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, and a ceramic compound, wherein at least a portion of the cross-linkable functional groups form cross-links with each other, forming a three-dimensional network structure of the polymer, and the ceramic compound is contained within the three-dimensional network structure.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0132767, filed October 14, 2022, and Korean Patent Application No. 10-2023-0136065, 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 and positive electrodes are separated by a separator, so if the separator is damaged by deformation or external impact, a short circuit may occur, which can lead to risks such as overheating or explosion. Therefore, the development of a solid electrolyte that can ensure safety is a very important issue in the field of lithium-ion secondary batteries.

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

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

[0006] These conventional hybrid (composite) solid electrolytes are made by dispersing inorganic powders, such as oxide ceramics, in a polymer matrix. They offer advantages over existing liquid electrolytes, such as higher ignition and combustion stability, and higher ionic conductivity than polymer solid 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 movement of lithium ions within the composite solid electrolyte, limiting the ionic conductivity of the composite solid electrolyte.

[0007] To overcome these limitations of conventional composite solid electrolytes, efforts have been made to improve the ionic conductivity of composite solid electrolytes 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 composite solid electrolytes using only such polymer structural modifications or plasticizer addition methods.

[0008] Therefore, there is a need to develop a technology that can improve the ionic conductivity of composite solid electrolytes without modifying the polymer structure or adding plasticizers. [Prior art documents] [Patent documents]

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

[0010] The present invention provides a composite solid electrolyte having improved mechanical strength and ionic conductivity by uniformly dispersing a ceramic compound in a cross-linked structure of a predetermined polymer, and a method for manufacturing the same.

[0011] The present invention also provides an all-solid-state battery including a composite solid electrolyte having improved mechanical strength and 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 PEO (polyethylene oxide) copolymer containing cross-linkable functional groups; and a ceramic compound; wherein at least a portion of the cross-linkable functional groups form cross-links with each other to form a three-dimensional network structure of the polymer; and the ceramic compound is contained within the three-dimensional network structure.

[0013] Such a composite solid electrolyte may further include a crosslinking agent, and at least a portion of the crosslinkable functional groups of the PEO-based copolymer may form crosslinks with each other via the crosslinking agent.

[0014] 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 an alkylene linker having 0 carbon atoms represents a single bond), and may be one or more 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.

[0015] Meanwhile, in one embodiment, the composite solid electrolyte may further include a lithium salt dispersed on the polymer forming the three-dimensional network structure. 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 are mobile during charge / discharge of the battery.

[0016] In a specific example, the PEO (polyethylene oxide) copolymer may be a copolymer containing repeating units of the following chemical formulas 1 to 3:

[0017] [ka]

[0018] In the above chemical formulas 1 to 3, R1 is -CH2-O-(CH2-CH2-O) k -R3, k is 0 to 20, and R3 represents an alkyl group having 1 to 5 carbon atoms; R2 represents a substituent in which one or more crosslinkable functional groups selected from the group consisting of a hydroxyl group, a carboxyl group, an isocyanate group, a nitro group, a cyano group, an amine group, an amide group, an epoxy group, and an allyl group are bonded to a polymer chain via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (however, an alkylene linker having 0 carbon atoms represents a single bond); l, m, and n are the repeating numbers of the repeating unit, l and n are each independently an integer of 1 to 1,000, and m is an integer of 0 to 1,000.

[0019] In addition, in the composite solid electrolyte of the embodiment, the ceramic compound may 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.

[0020] Meanwhile, according to another embodiment of the present invention, there is provided a method for manufacturing the composite solid electrolyte of the above embodiment, including the steps of: forming a mixture of a PEO (polyethylene oxide)-based copolymer containing a cross-linkable functional group and a ceramic compound; and performing a cross-linking reaction on the PEO-based copolymer contained in the mixture.

[0021] In such a manufacturing method, the cross-linking reaction step may be carried out in the additional presence of one or more additives selected from the group consisting of cross-linking agents and initiators.

[0022] According to an additional embodiment of the invention, there is provided an all-solid-state battery including an electrolyte layer comprising the composite solid electrolyte of the above embodiment. [Effects of the Invention]

[0023] The composite solid electrolyte according to the present invention can exhibit improved mechanical properties and ionic conductivity by uniformly dispersing the ceramic compound in the composite solid electrolyte while maintaining the inherent structural characteristics of the polymer without deformation or destruction of the polymer chain. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, the embodiments of the invention will be described in more detail for better understanding of the invention.

[0025] The terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, in accordance with the principle that the inventor can appropriately define the concept of the term in order to best describe his or her invention.

