Composite solid electrolyte and all-solid-state battery comprising same

Abstract

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

Description

Composite solid electrolyte and all-solid-state battery containing the same

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0048815, filed April 11, 2024, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to a composite solid electrolyte and an all-solid-state battery including the same.

[0004] Lithium-ion batteries using liquid electrolytes have a structure where the anode and cathode are separated by a separator. Damage to the separator due to deformation or external impact can cause a short circuit, potentially leading to risks such as overheating or explosion. Therefore, the development of a solid electrolyte that can ensure safety in lithium-ion secondary batteries is a critical task.

[0005] Lithium secondary batteries using solid electrolytes offer enhanced safety, improved reliability by preventing electrolyte leakage, and the ease of manufacturing thin batteries. Furthermore, the use of lithium metal as the anode enhances energy density. Consequently, solid electrolytes are expected to find applications in small-sized secondary batteries as well as high-capacity secondary batteries for electric vehicles, drawing attention as next-generation batteries.

[0006] Among solid electrolytes, polymer solid electrolytes can use polymer materials with ion-conducting properties, and can be used in the form of composite solid electrolytes that mix inorganic materials with these polymer materials.

[0007] Conventional hybrid (composite) solid electrolytes, such as these, are manufactured by dispersing inorganic powders such as oxide ceramics in a polymer matrix. Compared to existing liquid electrolytes, they have high ignition and combustion stability, and compared to polymer solid electrolytes, they have the advantage of high ionic conductivity. However, there has been a difficulty in that basic prerequisites such as improving the dispersibility of oxide ceramic particles within the polymer matrix and optimizing the physical properties of the polymer matrix used must be satisfied. In particular, when a polymer containing a highly crystalline unit, such as polyethylene oxide (PEO) or polypropylene oxide (PPO), is used as the matrix, there has been a problem in that it is difficult to manufacture a composite solid electrolyte with improved ionic conductivity. In other words, the high crystallinity of the PEO or PPO polymers inhibits the chain mobility of the polymer, reducing the dispersibility of the oxide ceramics, and restricting the movement of lithium ions within the composite solid electrolyte. Consequently, there has been a limit to improving the ionic conductivity of the composite solid electrolyte. In addition, when using additional plasticizers or dispersants to improve the dispersibility of the above ceramics, there are limitations such as a possible deterioration in electrochemical properties and a complicated process.

[0008] In particular, it was known that it was not easy to secure an ionic conductivity of 0.1 mS / cm or more at room temperature when applying conventional composite solid electrolyte manufacturing technology.

[0009] In addition, when a (block) copolymer including a polypropylene oxide (PPO) unit is used as the polymer matrix, since the polymer matrix is ​​prepared in a gas phase and a composite solid electrolyte is formed through a gas phase / liquid phase reaction, the overall electrolyte manufacturing process becomes complicated, and process problems such as difficulty in controlling the thickness of the solid electrolyte membrane occur. In addition, the PPO-based polymer matrix has a large shrinkage rate during molding, is prone to aging, and has poor impact resistance at low temperatures, so the composite solid electrolyte manufactured using the same may also have insufficient physical properties.

[0010] 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 a ceramic compound and a lithium salt on a polymer.

[0011] In addition, the present invention provides an all-solid-state battery including a composite solid electrolyte with improved ionic conductivity.

[0012] According to one embodiment of the invention, a composite solid electrolyte is provided, comprising: a polymer comprising a non-crosslinked PEO (polyethylene oxide) copolymer having a branched structure including 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 based on 100 parts by weight of the polymer:

[0013] [Chemical Formula 1]

[0014]

[0015] [Chemical Formula 2]

[0016]

[0017] In the above chemical formulas 1 and 2, R1 is -CH2-O-(CH2-CH2-O) k-R3 represents, k is 0 to 20, R3 represents an alkyl group having 1 to 5 carbon atoms,

[0018] l and m are the repetition numbers of the repeating unit, and are each independently integers from 1 to 100000.

[0019] In addition, in the composite solid electrolyte of the above embodiment, the ceramic compound may include an oxide-based solid electrolyte of lithium metal oxide or lithium metal phosphate, and more specifically, may include at least one oxide-based solid electrolyte selected from the group consisting of a lithium-lanthanum-zirconium oxide-based (LLZO) compound, a lithium-silicon titanium phosphate-based (LSTP) compound, a lithium-lanthanum-titanium oxide-based (LLTO) compound, a lithium-aluminum-titanium phosphate-based (LATP) compound, a lithium-aluminum-germanium phosphate-based (LAGP) compound, and a lithium-lanthanum-zirconium-titanium oxide-based (LLZTO) compound.

