Cathode active material for all-solid-state battery, manufacturing method therefor, and cathode and all-solid-state battery comprising same

Abstract

The present invention relates to a cathode active material for an all-solid-state battery, comprising: a core part comprising lithium-metal oxide; and a coating part positioned on the surface of the core part and comprising an amorphous phase, wherein the amorphous phase comprises lithium oxide and titanium oxide.

Description

Cathode active material for all-solid-state batteries, method for producing same, all-solid-state battery cathode and all-solid-state battery comprising same

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0102368, dated August 1, 2024, and all the contents of the document in that 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 method for producing the same, a positive electrode for an all-solid-state battery including the same, and an all-solid-state battery.

[0003]

[0004] Various batteries are being studied to overcome the limitations of current lithium secondary batteries in terms of battery capacity, safety, output, large-scale development, and miniaturization.

[0005] Representative examples include metal-air batteries with much larger theoretical capacity than lithium secondary batteries, all-solid-state batteries with no risk of explosion in terms of safety, supercapacitors for output, NaS batteries or RFBs (redox flow batteries) for large-scale applications, and thin film batteries for miniaturization, all of which are being continuously researched in academia and industry.

[0006] Among the various next-generation batteries, all-solid-state batteries are batteries that replace the liquid electrolytes used in conventional lithium secondary batteries with solid electrolytes. Since they do not use flammable solvents within the battery, there is no risk of fire or explosion due to decomposition reactions of conventional electrolytes, which can significantly improve safety. Furthermore, among all-solid-state batteries, technological development is continuing for sulfide-based all-solid-state batteries, which have high ionic conductivity of solid electrolytes and can theoretically achieve high energy densities of over 900 Wh / L. Here, the term "sulfide-based all-solid-state battery" refers to an all-solid-state battery that contains a sulfide-based solid electrolyte.

[0007] In all-solid-state battery systems, lithium ion conduction does not occur through the liquid electrolyte contained 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 inside of 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, physical contact between the cathode active material, sulfide-based solid electrolyte particles, and other battery components within the cathode must be promoted, and the porosity of the cathode after rolling must be reduced, which must be maintained during charge and discharge.

[0008] However, in the case of a positive electrode for a sulfide-based all-solid-state battery, a chemical reaction can occur simply through physical contact between the positive electrode active material and the sulfide-based solid electrolyte particles due to the difference in potential between the positive electrode active material and the sulfide-based solid electrolyte particles. Furthermore, side reactions can occur at the interface between the positive electrode active material and the sulfide-based solid electrolyte particles, resulting in not only the consumption of active lithium but also increased resistance, leading to other problems.

[0009] Accordingly, the need for technological development that can prevent side reactions occurring due to physical contact between the positive electrode active material and the sulfide-based solid electrolyte particles at the positive electrode of a sulfide-based all-solid-state battery is continuously being raised.

[0010]

[0011] [Previous literature]

[0012] [Patent Document]

[0013] Republic of Korea Publication Patent No. 10-2017-0070239

[0014]

[0015] In order to solve the above problem, the inventors of the present invention conducted various studies and found that when the surface of a lithium metal oxide, which is a positive electrode active material, is coated with an amorphous phase including a mixture of lithium oxide and titanium oxide, the coating can prevent a side reaction between the positive electrode active material and the sulfide-based solid electrolyte when the positive electrode active material and the sulfide-based solid electrolyte come into physical contact within the positive electrode, thereby completing the present invention.

[0016] Accordingly, the present invention aims to provide a positive electrode active material for an all-solid-state battery capable of reducing side reactions between a positive electrode active material and a sulfide-based solid electrolyte, a method for producing the same, and a positive electrode including the same.

[0017] In addition, the present invention aims to provide an all-solid-state battery including the positive electrode, which has excellent life characteristics and discharge capacity.

[0018]

[0019] To achieve the above purpose,

[0020] The present invention comprises a core part comprising a lithium-metal oxide; and

[0021] A coating portion located on the surface of the core portion and including an amorphous phase;

[0022] The above amorphous phase provides a positive electrode active material for an all-solid-state battery, comprising lithium oxide and titanium oxide.

[0023] In addition, the present invention provides a method for producing a cathode active material for an all-solid-state battery of the present invention, comprising a step of mixing and heat-treating a lithium-metal oxide, a lithium oxide precursor, and a titanium oxide precursor.

[0024] In addition, the present invention provides a positive electrode for an all-solid-state battery comprising the positive electrode active material of the present invention, a solid electrolyte, a conductive material, and a binder.

[0025] In addition, the present invention provides an all-solid-state battery comprising the positive electrode of the present invention; a negative electrode; and a solid electrolyte layer between the positive electrode and the negative electrode.

[0026]

[0027] The positive electrode active material for an all-solid-state battery of the present invention includes an amorphous coating portion including a mixture of lithium oxide and titanium oxide on the surface of a core portion including lithium metal oxide, thereby preventing side reactions between the positive electrode active material and a sulfide-based solid electrolyte.