[0026] The term "three-dimensional network structure" as used herein refers to a structure including a three-dimensional frame and an internal space formed by the frame, and the frame may include polymer chains including crosslinks formed by the crosslinking functional groups, for example, crosslinks between crosslinking functional groups and / or crosslinks between the crosslinking functional groups and a crosslinking agent. The three-dimensional network structure may also be referred to as a crosslinked structure.

[0027] Meanwhile, in the past, in order to improve the ionic conductivity of solid electrolytes, composite solid electrolytes have been prepared by mixing ceramic compounds such as oxides into a polymer matrix. However, such composite solid electrolytes have problems such as reduced ionic conductivity when oxide-based ceramic particles are unevenly distributed in the polymer matrix or when a highly crystalline polymer such as polyethylene oxide is used as the polymer.

[0028] Therefore, the present inventors prepared a polymer by cross-linking a polyethylene oxide (PEO) copolymer modified with a cross-linking functional group, mixed the PEO copolymer with a ceramic compound, and then induced cross-linking through coating and drying processes, thereby preparing a composite solid electrolyte containing a polymer in which the ceramic compound was uniformly dispersed among the polymer chains.

[0029] As a result, the inventors have confirmed that it is possible to provide a composite solid electrolyte that exhibits improved mechanical properties and ionic conductivity compared to existing composite solid electrolytes, and have completed the present invention.

[0030] The composite solid electrolyte of the embodiment will be specifically described below.

[0031] Composite solid electrolyte The composite solid electrolyte according to one embodiment of the invention comprises: The ceramic compound comprises a polymer including a PEO (polyethylene oxide) copolymer containing cross-linkable functional groups; and a ceramic compound, wherein at least a portion of the cross-linkable functional groups form cross-links with each other to form a three-dimensional network structure of the polymer, and the ceramic compound is contained within the three-dimensional network structure.

[0032] The composite solid electrolyte may include a three-dimensional network structure formed by a cross-linked polymer structure. The three-dimensional network structure may include a three-dimensional frame and an internal space between the frames, the frame including polymer chains with cross-links formed by the cross-linking functional groups, and the internal space may include a ceramic compound.

[0033] The crosslinking bonds formed by the crosslinking functional groups forming the framework may include crosslinking bonds between the crosslinking functional groups and / or crosslinking bonds between the crosslinking functional groups and a crosslinking agent. When the composite solid electrolyte further includes a crosslinking agent, at least some of the crosslinking functional groups may form crosslinks with each other via the crosslinking agent.

[0034] The ceramic compound is dispersed in the internal space of the three-dimensional network structure, allowing the ceramic compound to be uniformly dispersed. The uniformly dispersed ceramic compound morphology can further improve the mechanical strength and ionic conductivity of the composite solid electrolyte.

[0035] In other words, some of the cross-linked polymer chains act as a plasticizer to ensure flexibility, reducing the crystallinity that has been a chronic problem with PEO. Additionally, some of the cross-linked polymer chains act as a cross-linking agent to form a three-dimensional network, allowing the ceramic compound to be more uniformly dispersed.

[0036] Meanwhile, in the PEO copolymer, the cross-linkable functional group may be bonded directly to the main chain of the PEO copolymer or via an alkylene or alkylene oxide linker. Therefore, the cross-linkable functional group may be bonded via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (however, an alkylene linker having 0 carbon atoms represents a single bond), and may be one or more groups selected from the group consisting of a hydroxyl group, a carboxyl group, an isocyanate group, a nitro group, a cyano group, an amine group, an amide group, an epoxy group, and an allyl group.

[0037] In one embodiment of the invention, the cross-linking functional groups may be of two or more types. The cross-linking functional groups may be the same or different, and preferably different. When the cross-linking functional groups are different, 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.

[0038] The cross-linkable functional group means a functional group capable of forming a cross-link between itself and / or with a cross-linking agent, and can be bonded to the main chain of a polymer chain in the form of a side chain.

[0039] In a more specific embodiment, the PEO-based copolymer containing cross-linkable functional groups may be a copolymer containing repeating units of the following chemical formulas 1 to 3:

[0040] [ka]

[0041] In the above chemical formulas 1 to 3, R1 is -CH2-O-(CH2-CH2-O) k -R3, k is 0 to 20, and R3 represents an alkyl group having 1 to 5 carbon atoms; R2 represents a substituent in which one or more crosslinkable functional groups selected from the group consisting of a hydroxyl group, a carboxyl group, an isocyanate group, a nitro group, a cyano group, an amine group, an amide group, an epoxy group, and an allyl group are bonded to a polymer chain via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (however, an alkylene linker having 0 carbon atoms represents a single bond); l, m, and n are the repeating numbers of the repeating unit, l and n are each independently an integer of 1 to 1,000, and m is an integer of 0 to 1,000.