[0020] Additionally, in the composite solid electrolyte, the lithium salt may be included in an amount of 10 to 40 parts by weight relative to 100 parts by weight of the polymer.

[0021] The above-described composite solid electrolyte can be provided in a dry film state without containing liquid.

[0022] According to another embodiment of the invention, a method for producing the composite solid electrolyte is provided. The method may include: forming a mixture comprising a polymer including a non-crosslinked PEO (polyethylene oxide) copolymer having a branched structure including repeating units of the chemical formulae 1 and 2; a lithium salt; and a ceramic compound; and casting and drying the mixture to form a film.

[0023] In addition, according to a further embodiment of the invention, an all-solid-state battery is provided, which includes an electrolyte layer including the composite solid electrolyte of the above embodiment. The all-solid-state battery may include a positive electrode including a positive active material; a negative electrode including a negative active material; and an electrolyte layer interposed between the positive electrode and the negative electrode and including the composite solid electrolyte.

[0024] The composite solid electrolyte according to the present invention disperses a ceramic compound and a lithium salt in a fixed amount in a non-crosslinked PEO polymer matrix having a branched structure, thereby uniformly distributing the ceramic compound and the like without aggregation between the individual components or aggregation of particles. As a result, the ceramic compound and the like can be uniformly dispersed while reducing the influence of crystallinity of linear polymers, thereby exhibiting improved ionic conductivity.

[0025] Additionally, the composite solid electrolyte can be manufactured through a simplified process of mixing each component to prepare it in a liquid state and then casting it in a film state due to the excellent dispersibility of the polymer matrix, thereby exhibiting excellent processability and mass production.

[0026] Hereinafter, embodiments of the invention will be described in more detail to help understand the invention.

[0027] The terms and words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0028]

[0029] Previously, in order to improve the ionic conductivity of solid electrolytes, composite solid electrolytes were manufactured by mixing ceramic compounds such as oxides or lithium salts into a polymer matrix having a cross-linked structure, etc. However, these composite solid electrolytes had problems in that the oxide-based ceramic particles within the polymer matrix were unevenly distributed, or when a polymer containing a highly crystalline unit such as polyethylene oxide or polypropylene oxide was used as the polymer, the dispersibility and ionic conductivity of the ceramic compound were reduced. In particular, it is true that there was a limit to the uniform improvement in ionic conductivity as aggregation occurred between the particles of the ceramic compound, etc.

[0030] Accordingly, the inventors of the present invention mixed a PEO (polyethylene oxide) copolymer having a branched and non-crosslinked structure including a specific unit with a ceramic compound and a lithium salt, and then formed a film and dried it to produce a composite solid electrolyte including a polymer in which a ceramic compound, etc. is uniformly dispersed between the polymer chains.

[0031] In particular, the polymer matrix can exhibit excellent dispersibility for ceramic compounds, etc., and as a result, it enables the production of a composite solid electrolyte exhibiting excellent ionic conductivity, etc., through a simple process without the use of a separate plasticizer or dispersant, etc.

[0032] Therefore, according to one embodiment of the invention, it was confirmed that a composite solid electrolyte exhibiting improved ionic conductivity compared to existing composite solid electrolytes can be manufactured and provided through a simplified process, thereby completing the invention.

[0033]

[0034] Hereinafter, the composite solid electrolyte of the above embodiment will be specifically described.

[0035] composite solid electrolyte

[0036] According to one embodiment of the invention, a composite solid electrolyte comprises a polymer including 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.

[0037] In these composite solid electrolytes, the non-crosslinked PEO copolymer having the branched structure does not have a crosslinkable functional group, and at least some of the PEO repeating units have a branched chain including an alkylene oxide repeating structure. The structure of this branched chain is, for example, -CH2-O-(CH2-CH2-O). k -R3 (k is 0 to 20, and R3 is an alkyl group having 1 to 5 carbon atoms) can be defined, and such branched chains can be bonded to the main chain of some of the PEO repeating units. In a more specific example, the branched, non-crosslinked PEO copolymer can be one that does not include additional polymer units such as polypropylene oxide (PPO).

