Positive electrode active material for all-solid-state battery, positive electrode and all-solid-state battery

Abstract

The present invention relates to a cathode active material for an all-solid-state battery, a cathode, and an all-solid-state battery including the same. More specifically, the cathode active material according to the present invention has a particle layer formed on its surface, the particle layer being coated with lithium titanium oxide particles, and the particle layer prevents side reactions between the cathode active material and sulfide-based solid electrolyte particles in the cathode, thereby enabling stable charging and discharging of the all-solid-state battery.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0141761, filed October 23, 2023, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a positive electrode active material for an all-solid-state battery, a positive electrode, and an all-solid-state battery including the same. [Background technology]

[0003] Currently, various batteries that can overcome the limitations of lithium secondary batteries are being researched from the viewpoints of battery capacity, safety, output, size increase, and miniaturization.

[0004] Academia and industry are currently conducting ongoing research into metal-air batteries, which have a much larger theoretical capacity than lithium secondary batteries, all-solid-state batteries, which are safe and do not pose a risk of explosion, supercapacitors, NaS batteries or RFBs (redox flow batteries), which are large-sized batteries, and thin film batteries, which are ultra-small.

[0005] Among various next-generation batteries, all-solid-state batteries are those that replace the liquid electrolyte used in conventional lithium secondary batteries with a solid electrolyte. Because they do not use flammable solvents, they are completely free of fires and explosions caused by decomposition reactions of conventional electrolytes, significantly improving safety. Furthermore, among all-solid-state batteries, technological development is progressing on sulfide-based all-solid-state batteries, which have high ionic conductivity and can theoretically achieve a high energy density of over 900 Wh / L. Here, sulfide-based all-solid-state batteries refer to all-solid-state batteries that contain a sulfide-based solid electrolyte.

[0006] In all-solid-state battery systems, lithium ion conduction does not occur due to the liquid electrolyte found in conventional lithium-ion batteries (LIBs). Therefore, when manufacturing a cathode for a sulfide-based all-solid-state battery, sulfide-based solid electrolyte particles must be added to the cathode to increase the contact interface between the cathode active material and the sulfide-based solid electrolyte particles, thereby enhancing lithium ion conduction. Furthermore, to improve energy density, it is necessary to promote physical contact between the cathode active material, sulfide-based solid electrolyte particles, and other battery elements within the cathode, and reduce the porosity of the cathode after rolling. This reduction must be maintained during charging and discharging.

[0007] However, in a sulfide-based all-solid-state battery cathode, the potential difference between the cathode active material and sulfide-based solid electrolyte particles can cause a chemical reaction even when they are in physical contact with each other. Furthermore, side reactions can occur at the interface between the cathode active material and sulfide-based solid electrolyte particles, resulting in problems such as the consumption of active lithium and increased resistance.

[0008] For this reason, there is a continuing need for technological development that can prevent side reactions that occur due to physical contact between the positive electrode active material and sulfide-based solid electrolyte particles in the positive electrode of a sulfide-based all-solid-state battery. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-224307 Summary of the Invention [Problem to be solved by the invention]

[0010] As a result of extensive research into solving the above problem, the inventors of the present invention have found that Li4Ti5O 12 The particles were coated with Li4Ti5O 12a particle layer, and when the positive electrode active material and sulfide-based solid electrolyte particles are in physical contact with each other in the positive electrode, the Li4Ti5O 12 It was confirmed that the particle layer can prevent side reactions between the positive electrode active material and sulfide-based solid electrolyte particles, thereby enabling stable charge and discharge.

[0011] Therefore, an object of the present invention is to provide a positive electrode active material having a particle layer formed on the surface thereof, which prevents side reactions when it comes into physical contact with sulfide-based solid electrolyte particles.

[0012] Another object of the present invention is to provide a positive electrode including a positive electrode active material having a particle layer formed on the surface thereof, which prevents side reactions when the positive electrode active material comes into physical contact with sulfide-based solid electrolyte particles.

[0013] Another object of the present invention is to provide an all-solid-state battery capable of stable charging and discharging, which includes a cathode active material having a particle layer formed on the surface thereof, which prevents side reactions upon physical contact with sulfide-based solid electrolyte particles. [Means for solving the problem]

[0014] In order to achieve the above object, the present invention provides a positive electrode active material for an all-solid-state battery, which comprises a lithium titanium oxide particle layer on a surface thereof, wherein the lithium titanium oxide particle layer has a shape in which a plurality of lithium titanium oxide particles are continuously or discontinuously formed on the surface of the positive electrode active material.

[0015] The present invention also provides a positive electrode active material for an all-solid-state battery, wherein the lithium titanium oxide is represented by the following chemical formula 1: <Chemical formula 1> Li x Ti y O z In the above Chemical Formula 1, 0.5≦x≦5, 1≦y≦5, and 2≦z≦12.

