Solid electrolyte for all-solid-state battery and all-solid-state battery including same

Abstract

Disclosed are: a solid electrolyte for an all-solid-state battery, which can be protected from moisture by chemically reacting a sulfide-containing solid electrolyte with an amphiphilic compound, for example, a material such as a surfactant; and an all-solid-state battery comprising such a solid electrolyte. The solid electrolyte for an all-solid-state battery is surface-modified with an amphiphilic compound having both hydrophilic and hydrophobic groups.

Description

Solid electrolyte for all-solid-state batteries and all-solid-state batteries containing the same

[0001] This application claims the benefit of priority to U.S. patent application Ser. No. 18 / 428,312, filed January 31, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a sulfide-containing solid electrolyte having advantages in terms of ionic conductivity and thermal stability, etc., compared to liquid electrolytes or polymer / oxide-containing solid electrolytes, and more specifically, to a solid electrolyte for an all-solid-state battery capable of protecting from moisture by introducing a surfactant-like substance through a chemical reaction with the sulfide-containing solid electrolyte, and to an all-solid-state battery including the same.

[0003] The rise of electrified transportation continues, exemplified by the widespread adoption of electric vehicles (EVs) and the emergence of urban air mobility (UAM) vehicles. Simultaneously, demand for stationary energy storage systems, particularly in the residential and industrial sectors, powered by solar and wind power, is growing. This shift is driven in part by the urgent need to mitigate the negative environmental and climate impacts associated with conventional internal combustion engines and other non-renewable power generation. Consequently, the development of battery technologies that offer high energy density while ensuring enhanced safety has become essential.

[0004] From the perspective of limitations related to battery capacity, safety, output, large-scale development, and miniaturization, various batteries that can overcome the limitations of lithium secondary batteries are currently being studied.

[0005] Ongoing research focuses on various types of batteries. These include metal-air batteries with high theoretical capacities and all-solid-state batteries, which are safe and do not pose an explosion risk. Furthermore, for power output, supercapacitors are being explored. For larger scale, sodium sulfate batteries or redox flow batteries (RFBs) are being explored. For miniaturization, thin-film batteries are being explored.

[0006] Among these, all-solid-state batteries are those in which the liquid electrolytes used in conventional lithium secondary batteries are replaced with solid electrolytes. Such all-solid-state batteries are safer because they do not use flammable solvents, eliminating the risk of fire or explosion caused by the decomposition of conventional electrolytes. These all-solid-state batteries have the advantage of improving the low stability, energy density, and long-life issues of liquid electrolytes used in lithium-ion batteries (LIBs). Furthermore, because all-solid-state batteries can use lithium metal or a lithium alloy as anode materials, they can have the advantage of dramatically improving the energy density of the battery.

[0007] Meanwhile, the solid electrolytes of these all-solid-state batteries can be broadly classified into organic (polymer-containing) solid electrolytes and inorganic solid electrolytes. Among these, inorganic solid electrolytes can be divided into sulfide-containing and oxide-containing solid electrolytes. In addition, the solid electrolyte on which technological development is focused is the sulfide-containing solid electrolyte, and development is underway to achieve an ionic conductivity close to that of organic electrolytes. Thus, among the solid electrolytes, the sulfide-containing solid electrolyte is ranked 10th. -3 S / cm to 10 -2Not only does it have high ionic conductivity of S / cm, but it also has excellent thermal stability and ductility, so it has the advantage of interfacial compatibility, which is advantageous in improving resistance by making good contact with the interface.

[0008] However, sulfide-containing solid electrolytes are sensitive to moisture, generating, for example, toxic gases belonging to the H2S (hydrogen sulfide) series upon contact with moisture, necessitating the establishment of a very dry environment during the manufacture of batteries or electrodes. The present invention aims to provide a specific and practical solution to this problem.

[0009] Accordingly, the purpose of the present invention is to provide a solid electrolyte for an all-solid-state battery and an all-solid-state battery including the same, which can protect from moisture by introducing a substance of the surfactant concept through a chemical reaction with a sulfide-containing solid electrolyte.

[0010] To achieve the above purpose, the present invention provides a solid electrolyte for an all-solid-state battery, the surface of which is modified with an amphiphilic compound having a hydrophilic group and a hydrophobic group.

[0011] In addition, the present invention provides an all-solid-state battery comprising a positive electrode; a negative electrode; and a solid electrolyte for the all-solid-state battery.

