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

Abstract

The present invention relates to a positive electrode active material for an all-solid-state battery, a method for preparing the same, a positive electrode for an all-solid-state battery comprising the positive electrode active material, and an all-solid-state battery. The positive electrode active material for an all-solid-state battery includes a core portion including a lithium metal oxide, and a coating portion on a surface of the core portion and including a lithium aluminum boron oxide, the lithium aluminum boron oxide being a compound represented by Formula 1, thereby suppressing occurrence of a side reaction between the positive electrode active material and a solid electrolyte, therefore, the interface resistance is reduced, and the service life and the discharge capacity are positively influenced. [Formula 1] Li1 + xAl [5-(1 / 3) x-y] ByO8, where 0 < = x < = 1.2, 0lt; y < = 0.3, and 0 lt; (1 / 3) x + y < lt >; 5.

Description

TECHNICAL FIELD

[0001] This application claims priority to Korean Patent Application No. 10-2023-0154636, filed November 9, 2023, and Korean Patent Application No. 10-2024-0141284, filed October 16, 2024, the disclosures of which are incorporated herein in their entireties by reference.

[0002] The present application relates to a positive active material for an all-solid-state battery and a method for preparing the same, and a positive electrode for an all-solid-state battery and an all-solid-state battery comprising the same. BACKGROUND

[0003] Lithium secondary batteries are widely used as power sources for portable devices including IT mobile devices, and in recent years, the market has developed from small-sized lithium secondary batteries to medium- and large-sized secondary batteries. In particular, its use as a battery for an automobile is rapidly increasing. In order to use a lithium secondary battery as a power source for an electric vehicle, it is required to have high energy density and high power characteristics, and safety is particularly important.

[0004] Conventional lithium secondary batteries use a liquid non-aqueous organic electrolyte, which can catch fire and explode. There is an urgent need to solve these problems, as explosion accidents involving products using these batteries continue to occur.

[0005] Solid electrolytes for all-solid-state batteries replace these organic electrolytes, which indicates that all components of the battery, including the electrodes and the electrolyte, are solid, and since the solid electrolyte itself is highly safe, the risk of catching fire and explosion is eliminated.

[0006] Candidates for solid electrolytes for all-solid-state lithium ion secondary batteries include gel-type polymer electrolytes, and sulfide-based and oxide-based solid electrolytes, among which sulfide-based solid electrolytes exhibit high lithium ion conductivity of at least 1 x 10 -2 S / cm, have a wide potential window of at least 5 V, and have low performance degradation even in extreme environments, and have great advantages in the design of lithium ion secondary batteries with high energy density.

[0007] For all-solid-state batteries having such sulfide-based solid electrolytes, the interfacial resistance at the interface of the positive active material and the sulfide-based solid electrolyte is high, resulting in poor capacity utilization. It is proposed that the main cause of this interfacial resistance is 1) a space charge layer phenomenon, which is a lithium-deficient layer formed at the solid electrolyte interface due to a difference in the chemical potential of lithium ions in the positive active material and the solid electrolyte, and 2) an interfacial impurity layer formed due to a chemical reaction at the interface of the positive active material and the solid electrolyte.

[0008] To solve the above problems, a technique of introducing a coating layer on the surface of the positive electrode active material is being applied, and as a material of the coating layer, lithium oxide Li-M-O (where M is B, Al, Zr, P, Ti, Nb, or W) is known. However, the coating layer materials known so far are still insufficient to solve the above problems, and there is a need to develop a coating layer material capable of reducing the interfacial resistance at the interface between the positive electrode active material and the sulfide-based solid electrolyte. PRIOR ART

[0009] [PATENT LITERATURE]

[0010] Korean Patent Publication No. 10-2017-0070239 SUMMARY

[0011] [TECHNICAL PROBLEM]

[0012] To solve the above problems, the inventors of the present application have conducted various researches and found that coating a lithium aluminum boron oxide represented by the following Formula 1 on the surface of a lithium metal oxide positive electrode active material can reduce the interfacial resistance between the positive electrode active material and the solid electrolyte, thereby completing the present application.

[0013] Accordingly, an object of the present application is to provide a positive electrode active material for an all-solid-state battery capable of reducing the interfacial resistance between the positive electrode active material and the solid electrolyte, a method of preparing the same, and a positive electrode including the same.

[0014] Another object of the present application is to provide an all-solid-state battery including the positive electrode, which has excellent lifespan characteristics.

[0015] [TECHNICAL SOLUTION]

[0016] To achieve the above object, the present application provides a positive electrode active material for an all-solid-state battery, including: a core portion including a lithium metal oxide; and a coating portion located on the surface of the core portion and including a compound represented by Formula 1.

