Composite solid electrolytes and all-solid-state batteries containing them

Abstract

The present invention relates to a composite solid electrolyte and an all-solid-state battery containing the same. The composite solid electrolyte comprises a polymer containing a non-crosslinked PEO (polyethylene oxide) copolymer having a branched structure of a predetermined structure; a lithium salt; and a ceramic compound, wherein the lithium salt and the ceramic compound may have a structure in which they are dispersed on the polymer.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority under Korean Patent Application No. 10-2024-0048815 dated April 11, 2024, and all content disclosed in the said Korean Patent Application is incorporated herein as part of this specification.

[0002] This invention relates to a composite solid electrolyte and an all-solid-state battery containing the same. [Background technology]

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

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

[0005] Among solid electrolytes, polymer solid electrolytes can use polymer materials that are ion-conducting, and can be used in the form of composite solid electrolytes in which inorganic materials are mixed with such polymer materials.

[0006] Conventional hybrid (composite) solid electrolytes are manufactured by dispersing inorganic powders such as oxide ceramics in a polymer matrix. While they have advantages such as higher ignition and combustion stability compared to existing liquid electrolytes and higher ionic conductivity compared to polymer solid electrolytes, they face difficulties in meeting fundamental prerequisites, such as improving the dispersibility of oxide ceramic particles within the polymer matrix and optimizing the physical properties of the polymer matrix used. In particular, when polymers containing highly crystalline units, such as polyethylene oxide (PEO) or polypropylene oxide (PPO), are used as the matrix, it is difficult to manufacture composite solid electrolytes with improved ionic conductivity. That is, the high crystallinity of PEO and PPO polymers inhibits the chain mobility of the polymer chains, reducing the dispersibility of the oxide ceramics, and also restricts the movement of lithium ions within the composite solid electrolyte, thus limiting the improvement of the ionic conductivity of the composite solid electrolyte. Furthermore, when additional plasticizers or dispersants are used to improve the dispersibility of the ceramics, this can lead to a decrease in electrochemical properties and other limitations, such as increased process complexity.

[0007] In particular, it was considered difficult to ensure an ionic conductivity of 0.1 mS / cm or higher at room temperature when applying conventional composite solid electrolyte manufacturing technologies.

[0008] Furthermore, when using a (block) copolymer containing polypropylene oxide (PPO) units as the polymer matrix, the overall electrolyte manufacturing process becomes complex, and process problems arise, such as difficulty in controlling the thickness of the solid electrolyte membrane, because such a polymer matrix is ​​prepared in the gas phase and a composite solid electrolyte is formed by a gas-phase / liquid-phase reaction. In addition, the PPO-based polymer matrix has a high shrinkage rate during molding, is prone to aging, and has poor impact resistance at low temperatures, so the composite solid electrolyte manufactured using it may have insufficient physical properties. [Overview of the project] [Problems that the invention aims to solve]

[0009] The present invention provides a composite solid electrolyte that can be manufactured through a simple process and exhibits improved ionic conductivity by more uniformly dispersing ceramic compounds and lithium salts on a polymer.

[0010] Furthermore, the present invention provides an all-solid-state battery containing a composite solid electrolyte with improved ionic conductivity. [Means for solving the problem]

[0011] According to one embodiment of the invention, a composite solid electrolyte is provided comprising a polymer containing a non-crosslinked PEO (polyethylene oxide) copolymer having a branched structure containing repeating units of the following chemical formulas 1 and 2; a lithium salt; and a ceramic compound, wherein the lithium salt and the ceramic compound are dispersed on the polymer, and the ceramic compound is included in an amount of 10 to 45 parts by weight per 100 parts by weight of the polymer: [ka] [ka]

[0012] In the above chemical formulas 1 and 2, R1 is -CH2-O-(CH2-CH2-O) k -R3 is represented, k is 0 to 20, and R3 represents an alkyl group with 1 to 5 carbon atoms. l and m are the number of repetitions in the repeating unit, and are independent integers between 1 and 100,000.

[0013] In the composite solid electrolyte of the above embodiment, the ceramic compound can include an oxide-based solid electrolyte of a lithium metal oxide or a lithium metal phosphate. More specifically, it can include one or more oxide-based solid electrolytes selected from the group consisting of lithium-lanthanum-zirconium oxide-based (LLZO) compounds, lithium-silicon-titanium phosphate-based (LSTP) compounds, lithium-lanthanum-titanium oxide-based (LLTO) compounds, lithium-aluminum-titanium phosphate-based (LATP) compounds, lithium-aluminum-germanium phosphate-based (LAGP) compounds, and lithium-lanthanum-zirconium-titanium oxide-based (LLZTO) compounds.

