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

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 priority under Korean Patent Application No. 10-2023-0141761 dated October 23, 2023, and all content disclosed in the documents of said Korean Patent Application is 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 containing the same. [Background technology]

[0003] From the perspectives of battery capacity, safety, output, scaling up, and miniaturization, various types of batteries are currently being researched that can overcome the limitations of lithium-ion secondary batteries.

[0004] Typically, metal-air batteries, which have a much larger theoretical capacity than lithium-ion batteries; all-solid-state batteries, which pose no risk of explosion in terms of safety; supercapacitors, which offer high output; NaS batteries or RFB (redox flow batteries), which can be scaled up; and thin-film batteries, which are being miniaturized, are all the technologies that are being continuously researched in academia and industry.

[0005] Among various next-generation batteries, all-solid-state batteries refer to batteries that replace the liquid electrolyte used in conventional lithium-ion secondary batteries with a solid electrolyte. Because they do not use flammable solvents in the battery, they completely eliminate the risk of ignition or explosion due to the decomposition reaction of conventional electrolytes, thus 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 in the solid electrolyte and can theoretically achieve high energy densities of 900 Wh / L or more. Here, sulfide-based all-solid-state batteries refer to all-solid-state batteries that contain a sulfide-based solid electrolyte.

[0006] In a all-solid-state battery system, lithium-ion conduction by a liquid electrolyte contained in a conventional lithium-ion battery (LIB) does not occur. Therefore, when manufacturing a positive electrode for a sulfide-based all-solid-state battery, it is necessary to add sulfide-based solid electrolyte particles inside the positive electrode to increase the contact interface between the positive electrode active material and the sulfide-based solid electrolyte particles and increase the conduction of lithium ions. Further, in order to improve the energy density, it is necessary to promote the physical contact between the positive electrode active material, the sulfide-based solid electrolyte particles, and other battery elements inside the positive electrode and reduce the porosity of the positive electrode after rolling, which must be maintained even during charge and discharge.

[0007] However, in a positive electrode for a sulfide-based all-solid-state battery, due to the energy level difference between the positive electrode active material and the sulfide-based solid electrolyte particles, a chemical reaction may occur even only by their physical contact. Further, side reactions occur at the interface between the positive electrode active material and the sulfide-based solid electrolyte particles, and there are problems such as not only the consumption of active lithium but also an increase in resistance.

[0008] Therefore, in the positive electrode of a sulfide-based all-solid-state battery, the need for technological development to prevent side reactions generated by physical contact between the positive electrode active material and the sulfide-based solid electrolyte particles has been continuously raised.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] As a result of conducting extensive research to solve the above problems, the inventors coated the surface of the positive electrode active material with Li4Ti5O 12 particles to form Li4Ti5O 12A particle layer is formed, and when the positive electrode active material and sulfide-based solid electrolyte particles come into physical contact within the positive electrode, the Li4Ti5O 12 We confirmed that the particle layer can prevent side reactions between the positive electrode active material and the sulfide-based solid electrolyte particles, thereby enabling stable charging and discharging.

[0011] Therefore, an object of the present invention is to provide a positive electrode active material in which a particle layer is formed on the surface, thereby preventing side reactions during physical contact with sulfide-based solid electrolyte particles.

[0012] Another object of the present invention is to provide a positive electrode containing a positive electrode active material on which a particle layer is formed on the surface, thereby preventing side reactions during physical contact with sulfide-based solid electrolyte particles.

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

[0014] To achieve the above objective, the present invention provides a positive electrode active material for an all-solid-state battery comprising a lithium titanium oxide particle layer on its surface, 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 all-solid-state batteries, characterized in that the lithium titanium oxide is represented by the following chemical formula 1: <Chemical formula 1> Li x Ti y O z In the aforementioned 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, characterized in that the shape of the particles is one or more 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, characterized in that the particle size of the lithium titanate particles is 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, characterized in that the lithium titanate particles are contained at 5% by weight or less based on the total weight of the positive electrode active material.

[0019] The present invention also provides a positive electrode active material for an all-solid-state battery, characterized in that the BET specific surface area of the positive electrode active material is 0.4 m 2 / g or more and 1 m 2 / g or less.