[0028] Accordingly, an all-solid-state battery including the positive electrode active material can have improved life characteristics and discharge capacity.

[0029]

[0030] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0031] The terminology used in the present invention is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In the present invention, it should be understood that the terms "comprise" or "have" are intended to specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0032]

[0033] Hereinafter, the present invention will be described in more detail.

[0034]

[0035] The positive electrode for an all-solid-state battery includes a positive electrode active material, a solid electrolyte, a binder, and a conductive material. When the solid electrolyte is a sulfide-based solid electrolyte, a chemical reaction may occur simply by physical contact due to the potential difference between the positive electrode active material and the sulfide-based solid electrolyte. In addition, an all-solid-state battery including the positive electrode has a problem in that an electrochemical reaction occurs at the interface between the positive electrode active material and the sulfide-based solid electrolyte during charging and discharging, resulting in the consumption of active lithium and side reactions such as increased resistance.

[0036] Therefore, the present invention sought to provide a positive electrode active material for an all-solid-state battery capable of preventing the above-mentioned side reaction.

[0037]

[0038] Cathode active material for all-solid-state batteries

[0039] The present invention comprises a core part comprising a lithium-metal oxide; and

[0040] A coating portion located on the surface of the core portion and including an amorphous phase;

[0041] The above amorphous phase relates to a positive electrode active material for an all-solid-state battery, comprising lithium oxide and titanium oxide.

[0042]

[0043] The positive electrode active material of the present invention has a core-shell structure, the core part includes lithium metal oxide, and the coating part corresponding to the shell is in an amorphous phase and includes lithium oxide (Li2O) and titanium oxide (Ti). x O y ) may be included. More specifically, the coating portion may be in an amorphous phase and may include lithium oxide and titanium oxide in a mixture form. In one embodiment, the coating portion may include a composition represented by the following chemical formula 1.

[0044] [Chemical Formula 1]

[0045] αTi x O y -βLi2O

[0046] In the above chemical formula 1,

[0047] 6≤α+β≤8, and 0.7≤Li / Ti≤0.9.

[0048] In addition, the coating portion may be an amorphous phase, include lithium oxide and titanium oxide in a mixture form, and additionally include lithium, titanium, and oxygen in a form of chemical bonding.

[0049]

[0050] The above lithium metal oxide is a material capable of inserting and extracting lithium ions, and there are no special restrictions as long as it can be used as a positive electrode active material of a lithium ion secondary battery. That is, the lithium metal oxide of the core portion can be a positive electrode active material.

[0051] For example, the lithium-metal oxide may be lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), a compound substituted with one or more transition metals; chemical formula Li x M yO2 (M = one or more selected from the group consisting of Co, Mn, Ni, Al, Fe, V, Zn, Cr, Ti, Ta, Mg, Mo, Zr, W, Sn, Hf, Nd and Gd, x is 0 <x≤1.5, y는 0<y≤1); 화학식 Li 1+x Mn 2-x Lithium manganese oxides such as O4(0≤x≤0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8; chemical formula LiNi 1-x M x Ni-site lithium nickel oxide represented by O2 (M = Co, Mn, Al, Cu, Fe, Mg, B or Ga; 0.01≤x≤0.3); chemical formula LiMn 2-x M x Lithium manganese composite oxides represented by O2 (M = Co, Ni, Fe, Cr, Zn or Ta; 0.01≤x≤0.1) or Li2Mn3MO8 (M = Fe, Co, Ni, Cu or Zn); LiCoPO4; or LiFePO4; may include, but are not limited to, these.

[0052] The above lithium-metal oxide may have a layered crystal structure and may not have a spinel structure.

[0053] Since the lithium-metal oxide has a layered crystal structure, the operating voltage of an all-solid-state battery including the positive electrode active material can be 2.5 to 4.3 V. If the lithium-metal oxide has a spinel structure, the operating voltage of an all-solid-state battery including it can be increased to 5 V. However, considering the capacity advantage of the layered structure, the spinel structure is excluded, and is not preferred because it is different from the range of operating voltage aimed at in the present invention.

[0054]

[0055] The coating portion is located on the surface of the core portion and may be an amorphous phase. In addition, the amorphous phase may include lithium oxide and titanium oxide in a mixture form.

[0056] The above coating may mean that amorphous lithium oxide and titanium oxide are physically and / or chemically bonded to the surface of the core portion. In addition, the coating portion may exist in a form that uniformly covers the entire surface of the core portion. When the coating portion exists uniformly over the entire surface of the core portion, the coating portion can prevent direct contact between the lithium-metal oxide and the sulfide-based solid electrolyte, thereby suppressing side reactions due to differences in the chemical potential of lithium ions. In addition, at the same time, the concentration of lithium increases, thereby securing a movement path for lithium ions, thereby reducing the interfacial resistance with the sulfide-based solid electrolyte. In other words, the coating portion can act as a buffer layer between the core portion and the sulfide-based solid electrolyte, thereby suppressing the side reactions and reducing the interfacial resistance.