[0016] The present invention also provides a positive electrode active material for an all-solid-state battery, wherein the particles have one or more shapes selected from the group consisting of spherical and polygonal shapes.

[0017] The present invention also provides a positive electrode active material for an all-solid-state battery, wherein the lithium titanium oxide particles have a particle size of 10 nm or more and 1 μm or less.

[0018] The present invention also provides a positive electrode active material for an all-solid-state battery, wherein the lithium titanium oxide particles are contained in an amount of 5 wt % or less based on the total weight of the positive electrode active material.

[0019] The present invention also provides a cathode active material for an all-solid-state battery, the cathode active material having a BET specific surface area of ​​0.4 m 2 / g or more 1m 2 / g or less.

[0020] The present invention also provides a positive electrode active material for an all-solid-state battery, wherein the positive electrode active material contains at least one oxide selected from the group consisting of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium copper oxide, and vanadium oxide.

[0021] The present invention also provides a positive electrode for an all-solid-state battery, comprising the positive electrode active material, sulfide-based solid electrolyte particles, a conductive material, and a binder.

[0022] The present invention also provides a positive electrode for an all-solid-state battery, wherein the sulfide-based solid electrolyte is represented by the following chemical formula 2: <Chemical formula 2> L a M b P c S d X e In the above Chemical Formula 2, L is an element selected from the group consisting of alkali metals; M is an element selected from the group consisting of B, Al, Ga, In, Si, Ge, Sn, Pb, As, Sb, Bi, Ti, V, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, and W; X is an element selected from the group consisting of F, Cl, Br, I, and O, and 0≦a≦12, 0≦b≦6, 0≦c≦6, 0 <d≦12であり、0≦e≦9である。

[0023] The present invention also provides a positive electrode for an all-solid-state battery, wherein the conductive material comprises at least one material selected from the group consisting of vapor-grown carbon fiber (VGCF), graphite, carbon black, fluorocarbon, metal powder, conductive whisker, conductive metal oxide, and conductive polymer.

[0024] The present invention also provides a positive electrode for an all-solid-state battery, wherein the binder comprises at least one selected from the group consisting of polytetrafluoroethylene (PTFE), polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene.

[0025] The present invention also provides an all-solid-state battery comprising the positive electrode, the negative electrode, and a solid electrolyte membrane interposed therebetween. [Effects of the Invention]

[0026] According to the cathode active material for an all-solid-state battery of the present invention, the lithium titanium oxide particle layer formed on the cathode active material can prevent damage to the cathode active material and can prevent side reactions between the cathode active material and sulfide-based solid electrolyte particles in the cathode.

[0027] In addition, an all-solid-state battery including the cathode active material on which the lithium titanium oxide particle layer is formed can be stably charged and discharged because side reactions between the cathode active material and sulfide-based solid electrolyte particles are prevented. [Brief explanation of the drawings]

[0028] [Figure 1] FIG. 1 is a diagram showing a part of a cross section of a positive electrode active material for an all-solid-state battery according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention will now be described in further detail to aid in its understanding.

[0030] The terms and phrases used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term in order to best explain his / her invention.

[0031] [Cathode active material for all-solid-state batteries] The present invention relates to a positive electrode active material for an all-solid-state battery.

[0032] The positive electrode active material for an all-solid-state battery according to the present invention includes a lithium titanium oxide particle layer on the surface thereof, and the lithium titanium oxide particle layer has a shape in which a plurality of lithium titanium oxide particles are continuously or discontinuously formed on the surface of the positive electrode active material.

[0033] FIG. 1 is a diagram showing a part of a cross section of a positive electrode active material for an all-solid-state battery according to one embodiment of the present invention.

[0034] 1, a lithium titanium oxide particle layer 20 is formed on the surface of a positive electrode active material 10. When applied to a positive electrode and present together with sulfide-based solid electrolyte particles 30, the lithium titanium oxide particle layer 20 acts as a buffer layer to prevent side reactions between them.

[0035] The lithium titanium oxide particle layer 20 can be manufactured by a dry process without using a separate solvent, and the lithium titanium oxide particles may remain in their particle form within the coating layer. Therefore, the surface of the lithium titanium oxide particle layer 20 may have a shape in which the particles are connected continuously or discontinuously. The particles refer to small objects having physical and chemical properties.

[0036] The shape of the particles may be one or more selected from the group consisting of spherical and polygonal shapes.

[0037] The polygon may be one or more selected from the group consisting of a triangle, a square, a pentagon, a hexagon, a heptagon, and an octagon.