[0020] The present invention also provides a positive electrode active material for an all-solid-state battery, characterized in that the positive electrode active material contains one or more 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, characterized in that 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 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, characterized in that the conductive material comprises one or more selected from the group consisting of vapor-grown carbon fiber (VGCF), graphite, carbon black, fluorinated carbon, 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, characterized in that the binder comprises 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, carboxymethylcellulose, hydroxypropylcellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethylsucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene.

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

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

[0027] Furthermore, in an all-solid-state battery containing a positive electrode active material on which the lithium titanium oxide particle layer is formed, stable charging and discharging is possible because side reactions between the positive electrode active material and sulfide-based solid electrolyte particles are prevented. [Brief explanation of the drawing]

[0028] [Figure 1] This figure shows a portion of a cross-section of a positive electrode active material for an all-solid-state battery according to one embodiment of the present invention. [Modes for carrying out the invention]

[0029] The present invention will be described in more detail below to aid in understanding the present invention.

[0030] The terms and words used in this specification and in the claims shall not be interpreted in a manner limited to their ordinary or lexicographical meanings, but rather in a manner consistent with the technical idea of ​​the present invention, based on the principle that inventors may appropriately define the concepts of terms in order to best describe their invention.

[0031] [Cathode active material for all-solid-state batteries] This invention relates to a positive electrode active material for all-solid-state batteries.

[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 its surface, 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.

[0033] Figure 1 shows a portion of the cross-section of a positive electrode active material for an all-solid-state battery according to one embodiment of the present invention.

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

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

[0036] The shape of the particle may be one or more selected from the group consisting of spheres and polygons.

[0037] The aforementioned polygon may be one or more selected from the group consisting of triangles, quadrilaterals, pentagons, hexagons, heptagons, and octagons.

[0038] Therefore, the surface of the lithium titanium oxide particle layer may have a shape in which curved portions having a spherical shape and / or polygonal portions having a polygonal shape 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 chemical formula 1: <Chemical formula 1> Li x Ti y O z In the aforementioned chemical formula 1, 0.5 ≤ x ≤ 5, 1 ≤ y ≤ 5, and 2 ≤ z ≤ 12.

[0040] Furthermore, from the standpoint of electrochemical stability, the lithium titanium oxide is preferably Li4Ti5O 12 That's fine.

[0041] In one embodiment of the present invention, the particle size 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, and may be 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 interfacial 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 present in an amount of 5% by weight or less based on the total weight of the positive electrode active material. In this case, 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 lithium titanium oxide particles may be 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, or 1% by weight or less. If the content of lithium titanium oxide particles exceeds 5% by weight, the charge transfer resistance between the positive electrode and the sulfide-based solid electrolyte particles may increase. Furthermore, the lower limit of the content range for lithium titanium oxide particles is not particularly limited and may be, for example, 0.1% by weight.

[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 the all-solid-state battery is 0.4 m². 2 / g or more 1m 2 It is also acceptable if it is less than or equal to / g.

[0046] Specifically, the BET specific surface area of ​​the positive electrode active material for the all-solid-state battery is 0.4 m². 2 / g or more, 0.5m 2 / g or more or 0.6m 2 It may be more than / g, 1m 2 / g or less, 0.9m 2 / g or less, 0.8m 2 / g or less or 0.7m 2 It may be less than or equal to / g. If the BET specific surface area of ​​the positive electrode active material for the all-solid-state battery is less than the range, the effect of preventing side reactions between the positive electrode active material and sulfide-based solid electrolyte particles in the positive electrode may decrease, and if it exceeds the range, it may act as resistance when the battery is operated.

[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 intercalating and releasing lithium ions, for example, lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), Li[Ni x Co y Mn z M v ]O2(In the above formula, M is one element selected from the group consisting of Al, Ga, and In, or two or more elements selected from these, and 0.3≦x<1.0, 0≦y, z≦0.5, 0≦v≦0.1, x+y+z+v=1), Li(Li a M b-a-b’ M' b’ )O 2-c A c(In the above formula, 0≦a≦0.2, 0.6≦b≦1, 0≦b'≦0.2, 0≦c≦0.2, M includes 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.) Layered compounds such as or compounds substituted with one or more transition metals, chemical formula Li 1+y Mn 2-y Lithium manganese oxides such as O4 (where y is between 0 and 0.33), LiMnO3, LiMn2O3, LiMnO2, lithium copper oxide (Li2CuO2), vanadium oxides such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7, and LiNi 1-y M y Lithium nickel oxide of the Ni site type, represented as O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and y is between 0.01 and 0.3), chemical formula LiMn 2-y M y Examples include, but are not limited to, lithium manganese composite oxides represented as O2 (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 alkaline earth metal ions, disulfide compounds, and Fe2(MoO4)3.

