Composite solid electrolyte and method for producing the same

Abstract

The present invention relates to a composite solid electrolyte and a method for producing the same, which comprises a polymer including a PEO (polyethylene oxide) copolymer containing cross-linkable functional groups, a ceramic compound, and a polar compound, wherein at least a portion of the cross-linkable functional groups form cross-links with each other, the polymer forming a three-dimensional network structure, and the polar compound in a gaseous state is contained within the three-dimensional network structure or is bonded to the polymer chain.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0132765, filed October 14, 2022, and Korean Patent Application No. 10-2023-0136066, 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 composite solid electrolyte and a method for producing the same. [Background technology]

[0003] Lithium-ion batteries using liquid electrolytes have a structure in which the negative electrode and positive electrode are separated by a separator, and if the separator is damaged due to 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 in the field of lithium-ion secondary batteries is a very important issue.

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

[0005] Among solid electrolytes, polymer solid electrolytes can be made of ion-conductive polymer materials, and can be used in the form of a composite solid electrolyte in which such polymer materials are mixed with inorganic materials.

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

[0007] To overcome these limitations of conventional composite solid electrolytes, efforts have been made to improve the ionic conductivity of the composite solid electrolyte by modifying the structure of the crystalline polymer or by adding a separate plasticizer to the polymer to improve the mobility of the polymer chains. However, it has been difficult to improve the ionic conductivity of the composite solid electrolyte by modifying the polymer structure or adding a plasticizer alone.

[0008] Therefore, there is a need to develop a technology that can improve the ionic conductivity of composite solid electrolytes by methods other than modifying the polymer structure or adding plasticizers. [Prior art documents] [Patent documents]

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

[0010] The present invention provides a composite solid electrolyte that can improve ionic conductivity even when a trace amount of a polar compound (e.g., a polar solvent compound) is added to the composite solid electrolyte in a non-liquid state, and a method for producing the same.

[0011] The present invention also provides an all-solid-state battery that includes the composite solid electrolyte and exhibits improved ionic conductivity. [Means for solving the problem]

[0012] According to one embodiment of the present invention, there is provided a composite solid electrolyte comprising a polymer including a polyethylene oxide (PEO) copolymer containing cross-linkable functional groups, a ceramic compound, and a polar compound, wherein at least a portion of the cross-linkable functional groups form cross-links with each other, the polymer forming a three-dimensional network structure, and the polar compound in a gaseous state is contained within the three-dimensional network structure or bound to the polymer chain.

[0013] In such a composite 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.

[0014] The composite solid electrolyte may further include a cross-linking agent, and in this case, at least some of the cross-linkable functional groups may form cross-links with each other via the cross-linking agent.

[0015] In the composite solid electrolyte, the PEO-based copolymer may include one or more cross-linkable functional groups. The cross-linkable functional groups are bonded to the polymer chain of 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), 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.

[0016] The composite solid electrolyte may further include the lithium salt, and the lithium salt may be present in a state where at least a portion of the lithium salt is dissociated into cations and anions. The cations and / or anions may be present in a state bound to the polymer and may migrate during charge / discharge of the battery.

[0017] In a specific embodiment, the PEO (polyethylene oxide) copolymer of the composite solid electrolyte may be a copolymer including repeating units of the following Chemical Formulas 1 to 3:

[0018] [Chemical formula 1] [ka] [Chemical formula 2] [ka] [Chemical formula 3] [ka]

[0019] In the above 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 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 1000, and m is an integer of 0 to 1000.

[0020] Meanwhile, in the composite solid electrolyte, the content of the polar compound may be 0.1 wt % or more and less than 10 wt % based on the total weight of the composite solid electrolyte.

[0021] The polar compound may include one or more selected from the group consisting of carbonate compounds and sulfonyl compounds, or may be a polar compound contained in a gaseous state derived from a carbonate solvent or a sulfonyl solvent. More 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.

[0022] The ceramic compound may also include an oxide-based solid electrolyte of lithium metal oxide or lithium metal phosphate, and more specifically, may include one or more oxide-based solid electrolytes selected from the group consisting of lithium-lanthanum-zirconium oxide (LLZO) compounds, lithium-silicon titanium phosphate (LSTP) compounds, lithium-lanthanum-titanium oxide (LLTO) compounds, lithium-aluminum-titanium phosphate (LATP) compounds, lithium-aluminum-germanium phosphate (LAGP) compounds, and lithium-lanthanum-zirconium-titanium oxide (LLZTO) compounds.

[0023] Meanwhile, according to another embodiment of the present invention, there is provided a method for manufacturing the composite solid electrolyte of the one embodiment, including: (S1) mixing a PEO (polyethylene oxide)-based copolymer having a cross-linkable functional group with a ceramic compound, and then performing a cross-linking reaction on the PEO-based copolymer contained in the mixture; and (S2) depositing a polar solvent on the mixture including the polymer cross-linked in the (S1) step.

[0024] In this production method, the crosslinking reaction step (S1) may be carried out in the presence of one or more additives selected from the group consisting of a crosslinking agent and an initiator.

[0025] Meanwhile, in the preparation method, the polar solvent may be a polar solvent corresponding to the polar compound of the embodiment.

[0026] In the manufacturing method, in the step (S2), 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 composite solid electrolyte.

