Positive electrode active material for all-solid-state batteries, method for manufacturing the same, positive electrode for all-solid-state batteries containing the same, and all-solid-state battery

Abstract

The present invention relates to a positive electrode active material for all-solid-state batteries, a method for producing the same, a positive electrode for all-solid-state batteries containing the same, and an all-solid-state battery.

Description

[Technical Field]

[0001] This application claims priority rights under Korean Patent Application No. 10-2023-0154636 dated November 9, 2023, and Korean Patent Application No. 10-2024-0141284 dated October 16, 2024, and incorporates all the contents disclosed in the documents of said Korean Patent Applications as part of this Specification.

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

[0003] Lithium-ion batteries are widely used as power sources for portable devices, including IT mobile devices, and in recent years, the market has been growing rapidly, from small lithium-ion batteries to medium and large-sized batteries. In particular, their use as automotive batteries is on the rise. To use lithium-ion batteries as power sources for electric vehicles, high energy density and high output characteristics are required, and ensuring safety is especially important.

[0004] Conventional lithium-ion batteries use liquid, non-aqueous organic electrolytes, which pose a risk of ignition and explosion. Since explosion accidents involving products using this technology continue to occur, resolving these issues is a matter of urgency.

[0005] All-solid-state batteries replace organic electrolytes with solid electrolytes, and all battery components, such as electrodes and electrolytes, are made of solid material. Due to the high safety of the solid electrolyte itself, it is possible to fundamentally eliminate the risk of ignition and explosion.

[0006] Candidate solid electrolytes used in all-solid-state lithium-ion secondary batteries include gel-type polymer electrolytes, sulfide-based and oxide-based solid electrolytes, among which sulfide-based solid electrolytes have a capacity of 1 × 10⁻⁶. -2It exhibits high lithium-ion conductivity values ​​of S / cm or higher and has a wide potential window of 5V or more, resulting in less degradation of characteristics even in extreme environments, and offering significant advantages in the design of high-energy-density lithium-ion secondary batteries.

[0007] In all-solid-state batteries using sulfide-based solid electrolytes, there is a problem in that the capacity is not properly realized due to high interfacial resistance generated at the interface between the positive electrode active material and the sulfide-based solid electrolyte. The main causes of such interfacial resistance have been proposed to be: 1) the space charge layer phenomenon in which a lithium-deficient layer is formed at the solid electrolyte interface due to the chemical potential difference between lithium ions in the positive electrode active material and the solid electrolyte, and 2) the formation of an interfacial impurity layer due to chemical reactions at the interface between the positive electrode active material and the solid electrolyte.

[0008] To solve the aforementioned problems, a technique has been applied to introduce a coating layer on the surface of the positive electrode active material, and lithium oxide of Li-MO (where M is B, Al, Zr, P, Ti, Nb, or W) is known as the material for the coating layer. However, the materials for coating layers known to date are still insufficient to solve the aforementioned problems, and therefore, further development of materials for coating layers that can reduce the interfacial resistance generated at the interface between the positive electrode active material and the sulfide-based solid electrolyte is currently needed. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Korean Published Patent No. 2017-0070239 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] To solve the aforementioned problems, the inventors conducted multifaceted research and discovered that coating the surface of the lithium metal oxide, which is the positive electrode active material, with lithium aluminum boron oxide, a compound represented by the following chemical formula 1, can reduce the interfacial resistance between the positive electrode active material and the solid electrolyte, thus completing the present invention.

[0011] Accordingly, the present invention aims to provide a positive electrode active material for all-solid-state batteries that can reduce the interfacial resistance between the positive electrode active material and the solid electrolyte, a method for producing the same, and a positive electrode containing the same.

[0012] Furthermore, the present invention aims to provide an all-solid-state battery including the positive electrode that exhibits excellent lifespan characteristics. [Means for solving the problem]

[0013] In order to achieve the aforementioned objective, The present invention includes a core portion containing a lithium metal oxide; and The present invention provides a positive electrode active material for an all-solid-state battery, comprising a coating portion located on the surface of the core portion and containing a compound represented by the following chemical formula 1;

[0014] [Chemical formula 1] Li 1+x Al [5-(1 / 3)x-y] B y O8 The above x is 0 ≤ x ≤ 1.2, The aforementioned y is 0 <y≦0.3であり、 (1 / 3)x+y satisfies the condition 0 < (1 / 3)x+y < 5.

[0015] Furthermore, the present invention also includes the step of (1) mixing a lithium precursor, an aluminum precursor, a boron precursor, and a lithium metal oxide to produce a mixture; (2) The step of heating and drying the mixture; and (3) The present invention provides a method for producing a positive electrode active material for an all-solid-state battery, comprising the step of calcining the heated and dried mixture.

