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

Abstract

The present invention relates to an all-solid-state battery and a manufacturing method thereof. More specifically, in an all-solid-state battery according to the present invention, in a unit cell in which a cathode layer, a solid electrolyte layer, and an anode layer are stacked, the cross-sectional shapes and areas of the cathode layer, the solid electrolyte layer, and the anode layer are made identical to each other, which may improve structural stability.

Description

[Technical Field]

[0001] Cross-Citation of Related Applications This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0157932, filed November 15, 2023, and all contents disclosed in the documents of said Korean patent application are incorporated herein by reference.

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

[0003] Currently, various batteries that can overcome the limitations of lithium secondary batteries are being researched from the viewpoints of battery capacity, stability, output, size increase, and miniaturization.

[0004] Representative examples of batteries that are being continuously researched in academia and industry include metal-air batteries, which have a much larger theoretical capacity than lithium secondary batteries, all-solid-state batteries, which are stable and do not pose a risk of explosion, supercapacitors, NaS batteries or RFBs (redox flow batteries), which are large-sized batteries, and thin film batteries, which are ultra-small.

[0005] All-solid-state batteries are batteries that replace the liquid electrolyte used in conventional lithium secondary batteries with a solid, and because they do not use flammable solvents, they are completely free of fires and explosions caused by the decomposition reaction of conventional electrolytes, thereby significantly improving stability. Furthermore, because lithium metal or lithium alloys can be used as the anode material, they have the advantage of dramatically improving the energy density relative to the mass and volume of the battery.

[0006] However, in the cell assembly process for solid-state batteries, each electrode is stacked one by one on top of the pouch, but there are limitations to how precisely the cells can be aligned. When stacking cells to improve energy density, using cells that are not precisely aligned can result in an unstable stack structure, which can lead to cracks and short circuits.

[0007] 1a to 1c are schematic diagrams showing the longitudinal cross section of an all-solid-state battery according to the prior art (1a: longitudinal cross section of a unit cell, 1b: longitudinal cross section of a stack cell, 1c: longitudinal cross section of a laminate including a positive electrode layer and a solid electrolyte layer).

[0008] A unit cell (100) of a conventional all-solid-state battery has a structure in which a positive electrode current collector (111), a positive electrode active material layer (112), a solid electrolyte layer (120), and a negative electrode layer (130) are sequentially stacked (FIG. 1a). A stack cell (200) is formed by stacking a plurality of unit cells (100), for example, two or more unit cells (100) (FIG. 1b). When manufacturing the unit cell (100), the area of ​​the positive electrode layer (110) including the positive electrode current collector (111) and the positive electrode active material layer (112) is smaller than the adjacent solid electrolyte layer (120). Therefore, it is difficult to align the solid electrolyte layer (120) on the positive electrode layer (110), and misalignment can occur (FIG. 1c). Generally, if the positive electrode layer expands and contacts the negative electrode layer, or if misalignment occurs during the assembly process, causing the two electrode layers to come into contact and a short circuit occurs, so the positive electrode layer is designed to be smaller than the solid electrolyte layer, which acts as a separator. In addition, after the components described above are stacked, when pressure is applied, cracks (C) occur in the solid electrolyte layer (120) due to the difference in area between the adjacent positive electrode active material layer (112) and solid electrolyte layer (120), causing the stacked structure itself to collapse (D), which can cause contact between the positive electrode layer and the negative electrode layer.

[0009] FIG. 2 shows the structure of the all-solid-state battery disclosed in Patent Document 1.

[0010] Referring to FIG. 2, the structural stability of the all-solid-state battery is ensured by providing a spacer 50 made of a polymer to fill the space created by the smaller area of ​​the anode layer 40 than the solid electrolyte layer 30. The spacer 50 is made of a polymer containing at least one selected from the group consisting of polyethylene, polyethylene naphthalate, polyethylene terephthalate, and combinations thereof. Because the spacer 50 is a different material from the anode layer, when pressure is applied during the pressurization process during the fabrication of the all-solid-state battery, even if the anode layer 40 is not damaged, cracks may occur in the spacer 50 and the solid electrolyte layer 30, which bears the load. This phenomenon is particularly prevalent in stack cells.

[0011] Therefore, to ensure high stability of all-solid-state batteries, there is a need to develop technology that can easily achieve a certain alignment when assembling cells and thereby ensure structural stability. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Korean Patent Publication No. 2022-0080930 Summary of the Invention [Problem to be solved by the invention]

[0013] As a result of extensive research into solving the above problems, the inventors have confirmed that in an all-solid-state battery including a unit cell or a stack cell in which a plurality of unit cells are stacked, the structural stability of the all-solid-state battery can be ensured by forming a unit cell including a positive electrode layer, a solid electrolyte layer, and a negative electrode layer, and designing the cross-sectional shapes and areas of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer to be identical.