[0027] According to another embodiment of the present invention, there is provided an all-solid-state battery including an electrolyte layer including the composite solid electrolyte of the above-described embodiment. [Effects of the Invention]

[0028] The composite solid electrolyte according to an embodiment of the present invention maintains the inherent structural characteristics of the polymer without deformation or destruction of the polymer chains, and improves the ionic conductivity of the composite solid electrolyte by improving the mobility of the polymer chains and uniformly distributing ceramic particles in the composite solid electrolyte.

[0029] Furthermore, the composite solid electrolyte contains a trace amount of a polar compound in a gaseous state, which can improve the ionic conductivity and mechanical properties of the polymer solid electrolyte.

[0030] In addition, when a polar solvent is incorporated into the composite solid electrolyte by vapor deposition, 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 deteriorating mechanical properties. DETAILED DESCRIPTION OF THE INVENTION

[0031] Hereinafter, specific embodiments of the present invention will be described in more detail for better understanding of the present invention.

[0032] 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, based on the principle that the inventor can appropriately define the concept of the term in order to best explain his or her invention.

[0033] As used herein, the term "bonding," i.e., 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" is not limited to a specific type of physical bond, chemical bond, etc., but includes a state in which the polar compound is fixed by various bonds including these physical bonds, chemical bonds, etc., a state in which the polar compound is fixed by simple adhesion such as adsorption, or a state in which the polar compound is included in a three-dimensional network structure formed by cross-linking of the polymer and is fixed adjacent to the polymer chain or cross-linked structure.

[0034] 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 crosslinking functional groups and a crosslinking agent. The three-dimensional network structure may also be referred to as a crosslinked structure.

[0035] As used herein, the expression "existing or being contained in a gaseous state" for a polar compound (polar solvent) in a composite solid electrolyte refers to the polar compound being deposited in a vapor state, as distinct from the liquid-injected electrolyte, immediately after the composite solid electrolyte is manufactured or during the charge / discharge process of an all-solid-state secondary battery containing the composite solid electrolyte. However, depending on the storage or operating conditions of the composite solid electrolyte and / or secondary battery, the deposited polar compound may be locally or temporarily liquefied. Even in such cases, the deposited polar compound exhibits higher mobility than the polar solvent injected in a liquid state and thus exhibits a different state from the liquid polar solvent, and therefore can also be considered to be present or contained in the "gas state."

[0036] Meanwhile, in the past, in order to improve the ionic conductivity of solid electrolytes, composite solid electrolytes have been prepared by dispersing ceramic compounds such as oxides in a polymer matrix. However, such composite solid electrolytes have problems in that the ionic conductivity is reduced when the oxide-based ceramic particles in the polymer matrix are unevenly distributed or when a highly crystalline polymer such as polyethylene oxide is used as the polymer.

[0037] In addition, in the past, to improve the ionic conductivity of solid electrolytes, solid electrolytes have been immersed in or supported by a liquid electrolyte or a liquid solvent, or the liquid electrolyte or solvent has been directly injected 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 only increases the ionic conductivity of the solid electrolyte based on the high ionic conductivity of the liquid itself, and the improvement is insufficient, requiring 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, far from improving the physical properties of the solid electrolyte itself. Furthermore, when a liquid electrolyte or solvent is directly added or injected into a solid electrolyte in a liquid state, there are problems such as undesired side reactions between the polymer and the liquid, which can damage the polymer chains or break bonds within the polymer, resulting in the collapse of the solid electrolyte structure and a decrease in ionic conductivity.

[0038] In addition, when a solvent or liquid electrolyte is directly injected into a solid electrolyte, the liquid 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.

[0039] Furthermore, in the case of the conventional technology disclosed in JP 1994-124713 A, a technique was used in which a solvent was evaporated onto a general PEO (polyethylene oxide) polymer, but this had the problem that the internal structure of the polymer collapsed, making it impossible to ensure ionic conductivity.

[0040] Therefore, the inventors applied a method of depositing a polar compound derived from a polar solvent onto a composite solid electrolyte including a polymer cross-linked with a polyethylene oxide (PEO)-based copolymer modified with cross-linkable functional groups and a ceramic compound. The composite solid electrolyte thus prepared includes a polymer including a PEO-based copolymer with cross-linkable functional groups, a ceramic compound, and a polar compound. At least some of the cross-linkable functional groups cross-link with each other, forming a three-dimensional network structure of the polymer. The polar compound may be contained within the three-dimensional network structure in a gaseous state or may be bonded to the polymer chain.

[0041] It was confirmed that this composite solid electrolyte contains a small amount of polar compounds derived from the polar solvent in a gaseous state and exhibits improved ionic conductivity. This is thought to be because the polar compounds in the gaseous state affect the physical properties of the PEO-based copolymer, such as its crystallinity, increasing the chain mobility of the polymer chains, thereby improving the conductivity of the lithium ions contained in the composite solid electrolyte.

[0042] Furthermore, the composite solid electrolyte can exhibit superior ionic conductivity due to the ceramic compounds uniformly dispersed within the three-dimensional network structure.

[0043] Therefore, the composite solid electrolyte of an embodiment exhibits improved ionic conductivity without substantially including a liquid polar solvent or electrolyte, and can greatly contribute to the development of all-solid-state batteries with excellent physical properties.

[0044] Hereinafter, a composite solid electrolyte according to an embodiment of the present invention will be described in detail.

[0045] Composite solid electrolyte As described above, the composite solid electrolyte of one embodiment includes a polymer including a polyethylene oxide (PEO)-based copolymer having cross-linkable functional groups, a ceramic compound, and a polar compound, wherein at least a portion of the cross-linkable functional groups of the copolymer form cross-links with each other, the polymer forming a three-dimensional network structure, and the polar compound is contained in the three-dimensional network structure in a gaseous state or is bonded to the polymer chain.