[0016] Furthermore, the present invention provides a positive electrode for an all-solid-state battery comprising the positive electrode active material, solid electrolyte, conductive material, and binder described above.

[0017] Furthermore, the present invention provides an all-solid-state battery comprising the positive electrode; negative electrode; and a solid electrolyte layer between the positive electrode and the negative electrode. [Effects of the Invention]

[0018] The positive electrode active material for all-solid-state batteries of the present invention includes a coating portion on the surface of the core portion containing lithium metal oxide, which is the positive electrode active material, containing lithium aluminum boron oxide, which is a compound represented by the following chemical formula 1. This makes it possible to suppress side reactions occurring between the positive electrode active material and the solid electrolyte and to reduce interfacial resistance.

[0019] As a result, the all-solid-state battery containing the positive electrode active material can have improved lifespan characteristics and discharge capacity. [Modes for carrying out the invention]

[0020] The terms and words used in this specification and in the claims shall not be construed to be limited to their ordinary or dictionary meanings, but rather to be construed in a sense and concept consistent with the technical idea of ​​the present invention, based on the principle that an inventor may appropriately define the concept of a term in order to best describe his invention.

[0021] The terms used in this invention are used solely to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless they are clearly different in context. In this invention, terms such as “includes” or “having” specify the presence of features, figures, stages, operations, components, parts, or combinations thereof as described in the specification, and should not be understood to preemptively exclude the presence or possibility of adding one or more other features, figures, stages, operations, components, parts, or combinations thereof.

[0022] The present invention will be described in more detail below.

[0023] Solid-state batteries use a solid electrolyte to conduct lithium ions, so the movement of lithium ions during charging and discharging occurs in a solid state. In other words, since lithium ions can only move through the actual contact area between the positive electrode and the solid electrolyte, minimizing the interfacial resistance between the positive electrode and the solid electrolyte can improve the performance of solid-state batteries.

[0024] However, side reactions occur at the actual contact site between the positive electrode and the solid electrolyte, which leads to an increase in interfacial resistance.

[0025] Therefore, the present invention aims to provide a positive electrode active material that can reduce the interfacial resistance between the positive electrode and the solid electrolyte.

[0026] Cathode active material for all-solid-state batteries The present invention includes a core portion containing a lithium metal oxide; and This invention relates to a positive electrode active material for an all-solid-state battery, comprising a coating portion located on the surface of the core portion and containing a compound represented by the following chemical formula 1;

[0027] [Chemical formula 1] Li 1+x Al [5-(1 / 3)x-y] B y O8 The above x is 0 ≤ x ≤ 1.2, The aforementioned y is 0 <y≦0.3であり、 (1 / 3)x+y satisfies the condition 0 < (1 / 3)x+y < 5.

[0028] The positive electrode active material of the present invention has a core-shell structure, wherein the core portion contains a lithium metal oxide, and the coating portion corresponding to the shell may contain the compound represented by chemical formula 1. More specifically, the positive electrode active material of the present invention may include a core portion containing a lithium metal oxide which is the positive electrode active material, and a coating portion containing the compound represented by chemical formula 1 which is a buffer layer.

[0029] The lithium metal oxide is a substance capable of inserting and desorbing lithium ions, and there is no particular limitation as long as it can be used as a positive electrode active material for a lithium ion secondary battery.

[0030] For example, the positive electrode active material includes layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), and compounds substituted with one or more transition metals; chemical formula Li x M y O2 (M is 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, y is 0 < y ≤ 1); chemical formula Li 1+x Mn 2-x O4 (0 ≤ x ≤ 0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8; chemical formula LiNi 1-x M x O2 (M = Co, Mn, Al, Cu, Fe, Mg, B or Ga; 0.01 ≤ x ≤ 0.3) nickel-site type lithium nickel oxide represented by; chemical formula LiMn 2-x M x O2 (M = Co, Ni, Fe, Cr, Zn or Ta; 0.01 ≤ x ≤ 0.1) or lithium manganese composite oxide represented by Li2Mn3MO8 (M = Fe, Co, Ni, Cu or Zn); LiNi x Mn 2-x O4 spinel-structured lithium manganese composite oxide represented by; LiCoPO4; or LiFePO4; etc. may be included, but is not limited thereto.

[0031] The coating part is located on the surface of the core part and may contain a compound represented by the following chemical formula 1.