[0057] If the amorphous phase includes lithium oxide and boron oxide in a mixture form, the effect of improving the high-rate characteristics of an all-solid-state battery including the positive electrode active material cannot be expected. The present invention can obtain the effect of improving the high-rate characteristics of an all-solid-state battery by including lithium oxide and titanium oxide in a mixture form.

[0058] The thickness of the coating portion may be 5 to 200 nm, preferably 5 to 100 nm, and most preferably 5 to 30 nm. When the thickness of the coating portion is 5 to 200 nm, the effect of suppressing side reactions between the lithium-metal oxide and the sulfide-based solid electrolyte and reducing interfacial resistance can be obtained. If the thickness of the coating portion is less than 5 nm, the effect of suppressing side reactions and reducing interfacial resistance is very minimal, and if the thickness of the coating portion exceeds 200 nm, the original electrochemical performance of the positive electrode active material may not be exhibited due to an increase in interfacial resistance, which is not preferable.

[0059] Since the above coating portion is an amorphous phase, it does not have a diffraction peak at 2θ=10 to 90° in X-ray diffraction analysis (XRD). A diffraction peak of titanium oxide may be observed at 25 to 27°, but since the diffraction peak of the titanium oxide has very low intensity, the coating portion may exist in an amorphous phase.

[0060] If the coating portion is crystalline, it may form an island type on the surface of the core portion, which is undesirable, and may cause a problem of reduced ionic conductivity. However, if the coating portion is amorphous, the problem occurring in the coating portion can be solved. Therefore, the coating portion can prevent direct contact between the lithium metal oxide and the sulfide-based solid electrolyte, thereby suppressing side reactions due to differences in the chemical potential of lithium ions, and reducing the interfacial resistance with the sulfide-based solid electrolyte.

[0061] The coating portion may be included in an amount of 0.1 to 5 parts by weight, preferably 0.1 to 1 part by weight, based on 100 parts by weight of the core portion. In addition, the molar ratio of lithium to titanium (Li / Ti) in the coating portion may be 0.7 to 0.9. The coating portion can obtain the effect of preventing the side reaction within the above range of the weight portion and molar ratio, and if it is outside the above range, the interfacial resistance increases as the side reaction occurs, which causes a problem in that the electrochemical characteristics of the all-solid-state battery including it are not improved.

[0062]

[0063] The above-mentioned positive electrode active material for an all-solid-state battery can prevent damage to the core portion, which is the positive electrode active material, by including a coating portion on the surface of the core portion.

[0064] In addition, since the bulk structure of the core portion of the positive electrode active material for the all-solid-state battery does not change even if the positive electrode active material includes a coating portion on the surface of the core portion, stable electrochemical performance can be realized. In general, if a problem occurs in the process of coating the positive electrode active material, which is the core portion, the structure of the positive electrode active material may change. For example, the bulk structure may change to a rock salt structure, and in this case, a problem of reduced lithium mobility within the positive electrode active material may occur. However, the present invention can stably maintain the bulk structure of the positive electrode active material even if the coating portion is included.

[0065]

[0066] Method for manufacturing positive electrode active material for all-solid-state batteries

[0067] The present invention relates to a method for manufacturing a positive electrode active material for an all-solid-state battery, and may include a step of mixing and heat-treating a lithium-metal oxide, a lithium oxide precursor, and a titanium oxide precursor.

[0068] The above-described positive electrode active material for an all-solid-state battery may be the positive electrode active material for an all-solid-state battery of the present invention described above. That is, the positive electrode active material for an all-solid-state battery may include a core portion comprising a lithium metal oxide; and a coating portion located on the surface of the core portion and comprising an amorphous phase, wherein the amorphous phase may include lithium oxide and titanium oxide in a mixture form.

[0069]

[0070] The above lithium-metal oxide is included in the core portion, and the lithium oxide precursor and titanium oxide precursor may be raw materials for forming the coating portion.

[0071] The above lithium metal oxide follows the above description.

[0072] The above manufacturing method may be performed by a dry process without using a solvent, or by a wet process in which a lithium metal oxide, a lithium oxide precursor, and a titanium oxide precursor are dispersed in a solvent and then mixed.

[0073] The solvent is not particularly limited as long as it is a solvent in which the lithium metal oxide, lithium oxide precursor, and titanium oxide precursor can be stably dispersed. For example, the solvent may be a solvent commonly used in the art, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methyl-2-pyrrolidone (NMP), acetone, or water, and one of these may be used alone or a mixture of two or more thereof may be used.

[0074] The lithium oxide precursor may be lithium oxide or a compound that can be converted into lithium oxide through oxidation. Examples of compounds that can be converted into lithium oxide include, but are not limited to, LiOH, Li2CO3, LiNO3, and Li2SO4.