[0038] In the structure of the copolymer, the branched chain may be a substituent that acts as a type of plasticizer. Therefore, uniform dispersion of a ceramic compound or the like in a polymer phase including the copolymer can be induced. As a result, the composite solid electrolyte of one embodiment can exhibit excellent ionic conductivity even with a relatively small content of the ceramic compound, without the use of additional additives such as a separate plasticizer or dispersant. In addition, since the copolymer does not contain additional polymer units such as PPO, the physical properties of the composite solid electrolyte, such as impact resistance, can also be maintained excellently.

[0039] In a more specific embodiment, the non-crosslinked PEO copolymer having the branched structure may be a copolymer comprising repeating units of the following chemical formulae 1 and 2:

[0040] [Chemical Formula 1]

[0041]

[0042] [Chemical Formula 2]

[0043]

[0044] In the above chemical formulas 1 and 2, R1 is -CH2-O-(CH2-CH2-O) k -R3 represents, k is 0 to 20, R3 represents an alkyl group having 1 to 5 carbon atoms,

[0045] l and m are the repetition numbers of the repeating unit, and are each independently an integer from 1 to 100000, or from 50 to 80000, or from 100 to 50000.

[0046] For example, the branched chain of the above R1 can induce uniform dispersion of a ceramic compound or the like as described above, thereby allowing the composite solid electrolyte of one embodiment to exhibit improved ionic conductivity.

[0047] In the above copolymer, if l and m are too small, it is difficult to form a polymer due to the small molecular weight, and in particular, if the repeating unit of Chemical Formula 2 is not included, the ionic conductivity of the composite solid electrolyte of one embodiment may be reduced. If l and m are too large, the viscosity increases, solubility may decrease when preparing a polymer solution, and molding for preparing a solid electrolyte may become difficult.

[0048] The weight average molecular weight (Mw) of the copolymer comprising the above chemical formulae 1 and 2 may be 100,000 g / mol to 4,000,000 g / mol, specifically, may be 100,000 g / mol or more, 200,000 g / mol or more, or 300,000 g / mol or more, and 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 too small, the mechanical properties of the solid electrolyte produced may not be satisfied. If the weight average molecular weight (Mw) of the copolymer is too large, the solubility may decrease during the production of a polymer solution due to an increase in viscosity, and molding for the production of a solid electrolyte may become difficult. In addition, the ionic conductivity of the composite solid electrolyte may decrease due to an increase in crystallinity and a decrease in chain mobility within the solid electrolyte.

[0049] Additionally, the copolymer may be a random copolymer or a block copolymer.

[0050] In one embodiment of the invention, the composite solid electrolyte may further comprise a lithium salt. The lithium salt may be incorporated in the internal space between the polymer chains in a dissociated ionic state, thereby enhancing the ionic conductivity of the composite solid electrolyte. At least a portion of the dissociated cations and / or anions in the lithium salt may remain bound to the polymer chains, thereby exhibiting mobility during charging / discharging of the battery.

[0051] The lithium salt is (CF3SO2)2NLi(Lithium bis(trifluoromethanesulphonyl)imide, LiTFSI), (FSO2)2NLi(Lithium bis(fluorosulfonyl)imide, LiFSI), LiNO3, LiOH, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl 10, LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiSCN, LiC(CF3SO2)3, lithium chloroborane, lithium lower aliphatic carboxylic acid, and lithium tetraphenylborate.

[0052] In addition, the lithium salt may be included in an amount of 10 to 40 parts by weight based on 100 parts by weight of the branched and non-crosslinked PEO copolymer, and specifically, may be included in an amount of 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 content of the lithium salt is less than 10 parts by weight, the ionic conductivity of the composite solid electrolyte may be reduced, and if it exceeds 40 parts by weight, the mechanical strength may be reduced.

[0053] In one embodiment of the invention, the composite solid electrolyte may include a ceramic compound. The ceramic compound has a lithium ion transport capability to improve the conductivity of lithium ions, preferably contains lithium atoms but has the function of transporting lithium ions without storing lithium, thereby improving the ion conductivity of the composite solid electrolyte.

[0054] In addition, the ceramic compound may be uniformly dispersed in the non-crosslinked and branched polymer phase. The ceramic compound can be uniformly dispersed between polymer chains without agglomeration 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.