[0014] In the composite solid electrolyte, the lithium salt may be contained in a content of 10 to 40 parts by weight with respect to 100 parts by weight of the polymer.

[0015] The above-described composite solid electrolyte can be provided in a dry film state that does not contain a liquid.

[0016] According to another embodiment of the invention, a method for manufacturing the composite solid electrolyte is provided. Such a manufacturing method can include a step of forming a mixed solution including a polymer including a branched structure including the repeating units of Chemical Formulas 1 and 2, a non-crosslinked PEO (polyethylene oxide)-based copolymer, a lithium salt, and a ceramic compound, and a step of casting and drying the mixed solution to form a film.

[0017] According to an additional embodiment of the invention, a all-solid-state battery including an electrolyte layer including the composite solid electrolyte of the above embodiment is provided. Such an all-solid-state battery can include a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and an electrolyte layer interposed between the positive electrode and the negative electrode and including the composite solid electrolyte.

Effects of the Invention

[0018] The composite solid electrolyte according to the present invention allows for the uniform distribution of ceramic compounds and lithium salts in a fixed amount within a non-crosslinked PEO-based polymer matrix having a branched structure, without aggregation between components or particle aggregation. As a result, improved ionic conductivity can be achieved by uniformly dispersing the ceramic compounds and other elements while reducing the influence of the crystalline properties of the linear polymer.

[0019] Additionally, due to the excellent dispersibility of the polymer matrix, the composite solid electrolyte can be manufactured in a simplified process of mixing the components to produce a liquid state and then casting it into a film state, exhibiting excellent processability and mass productivity. [Modes for carrying out the invention]

[0020] The embodiments of the invention will be described in more detail below to help you understand the invention.

[0021] Terms and words used herein and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner and concept consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may appropriately define the concepts of terms in order to best describe their invention.

[0022] Conventionally, to improve the ionic conductivity of solid electrolytes, composite solid electrolytes were manufactured by mixing ceramic compounds such as oxides or lithium salts with a polymer matrix having a cross-linked structure. However, such composite solid electrolytes had problems such as the non-uniform distribution of oxide-based ceramic particles within the polymer matrix, and when polymers containing highly crystalline units such as polyethylene oxide or polypropylene oxide were used as the polymer, the dispersibility of the ceramic compounds and the ionic conductivity decreased. In particular, the aggregation of particles such as the ceramic compounds limited the ability to uniformly improve ionic conductivity.

[0023] Therefore, the inventors have produced a composite solid electrolyte containing a polymer in which the ceramic compound and other elements are uniformly dispersed between polymer chains by mixing a PEO (polyethylene oxide) copolymer having a branched and non-crosslinked structure containing specific units with a ceramic compound and a lithium salt, followed by film formation and drying.

[0024] In particular, the polymer matrix exhibits excellent dispersibility with ceramic compounds and the like, and as a result, it becomes possible to manufacture composite solid electrolytes exhibiting excellent ionic conductivity and other properties through a simple process without the need for separate plasticizers or dispersants.

[0025] Therefore, according to one embodiment of the invention, the invention is completed by confirming that a composite solid electrolyte exhibiting improved ionic conductivity compared to existing composite solid electrolytes can be manufactured and provided in a simplified process.

[0026] The composite solid electrolyte of the above embodiment will be described in detail below.

[0027] Composite solid electrolyte A composite solid electrolyte according to one embodiment of the invention comprises a polymer containing a non-crosslinked PEO (polyethylene oxide) copolymer having a predetermined branched structure; a lithium salt; and a ceramic compound, wherein the lithium salt and the ceramic compound are dispersed on the polymer.

[0028] In such a composite solid electrolyte, the non-crosslinked PEO copolymer having the branched structure does not have crosslinkable functional groups, and at least some of the PEO repeating units have branched chains containing repeating alkylene oxide structures. Such branched chain structures include, for example, -CH2-O-(CH2-CH2-O) k-R3 may be defined as (k is 0 to 20, and R3 is an alkyl group having 1 to 5 carbon atoms), and such branched chains can be bonded to the main chain of some of the PEO repeating units. In more specific examples, the branched, non-crosslinked PEO copolymer may not contain additional polymer units such as polypropylene oxide (PPO) units.

[0029] In the copolymer structure, the branched chains may act as substituents that function as a type of plasticizer. Therefore, a uniform dispersion of ceramic compounds and the like can be induced on the polymer containing the copolymer. As a result, the composite solid electrolyte of one embodiment can exhibit excellent ionic conductivity even with relatively small amounts of ceramic compounds, without the use of additional additives such as separate plasticizers or dispersants. Furthermore, since the copolymer does not contain additional polymer units such as PPO-based polymers, the physical properties of the composite solid electrolyte, such as impact resistance, can be maintained at an excellent level.