[0012] Therefore, the solid electrolyte for an all-solid-state battery according to the present invention and the all-solid-state battery including the same have the advantage of being able to protect the sulfide-containing solid electrolyte from moisture by introducing a substance of the surfactant concept through a chemical reaction with the sulfide-containing solid electrolyte.

[0013] FIG. 1 is an image showing the structure of an amphiphilic compound included in a solid electrolyte for an all-solid-state battery according to one embodiment of the present invention. FIG. 1 (a) is an image showing that the amphiphilic compound is classified into a hydrophilic site and a hydrophobic site, and FIG. 1 (b) is an image of one exemplary amphiphilic compound.

[0014] Figure 2 is an XRD graph showing the difference in structural stability between a solid electrolyte according to the present invention and a conventional solid electrolyte depending on moisture exposure.

[0015] Figure 3 is an XRD graph showing the difference in structural stability according to moisture exposure (air exposure) of a typical solid electrolyte.

[0016] Figure 4 is a graph showing the difference in ionic conductivity between a solid electrolyte according to the present invention and a conventional solid electrolyte depending on moisture exposure (air exposure).

[0017] Figure 5 is a graph showing the difference in ionic conductivity between a solid electrolyte according to the present invention and a conventional solid electrolyte depending on moisture exposure (air exposure).

[0018] Figure 6 is a graph showing the difference in ionic conductivity according to moisture exposure (air exposure) of a typical solid electrolyte.

[0019] Hereinafter, the present invention will be described in detail.

[0020] The solid electrolyte for an all-solid-state battery according to the present invention is surface-modified with an amphiphilic compound having a hydrophilic group and a hydrophobic group, and specifically, is surface-modified with an amphiphilic compound having a hydrophilic group on one side and a hydrophobic group on the other side, and is characterized in that the hydrophilic group is bonded.

[0021] One aspect of the present invention relates to a solid electrolyte for an all-solid-state battery comprising a solid electrolyte and a modified layer on a surface of the solid electrolyte, wherein the modified layer comprises an amphiphilic compound, and the amphiphilic compound comprises at least one hydrophilic group and at least one hydrophobic group.

[0022] In another embodiment of the present invention, the solid electrolyte comprises a sulfide-containing solid electrolyte. In another embodiment, the solid electrolyte comprises a bond between a hydrophilic group of an amphiphilic compound and the surface of the sulfide-containing solid electrolyte.

[0023] In another embodiment of the present invention, the hydrophilic group of the amphiphilic compound is at least one selected from the group consisting of a thiol group, an amine group, an isocyanate group, and an ethoxysilyl group.

[0024] In another embodiment of the present invention, the hydrophobic group of the amphiphilic compound is a hydrocarbon group substituted with a fluorine or organosilicon compound.

[0025] In another embodiment of the present invention, the amphiphilic compound is a perfluorothiol-containing compound. In another embodiment, the perfluorothiol-containing compound is a C1 to C30 aliphatic or aromatic hydrocarbon substituted with 1 to 20 fluorine atoms and 1 to 5 thiol groups.

[0026] In an embodiment of the present invention, the perfluorothiol-containing compound is a C8-C12 hydrocarbon substituted with 15 to 20 fluorine atoms and 1 to 3 thiol groups.

[0027] In another embodiment, the perfluorothiol-containing compound is a C10 hydrocarbon substituted with 17 fluorines and 1 thiol group. For example, the perfluorothiol-containing compound is CF3(CF2)7(CH2)2SH. This structure is also known as CAS No: 34143-74-3 (1H,1H,2H,2H-perfluorodecanethiol).

[0028] In an embodiment of the present invention, the sulfide-containing solid electrolyte comprises Li6PS5Cl.

[0029] In another embodiment of the present invention, the content of the amphiphilic compound is 5 to 30 wt% based on 100 wt% of the solid electrolyte for an all-solid-state battery.

[0030] In another embodiment of the present invention, the thickness of the modified layer comprising the amphiphilic compound is from 0.1 μm to 3 μm. In other embodiments, the thickness is from 0.1 μm to 1 μm, or from 0.3 μm to 0.5 μm.

[0031] In another aspect, the hydrophilic group of the perfluorothiol-containing compound is bonded to the solid electrolyte, and the hydrophobic group of the perfluorothiol-containing compound is positioned at the outermost portion of the solid electrolyte.