[0046] In a specific example, 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.

[0047] Such a composite solid electrolyte is substantially free of a liquid solvent or electrolyte solution, but contains a trace amount of a polar compound contained in a gaseous state or bound thereto by deposition, as described below. Such a composite solid electrolyte can be identified, for example, by the absence of a liquid phase component on the surface of the electrolyte layer when an electrolyte layer containing the composite solid electrolyte is separated from an all-solid-state battery or the like and observed visually or with an electron microscope. In contrast, when a liquid polar solvent or electrolyte solution is injected into the composite solid electrolyte, a liquid phase component or a component exhibiting wettability can be observed on the surface of the electrolyte layer. Furthermore, as will be seen in the examples described below, a composite solid electrolyte containing the polar compound vapor-deposited in a gaseous state exhibits significantly higher ionic conductivity than a composite solid electrolyte containing the polar compound vapor-deposited in a liquid state. A comparison of ionic conductivities can also identify a composite solid electrolyte containing the polar compound vapor-deposited in a gaseous state.

[0048] In the composite solid electrolyte of the embodiment, the crosslinkable functional group may be directly bonded to the backbone of the PEO-based copolymer or may be bonded via an alkylene or alkylene oxide linker. Thus, the crosslinkable functional group may be bonded 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), 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.

[0049] 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, preferably different. When the cross-linking functional groups are different, multiple types of repeating units each containing these functional groups may be included. Furthermore, when multiple types of cross-linking functional groups are included, it may be easier to control the mobility and ionic conductivity of the polymer chain.

[0050] The crosslinkable functional group means a functional group that can form a crosslink between itself and / or with itself via a crosslinking agent, and may be attached to the main chain of a polymer chain in the form of a side chain.

[0051] In a more specific embodiment, the PEO-based copolymer containing a cross-linkable functional group may be a copolymer containing repeating units of the following Chemical Formulas 1 to 3:

[0052] [Chemical formula 1] [ka] [Chemical formula 2] [ka] [Chemical formula 3] [ka]

[0053] In the above formulas 1 to 3, R1 is -CH2-O-(CH2-CH2-O) k -R3, k is 0 to 20, and R3 is 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 (provided that an alkylene linker having 0 carbon atoms represents a single bond); l, m, and n are the number of repeats of the repeating unit, l and n are each independently an integer of 1 to 1000, and m is an integer of 0 to 1000.

[0054] 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 a three-dimensional network structure by the cross-linking may improve the mechanical properties of the composite solid electrolyte. In addition, the gaseous polar compound may be contained or bonded within the three-dimensional network structure, thereby providing a composite solid electrolyte having improved ionic conductivity, according to an embodiment.

[0055] It is also clear that the PEO-based copolymer may contain two or more repeating units of Chemical Formula 3 in which R2 is a cross-linking functional group different from each other, and may also contain one or more repeating units of Chemical Formula 2.

[0056] If l, m, and n are each less than 1, it may be difficult to form a polymer due to a small molecular weight, and if l, m, and n are each more than 1000, the viscosity may increase, reducing solubility during preparation of a polymer solution, making molding for preparing a composite solid electrolyte difficult. In particular, if the number of repeating units containing cross-linkable functional groups among l, m, and n exceeds 1000, the degree of cross-linking may increase excessively, reducing the mobility of polymer chains and decreasing ionic conductivity.

[0057] As used herein, a "hydroxy group" refers to an --OH group.

[0058] As used herein, a "carboxyl group" refers to a -COOH group.

[0059] As used herein, an "isocyanate group" refers to a -N=C=O group.

[0060] As used herein, a "nitro group" refers to a -NO2 group.

[0061] As used herein, a "cyano group" refers to a -CN group.

[0062] As used herein, an "amide group" refers to -C(=O)NR'R'', where R' and R'' can each independently be hydrogen or a C1 to C5 alkyl group, or R' and R'' together with the N atom to which they are attached can form a heterocycle having C4 to C8 atoms in the ring structure.

[0063] As used herein, the term "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 ranges from 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.

[0064] As used herein, an "allyl group" refers to the group -CH2-CH=CH2.

[0065] The weight-average molecular weight (Mw) of the copolymers including Formulas 1 to 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 composite 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 may increase, reducing solubility during polymer solution preparation, making molding for the preparation of a composite solid electrolyte difficult. In addition, the ionic conductivity of the composite solid electrolyte may decrease due to increased crystallinity and decreased chain mobility within the composite solid electrolyte.

[0066] In particular, when the number of repeating units of Formula 3 containing cross-linking functional groups among l, m, and n exceeds 1,000, the degree of cross-linking increases excessively, which may reduce the mobility of polymer chains and decrease the ionic conductivity of the composite solid electrolyte.

[0067] The copolymer may also be a random copolymer or a block copolymer.

[0068] In a specific embodiment of the present invention, the polar compound may be contained in or bound to the surface or interior of the polymer chain in a gaseous state. Specifically, the polar compound in a gaseous state may be diffused or dispersed among the polymer chains forming the three-dimensional network structure by the cross-linking, or may be adsorbed or bound to the surface or interior of the polymer chain.