[0038] Therefore, the surface of the lithium titanium oxide particle layer may have a shape in which curved portions having the shape of a part of a sphere and / or polygonal portions having the shape of a part of a polygon are connected continuously and / or discontinuously.

[0039] In one embodiment of the present invention, the lithium titanium oxide (LTO) may be represented by the following formula 1: <Chemical formula 1> Li x Ti y O z In the above Chemical Formula 1, 0.5≦x≦5, 1≦y≦5, and 2≦z≦12.

[0040] In addition, from the viewpoint of electrochemical stability, the lithium titanium oxide is preferably Li4Ti5O 12 may be.

[0041] In one embodiment of the present invention, the particle diameter of the lithium titanium oxide particles may be 10 nm or more and 1 μm or less.

[0042] Specifically, the particle size of the lithium titanium oxide particles may be 10 nm or more, 30 nm or more, or 50 nm or more, or 0.5 μm or less, 0.8 μm or less, or 1 μm or less. If the particle size is less than 10 nm, the interface resistance may increase or the dispersibility may decrease, and if it exceeds 1 μm, the coverage of the coating layer may decrease.

[0043] In one embodiment of the present invention, the lithium titanium oxide particles may be contained in an amount of 5 wt% or less based on the total weight of the positive electrode active material, where the total weight of the positive electrode active material means the total weight of the positive electrode active material on which the lithium titanium oxide particle layer is formed.

[0044] Specifically, the content of the lithium titanium oxide particles may be 5 wt% or less, 4 wt% or less, 3 wt% or less, 2 wt% or less, or 1 wt% or less. If the content of the lithium titanium oxide particles exceeds 5 wt%, the charge transfer resistance between the positive electrode and the sulfide-based solid electrolyte particles may increase. In addition, the lower limit of the content range of the lithium titanium oxide particles is not particularly limited and may be, for example, 0.1 wt%.

[0045] In one embodiment of the present invention, when the lithium titanium oxide particle layer is formed, the BET specific surface area of ​​the positive electrode active material for an all-solid-state battery is 0.4 m 2 / g or more 1m 2 / g or less.

[0046] Specifically, the BET specific surface area of ​​the positive electrode active material for the all-solid-state battery is 0.4 m 2 / g or more, 0.5m 2 / g or more or 0.6m 2 / g or more, and 2 / g or less, 0.9m 2 / g or less, 0.8m 2 / g or less or 0.7m 2 If the BET specific surface area of ​​the positive electrode active material for an all-solid-state battery is less than the above range, the effect of preventing a side reaction between the positive electrode active material and sulfide-based solid electrolyte particles in the positive electrode may be reduced, and if the BET specific surface area exceeds the above range, the positive electrode active material may act as a resistor when the battery is operating.

[0047] In one embodiment of the present invention, 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 (LiCoO), lithium nickel oxide (LiNiO), Li[Ni x Co y Mn z M v ]O2 (wherein M is any one or more elements selected from the group consisting of Al, Ga, and In, and 0.3≦x<1.0, 0≦y, z≦0.5, 0≦v≦0.1, and x+y+z+v=1), Li (Li a M b-a-b’ M' b’ )O 2-c A c(wherein 0≦a≦0.2, 0.6≦b≦1, 0≦b'≦0.2, 0≦c≦0.2, M includes Mn and one or more selected from the group consisting of Ni, Co, Fe, Cr, V, Cu, Zn, and Ti, M' is one or more selected from the group consisting of Al, Mg, and B, and A is one or more selected from the group consisting of P, F, S, and N), or compounds substituted with one or more transition metals, such as compounds of the formula Li 1+y Mn 2-y O4 (where y is 0 or more and 0.33 or less), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2, lithium copper oxide (Li2CuO2), vanadium oxides such as LiV3O8, LiFe3O4, V2O5, and Cu2V2O7, and vanadium oxides with the chemical formula LiNi 1-y M y O2 (where M=Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and y is 0.01 or more and 0.3 or less), Ni-site type lithium nickel oxide, chemical formula LiMn 2-y M y Examples of suitable lithium manganese composite oxides include, but are not limited to, lithium manganese composite oxides represented by Li2Mn3MO8 (where M is Co, Ni, Fe, Cr, Zn, or Ta, and y is 0.01 or more and 0.1 or less) or Li2Mn3MO8 (where M is Fe, Co, Ni, Cu, or Zn), LiMn2O4 in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion, disulfide compounds, and Fe2(MoO4)3.

[0048] The positive electrode active material for an all-solid-state battery as described above can prevent damage to the positive electrode active material due to the lithium titanium oxide particle layer formed on the surface.

[0049] Furthermore, when the cathode active material having the lithium titanium oxide particle layer formed thereon is used in the cathode of an all-solid-state battery, it can prevent side reactions with sulfide-based solid electrolyte particles contained in the cathode. That is, the lithium titanium oxide particle layer acts as a buffer layer between the cathode active material and the sulfide-based solid electrolyte particles, preventing side reactions and thereby stably charging and discharging the all-solid-state battery.