[0042] For example, the cross-linkable functional group of R2 may form a polymer having a matrix form of a three-dimensional network structure formed by the cross-linking. The formation of the three-dimensional network structure by the cross-linking may improve the mechanical properties of the composite solid electrolyte, and the ceramic compound may be uniformly dispersed within the three-dimensional network structure, thereby providing a composite solid electrolyte having improved ionic conductivity according to an embodiment.

[0043] It is also clear that the PEO copolymer may contain two or more repeating units of Formula 3, in which R2 is a different cross-linking functional group, and may also contain one or more repeating units of Formula 2.

[0044] If l, m, and n are each less than 1, the molecular weight is small, making it difficult to form a polymer, and if l, m, and n are each more than 1000, the viscosity increases, reducing solubility during preparation of a polymer solution, making molding for preparing a 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 increases excessively, reducing the mobility of polymer chains and decreasing the ionic conductivity of the solid electrolyte.

[0045] As used herein, a "hydroxy group" refers to an --OH group.

[0046] As used herein, a "carboxyl group" refers to a -COOH group.

[0047] As used herein, an "isocyanate group" refers to a -N=C=O group.

[0048] As used herein, a "nitro group" refers to the -NO2 group.

[0049] As used herein, a "cyano group" refers to a -CN group.

[0050] As used herein, an "amide group" refers to -C(=O)NR'R", where R' and R" are each independently hydrogen or a C1-C5 alkyl group, or R' and R" together with the N atom to which they are attached can form a heterocycle having C4-C8 atoms in the ring structure.

[0051] In this specification, the "amine group" may be selected from the group consisting of monoalkylamine groups, monoarylamine groups, monoheteroarylamine groups, dialkylamine groups, diarylamine groups, diheteroarylamine groups, alkylarylamine groups, alkylheteroarylamine groups, and arylheteroarylamine groups. The number of carbon atoms is not particularly limited, but preferably 1 to 30. Specific examples of the amine group include, but are not limited to, methylamine groups, dimethylamine groups, ethylamine groups, diethylamine groups, phenylamine groups, naphthylamine groups, biphenylamine groups, dibiphenylamine groups, anthracenylamine groups, 9-methylanthracenylamine groups, diphenylamine groups, phenylnaphthylamine groups, ditolylamine groups, phenyltolylamine groups, triphenylamine groups, biphenylnaphthylamine groups, phenylbiphenylamine groups, biphenylfluorenylamine groups, phenyltriphenylenylamine groups, and biphenyltriphenylenylamine groups. Furthermore, the term "amino group" refers to -NH.

[0052] As used herein, an "allyl group" refers to the group -CH2-CH=CH2.

[0053] The weight-average molecular weight (Mw) of the copolymers including Formulas 1-3 may be 100,000 g / mol to 2,000,000 g / mol, specifically, 100,000 g / mol or more, 200,000 g / mol or more, or 300,000 g / mol or more, or 1,600,000 g / mol or less, 1,800,000 g / mol or less, or 2,000,000 g / mol or less. If the weight-average molecular weight (Mw) of the copolymer is less than 100,000 g / mol, the mechanical properties of the resulting solid electrolyte may not be satisfactory. If the weight-average molecular weight (Mw) of the copolymer is more than 2,000,000 g / mol, the viscosity increases, reducing solubility during polymer solution preparation, making molding for solid electrolyte preparation difficult. In addition, the ionic conductivity of the composite solid electrolyte may decrease due to increased crystallinity and reduced chain mobility within the solid electrolyte.

[0054] In particular, when the repeating number of the repeating unit of Formula 3 containing a cross-linking functional group among l, m, and n exceeds 1000, the degree of cross-linking increases excessively, which may reduce the mobility of the polymer chain and decrease the ionic conductivity of the composite solid electrolyte.

[0055] The copolymer may also be a random copolymer or a block copolymer.

[0056] 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, so that at least some of the cross-linkable functional groups may form cross-links with each other via the cross-linking agent. As a result, the composite solid electrolyte may further include cross-links between the cross-linking agent and the cross-linkable functional groups.

[0057] The cross-linking bond between the cross-linkable functional groups may be a urethane cross-linking bond, an ester cross-linking bond, a hydrogen bond, a bond formed by a radical polymerization reaction of a vinyl group at the end of an allyl group (-CH-CH=CH), or the like, but is not limited to these examples.

[0058] Furthermore, when a crosslinking agent is added in the process of producing the composite solid electrolyte, a crosslinking bond may be formed between the crosslinking agent and the crosslinkable functional group, and the crosslinking bond may be a hydrogen bond, a bond due to Lewis acid-base interaction, an ionic bond, a coordinate bond, or a bond formed by radical polymerization.