[0069] The polar compound may be gas molecules of a polar solvent used in the deposition process, and may be adsorbed into the polymer during deposition and then diffused into the polymer chains, and may be bonded to the polymer chains or may be dispersed or diffused in the internal spaces between the polymer chains. The polar compound may be bonded to the polymer chains or dispersed in the internal spaces between the polymer chains, thereby improving the ionic conductivity of the final composite solid electrolyte.

[0070] Specifically, the polar compound bonded to or contained between the polymer chains can act as a plasticizer to plasticize the polymer. The plasticized polymer can increase the amorphous region inside, thereby improving the mobility of the polymer chains. The increased mobility of the polymer chains increases the ion hopping effect inside the polymer, thereby improving the ionic conductivity of the composite solid electrolyte.

[0071] 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 composite solid electrolyte.

[0072] The polar compound may include one or more compounds selected from the group consisting of carbonate compounds and sulfonyl compounds.

[0073] 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.

[0074] The content of the polar compound may be 0.1 wt % or more and less than 10 wt %, based on the total weight of the composite solid electrolyte. For example, the content of the polar compound may be 0.1 wt % or more, 1 wt % or more, or 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 the internal chain conformation of the polymer, and the ionic conductivity of the composite solid electrolyte is not improved. If the content of the polar compound is 10 wt % or more, the composite solid electrolyte may have the properties of a semi-solid battery due to a high liquid content, and the mechanical strength of the composite solid electrolyte may be reduced due to gelation of the polymer.

[0075] In one embodiment of the present invention, the composite solid electrolyte may include cross-links between cross-linkable functional groups. The composite solid electrolyte may further include a cross-linking agent, and may further include 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, thereby forming the three-dimensional network structure.

[0076] The crosslink may be a urethane crosslink, an ester crosslink, a hydrogen bond, or a bond formed by a radical polymerization reaction of a vinyl group at the end of an allyl group (-CH-CH=CH), but is not limited to these examples.

[0077] Furthermore, when a crosslinking agent is added in the process of preparing the composite solid electrolyte, a crosslinking bond may be formed between the crosslinking agent and the crosslinkable functional group. 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.

[0078] The crosslinking agent is not particularly limited as long as it is a polyfunctional crosslinking agent that 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-(acryloyloxy)-2-hydroxypropyl methacrylate, 3,5-bis(acrylamido)benzic acid (3,5-bis(acryloylamido)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 acrylate, glycidylmethacrylate, 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.

[0079] 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 polymer chains and result in a decrease in ionic conductivity.

[0080] In one embodiment of the present invention, the composite solid electrolyte may further include a lithium salt. The lithium salt may be present in a dissociated ionic state in the internal space between the polymer chains, thereby improving the ionic conductivity of the composite solid electrolyte. At least a portion of the cations and / or anions dissociated from the lithium salt may be present in a state bound to the polymer chains, thereby exhibiting mobility during charge / discharge of the battery.

[0081] The lithium salts include (CF3SO2)2NLi (Lithium bis(trifluoromethanesulphonyl)imide, LiTFSI), (FSO2)2NLi (Lithium bis(fluorosulfonyl)imide, LiFSI), LiNO3, LiOH, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl10 , LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiSCN, LiC(CF3SO2)3, lithium chloroborane, lithium lower aliphatic carboxylate, and lithium tetraphenylborate.

[0082] The lithium salt may be included in an amount of 25 to 45 parts by weight, 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, based on 100 parts by weight of the PEO-based copolymer having a cross-linkable functional group. If the content of the lithium salt is less than 25 parts by weight, the ionic conductivity of the composite solid electrolyte may be reduced, and if it exceeds 45 parts by weight, the mechanical strength may be reduced.

[0083] The composite solid electrolyte may include a ceramic compound having lithium ion transport ability for improving the conductivity of lithium ions, preferably a ceramic compound containing lithium atoms but capable of transporting lithium ions without storing lithium, thereby improving the ionic conductivity of the composite solid electrolyte.

[0084] In addition, the ceramic compound may be included among the cross-linked polymer chains, for example, in a uniformly dispersed state within the three-dimensional network structure. The ceramic compound may be added during the cross-linking process and may be uniformly dispersed without aggregation among the polymer chains formed by the cross-linking. Such a uniformly dispersed ceramic compound may be advantageous for improving the mechanical strength and ionic conductivity of the composite solid electrolyte.

[0085] The ceramic compound may also be in the form of particles. Due to its particle morphology, the ceramic compound can be contained in a more uniformly dispersed state within the composite solid electrolyte. The ceramic compound particles may be spherical and have a diameter of 100 nm to 1000 nm. If the diameter is less than 100 nm, the amorphization effect due to reduced crystallinity of the polymer may be minimal. If the diameter is more than 1000 nm, the dispersibility may be reduced due to increased aggregation between particles, making uniform dispersion difficult.

[0086] The ceramic compound may be an oxide-based or phosphate-based compound, for example, an oxide-based solid electrolyte in the form of lithium metal oxide or lithium metal phosphate. More specifically, the ceramic compound may be a garnet-type lithium-lanthanum-zirconium oxide (LLZO, Li7La3Zr2O 12 ) compounds, perovskite-type lithium-lanthanum-titanium oxides (LLTO, Li3xLa 2 / 3-x TiO3) compounds, phosphate-based NASICON-type lithium-aluminum-titanium phosphate (LATP, Li 1+x Al x Ti 2-x (PO4)3) compounds, lithium-aluminum-germanium phosphate system (LAGP, Li 1.5 Al 0.5 Ge 1.5The solid electrolyte may be at least one 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.