[0050] Furthermore, even when the surface of the positive electrode active material is coated with the lithium titanium oxide particles, the bulk structure of the positive electrode active material remains unchanged, thereby achieving stable electrochemical performance. Generally, if a problem occurs during the coating process of the positive electrode active material, the bulk structure of the positive electrode active material may change. For example, the bulk structure may change to a rock salt structure, which may result in a decrease in lithium mobility within the positive electrode active material. However, in the present invention, the bulk structure of the positive electrode active material can be stably maintained even when the lithium titanium oxide particles are coated.

[0051] Furthermore, in the present invention, the problem of particles falling off from the lithium titanium oxide particle layer does not occur, and therefore the reliability of the product can be improved.

[0052] [Method of manufacturing positive electrode active material for all-solid-state batteries] The present invention also relates to a method for producing a positive electrode active material for an all-solid-state battery.

[0053] The method for producing a positive electrode active material for an all-solid-state battery according to the present invention includes the steps of: (S1) mixing a positive electrode active material and lithium titanium oxide particles; (S2) heating the mixture and then cooling it; Includes:

[0054] The manufacturing method may be carried out by a dry process using no solvent, or by a wet process in which the particles are dispersed in a solvent in step (S1) and then mixed.

[0055] Hereinafter, the method for producing a positive electrode active material for an all-solid-state battery will be described in more detail for each step.

[0056] In one embodiment of the present invention, in the step (S1), the positive electrode active material and lithium titanium oxide particles may be mixed.

[0057] The types and contents of the positive electrode active material and the lithium titanium oxide particles are the same as those described above.

[0058] Alternatively, the lithium titanium oxide particles may be dispersed in a solvent and then mixed. The solvent is not particularly limited as long as it can stably disperse the lithium titanium oxide particles. For example, the solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methyl-2-pyrrolidone (NMP), acetone, or water. These may be used alone or in combination.

[0059] In one embodiment of the present invention, in step (S2), the mixture may be heated and then cooled to coat the surface of the positive electrode active material with lithium titanium oxide particles.

[0060] The heating temperature may be 150°C or higher and 300°C or lower. If the heating temperature is lower than 150°C, the adhesive strength between the lithium titanium oxide particles and the adhesive strength of the lithium titanium oxide particles to the surface of the positive electrode active material may be reduced, and if the heating temperature exceeds 300°C, lithium on the surface of the positive electrode active material may be deintercalated by the high-temperature heat treatment. Specifically, the heating temperature may be 150°C or higher, 160°C or higher, 170°C or higher, or 180°C or higher, or 220°C or lower, 240°C or lower, 260°C or lower, 280°C or lower, or 300°C or lower.

[0061] Furthermore, when the heated lithium-titanium oxide particle layer is cooled, the adhesion of the lithium-titanium oxide particle layer can be further improved, and the durability of the positive electrode active material itself can also be enhanced. For example, the cooling temperature may be 10°C or higher and 30°C or lower.

[0062] [Cathode for all-solid-state batteries] The present invention relates to a positive electrode for an all-solid-state battery.

[0063] The positive electrode for an all-solid-state battery according to the present invention includes a positive electrode active material, sulfide-based solid electrolyte particles, a binder, and a conductive material.

[0064] In one embodiment of the present invention, the positive electrode may be in a collector-free form. In this case, a positive electrode active material layer containing the positive electrode active material, sulfide-based solid electrolyte particles, a binder, and a conductive material may itself be the positive electrode.

[0065] The positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on one surface of the positive electrode current collector. The positive electrode active material layer may include the positive electrode active material, sulfide-based solid electrolyte particles, a conductive material, and a binder.

[0066] The positive electrode current collector supports the positive electrode active material layer and serves to transfer electrons between an external conductor and the positive electrode active material layer.

[0067] The positive electrode current collector is not particularly limited as long as it does not cause a chemical change in the all-solid-state battery and has high electrical conductivity. For example, the positive electrode current collector may be made of stainless steel, aluminum, nickel, titanium, palladium, baked carbon, stainless steel surface-treated with carbon, nickel, silver, or the like, or an aluminum-cadmium alloy.

[0068] The positive electrode current collector may have a finely textured surface or a three-dimensional porous structure to strengthen the bonding strength with the positive electrode active material layer, and may have various forms such as a film, sheet, foil, mesh, net, porous body, foam, or nonwoven fabric.

[0069] In one embodiment of the present invention, the positive electrode active material is a positive electrode active material having a lithium titanium oxide particle layer formed on the surface thereof, as described above.