[0048] The positive electrode active material for all-solid-state batteries described above can be protected from damage by the lithium titanium oxide particle layer formed on its surface.

[0049] Furthermore, when the positive electrode active material on which the lithium titanium oxide particle layer is formed is applied to the positive electrode of an all-solid-state battery, side reactions with the sulfide-based solid electrolyte particles contained in the positive electrode can be prevented. In other words, the lithium titanium oxide particle layer acts as a buffer layer between the positive electrode active material and the sulfide-based solid electrolyte particles, preventing side reactions and thereby enabling stable charging and discharging of the all-solid-state battery.

[0050] Furthermore, even if the lithium titanium oxide particles are coated onto the surface of the positive electrode active material, the bulk structure of the positive electrode active material does not change, thus enabling stable electrochemical performance. Generally, if problems occur 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, in which case a problem may occur in which the mobility of lithium within the positive electrode active material decreases. However, in the present invention, even if the lithium titanium oxide particles are coated, the bulk structure of the positive electrode active material can be stably maintained.

[0051] Furthermore, in this invention, the problem of particles falling off the lithium titanium oxide particle layer does not occur, thus improving the reliability of the product.

[0052] [Method for 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 all-solid-state batteries.

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

[0054] The above manufacturing method may be carried out as a dry process without the use of a solvent, or as a wet process in which particles are dispersed in a solvent in step (S1) and then mixed.

[0055] The method for producing positive electrode active material for all-solid-state batteries will be described in more detail below, step by step.

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

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

[0058] Furthermore, the lithium titanium oxide particles may be dispersed in a solvent and then mixed. In this case, 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, and one of these alone or a mixture of two or more may be used.

[0059] In one embodiment of the present invention, in step (S2), the mixture can 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 between 150°C and 300°C. If the heating temperature is below 150°C, the adhesive strength between lithium titanium oxide particles and the adhesive strength of lithium titanium oxide particles to the surface of the positive electrode active material may decrease, and if it 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, and may be 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 between 10°C and 30°C.

[0062] [Cathode for all-solid-state batteries] This invention relates to a positive electrode for all-solid-state batteries.

[0063] The positive electrode for an all-solid-state battery according to the present invention comprises 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 current collector-free form. In this case, the positive electrode active material layer itself, which includes the positive electrode active material, sulfide-based solid electrolyte particles, binder, and conductive material, may be the positive electrode.

[0065] Furthermore, 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 plays a role in transferring electrons between the 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 chemical changes 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, calcined carbon, stainless steel surface-treated with carbon, nickel, silver, etc., or an aluminum-cadmium alloy.

[0068] The positive electrode current collector may have a fine uneven surface or a three-dimensional porous structure to enhance the bonding force with the positive electrode active material layer. As a result, the positive electrode current collector may include various forms such as film, sheet, foil, mesh, net, porous material, foam, and 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 its surface, as described above.

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

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

[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 aforementioned 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 electrolytes are 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, and 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, or In), Li 10 GeP2S 12 It may include one or more species selected from the group consisting of the following:

[0075] Furthermore, the sulfide-based solid electrolyte particles may be included in an amount of 10% to 50% by weight based on the total weight of the positive electrode active material layer. Specifically, the content of the sulfide-based solid electrolyte may be 10% or more by weight, 20% or more by weight, or 30% or more by weight, or 40% or less by weight, 45% or less by weight, or 50% or less by weight. If the content of the sulfide-based solid electrolyte particles is less than 10% by weight, the effect of improving ionic conductivity may be minimal, and if it exceeds 50% by weight, the content of the positive electrode active material, binder, or conductive material may decrease relatively, potentially degrading battery performance.