[0030] In a more specific embodiment, the non-crosslinked PEO copolymer having the branched structure may be a copolymer containing repeating units of the following chemical formulas 1 and 2: [ka] [ka]

[0031] In the above chemical formulas 1 and 2, R1 is -CH2-O-(CH2-CH2-O) k -R3 is represented, k is 0 to 20, and R3 represents an alkyl group with 1 to 5 carbon atoms. l and m are the number of repetitions in the repeating unit, and are independent integers ranging from 1 to 100,000, 50 to 80,000, or 100 to 50,000, respectively.

[0032] For example, the branched chain of R1, as described above, can induce a uniform dispersion of ceramic compounds and the like, thereby causing the composite solid electrolyte of one embodiment to exhibit improved ionic conductivity.

[0033] In the copolymer, if l and m are excessively small, forming a polymer is difficult due to the low molecular weight, and in particular, if the repeating units of chemical formula 2 are not included, the ionic conductivity of the composite solid electrolyte of one embodiment may be low. If l and m are excessively large, the increased viscosity reduces solubility during the production of the polymer solution, making molding for the production of the solid electrolyte difficult.

[0034] The weight-average molecular weight (Mw) of the copolymer containing chemical formulas 1 and 2 may be between 100,000 g / mol and 4,000,000 g / mol, and more specifically, it may be 100,000 g / mol or more, 200,000 g / mol or more, or 300,000 g / mol or more, and may be 3,000,000 g / mol or less, or 2,000,000 g / mol or less. If the weight-average molecular weight (Mw) of the copolymer is excessively small, the mechanical properties of the solid electrolyte produced may not be satisfied. If the weight-average molecular weight (Mw) of the copolymer is excessively large, the viscosity may increase, reducing solubility during the production of the polymer solution, which may make molding for solid electrolyte production difficult. In addition, the ionic conductivity of the composite solid electrolyte may decrease due to increased crystallinity and decreased chain mobility within the solid electrolyte.

[0035] Furthermore, the copolymer may be a random copolymer or a block copolymer.

[0036] In one embodiment of the invention, the composite solid electrolyte may further contain a lithium salt. The lithium salt is contained 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 some of the cations and / or anions dissociated by the lithium salt remain bound to the polymer chains and can exhibit mobility during charging and discharging of the battery.

[0037] The lithium salts mentioned above are (CF3SO2)2NLi (Lithium bis(trifluoromethanesulfonyyl)imide, LiTFSI), (FSO2)2NLi (Lithium bis(fluorosulfonyl)imide, LiFSI), LiNO3, LiOH, LiCl, LiBr, LiI, LiClO4, LiBF4, and LiB 10 Cl 10 It may contain one or more selected from the group consisting of LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiSCN, LiC(CF3SO2)3, lithium chloroborane, lithium lower aliphatic carboxylate, and lithium tetraphenylborate.

[0038] Furthermore, the lithium salt may be present in 10 to 40 parts by weight per 100 parts by weight of the branched and non-crosslinked PEO copolymer, specifically, 15 parts by weight or more, or 20 parts by weight or more, or 40 parts by weight or less, or 38 parts by weight or less. If the lithium salt content is less than 10 parts by weight, the ionic conductivity of the composite solid electrolyte may decrease, and if it exceeds 40 parts by weight, the mechanical strength may decrease.

[0039] In one embodiment of the invention, the composite solid electrolyte may include a ceramic compound. The ceramic compound has lithium ion transfer capability to improve lithium ion conductivity, and preferably contains lithium atoms and has the function of moving lithium ions without storing lithium, thereby improving the ionic conductivity of the composite solid electrolyte.

[0040] Furthermore, the ceramic compound may be included in a state uniformly dispersed on the non-crosslinked and branched polymers. The ceramic compound can be uniformly dispersed without clumping between polymer chains due to the branched chain structure of the polymer. Such a ceramic compound may be advantageous in improving the mechanical strength and ionic conductivity of the composite solid electrolyte due to its uniform dispersion form.

[0041] Furthermore, the ceramic compound may be in the form of particles. Due to its morphological characteristics as particles, it is possible for it to be included in a more uniformly dispersed state within the composite solid electrolyte. The particles of the ceramic compound may be spherical, and their diameter may be between 100 nm and 1000 nm. If the diameter is less than 100 nm, the non-crystallization effect due to the decrease in the crystallinity of the polymer is slight, and if it exceeds 1000 nm, the dispersibility may decrease due to increased aggregation between particles, making uniform dispersion difficult.