[0075] The titanium oxide precursor may be titanium oxide or a compound that can be converted into titanium oxide through oxidation. Examples of compounds that can be converted into titanium oxide include, but are not limited to, TiO2, titanium ethoxide, and tetrabutyl titanate.

[0076] Once the formation of the coating on the surface of the lithium metal oxide core is complete, a process of obtaining a positive electrode active material for an all-solid-state battery and then drying to remove any residual solvent can be performed. The removal of the residual solvent can be accomplished using a convection oven, a thermal stirrer, or a vacuum evaporator. After the removal of the residual solvent, heat treatment can be performed.

[0077] The above heat treatment may be performed in an oxygen-containing atmosphere at a temperature of 200 to 600°C for 2 to 6 hours. Preferably, it may be performed at a temperature of 350 to 450°C for 2 to 4 hours. The heat treatment temperature may be a temperature at which the coating does not form a crystalline phase and the coating does not affect the structure of the core portion. If the heat treatment temperature is less than 200°C, the adhesion of the coating to the surface of the core portion may be reduced, and if it exceeds 600°C, the coating portion may form a crystalline phase, which is not preferable.

[0078] A cooling process may additionally be included after the above heat treatment.

[0079] In addition, since the lithium oxide may be derived from a lithium-containing component present on the surface of the lithium-metal oxide of the core portion, a cathode active material for an all-solid-state battery may be manufactured by mixing only the lithium-metal oxide and titanium oxide precursor and then heat-treating the mixture.

[0080]

[0081] Cathode for all-solid-state batteries

[0082] The present invention relates to a positive electrode for an all-solid-state battery, wherein the positive electrode may include a positive electrode active material, a sulfide-based solid electrolyte, a conductive material, and a binder, and the positive electrode active material is the positive electrode active material of the present invention described above.

[0083]

[0084] The positive electrode may include a positive electrode current collector and a positive electrode active material layer applied to one or both surfaces of the positive electrode current collector. Accordingly, the positive electrode active material, sulfide-based solid electrolyte, conductive material, and binder may be included in the positive electrode active material layer. In addition, the positive electrode may be in a current collector-free form. Accordingly, the positive electrode active material layer itself may be the positive electrode.

[0085] The above positive electrode active material may be the same as the positive electrode active material of the present invention described above.

[0086] The positive electrode active material may be included in an amount of 55 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%, 60 wt% or more, or 65 wt% or more, and may be 83 wt% or less, 85 wt% or less, or 90 wt% or less. If the content of the positive electrode active material is less than 55 wt%, battery performance may deteriorate, and if it is more than 90 wt%, mass transfer resistance may increase.

[0087] The above positive electrode current collector is intended to support the positive electrode active material layer, and is not particularly limited as long as it has excellent conductivity and is electrochemically stable in the voltage range of the lithium secondary battery. For example, the positive electrode current collector may be any one metal selected from the group consisting of copper, aluminum, stainless steel, titanium, silver, palladium, nickel, alloys thereof, and combinations thereof. The stainless steel may be surface-treated with carbon, nickel, titanium, or silver. As the alloy, an aluminum-cadmium alloy may be preferably used. In addition, calcined carbon, a non-conductive polymer surface-treated with a conductive material, or a conductive polymer may be used.

[0088] The above-mentioned positive electrode current collector can form fine irregularities on its surface to strengthen the bonding strength with the positive electrode active material, and can be used in various forms such as a film, sheet, foil, mesh, net, porous body, foam, and non-woven body.

[0089] The above sulfide-based solid electrolyte contains sulfur (S) and has the ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and may include Li-PS-based glass or Li-PS-based glass ceramic.

[0090] Specifically, the sulfide-based solid electrolyte may include at least one selected from the group consisting of Li6PS5Cl, Li6PS5Br, Li6PS5I, Li2S-P2S5, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5, Li2S-P2S5-SiS2, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2, and Li2S-GeS2-ZnS, and preferably may include at least one selected from the group consisting of Li6PS5Cl, Li6PS5Br, and Li6PS5I. The above Li6PS5Cl, Li6PS5Br, and Li6PS5I may be argyrodite type solid electrolytes. In addition, the sulfide-based solid electrolyte may be in a form doped with trace elements, for example, Li6PS5Cl may be additionally doped with bromine (Br).

[0091] In addition, the sulfide-based solid electrolyte may be included in an amount of 10 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, and may be 40 wt% or less, 45 wt% or less, or 50 wt% or less. If the content of the sulfide-based solid electrolyte is less than 10 wt%, the effect of improving ionic conductivity may be minimal, and if it exceeds 50 wt%, the content of the positive electrode active material, binder, or conductive agent may be relatively reduced, resulting in deterioration in battery performance.

[0092] The above-mentioned conductive material is not particularly limited as long as it prevents side reactions in the internal environment of the all-solid-state battery and has excellent electrical conductivity without causing chemical changes in the battery.