[0087] The oxide-based solid electrolyte made of the oxide-based or phosphate-based compound generally has a maximum resistance of 10 -4 ~10 -3 It has an ionic conductivity of 100 S / cm, is stable in the high voltage range, is stable in air, and has the advantages of being easy to synthesize and handle.

[0088] Therefore, the composite solid electrolyte further includes the ceramic compound mixed therein, thereby compensating for the disadvantages of the polymer-based solid electrolyte.

[0089] In addition, the ceramic compound has high high-temperature stability because it does not easily burn or ignite even under high-temperature conditions of 400° C. or higher. Therefore, when the composite solid electrolyte contains the ceramic compound, it is possible to improve the mechanical strength of the composite solid electrolyte as well as its high-temperature stability and ionic conductivity.

[0090] The ceramic compound may be included in an amount of 10 to 100 parts by weight, or 10 to 60 parts by weight, based on 100 parts by weight of the PEO-based copolymer containing a cross-linkable functional group.

[0091] If the ceramic compound is contained in an excessively small amount, the polymer crystallinity and amorphous effect of the ceramic compound may be reduced, resulting in a small increase in the ionic conductivity of the composite solid electrolyte, and the mechanical properties may not reach the expected level due to the formation of a composite.

[0092] If the ceramic compound is contained in an excessively large amount, the ceramic compound may not be uniformly dispersed in the polymer, causing the ceramic compound particles to aggregate together, resulting in a composite solid electrolyte having reduced ionic conductivity.

[0093] Method for manufacturing composite solid electrolyte In another embodiment of the present invention, the method for manufacturing the composite solid electrolyte may include the steps of: (S1) mixing a PEO (polyethylene oxide)-based copolymer having a cross-linkable functional group with a ceramic compound, and then cross-linking the PEO-based copolymer contained in the mixture; and (S2) depositing a polar solvent on the mixture including the polymer cross-linked in step (S1).

[0094] The PEO copolymer containing the crosslinkable functional group has been described above.

[0095] Each step will be explained in more detail below.

[0096] In the step (S1), a PEO (polyethylene oxide) copolymer containing a cross-linkable functional group is mixed with a ceramic compound, and then a cross-linking reaction is carried out on the PEO copolymer contained in the mixture, thereby producing a polymer having the above-mentioned three-dimensional network structure.

[0097] The cross-linking reaction in step (S1) may be carried out in the presence of one or more additives selected from the group consisting of a cross-linking agent and an initiator.

[0098] In order to form a composite solid electrolyte, a lithium salt may be added in step (S1).

[0099] The ceramic compound may be the same as that used in the composite solid electrolyte described above, and the content may be the same.

[0100] The cross-linking reaction may be carried out during the drying process after a solution containing the PEO copolymer and the ceramic compound is applied to a substrate to form a coating film.

[0101] Specifically, the mixed solution may be prepared by mixing the PEO-based copolymer and the ceramic compound in a solvent, and then further mixing a crosslinker, an initiator, and / or a lithium salt. Alternatively, a solution containing the PEO-based copolymer, the crosslinker, the initiator, and / or the lithium salt may be prepared first, and then the ceramic compound may be added to prepare a mixed solution or suspension.

[0102] The solvent is not particularly limited as long as it can be mixed with 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). Such solvents serve as reaction media for crosslink formation and are distinct from polar solvents contained in liquid electrolytes, etc., and are completely removed by drying after crosslinking.

[0103] The concentration of the mixed solution can be appropriately adjusted taking into consideration the smoothness of the molding process for preparing the composite 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 too dilute, resulting in a decrease in the mechanical strength of the composite solid electrolyte or the electrolyte may flow when applied to a substrate. If the concentration is more than 20 wt%, it may be difficult to dissolve the lithium salt in the polymer solution to the desired concentration, or the high viscosity may reduce solubility or make it difficult to apply the solution to a uniform thin film.

[0104] The substrate is not particularly limited as long as it can serve 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.

[0105] 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.

[0106] The coating film formed on the substrate by the above coating method may be formed into a film-shaped polymer from which the residual solvent has been completely removed through a drying process. The drying may 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 may remove a portion of the solvent through room temperature drying, and the secondary drying process may completely remove the solvent through high-temperature vacuum drying. The high-temperature drying may 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 may not be completely removed, and if it exceeds 130°C, the polymer may shrink, making it difficult to form a uniform electrolyte membrane.

[0107] The crosslinking agent may form a bond with the crosslinkable functional group. The type of the crosslinking agent, the content of the crosslinking agent, and the type of bond with the crosslinkable functional group are as described above.

[0108] In addition, the initiator may induce 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, such as an allyl group.

[0109] The initiator is not particularly limited as long as it is an initiator that can induce a radical polymerization reaction between the cross-linkable functional groups. For example, the initiator may include one or more selected from the group consisting of benzoyl peroxide, azobisisobutyronitrile, lauroyl peroxide, cumene hydroperoxide, diisopropylphenyl hydroperoxide, tert-butyl hydroperoxide, p-menthane hydroperoxide, and 2,2'-azobis(2-methylpropionitrile).

[0110] The initiator may be used in an amount of 0.5 to 2 parts by weight per 100 parts by weight of the PEO-based copolymer containing cross-linkable functional groups. When used in this range, the initiator can induce a radical polymerization reaction between the cross-linkable functional groups, thereby enabling efficient formation of cross-links.

[0111] The content and type of the lithium salt are as described above.