[0042] The ceramic chemical may be an oxide-based or phosphate-based compound, or it may be an oxide-based solid electrolyte in the form of, for example, lithium metal oxide or lithium metal phosphorus oxide. However, considering the appropriate dispersibility of the ceramic compound and the excellent ionic conductivity of the solid electrolyte, the oxide-based solid electrolyte in the form of lithium metal phosphorus oxide is more appropriately usable.

[0043] More specifically, the ceramic compound is a garnet-type lithium-lanthanum-zirconium oxide system (LLZO, Li7La3Zr2O 12) Compounds, perovskite-type lithium-lanthanum-titanium oxide-based (LLTO, Li3xLa 2 / 3-x TiO3) compounds, phosphate-based NASICON-type lithium-aluminum-titanium phosphate-based (LATP, Li 1+x Al x Ti 2-x (PO4)3) compounds, lithium-aluminum-germanium phosphate-based (LAGP, Li 1.5 Al 0.5 Ge 1.5 (PO4)3) compounds, lithium-silicon-titanium phosphate-based (LSTP, LiSiO2TiO2(PO4)3) compounds, and lithium-lanthanum-zirconium-titanium oxide-based (LLZTO) compounds, and one or more can be selected from the group consisting of; 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. Among these, one or more selected from the group consisting of the lithium-silicon-titanium phosphate-based (LSTP) compounds, lithium-aluminum-titanium phosphate-based (LATP) compounds, and lithium-aluminum-germanium phosphate-based (LAGP) compounds having the lithium metal phosphate form can be more suitably used in terms of the ionic conductivity of the solid electrolyte and the like.

[0044] The oxide-based solid electrolyte generally has an ionic conductivity value of up to 10 -4 ~10 -3 S / cm at room temperature, is stable in a high voltage region, is stable in air, and has the advantages of being easy to synthesize and handle.

[0045] Furthermore, the ceramic compound does not easily burn or ignite even under high-temperature conditions of 400°C or higher, thus exhibiting high high-temperature stability. Therefore, when the composite solid electrolyte contains the ceramic compound, it is possible to improve not only the mechanical strength of the composite solid electrolyte but also its high-temperature stability and ionic conductivity.

[0046] The ceramic compound may be present in an amount of 10 to 45 parts by weight, or 20 to 40 parts by weight, per 100 parts by weight of the PEO copolymer containing the crosslinking functional group.

[0047] If the ceramic compound is present in an excessively small amount, the crystallinity reduction and amorphous effect of the polymer due to the ceramic compound are diminished, resulting in a less significant increase in the ionic conductivity of the composite solid electrolyte, and the mechanical properties may not reach the level expected due to composite formation.

[0048] If the ceramic compound is present in an excessively large amount, the ceramic compound will not be uniformly dispersed within the polymer, and the ceramic compound particles will aggregate and clump together, resulting in the production of a composite solid electrolyte with reduced ionic conductivity.

[0049] The composite solid electrolyte of the above-described embodiment can be provided in a dry film state that does not contain any liquid such as an organic solvent or electrolyte, and can exhibit excellent ionic conductivity in such a dry film state. As a result, the composite solid electrolyte can greatly contribute to providing an all-solid-state battery that exhibits excellent electrical properties.

[0050] Method for manufacturing composite solid electrolytes The above-described method for producing a composite solid electrolyte may include the steps of forming a mixed solution containing a polymer including a non-crosslinked PEO (polyethylene oxide) copolymer having a branched structure containing repeating units of chemical formulas 1 and 2; a lithium salt; and a ceramic compound; and casting and drying the mixed solution to form a film.

[0051] In the above manufacturing method, due to the excellent dispersibility of the copolymer, a composite solid electrolyte can be produced by a simplified method in which a polymer matrix containing the copolymer is mixed with a ceramic compound or the like to form a solution or dispersion, and then a film is formed.

[0052] In this manufacturing method, the non-crosslinked PEO copolymer having the branched structure has already been described above, so no further explanation is provided.

[0053] In one embodiment of the invention, the lithium salt and ceramic compound can be the same as those used in the composite solid electrolyte described above, and the content can also be the same.

[0054] In the aforementioned mixed solution formation step, a mixed solution containing the polymer including the PEO-based copolymer, a lithium salt, and a ceramic compound can be applied to a substrate to form a coating film. At this time, the mixed solution can be produced by mixing the PEO-based copolymer, the lithium salt, and the ceramic compound in a solvent.