[0032] In an embodiment of the present invention, the present invention relates to an all-solid-state battery comprising a positive electrode, a negative electrode, and a solid electrolyte disclosed herein.

[0033] In an embodiment of the present invention, the solid electrolyte is positioned as a film having a layered structure between the positive electrode and the negative electrode. Alternatively, or additionally, the solid electrolyte is mixed with and contained in one or both of the positive electrode active material and the negative electrode active material.

[0034] In another embodiment of the present invention, the all-solid-state battery may be a semi-solid battery additionally comprising a liquid electrolyte.

[0035] solid electrolyte

[0036] The solid electrolyte for an all-solid-state battery according to the present invention may include a sulfide-containing solid electrolyte as a parent material. In addition, the solid electrolyte for an all-solid-state battery according to the present invention is characterized in that the surface of the parent material is surface-modified with an amphiphilic compound having a hydrophilic group on one side and a hydrophobic group on the other side, and the hydrophilic group of the amphiphilic compound is bonded to the surface of the parent material. In other words, the solid electrolyte for an all-solid-state battery is characterized in that it may include a sulfide-containing solid electrolyte as a parent material, and the surface of the parent material is modified with an amphiphilic compound.

[0037] The parent material, for example, a sulfide-containing solid electrolyte, may contain a lithium salt, and the lithium salt may be an ionizable lithium salt such as Li + X - It can be expressed as . The anion of these lithium salts is not particularly limited, but F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - ,　 CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN- and (CF3CF2SO2)2N - Examples thereof include, but are not limited to, sulfide-containing electrolytes. For the purposes of the present invention, any suitable sulfide-based electrolyte material may be used. The term "sulfide-containing electrolyte" as used herein refers to an electrolyte containing ions (e.g., Li + ) and an electrolyte suitable for electrically insulating the positive and negative electrodes of an electrochemical cell. Exemplary sulfide-containing electrolytes are described in the literature [Shaojie Chenet al., "Sulfide solid electrolytes for all-solid-state lithium batteries: Structure, conductivity, stability and application," Energy Storage Materials, Volume 14, Pages 58-74 (September 2018), which is expressly incorporated herein by reference in its entirety.

[0038] For example, many sulfide-containing electrolyte materials have superionic conductivity (~10 -2 S cm -1 It is receiving special attention due to its high ionic conductivity and deformability. In particular, Li3P7S 11 , Li 10 GeP2S 12 , and Na3PS4 and Li6PS5Cl have been reported to exhibit high ionic conductivities; some even approach the ionic conductivities of liquid electrolytes. According to an embodiment of the present invention, the sulfide solid electrolyte material also provides a low Young's modulus, which is advantageous for forming a favorable interfacial contact with the electrode material by simple cold pressing at room temperature.

[0039] The sulfide-containing solid electrolyte contains sulfur (S) and has the ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and may include a Li-PS-based glass, a Li-PS-based glass ceramic, and an argyrodite-based sulfide-containing solid electrolyte. Non-limiting examples of such sulfide-containing solid electrolytes include one or more of Li2S-P2S5, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-LiCl-P2S5, Li2S-Li2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2O5, Li2S-P2S5-SiS2, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2, Li2S-GeS2-ZnS, or Li6PS5X (X = at least one of Cl, Br or I). In addition, the sulfide-containing solid electrolyte included as a base material in the solid electrolyte for the all-solid-state battery of the present invention is not limited thereto, and may include any known sulfide-containing solid electrolyte.

[0040] The base material constituting the solid electrolyte for an all-solid-state battery of the present invention, i.e., the sulfide-containing solid electrolyte, preferably comprises a LPSCl (lithium phosphate sulfur chloride) compound, and more preferably comprises Li6PS5Cl, which is preferable in terms of serving as a transport layer for ion movement by redox reaction. In addition, the base material constituting the solid electrolyte for an all-solid-state battery of the present invention, i.e., the sulfide-containing solid electrolyte, may be more preferably composed of Li6PS5Cl.