[0014] Therefore, an object of the present invention is to provide an all-solid-state battery that ensures structural stability and a method for manufacturing the same. [Means for solving the problem]

[0015] In order to achieve the above object, the present invention provides an all-solid-state battery including a unit cell, The unit cell comprises: a positive electrode current collector; a positive electrode active material layer in contact with a certain area of ​​one surface of the positive electrode current collector; a solid electrolyte layer that surrounds one surface of the positive electrode active material layer and a side surface adjacent to the one surface and is formed in contact with the positive electrode current collector; and a negative electrode layer located on the solid electrolyte layer and having the same area as the solid electrolyte layer.

[0016] In one embodiment of the present invention, there is provided an all-solid-state battery, wherein the area of ​​the solid electrolyte layer is 1.3 to 1.8 times larger than the area of ​​the positive electrode active material layer.

[0017] In one embodiment of the present invention, there is provided an all-solid-state battery, wherein the anode layer includes: an anode current collector; and an anode active material layer formed on the anode current collector, the anode active material layer being stacked so as to be in contact with the solid electrolyte layer.

[0018] In one embodiment of the present invention, there is provided an all-solid-state battery, wherein the anode layer includes: an anode current collector; and an anode-less coating layer formed on the anode current collector; and the anode-less coating layer is laminated so as to be in contact with the solid electrolyte layer.

[0019] In one embodiment of the present invention, there is provided an all-solid-state battery, wherein two or more unit cells are stacked.

[0020] In one embodiment of the present invention, the all-solid-state battery is a pouch-type all-solid-state battery.

[0021] The present invention also provides a method for manufacturing a cathode active material using a cathode current collector, comprising the steps of: (S1) forming a cathode active material layer having a predetermined area on the cathode current collector; (S2) forming a solid electrolyte layer on the positive electrode active material layer so as to surround one surface of the positive electrode active material layer and a side surface adjacent to the one surface; (S3) forming an anode layer on the solid electrolyte layer, the anode layer having the same area as the solid electrolyte layer; (S4) applying pressure in a stacking direction to bond the positive electrode current collector, the positive electrode active material layer, the solid electrolyte layer, and the negative electrode layer.

[0022] In one embodiment of the present invention, there is provided a method for manufacturing an all-solid-state battery, wherein the pressure is 300 MPa to 700 MPa. [Effects of the Invention]

[0023] The unit cell included in the all-solid-state battery of the present invention has a structure in which a positive electrode layer, a solid electrolyte layer, and a negative electrode layer are sequentially stacked, and the positive electrode layer, solid electrolyte layer, and a negative electrode layer have the same shape and cross section, and therefore have structural stability, and therefore damage such as cracking and stretching can be prevented even in the step of bonding them under pressure during production.

[0024] In addition, even when two or more unit cells are stacked to form a stack cell in order to improve energy density, the structure is stable and the battery can exhibit excellent life characteristics. [Brief explanation of the drawings]

[0025] [Figure 1a] 1A is a schematic diagram showing a longitudinal section of an all-solid-state battery according to the prior art (1a: longitudinal section of a unit cell). FIG. [Figure 1b] 1A and 1B are schematic diagrams showing a longitudinal section of an all-solid-state battery according to the prior art (1B: longitudinal section of a stack cell). [Figure 1c] 1A and 1B are schematic diagrams showing a longitudinal section of an all-solid-state battery according to the prior art (1c: longitudinal section of a laminate including a positive electrode layer and a solid electrolyte layer). [Figure 2] This is the structure of an all-solid-state battery disclosed in Patent Document 1. [Figure 3a]3A is a schematic diagram showing a vertical cross section of an all-solid-state battery according to the present invention (3a: vertical cross section of a unit cell). FIG. [Figure 3b] 3A is a schematic diagram showing a vertical cross section of an all-solid-state battery according to the present invention (3b: vertical cross section of a stack cell). FIG. [Figure 3c] 3A and 3B are schematic diagrams showing a vertical cross section of an all-solid-state battery according to the present invention (3c: vertical cross section of a laminate including a positive electrode layer and a solid electrolyte layer). [Figure 4a] 4A and 4B are schematic diagrams illustrating the manufacturing process of a unit cell according to a preferred embodiment of the present invention (4a: positive electrode arrangement). [Figure 4b] 4A and 4B are schematic diagrams illustrating the manufacturing process of a unit cell according to a preferred embodiment of the present invention (FIG. 4B: Manufacturing of a solid electrolyte layer). [Figure 4c] 4A to 4C are schematic diagrams illustrating a manufacturing process of a unit cell according to a preferred embodiment of the present invention (FIG. 4C: schematic diagrams of the top and longitudinal cross sections of the manufactured solid electrolyte layer). [Figure 4d] 4A to 4D are schematic diagrams illustrating a manufacturing process of a unit cell according to a preferred embodiment of the present invention (4D: cutting of a laminate including a positive electrode layer and a solid electrolyte layer). DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention will now be described in more detail to aid in its understanding.