[0055] The solvent is not particularly limited as long as it can dissolve the PEO copolymer and lithium salt and can be easily removed by the drying process. For example, the solvent may be acetonitrile, methanol, ethanol, tetrahydrofuran, water, isopropyl alcohol, dimethyl sulfoxide (DMSO), methylpyrrolidone (NMP), or dimethylformamide (DMF).

[0056] The concentration of the mixture can be appropriately adjusted, taking into consideration the degree to which the molding process for manufacturing the composite solid electrolyte can proceed smoothly. Specifically, the concentration of the mixture may refer to the concentration (w / w%) of the PEO copolymer in the mixture. For example, the concentration of the mixture may be 5% to 20%, and more specifically, it may be 5% or more, 7% or more, or 9% or more, or 13% or less, 17% or less, or 20% or less. If the concentration of the mixture is less than 5%, the concentration may be excessively diluted, reducing the mechanical strength of the composite solid electrolyte or causing it to flow when applied to the substrate. If it exceeds 20%, it may be difficult to dissolve the lithium salt in the mixture at the desired concentration, the viscosity may be high, reducing solubility, or it may be difficult to apply it in a uniform thin film form.

[0057] The substrate is not particularly limited as long as it serves as a support for the coating film. For example, the substrate may be SUS (Stainless Use Steel), polyethylene terephthalate film, polytetrafluoroethylene film, polyethylene film, polypropylene film, polybutene film, polybutadiene film, vinyl chloride copolymer film, polyurethane film, ethylene-vinyl acetate film, ethylene-propylene copolymer film, ethylene-ethyl acrylate copolymer film, ethylene-methyl acrylate copolymer film, or polyimide film.

[0058] Furthermore, the coating method is not particularly limited as long as it is a method that can form a coating film by applying the mixture onto the substrate. For example, the coating method may be bar coating, roll coating, spin coating, slit coating, die coating, blade coating, comma coating, slot die coating, lip coating, spray coating, or solution casting.

[0059] A coating film formed on a substrate by this coating method can be formed into a solid electrolyte film from which residual solvent is completely removed by a drying process. To prevent shrinkage of the film due to rapid evaporation of the solvent, the drying process can be divided into a primary drying process and a secondary drying process. The primary drying process can remove part of the solvent by drying at room temperature, and the secondary drying process can completely remove the solvent by high-temperature vacuum drying. The high-temperature drying can be carried out at temperatures between 80°C and 130°C. If the high-temperature drying temperature is below 80°C, the residual solvent cannot be completely removed, and if it exceeds 130°C, the film may shrink, making it difficult to form a uniform electrolyte film.

[0060] By the manufacturing method described above, a composite solid electrolyte of one embodiment can be produced in which the ceramic compound is uniformly dispersed between branched and non-crosslinked polymer chains.

[0061] All solid state battery An additional embodiment of the invention also relates to an all-solid-state battery comprising an electrolyte layer containing the composite solid electrolyte, wherein the all-solid-state battery may include a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and an electrolyte layer interposed between the positive electrode and the negative electrode, comprising the composite solid electrolyte. In this case, the electrolyte layer may include the composite solid electrolyte of the first embodiment.

[0062] Specifically, the composite solid electrolyte contains a polymer containing branched and non-crosslinked PEO (polyethylene oxide) copolymers, a lithium salt, and a ceramic compound. Since the ceramic compound and the like are uniformly dispersed on the polymer, improving ionic conductivity, it may be suitable as an electrolyte for an all-solid-state battery.

[0063] On the other hand, the positive electrode included in the all-solid-state battery may include a positive electrode active material layer, and the positive electrode active material layer may be formed on at least one surface of the positive electrode current collector.

[0064] The positive electrode active material layer comprises a positive electrode active material, a binder, and a conductive material.

[0065] Furthermore, the positive electrode active material is not particularly limited as long as it is a material capable of reversibly intercalating and releasing lithium ions, for example, lithium cobalt oxide, lithium nickel oxide, Li[NixCoyMnzMv]O2 (wherein M is one or more elements selected from the group consisting of Al, Ga, and In; 0.3≦x<1.0, 0≦y, z≦0.5, 0≦v≦0.1, x+y+z+v=1), Li(LiaMb-a-b'M'b')O2 2-c A c (In the above formula, 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 such as and compounds substituted with one or more transition metals; chemical formula Li1+y Mn 2-y Lithium manganese oxides such as O4 (where y is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-y Ni-site type lithium nickel oxide represented as MyO2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and y = 0.01 to 0.3); chemical formula LiMn 2-y M y Lithium manganese composite oxides represented as O2 (where M = Co, Ni, Fe, Cr, Zn, or Ta, and y = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu, or Zn); LiMn2O4 in which part of the Li in the chemical formula is substituted with alkaline earth metal ions; disulfide compounds; Fe2(MoO4)3, etc., are examples, but are not limited to these.