[0070] The positive electrode active material is as described above.

[0071] The positive electrode active material may be included in an amount of 55 wt% to 90 wt% based on the total weight of the positive electrode active material layer. Specifically, the content of the positive electrode active material may be 55 wt% to 60 wt% or 65 wt% or more, or 83 wt% to 85 wt% or 90 wt% or less. If the content of the positive electrode active material is less than 55 wt%, battery performance may be reduced, and if it exceeds 90 wt%, mass transfer resistance may be increased.

[0072] In one embodiment of the present invention, the sulfide-based solid electrolyte particles may be included in the positive electrode to improve ionic conductivity.

[0073] The sulfide-based solid electrolyte may be represented by the following chemical formula 2: <Chemical formula 2> L a M b P c S d X e In the above Chemical Formula 2, L is an element selected from the group consisting of alkali metals; M is an element selected from the group consisting of B, Al, Ga, In, Si, Ge, Sn, Pb, As, Sb, Bi, Ti, V, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, and W; X is an element selected from the group consisting of F, Cl, Br, I, and O; and 0≦a≦12, 0≦b≦6, 0≦c≦6, 0 <d≦12であり、0≦e≦9である。

[0074] For example, the sulfide-based solid electrolyte may be Li6PS5Cl, Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (where m and n are positive numbers, and Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, and In), Li 10 GeP2S 12 It may contain one or more selected from the group consisting of:

[0075] The sulfide-based solid electrolyte particles may be included in an amount of 10 wt % to 50 wt % based on the total weight of the positive electrode active material layer. Specifically, the content of the sulfide-based solid electrolyte may be 10 wt % or more, 20 wt % or more, or 30 wt % or more, or 40 wt % to 45 wt % or less, or 50 wt % or less. If the content of the sulfide-based solid electrolyte particles is less than 10 wt %, the effect of improving ion conductivity may be negligible. If the content of the sulfide-based solid electrolyte particles is more than 50 wt %, the content of the positive electrode active material, binder, or conductive material may be relatively reduced, which may result in reduced battery performance.

[0076] In one embodiment of the present invention, the binder may be included to assist bonding between materials included in the positive electrode active material layer and bonding between the positive electrode active material layer and the positive electrode current collector.

[0077] The binder may include one or more selected from the group consisting of polytetrafluoroethylene (PTFE), polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene. Preferably, the binder may include polytetrafluoroethylene (PTFE).

[0078] The binder may be included in an amount of 0.1 wt % to 3 wt % based on the total weight of the positive electrode active material layer. Specifically, the binder content may be 0.1 wt % to 0.5 wt %, or 0.8 wt % or more, or 1.5 wt %, 2 wt %, or 3 wt % or less. If the binder content is less than 0.1 wt %, the effect of improving the bonding strength between materials included in the positive electrode active material layer is negligible, and the electrode sheet may not be properly formed. If the binder content exceeds 3 wt %, the ionic conductivity or electrical conductivity may be reduced.

[0079] In one embodiment of the present invention, the conductive material may be included in the positive electrode to improve electrical conductivity.

[0080] 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 include graphite or conductive carbon, such as graphite (e.g., natural graphite, artificial graphite, etc.); carbon black (e.g., acetylene black, ketjen black, denka black, thermal black, channel black, furnace black, lamp black, summer black, etc.); carbon-based materials with a graphene or graphite crystalline structure; conductive fibers (e.g., carbon fiber, metal fiber, etc.); carbon fluoride; metal powder (e.g., aluminum powder, nickel powder, etc.); conductive whiskers (e.g., zinc oxide, potassium titanate, etc.); conductive oxides (e.g., titanium oxide, etc.); and conductive polymers (e.g., polyphenylene derivatives), which may be used alone or in combination. Preferably, the conductive material may include vapor-grown carbon fiber (VGCF).

[0081] The conductive material may be included in an amount of 0.1 wt % to 5 wt % based on the total weight of the positive electrode active material layer. Specifically, the content of the conductive material may be 0.1 wt % or more, 0.5 wt % or more, 1 wt % or more, 1.5 wt % or more, or 2 wt % or more, or 4 wt % or less, 4.5 wt % or less, or 5 wt % or less. If the content of the conductive material is too low, such as less than 0.1 wt %, the effect of improving electrical conductivity may not be expected or the electrochemical properties of the battery may be reduced. If the content of the conductive material is too high, such as more than 5 wt %, the amount of positive electrode active material may be relatively small, and the capacity and energy density may be reduced.

[0082] [All-solid battery] The present invention also relates to an all-solid-state battery comprising the solid electrolyte membrane.

[0083] The all-solid-state battery according to the present invention includes the positive electrode, the negative electrode, and a sulfide-based solid electrolyte membrane interposed therebetween. The positive electrode is as described above.