[0032] [Chemical formula 1] Li 1+x Al [5-(1 / 3)x-y] B y O8 The above x is 0 ≤ x ≤ 1.2, The aforementioned y is 0 <y≦0.3であり、 (1 / 3)x+y satisfies the condition 0 < (1 / 3)x+y < 5.

[0033] In other words, the positive electrode active material for the all-solid-state battery of the present invention may be in a form in which a lithium metal oxide is coated with a compound represented by chemical formula 1. The coating may mean that the compound represented by chemical formula 1 is physically and / or chemically bonded to the surface of the core. The compound represented by chemical formula 1 may cover the entire surface of the core, or it may be distributed on the surface of the core in an island type or flake form, and if it is distributed in an island type or flake form, it may be separated from each other by a predetermined interval. Preferably, the compound represented by chemical formula 1 may be distributed in a form that uniformly covers the entire surface of the core. When the compound represented by chemical formula 1 is uniformly coated on the entire surface of the core, the coating layer of the compound represented by chemical formula 1 prevents direct contact between the positive electrode active material and the solid electrolyte, thereby suppressing interfacial side reactions due to the chemical potential difference of lithium ions. At the same time, the lithium concentration increases and a path for lithium ion movement is secured, so the interfacial resistance with the solid electrolyte can be reduced.

[0034] In the aforementioned chemical formula 1, if x is less than 0, the effect of reducing the interfacial resistance between the positive electrode active material and the solid electrolyte is minimal due to the presence of lithium in a low content, and the compound represented by the aforementioned chemical formula 1 may have low ionic conductivity. Furthermore, if x exceeds 0.12, the ionic conductivity begins to decrease, which is undesirable. Therefore, in the aforementioned chemical formula 1, x is 0 ≤ x ≤ 0.12, and preferably 0 ≤ x ≤ 0.09.

[0035] Also, in the chemical formula 1, when y is 0, boron (B) is not contained, so y must exceed 0. Also, when y exceeds 0.3, the formation of impurity phases and ionic conductivity decrease, which is not preferable. In the chemical formula 1, y is 0 < y ≤ 0.3, and preferably, 0.05 < y ≤ 0.2 may also be applicable.

[0036] Also, if (1 / 3)x + y is not less than 5, the chemical formula 1 cannot contain aluminum (Al), so (1 / 3)x + y must be less than 5. Also, since x is 0 ≤ x ≤ 0.12 and y is 0 < y ≤ 0.3, it is natural that (1 / 3)x + y exceeds 0.

[0037] In the chemical formula 1, x is 0 ≤ x ≤ 0.12, y is 0 < y ≤ 0.3, and (1 / 3)x + y has 0 < (1 / 3)x + y < 5, whereby the ionic conductivity of the compound represented by the chemical formula 1 may be 1 × 10 -8 S / cm or more, and preferably, 3 × 10 -6 S / cm or more may also be applicable.

[0038] Also, the thickness of the coating portion may be 10 nm to 200 nm, and preferably, 50 nm to 150 nm may also be applicable. When the thickness of the coating portion is 10 nm to 200 nm, the effect of reducing the interfacial resistance between the positive electrode active material and the solid electrolyte can be obtained. In case the thickness of the coating portion is less than 10 nm, the effect of reducing the interfacial resistance is very slight, and when the thickness of the coating portion exceeds 200 nm, there is a possibility that the original electrochemical performance of the positive electrode active material cannot be exhibited due to an increase in the interfacial resistance, which is not preferable.

[0039] The compound represented by chemical formula 1 is included in an amount of 0.1 to 5 parts by weight, preferably 1 to 3 parts by weight, based on 100 parts by weight of the core. Within the range of 0.1 to 5 parts by weight, a reduction in interfacial resistance can be obtained, but outside this range, the interfacial resistance increases, which is a problem as it prevents improvement in the electrochemical properties of the all-solid-state battery containing it.

[0040] Method for manufacturing positive electrode active material for all-solid-state batteries The present invention relates to a method for producing a positive electrode active material for an all-solid-state battery, wherein the method for producing the positive electrode active material for an all-solid-state battery is: (1) A step of mixing a lithium precursor, an aluminum precursor, a boron precursor, and a lithium metal oxide to produce a mixture; (2) The step of heating and drying the mixture; and (3) The step of calcining the heated and dried mixture;

[0041] The aforementioned step (1) is a step of mixing a lithium precursor, an aluminum precursor, a boron precursor, and a lithium metal oxide to produce a mixture.

[0042] Specifically, this may involve preparing a dispersion by dispersing a lithium precursor, an aluminum precursor, and a boron precursor in a suitable solvent, and then adding a lithium metal oxide, which is a positive electrode active material, to the dispersion to produce a mixture.