[0055] In addition, the ceramic compound may be in the form of particles. Due to the morphological characteristics of particles, they can be included in a more uniformly dispersed state within the composite solid electrolyte. The particles of the ceramic compound may be spherical and may have a diameter of 100 nm to 1000 nm. If the diameter is less than 100 nm, the non-crystallization effect due to a decrease in the crystallinity of the polymer may be minimal, and if it exceeds 1000 nm, the dispersibility may be reduced due to an increase in aggregation between particles, making it difficult to uniformly disperse them.

[0056] The ceramic chemical may be an oxide-based or phosphate-based compound, and may be, for example, an oxide-based solid electrolyte in the form of lithium metal oxide or lithium metal phosphate. However, considering the appropriate dispersibility of the ceramic compound and the excellent ionic conductivity of the solid electrolyte, an oxide-based solid electrolyte in the form of lithium metal phosphate may be more appropriately used.

[0057] More specifically, the ceramic compound is a garnet-type lithium-lanthanum-zirconium oxide system (LLZO, Li7La3Zr2O 12 ) compound, perovskite type lithium-lanthanum-titanium oxide system (LLTO, Li3xLa 2 / 3-x TiO3) compound, NASICON type lithium-aluminum-titanium phosphate (LATP, Li) of phosphate type 1+x Al x Ti 2-x (PO4)3) compound, lithium-aluminum-germanium phosphate system (LAGP, Li 1.5 Al 0.5 Ge 1.5(PO4)3) compounds, lithium-silicon-titanium phosphate (LSTP, LiSiO2TiO2(PO4)3) compounds, and lithium-lanthanum-zirconium-titanium oxide (LLZTO) compounds, and more preferably, at least one oxide-based solid electrolyte 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, at least one selected from the group consisting of lithium-silicon titanium phosphate (LSTP) compounds, lithium-aluminum-titanium phosphate (LATP) compounds, and lithium-aluminum-germanium phosphate (LAGP) compounds having the lithium metal phosphate form can be more appropriately used in terms of ion conductivity of the solid electrolyte.

[0058] The above oxide-based solid electrolyte generally has a maximum temperature of 10 -4 10 inland -3 It has an ionic conductivity value of S / cm, is stable in the high voltage range, is stable in air, and has the advantages of being easy to synthesize and handle.

[0059] In addition, the ceramic compound does not easily combust or ignite even under high-temperature conditions of 400°C or higher, thus exhibiting high high-temperature stability. Therefore, when the composite solid electrolyte includes the ceramic compound, the mechanical strength, high-temperature stability, and ionic conductivity of the composite solid electrolyte can be improved.

[0060] The above ceramic compound may be included in an amount of 10 to 45 parts by weight, or 20 to 40 parts by weight, based on 100 parts by weight of the PEO copolymer including the cross-linking functional group.

[0061] If the above ceramic compound is included in an excessively small amount, the effect of lowering the polymer crystallinity and making it amorphous by the ceramic compound is reduced, so the effect of increasing the ionic conductivity of the composite solid electrolyte is not significant, and the mechanical properties may also fall short of the expected level due to the formation of a composite.

[0062] If the ceramic compound is included in an excessively large amount, the ceramic compound is not uniformly dispersed within the polymer, causing the ceramic compound particles to clump together and aggregate, resulting in the production of a composite solid electrolyte with reduced ionic conductivity.

[0063] The composite solid electrolyte of the above-described embodiment can be provided in a dry film state that does not contain a liquid such as an organic solvent or electrolyte, and can exhibit excellent ionic conductivity in this dry film state. As a result, the composite solid electrolyte can significantly contribute to the provision of an all-solid-state battery exhibiting excellent electrical characteristics.

[0064] Method for manufacturing composite solid electrolyte

[0065] The method for manufacturing the above-described composite solid electrolyte may include a step of forming a mixture comprising a polymer including a non-crosslinked PEO (polyethylene oxide) copolymer having a branched structure including repeating units of the above chemical formulae 1 and 2; a lithium salt and a ceramic compound; and a step of casting and drying the mixture to form a film.

[0066] In the above manufacturing method, due to the excellent dispersibility of the copolymer, etc., a composite solid electrolyte can be manufactured by a simplified method of mixing a polymer matrix including the copolymer with a ceramic compound, etc. to form a solution or dispersion, and forming a film.