[0093] For example, the conductive material may include graphite or conductive carbon, and examples thereof include 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 having a crystal structure of graphene or graphite; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon; metal powders such as aluminum powder or nickel powder; conductive whiskeys such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives; which may be used alone or in combination of two or more, but are not necessarily limited thereto. Preferably, the conductive material may include vapor-grown carbon fiber (VGCF).

[0094] 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, and 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, and 4 wt% or less, 4.5 wt% or less, or 5 wt% or less. If the content of the conductive material is too small, less than 0.1 wt%, it is difficult to expect an effect of improving electrical conductivity or the electrochemical characteristics of the battery may deteriorate, and if it exceeds 5 wt%, it is too large, and the amount of the positive electrode active material is relatively small, which may result in a decrease in capacity and energy density.

[0095] In addition, the binder increases the bonding strength between the components constituting the positive electrode and between them and the current collector, and any binder known in the industry can be used.

[0096] For example, the binder may be a fluororesin binder including polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE); a rubber binder including styrene butadiene rubber (SBR), acrylonitrile-butidiene rubber, and styrene-isoprene rubber; a cellulose binder including carboxyl methyl cellulose (CMC), starch, hydroxy propyl cellulose, and regenerated cellulose; a polyalcohol binder; a polyolefin binder including polyethylene and polypropylene; a polyimide binder; a polyester binder; and a silane binder. One, two or more mixtures or copolymers selected from the group consisting of may be used.

[0097] In addition, the binder may be included in an amount of 0.1 to 3 wt% based on the total weight of the positive electrode active material layer. Specifically, the content of the binder may be 0.1 wt% or more, 0.5 wt% or more, or 0.8 wt% or more, and may be 1.5 wt% or less, 2 wt% or less, or 3 wt% or less. If the content of the binder is less than 0.1 wt%, the effect of improving the bonding strength between materials included in the positive electrode active material layer may be minimal, and thus the electrode sheet may not be properly formed. If the content of the binder is more than 3 wt%, ionic conductivity or electrical conductivity may be reduced.

[0098]

[0099] All-solid-state batteries

[0100] The present invention relates to an all-solid-state battery comprising: a positive electrode; a negative electrode; and a solid electrolyte layer between the positive electrode and the negative electrode; wherein the positive electrode is the positive electrode of the present invention described above.

[0101]

[0102] The above-mentioned negative electrode may include a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector. In addition, the negative electrode, like the positive electrode, may include a conductive material and a binder as needed. In this case, the negative electrode current collector, conductive material, and binder are as described above.

[0103] The above negative active material is lithium ion (Li + ) can be reversibly intercalated or deintercalated, or any material that can react with lithium ions to form a reversibly lithium-containing compound.

[0104] For example, the negative active material may be at least one carbon-based material selected from the group consisting of crystalline artificial graphite, crystalline natural graphite, amorphous hard carbon, low-crystalline soft carbon, carbon black, acetylene black, Ketjen black, Super-P, graphene, and fibrous carbon, Si-based material, Li x Fe2O3(0≤x≤1), Li x WO2(0≤x≤1), Sn x Me 1-x Me´ y O z (Me: Mn, Fe, Pb, Ge; Me´: Al, B, P, Si, elements of group 1, 2, and 3 of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 규소계 합금; 주석계 합금; SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료; 티타늄 산화물; 리튬 티타늄 산화물 등을 포함할 수 있지만, 이들만으로 한정되는 것은 아니다.

[0105] Additionally, the negative electrode may include a negative electrode current collector and a coating layer including metal-carbon composite particles positioned on the negative electrode current collector. This may mean an anodeless electrode that does not include a negative electrode active material.

[0106] The above negative electrode may be such that when the all-solid-state battery is charged, lithium ions pass through the coating layer to reach the surface of the negative electrode current collector, and these are deposited to form a lithium metal layer.

[0107] The above metal-carbon composite particles may have a form in which carbon particles and metal particles are attached to each other or one surface is coated with the other, and may be physically or chemically bonded.

[0108] The above carbon particles may include natural graphite, artificial graphite, hard carbon, soft carbon, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, carbon nanotubes, fullerene, carbon fiber, and fluorocarbon.

[0109] The above metal particles are lithium-philic metals, for example, Ni, Cu, Ag, Au, Pt, Al, Zn, Bi, etc., and may be one or a combination of two or more thereof. By introducing a metal having the above lithium-philic properties, it is advantageous to form a stable and uniform lithium layer on the surface of the current collector.

[0110] The above negative electrode may be manufactured by mixing a binder solution and the composite particles to prepare a slurry for forming a coating layer, and then applying and drying the slurry on a negative electrode current collector. In this case, the binder may be a conventional binder used in the art.

[0111] The above solid electrolyte layer is formed of a solid electrolyte in a layered form, and the solid electrolyte may include at least one selected from the group consisting of a sulfide-based solid electrolyte, a polymer-based solid electrolyte, and an oxide-based solid electrolyte, and preferably may include a sulfide-based solid electrolyte.