[0059] The crosslinking agent is not particularly limited as long as it can form a crosslink with the crosslinkable functional group. For example, the crosslinking agent may be trimethylolpropane trimethacrylate, polyethylene glycol diacrylate (poly(ethylene glycol) diacrylate), polyethylene glycol dimethacrylate (poly(ethylene glycol) dimethacrylate), ethylene glycol dimethylacrylate (hereinafter referred to as "EGDMA"), 1,3-diisopropenylbenzene (DIP), 1,4-diacryloyl piperazine, 2-(diethylamino)ethyl methacrylate, 2,6-bisacryloylamidopyridine, 3-(acryloxy)-2-hydroxypropyl methacrylate, 3,5-bis(acrylamido)benzoic acid (3,5-bis(acrylamido)benzoic acid, 3-aminopropyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-methylacryloxypropyltrimethoxysilane, bis-(1-(tert-butylperoxy)-1-methylethyl)-benzene, dicumyl peroxide, dimethacrylate, divinylbenzene, ethylene glycol maleic rosinate acrylate, glycidylmethacrylate, hydroxyquinoline, i-phenyldiethoxysilane silane), 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.

[0060] The crosslinking agent may be included in an amount of 1 to 30 parts by weight based on 100 parts by weight of the PEO copolymer having a crosslinkable functional group. If the content of the crosslinking agent is less than 1 part by weight, crosslinking with the crosslinkable functional group may not be sufficient, while if the content is more than 30 parts by weight, crosslinking may be excessive, which may reduce the mobility of the polymer chain and thereby reduce ion conductivity.

[0061] In one embodiment of the present invention, the composite solid electrolyte may further include a lithium salt. The lithium salt may be present in the internal space between the polymer chains in a dissociated ionic state, thereby improving the ionic conductivity of the composite solid electrolyte. At least a portion of the cations and / or anions dissociated from the lithium salt may be present in a state bound to the polymer chains, thereby exhibiting mobility during charge / discharge of the battery.

[0062] The lithium salts include (CF3SO2)2NLi (Lithium bis(trifluoromethanesulphonyl)imide, LiTFSI), (FSO2)2NLi (Lithium bis(fluorosulfonyl)imide, LiFSI), LiNO3, LiOH, LiCl, LiBr, LiI, LiClO4, LiBF4, and LiB 10 Cl 10, LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiSCN, LiC(CF3SO2)3, lithium chloroborane, lithium lower aliphatic carboxylate, and lithium tetraphenylborate.

[0063] The lithium salt may be contained in an amount of 25 to 45 parts by weight relative to 100 parts by weight of the PEO-based copolymer having a cross-linkable functional group, specifically, 25 parts by weight or more, 30 parts by weight or more, or 35 parts by weight or more, or 40 parts by weight or less, or 45 parts by weight or less. If the content of the lithium salt is less than 25 parts by weight, the ionic conductivity of the composite solid electrolyte may decrease, and if it exceeds 45 parts by weight, the mechanical strength may decrease.

[0064] In one embodiment of the present invention, the composite solid electrolyte may include a ceramic compound having lithium ion transport ability for improving lithium ion conductivity, preferably containing lithium atoms and capable of transporting lithium ions without storing lithium, thereby improving the ionic conductivity of the composite solid electrolyte.

[0065] In addition, the ceramic compound may be included in a state of being uniformly dispersed among the cross-linked polymer chains, for example, within the three-dimensional network structure. The ceramic compound may be added during the cross-linking process and be uniformly dispersed without clumps 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.

[0066] The ceramic compound may also be in the form of particles. Due to its morphological characteristics as particles, it may be contained in a more uniformly dispersed state within the composite solid electrolyte. The ceramic compound particles may be spherical, and their diameter may be 100 nm to 1000 nm. If the diameter is less than 100 nm, the amorphization effect due to reduced crystallinity of the polymer is minimal, while if the diameter is more than 1000 nm, the dispersibility may be reduced due to increased aggregation between particles, making it difficult to disperse uniformly.