[0067] In this manufacturing method, the non-crosslinked PEO copolymer having the branched structure has already been described above, so further description will be omitted.

[0068] In one embodiment of the invention, the lithium salt and ceramic compound may be the same as those used in the composite solid electrolyte described above, and the content may also be the same.

[0069] In the above-mentioned mixture forming step, a polymer including the PEO-based copolymer and a mixture including a lithium salt and a ceramic compound can be applied onto a substrate to form a coating film. At this time, the mixture can be prepared by mixing the PEO-based copolymer, a lithium salt, and a ceramic compound in a solvent.

[0070] The solvent is not particularly limited as long as it can dissolve the PEO copolymer and 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), methyl pyrrolidone (NMP), or dimethyl formamide (DMF, N,N-Dimethyl formamide).

[0071] The concentration of the above mixture may be appropriately adjusted to ensure that the molding process for manufacturing the composite solid electrolyte can proceed smoothly. Specifically, the concentration of the above mixture may refer to the concentration (w / w%) of the PEO copolymer in the mixture. For example, the concentration of the above mixture may be 5% to 20%, specifically, 5% or more, 7% or more, or 9% or more, and 13% or less, 17% or less, or 20% or less. If the concentration of the above mixture is less than 5%, the concentration may be excessively dilute, which may lower the mechanical strength of the composite solid electrolyte or cause it to flow when applied onto a substrate. On the other hand, if it is more than 20%, it may be difficult to dissolve the lithium salt in the mixture at a desired concentration, and the viscosity may be high, which may reduce the solubility or make it difficult to apply it in a uniform thin film form.

[0072] The above substrate is not particularly limited as long as it can serve as a support for the coating film. For example, the above substrate may be SUS (Stainless Steel), a polyethylene terephthalate film, a polytetrafluoroethylene film, a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a vinyl chloride copolymer film, a polyurethane film, an ethylene-vinylacetate film, an ethylene-propylene copolymer film, an ethylene-ethyl acrylate copolymer film, an ethylene-methyl acrylate copolymer film, or a polyimide film.

[0073] In addition, the coating method is not particularly limited as long as it is a method that can form a coating film by coating the mixture on 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.

[0074] The coating film formed on the substrate by the above coating method can be formed into a solid electrolyte film from which the residual solvent is completely removed through a drying process. The drying can be divided into a first drying process and a second drying process to prevent film shrinkage due to rapid evaporation of the solvent. The first drying process can remove some of the solvent through room temperature drying, and the second drying process can completely remove the solvent through vacuum high-temperature drying. The high-temperature drying can be performed at a temperature of 80°C to 130°C. If the high-temperature drying temperature is lower than 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.

[0075] Through the manufacturing method described above, a composite solid electrolyte of one embodiment in which a ceramic compound is uniformly dispersed between branched and non-crosslinked polymer chains can be manufactured.

[0076] All-solid-state batteries

[0077] A further embodiment of the invention also relates to an all-solid-state battery comprising an electrolyte layer including the composite solid electrolyte, wherein the all-solid-state battery may 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. In this case, the electrolyte layer may include the composite solid electrolyte of one embodiment.

[0078] Specifically, the composite solid electrolyte comprises a polymer including a branched and non-crosslinked PEO (polyethylene oxide) copolymer, a lithium salt, and a ceramic compound, and since the ceramic compound and the like are uniformly dispersed on the polymer, ion conductivity is improved, and thus the composite solid electrolyte can be suitable as an electrolyte for an all-solid-state battery.

[0079] Meanwhile, the positive electrode included in the above-described all-solid-state battery includes 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.

[0080] The above positive electrode active material layer includes a positive electrode active material, a binder, and a conductive material.

[0081] In addition, 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 one element selected from the group consisting of Al, Ga, and In, or two or more of these elements; 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')O 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 includes at least one selected from the group consisting of Mn and Ni, Co, Fe, Cr, V, Cu, Zn and Ti; M' is at least one selected from the group consisting of Al, Mg and B, and A is at least one selected from the group consisting of P, F, S and N.) layered compounds or compounds substituted with one or more transition metals; chemical formula Li 1+y Mn 2-y Lithium manganese oxides such as O4 (where y is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-y Ni-site type lithium nickel oxide represented by MyO2 (wherein, 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 by O2 (wherein, M=Co, Ni, Fe, Cr, Zn or Ta, and y=0.01 to 0.1) or Li2Mn3MO8 (wherein, M=Fe, Co, Ni, Cu or Zn); LiMn2O4 in which a portion of Li in the chemical formula is replaced with an alkaline earth metal ion; disulfide compounds; Fe2(MoO4)3, etc., but are not limited thereto.