[0112] The above sulfide-based solid electrolyte follows the above-described procedure.

[0113] The above polymer-based solid electrolyte is a polymer electrolyte material formed by adding a polymer resin to a composite of a lithium salt and a polymer resin, that is, a solvated lithium salt, and is about 1x10 -7 S / cm or more, preferably about 1x10 -5 It can exhibit ionic conductivity of S / cm or more.

[0114] Non-limiting examples of the polymer resin include polyether polymers, polycarbonate polymers, acrylate polymers, polysiloxane polymers, phosphazene polymers, polyethylene derivatives, alkylene oxide derivatives such as polyethylene oxide, phosphate ester polymers, polyagitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, polymers containing ionic dissociation groups, etc., and may include one or more of these. In addition, the polymer electrolyte may include, as a polymer resin, a branched copolymer in which an amorphous polymer such as PMMA, polycarbonate, polysiloxane (PDMS) and / or phosphazene is copolymerized as a comonomer in a polyethylene oxide (PEO) main chain, a comb-like polymer, and a cross-linked polymer resin, and may include one or more of these.

[0115] In the above polymer solid electrolyte, the above-mentioned lithium salt is an ionizable lithium salt, Li + X -It can be expressed as . There is no particular limitation on the anion of these lithium salts, but F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , (CF3CF2SO2)2N - Examples include:

[0116] The above oxide-based solid electrolyte may contain oxygen (O) and have the ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table. For example, an LLTO-based compound, Li6La2CaTa2O 12 , Li6La2ANb2O 12 (A is Ca or Sr), Li2Nd3TeSbO 12 , Li3BO 2.5 N 0.5 , Li9SiAlO8, LAGP compounds, LATP compounds, Li1 +x Ti 2-x Al x Si y (PO4) 3-y(where, 0≤x≤1, 0≤y≤1), LiAl x Zr 2-x (PO4)3(where, 0≤x≤1, 0≤y≤1), LiTi x Zr 2-x (PO4)3 (wherein, 0≤x≤1, 0≤y≤1), may include at least one selected from among LISICON compounds, LIPON compounds, perovskite compounds, NASICON compounds, and LLZO compounds.

[0117]

[0118] As described above, the positive electrode active material of the present invention includes a coating portion on the surface of the core portion, and the coating portion is an amorphous phase, and the amorphous phase includes lithium oxide and titanium oxide in a mixed form, thereby preventing the lithium-metal oxide, which is the positive electrode active material, from direct contact with the sulfide-based solid electrolyte, thereby reducing side reactions occurring between the positive electrode active material and the sulfide-based solid electrolyte, and thereby reducing the interfacial resistance. In addition, an all-solid-state battery using the positive electrode active material can obtain an effect of improving the life characteristics.

[0119]

[0120] Hereinafter, the present invention will be described in more detail through examples, but the following examples are intended to illustrate the present invention, and the scope of the present invention is not limited to these examples.

[0121]

[0122] <All-solid-state battery manufacturing>

[0123] Example 1.

[0124] The core portion, a layered crystal structure positive electrode active material NCM811, and the coating portion, a lithium oxide precursor and a titanium oxide precursor, were dispersed in ethanol. The coating portion was comprised of 0.5 parts by weight based on 100 parts by weight of the core portion. The residual solvent in the dispersion was removed using a vacuum rotary evaporator. Thereafter, the dispersion from which the residual solvent had been removed was heat-treated at 400°C for 4 hours, cooled to room temperature, and then pulverized to produce a positive electrode active material for an all-solid-state battery.

[0125] The above positive electrode active material includes a core portion and a coating portion located on the surface of the core portion, the core portion is NCM811, and the coating portion includes lithium oxide and titanium oxide.

[0126] In addition, as a result of ICP analysis of the coating portion of the positive electrode active material, the molar ratio of Li and Ti in the coating portion of the positive electrode active material of Example 1 was observed to be 0.7 to 0.9.

[0127] The positive electrode active material, sulfide-based solid electrolyte particles, conductive agent, and binder were mixed in a weight ratio of 80:17:2:1 by powder mixing. Specifically, the positive electrode active material and the sulfide-based solid electrolyte Li6PS5Cl were quantified in powder form and mixed for 15 minutes using a blade mixer in a dry room environment to obtain a mixture. Thereafter, the conductive agent vapor-grown carbon fiber (VGCF) powder was quantified and added to the mixture, followed by mixing. The binder PTFE (Polytetrafluoroethylene) powder was quantified and further mixed to obtain a mixed powder.

[0128] After the above mixed powder was injected into the inducer, fiberization was performed in the inducer, and calendaring was performed on a roller to manufacture a positive electrode with a loading of 6 mAh / cm2.

[0129] The above positive electrode, sulfide-based solid electrolyte membrane (Li6PS5Cl), and negative electrode (lithium metal) were sequentially laminated, and then pressurized to 100 MPa to manufacture an all-solid-state battery.