[0041] The amphiphilic compound located on the surface of the above-mentioned parent material has a hydrophilic group on one side and a hydrophobic group on the other side, and the hydrophilic group of the amphiphilic compound binds to the surface of the parent material (for example, S of Li6PS5Cl and S among the thiol groups of the amphiphilic compound form an SS bond due to strong bonding E). In other words, the hydrophilic group of the amphiphilic compound acts as a linker that mediates the parent material and the hydrophobic group of the amphiphilic compound. Therefore, the hydrophobic group of the amphiphilic compound does not come into contact with the parent material. In addition, the solid electrolyte includes a bond between the hydrophilic group of the amphiphilic compound and the surface of the sulfide-containing solid electrolyte.

[0042] In the above amphiphilic compound, the hydrophilic group may be selected from the group consisting of a thiol group, an amine group, an isocyanate group, and a suitable leaving group, for example, an ethoxysilyl group (e.g., triethoxysilyl or trimethoxysilyl), but is not limited thereto. However, a thiol group capable of forming an SS bond with a sulfide-containing solid electrolyte (parent material) is most preferable as the hydrophilic group of the amphiphilic compound. Accordingly, other hydrophilic groups containing a sulfur atom can also be applied as the hydrophilic group of the amphiphilic compound, but in this case, a thiol group is most preferable.

[0043] The term "thiol" may be understood as an organosulfur compound of the form R-SH, where R represents an alkyl or other organic substituent. The term "isocyanate" may be understood as a functional group of the formula RN=C=O, where R may be an alkyl group or an aryl group.

[0044] The term "amine" may be understood as a compound or functional group containing a basic nitrogen atom with a lone pair of electrons. Amines are formally derivatives of ammonia (NH3) in which one or more hydrogen atoms are replaced by a substituent such as an alkyl group or an aryl group (e.g., alkylamines and arylamines). The substituent -NH2 is referred to as an amino group. In certain embodiments, amines may include primary amines, secondary amines, and / or tertiary amines. In certain embodiments, the amino group may further be converted into a useful leaving group, for example, by conversion to an ammonium salt, an aryl(sulfonyl)amino group.

[0045] And, in the amphiphilic compound, the hydrophobic group is a hydrocarbon group substituted with fluorine or an organosilicon compound (e.g., silane, alkoxy silane, isocyanate). Here, the hydrophilic group is positioned in a substituted state on a carbon atom included in the hydrophobic group. According to an embodiment of the present invention, the total number of carbons (including chains and substituents) may be 6 to 16 carbons, or according to some embodiments of the present invention, 6 to 12 carbons, 8 to 12 carbons, or 10 to 12 carbons. A hydrocarbon group can have a total of 6 carbons, 7 carbons, 8 carbons, 9 carbons, 10 carbons, 11 carbons, 12 carbons, 13 carbons, 14 carbons, 15 carbons, 16 carbons, 17 carbons, 18 carbons, 19 carbons, or 20 carbons.

[0046] For example, the hydrocarbon group includes substituted or unsubstituted n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, isopentyl, n-hexyl, isohexyl, sec-hexyl, tert-hexyl, n-heptyl, isoheptyl, sec-heptyl, tert-heptyl, n-octyl, isooctyl, sec-octyl, tert-octyl, n-nonyl, isononyl, sec-nonyl, tert-nonyl, n-decyl, isodecyl, sec-decyl, tert-decyl, n-undecyl, isoundecyl, sec-undecyl, tert-undecyl, n-dodecyl, isododecyl, sec-dodecyl, tert-dodecyl, etc. It may be an unrestricted substituted or unsubstituted C3-C20 alkyl group.

[0047] The hydrophilic and hydrophobic groups are positioned separately in a single compound, thereby forming a hydrophilic site and a hydrophobic site, respectively. FIG. 1 is an image showing the structure of an amphiphilic compound included in a solid electrolyte for an all-solid-state battery according to an embodiment of the present invention. FIG. 1 (a) is an image showing that the amphiphilic compound is classified into a hydrophilic site and a hydrophobic site, and FIG. 1 (b) is an image showing this in more detail.

[0048] As an example of the bonding relationship between the above-described parent material and amphiphilic compound, as an embodiment, a hydrophilic thiol group and a hydrophobic fluorine-substituted hydrocarbon group may be sequentially connected and positioned from the surface of the parent material (e.g., LPSCl-based compound) toward the outside thereof. However, as described above, the present invention is not limited thereto. In addition, the amphiphilic compound illustrated in (b) of FIG. 1 is a perfluorothiol-containing compound, and various perfluorothiol-containing compounds can be exemplified as the amphiphilic compound of the present invention.