[0027] The terms and words used in this specification and claims should not be construed as being limited to their ordinary or dictionary meanings, but should be construed in a meaning and concept that is consistent with the technical idea of ​​the present invention, based on the principle that an inventor can appropriately define the concept of a term in order to best explain his or her invention.

[0028] All solid state battery The present invention relates to an all-solid-state battery.

[0029] The all-solid-state battery according to the present invention includes a unit cell, The unit cell comprises: positive electrode current collector, a positive electrode active material layer in contact with a certain area of ​​one surface of the positive electrode current collector; a solid electrolyte layer that surrounds one surface of the positive electrode active material layer and a side surface adjacent to the one surface and is formed in contact with the positive electrode current collector; a negative electrode layer located on the solid electrolyte layer and having the same area as the solid electrolyte layer.

[0030] The all-solid-state battery according to the present invention does not contain any other materials except for the positive electrode layer, the solid electrolyte layer, and the negative electrode layer, and therefore can prevent problems such as structural instability and deterioration of battery performance due to the addition of other materials.

[0031] Therefore, the unit cell of the all-solid-state battery may be composed of a positive electrode layer, a solid electrolyte layer, and a negative electrode layer.

[0032] 3a to 3c are schematic diagrams showing the longitudinal cross section of a unit cell included in an all-solid-state battery according to one embodiment of the present invention (3a: longitudinal cross section of a unit cell, 3b: longitudinal cross section of a stack cell, 3c: longitudinal cross section of a laminate including a positive electrode layer and a solid electrolyte layer).

[0033] Referring to Figures 3a to 3c, the unit cell (100) included in the all-solid-state battery has a structure in which a positive electrode current collector (111), a positive electrode active material layer (112), a solid electrolyte layer (120), and a negative electrode layer (130) are sequentially stacked.

[0034] The positive electrode active material layer (112) is in contact with one surface of the positive electrode current collector (111) and is in contact with a certain area of ​​the surface. In addition to the surface in contact with the positive electrode current collector (111), the other surface of the positive electrode active material layer (112) and four side surfaces adjacent to the other surface are surrounded by the solid electrolyte layer (120). In this case, the surface of the positive electrode active material layer (112) in contact with the positive electrode current collector (111) can be referred to as the first surface, the other surface as the second surface, and the four side surfaces adjacent to the first and second surfaces can be referred to as the first side, second side, third side, and fourth side.

[0035] The unit cells (100) or the stack cell (200) formed by stacking these units may have a rectangular parallelepiped shape, and the cross sections of the positive electrode current collector (111), the solid electrolyte layer (120), and the negative electrode layer (130) have the same area and shape. In addition, in the portion where the side surface of the positive electrode active material layer (112) is surrounded by the solid electrolyte layer (120), the area and shape of the cross section of the positive electrode active material layer (112) plus the cross section of the solid electrolyte layer (120) may be the same as the area and shape of the positive electrode current collector (111) (FIGS. 3a and 3b).

[0036] Since the unit cell (100) has a rectangular parallelepiped shape and is structurally stable, it is easy to align the unit cell (100) during manufacturing, and as described above, even when the components are stacked and pressurized, phenomena such as cracking, stretching, or cell shorting can be prevented (Figure 3c).

[0037] In one embodiment of the present invention, the positive electrode layer includes a positive electrode current collector and a positive electrode active material layer formed on one surface of the positive electrode current collector.

[0038] The positive electrode current collector supports the positive electrode active material layer and serves to transfer electrons between an external conductor and the positive electrode active material layer.

[0039] The positive electrode current collector is not particularly limited as long as it does not cause a chemical change in the all-solid-state battery and has high electronic conductivity. For example, the positive electrode current collector can be made of aluminum, nickel, titanium, palladium, baked carbon, copper, stainless steel, copper or stainless steel whose surface is treated with carbon, nickel, silver, or the like, or an aluminum-cadmium alloy.

[0040] In addition, the positive electrode current collector may have a fine uneven structure on its surface or a three-dimensional porous structure to strengthen the bonding strength with the positive electrode active material layer, and thus may have various forms such as a film, sheet, foil, mesh, net, porous material, foam, or nonwoven fabric.

[0041] The positive electrode active material layer may be formed to have an area smaller than that of the positive electrode current collector and may be positioned on the positive electrode current collector.

[0042] The positive electrode active material layer includes a positive electrode active material, a solid electrolyte, a conductive material, and a binder.