[0067] The ceramic compound may be an oxide-based or phosphate-based compound, and may be an oxide-based solid electrolyte in the form of, for example, lithium metal oxide or lithium metal phosphate. More specifically, the ceramic compound may be a garnet-type lithium-lanthanum-zirconium oxide (LLZO, Li7La3Zr2O 12 ) compounds, perovskite-type lithium-lanthanum-titanium oxides (LLTO, Li3xLa 2 / 3-x TiO3) compounds, phosphate-based NASICON-type lithium-aluminum-titanium phosphate (LATP, Li 1+x Al x Ti 2-x (PO4)3) compounds, lithium-aluminum-germanium phosphate system (LAGP, Li 1.5 Al 0.5 Ge 1.5The solid electrolyte may be one or more selected from the group consisting of lithium-lanthanum-zirconium-titanium oxide (LLZTO) compounds, lithium-silicon-titanium phosphate (LSTP, LiSiOTiO(PO)) compounds, and lithium-lanthanum-zirconium-titanium oxide (LLZTO) compounds. More preferably, one or more oxide-based solid electrolytes selected from the group consisting of lithium-lanthanum-zirconium oxide (LLZO), lithium-silicon-titanium phosphate (LSTP), lithium-lanthanum-titanium oxide (LLTO), lithium-aluminum-titanium phosphate (LATP), lithium-aluminum-germanium phosphate (LAGP), and lithium-lanthanum-zirconium-titanium oxide (LLZTO) can be used.

[0068] The oxide-based or phosphate-based oxide-based solid electrolyte generally has a maximum resistance of 10 -4 ~10 -3 It has an ionic conductivity of 100 S / cm, is stable in the high voltage range, is stable in air, and has the advantages of being easy to synthesize and handle.

[0069] In addition, the ceramic compound has high high-temperature stability because it does not easily burn or ignite even at high temperatures of 400° C. or higher. Therefore, when the composite solid electrolyte contains the ceramic compound, it is possible to improve the mechanical strength of the composite solid electrolyte as well as its high-temperature stability and ionic conductivity.

[0070] The ceramic compound may be contained in an amount of 10 to 100 parts by weight, or 10 to 60 parts by weight, relative to 100 parts by weight of the PEO copolymer containing a cross-linkable functional group.

[0071] 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.

[0072] If the ceramic compound is contained in an excessively large amount, the ceramic compound may not be uniformly dispersed in the polymer, and the ceramic compound particles may aggregate and clump together, resulting in a composite solid electrolyte with reduced ionic conductivity.

[0073] Method for manufacturing composite solid electrolyte A method for manufacturing a composite solid electrolyte according to another embodiment of the present invention may include forming a mixture of a PEO (polyethylene oxide)-based copolymer having a cross-linkable functional group and a ceramic compound; and performing a cross-linking reaction on the PEO-based copolymer contained in the mixture.

[0074] In this production method, the PEO copolymer containing the cross-linkable functional group has already been described above, so further explanation will be omitted.

[0075] In one embodiment of the invention, the cross-linking reaction step may be carried out in the presence of at least one additive selected from the group consisting of a cross-linking agent and an initiator.

[0076] Also, a lithium salt may be added during the mixing step or the cross-linking reaction step.

[0077] Furthermore, the ceramic compound may be the same as that used in the composite solid electrolyte described above, and the content may also be the same.

[0078] The cross-linking can be formed during the drying process after a mixed solution containing a polymer including the PEO copolymer and a ceramic compound is applied to a substrate to form a coating film.

[0079] Specifically, the mixed solution can be prepared by mixing the PEO-based copolymer and the ceramic compound in a solvent, and may additionally be prepared by mixing a crosslinker, an initiator, and / or a lithium salt together.

[0080] The solvent is not particularly limited as long as it can be mixed with the PEO-based 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).

[0081] The concentration of the mixed solution can be appropriately adjusted taking into consideration the degree to which the molding process for producing the composite solid electrolyte can proceed smoothly. Specifically, the concentration of the mixed solution may refer to the concentration (w / w%) of the PEO-based copolymer in the mixed solution. For example, the concentration of the mixed solution may be 5% to 20%, specifically, 5% or more, 7% or more, or 9% or more, or 13%, 17% or less, or 20% or less. If the concentration of the mixed solution is less than 5%, the concentration may be excessively diluted, resulting in a decrease in the mechanical strength of the composite solid electrolyte or in the possibility of it running off when applied to a substrate. If the concentration is more than 20%, it may be difficult to dissolve the lithium salt in the mixed solution to the desired concentration, resulting in a high viscosity that reduces solubility, or making it difficult to apply the solution in the form of a uniform thin film.

[0082] 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 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.

[0083] The coating method is not particularly limited as long as it can coat the mixed solution on the substrate to form a coating film, 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.

[0084] The coating film formed on the substrate by such a coating method can be formed into a solid electrolyte membrane from which the residual solvent has been completely removed by a drying process. The drying process can be divided into a primary drying process and a secondary drying process to prevent shrinkage of the film due to rapid evaporation of the solvent. The primary drying process can remove a portion of the solvent by drying at room temperature, and the secondary drying process can completely remove the solvent by high-temperature drying in a vacuum. The high-temperature drying can be performed at a temperature of 80°C to 130°C. If the high-temperature drying temperature is less than 80°C, the residual solvent cannot be completely removed, and if it exceeds 130°C, the film will shrink, making it difficult to form a uniform electrolyte membrane.