[0084] In one embodiment of the present invention, the negative electrode may include a negative electrode active material layer, and the negative electrode active material layer may be formed on one surface of a negative electrode current collector.

[0085] The negative electrode active material layer may include a negative electrode active material, a conductive material, and a binder, or may be an anodeless layer.

[0086] In the negative electrode active material layer, the negative electrode active material is lithium (Li + The lithium ion-containing compound may include a material capable of reversible intercalation or deintercalation of lithium ions, a material capable of reversibly reacting with lithium ions to form a lithium-containing compound, lithium metal, or a lithium alloy.

[0087] The lithium ion (Li + The material capable of reversibly inserting or de-inserting lithium ions (Li) may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. + The material capable of reacting with lithium (Li) to reversibly form a lithium-containing compound may be, for example, tin oxide, titanium nitrate, or silicon. The lithium alloy may be, for example, an alloy of lithium (Li) and a metal selected from the group consisting of indium (In), 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).

[0088] Preferably, the negative electrode active material may be lithium metal or a lithium-indium alloy (Li-In), and specifically, may be in the form of lithium metal, a lithium thin film, or a lithium-indium alloy thin film or powder.

[0089] The negative electrode active material may be included in an amount of 40 wt % 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 % to 50 wt % or 70 wt % to 80 wt %. If the content of the negative electrode active material is less than 40 wt %, the connectivity between the wet negative electrode active material layer and the dry negative electrode active material layer may be insufficient, and if the content is more than 80 wt %, mass transfer resistance may be increased.

[0090] The binder may be a component that assists in binding the negative electrode active material to the conductive material and the like and in binding the negative electrode current collector, and may be any of the following: styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylic The binder may include one or more selected from the group consisting of lylonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene. Preferably, the binder may include polytetrafluoroethylene (PTFE).

[0091] The binder may be included in an amount of 0.5 wt % to 4 wt % based on the total weight of the negative electrode active material layer. Specifically, the binder content may be 0.5 wt % to 1 wt %, or 1.5 wt % or more, or 3 wt %, 3.5 wt %, or 4 wt % or less. If the binder content is less than 0.5 wt %, the adhesive strength between the positive electrode active material and the negative electrode current collector may be reduced. If the binder content exceeds 4 wt %, the adhesive strength is improved, but the content of the negative electrode active material may be reduced accordingly, which may reduce the battery capacity.

[0092] 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 include graphite or conductive carbon, such as graphite (e.g., natural graphite, artificial graphite, etc.); carbon black (e.g., carbon black, acetylene black, ketjen black, denka black, thermal black, channel black, furnace black, lamp black, summer black, etc.); carbon-based materials with a graphene or graphite crystalline structure; conductive fibers (e.g., carbon fiber, metal fiber, etc.); carbon fluoride; metal powder (e.g., aluminum powder, nickel powder, etc.); conductive whiskers (e.g., zinc oxide, potassium titanate, etc.); conductive oxides (e.g., titanium oxide, etc.); and conductive polymers (e.g., polyphenylene derivatives). These may be used alone or in combination. Preferably, the conductive material may include vapor-grown carbon fiber (VGCF).

[0093] The conductive material may typically be included in an amount of 1 wt % to 5 wt % based on the total weight of the positive electrode active material layer. Specifically, the conductive material content may be 1 wt % to 1.5 wt %, or 2 wt % or more, or 4 wt %, 4.5 wt %, or 5 wt % or less. If the conductive material content is too low, such as less than 1 wt %, the improvement in electrical conductivity may not be expected or the electrochemical characteristics of the battery may be degraded. If the conductive material content is too high, such as more than 5 wt %, the amount of negative electrode active material may be relatively small, resulting in reduced capacity and energy density. The method for incorporating the conductive material into the negative electrode is not particularly limited, and may be a conventional method known in the art, such as mixing or coating with the negative electrode active material.

[0094] The negative electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and is conductive, and may be, for example, copper, stainless steel, aluminum, nickel, titanium, baked carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like, an aluminum-cadmium alloy, etc. Similarly to the positive electrode current collector, the negative electrode current collector may be in various forms such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric having fine irregularities formed on the surface.

[0095] The method for manufacturing the negative electrode is not particularly limited, and the negative electrode may be manufactured by forming a negative electrode active material layer on a negative electrode current collector using a layer or film formation method commonly used in the art. For example, methods such as compression bonding, coating, and vapor deposition may be used. In addition, the negative electrode of the present invention also includes a case where 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 the metal plate by initial charging.

[0096] The anode-free layer refers to an anode layer in which, at the time of initial assembly of the battery, lithium metal or a lithium alloy, which serves as a lithium supply source among the anode active materials, is not present in the anode, but lithium is deposited in the anode upon charging. A battery including the anode-free layer can also be called an anode-free battery.