[0043] The positive electrode active material is not particularly limited as long as it is a material capable of reversibly absorbing and releasing lithium ions. For example, lithium cobalt oxide (LiCoO), lithium nickel oxide (LiNiO), Li[Ni x Co y Mn z M v ]O2 (wherein M is any one or more elements selected from the group consisting of Al, Ga, and In; 0.3≦x<1.0, 0≦y, z≦0.5, 0≦v≦0.1, and x+y+z+v=1), Li (Li a M b-a-b’ M' b’ )O 2-c A c (wherein 0≦a≦0.2, 0.6≦b≦1, 0≦b'≦0.2, 0≦c≦0.2; M includes Mn and one or more elements selected from the group consisting of Ni, Co, Fe, Cr, V, Cu, Zn, and Ti; M' is one or more elements selected from the group consisting of Al, Mg, and B; and A is one or more elements selected from the group consisting of P, F, S, and N); layered compounds and compounds substituted with one or more transition metals, such as compounds of the formula Li 1+y Mn 2-y Lithium manganese oxides such as LiMnO4 (where y is 0 to 0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, and Cu2V2O7; and the chemical formula LiNi 1-y Ni-site lithium nickel oxide represented by MyO2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and y is 0.01 to 0.3); chemical formula: LiMn 2-y M yExamples of suitable lithium manganese composite oxides include, but are not limited to, lithium manganese composite oxides represented by LiMnO2 (where M is Co, Ni, Fe, Cr, Zn, or Ta, and y is 0.01 to 0.1) or Li2Mn3MO8 (where M is Fe, Co, Ni, Cu, or Zn); LiMn2O4, in which part of the Li in the chemical formula is replaced with an alkaline earth metal ion; disulfide compounds; and Fe2(MoO4)3.

[0044] The positive electrode active material may be contained in an amount of 60 wt% to 80 wt% based on the total weight of the positive electrode active material layer. Specifically, the content of the positive electrode active material may be 60 wt%, 65 wt% or more, or 68 wt% or more, and may be 72 wt% or less, 75 wt% or less, or 80 wt% or less. If the content of the positive electrode active material is less than 60 wt%, battery performance may be reduced, and if it exceeds 80 wt%, mass transfer resistance may be increased.

[0045] In addition, the solid electrolyte may have an argyrodite structure, and specifically, may include a sulfide-based solid electrolyte, a halide-based solid electrolyte, or an oxide-based solid electrolyte.

[0046] The sulfide-based solid electrolyte may include a compound represented by the following Chemical Formula 1 or a mixture thereof: [Chemical formula 1] Li a M b S c X d In the formula 1, M is selected from P, Sn, Sb, As, and Ge; X is selected from Cl, Br, and I; 5≦a≦7.5, and 0.5 <b≦1.5であり、4<c≦6であり、0.5<d≦2である。

[0047] The halide-based solid electrolyte may be represented by the following chemical formula 2: [Chemical formula 2] Li 6-3aM a Br b Cl c In the above formula 2, M is a metal other than Li, and a is 0. <a<2であり、bは0≦b≦6であり、cは0≦c≦6であり、b+c=6である。

[0048] For example, the halide-based solid electrolyte may contain one or more selected from the group consisting of Li3YBr6, Li3YCl6, and Li3YBr2Cl4.

[0049] The oxide-based solid electrolyte is Li 3x La 2 / 3-x LLT series with perovskite structure such as TiO3, Li 14 LISICON systems such as Zn(GeO4)4, Li 1.3 Al 0.3 Ti 1.7 LATP systems such as (PO4)3, (Li 1+x Ge 2-x Al x The LAGP type such as (PO4)3) or the phosphate type such as LiPON may be appropriately selected and used, but is not particularly limited to these.

[0050] The conductive material is not particularly limited as long as it prevents side reactions in the internal environment of the all-solid-state battery, does not cause chemical changes in the battery, and has excellent electrical conductivity. Typical examples include graphite or conductive carbon, such as natural graphite and artificial graphite; carbon black, such as carbon black, acetylene black, ketjen black, denka black, thermal black, channel black, furnace black, lamp black, and thermal black; carbon-based materials with graphene or graphite crystal structures; conductive fibers, such as carbon fiber and metal fiber; carbon fluoride; metal powders, such as aluminum powder and nickel powder; conductive whiskers, such as zinc oxide and potassium titanate; conductive oxides, such as titanium oxide; and conductive polymers, such as polyphenylene derivatives. The conductive material may be vapor-grown carbon fiber (VGCF), either alone or in combination.

[0051] The conductive material may typically be included in an amount of 1 wt% to 5 wt% based on the total weight of the positive electrode active material layer. Specifically, the content of the conductive material may be 1 wt% or more, 1.5 wt% or more, or 2 wt% or more, and 4 wt% or less, 4.5 wt% or less, or 5 wt% or less. If the content of the conductive material is too low, such as less than 1 wt%, the improvement in electrical conductivity may not be expected or the electrochemical characteristics of the battery may be reduced. If the content is too high, such as more than 5 wt%, the amount of positive electrode active material may be relatively small, resulting in reduced capacity and energy density. The method for incorporating the conductive material into the positive electrode is not significantly limited, and conventional methods known in the art, such as mixing with the positive electrode active material or coating, may be used.

[0052] The binder is a component that assists in binding the positive electrode active material to the conductive material and the current collector, and is preferably a material selected from the group consisting of styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, and polyacrylonitrile. , polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene. Preferably, the binder may include polytetrafluoroethylene (PTFE).