[0076] In one embodiment of the present invention, the binder may be included to assist in bonding between substances contained 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 contain 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, carboxymethylcellulose, hydroxypropylcellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethylsucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene. Preferably, the binder may contain polytetrafluoroethylene (PTFE).

[0078] Furthermore, the binder may be included in an amount of 0.1% by weight or more and 3% by weight or less based on the total weight of the positive electrode active material layer. Specifically, the binder content may be 0.1% by weight or more, 0.5% by weight or more, or 0.8% by weight or more, or 1.5% by weight or less, 2% by weight or less, or 3% by weight or less. If the binder content is less than 0.1% by weight, the effect of improving the bonding force between substances contained in the positive electrode active material layer will be negligible, and there is a possibility that the electrode sheet may not be properly formed. If it exceeds 3% by weight, there is a possibility that the ionic conductivity or electrical conductivity will decrease.

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

[0080] Furthermore, the conductive material is not particularly limited as long as it prevents side reactions in the internal environment of the all-solid-state battery, does not cause chemical changes in the battery, and has excellent electrical conductivity. Typically, graphite or conductive carbon may be used, for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, Denka black, thermal black, channel black, furnace black, lamp black, and summer black; carbon-based materials whose crystalline structure is graphene or graphite; conductive fibers such as carbon fibers and metal fibers; carbon fluoride; metal powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives; which may be used alone or in mixtures of two or more, but are not necessarily limited to these. Preferably, the conductive material may also contain vapor-grown carbon fiber (VGCF).

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

[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 a positive electrode, a negative electrode, and a sulfide-based solid electrolyte membrane interposed between them. The positive electrode is as described above.

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

[0085] The anode active material layer may include anode active material, a conductive material, and a binder. Alternatively, the anode active material layer may be an anodeless layer.

[0086] In the negative electrode active material layer, the negative electrode active material is lithium (Li + The material may include a substance that can be reversibly intercalated or deintercalated, a substance that can reversibly form a lithium-containing compound by reacting with lithium ions, lithium metal, or lithium alloy.

[0087] The aforementioned lithium ion (Li + The material that can reversibly insert or remove the lithium ion (Li) may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. + The substance that can reversibly form a lithium-containing compound by reacting with ) 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 lithium-indium alloy (Li-In), and specifically, it may be in the form of lithium metal, a lithium thin film, a lithium-indium alloy thin film, or powder.

[0089] The negative electrode active material may be present in an amount of 40% to 80% by weight based on the total weight of the negative electrode active material layer. Specifically, the content of the negative electrode active material may be 40% or more by weight, 50% or more by weight, 70% or less by weight, or 80% or less by weight. If the content of the negative electrode active material is less than 40% by weight, the connectivity between the wet negative electrode active material layer and the dry negative electrode active material layer may be insufficient, and if it exceeds 80% by weight, the mass transfer resistance may increase.

[0090] Furthermore, the binder contains components that assist in the bonding of the negative electrode active material to conductive materials and to the negative electrode current collector, such as styrene-butadiene rubber, acrylic styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile-butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, and polyacrylic. The binder may contain one or more selected from the group consisting of lilonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethylcellulose, hydroxypropylcellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethylsucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene. Preferably, the binder may contain polytetrafluoroethylene (PTFE).

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

[0092] Furthermore, the conductive material is not particularly limited as long as it prevents side reactions in the internal environment of the all-solid-state battery, does not cause chemical changes in the battery, and has excellent electrical conductivity. Typically, graphite or conductive carbon may be used, for example, graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, Denka black, thermal black, channel black, furnace black, lamp black, and summer black; carbon-based materials whose crystalline structure is graphene or graphite; conductive fibers such as carbon fibers and metal fibers; carbon fluoride; metal powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives; which may be used alone or in mixtures of two or more, but are not necessarily limited to these. Preferably, the conductive material may also contain vapor-grown carbon fiber (VGCF).

