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

Abstract

The present invention relates to an all-solid-state battery having a unit cell electrode with low surface resistance, and a method for producing the same.

Description

[Technical Field]

[0001] This application claims priority rights under Korean Patent Application No. 10-2022-0139084 dated October 26, 2022, and Korean Patent Application No. 10-2023-0139649 dated October 18, 2023, and incorporates all the contents disclosed in the documents of said Korean patent applications as part of this specification.

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

[0003] A secondary battery is a device that stores external electrical energy in the form of chemical energy and generates electricity when needed. It is also called a rechargeable battery because it can be recharged multiple times. Commonly used secondary batteries include lead-acid batteries, nickel-cadmium batteries (NiCd), nickel-metal hydride batteries (NiMH), and lithium-ion batteries. Secondary batteries offer both economic and environmental advantages compared to disposable primary batteries.

[0004] Meanwhile, with the advancement of wireless communication technology, there is a demand for lighter, thinner, and smaller portable devices and automotive accessories, and the demand for rechargeable batteries used as energy sources for these devices is increasing. In particular, from the perspective of preventing environmental pollution, hybrid and electric vehicles have become practical, and research is emerging to reduce manufacturing costs and weight and extend lifespan by using rechargeable batteries in these next-generation automotive batteries. Among the various types of rechargeable batteries, lithium-ion batteries, which are lightweight, exhibit high energy density and operating potential, and have a long cycle life, have recently been attracting attention.

[0005] Generally, lithium secondary batteries are manufactured by mounting an electrode stack, consisting of a negative electrode, a positive electrode, and a separator membrane, inside a cylindrical or rectangular metal can or a pouch-shaped case made of aluminum laminate sheet, and then injecting an electrolyte into the electrode stack.

[0006] Conventionally, as an electrolyte for lithium secondary batteries, a liquid electrolyte in which a lithium salt is dissolved in a non-aqueous organic solvent has been mainly used. However, such a liquid electrolyte not only has a high possibility of deteriorating the electrode material and volatilizing the organic solvent, but also combustion, explosion, etc. may occur due to the ambient temperature and the temperature rise of the battery itself, and there is a risk of liquid leakage, which poses problems in realizing various forms of lithium secondary batteries with high safety.

[0007] On the other hand, all-solid-state batteries using solid electrolytes have the advantage that since they eliminate organic solvents, electrode laminates can be fabricated in a safe and simple form.

[0008] All-solid-state batteries are classified into oxide-based, polymer-based, and sulfide-based according to the raw materials of the solid electrolyte. Sulfide-based all-solid-state batteries have attracted attention because their lithium ion conductivity is superior to that of other series of batteries. However, despite their excellent characteristics, they have the disadvantage of being inferior in terms of lifespan and output compared to conventional batteries that utilize liquid electrolytes because their ion conductivity and the electric resistance between the positive and negative electrodes are higher than those of liquid batteries.

[0009] In order to improve the lifespan and output of a unit cell, methods such as changing the positive electrode, negative electrode, or type of solid electrolyte, or changing the assembly method can be considered.

[0010] In the case of sulfide-based all-solid-state batteries, when the electrodes and the solid electrolyte are fabricated by pressurizing in a roll-to-roll manner like a conventional lithium ion battery (LIB), a problem occurs in that the inside of the battery becomes porous and it becomes difficult to achieve interfacial contact. Therefore, it will be fabricated by a three-dimensional pressurization method using a hydrostatic pressure method. When pressurization is performed in such a hydrostatic pressure method, the size of the cell that can be pressurized is limited by the size of the chamber of isostatic pressurization equipment such as CIP and WIP, which may limit the scale-up of the production of all-solid-state batteries.

[0011] In addition, electrodes manufactured by applying an electrode active material onto a current collector by a method such as overcoating have a high surface resistance and may cause a performance degradation of an all-solid-state battery.

[0012] Therefore, there is a need for research on an all-solid-state battery and a method for manufacturing the same that can solve the above problems.