[0049] More specifically, in embodiments of the present invention, the perfluorothiol-containing compound may be a C1 to C30, preferably C3 to C20, and more preferably C7 to C15 aliphatic or aromatic hydrocarbon substituted with 1 to 20, preferably 5 to 20, more preferably 8 to 18 fluorines and 1 to 5, preferably 1 to 3 thiol groups. In embodiments of the present invention, any fluorine substitution may be in the range of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 and 20. In embodiments of the present invention, any thiol groups may be in the range of 1, 2, 3, 4 and 5.

[0050] The content of the amphiphilic compound located on the surface of the above-mentioned base material may be 5 to 30 wt%, preferably 10 to 20 wt%, and more preferably 13 to 18 wt%, based on 100 wt% of the solid electrolyte for an all-solid-state battery of the present invention. In an embodiment of the present invention, the content of the amphiphilic compound located on the surface of the above-mentioned base material may be any range of wt% taken from data points of 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, and 30, based on 100 wt% of the solid electrolyte for an all-solid-state battery of the present invention. If the content of the amphiphilic compound is less than 5 wt% based on 100 wt% of the solid electrolyte for the all-solid-state battery of the present invention, it may be difficult to protect the sulfide-containing solid electrolyte from moisture. In addition, if the content of the amphiphilic compound exceeds 30 wt% based on 100 wt% of the solid electrolyte for the all-solid-state battery of the present invention, the problem of a significant decrease in the ionic conductivity of the sulfide-containing solid electrolyte may occur.

[0051] In addition, the thickness of the amphiphilic compound layer (or modified layer including the amphiphilic compound) located on the surface of the above-mentioned parent material may be 0.1 µm to 3 µm, preferably 0.1 µm to 1 µm, and more preferably 0.3 µm to 0.5 µm. In an embodiment of the present invention, the thickness of the amphiphilic compound layer may be in μm in any range taken from the data points of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, and 3.0. If the thickness of the amphiphilic compound layer is less than 0.1 μm, it may not function properly as a moisture protection layer, and thus the moisture protection effect may be reduced. In addition, if the thickness of the amphiphilic compound layer exceeds 3 μm, the amphiphilic compound layer may rather interfere with lithium ion transfer, which may significantly reduce the ion conductivity of the sulfide-containing solid electrolyte.

[0052] The solid electrolyte for all-solid-state batteries described above can protect the parent material (sulfide-containing solid electrolyte) from moisture because its outer surface is hydrophobic. In other words, the present invention is significant in that it not only protects the parent material from moisture by introducing a surfactant-like substance to the surface of the parent material, but also maximizes the moisture protection effect by further enhancing hydrophobicity.

[0053] All-solid-state batteries

[0054] Next, an all-solid-state battery (including a solid electrolyte for an all-solid-state battery) according to the present invention will be described. The all-solid-state battery includes a positive electrode, a negative electrode, and the solid electrolyte for an all-solid-state battery described herein.

[0055] The above solid electrolyte may be independently positioned without being mixed with the electrodes (i.e., positioned as a layered film between the positive and negative electrodes), may be positioned mixed with at least one of the positive active material and the negative active material, or may be positioned with all of them, as long as it does not adversely affect the performance of the battery.

[0056] These solid electrolytes can perform the same functions as separators in conventional lithium secondary batteries (i.e., electrically insulating the positive and negative electrodes while simultaneously allowing lithium ions to pass through). Alternatively, the all-solid-state battery can be utilized as a semi-solid battery, including a liquid electrolyte if necessary. In this case, a separate polymer separator may be required. A conventional liquid electrolyte can be selected.

[0057] The positive electrode includes a positive electrode active material layer including an active material, a conductive material, and a binder in the form of granules, etc. In addition, the positive electrode includes a current collector if necessary, and the positive electrode active material layer can be positioned on at least one surface of the current collector.

[0058] As the positive electrode active material, any material that can be used as a positive electrode active material of a conventional lithium ion secondary battery can be used without limitation. In addition, the positive electrode active material may be a lithium transition metal oxide containing one or more transition metals. For example, the positive electrode active material may be LiCoO2, LiNiO2, LiMnO2, Li2MnO3, LiMn2O4, Li(Ni a Co b Mn c )O2(0 <a<1, 0<b<1, 0<c<1, a+b+c=1), LiNi 1-y Co y O2(O <y<1), LiCo 1-y Mn y O2, LiNi 1-y Mn y O2(O <y<1), Li(Ni a Co b Mnc )O4(0 <a<2, 0<b<2, 0<c<2, a+b+c=2), LiMn 2-z Ni z O4(0 <z<2), LiMn 2-z Co z O4(0 <z<2), 및 이의 조합으로 이루어진 군으로부터 선택되는 것일 수 있다.