[0130]

[0131] Example 2.

[0132] A positive electrode active material, a positive electrode, and an all-solid-state battery were manufactured in the same manner as in Example 1, except that the coating portion was included in an amount of 0.1 part by weight based on 100 parts by weight of the core portion.

[0133] As a result of ICP analysis of the coating portion of the positive electrode active material, the molar ratio of Li and Ti in the coating portion of the positive electrode active material of Example 2 was observed to be 0.7 to 0.9.

[0134]

[0135] Example 3.

[0136] A positive electrode active material, a positive electrode, and an all-solid-state battery were manufactured in the same manner as in Example 1, except that the coating portion was included in an amount of 5 parts by weight based on 100 parts by weight of the core portion.

[0137] As a result of ICP analysis of the coating portion of the positive electrode active material, the molar ratio of Li and Ti in the coating portion of the positive electrode active material of Example 3 was observed to be 0.7 to 0.9.

[0138]

[0139] Example 4.

[0140] A positive electrode active material, a positive electrode, and an all-solid-state battery were manufactured in the same manner as in Example 1, except that the coating portion was included in an amount of 10 parts by weight based on 100 parts by weight of the core portion.

[0141] As a result of ICP analysis of the coating portion of the positive electrode active material, the molar ratio of Li and Ti in the coating portion of the positive electrode active material of Example 4 was observed to be 0.7 to 0.9.

[0142]

[0143] Example 5.

[0144] A cathode active material, a cathode, and an all-solid-state battery were manufactured in the same manner as in Example 1, except that the dispersion from which the residual solvent was removed was heat-treated at a temperature of 500°C.

[0145] As a result of ICP analysis of the coating portion of the positive electrode active material, the molar ratio of Li and Ti in the coating portion of the positive electrode active material of Example 5 was observed to be 0.7 to 0.9.

[0146]

[0147] Example 6.

[0148] A cathode active material, a cathode, and an all-solid-state battery were manufactured in the same manner as in Example 1, except that the dispersion from which the residual solvent was removed was heat-treated at a temperature of 100°C.

[0149]

[0150] Comparative Example 1.

[0151] A cathode active material, a cathode, and an all-solid-state battery were manufactured in the same manner as in Example 1, except that the dispersion from which the residual solvent was removed was heat-treated at a temperature of 700°C.

[0152]

[0153] Experimental Example 1. XRD Measurement of the Coating Part of the Positive Active Material for All-Solid-State Battery

[0154] The coating portion of the positive electrode active material for an all-solid-state battery manufactured in Examples 1 to 6 and Comparative Example 1 was measured by XRD.

[0155] The above XRD was performed using Bruker's D8 ebdeavor, and the range of 10 to 90° was measured using a Cu target.

[0156] As a result of XRD measurement, the coating portion of the positive active materials of Examples 1 to 4 and 6 did not observe a peak at 2θ=10 to 90°. From this, it was found that the coating portion of the positive active materials of Examples 1 to 4 and 6 was in an amorphous phase. Since the coating portion of the positive active materials of Examples 1 to 4 and 6 is in an amorphous phase, lithium oxide and titanium oxide may be in a mixture form, and may also be in the form of lithium-titanium oxide (Li-Ti-O).

[0157] In the coating portion of the positive active material of Example 5, a titanium oxide peak with very low intensity was observed at 2θ=25 to 27°. Even though the peak was observed, the intensity was very low, indicating that the crystallinity of the coating portion was very low, and that the coating portion existed in an amorphous phase.

[0158] On the other hand, the coating portion of the positive electrode active material of Comparative Example 1 had peaks observed at 2θ=18°, 36°, 48°, 57°, 64°, 67°, and 79°. Therefore, it was found that the coating portion of the positive electrode active material of Comparative Example 1 was in a crystalline phase. Comparative Example 1 was heat-treated at a temperature of 700°C, and it was found that the coating portion had a crystalline phase due to the high heat treatment temperature.

[0159]

[0160] Experimental Example 2. Performance Evaluation of All-Solid-State Battery

[0161] The performance of the all-solid-state batteries manufactured in Examples 1 to 6 and Comparative Example 1 was evaluated.

[0162] The capacity capability of the above-mentioned all-solid-state battery was observed through a protocol of activating it in a charger / discharger at 0.05 C for 2 cycles and then discharging it up to 1 C. Specifically, the rate capability was observed through a protocol of 0.05 C CC / CV (Constant Current / Constant Voltage) charging, 2 cycles of 0.05 C CC (Constant Current) discharging, and then 0.1 C / 0.2 C / 0.33 C / 0.5 C / 1 C CC discharging while maintaining the 0.1 C CC / CV charging process. In addition, the life characteristics were observed through 0.33 C CC-CV charging and 0.33 C CC discharging, and the initial discharge capacity and Coulombic efficiency (CE) results are shown in Table 1 below.