Prior Art Documents

Patent Documents

[0013]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0014] An object of the present invention is to reduce the surface resistance of a positive electrode and a negative electrode that are in contact with a solid electrolyte layer in a positive electrode and a negative electrode that constitute a unit cell, and to improve the performance of an all-solid-state battery.

[0015] Another object of the present invention is to provide a method for manufacturing an all-solid-state battery, in which the surface resistance of a positive electrode and a negative electrode that are in contact with a solid electrolyte layer is low, alignment between electrodes is easy, and the manufacturing method is simple.

Means for Solving the Problems

[0016] To achieve the above object, the present invention includes a first unit cell in which a current collector, a negative electrode, a solid electrolyte layer, and a positive electrode are laminated in this order; and a second unit cell in which a current collector, a positive electrode, a solid electrolyte layer, and a negative electrode are laminated in this order, wherein the first unit cell and the second unit cell are alternately laminated, and an all-solid-state battery in which electrodes of the same polarity are located on both surfaces of the current collector. In the first and second unit cells, the surface resistance of the negative electrode and positive electrode in contact with the solid electrolyte layer is 3 mΩ / cm². 2 The following all-solid-state battery is provided.

[0017] In one embodiment of the present invention, the solid electrolyte layer may contain a sulfide-based solid electrolyte.

[0018] In one embodiment of the present invention, the all-solid-state battery may have a current collector formed on the electrode located in the outermost layer.

[0019] In one embodiment of the present invention, in the first unit cell and the second unit cell, the surface resistance of the negative electrode in contact with the solid electrolyte layer and the positive electrode in contact with the solid electrolyte layer are 0.3 mΩ / cm 2 The following is also acceptable.

[0020] In one embodiment of the present invention, the total thickness of the current collector and the negative electrode combined may be 20 to 80 μm, and the total thickness of the current collector and the positive electrode combined may be 100 to 200 μm.

[0021] Furthermore, the present invention includes the steps of (1) manufacturing a negative electrode laminate by laminating a first release film, a negative electrode, and a second release film in that order; (2) A step of manufacturing a positive electrode laminate by laminating a first release film, a positive electrode, and a second release film in that order; (3) The step of peeling off the second release film from the negative electrode laminate and the second release film from the positive electrode laminate; (4) The step of interposing a solid electrolyte layer between the negative electrode laminated on the first release film and the positive electrode laminated on the first release film; (5) The steps of peeling off the first release film of the negative electrode and the first release film of the positive electrode, punching out to a certain size, and manufacturing a plurality of unit cells including the negative electrode, a solid electrolyte layer, and a positive electrode; (6) A current collector is interposed between one unit cell and another unit cell, with electrodes of the same polarity positioned on both sides of the current collector; (7) A method for manufacturing an all-solid-state battery is provided, which includes the step of stacking current collectors on electrodes located in the outermost layer.

[0022] In one embodiment of the present invention, the step of pressurizing the negative electrode laminate of step (1) and the step of pressurizing the positive electrode laminate of step (2) may be further included.

[0023] In one embodiment of the present invention, the thickness of the pressurized negative electrode laminate may be 50 to 90% of the thickness of the negative electrode laminate before pressurization, and the thickness of the pressurized positive electrode laminate may be 50 to 90% of the thickness of the positive electrode laminate before pressurization.

[0024] In one embodiment of the present invention, the solid electrolyte layer is (a) A step of manufacturing a solid electrolyte layer laminate by laminating a first release film, a solid electrolyte layer, and a second release film in that order; (b) The step of pressurizing the solid electrolyte layer laminate; (c) The pressurized solid electrolyte layer laminate is manufactured by the step of peeling off the first release film and the second release film.

[0025] In one embodiment of the present invention, the solid electrolyte layer may be manufactured by applying a solid electrolyte layer forming composition onto a positive electrode or a negative electrode.

[0026] In one embodiment of the present invention, the step of pressurizing after step (4) and before step (5) may be further included.