[0043] The solvent is not particularly limited as long as it can rapidly remove the lithium metal oxide without degrading its electrochemical properties, and anhydrous ethanol can be used as one specific example.

[0044] The lithium precursor may be, for example, CH3COOLi·2H2O, LiOH·H2O, LiNO3, or Li2CO3, but is not limited to these.

[0045] The aluminum precursor may be, for example, Al(NO3)3·9H2O, Al2O3,C2H4O5Al, or Al(OH)3, but is not limited to these.

[0046] The boron precursor may be, for example, H3BO3 or B2O, but is not limited to these.

[0047] Furthermore, the lithium precursor, aluminum precursor, and boron precursor may be mixed in a molar ratio of 1:4.95:0.05 to 1.09:4.7:0.3.

[0048] The (2) step is to heat and dry the mixture produced in the (1) step.

[0049] The heating may be performed simultaneously with stirring so that the mixture does not aggregate and precipitate in the solvent and has a uniformly dispersed phase. The heating temperature may be 50°C to 150°C, and is not particularly limited as long as it is a temperature at which the solvent can be evaporated. After heating and evaporating the solvent, the mixture can be dried to obtain a powder. The drying can be carried out without limitation using methods used in the industry, and in this invention, the powder mixture was dried at a temperature of 50°C to 100°C, but is not limited thereto.

[0050] The third step is to calcine the mixture that has been heated and dried in the second step.

[0051] The aforementioned firing process may involve raising the temperature to 400°C to 1000°C at a rate of 1°C / min to 10°C / min, followed by a firing period of 1 to 5 hours. Furthermore, the firing process may be carried out while injecting oxygen gas (O2).

[0052] Subsequently, the calcined mixture is cooled to room temperature to obtain the positive electrode active material for the all-solid-state battery of the present invention. That is, the positive electrode active material for the all-solid-state battery may include a core portion containing a lithium metal oxide; and a coating portion located on the surface of the core portion and containing the compound of chemical formula 1. The positive electrode active material for the all-solid-state battery is prepared as described above.

[0053] Positive electrode for all-solid-state batteries 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 solid electrolyte, a conductive material, and a binder, and the positive electrode active material is the positive electrode active material of the present invention as described above.

[0054] The positive electrode may include a positive electrode current collector and a positive electrode active material layer coated on one or both sides of the positive electrode current collector. Therefore, the positive electrode active material, solid electrolyte, conductive material, and binder may be included in the positive electrode active material layer.

[0055] The positive electrode current collector is for supporting 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. Other options include calcined carbon, a non-conductive polymer surface-treated with a conductive material, or a conductive polymer.

[0056] The positive electrode current collector can have fine irregularities formed on its surface to strengthen its bonding force with the positive electrode active material, and may be used in various forms such as film, sheet, foil, mesh, net, porous material, foam, nonwoven fabric, etc.

[0057] The solid electrolyte may include one or more selected from the group consisting of sulfide-based solid electrolytes, polymer-based solid electrolytes, and oxide-based solid electrolytes, and preferably includes a sulfide-based solid electrolyte.

[0058] The sulfide-based solid electrolyte contains sulfur (S) and has ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and may include Li-PS glass or Li-PS glass ceramic.

[0059] Specifically, the sulfide-based solid electrolyte may contain one or more 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 contains one or more selected from the group consisting of Li6PS5Cl, Li6PS5Br, and Li6PS5I. The Li6PS5Cl, Li6PS5Br, and Li6PS5I mentioned above may be argyrodite-type solid electrolytes. Furthermore, the sulfide-based solid electrolyte may be in a form doped with trace amounts of elements; for example, Li6PS5Cl may be further doped with bromine (Br).

[0060] The aforementioned polymer solid electrolyte is a composite of a lithium salt and a polymer resin, that is, a polymer electrolyte material formed by adding a polymer resin to a solvated lithium salt, and is approximately 1 × 10⁻⁶ -7 S / cm or more, preferably about 1 × 10 -5 It can exhibit ionic conductivity of S / cm or higher.

[0061] 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, and may contain one or more of these. Furthermore, as the polymer electrolyte, examples of polymer resins include branched copolymers obtained by copolymerizing a PEO (polyethylene oxide) main chain with amorphous polymers such as PMMA, polycarbonate, polysiloxane (pdms) and / or phosphazene as copolymerizers, comb-like polymers, and crosslinked polymers, and may contain one or more of these.