[0059] The above-mentioned positive electrode conductive material may also be used without limitation as long as it can be used as a positive electrode conductive material of a conventional lithium ion secondary battery. For example, the positive electrode conductive material may be a conventional material such as carbon nanotubes (single-walled carbon nanotubes, multi-walled carbon nanotubes) or carbon black. In some embodiments of the present invention, the conductive material may be selected from the group consisting of graphite, carbon black, carbon fibers or metal fibers, metal powder, conductive whiskers, conductive metal oxides, activated carbon, or polyphenylene derivatives. More specifically, the positive electrode conductive material may be natural graphite, artificial graphite, super-p TM (super-p TM ), acetylene black, ketjen black TM (ketjen black TM ), channel black, furnace black, lamp black, thermal black, Denka black TM (denka black TM ), at least one conductive material selected from the group consisting of aluminum powder, nickel powder, zinc oxide, potassium titanate, and titanium oxide.

[0060] The above-mentioned positive electrode binder is mixed with the positive electrode active material and the positive electrode conductive material to bind each component and help particle growth. The binder may be an organic binder, and the organic binder means a binder that is dissolved or dispersed in an organic solvent, particularly N-methylpyrrolidone (NMP), and is distinguished from an aqueous binder that uses water as a solvent or dispersion medium. For example, the binder may be selected from the group consisting of polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polyimide, polyamideimide, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber, and fluororubber, but is not limited thereto. In addition, the weight ratio of the positive electrode active material, positive electrode conductive material, and binder included in the positive electrode also applies to the conventional one.

[0061] The above-described collector is not limited to a specific type and may include those having high conductivity without causing chemical changes in the battery, for example, stainless steel, copper, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel having a surface treated with carbon, nickel, titanium, and silver.

[0062] The above-described negative electrode may include a negative electrode active material layer comprising a negative electrode active material usable in a conventional lithium ion secondary battery. The negative electrode active material may be combined with a conductive material and / or a binder as described herein with respect to the positive electrode active material layer. Additionally, the negative electrode may include a current collector, if necessary, and the negative electrode active material layer may be positioned on at least one surface of the current collector.

[0063] For example, the negative active material is carbon such as non-graphitizable carbon, graphitic carbon, etc.; Li x Fe2O3(0≤x≤1), Lix WO2(0≤x≤1), Sn x Me 1-x Me' y O z (Me: Mn,Fe,Pb,Ge; Me': Al, B, P, Si, elements of group 1, group 2, group 3 of the periodic table, halogen; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 규소계 합금; 주석계 합금; SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4및 Bi2O5등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni계 재료; 티타늄 산화물; 리튬 티타늄 산화물; 등에서 선택된 어느 하나 이상을 포함한 것일 수 있다.

[0064] In addition, the present invention provides a battery module including the all-solid-state battery as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source. 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.

[0065] Hereinafter, preferred embodiments are presented to help understand the present invention, but these are only illustrative of the present invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and technical idea of ​​the present invention, and it is also natural that such changes and modifications fall within the scope of the appended patent claims.

[0066] [Example 1] Preparation of surface-modified solid electrolyte

[0067] First, Li6PS5Cl (manufactured by NEI) as a base material and perfluorothiol having a hydrophilic group (thiol group) and a hydrophobic group (fluorine-substituted hydrocarbon group) were prepared. The perfluorothiol compound was the same as that exemplified in Fig. 1 (b) (also known as CAS No: 34143-74-3 (1H,1H,2H,2H-perfluorodecanethiol)). Each of these samples was processed in a glove box with an oxygen level of less than 0.5 ppm. Next, Li6PS5Cl and perfluorothiol were placed in a Thinky Mixer at a weight ratio of 5:1 and reacted at 25°C for 20 minutes at 2,000 rpm to modify the surface of Li6PS5Cl. At this time, the hydrophilic group of perfluorothiol was chemically bonded with Li6PS5Cl, and the hydrophobic group of perfluorothiol was positioned at the outermost outer side of Li6PS5Cl.