[0082] In addition, 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, and 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 and electrical characteristics between the positive electrode active materials may be insufficient, and if it is more than 80 wt%, the material transfer resistance may increase.

[0083] In addition, the binder is a component that assists in the bonding of the positive electrode active material and the conductive material and the bonding to 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, fluorine rubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepoxychlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenol resin, epoxy resin, carboxymethylcellulose, hydroxypropyl cellulose, cellulose acetate, The binder may include at least one selected from the group consisting of 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 at least one selected from the group consisting of styrene-butadiene rubber, polytetrafluoroethylene, carboxymethylcellulose, polyacrylic acid, lithium polyacrylate, and polyvinylidene fluoride.

[0084] In addition, 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, and specifically, the content of the binder may be 1 wt% or more or 3 wt% or more, and 15 wt% or less or 30 wt% or less. If the content of the binder is less than 1 wt%, the adhesive strength between the positive electrode active material and the positive electrode current collector may be reduced, and if it exceeds 30 wt%, the adhesive strength may be improved, but the content of the positive electrode active material may be reduced, which may lower the battery capacity.

[0085] In addition, the conductive material is not particularly limited as long as it prevents side reactions in the internal environment of the all-solid-state battery, does not cause chemical changes in the battery, and has excellent electrical conductivity. Representative examples thereof include graphite or conductive carbon, and examples thereof include graphite such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, Denka black, thermal black, channel black, furnace black, lamp black, and summer black; carbon-based materials having a crystal structure of graphene or graphite; conductive fibers such as carbon fiber and metal fiber; fluorinated carbon; metal powders such as aluminum powder and nickel powder; conductive whiskey such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives; which may be used alone or in combination of two or more thereof, but are not necessarily limited thereto.

[0086] 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, and specifically, the content of the conductive material may be 0.5 wt% or more or 1 wt% or more, and 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 effect of improving electrical conductivity or the electrochemical characteristics of the battery may deteriorate, and if it exceeds 30 wt%, the amount of the positive electrode active material may be relatively small, which may lower the capacity and energy density. The method of including the conductive material in the positive electrode is not particularly limited, and a conventional method known in the art, such as coating on the positive electrode active material, may be used.

[0087] In addition, the positive electrode current collector supports the positive electrode active material layer and serves to transfer electrons between the external conductor and the positive electrode active material layer.

[0088] The positive electrode current collector is not particularly limited as long as it has high electronic conductivity without causing chemical changes in the all-solid-state battery. For example, the positive electrode current collector may be copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, silver, etc., or an aluminum-cadmium alloy.

[0089] The positive electrode current collector may have a finely irregular structure on its surface or may employ a three-dimensional porous structure to strengthen the bonding strength with the positive electrode active material layer. Accordingly, the positive electrode current collector may include various forms such as a film, sheet, foil, mesh, net, porous body, foam, or non-woven fabric.

[0090] The positive electrode as described above can be manufactured according to a conventional method, and specifically, a composition for forming a positive electrode active material layer prepared by mixing a positive electrode active material, a conductive agent, and a binder in an organic solvent phase is applied and dried on a positive electrode current collector, and optionally, compression molded on the current collector to improve the electrode density, can be manufactured. At this time, it is preferable to use an organic solvent that can uniformly disperse the positive electrode active material, the binder, and the conductive agent, and that easily evaporates. Specifically, examples thereof include acetonitrile, methanol, ethanol, tetrahydrofuran, water, isopropyl alcohol, dimethyl sulfoxide (DMSO), and methyl pyrrolidone (NMP, N-Methyl-2-Pyrrolidone).

[0091] Meanwhile, the negative electrode included in the above-described 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. The negative electrode active material layer may include a negative electrode active material, a conductive material, and a binder.

[0092] The above negative 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.

[0093] 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 reversibly forming a lithium-containing compound by reacting with the lithium ions (Li+) may be, for example, tin oxide, titanium nitrate, or silicon. The lithium alloy may be, for example, an alloy of a metal selected from the group consisting of lithium (Li) and 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).