[0017] [Formula 1]

[0018] Li 1+x Al [5-(1 / 3)x-y] B y O8

[0019] wherein 0≤x≤1.2, 0

[0020] The present application provides a method of preparing the positive electrode active material for an all-solid-state battery of the present application, including the steps of: (1) mixing a lithium precursor, an aluminum precursor, a boron precursor, and a lithium metal oxide to prepare a mixture; (2) heating and drying the mixture; and (3) calcining the heated and dried mixture.

[0021] The present application also provides a positive electrode for a full solid battery comprising the positive electrode active material of the present application, a solid electrolyte, a conductive material, and a binder.

[0022] The present application also provides a full solid battery comprising the positive electrode of the present application; a negative electrode; and a solid electrolyte layer between the positive electrode and the negative electrode.

[0023] [Advantages]

[0024] The positive electrode active material for a full solid battery of the present application has a coating portion comprising a lithium aluminum boron oxide compound represented by Formula 1 below on the surface of a core comprising a lithium metal oxide positive electrode active material, and thus can inhibit a side reaction occurring between the positive electrode active material and the solid electrolyte, thereby reducing the interfacial resistance.

[0025] Accordingly, a full solid battery comprising the positive electrode active material can have improved lifespan characteristics and discharge capacity. DETAILED DESCRIPTION

[0026] The words and terms used in the specification and claims should not be interpreted as their ordinary or dictionary meanings, but should be interpreted based on the principle that the inventor can define the concept of the terms in order to best describe the present application in the way he or she considers most appropriate. The words or terms used in the specification and claims should be interpreted as having meanings and concepts consistent with the technical idea of the present application.

[0027] The terms used in the present application are used only to describe certain examples and are not intended to limit the present application. Unless the context clearly indicates otherwise, the singular expressions include the plural. In the present application, the term "comprising" or "having" is intended to mean the presence of the features, numbers, steps, actions, components, parts, or combinations thereof described herein, and should not be understood as excluding the possibility of the presence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0028] Hereinafter, the present application will be described in more detail.

[0029] A full solid battery uses a solid electrolyte to conduct lithium ions, and as a result, lithium ion movement due to charging and discharging occurs in a solid state. In other words, since the full solid battery allows only lithium ions to move through the actual contact site of the positive electrode and the solid electrolyte, minimizing the interfacial resistance between the positive electrode and the solid electrolyte can improve the performance of the full solid battery.

[0030] However, at the actual contact site of the positive electrode and the solid electrolyte, a side reaction can occur, thereby increasing the interfacial resistance.

[0031] Accordingly, the present application seeks to provide a positive electrode active material capable of reducing the interfacial resistance of the positive electrode and the solid electrolyte.

[0032] Positive active material for all-solid-state battery

[0033] The present application relates to a positive electrode active material for an all-solid-state battery, comprising: a core portion comprising a lithium metal oxide; and a coating portion located on a surface of the core portion and comprising a compound represented by Formula 1.

[0034] [Formula 1]

[0035] Li 1+x Al [5-(1 / 3)x-y] B y O8

[0036] wherein 0≤x≤1.2, 0<y≤0.3, and 0<(1 / 3)x+y<5.

[0037] The positive electrode active material of the present application can have a core-shell structure, in which the core portion comprises a lithium metal oxide, and the coating portion corresponding to the shell comprises a compound represented by Formula 1. More specifically, the positive electrode active material of the present application can include: a core portion comprising a lithium metal oxide as a positive electrode active material, and a coating portion comprising a buffer layer, i.e., a compound represented by Formula 1.

[0038] The lithium metal oxide is a material capable of intercalating and removing lithium ions, and is not particularly limited as long as it can be used as a positive electrode active material in a lithium ion secondary battery.

[0039] For example, the positive electrode active material can include, but is not limited to: a layered compound, such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2) or a compound substituted with one or more transition metals; a compound represented by Formula Li x M y O2(wherein M is at least one selected from Co, Mn, Ni, Al, Fe, V, Zn, Cr, Ti, Ta, Mg, Mo, Zr, W, Sn, Hf, Nd, or Gd, wherein 0<x≤1.5 and 0<y≤1); a lithium manganese oxide, such as Li 1+x Mn 2-x O4(wherein 0≤x≤0.33), LiMnO3, LiMn2O3, or LiMnO2, etc.; a lithium copper oxide (Li2CuO2); a vanadium oxide, such as LiV3O8; a Ni-site type lithium nickel compound represented by LiNi 1-x M x O2(wherein M is Co, Mn, Al, Cu, Fe, Mg, B, or Ga, 0.01≤x≤0.3); a LiMn 2-x M xLi2Mn3MO8 (wherein M is Fe, Co, Ni, Cu, or Zn) represented by Li2Mn3MO8 (wherein M is Fe, Co, Ni, Cu, or Zn); a lithium manganese composite oxide having a spinel structure, represented by LiNi x Mn 2-x O4 is represented; LiCoPO4; or LiFePO4.