[0027] In one embodiment of the present invention, in step (5), the surface resistance of the negative electrode in contact with the solid electrolyte layer and the positive electrode in contact with the solid electrolyte layer is 3 mΩ / cm 2 The following is also acceptable.

[0028] In one embodiment of the present invention, in step (5), the surface resistance of the negative electrode in contact with the solid electrolyte layer and the positive electrode in contact with the solid electrolyte layer is 0.3 mΩ / cm 2 The following is also acceptable.

[0029] In one embodiment of the present invention, the total thickness of the current collector and the negative electrode combined may be 20 to 80 μm, and the total thickness of the current collector and the positive electrode combined may be 100 to 200 μm.

[0030] In one embodiment of the present invention, step (6) above may be repeated.

[0031] In one embodiment of the present invention, the solid electrolyte layer may contain a sulfide-based solid electrolyte. [Effects of the Invention]

[0032] The all-solid-state battery of the present invention has low surface resistance of both the positive electrode in contact with the solid electrolyte layer and the negative electrode in contact with the solid electrolyte layer, thus improving the performance of the all-solid-state battery.

[0033] Furthermore, the manufacturing method for all-solid-state batteries of the present invention, by manufacturing unit cells using a release film, enables the uniform production of the interfaces between the negative and positive electrodes contained in the unit cells, thereby reducing surface resistance. In addition, it has the advantage of a simple manufacturing process and easy alignment of the electrodes. [Brief explanation of the drawing]

[0034] [Figure 1] This figure shows the all-solid-state battery of the present invention. [Figure 2] This flowchart shows the method for manufacturing an all-solid-state battery according to the present invention. [Modes for carrying out the invention]

[0035] The present invention will be described in detail below, based on the attached drawings, so that it can be easily implemented by a person with ordinary skill in the art to which the invention pertains. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0036] To clearly explain the present invention, irrelevant parts have been omitted, and the same or similar reference numerals will be used throughout the specification for identical or similar constituent elements.

[0037] Furthermore, the terms and words used in this specification and the claims shall not be interpreted in a manner limited to their ordinary or lexicographical meanings, but rather in a manner 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.

[0038] The embodiments will be described in detail below with reference to the attached drawings. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0039] The present invention relates to a first unit cell (10) in which a current collector (11), a negative electrode (12), a solid electrolyte layer (13), and a positive electrode (14) are stacked in that order; and It includes a second unit cell (20) in which a current collector (21), a positive electrode (24), a solid electrolyte layer (23), and a negative electrode (22) are stacked in that order, A solid-state battery (100) in which the first unit cell (10) and the second unit cell (20) are stacked alternately, and electrodes of the same polarity are located on both sides of the current collector (11 or 21), In the first unit cell (10) and the second unit cell (20), the surface resistance of the negative electrode (12, 22) in contact with the solid electrolyte layer (13, 23) and the positive electrode (14, 24) in contact with the solid electrolyte layer (13, 23) is 3 mΩ / cm. 2 The following concerns all-solid-state batteries.

[0040] The first unit cell (10) is constructed by stacking a current collector (11), a negative electrode (12), a solid electrolyte layer (13), and a positive electrode (14) in that order.

[0041] The first unit cell (10) is formed by stacking a negative electrode (12) on a current collector (11), and the current collector may be a negative electrode current collector (11).

[0042] The negative electrode current collector (11) is for supporting the negative electrode active material and is not particularly limited as long as it has excellent conductivity and is electrochemically stable in the voltage range of the lithium secondary battery. For example, the negative electrode current collector (11) may be any one metal selected from the group consisting of copper, aluminum, stainless steel, titanium, silver, palladium, nickel, alloys thereof, and combinations thereof, and the stainless steel may be surface-treated with carbon, nickel, titanium, or silver, and as the alloy, aluminum-cadmium alloy may be preferably used, but other materials such as calcined carbon, non-conductive polymers surface-treated with conductive materials, or conductive polymers may also be used. Preferably, the negative electrode current collector (11) may be any one metal selected from the group consisting of stainless steel, copper, nickel, alloys thereof, and combinations thereof.

