All-solid-state battery and method for manufacturing the same.

Abstract

The present invention relates to an all-solid-state battery and a method for manufacturing the same, wherein the average particle size of the solid electrolyte present at the interface between the negative electrode active material layer and the solid electrolyte layer is 1 to 3 μm.

Description

[Technical Field]

[0001] This application claims priority under Korean Patent Application No. 10-2024-0040201 dated March 25, 2024, and incorporates all the contents disclosed in the said Korean Patent Application as part of this Specification.

[0002] The present invention relates to an all-solid-state battery and a method for manufacturing the same. [Background technology]

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

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

[0005] All-solid-state batteries are batteries that replace the liquid electrolyte used in conventional lithium-ion secondary batteries with a solid. Because they do not use flammable solvents within the battery, and therefore do not cause ignition or explosion due to the decomposition reaction of conventional electrolytes, safety can be greatly improved.

[0006] All-solid-state batteries can be manufactured through high-pressure pressing after interposing a solid electrolyte layer between the positive electrode and the negative electrode. The solid electrolyte layer can be formed in the all-solid-state battery by methods such as using a free-standing solid electrolyte layer, transferring the solid electrolyte layer to the electrode, or applying a composition for forming a solid electrolyte layer to the electrode. Among these, the method of applying a composition for forming a solid electrolyte layer to the electrode has the advantages of high process efficiency and the ability to realize a thin-film solid electrolyte layer.

[0007] The composition for forming a solid electrolyte layer is in the form of a slurry containing a solid electrolyte, a binder, and a solvent. In case the negative electrode active material layer contains a carbon-based material as the negative electrode active material, the porosity of the negative electrode active material layer is high, and a phenomenon occurs where the solvent of the composition for forming a solid electrolyte layer penetrates into the pores of the negative electrode active material layer. At this time, fine particles of the solid electrolyte and the binder, etc. penetrate into the pores together with the solvent and come to be located at the interface between the negative electrode active material layer and the solid electrolyte layer, which may cause problems such as an increase in the irreversible capacity of the all-solid-state battery and a decrease in the life characteristics.

[0008] Therefore, in the process of applying a composition for forming a solid electrolyte layer to the negative electrode active material layer, research is needed to prevent the solid electrolyte from penetrating into the coating layer.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] In order to solve the above problems, as a result of extensive research by the inventors, We confirmed that if the average particle size of the solid electrolyte present at the interface between the negative electrode active material layer and the solid electrolyte layer is 1 to 3 μm, the amount of solid electrolyte penetrating into the pores of the negative electrode active material layer can be reduced, thus completing the present invention.

[0011] Therefore, the present invention aims to provide an all-solid-state battery with improved lifespan characteristics by preventing the solid electrolyte from penetrating the negative electrode active material layer.

[0012] Another object of the present invention is to provide a method for manufacturing the all-solid-state battery. [Means for solving the problem]

[0013] In order to achieve the aforementioned objective, The present invention includes a positive electrode comprising a positive electrode active material layer; a negative electrode comprising a negative electrode active material layer; and a solid electrolyte layer comprising a solid electrolyte interposed between the positive electrode active material layer and the negative electrode active material layer; The aforementioned negative electrode active material layer contains a carbon-based material as the negative electrode active material. The present invention provides an all-solid-state battery in which the average particle size of the solid electrolyte present at the interface between the negative electrode active material layer and the solid electrolyte layer is 1 to 3 μm.

[0014] Furthermore, the present invention also includes the step of (1) mixing a negative electrode active material, a binder, and a solvent to produce a composition for forming a negative electrode active material layer; (2) A step of applying and drying the negative electrode active material layer forming composition onto the negative electrode current collector to form the negative electrode active material layer; (3) A step of pressurizing the negative electrode active material layer to manufacture the negative electrode; (4) A step of mixing a solid electrolyte, a binder, and a solvent to produce a composition for forming a solid electrolyte layer; (5) The step of applying the solid electrolyte layer forming composition onto the negative electrode active material layer and drying it to produce a solid electrolyte layer; and (6) A method for manufacturing an all-solid-state battery according to the present invention, comprising the step of stacking a positive electrode on the solid electrolyte layer. [Effects of the Invention]

[0015] The all-solid-state battery of the present invention has an average particle size of 1 to 3 μm for the solid electrolyte present at the interface between the negative electrode active material layer and the solid electrolyte layer. This reduces the amount of solid electrolyte that penetrates into the pores of the negative electrode active material layer, thereby reducing side reactions and irreversible capacity between the negative electrode active material and the solid electrolyte during operation of the all-solid-state battery and improving its lifespan characteristics. [Brief explanation of the drawing]

[0016] [Figure 1] This is a photograph of the interface of the all-solid-state battery in Example 1. [Figure 2] This is a photograph of the interface of the all-solid-state battery in Comparative Example 1. [Figure 3] This is a graph showing the measured life characteristics of the all-solid-state battery in Experimental Example 1. [Modes for carrying out the invention]

[0017] The present invention will be described in more detail below.