[0085] 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.

[0086] Furthermore, the initiator induces a radical polymerization reaction between the cross-linking functional groups to form cross-links between the cross-linking functional groups. The functional group that enables the radical polymerization reaction may be a functional group containing vinyl at its terminal, or may be, for example, an allyl group.

[0087] 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, paramethane hydroperoxide, and 2,2'-azobis(2-methylpropionitrile).

[0088] The initiator can be used in an amount of 0.5 to 2 parts by weight per 100 parts by weight of the PEO copolymer containing cross-linking functional groups, and when used in this range, it can induce a radical polymerization reaction between the cross-linking functional groups to efficiently form cross-links.

[0089] The content and type of the lithium salt are as described above.

[0090] By the above-described manufacturing method, a composite solid electrolyte according to one embodiment can be manufactured in which the ceramic compound is uniformly dispersed among the cross-linked polymer chains.

[0091] all solid state battery An additional embodiment of the invention also relates to an all-solid-state battery including an electrolyte layer comprising the composite solid electrolyte, the all-solid-state battery including an anode, a cathode, and a composite solid electrolyte interposed between the anode and the cathode, wherein the composite solid electrolyte is according to one of the embodiments described above.

[0092] 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 ceramic compound. The ceramic compound is uniformly dispersed within the three-dimensional network structure of the polymer, improving ionic conductivity, making it suitable as an electrolyte for all-solid-state batteries.

[0093] 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.

[0094] The positive electrode active material layer includes a positive electrode active material, a binder, and a conductive material.

[0095] The positive electrode active material is not particularly limited as long as it is a material capable of reversibly absorbing and releasing lithium ions, and examples thereof include lithium cobalt oxide, lithium nickel oxide, Li[NixCoyMnzMv]O2 (wherein M is any one or more elements selected from the group consisting of Al, Ga, and In; 0.3≦x<1.0, 0≦y, z≦0.5, 0≦v≦0.1, and x+y+z+v=1), Li(LiaMb-a-b'M'b')O 2-c A c (wherein 0≦a≦0.2, 0.6≦b≦1, 0≦b'≦0.2, 0≦c≦0.2; M comprises Mn and one or more elements selected from the group consisting of Ni, Co, Fe, Cr, V, Cu, Zn, and Ti; M' is one or more elements selected from the group consisting of Al, Mg, and B; and A is one or more elements selected from the group consisting of P, F, S, and N); layered compounds and compounds substituted with one or more transition metals, such as those represented by the formula Li 1+y Mn 2-y Lithium manganese oxides such as LiMnO4 (where y is 0 to 0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, and Cu2V2O7; and the chemical formula LiNi 1-yNi-site lithium nickel oxide represented by MyO2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and y = 0.01 to 0.3); chemical formula LiMn 2-y M y Examples of suitable lithium manganese composite oxides include, but are not limited to, lithium manganese composite oxides expressed as Li2Mn3MO8 (where M is Co, Ni, Fe, Cr, Zn, or Ta, and y is 0.01 to 0.1) or Li2Mn3MO8 (where M is Fe, Co, Ni, Cu, or Zn); LiMn2O4, in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion; disulfide compounds; and Fe2(MoO4)3.

[0096] The positive electrode active material may be included in an amount of 40 to 80 wt % based on the total weight of the positive electrode active material layer. Specifically, the content of the positive electrode active material may be 40 wt % or more, or 50 wt % or more, or 70 wt % or less, or 80 wt % or less. If the content of the positive electrode active material is less than 40 wt %, the connectivity between the positive electrode active materials and the electrical properties may be insufficient, and if it exceeds 80 wt %, the mass transfer resistance may be high.

[0097] Furthermore, the binder is a component that assists in binding the positive electrode active material to the conductive material and the current collector, and is selected from the group consisting of styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile The binder may include at least one selected from the group consisting of styrene-butadiene rubber, polytetrafluoroethylene, carboxymethyl cellulose, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene. Preferably, the binder may include at least one selected from the group consisting of styrene-butadiene rubber, polytetrafluoroethylene, carboxymethyl cellulose, polyacrylic acid, lithium polyacrylate, and polyvinylidene fluoride.

[0098] The binder may be included in an amount of 1 wt % to 30 wt % based on the total weight of the positive electrode active material layer. Specifically, the binder content may be 1 wt % or more, or 3 wt % or more, or 15 wt % or less, or 30 wt % or less. If the binder content is less than 1 wt %, the adhesive strength between the positive electrode active material and the positive electrode current collector may be reduced. If the binder content exceeds 30 wt %, the adhesive strength is improved, but the content of the positive electrode active material may be reduced accordingly, resulting in a reduced battery capacity.