[0068] [Comparative Example 1] Conventional solid electrolyte

[0069] A conventional solid electrolyte (Li6PS5Cl) without surface modification was prepared.

[0070] [Comparative Example 2] Conventional solid electrolyte

[0071] The surface of Li6PS5Cl was simply coated with sulfosuccinic acid ester salt (anionic surfactant).

[0072] [Experimental Example 1] Evaluation of the structural stability of solid electrolytes

[0073] The structural stability of Li6PS5Cl was evaluated after exposing the solid electrolytes of Example 1, Comparative Examples 1 and 2 to moisture at 25°C and a relative humidity of 25%. Fig. 2 is an XRD graph showing the difference in structural stability of the solid electrolyte according to the present invention and a conventional solid electrolyte upon exposure to moisture (exposure to air), and Fig. 3 is an XRD graph showing the difference in structural stability of a conventional solid electrolyte upon exposure to moisture (exposure to air).

[0074] As illustrated in FIG. 2, it was confirmed that the surface-modified solid electrolyte of Example 1 ('Perfluoro Thiol (no air)' and 'Perfluoro Thiol (1 day air)' in FIG. 2) showed little change in the structure of Li6PS5Cl even in a moisture exposure environment. On the other hand, the solid electrolyte of Comparative Example 1 (Li6PS5Cl, 'Pristine LPSCl' and 'Air exposed LPSCl (1 day air)') without surface modification showed no small structural changes. In addition, as illustrated in FIG. 3, it was confirmed that the solid electrolyte of Comparative Example 2, which was prepared by simply coating the surface of Li6PS5Cl with a sulfosuccinic acid ester salt (diethylhexyl sodium sulfosuccinate), also showed no small structural changes. Through this, it can be seen that protection from moisture is possible when the surface of the base material (sulfide-containing solid electrolyte) is modified with an amphiphilic compound as in the present invention.

[0075] [Experimental Example 2] Evaluation of the ionic conductivity of solid electrolytes

[0076] The solid electrolytes of Example 1, Comparative Examples 1 and 2 were exposed to moisture at 25°C and a relative humidity of 25%, and then the ionic conductivity of Li6PS5Cl was measured. Figures 4 and 5 are graphs showing the difference in ionic conductivity of the solid electrolyte according to the present invention and a conventional solid electrolyte depending on moisture exposure (air exposure), and Figure 6 is a graph showing the difference in ionic conductivity of a conventional solid electrolyte depending on moisture exposure (air exposure).

[0077] As illustrated in FIGS. 4 and 5, the solid electrolyte of surface-modified Example 1 ('Perfluoro Thiol (no air)' and 'Perfluoro Thiol (1 day air)' in FIGS. 4 and 5) was confirmed to maintain ionic conductivity of up to about 1 mS / cm even after moisture exposure. On the other hand, the solid electrolyte of Comparative Example 1 without surface modification (Li6PS5Cl, 'Pristine LPSCl' and 'LPSCl (24 hr air)') was confirmed to have ionic conductivity that dropped to 0 mS / cm. In addition, as illustrated in FIG. 6, the solid electrolyte of Comparative Example 2, which was prepared by simply coating the surface of Li6PS5Cl with a sulfosuccinic acid ester salt (Diethylhexyl sodium sulfosuccinate), exhibited higher ionic conductivity than the solid electrolyte of Comparative Example 1, but lower ionic conductivity than the solid electrolyte of Example 1.

Claims

1. A solid electrolyte comprising a sulfide-containing solid electrolyte; and A modified layer comprising a hydrophilic compound and positioned on the surface of the solid electrolyte; The hydrophilic compound comprises at least one hydrophilic group and at least one hydrophobic group, The hydrophilic group of the hydrophilic compound is at least one selected from the group consisting of a thiol group, an amine group, an isocyanate group, and an ethoxysilyl group, A solid electrolyte for an all-solid-state battery, wherein the hydrophobic group of the hydrophilic compound is a hydrocarbon group substituted with a fluorine or organic silicon compound.

2. A solid electrolyte for an all-solid-state battery, characterized in that the solid electrolyte comprises a bond between a hydrophilic group of the hydrophilic compound and a surface of the sulfide-containing solid electrolyte according to claim 1.