[0040] The coating portion can be located on the surface of the core portion, and can include a compound represented by the following Formula 1.

[0041] [Formula 1]

[0042] Li 1+x Al [5-(1 / 3)x-y] B y O8

[0043] wherein 0≤x≤1.2, 0<y≤0.3, and 0<(1 / 3)x+y<5.

[0044] In other words, the positive active material for a full solid-state battery according to the present application can be in the form of a lithium metal oxide coated with a compound represented by Formula 1. The coating can mean that the compound represented by Formula 1 is physically and / or chemically bonded to the surface of the core portion. In addition, the compound represented by Formula 1 can cover the entire surface of the core portion, or can be distributed in island or flake shapes on the surface of the core portion, and if distributed in island or flake shapes, it can be spaced apart from each other at a predetermined interval. Preferably, the compound represented by Formula 1 can be distributed in a manner in which it uniformly covers the entire surface of the core portion. If the compound represented by Formula 1 is uniformly coated on the entire surface of the core portion, the coating of the compound represented by Formula 1 can prevent direct contact between the positive active material and the solid electrolyte, thereby suppressing an interface side reaction caused by a chemical potential difference of lithium ions. At the same time, the concentration of lithium is improved, thereby providing a migration path for lithium ions, which can reduce the interface resistance with the solid electrolyte.

[0045] In Formula 1, when x is less than 0, the effect of reducing the interface resistance between the positive active material and the solid electrolyte is not significant due to the inclusion of a low content of lithium, and the compound represented by Formula 1 can have low ionic conductivity. In addition, when x exceeds 0.12, the ionic conductivity begins to decrease, which is not desirable. Accordingly, in Formula 1, x can be 0≤x≤0.12, preferably 0≤x≤0.09.

[0046] In addition, in Formula 1, y must exceed 0 because if y is 0, it will not include boron (B). In addition, if y exceeds 0.3, it is not desirable due to the formation of an impurity phase and a decrease in ionic conductivity. In Formula 1, y can be 0<y≤0.3, preferably 0.05<y≤0.2.

[0047] Further, (1 / 3)x+y must be less than 5 because only when (1 / 3)x+y is less than 5, formula 1 can contain aluminum (Al). In addition, since x is 0≤x≤0.12 and y is 0<y≤0.3, (1 / 3)x+y is naturally greater than 0.

[0048] In formula 1, x is 0≤x≤0.12, y is 0<y≤0.3, and 0<(1 / 3)x+y<5, the ionic conductivity of the compound represented by formula 1 can be at least 1×10 -8 S / cm, preferably at least 3×10 -6 S / cm.

[0049] In addition, the thickness of the coating portion can be 10 to 200 nm, preferably 50 to 150 nm. When the thickness of the coating portion is 10 to 200 nm, the effect of reducing the interface resistance between the positive electrode active material and the solid electrolyte can be achieved. If the thickness of the coating portion is less than 10 nm, the effect of reducing the interface resistance is very insignificant, and if the thickness of the coating portion exceeds 200 nm, it can be impossible to exhibit the original electrochemical performance of the positive electrode active material due to an increase in the interface resistance, and thus is undesirable.

[0050] The content of the compound represented by formula 1 can be 0.1 parts by weight to 5 parts by weight, preferably 1 part by weight to 3 parts by weight, based on 100 parts by weight of the core portion. In the range of 0.1 to 5 parts by weight, the interface resistance reduction effect can be obtained, and outside the above range, there is a problem that the interface resistance rises and the electrochemical characteristics of the all-solid-state battery containing the same cannot be improved.

[0051] Method for producing positive active material for all-solid-state battery

[0052] The present application relates to a method for producing a positive electrode active material for an all-solid-state battery, comprising:

[0053] (1) mixing a lithium precursor, an aluminum precursor, a boron precursor, and a lithium metal oxide to prepare a mixture;

[0054] (2) heating and drying the mixture; and

[0055] (3) calcining the heated and dried mixture.

[0056] Step (1) mixes a lithium precursor, an aluminum precursor, a boron precursor, and a lithium metal oxide to prepare a mixture;

[0057] Specifically, a dispersion liquid can be prepared by dispersing a lithium precursor, an aluminum precursor, and a boron precursor in a suitable solvent, and then adding a lithium metal oxide as a positive electrode active material to the dispersion liquid to prepare a mixture.

[0058] The solvent can be, but is not limited to, any solvent capable of being quickly removed without reducing the electrochemical properties of the lithium metal oxide, and in one example, anhydrous ethanol solvent can be used.