[0093] The conductive material may typically be included in an amount of 1% to 5% by weight based on the total weight of the positive electrode active material layer. Specifically, the content of the conductive material may be 1% or more by weight, 1.5% or more by weight, or 2% or more by weight, or 4% or less by weight, 4.5% or less by weight, or 5% or less by weight. If the content of the conductive material is too low (less than 1% by weight), the effect of improving electrical conductivity may not be expected, or the electrochemical properties of the battery may deteriorate. If it is too high (more than 5% by weight), the amount of negative electrode active material will be relatively small, and the capacity and energy density may decrease. The method of incorporating the conductive material into the negative electrode is not greatly limited, and conventional methods known in the art, such as mixing with the negative electrode active material or coating, may be used.

[0094] Furthermore, 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. For example, the negative electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloy. Also, similar to the positive electrode current collector, the negative electrode current collector may be made of various forms such as films, sheets, foils, nets, porous materials, foams, or nonwoven fabrics with fine irregularities formed on their surface.

[0095] The method for manufacturing the negative electrode is not particularly limited, and it can be manufactured by forming a negative electrode active material layer on a negative electrode current collector using a layer or film formation method commonly used in the industry. For example, methods such as crimping, coating, and vapor deposition may be used. Furthermore, the negative electrode of the present invention is also included in the case where a metallic lithium thin film is formed on a metal plate by initial charging after the battery has been assembled without a lithium thin film on the negative electrode current collector.

[0096] Furthermore, the term "negative electrode layer" refers to a negative electrode layer in which, during the initial assembly of the battery, lithium metal or lithium alloy, which serves as a lithium supply source among the negative electrode active materials, is not present in the negative electrode, but lithium is deposited in the negative electrode during charging. A battery containing this negative electrode layer can also be called a negative electrode-free battery.

[0097] In the aforementioned negative electrode-free battery, as the battery charges and discharges, lithium ions released from the positive electrode move to the negative electrode to form a negative electrode active material layer. For example, during charging of the battery, lithium ions are detached from the positive electrode active material and then move to the negative electrode side, becoming lithium metal composed purely of lithium. This can form a layered lithium metal layer on the negative electrode current collector, or a lithium metal structure of any shape rather than a layered one. Any shape could be, for example, a structure in which lithium metal is aggregated into particulate matter.

[0098] In one embodiment of the present invention, the sulfide-based solid electrolyte contained in the sulfide-based solid electrolyte layer can be represented by the following chemical formula 2: <Chemical formula 2> L a M b P c S d X e In the aforementioned 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 electrolytes are 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, and 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, or In), Li 10 GeP2S 12 It may include one or more species selected from the group consisting of the following:

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

[0101] [Battery Module] The present invention also relates to a battery module including the all-solid-state battery as a unit battery, a battery pack including the battery module, and a device including the battery pack as a power source.

[0102] Specific examples of the aforementioned devices include, but are not limited to, power tools powered by battery-powered motors; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters; electric golf carts; and power storage systems.

[0103] The following are preferred embodiments to aid in understanding the present invention. These embodiments are 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 present invention and the technical concept, and that such variations and modifications fall within the scope of the appended claims.

[0104] In the following examples and comparative examples, a positive electrode active material, a positive electrode containing the same, and an all-solid-state battery were manufactured as shown in Table 1 below.

[0105] [Table 1]

[0106] [Example 1] [1-1. Manufacturing of positive electrode active material with a lithium titanium oxide particle layer formed on its surface] As described in Table 1 above, a mixture was obtained by mixing 99% by weight of 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 to coat the surface of the positive electrode active material with lithium titanium oxide particles, forming a lithium titanium oxide particle layer.

[0108] [1-2. Manufacturing of the positive electrode] The positive electrode active material on which the lithium titanium oxide particle layer was formed, 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 powder mixing was performed. Specifically, the positive electrode active material and the sulfide-based solid electrolyte, Li6PS5Cl, were quantified in powder form and then mixed in a dry room environment using a blade mixer for 15 minutes to obtain a mixture. Subsequently, vapor-grown carbon fiber (VGCF) powder, which is the conductive material, was quantified and added to the mixture and mixed, and then PTFE (Polytetrafluoroethylene) powder, which is the binder, was quantified and further mixed to obtain a mixed powder.

[0109] After the mixed powder is placed in a mortar, the fibrous process is carried out in the mortar, and then calendered with a roller, resulting in a yield of 6 mAh / cm². 2 We manufactured the positive electrode for loading.