[0043] The negative electrode current collector (11) can have fine irregularities formed on its surface to strengthen its bonding force with the negative electrode active material, and may be used in various forms such as film, sheet, foil, mesh, net, porous material, foam, or nonwoven fabric.

[0044] The thickness of the negative electrode current collector (11) may be 5 to 20 μm.

[0045] The negative electrode (12) has the same meaning as the negative electrode active material, and the negative electrode active material may include one or more selected from a material that can reversibly insert and remove lithium ions, lithium metal, or a metallic material that can be alloyed with lithium, preferably including one or more selected from a carbon-based negative electrode active material and a metallic or quasi-metallic negative electrode active material.

[0046] The carbon-based anode active material may be amorphous carbon. Examples of amorphous carbon include carbon black, acetylene black, furnace black, Ketjen black, and graphene, but are not necessarily limited to these; any material classified as amorphous carbon in the art is acceptable. Amorphous carbon is carbon that does not have crystallinity or has very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon.

[0047] The aforementioned metallic or quasimetallic anode active material includes, but is not limited to, one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). Any metallic or quasimetallic anode active material that forms an alloy or compound with lithium in the art is acceptable. For example, nickel (Ni) does not form an alloy with lithium and is therefore not a metallic anode active material.

[0048] In one embodiment, the negative electrode active material may consist only of amorphous carbon, or it may consist of one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). In another embodiment, the negative electrode active material may consist of a mixture of amorphous carbon and one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The mixing ratio of the amorphous carbon and the mixture of gold, etc., is, for example, 10:1 to 1:2, 5:1 to 1:1, or 4:1 to 2:1 by weight, but is not necessarily limited to this range.

[0049] The solid electrolyte of the solid electrolyte layer (13) may preferably contain a sulfide-based solid electrolyte.

[0050] Examples of the sulfide-based solid electrolyte include Li2S-P2S5, Li2S-P2S5-LiX (X is a halogen element), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (m, n are positive numbers, Z is any one of Ge, Zn or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p, q are positive numbers, M is any one of P, Si, Ge, B, Al, Ga, In), Li 7-x PS 6-x Cl x (0 < x < 2), Li 7-x PS 6-x Br x (0 < x < 2) and Li 7-x PS 6-x I x It is one or more selected from the above.

[0051] The sulfide-based solid electrolyte may include, for example, an argyrodite type solid electrolyte represented by the following Chemical Formula 1: [Chemical Formula 1] Li + 12-n-x A n+ X 2- 6-x Y - x In the above formula, A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb or Ta, X is S, Se or Te, Y is Cl, Br, I, F, CN, OCN, SCN, or N3, 1 < n < 5, 0 < x < 2.

[0052] Furthermore, sulfide-based solid electrolytes include, for example, Li 7-x PS 6-x Cl x (0≦x≦2), Li 7-x PS 6-x Br x (0≦x≦2) and Li 7-x PS 6-x I x The compound may be an argyrodite type containing one or more elements selected from (0 ≤ x ≤ 2). Preferably, the sulfide-based solid electrolyte may be an argyrodite type compound containing one or more elements selected from, for example, Li6PS5Cl, Li6PS5Br, and Li6PS5I. Alternatively, the sulfide-based solid electrolyte may be, for example, Li6PS5Cl further doped with bromine (Br).

[0053] The positive electrode (14) includes a positive electrode active material and may selectively include a conductive material and a binder.

[0054] The positive electrode active material may vary depending on the type of all-solid-state battery. For example, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (0 ≤ x ≤ 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented as O2 (M=Co, Mn, Al, Cu, Fe, Mg, B or Ga; 0.01≦x≦0.3); chemical formula LiMn 2-x M x Lithium manganese composite oxide represented as O2 (M=Co, Ni, Fe, Cr, Zn, or Ta; 0.01≦x≦0.1) or Li2Mn3MO8 (M=Fe, Co, Ni, Cu, or Zn); LiNix Mn 2-x Lithium manganese composite oxide with a spinel structure represented by O4; LiCoPO4; LiFePO4; elemental sulfur (S8); Li2S n (n=1), organosulfur compounds or carbon-sulfur polymers ((C2S x ) n This may include, but is not limited to, sulfur-based compounds such as (x=2.5~50, n=2).