[0053] The binder may be contained in an amount of 0.5 wt % to 4 wt % based on the total weight of the positive electrode active material layer. Specifically, the binder content may be 0.5 wt % or more, 1 wt % or more, or 1.5 wt % or more, and may be 3 wt % or less, 3.5 wt % or less, or 4 wt % or less. If the binder content is less than 0.5 wt %, the adhesive strength between the positive electrode active material and the positive electrode current collector may decrease. If the binder content exceeds 4 wt %, the adhesive strength may improve, but the content of the positive electrode active material may decrease accordingly, resulting in a decrease in battery capacity.

[0054] In one embodiment of the present invention, the solid electrolyte layer may be 1.3 to 1.8 times larger than the area of ​​the positive electrode active material layer, where the areas of the solid electrolyte layer and the positive electrode active material layer refer to the areas when the solid electrolyte layer and the positive electrode active material layer are viewed from above.

[0055] The solid electrolyte layer is formed to surround one surface of the positive electrode active material layer and a side surface adjacent to the one surface, and therefore has a larger area than the positive electrode active material layer. If the area of ​​the solid electrolyte layer is less than 1.3 times the area of ​​the positive electrode active material layer, a step may occur between the solid electrolyte layer and the positive electrode current collector or the negative electrode layer. If the area of ​​the solid electrolyte layer is more than 1.8 times, the migration path of lithium ions may become longer or production costs may increase.

[0056] The solid electrolyte layer may contain a sulfide-based solid electrolyte, a halide-based solid electrolyte, or an oxide-based solid electrolyte. From the viewpoint of lithium ion conductivity, the solid electrolyte layer may contain a sulfide-based solid electrolyte.

[0057] The sulfide-based solid electrolyte may include a compound represented by the following Chemical Formula 1 or a mixture thereof: [Chemical formula 1] Li a M b S c X d In the formula 1, M is selected from P, Sn, Sb, As, and Ge; X is selected from Cl, Br, and I; 5≦a≦7.5, and 0.5 <b≦1.5であり、4<c≦6であり、0.5<d≦2である。

[0058] The halide-based solid electrolyte may be represented by the following chemical formula 2: [Chemical formula 2] Li 6-3a M a Br b Cl c In the above formula 2, M is a metal other than Li, and a is 0. <a<2であり、bは0≦b≦6であり、cは0≦c≦6であり、b+c=6である。

[0059] For example, the halide-based solid electrolyte may contain one or more selected from the group consisting of Li3YBr6, Li3YCl6, and Li3YBr2Cl4.

[0060] The oxide-based solid electrolyte is Li 3x La 2 / 3-x LLT series with perovskite structure such as TiO3, Li 14 LISICON systems such as Zn(GeO4)4, Li 1.3 Al 0.3 Ti 1.7 LATP systems such as (PO4)3, (Li 1+x Ge 2-x Al x The LAGP type such as (PO4)3) or the phosphate type such as LiPON may be appropriately selected and used, but is not particularly limited to these.

[0061] In one embodiment of the present invention, the negative electrode layer may include: a negative electrode current collector; and a negative electrode active material layer formed on the negative electrode current collector, wherein the negative electrode active material layer is stacked in contact with the solid electrolyte layer.

[0062] Alternatively, the negative electrode layer may include a negative electrode current collector and a negative electrode-less coating layer formed on the negative electrode current collector, the negative electrode-less coating layer being laminated so as to be in contact with the solid electrolyte layer.

[0063] The negative electrode active material layer includes a negative electrode active material, a binder, and a conductive material.

[0064] The negative electrode active material is lithium (Li +The material may include a material capable of reversible intercalation or deintercalation of . ) , a material capable of reacting with lithium ions to reversibly form a lithium-containing compound, lithium metal, or a lithium alloy.

[0065] The lithium ion (Li + The material capable of reversibly inserting or de-inserting lithium ions (Li) may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. + The material capable of reacting with lithium (Li) to reversibly form a lithium-containing compound may be, for example, tin oxide, titanium nitrate, or silicon. The lithium alloy may be, for example, an alloy of lithium (Li) and a metal selected from the group consisting of indium (In), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al), and tin (Sn).

[0066] Preferably, the negative electrode active material may be lithium metal or a lithium-indium alloy (Li-In), and specifically, may be in the form of a lithium metal or lithium thin film, or a lithium-indium alloy thin film or powder.

[0067] The negative electrode active material may be included in an amount of 40 wt % to 80 wt % based on the total weight of the negative electrode active material layer. Specifically, the content of the negative electrode active material may be 40 wt % or more or 50 wt % or more, and may be 70 wt % or less or 80 wt % or less. If the content of the negative electrode active material is less than 40 wt %, the connectivity between the wet negative electrode active material layer and the dry negative electrode active material layer may be insufficient, and if it exceeds 80 wt %, the mass transfer resistance may be increased.