[0066] Furthermore, the positive electrode active material may be present in an amount of 40 to 80% by weight based on the total weight of the positive electrode active material layer. Specifically, the content of the positive electrode active material may be 40% or more by weight, 50% or more by weight, or 70% or less by weight, or 80% or less by weight. If the content of the positive electrode active material is less than 40% by weight, the connectivity and electrical properties between the positive electrode active materials may be insufficient, and if it exceeds 80% by weight, the mass transfer resistance may increase.

[0067] Furthermore, the binder is a component that assists in the bonding of the positive electrode active material to conductive materials and to the current collector, and includes styrene-butadiene rubber, acrylic styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile-butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonite The binder may include one or more selected from the group consisting of styrene-butadiene rubber, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethylcellulose, hydroxypropylcellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethylsucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene. Preferably, the binder may include one or more selected from the group consisting of styrene-butadiene rubber, polytetrafluoroethylene, carboxymethylcellulose, polyacrylic acid, lithium polyacrylate, and polyvinylidene fluoride.

[0068] Furthermore, the binder may be present in an amount of 1% to 30% by weight based on the total weight of the positive electrode active material layer. Specifically, the binder content may be 1% or more by weight, 3% or more by weight, 15% or less by weight, or 30% or less by weight. If the binder content is less than 1% by weight, the adhesive strength between the positive electrode active material and the positive electrode current collector may decrease. If it exceeds 30% by weight, the adhesive strength will improve, but the amount of positive electrode active material will decrease accordingly, which may reduce the battery capacity.

[0069] Furthermore, the conductive material is not particularly limited as long as it prevents side reactions in the internal environment of the all-solid-state battery and has excellent electrical conductivity without inducing chemical changes in the battery. Typically, graphite or conductive carbon can be used, for example, graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, Denka black, thermal black, channel black, furnace black, lamp black, and summer black; carbon-based materials whose crystalline structure is graphene or graphite; conductive fibers such as carbon fibers and metal fibers; carbon fluoride; metal powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives; which can be used alone or in mixtures of two or more, but are not necessarily limited to these.

[0070] The conductive material may typically be present in an amount of 0.5% to 30% by weight based on the total weight of the positive electrode active material layer. Specifically, the content of the conductive material may be 0.5% or more by weight, 1% or more by weight, 20% or less by weight, or 30% or less by weight. If the content of the conductive material is excessively low, less than 0.5% by weight, it may be difficult to expect an improvement in electrical conductivity, or the electrochemical properties of the battery may deteriorate. If it is excessively high, more than 30% by weight, the amount of positive electrode active material will be relatively small, which may reduce the capacity and energy density. The method for incorporating the conductive material into the positive electrode is not significantly limited, and conventional methods known in the art, such as coating the positive electrode active material, can be used.

[0071] Furthermore, the positive electrode current collector supports the positive electrode active material layer and plays a role in transferring electrons between the external conductor and the positive electrode active material layer.

[0072] The positive electrode current collector is not particularly limited as long as it has high electronic conductivity without inducing chemical changes in the all-solid-state battery. For example, copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, silver, etc., and aluminum-cadmium alloys can be used as the positive electrode current collector.

[0073] The positive electrode current collector may have a fine uneven surface or a three-dimensional porous structure to enhance the bonding force with the positive electrode active material layer. This allows the positive electrode current collector to take on a variety of forms, such as film, sheet, foil, mesh, net, porous material, foam, or nonwoven fabric.

[0074] Such positive electrodes can be manufactured by conventional methods. Specifically, a composition for forming a positive electrode active material layer, prepared by mixing a positive electrode active material, a conductive material, and a binder in an organic solvent, is applied to a positive electrode current collector and dried, and then selectively compressed and molded onto the current collector to improve electrode density. In this case, it is preferable to use an organic solvent that can uniformly disperse the positive electrode active material, binder, and conductive material and that evaporates easily. Specifically, examples include acetonitrile, methanol, ethanol, tetrahydrofuran, water, isopropyl alcohol, dimethyl sulfoxide (DMSO), and methylpyrrolidone (NMP, N-Methyl-2-Pyrrolidone).

[0075] On the other hand, the negative electrode included in the all-solid-state battery includes a negative electrode active material layer, and the negative electrode active material layer may be formed on at least one surface of the negative electrode current collector. Such a negative electrode active material layer may include a negative electrode active material, a conductive material, and a binder.