[0055] The conductive material electrically connects the electrolyte and the positive electrode active material, acting as a pathway for electrons to move from the current collector to the positive electrode active material. It can be used without limitation as long as it does not undergo chemical changes in a lithium secondary battery and is porous and conductive.

[0056] For example, the conductive material may 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 may be used individually or in combination.

[0057] Currently, commercially available conductive materials include acetylene black-based materials (such as those from Chevron Chemical Company and Gulf Oil Company), Ketjen Black EC-based materials (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.

[0058] Furthermore, the binder enhances the bonding force between the components constituting the positive electrode and between them and the current collector, and any binder known in the industry may be used.

[0059] 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.

[0060] The aforementioned second unit cell (20) is constructed by stacking a current collector (21), a positive electrode (24), a solid electrolyte layer (23), and a negative electrode (22) in that order.

[0061] The second unit cell (20) is formed by stacking positive electrodes (24) on a current collector (21), and the current collector may be a positive electrode current collector (21).

[0062] The positive electrode current collector (21) is the same as the negative electrode current collector (11) described above, and is preferably made of aluminum or an aluminum alloy. The thickness of the positive electrode current collector (21) may be 5 to 20 μm.

[0063] The positive electrode (24), solid electrolyte layer (23), and negative electrode (22) contained in the second unit cell (20) are identical to the positive electrode (14), solid electrolyte layer (13), and negative electrode (12) contained in the first unit cell (10) described above.

[0064] The all-solid-state battery of the present invention is configured such that the first unit cell (10) and the second unit cell (20) are stacked alternately, and in this case, electrodes of the same polarity may be located on both sides of the current collector (11 or 21).

[0065] In one embodiment, when a second unit cell (20) is stacked on a first unit cell (10), the positive electrode current collector (21) of the second unit cell (20) may be stacked on the positive electrode (14) of the first unit cell (10). Therefore, the positive electrode (14) of the first unit cell (10) and the positive electrode (24) of the second unit cell (20) may be located on both sides of the positive electrode current collector (21).

[0066] In another embodiment, when the first unit cell (10) is stacked on the second unit cell (20), the negative electrode current collector (11) of the first unit cell (10) may be stacked on the negative electrode (22) of the second unit cell (20). Therefore, the negative electrode (22) of the second unit cell (20) and the negative electrode (12) of the first unit cell (10) may be located on both sides of the negative electrode current collector (11).

[0067] When the first unit cell (10) and the second unit cell (20) are stacked alternately, the outermost layer of the all-solid-state battery (100) will have either a positive or negative electrode. Therefore, it may be preferable to stack a positive electrode current collector or a negative electrode current collector on the positive or negative electrode of the outermost layer, thereby forming a positive electrode current collector or a negative electrode current collector on the outermost layer of the all-solid-state battery (100).

[0068] In the all-solid-state battery (100) of the present invention, the interface in which the negative electrodes (12, 22) and positive electrodes (14, 24) contained in the first unit cell (10) and the second unit cell (20) contact the solid electrolyte layer (13, 23) is uniform, and can exhibit a low surface resistance, the surface resistance of which is 3 mΩ / cm. 2 Preferably, 1 mΩ / cm 2 More preferably, 0.5 mΩ / cm 2 Below, the most preferred value is 0.3 mΩ / cm 2 The following is also acceptable.

[0069] Therefore, the all-solid-state battery (100) of the present invention can exhibit excellent performance.