[0068] The binder is a component that assists in binding the negative electrode active material to the conductive material and the like and in binding the negative electrode current collector, and is preferably a rubber such as styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylontrile, The binder may include one or more selected from the group consisting of polyethylene terephthalate (PET) polymer, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene. Preferably, the binder may include polytetrafluoroethylene (PTFE).

[0069] The binder may be contained in an amount of 0.5 wt % to 4 wt % based on the total weight of the negative electrode active material layer. Specifically, the binder content may be 0.5 wt % or more, 1 wt % or more, or 1.5 wt % or more, and may be 3 wt % or less, 3.5 wt % or less, or 4 wt % or less. If the binder content is less than 0.5 wt %, the adhesive strength between the positive electrode active material and the negative electrode current collector may decrease. If the binder content exceeds 4 wt %, the adhesive strength will improve, but the content of the negative electrode active material will decrease accordingly, and the battery capacity may decrease.

[0070] The conductive material is not particularly limited as long as it prevents side reactions in the internal environment of the all-solid-state battery, does not cause chemical changes in the battery, and has excellent electronic conductivity. Typical examples include graphite or conductive carbon, such as natural graphite and artificial graphite; carbon black, such as carbon black, acetylene black, ketjen black, denka black, thermal black, channel black, furnace black, lamp black, and thermal black; carbon-based materials with a graphene or graphite crystalline structure; conductive fibers, such as carbon fiber and metal fiber; carbon fluoride; metal powders, such as aluminum powder and nickel powder; conductive whiskers, such as zinc oxide and potassium titanate; conductive oxides, such as titanium oxide; and conductive polymers, such as polyphenylene derivatives. The conductive material may be vapor-grown carbon fiber (VGCF), either alone or in combination.

[0071] The conductive material may typically be included in an amount of 1 wt % to 5 wt % based on the total weight of the negative electrode active material layer. Specifically, the content of the conductive material may be 1 wt % or more, 1.5 wt % or more, or 2 wt % or more, and 4 wt % or less, 4.5 wt % or less, or 5 wt % or less. If the content of the conductive material is too low, such as less than 1 wt %, the effect of improving electronic conductivity may not be expected or the electrochemical characteristics of the battery may be degraded. If the content is too high, such as more than 5 wt %, the amount of negative electrode active material may be relatively small, resulting in reduced capacity and energy density. The method for incorporating the conductive material into the negative electrode is not particularly limited, and may be a conventional method known in the art, such as mixing with the negative electrode active material or coating.

[0072] The negative electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and is conductive, and examples of the negative electrode current collector that can be used include copper, stainless steel, aluminum, nickel, titanium, baked carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. Similarly to the positive electrode current collector, the negative electrode current collector can be in various forms such as a film, sheet, foil, net, porous material, foam, nonwoven fabric, etc., with fine irregularities formed on the surface.

[0073] The method for manufacturing the negative electrode is not particularly limited, and the negative electrode may be manufactured by forming a negative electrode active material layer on a negative electrode current collector using a layer or film formation method commonly used in the art. For example, methods such as compression bonding, coating, and vapor deposition may be used. In addition, the negative electrode of the present invention also includes a case where a battery is assembled without a lithium thin film on the negative electrode current collector, and then a metallic lithium thin film is formed on the metal plate by initial charging.

[0074] In addition, the anode-less coating layer does not contain an anode active material, and an anode active material may be formed in the anode-less coating layer upon charging. For example, lithium ions may migrate from the positive electrode during charging of the battery, resulting in the deposition of lithium metal from the negative electrode. That is, the anode-less coating layer may be a film that induces the deposition of lithium.

[0075] The anode-less coating layer may contain metal particles and carbon material particles, and specifically may contain a carbon material-metal composite.

[0076] The carbon material particles may be, for example, amorphous carbon material particles. However, the carbon material particles are not limited to amorphous particles. Specific examples of the amorphous carbon material include carbon black such as acetylene black, furnace black, and ketjen black, graphene, or a combination thereof.

[0077] The metal particles may be particles that form an alloy with lithium, and may be particles of one or more types selected from silver (Ag), gold, platinum, palladium, silicon, aluminum, bismuth, tin, indium, and zinc. The negative electrode coating layer may be formed as a very thin film with a micron thickness, for example, with a thickness of 10 μm or less.

[0078] Preferably, the negative electrode-less coating layer may contain an Ag-C composite as the carbon material-metal composite, and lithium may be deposited between the negative electrode current collector and the coating layer containing the Ag-C composite during the first charge.

[0079] In one embodiment of the present invention, two or more unit cells may be stacked to form a stack cell.

[0080] Since the unit cell has a rectangular parallelepiped shape, even when two or more unit cells are stacked, the stack cell also has a rectangular parallelepiped shape, thereby providing structural stability.

[0081] In one embodiment of the present invention, the all-solid-state battery may be a pouch-type all-solid-state battery.

[0082] Manufacturing method for all-solid-state batteries The present invention also relates to a method for manufacturing an all-solid-state battery.