[0062] In the polymer solid electrolyte, the lithium salt is an ionizable lithium salt, Li + X - It can be expressed as follows. There are no particular restrictions on the anion of such lithium salt, 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 the following.

[0063] The oxide-based solid electrolyte may contain oxygen (O) and have ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table. For example, LLTO compounds, Li6La2CaTa2O 12 Li6La2ANb2O 12 (A is Ca or Sr), Li2Nd3TeSbO 12 Li3BO 2.5 N 0.5 , Li9SiAlO8, LAGP compounds, LATP compounds, Li 1+x Ti 2-x Al x Si y (PO4) 3-y (Here, 0≦x≦1, 0≦y≦1), LiAl x Zr 2-x (PO4)3 (where 0≦x≦1), LiTi x Zr 2-x (PO4)3 (where 0 ≤ x ≤ 1), may contain one or more compounds selected from LISICON compounds, LIPON compounds, perovskite compounds, NASICON compounds, and LLZO compounds.

[0064] The conductive material electrically connects the current collector and the positive electrode active material, acting as a pathway for electrons to move from the current collector to the positive electrode active material. It can be used without limitation as long as it does not undergo chemical changes in a lithium secondary battery and is porous and conductive.

[0065] For example, the conductive material can be a porous carbon-based material, such as carbon black, graphite, graphene, activated carbon, carbon fiber, metallic fibers such as metal mesh; metallic powders such as copper, silver, nickel, and aluminum; or organic conductive materials such as polyphenylene derivatives. The conductive materials can be used individually or in combination.

[0066] Currently, commercially available conductive materials include the acetylene black series (products from Chevron Chemical Company or Gulf Oil Company, etc.), the Ketjen Black EC series (products from Armak Company), Vulcan XC-72 (products from Cabot Company), and Super P (products from MMM). Examples include acetylene black, carbon black, and graphite.

[0067] Furthermore, the binder enhances the bonding force between the components constituting the positive electrode and between them and the current collector, and any binder known in the industry can be used.

[0068] For example, the binder may be one, a mixture of two or more, or a copolymer selected from the group consisting of: fluororesin binders containing polyvinylidenefluoride (PVdF) or polytetrafluoroethylene (PTFE); rubber binders containing styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, or styrene-isoprene rubber; cellulose binders containing carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, or regenerated cellulose; polyalcohol binders; polyolefin binders containing polyethylene or polypropylene; polyimide binders; polyester binders; and silane binders.

[0069] all solid state battery 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 as described above.

[0070] The negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector. Furthermore, the negative electrode, like the positive electrode, may optionally include a conductive material and a binder. In this case, the negative electrode current collector, conductive material, and binder are as described above.

[0071] The aforementioned negative electrode active material is lithium ion (Li + Any substance that can reversibly intercalate or deintercalate lithium, or react with lithium ions to reversibly form lithium-containing compounds, is acceptable.

[0072] For example, the negative electrode active material may be one or more carbon-based materials 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, fibrous carbon, Si-based materials, 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, Group 1, 2, 3 elements of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8) and other metal composite oxides; lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni-based materials; titanium oxides; lithium titanium oxides, etc., may be included, but are not limited to these only.

[0073] Further, the negative electrode may include a negative electrode current collector and a coating layer including metal-carbon composite particles located on the negative electrode current collector. This may mean an anodeless negative electrode that does not contain a negative electrode active material.

[0074] The negative electrode may be such that lithium ions pass through the coating layer and reach the surface of the negative electrode current collector during charging of the all-solid-state battery, and these are electrodeposited to form a lithium metal layer.

[0075] The metal-carbon composite particles may have a form in which carbon particles and metal particles are attached to each other or one is coated on the surface of the other, and may be physically or chemically bonded.

[0076] The aforementioned 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, fullerenes, carbon fibers, and fluorinated carbon.

[0077] The aforementioned metal particles are lithiophilic metals, such as Ni, Cu, Ag, Au, Pt, Al, Zn, and Bi, and may be one or more of these in combination. Introducing these lithium-philic metals is advantageous for forming a stable and uniform lithium layer on the surface of the current collector.

[0078] The negative electrode may be manufactured by mixing a binder solution and the composite particles to produce a slurry for forming a coating layer, and then applying and drying the slurry onto a negative electrode current collector. In this case, the binder may be a conventional binder used in the industry.

[0079] The solid electrolyte layer consists of a solid electrolyte in a layered structure, and the solid electrolyte is as described above. Therefore, the solid electrolyte may contain one or more selected from the group consisting of sulfide-based solid electrolytes, polymer-based solid electrolytes, and oxide-based solid electrolytes, and preferably contains a sulfide-based solid electrolyte.