[0070] In this case, the total thickness of the current collector (11) and the negative electrodes (12, 22) combined may be 20 to 80 μm, preferably 30 to 70 μm. Also, the total thickness of the current collector (21) and the positive electrodes (14, 24) combined may be 100 to 200 μm, preferably 120 to 170 μm. Specifically, in the first unit cell (10), the total thickness of the current collector (11) and the negative electrode (12) combined may be 20 to 80 μm, preferably 30 to 70 μm. Also, in the second unit cell (20), the total thickness of the current collector (21) and the positive electrode (24) combined may be 100 to 200 μm, preferably 120 to 170 μm.

[0071] The uniform interface between the negative electrode (12, 22) in contact with the solid electrolyte layer (13, 23) and the positive electrode (14, 24) in contact with the solid electrolyte layer (13, 23) is due to the manufacturing method of the all-solid-state battery of the present invention, which will be described later.

[0072] Among conventional all-solid-state batteries, those using sulfide-based solid electrolytes had a problem: when manufactured using a roll-to-roll pressurization method, many pores (porous) formed inside the electrodes, making interfacial contact difficult. To solve this, a three-dimensional pressurization method was implemented through hydrostatic pressurization, but the size of the battery that could be pressurized was limited by the size of the chamber in the isotropic pressurization equipment.

[0073] Furthermore, manufacturing an all-solid-state battery requires repeating a complex process in which the negative electrode is laminated onto a solid electrolyte layer sheet, then pressurized, another solid electrolyte layer sheet is laminated onto this and pressurized, and then the positive electrode is laminated onto this and pressurized. Repeating this process makes it difficult to align the electrodes that are laminated.

[0074] Furthermore, in the case of positive and negative electrodes, the positive and negative electrodes are manufactured by overcoating the positive or negative electrode active material onto the current collector. However, in this case, the surfaces of the positive and negative electrodes are uneven, resulting in high surface resistance, which makes it impossible to manufacture all-solid-state batteries with superior performance.

[0075] Therefore, the present invention aims to provide a method for manufacturing an all-solid-state battery that can solve the aforementioned problems.

[0076] The present invention relates to a method for manufacturing an all-solid-state battery, (1) A step of manufacturing a negative electrode laminate (not shown) by laminating a first release film (35), a negative electrode (32), and a second release film (not shown) in that order; (2) A step of manufacturing a positive electrode laminate (not shown) by stacking a first release film (35), a positive electrode (34), and a second release film (not shown) in that order; (3) The step of peeling off the second release film from the negative electrode laminate and the second release film from the positive electrode laminate; (4) Interposing a solid electrolyte layer (33) between a negative electrode (32) laminated on the first release film (35) and a positive electrode (34) laminated on the first release film (35); (5) The steps of peeling off the first release film (35) of the negative electrode (32) and the first release film (35) of the positive electrode (34), punching them out to a certain size to manufacture a plurality of unit cells (30) including the negative electrode (32), solid electrolyte layer (33), and positive electrode (34); (6) A current collector (31) is interposed between one unit cell (30a) and another unit cell (30b), and electrodes of the same polarity are positioned on both sides of the current collector (31); (7) The step of stacking a current collector (31) on the electrode located in the outermost layer may also be included.

[0077] Step (1) is a step of manufacturing a negative electrode laminate by stacking a first release film (35), a negative electrode (32), and a second release film in that order, and step (2) is a step of manufacturing a positive electrode laminate by stacking a first release film (35), a positive electrode (34), and a second release film in that order.

[0078] The first release film (35) and the second release film may be the same or different, and are not particularly limited in type as long as they are used in the industry. For example, they may be one or more selected from the group consisting of polyethylene terephthalate (PET), polyimide (PI), poly(methylmethacrylate), PMMA, cellulose triacetate (TAC), polypropylene, polyethylene, and polycarbonate. Furthermore, the first release film (35) and the second release film may have a coating or surface treatment applied to one side on which the negative or positive electrode is laminated so that no residue remains when peeled off. Examples of such surface treatments include surface modification treatments such as plasma treatment and sulfonation treatment, or release treatments such as silicon treatment, long-chain alkyl treatment, and fluorine treatment.

[0079] The negative electrode laminate may be manufactured by applying or laminating a negative electrode active material to one side of the first release film (35) to produce a negative electrode (32) formed on the first release film (35), and then laminating a second release film on the negative electrode (32).