[0018] The terms and words used in this specification and in the claims should not be interpreted in their ordinary or dictionary sense, but rather in a sense and concept consistent with the technical idea of ​​the present invention, based on the principle that inventors may appropriately define the concepts of terms in order to best describe their invention.

[0019] The terms used in this invention are used solely to describe specific embodiments and are not intended to limit the invention. A singular expression includes plural expressions unless the context clearly indicates otherwise. In this invention, terms such as “includes” or “having” are intended to specify the existence of features, figures, stages, operations, components, parts, or combinations thereof described in the specification, and should not be understood to preemptively exclude the existence or possibility of adding one or more other features, figures, stages, operations, components, parts, or combinations thereof.

[0020] all solid state battery The present invention includes a positive electrode comprising a positive electrode active material layer; a negative electrode comprising a negative electrode active material layer; and a solid electrolyte layer comprising a solid electrolyte interposed between the positive electrode active material layer and the negative electrode active material layer; The aforementioned negative electrode active material layer contains a carbon-based material as the negative electrode active material. This invention relates to an all-solid-state battery in which the average particle size of the solid electrolyte present at the interface between the negative electrode active material layer and the solid electrolyte layer is 1 to 3 μm.

[0021] The negative electrode including the negative electrode active material layer may also include a negative electrode current collector and the negative electrode active material layer on the negative electrode current collector.

[0022] The negative electrode current collector is for supporting the negative 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 all-solid-state battery. For example, the negative 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 or conductive polymer surface-treated with a conductive material.

[0023] The negative electrode current collector can have fine irregularities formed on its surface to strengthen the bonding force with the negative electrode active material, and can be used in various forms such as film, sheet, foil, mesh, net, porous material, foam, nonwoven fabric, etc.

[0024] The anode active material layer may include a carbon-based material as the anode active material. An anode containing a carbon-based material as the anode active material may be anodeless.

[0025] If the negative electrode of the all-solid-state battery is a non-negative electrode, during charging of the all-solid-state battery, lithium ions that have moved from the positive electrode can be deposited and stored in the form of lithium metal (Li) between the negative electrode active material layer and the negative electrode current collector, thereby forming a lithium metal layer.

[0026] The carbon-based material may include one or more selected from the group consisting of natural graphite, artificial graphite, hard carbon, soft carbon, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon nanotubes, fullerenes, carbon fibers, and fluorinated carbon, and preferably includes carbon black.

[0027] Furthermore, the negative electrode active material layer may also contain a metal, and if a metal is included, lithium metal (Li) can be formed more smoothly and flatly between the negative electrode active material layer and the negative electrode current collector.

[0028] The aforementioned metal is a lithiophilic metal and may include one or more selected from the group consisting of nickel, copper, silver, gold, platinum, aluminum, zinc, palladium, and bismuth.

[0029] The negative electrode active material layer may further contain a binder. The binder enhances the bonding force between the negative electrode active material and the negative electrode current collector, and its type is not particularly limited as long as it is used in the industry.

[0030] 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.

[0031] The porosity of the negative electrode active material layer may be 15 to 40%, preferably 15 to 30%. Furthermore, the average diameter of the pores in the negative electrode active material layer may be less than 0.5 to 0.7 μm.

[0032] A solid electrolyte layer can be formed by applying a solid electrolyte layer-forming composition onto a negative electrode active material layer. The solid electrolyte layer-forming composition is in slurry form, and the solvent in the slurry penetrates into the pores of the negative electrode active material layer. Generally, if the negative electrode active material is a carbon-based material, the porosity of the negative electrode active material layer is high, and as the solvent in the slurry penetrates into the pores of the negative electrode active material layer, the solid electrolyte particles contained in the solid electrolyte layer-forming composition also penetrate, causing the solid electrolyte particles to be located at the interface between the negative electrode active material layer and the solid electrolyte layer. When solid electrolyte particles are located at this interface, the irreversible capacity of the all-solid-state battery increases, which can lead to problems such as poor lifespan characteristics. In this specification, if the average particle size of the solid electrolyte is less than 1 μm, it means that the solid electrolyte is made up of fine particles.