[0110] [1-3. All-solid-state battery] After sequentially stacking the positive electrode, sulfide-based solid electrolyte membrane (Li6PS5Cl), and negative electrode (lithium metal), the battery was pressurized at 100 MPa to manufacture an all-solid-state battery.

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

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

[0113] [Example 4] The procedure was carried out in the same manner as in Example 1, except that the weight of lithium titanium oxide particles was set to 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 capacity capability of the aforementioned all-solid-state battery was observed through a protocol in which it was activated at 0.05C for two cycles using a charger / discharger, and then discharged up to a maximum of 1C. Specifically, the capacity capability was observed through a protocol in which the battery was charged at 0.05C CC / CV (Constant Current / Constant Voltage), discharged at 0.05C CC (Constant Current) for two cycles using the charger / discharger, and then discharged at 0.1C / 0.2C / 0.33C / 0.5C / 1C while maintaining the 0.1C CC / CV charging process.

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

[0117] [Table 2]

[0118] Referring to Table 2 above, it can be seen that Example 1 is excellent in terms of initial coulombic efficiency, 100-cycle retention, and 1C retention.

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

[0120] Example 2 is a device that has been heat-treated at a high temperature, and the initial Coulomb efficiency and capacity retention rate have relatively decreased due to the degradation of the positive electrode active material that occurs at high temperatures.

[0121] Furthermore, in Example 3, because the particle size of the lithium titanium oxide particles is somewhat large, the coverage of the positive electrode active material surface is reduced, and side reactions occurring at the interface between the positive electrode active material and the solid electrolyte particles are not suppressed. As a result, the initial Coulomb efficiency and capacity retention rate are relatively reduced.

[0122] Furthermore, in Example 4, it was found that the relatively high content of lithium titanium oxide particles led to excessive coverage of the positive electrode surface, resulting in reduced interfacial conductivity, low initial Coulomb 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 all-solid-state batteries, comprising a lithium titanium oxide particle layer on its surface, The lithium titanium oxide particle layer has a shape in which a plurality of lithium titanium oxide particles are formed continuously or discontinuously on the surface of the positive electrode active material for the all-solid-state battery. The positive electrode active material is a positive electrode active material for all-solid-state batteries, comprising lithium nickel oxide.

2. The lithium titanium oxide is characterized by being represented by the following chemical formula 1, and is a positive electrode active material for an all-solid-state battery according to claim 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.

3. The positive electrode active material for an all-solid-state battery according to claim 1, characterized in that the shape of the lithium titanium oxide particles is one or more selected from the group consisting of spherical and polygonal shapes.

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

5. The positive electrode active material for an all-solid-state battery according to claim 1, characterized in that the lithium titanium oxide particles are included in an amount of 0.1% to 3% by weight based on the total weight of the positive electrode active material for the all-solid-state battery.

6. The BET specific surface area of ​​the positive electrode active material for the all-solid-state battery is 0.4 m². ２ / g or more 1m ２ The positive electrode active material for an all-solid-state battery according to claim 1, characterized in that it is less than or equal to / g.

7. A positive electrode for an all-solid-state battery, comprising a positive electrode active material, sulfide-based solid electrolyte particles, a conductive material, and a binder, as described in any one of claims 1 to 6.

8. The sulfide-based solid electrolyte is characterized by being represented by the following chemical formula 2, and is the positive electrode for an all-solid-state battery according to claim 7: <Chemical formula 2> L ａ M ｂ P ｃ S ｄ X ｅ In the aforementioned 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.

9. The positive electrode for an all-solid-state battery according to claim 7, characterized in that the conductive material includes one or more selected from the group consisting of vapor-grown carbon fiber (VGCF), graphite, carbon black, fluorinated carbon, metal powder, conductive whisker, conductive metal oxide, and conductive polymer.

10. The binder is 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, carboxymethylcellulose, hydroxypropylcellulose, ce A positive electrode for an all-solid-state battery according to claim 7, characterized by comprising one or more selected from the group consisting of lurose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethylsucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene.

11. An all-solid-state battery comprising a positive electrode, a negative electrode, and a sulfide-based solid electrolyte membrane interposed between them, as described in claim 7.

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