[0059] The lithium precursor can be, for example, but not limited to, CH3COOLi·2H2O, LiOH·H2O, LiNO3, or Li2CO3.

[0060] The aluminum precursor can be, for example, but not limited to, Al(NO3)·9H2O, Al2O3, C2H4O5Al, or Al(OH)3.

[0061] The boron precursor can be, for example, but not limited to, H3BO3 or B2O.

[0062] Further, the lithium precursor, the aluminum precursor, and the boron precursor can be mixed in a molar ratio of 1:4.95:0.05 to 1.09:4.7:0.3.

[0063] Step (2) is a heating and drying step of the mixture prepared in step (1).

[0064] The heating step can be performed simultaneously with stirring, so that the mixture has uniformly dispersed phases and has no agglomeration and precipitation in the solvent. The heating temperature can be 50°C to 150°C, and the heating temperature is not particularly limited as long as it is a temperature capable of evaporating the solvent. After the solvent is evaporated by heating, the solvent can be dried to obtain a powder-like mixture, and the drying can be used without limitation using a method used in the art, and in the present application, the powder-like mixture is dried at a temperature of 50°C to 100°C, but is not limited thereto.

[0065] Step (3) is a calcination of the mixture heated and dried in step (2).

[0066] The calcination can be performed by increasing the temperature to a temperature of 400°C to 1000°C at a rate of 1 to 10°C / min and maintaining for 1 to 5 hours. Further, the calcination can also be performed while injecting oxygen (O2).

[0067] Then, the calcined mixture can be cooled to room temperature to obtain the above-described positive electrode active material for a full solid-state battery of the present application. That is, the positive electrode active material for a full solid-state battery of the present application can include: a core portion including a lithium metal oxide; and a coating portion located on a surface of the core portion and including a compound of Formula 1. The positive electrode active material for a full solid-state battery of the present application is as described above.

[0068] Positive electrode for all-solid-state battery

[0069] The present invention relates to a cathode for an all-solid-state battery, wherein the cathode can include a cathode active material, a solid electrolyte, a conductive material, and a binder, wherein the cathode active material is the cathode active material of the present invention as described above.

[0070] The cathode can include a cathode current collector and a cathode active material layer applied to one side or both sides of the cathode current collector. Accordingly, the cathode active material, the solid electrolyte, the conductive material, and the binder can be contained in the cathode active material layer.

[0071] The cathode current collector serves to support the cathode active material layer, and is not particularly limited as long as it is electrically conductive and electrochemically stable in the voltage range of the lithium secondary battery. For example, the cathode current collector can be any metal selected from copper, aluminum, stainless steel, titanium, silver, palladium, nickel, alloys thereof, and combinations thereof, wherein the stainless steel can be surface-treated with carbon, nickel, titanium, or silver, and the alloy can preferably be an aluminum-cadmium alloy, but the cathode current collector can also be a non-conductive polymer surface-treated with calcined carbon or a conductive material or a conductive polymer.

[0072] The cathode current collector can form micro concavities and convexities on its surface to strengthen the binding force with the cathode active material, and various forms such as a film, a sheet, a foil, a screen, a mesh, a porous body, a foam body, a non-woven fabric body, etc. can be used.

[0073] The solid electrolyte can 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, preferably a sulfide-based solid electrolyte.

[0074] The sulfide-based solid electrolyte contains sulfur (S), and exhibits ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and can include a Li-P-S-based glass or a Li-P-S-based glass ceramic.

[0075] Specifically, the sulfide-based solid electrolyte can 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, preferably include at least one selected from the group consisting of Li6PS5Cl, Li6PS5Br, and Li6PS5I. Li6PS5Cl, Li6PS5Br, and Li6PS5I can be argyrodite-type solid electrolytes. In addition, the sulfide-based solid electrolyte can be doped with a trace element, for example, Li6PS5Cl additionally doped with bromine (Br).

[0076] The polymer-based solid electrolyte is a complex of a lithium salt and a polymer resin, that is, a polymer electrolyte material in a form formed by adding a polymer resin to a solvated lithium salt, and can exhibit an ionic conductivity of about 1 × 10 -7 S / cm or more, preferably about 1 × 10 -5 S / cm or more.

[0077] Non-limiting examples of the polymer resin include polyether-based polymers, polycarbonate-based polymers, acrylate-based polymers, polysiloxane-based polymers, phosphazene-based polymers, polyethylene derivatives, alkylene oxide derivatives (for example, polyethylene oxide), phosphate polymers, polyblended lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, and polymers including an ionic dissociation group, and can include one or more thereof. In addition, the polymer electrolyte can be a polymer resin, for example, a branched copolymer, a comb polymer, and a cross-linked polymer resin copolymerized with an amorphous polymer such as PMMA, polycarbonate, polysiloxane (PDMS), and / or phosphazene, etc. as a comonomer in a polyethylene oxide (PEO) backbone, and can include one or more thereof.