3. A solid electrolyte for an all-solid-state battery, characterized in that the hydrophilic compound in claim 1 is a perfluorothiol-containing compound.

4. A solid electrolyte for an all-solid-state battery, characterized in that the perfluorothiol-containing compound in claim 3 is a C1 to C30 aliphatic or aromatic hydrocarbon substituted with 1 to 20 fluorine atoms and 1 to 5 thiol groups.

5. A solid electrolyte for an all-solid-state battery, characterized in that the perfluorothiol-containing compound in claim 4 is a C8 to C12 hydrocarbon substituted with 15 to 20 fluorine atoms and 1 to 3 thiol groups.

6. A solid electrolyte for an all-solid-state battery, characterized in that in claim 4, the perfluorothiol-containing compound is a C10 hydrocarbon substituted with 17 fluorine groups and 1 thiol group.

7. A solid electrolyte for an all-solid-state battery, characterized in that in claim 4, the perfluorothiol-containing compound is CF3(CF2)7(CH2)2SH.

8. A solid electrolyte for an all-solid-state battery, characterized in that the sulfide-containing solid electrolyte according to claim 1 comprises Li6PS5Cl.

9. A solid electrolyte for an all-solid-state battery, characterized in that the content of the hydrophilic compound in claim 1 is 5 to 30 wt% based on 100 wt% of the solid electrolyte for an all-solid-state battery.

10. A solid electrolyte for an all-solid-state battery, characterized in that the thickness of the modified layer including the hydrophilic compound in claim 1 is 0.1 ㎛ to 3 ㎛.

11. A solid electrolyte for an all-solid-state battery, characterized in that the thickness of the modified layer including the hydrophilic compound in claim 1 is 0.1 ㎛ to 1 ㎛.

12. A solid electrolyte for an all-solid-state battery, characterized in that the thickness of the modified layer including the hydrophilic compound in claim 1 is 0.3 µm to 0.5 µm.

13. A solid electrolyte for an all-solid-state battery, characterized in that, in claim 3, the hydrophilic group of the perfluorothiol-containing compound is bonded to the solid electrolyte, and the hydrophobic group of the perfluorothiol-containing compound is located at the outermost outer side of the solid electrolyte.

14. An all-solid-state battery comprising a positive electrode; a negative electrode; and a solid electrolyte for the all-solid-state battery of claim 1.

15. An all-solid-state battery according to claim 14, characterized in that the solid electrolyte is positioned as a film having a layered structure between the positive electrode and the negative electrode.

16. An all-solid-state battery according to claim 14, characterized in that the solid electrolyte is mixed and included in one or both of the positive electrode active material and the negative electrode active material.

17. An all-solid-state battery according to claim 14, characterized in that the all-solid-state battery is a semi-solid-state battery additionally including a liquid electrolyte.

18. A battery module including an all-solid-state battery, The above all-solid-state battery includes a positive electrode, a negative electrode, and a solid electrolyte membrane interposed therebetween, The solid electrolyte film comprises a solid electrolyte including a sulfide-containing solid electrolyte; and a modified layer located on the surface of the solid electrolyte and including a hydrophilic compound; The hydrophilic compound comprises at least one hydrophilic group and at least one hydrophobic group, The hydrophilic group of the hydrophilic compound is at least one selected from the group consisting of a thiol group, an amine group, an isocyanate group, and an ethoxysilyl group, A battery module wherein the hydrophobic group of the hydrophilic compound is a hydrocarbon group substituted with a fluorine or organic silicon compound.

19. An electric vehicle comprising a battery module including an all-solid-state battery, The above all-solid-state battery comprises a positive electrode, a negative electrode, and a solid electrolyte membrane interposed therebetween, The solid electrolyte film comprises a solid electrolyte including a sulfide-containing solid electrolyte; and a modified layer located on the surface of the solid electrolyte and including a hydrophilic compound; The hydrophilic compound comprises at least one hydrophilic group and at least one hydrophobic group, The hydrophilic group of the hydrophilic compound is at least one selected from the group consisting of a thiol group, an amine group, an isocyanate group, and an ethoxysilyl group, An electric vehicle, wherein the hydrophobic group of the hydrophilic compound is a hydrocarbon group substituted with a fluorine or organic silicon compound.

20. An electric vehicle according to claim 19, characterized in that the electric vehicle is selected from the group consisting of an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), an electric two-wheeler, and an electric golf cart.

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