copolymer contained in the polymer solution was 10.4%.

[0162] After casting the manufactured polymer solution onto the lower substrate of a coin cell, a 200 μm thick electrolyte film was produced by primary drying at room temperature for 12 hours, followed by secondary drying at 100°C for 12 hours to induce cross-linking.

[0163] (2-step) Production of polymer solid electrolytes The polymer was attached to the upper plate of the chamber, and the lower part of the chamber was filled with ethyl methyl carbonate (EMC) solvent. After this, the chamber was allowed to evaporate naturally at room temperature for 72 hours, and ethyl methyl carbonate (EMC) vapor was introduced into the polymer attached to the upper part of the chamber to deposit onto the polymer, thereby producing a polymer solid electrolyte.

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

[0165] Comparative Example Comparative Example 1: Polymeric solid electrolyte containing a large amount of modified PEO+ liquid The polymer solid electrolyte was manufactured in the same manner as in Example 1, except that the EMC solvent was directly injected into the polymer solid electrolyte manufactured in step 1) of Example 1.

[0166] Comparative Example 2: Composite solid electrolyte containing a large amount of modified PEO+ liquid The composite solid electrolyte was manufactured in the same manner as in Example 2, except that the EMC solvent was directly injected into the composite solid electrolyte manufactured 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. Using Equation 1 below, the content of polar compounds (M(t)) measured by the fitting parameters K and n was fitted to confirm the correlation between the diffusion behavior of polar solvents and their ionic conductivity:

[0168]

number

[0169] In formula 1 above, M(t) is the content of the polar compound contained on the surface or inside the polymer chain after the polar solvent has been 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, a fitting parameter for fitting the content of polar compounds (M(t)), where 0.5 ≤ n < 0.7.

[0170] In the above formula 1, the content of the polar compound (M(t)) can be measured by monitoring the weight of the liquid phase that evaporates over time while heating a solid electrolyte test specimen using a balance. For example, it can be measured by using a heated electronic balance (AND's MS-70) to heat the test specimen at a temperature of 55-70°C or 60°C while monitoring the weight of the liquid phase that evaporates over time. When the amount of polar compound that evaporates over time reaches a saturation point, that saturation point is considered to be the total amount of polar compound contained inside the solid electrolyte. In the examples and comparative examples, the polar compound may be ethyl methyl carbonate (EMC).

[0171] Using Equation 1 above, a graph was created showing the correlation between the change in the measured polar compound content (M(t)) and the change in (ΔM(t)) for a vapor deposition time (t) between 0 seconds and 500 seconds (Figures 1 and 2). From this, K and n, which are fitting parameters indicating the behavior of the polar solvent, were determined.

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

[0173] Referring to Figures 1 and 2, both Example 1 and Comparative Example 1 correspond to the graph of the function in Equation 1. In Example 1, the diffusion behavior of the polar solvent vapor-deposited onto the polymer is similar to Fickian diffusion, while in Comparative Example 1, the diffusion behavior of the polar solvent impregnated into the polymer is similar to non-Fickian diffusion, and it can be predicted that gelation will occur.

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

[0175] Furthermore, 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, 1.7671 cm⁻¹ was used. 2 After forming the polymer solid electrolyte on the lower substrate of a coin cell of a certain size, a coin cell for ionic conductivity measurement was manufactured using SUS as an inert electrode (blocking electrode).

[0177] Using an electrochemical impedance spectrometer (EIS, VM3, Bio Logic Science Instrument), the resistance was measured at 25°C under conditions of an amplitude of 10mV and a scan range from 1Hz to 0.1MHz. The ionic conductivity of the polymer solid electrolyte was then calculated using Equation 2 below.

[0178]

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[0179] In equation 2 above,

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[0180] [Table 1]

[0181] As shown in Table 1 above, when comparing Example 1, which is a polymer solid electrolyte, with Comparative Example 1, the vapor deposition process was performed in Example 1 compared to Comparative Example 1, which was performed using a solvent impregnation method.

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Claims

1. (S1) A step of producing a polymer by crosslinking PEO (polyethylene oxide) copolymers containing crosslinkable functional groups; and (S2) A step of vapor deposition of a polar solvent onto the polymer produced in step (S1); A method for producing a polymer solid electrolyte, wherein the vapor deposition step is carried out for a time that satisfies the following formula 1 to adjust the content of polar compounds in the polymer solid electrolyte: [Math 1] In the above formula 1, M(t) is the content of the polar compound contained on the surface or inside the polymer chain after the polar solvent has been 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)), where 0.01 < K < 0.

1. n is the transport exponent, a fitting parameter for fitting the content of polar compounds (M(t)), where 0.5 ≤ n < 0.

7.

2. The method for producing a polymer solid electrolyte according to claim 1, wherein step (S1) is carried out in the presence of one or more additional substances selected from the group consisting of crosslinking agents and initiators.

3. The method for producing a polymer solid electrolyte according to claim 1, further comprising adding a lithium salt in or before step (S1).

4. A method for producing a polymer solid electrolyte according to claim 1, wherein a ceramic compound is further added during the crosslinking process in step (S1).

5. The crosslinkable functional group is bonded to the PEO copolymer via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (wherein the alkylene linker having 0 carbon atoms shows a single bond). A method for producing a polymer solid electrolyte according to claim 1, comprising a group selected from the group consisting of hydroxyl group, carboxyl group, isocyanate group, nitro group, cyano group, amine group, amide group, epoxy group, and allyl group.

6. The method for producing a polymeric 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: 【Chemistry 1】 【Chemistry 2】 【Transformation 3】 In the above chemical formulas 1 to 3, R １ is, -CH ２ -O-(CH ２ -CH ２ -O) ｋ -R ３ This shows that k is between 0 and 20, and R ３ This represents an alkyl group having 1 to 5 carbon atoms. R ２ This refers to a substituent in which one or more crosslinking functional groups selected from the group consisting of hydroxyl groups, carboxyl groups, isocyanate groups, nitro groups, cyano groups, amine groups, amide groups, epoxy groups, and allyl groups are bonded to the polymer chain via a C0-C10 alkylene linker or alkylene oxide linker (where the C0 alkylene linker shows a single bond). l, m, and n are the number of repetitions in the repeating unit, where l and n are independent integers between 1 and 1000, and m is an integer between 0 and 1000.

7. The method for producing a polymer solid electrolyte according to claim 1, wherein in step (S2), vapor of the polar solvent is deposited onto the polymer such that the content of the polar solvent is 0.1% by weight or more and less than 10% by weight on a total weight basis of the polymer solid electrolyte.

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

9. A method for producing a polymer solid electrolyte according to any one of claims 1 to 8, wherein the polar solvent comprises one or more 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. The method for producing a polymer solid electrolyte according to claim 9, wherein the polar solvent comprises one or more selected from the group consisting of ethyl methyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, vinylene carbonate, and sulfolane.

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