[0078] In the polymer solid electrolyte of the present application, the lithium salt is an ionizable lithium salt, which can be represented as Li + X - . The anion of the lithium salt is not particularly limited, but can include F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 -, ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , and (CF3CF2SO2)2N - .

[0079] The oxide-based solid electrolyte can contain oxygen (O) and have ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table. For example, it can contain at least one selected from the group consisting of an LLTO-based compound, Li6La2CaTa2O 12 , Li6La2ANb2O 12 (where A is Ca or Sr), Li2Nd3TeSbO 12 , Li3BO 2.5 N 0.5 , Li9SiAlO8, a LAGP-based compound, a LATP-based compound, Li 1+x Ti 2-x Al x Si y (PO4) 3-y (where 0≤x≤1 and 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), a LISICON-based compound, a LIPON-based compound, a perovskite-based compound, a nasicon-based compound, and an LLZO-based compound.

[0080] The conductive material is a material that electrically connects the current collector and the positive active material, and functions as a path for the movement of electrons from the current collector to the positive active material, and can be used without limitation as long as it does not cause chemical changes in the lithium secondary battery and has porosity and electrical conductivity.

[0081] For example, as the conductive material, a porous carbon-based material, in which the carbon-based material includes carbon black, graphite, graphene, activated carbon, and carbon fiber; and a metal fiber such as a metal mesh; a metal powder such as copper, silver, nickel, or aluminum; or an organic conductive material such as a polyphenylene derivative can be used. The conductive material can be used alone or in combination.

[0082] Commercially available products currently used as the conductive material include acetylene black (Chevron Chemical Company or Gulf Oil Company), Ketjen black EC (Armak Company), Vulcan XC-72 (Cabot Company), and Super P (MMM). Examples can include acetylene black, carbon black, and graphite.

[0083] In addition, the binder further increases the adhesion between the components constituting the positive electrode or between the components and the current collector, and any binder known in the art can be used.

[0084] For example, the binder can be one or a mixture or copolymer of two or more selected from the group consisting of a fluoroplastic binder including polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE); a rubber-based binder including styrene butadiene rubber (SBR), acrylonitrile-butadiene rubber, or styrene-isoprene rubber; a cellulose binder including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; a polyhydric alcohol binder; a polyolefin binder including polyethylene or polypropylene; a polyimide binder; a polyester binder; and a silane binder.

[0085] All-solid-state battery

[0086] The present application relates to an all-solid-state battery including: 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 application as described above.

[0087] The negative electrode can include a negative current collector and a negative active material layer on the negative current collector. In addition, like the positive electrode, the negative electrode can include a conductive material and a binder as needed. The negative current collector, the conductive material, and the binder are as described above.

[0088] The negative active material can be a material capable of reversibly intercalating or deintercalating lithium ions (Li +) and any material that can react with lithium ions to reversibly form a lithium-containing compound.

[0089] For example, the negative active material can include, but is not limited to, one or more carbonaceous 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, and fibrous carbon; Si-based materials, Li x Fe2O3(wherein 0≤x≤1), Li x WO2(wherein 0≤x≤1), Sn x Me 1-x Me´ y O z (wherein Me is Mn, Fe, Pb, or Ge; Me' is Al, B, P, Si, an element of Group 1, 2, or 3 of the Periodic Table of Elements, a halogen; 0 < x ≤ 1; 1 ≤ y ≤ 3; and 1 ≤ z ≤ 8) and other metal complex oxides; lithium metal; lithium alloys; silicon-based alloys; tin-based alloys; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, and the like; electrically conductive polymers such as polyacetylene; Li-Co-Ni-based materials; titanium oxides; and lithium titanium oxides.

[0090] Further, the negative electrode can include a negative electrode current collector and a coating layer including metal-carbon composite particles on the negative electrode current collector. This can mean anodeless, which does not include a negative active material.

[0091] The negative electrode can be such that, when the all-solid-state battery is charged, lithium ions pass through the above-described coating layer to reach the surface of the negative electrode current collector and are electro-deposited to form a lithium metal layer.

[0092] The metal-carbon composite particles can have a structure in which carbon particles and metal particles are attached to each other, or can be a structure in which one is coated on the surface of the other, and can be physically or chemically bonded.

[0093] The carbon particles can include natural graphite, artificial graphite, hard carbon, soft carbon, carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal-cracking carbon black, carbon nanotubes, fullerenes, carbon fibers, and fluorinated carbon.

[0094] The metal particles can be lithiumophilic metals such as Ni, Cu, Ag, Au, Pt, Al, Zn, and Bi, and can be any one or a combination of two or more thereof. It is advantageous to form a stable and uniform lithium layer on the surface of the current collector by introducing a metal having lithiumophilic properties.