[0080] As described above, the positive electrode active material of the present invention includes a coating portion containing chemical formula 1 on the surface of the core portion containing lithium metal oxide. This prevents the lithium metal oxide, which is the positive electrode active material, from coming into direct contact with the solid electrolyte, thereby reducing side reactions between the positive electrode active material and the solid electrolyte, and consequently reducing interfacial resistance. Therefore, an all-solid-state battery containing this can achieve improved lifespan characteristics. Thus, the all-solid-state battery of the present invention can have excellent lifespan characteristics.

[0081] The present invention will be described in more detail below with reference to examples, but these examples are for illustrative purposes only and the scope of the present invention is not limited to these.

[0082] <Manufacturing of all-solid-state batteries> Example 1-1. Production of positive electrode active material for all-solid-state batteries CH3COOLi·2H2O, Al(NO3)3·9H2O, and H3BO3 were added to anhydrous ethanol solvent in a molar ratio of 1:4.95:0.05 to disperse the precursors. 1.0 g of NCM811 was added to the dispersion, and the mixture was heated at 90°C for 2 hours while stirring at 200 rpm to evaporate the anhydrous ethanol solvent.

[0083] Subsequently, the material was dried at 80°C for 2 hours, and then heated at a rate of 5°C / minute while injecting oxygen gas, and calcined at 750°C for 2 hours. After cooling to room temperature, it was pulverized to produce the cathode active material.

[0084] The 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 is Li, which has chemical formula 1. 1+x Al [5-(1 / 3)x-y] B y It contains O8 compounds.

[0085] ICP analysis of the coating portion revealed that the coating portion of the positive electrode active material in Example 1-1 was LiAl 4.95 B 0.05 It was confirmed that it contained O8. That is, the coating portion of the positive electrode active material in Example 1-1 is Li, which has chemical formula 1. 1+x Al [5-(1 / 3)x-y] B y In O8, it was found that x is 0 and y is 0.05.

[0086] Examples 1-2. Manufacturing of all-solid-state batteries 100 mg of Li6PS5Cl was pressurized with a pressure of 2.5 tons to produce a solid electrolyte layer approximately 10 mm thick.

[0087] The positive electrode active material, conductive material (carbon fiber), and solid electrolyte (Li6PS5Cl) produced in Example 1-1 were mixed at a weight ratio of 80:19:1, and the mixture was applied to a solid electrolyte pellet together with a positive electrode current collector, and then pressed to produce a positive electrode.

[0088] Li-In alloy was used as the negative electrode.

[0089] After laminating the positive electrode, solid electrolyte layer, negative electrode, and SUS current collector in this order, it was pressed at a pressure of 3.5 tons to manufacture the all-solid-state battery of Example 1-2.

[0090] Example 2-1. Production of a positive electrode active material for an all-solid-state battery A positive electrode active material was produced in the same manner as in Example 1-1, except that the molar ratio of CH3COOLi·2H2O, Al(NO3)3·9H2O, and H3BO3 was 1.09:4.87:0.1.

[0091] The positive electrode active material includes a core part and a coating part located on the surface of the core part. The core part is NCM811, and the coating part is Li 1+x Al [5-(1 / 3)x-y] B y a compound of O8.

[0092] As a result of ICP analysis of the coating part, the coating part of the positive electrode active material of Example 2-1 was found to contain Li 1.09 Al 4.87 B 0.1 O8. That is, in Li 1+x Al [5-(1 / 3)x-y] B y O8 of the coating part of the positive electrode active material of Example 2-1, it was found that x is 0.09 and y is 0.1. [[ID=四十二]] [[ID=四十三]]

[0093] [[ID=四十四]] [[ID=四十五]]Example 2-2. Production of an all-solid-state battery [[ID=四十六]] [[ID=四十七]]An all-solid-state battery of Example 2-2 was produced in the same manner as in Example 1-2, except that the positive electrode active material of Example 2-1 was used.

[0094] Example 3-1. Production of Cathode Active Material for All-Solid-State Battery A cathode active material was produced in the same manner as in Example 1-1, except that the molar ratio of CH3COOLi·2H2O, Al(NO3)3·9H2O, and H3BO3 was 1.09:4.77:0.2.

[0095] The cathode active material includes a core part and a coating part located on the surface of the core part. The core part is NCM811, and the coating part is Li 1+x Al [5-(1 / 3)x-y] B y a compound of O8.