[0076] The negative electrode active material may include a material into which lithium (Li+) can be reversibly intercalated or deintercalated, a material that can react with lithium ions to reversibly form a lithium-containing compound, a lithium metal, or a lithium alloy.

[0077] The material in which lithium ions (Li+) can be reversibly inserted into or removed from may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. The material in which lithium ions (Li+) can be reversibly reacted to form a lithium-containing compound may be, for example, tin oxide, titanium nitrate, or silicon. The lithium alloy may be, for example, an alloy of lithium (Li) with a metal selected from the group consisting of sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al), and tin (Sn).

[0078] Preferably, the negative electrode active material may be lithium metal, and more specifically, it may be in the form of a lithium metal thin film or lithium metal powder.

[0079] The negative electrode active material may be present in an amount of 40 to 80% by weight based on the total weight of the negative electrode active material layer. Specifically, the content of the negative electrode active material may be 40% or more by weight, 50% or more by weight, or 70% or less by weight, or 80% or less by weight. If the content of the negative electrode active material is less than 40% by weight, the electrical characteristics will be insufficient, and if it exceeds 80% by weight, the mass transfer resistance may increase.

[0080] Furthermore, the binder is as described above in the positive electrode active material layer.

[0081] Furthermore, the conductive material is as described above in the positive electrode active material layer.

[0082] Furthermore, the negative electrode current collector is not particularly limited as long as it is conductive without inducing a chemical change in the battery. For example, the negative electrode current collector can be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloy. In addition, the negative electrode current collector can be made of various forms such as films, sheets, foils, nets, porous materials, foams, and nonwoven fabrics with fine irregularities formed on their surface, similar to the positive electrode current collector.

[0083] The method for manufacturing the negative electrode is not particularly limited, and it can be manufactured by forming a negative electrode active material layer on a negative electrode current collector using a layer or film formation method commonly used in the industry. For example, methods such as crimping, coating, and vapor deposition can be used. Furthermore, the negative electrode of the present invention is also included in the case where a metallic lithium thin film is formed on a metal plate by initial filling after the battery is assembled without a lithium thin film on the negative electrode current collector.

[0084] On the other hand, according to an additional embodiment of the invention, a battery module including the all-solid-state battery as a unit battery, a battery pack including the battery module, and a device including the battery pack as a power source are provided.

[0085] Specific examples of the aforementioned devices include, but are not limited to, power tools powered by battery-powered motors; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters; electric golf carts; and power storage systems.

[0086] The following examples are provided to facilitate understanding of the invention, but these examples are provided only to make the invention easier to understand, and the invention is not limited thereto.

[0087] Examples Examples 1-3 and Comparative Example 1: Production of a Composite Solid Electrolyte A polyethylene oxide (PEO) copolymer of the following chemical formula 1a was prepared: [ka]

[0088] In the aforementioned chemical formula 1a, the ratio of l to m was 85:15, and the weight-average molecular weight (Mw) of the copolymer was approximately 2,000,000 g / mol.

[0089] After mixing LiTFSI as a lithium salt with the polyethylene oxide copolymer, a polymer solution was prepared using acetonitrile solvent, and this solution was stirred for 24 hours using a magnetic bar. LSTP as a ceramic compound was then mixed with the prepared polymer solution to produce a mixture of polymer and ceramic compound, which was then stirred using a paste mixer at 1500 rpm / 3 minutes for 5 cycles. At this time, the composition of the mixture of the non-crosslinked copolymer matrix and ceramic compound was determined by mixing 36 parts by weight of LiTFSI (lithium salt) and 10 parts by weight (Example 1), 20 parts by weight (Example 2), 40 parts by weight (Example 3), and 60 parts by weight (Comparative Example 1) of LSTP (ceramic compound) per 100 parts by weight of polymer matrix, so that the polymer matrix concentration in the mixture was 14.3% by weight, and the polymer matrix-ceramic compound concentration was 16.7% by weight using acetonitrile solvent. After casting the prepared mixture onto the lower substrate of the coin cell, it was subjected to primary drying at room temperature for 12 hours, followed by secondary drying in a vacuum oven at 100°C for 12 hours to produce a composite solid electrolyte film with a thickness of 200 μm.

[0090] Comparative Examples 2-4: Manufacturing of Composite Solid Electrolytes A polyethylene oxide (PEO) copolymer of the following chemical formula 1b was prepared: [ka]

[0091] In the above chemical formula 1b, R1 is -CH2-O-(CH2-CH2-O) k The copolymer is -CH3, R2 is -CH2-O-CH2-CH=CH2, k is 2, the l:m:n ratio is 85:13:2, and the weight-average molecular weight (Mw) of the copolymer was approximately 2,000,000 g / mol.