[0097] In the anode-free battery, during charging and discharging of the battery, lithium ions released from the positive electrode migrate to the negative electrode to form a negative electrode active material layer. For example, during charging of the battery, lithium ions are released from the positive electrode active material and then migrate to the negative electrode side to become lithium metal composed purely of lithium, which may form a layered lithium metal layer on the negative electrode current collector, or may form a lithium metal structure of any shape other than a layer. The arbitrary shape may be, for example, a structure in which lithium metal is aggregated into particles.

[0098] In one embodiment of the present invention, the sulfide-based solid electrolyte contained in the sulfide-based solid electrolyte layer may be represented by the following Chemical Formula 2: <Chemical formula 2> L a M b P c S d X e In the above Chemical Formula 1, L is an element selected from the group consisting of alkali metals; M is an element selected from the group consisting of B, Al, Ga, In, Si, Ge, Sn, Pb, As, Sb, Bi, Ti, V, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, and W; X is an element selected from the group consisting of F, Cl, Br, I, and O; and 0≦a≦12, 0≦b≦6, 0≦c≦6, 0 <d≦12であり、0≦e≦9である。

[0099] For example, the sulfide-based solid electrolyte may be Li6PS5Cl, Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Zm S n (where m and n are positive numbers, and Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, and In), Li 10 GeP2S 12 It may contain one or more selected from the group consisting of:

[0100] However, the sulfide-based solid electrolyte is not limited to these, and a wide range of sulfide-based solid electrolytes commonly used in the art may be used.

[0101] [Battery module] The present invention also relates to 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.

[0102] Specific examples of the device 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.

[0103] Preferred examples will be described below to aid in understanding the present invention. However, the following examples are merely illustrative of the present invention, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope of the scope and technical idea of ​​the present invention. Naturally, such changes and modifications also fall within the scope of the appended claims.

[0104] In the following Examples and Comparative Examples, positive electrode active materials, positive electrodes containing the same, and all-solid-state batteries were manufactured as shown in Table 1 below.

[0105] [Table 1]

[0106] [Example 1] [1-1. Production of a positive electrode active material having a lithium titanium oxide particle layer formed on its surface] As shown in Table 1, a mixture was obtained by mixing 99% by weight of the positive electrode active material and 1% by weight of lithium titanium oxide. The lithium titanium oxide used had a particle size of 50 nm.

[0107] The mixture was heated to a temperature of 200° C. and then cooled, and the surface of the positive electrode active material was coated with lithium titanium oxide particles to form a lithium titanium oxide particle layer.

[0108] [1-2. Manufacturing of positive electrodes] The cathode active material with the lithium titanium oxide particle layer formed thereon, sulfide-based solid electrolyte particles, conductive material, and binder were mixed in a weight ratio of 83.8:14.8:0.2:1.2 and then powder mixed. Specifically, the cathode active material and sulfide-based solid electrolyte Li6PS5Cl were measured in powder form and mixed for 15 minutes using a blade mixer in a dry room environment to obtain a mixture. Next, vapor-grown carbon fiber (VGCF) powder, a conductive material, was measured and added to the mixture and mixed. PTFE (Polytetrafluoroethylene) powder, a binder, was measured and further mixed to obtain a mixed powder.

[0109] The mixed powder was put into a mortar, and then fiberized in the mortar, followed by calendering with a roller to obtain a fiber strength of 6 mAh / cm 2 A positive electrode of loading was prepared.

[0110] [1-3. All-solid-state battery] The positive electrode, sulfide-based solid electrolyte film (Li6PS5Cl), and negative electrode (lithium metal) were sequentially stacked, and then pressurized at 100 MPa to produce an all-solid-state battery.

[0111] [Example 2] The same method as in Example 1 was carried out, except that the heat treatment temperature was set to 500°C after mixing the positive electrode active material and the lithium titanium oxide particles.

[0112] [Example 3] The same procedure as in Example 1 was carried out, except that the particle size of the lithium titanium oxide particles was set to 2 μm.

[0113] [Example 4] The same procedure as in Example 1 was carried out, except that the weight of the lithium titanium oxide particles was 10% by weight.

[0114] [Experimental Example 1: Performance evaluation of all-solid-state batteries] The performance of the all-solid-state batteries manufactured in the examples and comparative examples was evaluated.

[0115] The rate characteristics (capacity capability) of the all-solid-state battery were observed through a protocol in which the battery was activated for two cycles at 0.05 C in a charger / discharger and then discharged up to 1 C. Specifically, the rate characteristics were observed through a protocol in which the battery was charged at 0.05 C CC / CV (Constant Current / Constant Voltage), discharged at 0.05 C CC (Constant Current) for two cycles, and then discharged at 0.1 C / 0.2 C / 0.33 C / 0.5 C / 1 C CC while maintaining the 0.1 C CC / CV charging process.