[0096] As a result of ICP analysis of the coating part, it was confirmed that the coating part of the cathode active material of Example 3-1 contains Li 1.09 Al 4.77 B 0.2 O8. That is, in Li 1+x Al [5-(1 / 3)x-y] B y O8 of the coating part of the cathode active material of Example 3-1, it was found that x is 0.09 and y is 0.2.

[0097] Example 3-2. Production of All-Solid-State Battery An all-solid-state battery of Example 3-2 was produced in the same manner as in Example 1-2, except that the cathode active material of Example 3-1 was used.

[0098] Example 4-1. Production of Cathode Active Material for All-Solid-State Battery A cathode active material was produced in the same manner as in Example 1-1, except that the molar ratio of CH3COOLi·2H2O, Al(NO3)3·9H2O, and H3BO3 was 1.09:4.67:0.3.

[0099] The cathode active material includes a core part and a coating part located on the surface of the core part. The core part is NCM811, and the coating part is Li 1+xAl [5-(1 / 3)x-y] B y It contains O8 compounds.

[0100] ICP analysis of the coating portion revealed that the coating portion of the positive electrode active material in Example 4-1 was Li 1.09 Al 4.67 B 0.3 It was confirmed that it contained O8. That is, the coating portion of the positive electrode active material in Example 4-1 is Li, which has chemical formula 1. 1+x Al [5-(1 / 3)x-y] B y In O8, it was found that x is 0.09 and y is 0.3.

[0101] Example 4-2. Manufacturing of an all-solid-state battery An all-solid-state battery of Example 4-2 was manufactured in the same manner as in Example 1-2, except that the positive electrode active material of Example 4-1 was used.

[0102] Comparative Example 1-1. Production of positive electrode active material for all-solid-state batteries The positive electrode active material was produced in the same manner as in Example 1-1, except that the molar ratio of CH3COOLi·2H2O and Al(NO3)3·9H2O was 1:5.

[0103] The positive electrode active material includes a core portion and a coating portion located on the surface of the core portion, the core portion being NCM811 and the coating portion being Li 1+x Al [5-(1 / 3)x-y] B y It contains O8 compounds.

[0104] ICP analysis of the coating portion confirmed that the coating portion of the positive electrode active material of Comparative Example 1-1 contained LiAl5O8. In other words, the coating portion of the positive electrode active material of Comparative Example 1-1 contained LiAl5O8, which has chemical formula 1. 1+x Al [5-(1 / 3)x-y] B y In O8, since x is 0 and y is 0, it was determined that boron is not present.

[0105] Comparative Example 1-2. Manufacturing of All-Solid-State Batteries A solid-state battery of Comparative Example 1-2 was manufactured in the same manner as in Example 1-2, except that the positive electrode active material of Comparative Example 1-1 was used.

[0106] Comparative Example 2-1. Production of positive electrode active material for all-solid-state batteries The positive electrode active material was produced in the same manner as in Example 1-1, except that the molar ratio of CH3COOLi·2H2O, Al(NO3)3·9H2O, and H3BO3 was 1:4.8:0.4.

[0107] The positive electrode active material includes a core portion and a coating portion located on the surface of the core portion, the core portion being NCM811 and the coating portion being Li 1+x Al [5-(1 / 3)x-y] B y It contains O8 compounds.

[0108] ICP analysis of the aforementioned coating portion revealed that the coating portion of the positive electrode active material in Comparative Example 2-1 was LiAl 4.6 B 0.4 It was confirmed that it contained O8. That is, the coating portion of the positive electrode active material in Comparative Example 2-1 was Li, which has chemical formula 1. 1+x Al [5-(1 / 3)x-y] B y In O8, it was found that x is 0 and y is 0.4.

[0109] Comparative Example 2-2. Manufacturing of All-Solid-State Batteries A solid-state battery of Comparative Example 2-2 was manufactured in the same manner as in Example 1-2, except that the positive electrode active material of Comparative Example 2-1 was used.

[0110] Experimental Example 1. Measurement of the ionic conductivity of the coating portion of the positive electrode active material. The ionic conductivity of the coated portion of the positive electrode active material produced in Examples 1-1 to 4-1 and Comparative Examples 1-1 to 2-1 was measured.

[0111] The ionic conductivity was measured by electrochemical impedance spectroscopy (EIS) in the frequency range of 5.0 MHz to 7.0 MHz with an alternating current (AC) voltage of 10 mV applied to a symmetric cell composed of a solid electrolyte (Li6PS5Cl) / ion conductor / solid electrolyte (Li6PS5Cl), and the results are shown in Table 1 below.