[0112] In step (S2), a polar solvent may be deposited on the crosslinked polymer-containing mixture prepared in step (S1) to prepare the composite solid electrolyte of the embodiment. In this case, the gas molecules of the polar solvent may be a polar compound according to the embodiment.

[0113] The deposition may 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 interior. In this manner, the vapor of the polar compound may be uniformly dispersed on the surface and / or interior of the polymer through deposition at room temperature or by heating, and the polar compound gas molecules may be bound to the polymer chains or may be uniformly dispersed or diffused within the interior space of the polymer chains.

[0114] When the polar solvent is kept at room temperature during the 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 change in the conformation of the polymer chains cross-linked within the polymer.

[0115] Furthermore, heating the polar solvent during deposition can increase the 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 exhibits improved heat resistance and can withstand temperatures up to 80°C when a cross-linked structure is formed, thereby increasing the deposition rate. The heating method can be any method capable of supplying energy sufficient to generate vapor. Examples of suitable heating methods include, but are not limited to, direct heating using a burner or stove, and indirect heating using a heater or steam tube.

[0116] If the heating temperature is too high, the polar solvent may boil above its boiling point, or the solvent may undergo structural changes, or polymer deformation may occur. In addition, there is a disadvantage that it is difficult to control the evaporation rate of the polar solvent during deposition. Therefore, in order to deposit a small amount of polar solvent, it may be preferable to perform deposition at a heating temperature within the appropriate range as specified above.

[0117] All solid state battery An additional embodiment of the present invention relates to an all-solid-state battery further including the composite solid electrolyte. The all-solid-state battery includes an anode, a cathode, and a composite solid electrolyte interposed between the anode and the cathode, and the composite solid electrolyte is according to any one of the above-described embodiments.

[0118] Specifically, the composite 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 the ceramic compound is uniformly dispersed, thereby improving ionic conductivity, and therefore the composite solid electrolyte may be suitable as an electrolyte for an all-solid-state battery.

[0119] 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.

[0120] The positive electrode active material layer includes a positive electrode active material, a binder, and a conductive material.

[0121] In addition, the positive electrode active material is not particularly limited as long as it is a material capable of reversibly inserting and releasing lithium ions, and examples thereof include 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, and 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), and compounds substituted with one or more transition metals; 1+yMn 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; 1-y M y Ni-site lithium nickel oxide represented by the chemical formula LiMnO2 (where M=Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and y=0.01 to 0.3); 2-y M y Examples of suitable lithium manganese composite oxides include, but are not limited to, lithium manganese composite oxides represented by 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.

[0122] 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 increased.

[0123] The binder is a component that aids in bonding the positive electrode active material to the conductive material and the current collector, and is selected from the group consisting of styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylic The binder may include one or more 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 one or more selected from the group consisting of styrene-butadiene rubber, polytetrafluoroethylene, carboxymethyl cellulose, polyacrylic acid, lithium polyacrylate, and polyvinylidene fluoride.

[0124] 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, and 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.

[0125] Furthermore, the conductive material is not particularly limited as long as it prevents side reactions in the internal environment of the all-solid-state battery, does not induce chemical changes in the battery, and has excellent electrical conductivity. Representative examples include graphite or conductive carbon, and examples thereof 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 substances 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. However, the conductive material is not necessarily limited thereto.

[0126] 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 %, the electrical conductivity improvement effect may be difficult to expect or the electrochemical characteristics of the battery may be degraded. If the content 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.

[0127] 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.

[0128] The positive electrode current collector is not particularly limited as long as it does not induce chemical changes in the all-solid-state battery and has high electronic conductivity. For example, the positive electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium, palladium, baked carbon, copper or stainless steel whose surface is treated with carbon, nickel, silver, or the like, or an aluminum-cadmium alloy.

[0129] 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 have various forms such as a film, sheet, foil, mesh, net, porous body, foam, or nonwoven fabric.

[0130] The positive electrode may be fabricated by a conventional method. Specifically, the positive electrode active material, conductive material, and 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 compression-molded into a current collector to improve electrode density. The organic solvent is preferably one that can uniformly disperse the positive electrode active material, binder, and conductive material and is easily evaporated. Specific examples of the organic solvent include acetonitrile, methanol, ethanol, tetrahydrofuran, water, isopropyl alcohol, dimethyl sulfoxide (DMSO), and N-methyl-2-pyrrolidone (NMP).

[0131] 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.

[0132] 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.

[0133] 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).

[0134] Preferably, the negative electrode active material may be lithium metal, specifically in the form of a lithium metal thin film or lithium metal powder.

[0135] 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.

[0136] The binder is the same as that described above in the positive electrode active material layer.

[0137] The conductive material is the same as that described above in the positive electrode active material layer.

[0138] 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, baked carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. Similarly 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.

[0139] 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. For example, methods such as compression bonding, coating, and vapor deposition may be used. Furthermore, the negative electrode of the present invention also includes a battery in which a thin lithium film is formed on the metal plate by initial charging after assembling the battery without a thin lithium film on the negative electrode current collector.

[0140] 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.

[0141] Specific examples of the device include, but are not limited to, power tools driven by electric 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.

[0142] Preferred examples are presented below to aid in understanding the present invention. However, the following examples are provided only to facilitate understanding of the invention, and the present invention is not limited thereto.

[0143] Example Example 1: Preparation of composite solid electrolyte 1) Preparation of polymers including copolymers A polyethylene oxide (PEO) copolymer of the following formula 1a was prepared.