[0033] However, even if the negative electrode active material layer of the all-solid-state battery of the present invention contains a carbon-based material as the negative electrode active material, the aforementioned problems can be solved because the negative electrode active material layer has the aforementioned porosity and average pore diameter.

[0034] The average particle size (D50) of the solid electrolyte may be 2 to 4 μm, and D10 may be fine particles less than 1 μm. Also, D90 may be 5 to 8 μm. Although the average particle size (D50) of the solid electrolyte is 2 to 4 μm, the average particle size (D50) of the solid electrolyte present at the interface between the negative electrode active material layer and the solid electrolyte layer may be 1 to 3 μm, preferably 1 to 2 μm. This means that the negative electrode active material layer having the aforementioned porosity and average pore diameter reduces the penetration of fine particle solid electrolyte into the pores of the negative electrode active material layer. Therefore, the all-solid-state battery of the present invention can have the effect of low irreversible capacity and excellent life characteristics. If the porosity of the negative electrode active material layer exceeds 40% or the average pore diameter is 0.7 μm or more, the penetration of fine particle solid electrolyte into the pores of the negative electrode active material layer increases, and the average particle size of the solid electrolyte present at the interface between the negative electrode active material layer and the solid electrolyte layer may be less than 1 μm. This could increase the irreversible capacity of the all-solid-state battery and potentially degrade its lifespan. The average particle size D50 refers to the particle size where the cumulative volume accounts for 50% of the particle size distribution curve.

[0035] The positive electrode including the positive electrode active material layer may also include a positive electrode current collector and the positive electrode active material layer on the positive electrode current collector.

[0036] The positive electrode current collector is the same as the negative electrode current collector described above.

[0037] The positive electrode active material layer may selectively contain a conductive material or a binder, the binder being as described above.

[0038] The cathode active material may vary depending on the type of all-solid-state battery. For example, the cathode active material may be a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; 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, V2O5, Cu2V2O7; 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 oxides 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 oxides represented by Li2Mn3MO8 (M = Fe, Co, Ni, Cu or Zn); LiNi x Mn 2-x O4 spinel-structured lithium manganese composite oxides represented by; LiCoPO4; LiFePO4; sulfur element (Elemental sulfur, S8); Li2S n (n = 1), organic sulfur compounds or carbon-sulfur polymers ((C2S x ) n : x = 2.5 to 50, n = 2) and the like sulfur series compounds may be included, but are not limited thereto.

[0039] The conductive material electrically connects the electrolyte and the cathode active material and serves as a path for electrons to move from the current collector to the cathode active material. As long as it does not cause a chemical change in the lithium secondary battery and has porosity and conductivity, it can be used without limitation. [[ID=...]] [[ID=...]]

[0040] [[ID=...]] 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.

[0041] 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.

[0042] The solid electrolyte layer contains a solid electrolyte, which 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.

[0043] 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.

[0044] 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-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).

[0045] 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 x 10⁻⁶ -7 S / cm or more, preferably about 1 x 10 -5 It can exhibit ionic conductivity of S / cm or higher.

[0046] 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, agitation 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.

[0047] In the polymer solid electrolyte, the lithium salt is an ionizable lithium salt, Li + X - This can be shown as follows. There are no particular limitations on the anion of such a 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.

[0048] 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, Li1 +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, 0≦y≦1), LiTi x Zr 2-x (PO4)3 (where 0≦x≦1, 0≦y≦1), may contain one or more compounds selected from LISICON compounds, LIPON compounds, perovskite compounds, NASICON compounds, and LLZO compounds.

[0049] Furthermore, the solid electrolyte layer may further contain a binder, and the type of binder is not particularly limited as long as it is used in the industry.

[0050] For example, acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), butadiene rubber (BR), styrene-butadiene-styrene copolymer (SBS), polybutadiene (PAN), styrene-ethylene / butylene-styrene block copolymer (SEBS), silicone rubber (SR), hydrogenated nitrile butadiene rubber (HNBR), poly(ethylene vinyl acetate) (PEVA), poly(methyl methacrylate) (PMMA), polyisobutene (PIB), polyacrylate, etc. may be used, but are not limited to these.