[0095] The negative electrode can be prepared by mixing a binder solution and composite particles to prepare a slurry for coating layer formation, then coating the slurry onto a negative electrode current collector and drying. In this case, the binder can be any conventional binder used in the art.

[0096] The solid electrolyte layer is a layer of a solid electrolyte, wherein the solid electrolyte is as described above. Thus, the solid electrolyte can comprise 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, preferably a sulfide-based solid electrolyte.

[0097] As described above, the positive electrode active material of the present application, which comprises a coating layer of Formula 1 on the surface of a core comprising a lithium metal oxide, can prevent direct contact of the lithium metal oxide as the positive electrode active material with the solid electrolyte, thereby reducing side reactions occurring between the positive electrode active material and the solid electrolyte, thereby reducing the interfacial resistance. Thus, the all-solid-state battery containing it can achieve improved life characteristics. Thereby, the all-solid-state battery of the present application can have excellent life characteristics.

[0098] Examples

[0099] The present application will now be further described with reference to the following examples, which are intended to illustrate the present application and are not intended to limit the scope of the present application.

[0100] Manufacture of an all-solid-state battery

[0101] Example 1-1. Manufacture of a positive electrode active material for an all-solid-state battery

[0102] CH3COOLi·2H2O, Al(NO3)·9H2O, and H3BO3 were added in a molar ratio of 1:4.95:0.05 in an anhydrous ethanol solvent and the above precursors were dispersed. To the above dispersion, 1.0 g of NCM811 was added, and then heated to a temperature of 90°C for 2 hours under stirring at 200 rpm, thereby evaporating the anhydrous ethanol solvent.

[0103] Then, it was dried at 80°C for 2 hours, and then fired at 750°C for 2 hours while injecting oxygen after heating at a rate of 5°C / min. Then, it was cooled to room temperature, and then ground to prepare a positive electrode active material.

[0104] The positive electrode active material comprises a core and a coating layer portion on the surface of the core, wherein the core is NCM811, and the coating layer portion comprises a compound of Formula 1 Li 1+x Al [5-(1 / 3)x-y] B y O8.

[0105] ICP analysis of the coating portion revealed that the coating portion of the positive electrode active material of Example 1-1 contained LiAl 4.95 B 0.05 O8. In other words, it was found that the coating portion of the positive electrode active material of Example 1-1 had the formula 1, Li 1+ x Al [5-(1 / 3)x-y] B y O8, where x is 0 and y is 0.05.

[0106] Example 1-2. Manufacturing of all-solid-state battery

[0107] A solid electrolyte layer of about 10 mm in thickness was prepared by pressing 100 mg of Li6PS5Cl under a pressure of 2.5 tons.

[0108] The positive electrode active material prepared in Example 1-1, the conductive material (carbon fiber), and the solid electrolyte (Li6PS5Cl) were mixed in a weight ratio of 80:19:1, and the mixture was coated together with the positive electrode current collector onto the solid electrolyte tablet prepared above and pressed to prepare a positive electrode.

[0109] Li-In alloy was used as the negative electrode.

[0110] After stacking the positive electrode, the solid electrolyte layer, the negative electrode, and the SUS current collector in the above order, an all-solid-state battery of Example 1-2 was manufactured by pressing under a pressure of 3.5 tons.

[0111] Example 2-1. Manufacturing of positive electrode active material for all-solid-state battery

[0112] The same procedure as in Example 1-1 above was performed to prepare a positive electrode active material, except that the molar ratio of CH3COOLi·2H2O, Al(NO3)·9H2O, and H3BO3 was set to 1.09:4.87:0.1.

[0113] The positive electrode active material includes a core portion and a coating portion on the surface of the core portion, wherein the core portion is NCM811, and the coating portion contains a compound of formula 1, Li 1+x Al [5-(1 / 3)x-y] B y O8.

[0114] ICP analysis of the coating portion revealed that the coating portion of the positive electrode active material of Example 2-1 contained Li 1.09 Al 4.87 B 0.1 O8. In other words, it was found that the coating portion of the positive electrode active material of Example 2-1 had the formula 1, Li 1+ x Al [5-(1 / 3)x-y] B yO8, wherein x is 0.09, and y is 0.1.

[0115] Example 2-2. Manufacturing of all-solid-state battery

[0116] The same procedure as in Example 1-2 was performed to prepare the all-solid-state battery of Example 2-2, except that the positive electrode active material of Example 2-1 was used.

[0117] Example 3-1. Manufacturing of positive electrode active material for all-solid-state battery

[0118] The same procedure as in Example 1-1 was performed to prepare the positive electrode active material, except that the molar ratio of CH3COOLi·2H2O, Al(NO3)·9H2O, and H3BO3 was set to 1.09:4.77:0.2.