[0083] The method for manufacturing an all-solid-state battery according to the present invention includes a unit cell manufacturing process including the following steps (S1) to (S4): (S1) forming a positive electrode active material layer of a certain area on a positive electrode current collector; (S2) forming a solid electrolyte layer on the positive electrode active material layer so as to surround one surface of the positive electrode active material layer and a side surface adjacent to the one surface; (S3) forming an anode layer on the solid electrolyte layer, the anode layer having the same area as the solid electrolyte layer; (S4) applying pressure in a stacking direction of the positive electrode current collector, the positive electrode active material layer, the solid electrolyte layer, and the negative electrode layer to bond them together.

[0084] Hereinafter, each step of the method for manufacturing an all-solid-state battery according to the present invention will be described in more detail.

[0085] In one embodiment of the present invention, in step (S1), a positive electrode active material layer having a certain area may be formed on the positive electrode current collector.

[0086] The area of ​​the positive electrode current collector may be larger than the area of ​​the positive electrode active material layer. The area of ​​the positive electrode current collector may be 1.3 to 1.8 times the area of ​​the positive electrode active material layer. The area of ​​the positive electrode current collector is the same as the area of ​​the solid electrolyte layer, which may be advantageous for producing a rectangular parallelepiped unit cell.

[0087] The positive electrode active material layer can be fabricated by mixing a positive electrode active material, a solid electrolyte, a conductive material, and a binder in an organic solvent to form a positive electrode active material layer composition, applying the composition to a positive electrode current collector, drying the composition, and optionally compression-molding the composition onto the positive electrode current collector to improve electrode density. The organic solvent is preferably one that can uniformly disperse the positive electrode active material, the solid electrolyte, the binder, and the conductive material and that is easily evaporated. Specific examples of the organic solvent include acetonitrile, methanol, ethanol, xylene, toluene, hexane, tetrahydrofuran, and isopropyl alcohol.

[0088] In one embodiment of the present invention, in step (S2), a solid electrolyte layer may be formed on the positive electrode active material layer to surround one surface of the positive electrode active material layer and side surfaces adjacent to the one surface. In the positive electrode active material layer, one surface in contact with the positive electrode current collector may be referred to as a first surface, the other surface may be referred to as a second surface, and four side surfaces adjacent to the first and second surfaces may be referred to as a first side, a second side, a third side, and a fourth side.

[0089] The solid electrolyte layer is formed on the positive electrode active material layer, and is also formed to surround the second surface and the first to fourth side surfaces of the positive electrode active material. In addition, since the area of ​​the positive electrode current collector is larger than the area of ​​the positive electrode active material layer, the solid electrolyte layer is also formed in contact with the positive electrode current collector on which the positive electrode active material layer is not in contact.

[0090] The solid electrolyte layer may be prepared by mixing a solid electrolyte and a binder in a solvent to obtain a slurry, coating the slurry on the positive electrode active material layer, and then drying the slurry.

[0091] As described above, the solid electrolyte may include one or more selected from the group consisting of sulfide-based solid electrolytes, halide-based solid electrolytes, and oxide-based solid electrolytes.

[0092] The binder may contain at least one selected from the group consisting of acrylic copolymers, acrylic block copolymers, acrylic monomers, random copolymers of oligomers, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymers, acrylonitrile-butadiene rubber, nitrile-butadiene rubber, acrylonitrile-styrene-butadiene copolymers, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, and ethylene / propylene copolymers.

[0093] The binder may be contained in an amount of 5 to 15 parts by weight per 100 parts by weight of the solid electrolyte. Specifically, the content of the binder may be 5 parts by weight or more, 7 parts by weight or more, or 9 parts by weight or more, or 11 parts by weight or less, 13 parts by weight or less, or 15 parts by weight or less. If the content of the binder is less than 5 parts by weight, it may be difficult to form a solid electrolyte layer, and if it exceeds 15 parts by weight, ion conductivity may decrease.

[0094] The solvent is not particularly limited as long as it dissolves and / or disperses the solid electrolyte and / or binder to form a slurry. For example, the solvent may be at least one selected from the group consisting of dimethyl sulfoxide (DMSO), isopropyl alcohol, ethyl butyrate, heptyl butyrate, hexyl butyrate, butyl butyrate, isopropyl butyrate, isobutyl isobutyrate, N-methylpyrrolidone (NMP), acetone, xylene, N,N-dimethylmethanamide (DMF), benzene, tetrahydrofuran (THF), and water. The amount of the solvent used may be adjusted taking into account the thickness of the coating layer and the physical properties of the solid electrolyte to be produced.

[0095] The coating method may be bar coating, roll coating, spin coating, slit coating, die coating, blade coating, comma coating, slot die coating, lip coating, or solution casting, but is not limited thereto as long as it is a method that can form a layer by coating.

[0096] The drying method is not particularly limited as long as it can evaporate the solvent after coating to form a layer. For example, the drying may be performed at 300°C or less. Specifically, the drying temperature may be 300°C or less, 200°C or less, 150°C or less, or 100°C or less.