[0112]

Table 1

[0113] In Examples 1-1 to 4-1, the coating part satisfies the ranges of x, y and (1 / 3)x + y in Chemical Formula 1. On the other hand, in Comparative Examples 1-1 and 2-1, the coating parts contain LiAl5O8 and LiAl 4.6 B 0.4 O8 respectively. In Chemical Formula 1, x is 0, y is 0, x is 0, and y is 0.4 respectively, which is outside the range of y in Chemical Formula 1.

[0114] From the above results, it was found that when 0 < y ≤ 0.3 in Chemical Formula 1, the ionic conductivity of the coating part, which is a compound represented by Chemical Formula 1, is very high. On the other hand, when y is outside the above range, the ionic conductivity of the coating part shows a very low result, indicating that the effect of improving ionic conductivity cannot be obtained.

[0115] Experimental Example 2. Evaluation of charge-discharge and life characteristics of all-solid-state battery The charge-discharge and life characteristics of the all-solid-state batteries of Examples 2-2 to 3-2 and Comparative Examples 1-2 and 2-2 were measured.

[0116] The charge-discharge characteristics were measured by charging the all-solid-state battery at a temperature of 25 °C in CCCV mode at 0.1C until it reached 3.7V and then discharging it at a constant current until it reached 1.9V, and the results are shown in Table 2 below.

[0117] Lifetime characteristics were measured by charging the all-solid-state battery at 25°C in CCCV mode at 0.5C until it reached 3.7V, then discharging it to 1.9V with a constant current for 100 charge-discharge cycles. The results are shown in Table 3 below.

[0118] [Table 2]

[0119] [Table 3]

[0120] From the results in Tables 2 and 3, the positive electrode active material contained in the all-solid-state batteries of Examples 2-2 and 3-2 has superior ionic conductivity compared to the positive electrode active material contained in the all-solid-state batteries of Comparative Examples 1-2 and 2-2. As a result, the all-solid-state batteries of Examples 2-2 and 3-2 showed improved initial charge / discharge capacity and life characteristics compared to the all-solid-state batteries of Comparative Examples 1-2 and 2-2.

Claims

1. Core portion containing lithium metal oxide; and A positive electrode active material for an all-solid-state battery, comprising a coating portion located on the surface of the core portion and containing a compound represented by the following chemical formula 1: [Chemical formula 1] Li １＋ｘ Al ［５－（１／３）ｘ－ｙ］ B ｙ O ８ The above x is 0 ≤ x ≤ 1.2, The above y is 0 < y ≤ 0.3, (1 / 3)x + y satisfies the condition 0 < (1 / 3)x + y < 5.

2. The positive electrode active material for an all-solid-state battery according to claim 1, wherein y is 0.05 < y ≤ 0.

2.

3. The positive electrode active material for an all-solid-state battery according to claim 1, wherein the thickness of the coating portion is 10 nm to 200 nm.

4. The positive electrode active material for an all-solid-state battery according to claim 1, wherein the compound represented by the chemical formula 1 is included in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the core portion.

5. The ionic conductivity of the positive electrode active material is 1 × 10⁻⁶ －８ The positive electrode active material for an all-solid-state battery according to claim 1, wherein the S / cm is 1 or higher.

6. (1) A step of mixing a lithium precursor, an aluminum precursor, a boron precursor, and a lithium metal oxide to produce a mixture; (2) The step of heating and drying the mixture; and (3) A method for producing a positive electrode active material for an all-solid-state battery according to any one of claims 1 to 5, comprising the step of calcining the heated and dried mixture.

7. The method for producing a positive electrode active material for an all-solid-state battery according to claim 6, wherein the lithium precursor, aluminum precursor, and boron precursor are mixed in a molar ratio of 1:4.95:0.05 to 1.09:4.67:0.

3.

8. The method for producing a positive electrode active material for an all-solid-state battery according to claim 6, wherein the firing treatment is carried out by raising the temperature to 400°C to 1000°C at a rate of 1°C / min to 10°C / min, and then for 1 to 5 hours.

9. A positive electrode for an all-solid-state battery comprising a positive electrode active material, a solid electrolyte, a conductive material, and a binder according to any one of claims 1 to 5.

10. A solid-state battery comprising a positive electrode; a negative electrode; and a solid electrolyte layer between the positive electrode and the negative electrode, as described in claim 9.

11. The all-solid-state battery according to claim 10, wherein the solid electrolyte comprises one or more selected from the group consisting of sulfide-based solid electrolytes, polymer-based solid electrolytes, and oxide-based solid electrolytes.

12. The all-solid-state battery according to claim 11, wherein the solid electrolyte includes a sulfide-based solid electrolyte.

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