[0094] Preferably, the negative active material may be lithium metal, and specifically, may be in the form of a lithium metal thin film or lithium metal powder.

[0095] 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, and 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 characteristics may not be sufficient, and if it is more than 80 wt%, the material transfer resistance may increase.

[0096] In addition, the binder is as described above in the positive electrode active material layer.

[0097] In addition, the above-described conductive material is as described above in the positive electrode active material layer.

[0098] In addition, the negative electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery. For example, the negative electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., an aluminum-cadmium alloy, etc. In addition, the negative electrode current collector, like the positive electrode current collector, may be made of various forms such as a film, sheet, foil, net, porous body, foam, non-woven body, etc. having fine irregularities formed on the surface.

[0099] The method for manufacturing the above negative electrode is not particularly limited, and can be manufactured by forming a negative electrode active material layer on the negative electrode current collector using a method for forming a layer or film commonly used in the art. For example, methods such as compression, coating, and deposition can be used. In addition, a case in which a battery is assembled without a lithium thin film on the negative electrode current collector and then a metallic lithium thin film is formed on a metal plate by initial charging is also included in the negative electrode of the present invention.

[0100] Meanwhile, 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.

[0101] At this time, specific examples of the device include, but are not limited to, a power tool that is powered by an electric motor; an electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), etc.; an electric two-wheeled vehicle including an electric bicycle (E-bike) and an electric scooter (E-scooter); an electric golf cart; and a power storage system.

[0102]

[0103] Hereinafter, preferred embodiments are presented to help understand the invention, but the following embodiments are provided only to make it easier to understand the invention and the invention is not limited thereto.

[0104]

[0105] Example

[0106] Examples 1 to 3 and Comparative Example 1: Preparation of composite solid electrolyte

[0107] A polyethylene oxide (PEO) copolymer of the following chemical formula 1a was prepared:

[0108] [Chemical Formula 1a]

[0109]

[0110] In the above chemical formula 1a, the ratio of l:m was 85:15, and the weight average molecular weight (Mw) of the copolymer was about 2,000,000 g / mol.

[0111] After mixing LiTFSI as a lithium salt into the above polyethylene oxide copolymer, a polymer solution was prepared using acetonitrile solvent, and then stirred using a magnetic bar for 24 hours. LSTP as a ceramic compound was mixed into the prepared polymer solution to prepare a mixture of polymer and ceramic compound, and then stirred using a paste mixer at 1500 rpm / 3 minutes, repeating the conditions five times. At this time, the composition of the mixed solution of the non-crosslinked copolymer matrix and the ceramic compound was such that 36 parts by weight of LiTFSI as a 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 as a ceramic compound were mixed with respect to 100 parts by weight of the polymer matrix, and the concentration of the polymer matrix contained in the mixed solution was 14.3% by weight, and the acetonitrile solvent was used so that the concentration of the polymer matrix-ceramic compound was 16.7% by weight. After solution casting the prepared mixed solution on the lower substrate of the coin cell, it was first dried at room temperature for 12 hours, and then secondarily dried in a vacuum oven at 100°C for 12 hours to prepare a composite solid electrolyte film having a thickness of 200 μm.

[0112]

[0113] Comparative Examples 2 to 4: Preparation of composite solid electrolytes

[0114] A polyethylene oxide (PEO) copolymer of the following chemical formula 1b was prepared:

[0115] [Chemical Formula 1b]

[0116]

[0117] In the above chemical formula 1b, R1 is -CH2-O-(CH2-CH2-O) k-CH3, 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 was about 2,000,000 g / mol.

[0118] The copolymer of the above chemical formula 1b has an allyl group bonded via a methylene oxide linker as a cross-linking functional group.

[0119] A mixture of the polyethylene oxide copolymer and the ceramic compound was prepared by mixing trimethylolpropane trimethacrylate as a crosslinking agent, benzoyl peroxide as an initiator, LiTFSI as a lithium salt, and LSTP as a ceramic compound with acetonitrile as a solvent in the above polyethylene oxide copolymer, and then stirring the mixture using a magnetic bar for 24 hours. At this time, the composition of the mixture of the polyethylene oxide copolymer and the ceramic compound was such that 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 a ceramic compound were mixed for 100 parts by weight of the polyethylene oxide copolymer, and the concentration of the polyethylene oxide copolymer as a polymer included in the mixture of the polymer and the ceramic compound was 11.1% by weight, and the concentration of the polyethylene oxide and the ceramic compound was 14.9% by weight, using acetonitrile as a solvent.