[0092] The copolymer of chemical formula 1b has an allyl group linked via a methylene oxide linker as a crosslinking functional group.

[0093] The polyethylene oxide copolymer was mixed with trimethylolpropane trimethacrylate as a crosslinking agent, benzoyl peroxide as an initiator, LiTFSI as a lithium salt, and LSTP as a ceramic compound to produce a mixture of polyethylene oxide copolymer and ceramic compound. This mixture was then stirred for 24 hours using a magnetic bar. At this time, the composition of the polyethylene oxide copolymer and ceramic compound mixture was prepared by mixing 100 parts by weight of polyethylene oxide copolymer with 20 parts by weight of trimethylolpropane trimethacrylate as a crosslinking agent, 1 part by weight of benzoyl peroxide as an initiator, 36 parts by weight of LiTFSI as a lithium salt, and 0 parts by weight (Comparative Example 1), 10 parts by weight (Comparative Example 2), and 80 parts by weight (Comparative Example 3) of LSTP as ceramic compounds. The concentration of polyethylene oxide copolymer in the mixture of the polymer and ceramic compound was 11.1% by weight, and the concentration of polyethylene oxide and ceramic compound was 14.9% by weight using acetonitrile solvent.

[0094] After casting the prepared mixture onto the lower substrate of the coin cell, it was subjected to primary drying at room temperature for 12 hours, followed by secondary drying in a vacuum oven at 100°C for 12 hours to form an electrolyte film with a thickness of 200 μm, thereby producing a composite solid electrolyte.

[0095] Experimental example Experimental Example 1: Measurement of Ionic Conductivity of Solid Electrolytes To measure the ionic conductivity of the solid electrolytes prepared in the examples and comparative examples, 1.7671 cm⁻¹ was used. 2 After forming the solid electrolyte on the lower substrate of a coin cell of a certain size, a coin cell for ionic conductivity measurement was manufactured using SUS as an inert electrode (blocking electrode).

[0096] Using an electrochemical impedance spectrometer (EIS, VM3, Bio Logic Science Instrument), the resistance was measured at 25°C under conditions of an amplitude of 10mV and a scan range from 1Hz to 0.1MHz. The ionic conductivity of the solid electrolyte was then calculated using Equation 1 below.

number

[0097] In equation 1 above, σ i R is 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 (cm²) of the solid electrolyte. 2 ) means.

[0098] Table 1 below shows the calculated ionic conductivity values. [Table 1]

[0099] As shown in Table 1 above, the composite solid electrolytes of the examples, manufactured using branched and non-crosslinked PEO and a certain amount of ceramic compound, were confirmed to exhibit improved ionic conductivity compared to Comparative Example 1, which exceeded the appropriate content range of the ceramic compound, or to the solid electrolytes of Comparative Examples 2-4, which were manufactured using crosslinked PEO.

Claims

1. A polymer containing a non-crosslinked PEO (polyethylene oxide) copolymer having a branched structure containing repeating units of the following chemical formulas 1 and 2; a lithium salt; and a ceramic compound. The lithium salt and ceramic compound are dispersed on the polymer. The ceramic compound is included in a composite solid electrolyte in an amount of 10 to 45 parts by weight per 100 parts by weight of the polymer: 【Chemistry 1】 【Chemistry 2】 In the above chemical formulas 1 and 2, R １ ha-CH ２ -O-(CH ２ -CH ２ -O) ｋ -R ３ This shows that k is between 0 and 20, and R ３ This represents an alkyl group having 1 to 5 carbon atoms. l and m are the number of repetitions in the repeating unit, and are independent integers between 1 and 100,000.

2. The composite solid electrolyte according to claim 1, wherein the ceramic compound comprises an oxide-based solid electrolyte of a lithium metal oxide or lithium metal phosphorus oxide.

3. The composite solid electrolyte according to 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.

4. The composite solid electrolyte according to claim 1, wherein the lithium salt is contained in an amount of 10 to 40 parts by weight per 100 parts by weight of the polymer.

5. The composite solid electrolyte according to claim 1, having a dry film state that does not contain liquid.

6. A step of forming a mixture containing a polymer having a branched structure including repeating units of chemical formulas 1 and 2, a lithium salt, and the ceramic compound. A method for producing a composite solid electrolyte according to claim 1, comprising the steps of casting and drying the mixture to form a film.

7. An all-solid-state battery comprising an electrolyte layer containing a composite solid electrolyte according to any one of claims 1 to 5.

8. The all-solid-state battery according to claim 7, comprising a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and an electrolyte layer interposed between the positive electrode and the negative electrode and containing the composite solid electrolyte.

Images