[0119] The positive electrode active material includes a core part and a coating part on the surface of the core part, wherein the core part is NCM811, and the coating part contains a compound Li 1+x Al [5-(1 / 3)x-y] B y O8.

[0120] ICP analysis of the coating part revealed that the coating part of the positive electrode active material of Example 3-1 contained Li 1.09 Al 4.77 B 0.2 O8. In other words, it was found that the coating part of the positive electrode active material of Example 3-1 had the formula 1, Li 1+ x Al [5-(1 / 3)x-y] B y O8, wherein x is 0.09, and y is 0.2.

[0121] Example 3-2. Manufacturing of all-solid-state battery

[0122] The same procedure as in Example 1-2 was performed to prepare the all-solid-state battery of Example 3-2, except that the positive electrode active material of Example 3-1 was used.

[0123] Example 4-1. Manufacturing of positive electrode active material for all-solid-state battery

[0124] The same procedure as in Example 1-1 was performed to prepare the positive electrode active material, except that the molar ratio of CH3COOLi·2H2O, Al(NO3)·9H2O, and H3BO3 was set to 1.09:4.67:0.3.

[0125] The positive electrode active material includes a core part and a coating part on the surface of the core part, wherein the core part is NCM811, and the coating part contains a compound Li1+x Al [5-(1 / 3)x-y] B y O8.

[0126] ICP analysis of the coating portion revealed that the coating portion of the positive electrode active material of Example 4-1 contained Li 1.09 Al 4.67 B 0.3 O8. In other words, it was found that the coating portion of the positive electrode active material of Example 4-1 had the formula 1, Li 1+ x Al [5-(1 / 3)x-y] B y O8, where x was 0.09 and y was 0.3.

[0127] Example 4-2. Manufacturing of a full solid-state battery

[0128] The same procedure as in Example 1-2 was performed to prepare the full solid-state battery of Example 4-2, except that the positive electrode active material of Example 4-1 was used.

[0129] Comparative Example 1-1. Manufacturing of a positive electrode active material for a full solid-state battery

[0130] The same procedure as in Example 1-1 above was performed to prepare the positive electrode active material, except that the molar ratio of CH3COOLi·2H2O and Al(NO3)·9H2O was set to 1:5.

[0131] The positive electrode active material included a core portion and a coating portion on the surface of the core portion, wherein the core portion was NCM811, and the coating portion contained a compound Li 1+x Al [5-(1 / 3)x-y] B y O8.

[0132] ICP analysis of the coating portion revealed that the coating portion of the positive electrode active material of Comparative Example 1-1 contained LiAl5O8. In other words, it was found that the coating portion of the positive electrode active material of Comparative Example 1-1 had the formula 1, Li 1+x Al [5-(1 / 3)x-y] B y O8, where x was 0, y was 0, and did not contain boron.

[0133] Comparative Example 1-2. Manufacturing of a full solid-state battery

[0134] The same procedure as in Example 1-2 was performed to prepare the full solid-state battery of Comparative Example 1-2, except that the positive electrode active material of Comparative Example 1-1 was used.

[0135] Comparative Example 2-1. Manufacturing of a positive electrode active material for a full solid-state battery

[0136] The same procedure as in Example 1-1 was performed to prepare a positive electrode active material, except that the molar ratio of CH3COOLi·2H2O, Al(NO3)·9H2O, and H3BO3 was set to 1:4.8:0.4.

[0137] The positive electrode active material comprises a core and a coating portion on the surface of the core, wherein the core is NCM811, and the coating portion comprises a compound Li 1+x Al [5-(1 / 3)x-y] B y O8.

[0138] ICP analysis of the coating portion revealed that the coating portion of the positive electrode active material of Comparative Example 2-1 contained LiAl 4.6 B 0.4 O8. In other words, it was found that the coating portion of the positive electrode active material of Comparative Example 2-1 had the formula 1, Li 1+x Al [5-(1 / 3)x-y] B y O8, wherein x was 0 and y was 0.4.

[0139] Comparative Example 2-2. Manufacture of a full solid-state battery

[0140] The same procedure as in Example 1-2 was performed to manufacture the full solid-state battery of Comparative Example 2-2, except that the positive electrode active material of Comparative Example 2-1 was used.

[0141] Experimental Example 1: Measurement of the ionic conductivity of the coating portion of a positive electrode active material

[0142] The ionic conductivity of the coating portion of the positive electrode active material prepared in Examples 1-1 to 4-1 and Comparative Examples 1-1 to 2-1 was measured.