[0051] Manufacturing method for all-solid-state batteries This invention relates to a method for manufacturing an all-solid-state battery. (1) A step of mixing carbon-based material, binder and solvent to produce a composition for forming a negative electrode active material layer; (2) A step of applying and drying the negative electrode active material layer forming composition onto the negative electrode current collector to form the negative electrode active material layer; (3) A step of pressurizing the negative electrode active material layer to manufacture the negative electrode; (4) A step of mixing a solid electrolyte, a binder, and a solvent to produce a composition for forming a solid electrolyte layer; (5) The step of applying the solid electrolyte layer forming composition onto the negative electrode active material layer and drying it to produce a solid electrolyte layer; and (6) The step of stacking a positive electrode on the solid electrolyte layer may be included, and the all-solid-state battery manufactured through the above step may be the all-solid-state battery of the present invention as described above.

[0052] Step (1) above is a step of manufacturing a composition for forming a negative electrode active material layer, the composition for forming a negative electrode active material layer being in slurry form and may contain a carbon-based material, a binder and a solvent, and may further contain a metal. The carbon-based material, binder and metal are as described above. The type of solvent is not particularly limited as long as it can disperse the carbon-based material, binder and metal.

[0053] The carbon-based material and the binder may be mixed in a weight ratio of 95:5 to 90:10.

[0054] The (2) step is to apply the slurry-like negative electrode active material layer forming composition manufactured in the (1) step onto the negative electrode current collector and dry it to form the negative electrode active material layer, and the negative electrode current collector is as described above.

[0055] The aforementioned coating method involves applying the negative electrode active material layer forming composition onto the negative electrode current collector. This can be done by distributing the negative electrode active material layer forming composition onto the negative electrode current collector and then uniformly dispersing it using a doctor blade or the like, or by die casting, comma coating, screen printing, or the like. At this time, the final thickness of the coating can be adjusted by adjusting the concentration of the negative electrode active material layer forming composition or the number of coatings.

[0056] The aforementioned drying process involves removing solvents and moisture from the composition in order to dry the negative electrode active material layer-forming composition applied to the negative electrode current collector, and may vary depending on the solvent used. For example, it can be carried out in a vacuum oven at 50 to 200°C. Examples of drying methods include drying with hot air, hot air, low-humidity air, vacuum drying, and drying by irradiation with (far) infrared rays or electron beams. The drying time is not particularly limited, but is usually carried out in the range of 30 seconds to 24 hours.

[0057] Step (3) above is a step of pressurizing the negative electrode active material layer formed in step (2), and the pressurization may be 30 to 500 MPa. By pressurizing the negative electrode active material layer, the porosity and average diameter of the pores in the negative electrode active material layer can be reduced. By pressurizing within the above range, the negative electrode active material layer of the present invention may have a porosity of 15 to 40%, and the average diameter of the pores may be less than 0.5 to 0.7 μm. As a result, as described above, the penetration of fine particle solid electrolyte into the pores of the negative electrode active material layer can be reduced, thereby reducing the irreversible capacity of the all-solid-state battery and improving its lifespan characteristics. If the negative electrode active material layer is not pressurized or is pressurized at less than 30 MPa, the porosity of the negative electrode active material layer will not be reduced, and the average particle size of the solid electrolyte present at the interface between the negative electrode active material layer and the solid electrolyte layer will be less than 1 μm, and as a result, the effect of improving the lifespan characteristics of the all-solid-state battery cannot be obtained. Furthermore, if the pressurization exceeds 500 MPa, there is a possibility that the negative electrode will be damaged by the strong pressure.

[0058] Step (4) above is a step of producing a composition for forming a solid electrolyte layer, the composition for forming a solid electrolyte layer comprising a solid electrolyte, a binder, and a solvent, and may be in slurry form. The solid electrolyte and binder are as described above. The solvent may be one that can disperse the solid electrolyte and binder and has a dielectric constant of 0.5 to 10. Examples of solvents that may be used include xylene, hexane, benzene, anisole, isobutyl isobutyrate, toluene, and butyl butyrate.

[0059] The solid electrolyte and binder may be mixed in a weight ratio of 98:2 to 90:10.

[0060] Step (5) is a step in which the solid electrolyte layer forming composition manufactured in step (4) is applied to the negative electrode active material layer and dried to form a solid electrolyte layer, and the application and drying may be the same as the application and drying in step (2) described above.