[0163]

[0164] Discharge capacity (mAh / g) CE (%) 1.0C / 0.1C (%) Cycle capacity (@100cycle) Example 1 20794% 95% 93% Example 2 20793% 93% 91% Example 3 20493% 92% 92% Example 4 19085% 83% 88% Example 5 20193% 88% 90% Example 6 20092% 86% 85% Comparative Example 1 19985% 83% 88%

[0165]

[0166] In the results of Table 1 above, the all-solid-state batteries of Examples 1 to 3, which include a cathode active material in which the coating portion of the all-solid-state battery positive electrode active material is in an amorphous phase, the coating portion is included in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the core portion, and the molar ratio of Li / Ti in the coating portion is 0.7 to 0.9, showed excellent battery performance.

[0167] Example 4 showed that the performance of the all-solid-state battery was lower than that of Examples 1 to 3, as the coating portion of the positive electrode active material for the all-solid-state battery was in an amorphous phase and the coating portion was included at 10 parts by weight based on 100 parts by weight of the core portion.

[0168] Example 5 showed excellent results in discharge capacity, CE, and life characteristics, but the rate performance was lower than Examples 1 to 3, in that the coating portion of the positive electrode active material for an all-solid-state battery was in an amorphous phase and the heat treatment temperature during the manufacture of the positive electrode active material was 500°C.

[0169] Example 6 shows that the coating portion of the positive electrode active material for an all-solid-state battery is amorphous, and the heat treatment temperature during the production of the positive electrode active material is 100°C. This results in very weak bonding between the coating portion and the core portion, resulting in detachment of the coating portion. Consequently, the rate and life characteristics were low.

[0170] Comparative Example 1 is a case where the coating portion of the positive electrode active material for an all-solid-state battery is in a crystalline phase, and the heat treatment temperature during the manufacture of the positive electrode active material was 700°C. As the coating portion has a crystalline phase, the all-solid-state battery of Comparative Example 1 showed lower performance than Examples 1 to 3.

[0171]

[0172] From this, it can be seen that if the coating portion of the positive electrode active material for an all-solid-state battery is in an amorphous phase, the characteristics of the all-solid-state battery including it are improved. In addition, even if the coating portion is in an amorphous phase, if the bonding between the coating portion and the core portion is weak, detachment of the coating portion may occur, making it impossible to improve the characteristics of the all-solid-state battery. It can also be seen that if the coating portion is included in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the core portion, the characteristics of the all-solid-state battery can be further improved.

Claims

1. A core portion comprising a lithium metal oxide; and A coating portion located on the surface of the core portion and including an amorphous phase; The above amorphous phase is a positive electrode active material for an all-solid-state battery, comprising lithium oxide and titanium oxide.

2. In paragraph 1, A positive electrode active material for an all-solid-state battery, wherein the amorphous phase comprises lithium oxide and titanium oxide in a mixed form.

3. In paragraph 2, The above amorphous phase is a positive electrode active material for an all-solid-state battery, which comprises a composition represented by the following chemical formula 1: [Chemical Formula 1] αTi x O y -βLi2O In the above chemical formula 1, 6≤α+β≤8, and 0.7≤Li / Ti≤0.

9.

4. In paragraph 1, A cathode active material for an all-solid-state battery, wherein the molar ratio of lithium to titanium (Li / Ti) in the above-mentioned coating portion is 0.7 to 0.

9.

5. In paragraph 1, A positive electrode active material for an all-solid-state battery, wherein the amorphous phase does not have a diffraction peak at 10 to 90° in X-ray diffraction analysis.

6. In paragraph 1, The above lithium-metal oxide is a positive electrode active material for an all-solid-state battery, having a layered crystal structure.

7. In paragraph 1, A positive electrode active material for an all-solid-state battery, wherein the thickness of the coating portion is 5 to 200 nm.

8. In paragraph 1, A positive electrode active material for an all-solid-state battery, wherein the coating portion is included in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the core portion.

9. A method for producing a cathode active material for an all-solid-state battery according to claim 1, comprising a step of mixing and heat-treating a lithium metal oxide, a lithium oxide precursor, and a titanium oxide precursor.

10. In paragraph 9, A method for manufacturing a positive electrode active material for an all-solid-state battery, wherein the above heat treatment is performed at a temperature of 200 to 600°C for 2 to 4 hours.

11. A positive electrode for an all-solid-state battery comprising the positive electrode active material of paragraph 1, a sulfide-based solid electrolyte, a conductive material, and a binder.

12. An all-solid-state battery comprising the positive electrode of clause 11; a negative electrode; and a solid electrolyte layer between the positive electrode and the negative electrode.

13. In paragraph 12, An all-solid-state battery, wherein the solid electrolyte layer comprises at least one selected from the group consisting of a sulfide-based solid electrolyte, a polymer-based solid electrolyte, and an oxide-based solid electrolyte.

14. In paragraph 12, An all-solid-state battery having an operating voltage of 3 to 4.5 V.