[0143] Symmetric cells of the solid electrolyte (Li6PS5Cl) / ion conductor / solid electrolyte (Li6PS5Cl) configuration were manufactured, and the ionic conductivity was measured by electrochemical impedance spectroscopy (EIS) in the frequency range of 5.0 to 7.0 MHz at an applied alternating current (AC) voltage of 10 mV, and the results are shown in Table 1 below.

[0144] [Table 1]

[0145]

[0146] In Examples 1-1 to 4-1, the coating portion satisfied the ranges of x, y, and (1 / 3)x+y of Formula 1. In contrast, in Comparative Examples 1-1 and 2-1, the coating portion contained LiAl5O8 in which x was 0 and y was 0 of Formula 1 and LiAl 4.6 B 0.4O8, where y falls outside the range of y in Formula 1.

[0147] From the above results, it can be seen that in Formula 1, if 0 < y ≤ 0.3, the ionic conductivity of the coating portion as the compound shown in Formula 1 is very high. On the other hand, if y falls outside the above range, the ionic conductivity of the coating portion is very low, and it can be seen that the effect of improving ionic conductivity cannot be obtained.

[0148] Experimental Example 2: Evaluation of charge-discharge characteristics and life characteristics of all-solid-state batteries

[0149] The charge-discharge characteristics and life characteristics of the all-solid-state batteries of Examples 2-2 to 3-2, Comparative Examples 1-2 and 2-2 were measured.

[0150] At a temperature of 25 °C, the all-solid-state battery was charged to 3.7 V at 0.1C in the CCCV mode and discharged to 1.9 V at a constant current, whereby the charge-discharge characteristics were measured. The results are shown in Table 2 below.

[0151] After measuring the charge-discharge characteristics, at a temperature of 25 °C, the all-solid-state battery was charged to 3.7 V at 0.5C in the CCCV mode and discharged to 1.9 V at a constant current, and 100 charge-discharge cycles were performed, so as to measure the life characteristics using the capacity retention rate. The results are shown in Table 3 below.

[0152] [Table 2]

[0153]

[0154] [Table 3]

[0155]

[0156] From the results of Table 2 and Table 3 above, it can be seen that the positive electrode active materials contained in the all-solid-state batteries of Examples 2-2 and 3-2 have better ionic conductivity than the positive electrode active materials contained in the all-solid-state batteries of Comparative Examples 1-2 and 2-2. Therefore, the all-solid-state batteries of Examples 2-2 and 3-2 have improved initial charge-discharge capacity and life characteristics compared with the all-solid-state batteries of Comparative Examples 1-2 and 2-2.

Claims

1. A positive electrode active material for an all-solid-state battery, comprising: A core portion containing a lithium metal oxide; And A coating portion located on the surface of the core portion and containing a compound represented by Formula 1: [Formula 1] Li 1+x Al [5-(1 / 3)x-y] B y O8 Where 0 ≤ x ≤ 1.2, 0 < y ≤ 0.3, and 0 < (1 / 3)x + y < 5.

2. The positive electrode active material for all-solid-state batteries as described in claim 1, wherein, y is 0.05 < y ≤ 0.

2.

3. The positive electrode active material for all-solid-state batteries as described in claim 1, wherein, The thickness of the coating portion is 10 nm to 200 nm.

4. The positive electrode active material for all-solid-state batteries as described in claim 1, wherein, Relative to 100 parts by weight of the core portion, the content of the compound represented by Formula 1 is 0.1 part by weight to 5 parts by weight.

5. The positive electrode active material for all-solid-state batteries as described in claim 1, wherein, The positive electrode active material has an ionic conductivity of 1×10⁻⁶. -8 S / cm or higher.

6. A method for preparing the positive electrode active material for an all-solid-state battery according to any one of claims 1 to 5, comprising the following steps: (1) Mixing a lithium precursor, an aluminum precursor, a boron precursor, and a lithium metal oxide to prepare a mixture; (2) Heating and drying the mixture; and (3) Calcining the heated and dried mixture.

7. The method for preparing the positive electrode active material for all-solid-state batteries as described in claim 6, wherein, The lithium precursor, the aluminum precursor, and the 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 preparing the positive electrode active material for all-solid-state batteries as described in claim 6, wherein, The calcining is carried out as follows: at a rate of 1 °C / minute to 10 °C / minute, the temperature is raised to a temperature of 400 °C to 1000 °C and maintained for 1 hour to 5 hours.

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

10. An all-solid-state battery, comprising the positive electrode according to claim 9; a negative electrode; and a solid electrolyte layer located between the positive electrode and the negative electrode.

11. The all-solid-state battery as claimed in claim 10, wherein, The solid electrolyte comprises at least one selected from the group consisting of sulfide solid electrolytes, polymer solid electrolytes, and oxide solid electrolytes.

12. The all-solid-state battery as claimed in claim 11, wherein, The solid electrolyte includes a sulfide solid electrolyte.

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