[0144] [Chemical formula 1a] [ka] In the above formula 1a, R1 is -CH2-O-(CH2-CH2-O) k R2 was -CH2-O-CH2-CH=CH2, k was 2, the l:m:n ratio was 85:13:2, and the weight average molecular weight (Mw) of the copolymer was about 2,000,000 g / mol.

[0145] The copolymer of formula 1a has an allyl group as a cross-linking functional group, which is linked via a methylene oxide linker.

[0146] The polyethylene oxide copolymer was mixed with trimethylolpropane trimethacrylate as a crosslinker, benzoyl peroxide as an initiator, LiTFSI as a lithium salt, and LSTP as a ceramic compound in acetonitrile as a solvent to prepare a mixed solution of the polymer and the ceramic compound, which was then stirred for 24 hours using a magnetic bar. The mixed solution of the polyethylene oxide copolymer and the ceramic compound was prepared by mixing 100 parts by weight of the polyethylene oxide copolymer with 20 parts by weight of trimethylolpropane trimethacrylate as a crosslinker, 1 part by weight of benzoyl peroxide as an initiator, 36 parts by weight of LiTFSI as a lithium salt, and 40 parts by weight of LSTP as a ceramic compound. The acetonitrile solvent was used so that the concentration of the polymer polyethylene oxide copolymer in the mixed solution was 11.1 wt%, and the concentrations of the polymer polyethylene oxide copolymer and the ceramic compound were 14.9 wt%.

[0147] The prepared mixed solution was solution-cast on the lower substrate of a coin cell, and then dried at room temperature for 12 hours, and then dried at 100°C for 3 hours to prepare an electrolyte film with a thickness of 200 μm.

[0148] 2-step) Preparation of composite 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 solvent was allowed to evaporate naturally at room temperature for 72 hours. EMC vapor was then introduced into the polymer attached to the upper part of the chamber and deposited on the polymer to produce a composite solid electrolyte.

[0149] Comparative Example: Comparative Example 1: Composite solid electrolyte containing only modified PEO + ceramic compound (solvent-free) A composite solid electrolyte was prepared in the same manner as in Example 1, except that step 2) of Example 1, ie, the step of depositing the EMC solvent, was omitted.

[0150] Comparative Example 2: Modified PEO + ceramic compound + solvent-rich composite solid electrolyte A composite solid electrolyte was prepared in the same manner as in Example 1, except that the EMC solvent (12 wt%) was not deposited on the composite solid electrolyte prepared in step 1) of Example 1, but was directly injected as a liquid solvent. The EMC solvent was directly injected so that the content of the EMC solvent was 12 wt% based on the total weight of the prepared composite solid electrolyte.

[0151] Comparative Example 3: Unmodified PEO + ceramic compound + polar solvent-deposited composite solid electrolyte A composite solid electrolyte was prepared in the same manner as in Example 1, except that a polyethylene oxide (PEO) homopolymer (weight average molecular weight: about 4,000,000 g / mol) without a substituted crosslinkable functional group was used, and a crosslinking agent and an initiator were not added.

[0152] Comparative Example 4: Modified PEO + polar solvent deposited polymer solid electrolyte A polymer solid electrolyte was prepared in the same manner as in Example 1, except that no ceramic compound was added.

[0153] Experimental example Experimental Example 1: Measurement of polar compound content The polar compound content can be measured by monitoring the weight of the liquid phase evaporated over time while heating the solid electrolyte test piece using a balance. For example, a heated electronic balance (AND MS-70) can be used to monitor the weight of the liquid phase evaporated over time while heating the test piece at a temperature of 55 to 70°C or 60°C. When the amount of polar compound evaporated over time reaches saturation, the saturated amount is considered to be the total amount of polar compound contained within the solid electrolyte. In the examples and comparative examples, the polar compound may be ethyl methyl carbonate (EMC).

[0154] Experimental Example 2: Measurement of ionic conductivity of composite solid electrolyte To measure the ionic conductivity of the composite solid electrolytes prepared in the examples and comparative examples, a 1.7671 cm 2 The composite solid electrolyte was formed on the lower substrate of a coin cell of the same size, and then SUS was used as a blocking electrode to prepare a coin cell for measuring ionic conductivity.

[0155] Resistance was measured using an electrochemical impedance spectrometer (EIS, VM3, BioLogic Science Instrument) at 25°C under conditions of an amplitude of 10 mV and a scan range of 1 Hz to 0.1 MHz, and the ionic conductivity of the composite solid electrolyte was calculated using the following Equation 1:

[0156] [Formula 1]

number

[0157] In the above equation 1, σi is the ionic conductivity (S / cm) of the composite solid electrolyte, R is the resistance (Ω) of the composite solid electrolyte measured by the electrochemical impedance spectroscopy, L is the thickness (μm) of the composite solid electrolyte, and A is the area (cm 2 The composite solid electrolyte sample had L = 200 μm and A = 1.7671 cm 2 The following was used.

[0158] Table 1 below shows the measurement results of the content and ionic conductivity of EMC deposited (or contained) in the composite (or polymer) solid electrolyte.

[0159] [Table 1]

[0160] The ionic conductivity of the modified PEO-based solid electrolyte (Comparative Example 1) and the solid electrolyte into which EMC in a liquid state was directly injected (Comparative Example 2) was 10-4 S / cm level, whereas the composite solid electrolyte (Example 1) in which the modified PEO contains a gaseous polar solvent (EMC) during the deposition process and the ceramic compound is dispersed has an ionic conductivity of 10 -3 It was confirmed that the conductivity was improved to the S / cm level. This is thought to be because the vapor phase polar solvent (EMC) diffuses into the crosslinked 3D network structure of PEO or is adsorbed or bonded to the polymer chains, improving the mobility of lithium ions.