[0061] The aforementioned step (6) is the step of stacking positive electrodes on a solid electrolyte layer.

[0062] The positive electrode is manufactured by coating a positive electrode active material layer-forming composition onto a positive electrode current collector and drying it. The positive electrode active material layer-forming composition may contain a binder or a conductive material in addition to the positive electrode active material, and the positive electrode current collector, positive electrode active material, binder, and conductive material are as described above. Furthermore, the solvent type of the positive electrode active material layer-forming composition is not particularly limited, as long as it is in slurry form and can disperse the positive electrode active material, binder, and conductive material.

[0063] The positive electrode can be manufactured by applying and drying the positive electrode active material layer formation composition onto a positive electrode current collector, and the application and drying may be the same as the application and drying in step (2) described above.

[0064] The shape of the all-solid-state battery is not particularly limited and can be in various shapes such as cylindrical, stacked, or coin-shaped.

[0065] The following are preferred embodiments to aid in understanding the present invention. However, these embodiments are merely illustrative of the present invention, and it will be obvious to those skilled in the art that various changes and modifications are possible within the scope of the present invention and the technical concept, and such changes and modifications will naturally fall within the scope of the attached claims.

[0066] <Manufacturing of all-solid-state batteries> Example 1. A slurry-like composition for forming a negative electrode active material layer was prepared by dispersing a negative electrode active material (carbon black), a binder (polyvinylidene fluoride), and silver (Ag) in methylpyrrolidone. After applying the composition for forming a negative electrode active material layer onto a SUS negative electrode current collector, vacuum drying was performed at 100°C for 10 hours to form a negative electrode active material layer.

[0067] The negative electrode active material layer was pressurized to 300 MPa using CIP. The porosity of the negative electrode active material layer was 25%, and the average diameter of the pores was 0.5 μm.

[0068] A slurry-like composition for forming a solid electrolyte layer was prepared by dispersing a solid electrolyte (argyrodite, Li6PS5Cl) and a binder (nitrile butadiene rubber) in butyrate. At this time, the average particle size of the solid electrolyte was 2.66 μm for D50, 0.79 μm for D10, 6.42 μm for D90, and 10.9 μm for D99.

[0069] The solid electrolyte layer-forming composition was applied onto the negative electrode active material layer using a bar coater, and then vacuum-dried at 70°C for 5 hours to form a solid electrolyte layer.

[0070] A slurry-like composition for forming a positive electrode active material layer was prepared by dispersing a positive electrode active material (NCM 811), a conductive material (carbon fiber), a solid electrolyte (Li6PS5Cl), and a binder (polytetrafluoroethylene) in a solvent (butyrate). After applying the composition for forming a positive electrode active material layer to a positive electrode current collector, it was dried to produce a positive electrode containing the positive electrode active material layer.

[0071] The positive electrode was stacked on a solid electrolyte layer to manufacture an all-solid-state battery.

[0072] Comparative Example 1. A solid-state battery was manufactured in the same manner as in Example 1, except that the process of pressurizing the negative electrode active material layer was not performed.

[0073] The porosity of the negative electrode active material layer of the aforementioned all-solid-state battery was 45%, and the average diameter of the pores was 0.7 μm.

[0074] Experimental Example 1. Measurement of the average particle size (D50) of the solid electrolyte present at the interface between the negative electrode active material layer and the solid electrolyte layer. In the all-solid-state batteries of Example 1 and Comparative Example 1, the average particle size (D50) of the solid electrolyte present at the interface between the negative electrode active material layer and the solid electrolyte layer was measured.

[0075] Figure 1 shows a cross-section of the all-solid-state battery of Example 1, and Figure 2 shows a cross-sectional photograph of the all-solid-state battery of Comparative Example 1. Particle size measurement was performed using the imageJ program.

[0076] The average particle size of the solid electrolyte contained in the solid electrolyte layer forming composition was 2.66 μm, and D10 was 0.79 μm. The average particle size (D50) of the solid electrolyte present at the interface was measured to be 1.38 μm for Example 1 and 0.83 μm for Comparative Example 1.

[0077] Because the solid electrolyte particles penetrate the pores of the negative electrode active material layer, the average particle size of the solid electrolyte present at the interface is smaller than the average particle size of the solid electrolyte contained in the solid electrolyte layer forming composition. The porosity of the negative electrode active material layer in Example 1 is lower than that of the negative electrode active material layer in Comparative Example 1, and the average diameter of the pores is smaller. Therefore, Example 1 shows that the average particle size of the solid electrolyte present at the interface is larger than that of Comparative Example 1.