[0099] Furthermore, the conductive material is not particularly limited as long as it prevents side reactions in the internal environment of the all-solid-state battery, has excellent electrical conductivity without inducing chemical changes in the battery, and typically includes graphite or conductive carbon. Examples of the conductive material include graphite such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, denka black, thermal black, channel black, furnace black, and lamp black; carbon-based materials having a graphene or graphite crystal structure; conductive fibers such as carbon fibers and metal fibers; carbon fluoride; metal powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives. These may be used alone or in combination, but are not necessarily limited thereto.

[0100] The conductive material may typically be included in an amount of 0.5 wt % to 30 wt % based on the total weight of the positive electrode active material layer. Specifically, the content of the conductive material may be 0.5 wt % or more, or 1 wt % or more, or 20 wt % or less, or 30 wt % or less. If the content of the conductive material is too low, such as less than 0.5 wt %, it may be difficult to expect an improvement in electrical conductivity or the electrochemical characteristics of the battery may be deteriorated. If the content of the conductive material is too high, such as more than 30 wt %, the amount of positive electrode active material may be relatively reduced, resulting in reduced capacity and energy density. The method for incorporating the conductive material into the positive electrode is not particularly limited, and conventional methods known in the art, such as coating the positive electrode active material, may be used.

[0101] 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.

[0102] The positive electrode current collector is not particularly limited as long as it has high electronic conductivity without inducing chemical changes in the all-solid-state battery, and examples of the positive electrode current collector include copper, stainless steel, aluminum, nickel, titanium, palladium, baked carbon, copper or stainless steel surface-treated with carbon, nickel, silver, or the like, and aluminum-cadmium alloys.

[0103] The positive electrode current collector may have a micro-irregular structure or a three-dimensional porous structure on its surface to strengthen the bonding strength with the positive electrode active material layer, and may include various forms such as a film, sheet, foil, mesh, net, porous body, foam, or nonwoven fabric.

[0104] Such a positive electrode can be manufactured by a conventional method. Specifically, a positive electrode active material, a conductive material, and a binder are mixed in an organic solvent to form a positive electrode active material layer. The resulting composition is then applied to a positive electrode current collector, dried, and optionally, compressed into a current collector to improve electrode density. Preferably, the organic solvent used is one that can uniformly disperse the positive electrode active material, binder, and conductive material and is easily evaporated. Specific examples include acetonitrile, methanol, ethanol, tetrahydrofuran, water, isopropyl alcohol, dimethyl sulfoxide (DMSO), and N-methyl-2-pyrrolidone (NMP).

[0105] 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.

[0106] 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.

[0107] 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).

[0108] Preferably, the negative electrode active material may be lithium metal, specifically in the form of a lithium metal thin film or lithium metal powder.

[0109] 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.

[0110] The binder is the same as that described above in the positive electrode active material layer.

[0111] Furthermore, the conductive material is as described above in the positive electrode active material layer.

[0112] The negative electrode current collector is not particularly limited as long as it is conductive and does not induce chemical changes in the battery, and examples of the negative electrode current collector that can be used include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. Furthermore, similar to the positive electrode current collector, the negative electrode current collector can be in various forms such as a film, sheet, foil, net, porous material, foam, nonwoven fabric, etc., with fine irregularities formed on the surface.

[0113] The method for manufacturing the negative electrode is not particularly limited, and the negative electrode may be manufactured by forming a negative electrode active material layer on a negative electrode current collector using a layer or film formation method commonly used in the art, such as compression bonding, coating, deposition, etc. Furthermore, the negative electrode of the present invention also includes a case where a thin metallic lithium film is formed on a metal plate by initial charging after a battery is assembled without a thin lithium film on the negative electrode current collector.

[0114] 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.

[0115] Specific examples of the device include, but are not limited to, power tools powered by a battery-powered motor; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters; electric golf carts; and power storage systems.

[0116] Preferred examples will be presented below to aid in understanding the invention. However, the following examples are provided merely to facilitate understanding of the invention, and the invention is not limited thereto.

[0117] Example Example 1: Preparation of composite solid electrolyte A polyethylene oxide (PEO)-based copolymer of the following formula 1a was prepared:

[0118] [ka]

[0119] In the above chemical formula 1a, R1 is -CH2-O-(CH2-CH2-O) k R2 is -CH2-O-CH2-CH=CH2, k is 2, the ratio of l:m:n is 85:13:2, and the weight average molecular weight (Mw) of the copolymer is about 2,000,000 g / mol.