[0161] In addition, in the case of a general PEO-based solid electrolyte that was not crosslinked or modified as in Comparative Example 3, the effect of improving ionic conductivity by vapor deposition of a polar solvent was not observed, and in particular, an internal short state was confirmed in which ionic conductivity could not be measured due to the collapse of the internal structure of the polymer due to the lack of a crosslinked structure.

[0162] In addition, the modified PEO in Comparative Example 4 contains a polar solvent (EMC) in the deposition process, but the solid electrolyte does not contain a ceramic compound. The ionic conductivity is 10 -4 It was confirmed that the ionic conductivity was somewhat lower than that of Example 1 due to the absence of a ceramic compound, at the S / cm level.

[0163] Experimental Example 3: Measurement of low-temperature ionic conductivity of composite solid electrolytes The ionic conductivity of the composite solid electrolytes of Example 1 and Comparative Example 1 was measured at temperatures between -30°C and 0°C, and the results are shown in Table 2 below. However, the measurement method and conditions for ionic conductivity, except for the measurement temperature, were the same as those in Experimental Example 2.

[0164] [Table 2]

[0165] Referring to Table 2, it was confirmed that the composite solid electrolyte of Example 1 exhibited excellent ionic conductivity even at low temperatures compared to Comparative Example 1.

Claims

1. The composition includes a polymer including a PEO (polyethylene oxide) copolymer containing a cross-linkable functional group, a ceramic compound, and a polar compound; at least a part of the cross-linking functional groups form cross-links with each other, and the polymer forms a three-dimensional network structure; A composite solid electrolyte, wherein the polar compound is contained in the three-dimensional network structure in a gaseous state or is bonded on the polymer chain.

2. 2. The composite solid electrolyte according to claim 1, wherein the gaseous polar compound is dispersed among the polymer chains forming the three-dimensional network structure, or is adsorbed or bonded to the surface or inside of the polymer chains.

3. The composite solid electrolyte of claim 1 , wherein the composite solid electrolyte further comprises a cross-linking agent.

4. The composite solid electrolyte according to claim 3 , wherein at least a portion of the cross-linkable functional groups form cross-links with each other via the cross-linking agent.

5. The composite solid electrolyte of claim 1 , wherein the PEO-based copolymer comprises two or more types of cross-linking functional groups.

6. the cross-linking 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 composite solid electrolyte of claim 1, wherein the cation 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.

7. The composite solid electrolyte of claim 1 , wherein the composite solid electrolyte further comprises a lithium salt.

8. The composite solid electrolyte of claim 1 , wherein the PEO (polyethylene oxide) copolymer is a copolymer including repeating units of the following formulas 1 to 3: [Chemical formula 1] 【Chemical 1】 [Chemical formula 2] 【Chemistry 2】 [Chemical formula 3] 【Chemistry 3】 In the above 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 (provided that an alkylene linker having 0 carbon atoms represents a single bond), l, m, and n are the number of repeats 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.

9. The PEO-based copolymer is ２ The composite solid electrolyte according to claim 8 , wherein the repeating units of Chemical Formula 3 each have different cross-linking functional groups.

10. 2. The composite solid electrolyte of claim 1, wherein the content of the polar compound is 0.1 wt % or more and less than 10 wt % based on the total weight of the composite solid electrolyte.

11. The composite solid electrolyte according to claim 1 , wherein the polar compound comprises at least one selected from the group consisting of carbonate-based compounds and sulfonyl-based compounds.

12. 2. The composite solid electrolyte according to claim 1, wherein the polar compound 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.

13. The composite solid electrolyte of claim 1 , wherein the ceramic compound comprises an oxide-based solid electrolyte of lithium metal oxide or lithium metal phosphate.

14. 2. The composite solid electrolyte of claim 1, wherein the ceramic compound comprises one or more oxide-based solid electrolytes selected from the group consisting of lithium-lanthanum-zirconium oxide (LLZO) compounds, lithium-silicon titanium phosphate (LSTP) compounds, lithium-lanthanum-titanium oxide (LLTO) compounds, lithium-aluminum-titanium phosphate (LATP) compounds, lithium-aluminum-germanium phosphate (LAGP) compounds, and lithium-lanthanum-zirconium-titanium oxide (LLZTO) compounds.

15. (S1) mixing a PEO (polyethylene oxide) copolymer containing a cross-linking functional group with a ceramic compound, and then performing a cross-linking reaction on the PEO copolymer contained in the mixture; (S2) a step of depositing a polar solvent onto the mixture containing the polymer crosslinked in the step (S1).

16. The method for producing a composite solid electrolyte according to claim 15, wherein the step (S1) is carried out in the presence of one or more additives selected from the group consisting of a crosslinking agent and an initiator.

17. The method for producing a composite solid electrolyte according to claim 15, wherein the polar solvent includes at least one selected from the group consisting of carbonate-based solvents and sulfonyl-based solvents.

18. 18. The method for producing a composite solid electrolyte according to claim 15, wherein in step (S2), vapor of the polar solvent is deposited on the polymer so that a content of the polar solvent is 0.1 wt % or more and less than 10 wt % based on a total weight of the composite solid electrolyte.

19. 15. An all-solid-state battery comprising an electrolyte layer comprising the composite solid electrolyte of claim 1.

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