[0078] Experimental Example 2. Measurement of Life Characteristics of All-Solid-State Batteries The life characteristics of the all-solid-state batteries in Example 1 and Comparative Example 1 were measured.

[0079] Lifetime characteristics were measured by charging the all-solid-state battery at 60°C in CCCV mode at 0.33C until it reached 4.25V, then discharging it to 3.0V with a constant current, and measuring the capacity retention rate after 50 charge-discharge cycles.

[0080] The results are shown in Figure 3.

[0081] In Example 1, the average particle size (D50) of the solid electrolyte at the interface between the negative electrode active material layer and the solid electrolyte layer is larger than that of Comparative Example 1. That is, the porosity of the negative electrode active material layer in Example 1 is lower than that of Comparative Example 1, and the average diameter of the pores is smaller, resulting in less solid electrolyte penetrating the pores than in Comparative Example 1. As a result, the all-solid-state battery in Example 1 showed superior lifespan characteristics. On the other hand, in Comparative Example 1, more solid electrolyte penetrated the pores than in Example 1, leading to increased side reactions and irreversible capacity between the negative electrode active material and the solid electrolyte, and resulting in decreased lifespan characteristics.

[0082] Therefore, it can be seen that the all-solid-state battery of the present invention has an average particle size (D50) of 1 to 3 μm of the solid electrolyte present at the interface between the negative electrode active material layer and the solid electrolyte layer, which reduces the amount of solid electrolyte that penetrates into the pores of the negative electrode active material layer and improves the lifespan characteristics of the all-solid-state battery.

Claims

1. A positive electrode containing a positive electrode active material layer; A negative electrode containing a negative electrode active material layer; A solid electrolyte layer comprising a solid electrolyte interposed between the positive electrode active material layer and the negative electrode active material layer; The aforementioned negative electrode active material layer includes a carbon-based material, An all-solid-state battery in which the average particle size of the solid electrolyte present at the interface between the negative electrode active material layer and the solid electrolyte layer is 1 μm or more and 3 μm or less.

2. The all-solid-state battery according to claim 1, wherein the porosity of the negative electrode active material layer is 15% or more and 40% or less.

3. The all-solid-state battery according to claim 2, wherein the average diameter of the pores in the negative electrode active material layer is 0.5 μm or more and less than 0.7 μm.

4. The all-solid-state battery according to claim 1, wherein the carbon-based material comprises one or more selected from the group consisting of natural graphite, artificial graphite, hard carbon, soft carbon, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon nanotubes, fullerene, carbon fiber, and fluorinated carbon.

5. The negative electrode active material layer further contains a metal, The all-solid-state battery according to claim 1, wherein the metal comprises one or more selected from the group consisting of nickel, copper, silver, gold, platinum, aluminum, zinc, palladium, and bismuth.

6. The all-solid-state battery according to claim 1, wherein the average particle size of the solid electrolyte is 2 μm or more and 4 μm or less.

7. The all-solid-state battery according to claim 1, 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.

8. The all-solid-state battery according to claim 7, wherein the solid electrolyte includes a sulfide-based solid electrolyte.

9. (1) A step of mixing carbon-based material, binder and solvent to produce a composition for forming a negative electrode active material layer; (2) A step of applying and drying the negative electrode active material layer forming composition onto the negative electrode current collector to form the negative electrode active material layer; (3) A step of pressurizing the negative electrode active material layer to manufacture the negative electrode; (4) A step of mixing a solid electrolyte, a binder, and a solvent to produce a composition for forming a solid electrolyte layer; (5) The step of applying and drying the solid electrolyte layer formation composition onto the negative electrode active material layer to produce a solid electrolyte layer; and (6) A step of stacking a positive electrode on the solid electrolyte layer; a method for manufacturing an all-solid-state battery according to any one of claims 1 to 8.

10. The method for manufacturing an all-solid-state battery according to claim 9, wherein the pressurization in step (3) is 30 MPa or more and 500 MPa or less.

11. The method for manufacturing an all-solid-state battery according to claim 9, wherein the positive electrode is manufactured by applying and drying a composition for forming a positive electrode active material layer, which includes a positive electrode active material, a binder, and a solvent, onto a positive electrode current collector.

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