[0120] The copolymer of formula 1a has an allyl group as a cross-linking functional group linked via a methylene oxide linker.

[0121] 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 polyethylene oxide copolymer and ceramic compound, which was then stirred for 24 hours using a magnetic bar. The mixed solution of polyethylene oxide copolymer and ceramic compound was prepared by mixing 100 parts by weight of 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, so that the concentration of the polymer polyethylene oxide copolymer in the mixed solution of polymer and ceramic compound was 11.1 wt% and the concentrations of the polyethylene oxide and ceramic compound were 14.9 wt% in acetonitrile as a solvent.

[0122] The prepared mixed solution was solution-cast on the lower substrate of a coin cell, and then primarily dried at room temperature for 12 hours, and then secondary dried at 100°C for 3 hours to form an electrolyte film with a thickness of 200 μm, thereby preparing a composite solid electrolyte.

[0123] Comparative Example: Comparative Example 1: Polymer solid electrolyte containing only modified PEO (no ceramic compound) A polymer solid electrolyte was prepared in the same manner as in Example 1, except that no ceramic compound was used.

[0124] Comparative Example 2: Composite solid electrolyte containing unmodified PEO and ceramic compound A composite solid electrolyte was prepared in the same manner as in Example 1, except that a PEO homopolymer (Sigma-Aldrich, molecular weight (Mw): 4,000,000 g / mol) without a substituted crosslinking functional group was used, and a crosslinking agent and initiator were not added.

[0125] Comparative Example 3: Polymer solid electrolyte containing unmodified PEO (no ceramic compound) A polymer solid electrolyte was prepared in the same manner as in Example 1, except that a ceramic compound was not used, a PEO homopolymer (Sigma-Aldrich, molecular weight (Mw): 4,000,000 g / mol) without a substituted crosslinking functional group was used, and a crosslinker and initiator were not added. The PEO copolymer and the lithium salt LiTFSI were added to the solvent acetonitrile at a molar ratio of 20:1 to prepare a mixed solution. The concentration of the PEO copolymer in the mixed solution was 3% (w / w%).

[0126] Experimental Example Experimental Example 1: Measurement of ionic conductivity of solid electrolyte To measure the ionic conductivity of the solid electrolytes prepared in the examples and comparative examples, a 1.7671 cm 2 The solid electrolyte was formed on the lower substrate of a coin cell of the same size, and then SUS was used as a blocking electrode to prepare a coin cell for measuring ionic conductivity.

[0127] Resistance was measured using an electrochemical impedance spectrometer (EIS, VM3, Bio Logic Science Instrument) at 25°C with an amplitude of 10 mV and a scan range of 1 Hz to 0.1 MHz, and the ionic conductivity of the solid electrolyte was calculated using the following Equation 1:

[0128]

number

[0129] In the above formula 1, σ iis the ionic conductivity (S / cm) of the solid electrolyte, R is the resistance (Ω) of the solid electrolyte measured by the electrochemical impedance spectrometer, L is the thickness (μm) of the solid electrolyte, and A is the area (cm 2 ) means

[0130] Table 1 below shows the calculated ionic conductivity values.

[0131] [Table 1]

[0132] As shown in Table 1, Example 1, which is a composite solid electrolyte prepared using PEO containing cross-linkable functional groups and a ceramic compound, had the highest ionic conductivity.

Claims

1. A polymer including a PEO (polyethylene oxide)-based copolymer containing a cross-linkable functional group; and a ceramic 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; The ceramic compound is a composite solid electrolyte contained within the three-dimensional network structure.

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

3. The composite solid electrolyte according to claim 2 , wherein at least a portion of the cross-linkable functional groups form cross-links with each other via the cross-linking agent.

4. the cross-linkable functional group is bonded to the PEO-based copolymer via an alkylene linker or alkylene oxide linker having 0 to 10 carbon atoms (wherein an alkylene linker having 0 carbon atoms represents a single bond); 2. The 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.

5. 10. The composite solid electrolyte according to claim 1, further comprising a lithium salt dispersed on the polymer forming the three-dimensional network structure.

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

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

8. 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.

9. forming a mixture of a PEO (polyethylene oxide) copolymer containing cross-linkable functional groups and a ceramic compound; and The method for producing a composite solid electrolyte according to claim 1 , further comprising the step of causing a cross-linking reaction of the PEO-based copolymer contained in the mixture.

10. 10. The method for preparing a composite solid electrolyte according to claim 9, wherein the cross-linking reaction step is carried out in the additional presence of one or more additives selected from the group consisting of a cross-linking agent and an initiator.

11. An all-solid-state battery comprising an electrolyte layer comprising the composite solid electrolyte according to any one of claims 1 to 8.

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