[0116] Table 2 below shows the performance evaluation results of all-solid-state batteries.

[0117] [Table 2]

[0118] Referring to Table 2, Example 1 is excellent in all of the initial coulombic efficiency, capacity retention at 100 cycles, and capacity retention at 1C.

[0119] On the other hand, it was found that in Examples 2 to 4, compared to Example 1, the initial coulombic efficiency, the capacity retention rate at 100 cycles, and the capacity retention rate at 1C were all relatively low.

[0120] Example 2 was heat-treated at a high temperature, and the initial coulomb efficiency and capacity retention rate were relatively decreased due to degradation of the positive electrode active material that occurred at high temperatures.

[0121] In addition, in Example 3, the particle size of the lithium titanium oxide particles was somewhat large, which reduced the coverage of the positive electrode active material surface and prevented the side reactions occurring at the interface between the positive electrode active material and the solid electrolyte particles from being suppressed, resulting in a relative decrease in the initial coulombic efficiency and capacity retention.

[0122] In addition, in Example 4, since the content of lithium titanium oxide particles was relatively high, excessive coverage of the positive electrode surface reduced the interfacial conductivity, resulting in low initial coulombic efficiency and low capacity retention at 1C. [Explanation of symbols]

[0123] 10: Positive electrode active material 20: Lithium titanium oxide particle layer 30: Sulfide solid electrolyte particles

Claims

1. A positive electrode active material for an all-solid-state battery comprising a lithium titanium oxide particle layer on a surface thereof, The lithium titanium oxide particle layer has a shape in which a plurality of lithium titanium oxide particles are continuously or discontinuously formed on a surface of the positive electrode active material for an all-solid-state battery.

2. The positive electrode active material for an all-solid-state battery according to claim 1, wherein the lithium titanium oxide is represented by the following chemical formula 1: <Chemical formula 1> Li ｘ Ti ｙ O ｚ In the formula 1, 0.5≦x≦5, 1≦y≦5, and 2≦z≦12.

3. 2. The positive electrode active material for an all-solid-state battery according to claim 1, wherein the shape of the lithium titanium oxide particles is at least one selected from the group consisting of spherical and polygonal.

4. 2. The positive electrode active material for an all-solid-state battery according to claim 1, wherein the particle diameter of the lithium titanium oxide particles is 10 nm or more and 1 μm or less.

5. 2. The positive electrode active material for an all-solid-state battery according to claim 1, wherein the lithium titanium oxide particles are contained in an amount of 5 wt% or less based on the total weight of the positive electrode active material for an all-solid-state battery.

6. The BET specific surface area of ​​the positive electrode active material for an all-solid-state battery is 0.4 m ２ / g or more 1m ２ The positive electrode active material for an all-solid-state battery according to claim 1 , wherein the SiO 2 content is 0.15 / g or less.

7. 2. The positive electrode active material for an all-solid-state battery according to claim 1, wherein the positive electrode active material for an all-solid-state battery comprises at least one selected from the group consisting of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium copper oxide, and vanadium oxide.

8. A positive electrode for an all-solid-state battery, comprising the positive electrode active material according to any one of claims 1 to 7, sulfide-based solid electrolyte particles, a conductive material, and a binder.

9. The sulfide-based solid electrolyte is the positive electrode for an all-solid-state battery according to claim 8, characterized in that it is represented by the following chemical formula 2: <Chemical formula 2> L ａ M ｂ P ｃ S ｄ X ｅ In the above Chemical Formula 2, L is an element selected from the group consisting of alkali metals; M is an element selected from the group consisting of B, Al, Ga, In, Si, Ge, Sn, Pb, As, Sb, Bi, Ti, V, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, and W; X is an element selected from the group consisting of F, Cl, Br, I, and O; and 0≦a≦12, 0≦b≦6, 0≦c≦6, 0<d≦12, and 0≦e≦9.

10. 9. The positive electrode for an all-solid-state battery according to claim 8, wherein the conductive material comprises at least one selected from the group consisting of vapor-grown carbon fiber (VGCF), graphite, carbon black, fluorocarbon, metal powder, conductive whisker, conductive metal oxide, and conductive polymer.

11. The binder may be polytetrafluoroethylene (PTFE), polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate copolymer ...

9. The positive electrode for an all-solid-state battery according to claim 8, characterized in that it contains one or more selected from the group consisting of cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene.

12. An all-solid-state battery comprising the positive electrode, the negative electrode and a sulfide-based solid electrolyte film interposed therebetween according to claim 8.

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