[0097] In one embodiment of the present invention, in step (S3), an anode layer having the same area as the solid electrolyte layer may be stacked on the solid electrolyte layer.

[0098] In one embodiment of the present invention, in step (S4), the positive electrode current collector, the positive electrode active material layer, the solid electrolyte layer, and the negative electrode layer may be bonded by applying pressure in a stacking direction.

[0099] The pressure may be 300 MPa to 700 MPa, specifically, 300 MPa or more, 350 MPa or more, or 400 MPa or more, or 500 MPa or less, 550 MPa or less, 600 MPa or less, 650 MPa or less, or 700 MPa. If the pressure is less than 300 MPa, the internal adhesion of the all-solid-state battery may be poor, and if it exceeds 700 MPa, cracks may occur between the positive electrode and the electrolyte in the case of misalignment.

[0100] According to a preferred embodiment of the present invention, FIGS. 4a to 4d are schematic diagrams of a unit cell manufacturing process (4a: cathode placement, 4b: solid electrolyte layer manufacturing, 4c: schematic diagrams of the top and longitudinal cross section of the manufactured solid electrolyte layer, 4d: cutting of a laminate including a cathode layer and a solid electrolyte layer). A unit cell can be manufactured according to the above manufacturing process as follows:

[0101] A plurality of positive electrode layers (110) punched out on a PET release film (R.F.) are arranged (Fig. 4a). Then, after coating a slurry (S) for forming a solid electrolyte with a doctor blade (D.B.) (Fig. 4b), it is dried to form a solid electrolyte layer (120) (Fig. 4c). The laminate of the positive electrode layer and the solid electrolyte layer is cut per one positive electrode layer (Fig. 4d). The area of the solid electrolyte layer is formed larger than the area of the positive electrode active material layer included in the positive electrode layer. The slurry for forming the solid electrolyte is manufactured by mixing Li6PS5Cl, which is sulfide-based solid electrolyte particles having an argyrodite structure, a rubber-based binder, and a butyrate-based solvent. At this time, the area of the positive electrode active material layer is A 2 mm 2 , the area of the solid electrolyte layer is B 2 mm 2 , after setting the interval between the positive electrode layers to C mm when arranging the positive electrode layers, the process was performed so that C < A < B and C = (B - A).

[0102] Then, a negative electrode layer is laminated on the solid electrolyte layer, and it is pressurized at a pressure of 400 MPa to manufacture a unit cell. In the unit cell, the area of the positive electrode current collector included in the positive electrode layer, the combined area of the positive electrode active material layer and the solid electrolyte layer surrounding it, the area of the solid electrolyte layer, and the area of the negative electrode layer are the same.

[0103] Two of the unit cells may be laminated to manufacture a stack cell.

[0104] As described above, the present invention has been described with reference to limited examples and drawings, but the present invention is not limited thereby, and it is natural that various modifications and variations can be made by those having ordinary knowledge in the technical field to which the present invention belongs within the equivalent scope of the technical idea of the present invention and the claims described below.

Explanation of Reference Numerals

Claims

1. An all-solid-state battery including a unit cell, The unit cell comprises: a positive electrode current collector; a positive electrode active material layer in contact with a certain area of ​​one surface of the positive electrode current collector; a solid electrolyte layer that surrounds one surface of the positive electrode active material layer and a side surface adjacent to the one surface and is formed in contact with the positive electrode current collector; and a negative electrode layer located on the solid electrolyte layer and having the same area as the solid electrolyte layer.

2. 2. The all-solid-state battery according to claim 1, wherein the area of ​​the solid electrolyte layer is 1.3 to 1.8 times larger than the area of ​​the positive electrode active material layer.

3. the negative electrode layer includes: a negative electrode current collector; and a negative electrode active material layer formed on the negative electrode current collector; The all-solid-state battery according to claim 1 , wherein the negative electrode active material layer is laminated so as to be in contact with the solid electrolyte layer.

4. The negative electrode layer includes a negative electrode current collector and a negative electrode-less coating layer formed on the negative electrode current collector, 2. The all-solid-state battery according to claim 1, wherein the anode-less coating layer is laminated so as to be in contact with the solid electrolyte layer.

5. The all-solid-state battery according to claim 1 , wherein two or more unit cells are stacked.

6. The all-solid-state battery according to claim 1 , wherein the all-solid-state battery is a pouch type.

7. (S1) forming a positive electrode active material layer having a certain area on a positive electrode current collector; (S2) forming a solid electrolyte layer on the positive electrode active material layer so as to surround one surface of the positive electrode active material layer and a side surface adjacent to the one surface; (S3) forming an anode layer on the solid electrolyte layer, the anode layer having the same area as the solid electrolyte layer; (S4) applying pressure in a stacking direction to bond the positive electrode current collector, the positive electrode active material layer, the solid electrolyte layer, and the negative electrode layer.

8. The method for producing an all-solid-state battery according to claim 7, wherein the pressure is 300 MPa to 700 MPa.

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