[0120] After casting the mixture solution prepared above on the lower substrate of a coin cell, it was dried at room temperature for 12 hours, and then dried in a vacuum oven at 100°C for 12 hours to form an electrolyte film with a thickness of 200 μm, thereby preparing a composite solid electrolyte.

[0121]

[0122] Experimental example

[0123] Experimental Example 1: Measurement of the ionic conductivity of a solid electrolyte

[0124] In order to measure the ionic conductivity of the solid electrolyte manufactured in the examples and comparative examples, 1.7671 cm 2 After forming the solid electrolyte on the lower substrate of a coin cell of a size, a coin cell for measuring ionic conductivity was manufactured using SUS as an inactive electrode (blocking electrode).

[0125] The resistance was measured at 25°C using an electrochemical impedance spectrometer (EIS, VM3, Bio Logic Science Instrument) 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 Equation 1 below.

[0126] [Formula 1]

[0127]

[0128] In the above equation 1, σ i is the ionic conductivity of the solid electrolyte (S / cm), R is the resistance of the solid electrolyte (Ω) measured by the electrochemical impedance spectrometer, L is the thickness of the solid electrolyte (㎛), and A is the area of ​​the solid electrolyte (cm 2 ) means.

[0129]

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

[0131]

[0132] Ionic conductivity (S / cm, @25℃) Example 17.8x10 -5 Example 22.1x10 -4 Example 31.3x10 -4 Comparative example 13.6x10 -5 Comparative example 22.3x10 -5 Comparative example 33.6x10 -5Comparative example 41.8x10 -5

[0133] As shown in Table 1 above, it was confirmed that the composite solid electrolyte of the example manufactured using branched and non-crosslinked PEO and a ceramic compound of a certain content exhibited improved ionic conductivity compared to the solid electrolyte of Comparative Example 1, which was manufactured using a ceramic compound outside the appropriate content range, or Comparative Examples 2 to 4, which were manufactured using crosslinked PEO.

Claims

1. A polymer comprising a non-crosslinked PEO (polyethylene oxide) copolymer having a branched structure including repeating units of the following chemical formulas 1 and 2; a lithium salt and a ceramic compound; The above lithium salt and ceramic compound are dispersed on the polymer, A composite solid electrolyte in which the ceramic compound is included in an amount of 10 to 45 parts by weight relative to 100 parts by weight of the polymer: [Chemical Formula 1] [Chemical Formula 2] In the above chemical formulas 1 and 2, R1 is -CH2-O-(CH2-CH2-O) k -R3 represents, k is 0 to 20, R3 represents an alkyl group having 1 to 5 carbon atoms, l and m are the repetition numbers of the repeating unit, and are each independently integers from 1 to 100000.

2. In the first paragraph, the ceramic compound is a composite solid electrolyte including an oxide-based solid electrolyte of lithium metal oxide or lithium metal phosphate.

3. In the first paragraph, the ceramic compound is a composite solid electrolyte comprising at least one oxide-based solid electrolyte selected from the group consisting of a lithium-lanthanum-zirconium oxide (LLZO) compound, a lithium-silicon titanium phosphate (LSTP) compound, a lithium-lanthanum-titanium oxide (LLTO) compound, a lithium-aluminum-titanium phosphate (LATP) compound, a lithium-aluminum-germanium phosphate (LAGP) compound, and a lithium-lanthanum-zirconium-titanium oxide (LLZTO) compound.

4. A composite solid electrolyte in the first paragraph, wherein the lithium salt is included in an amount of 10 to 40 parts by weight relative to 100 parts by weight of the polymer.

5. A composite solid electrolyte having a dry film state without liquid in the first paragraph.

6. A step of forming a mixed solution comprising a polymer including a non-crosslinked PEO (polyethylene oxide) copolymer having a branched structure including repeating units of the above chemical formulas 1 and 2; a lithium salt and the ceramic compound; and A method for producing a composite solid electrolyte of claim 1, comprising the step of casting and drying the above mixture to form it into a film.

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

8. An all-solid-state battery comprising: 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.

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