[0080] Alternatively, the positive electrode laminate may be manufactured by applying or laminating a positive electrode active material to one side of the first release film (35) to produce a positive electrode (34) formed on the first release film (35), and then laminating a second release film on the positive electrode (34).

[0081] The negative electrode active material and positive electrode active material are as described above.

[0082] In one embodiment, the negative electrode (32) may be formed on the first release film (35) by dissolving a negative electrode active material in a solvent to produce a slurry-like negative electrode forming composition, and then applying and drying the composition onto the first release film (35). Subsequently, a second release film may be laminated on the negative electrode (32).

[0083] In one embodiment, the positive electrode (34) may be formed by dissolving a positive electrode active material in a solvent to produce a slurry-like positive electrode forming composition, then applying and drying the composition onto a first release film (35) to form the positive electrode (34) on the first release film (35). Subsequently, a second release film may be laminated onto the positive electrode (34).

[0084] The positive electrode (34) may further include a conductive material, a binder, and a solid electrolyte in addition to the positive electrode active material, and the conductive material, binder, and solid electrolyte are as described above.

[0085] In the aforementioned negative electrode laminate, the negative electrode (32) is located between the first release film (35) and the second release film, so the surface of the negative electrode (32) in contact with the first release film (35) and the surface of the negative electrode (32) in contact with the second release film can be manufactured to be very uniform.

[0086] Furthermore, in the positive electrode laminate, since the positive electrode (34) is located between the first release film (35) and the second release film, the surface of the positive electrode (34) in contact with the first release film (35) and the surface of the positive electrode (34) in contact with the second release film can be manufactured to be very uniform.

[0087] The process may further include a step of pressurizing the negative electrode laminate manufactured in step (1) and the positive electrode laminate manufactured in step (2), wherein the pressurization may be performed at a temperature of 25 to 60°C and a pressure of 10 to 100 MPa for no more than 5 minutes.

[0088] By applying the aforementioned pressure, the surfaces of the negative electrode (32) in contact with the first release film (35) and the negative electrode (32) in contact with the second release film in the negative electrode laminate manufactured in step (1) can be manufactured more uniformly. Furthermore, the surfaces of the positive electrode (34) in contact with the first release film (35) and the positive electrode (34) in contact with the second release film in the positive electrode laminate manufactured in step (2) can be manufactured to be extremely uniform.

[0089] The thickness of the pressurized negative electrode laminate may be 50-90% of the thickness of the negative electrode laminate before pressurization, and the thickness of the pressurized positive electrode laminate may be 50-90% of the thickness of the positive electrode laminate before pressurization.

[0090] Step (3) above is a step of peeling off the second release film of the negative electrode laminate and the second release film of the positive electrode laminate, and the second release film may be peeled off in order to interpose a solid electrolyte layer (33) between the positive electrode (34) and the negative electrode (32).

[0091] Step (4) above is the step of interposing a solid electrolyte layer (33) between the negative electrode (32) laminated on the first release film (35) and the positive electrode (34) laminated on the first release film (35). More specifically, the solid electrolyte layer (33) may be interposed between one side of the negative electrode from which the second release film has been peeled off and one side of the positive electrode from which the second release film has been peeled off.

[0092] In one embodiment, the solid electrolyte layer (33) is (a) A step of manufacturing a solid electrolyte layer laminate by laminating a first release film (35), a solid electrolyte layer (33), and a second release film in that order; (b) The step of pressurizing the solid electrolyte layer laminate; (c) The first release film (35) and the second release film of the pressurized solid electrolyte layer laminate may be manufactured by:

[0093] The first release film (35) and the second release film are as described above.

[0094] Step (a) is a step of manufacturing a solid electrolyte layer laminate by stacking a first release film (35), a solid electrolyte layer (33), and a second release film in that order.

[0095] The solid electrolyte layer (33) may be formed by mixing solid electrolyte powder, a binder, and a solvent to produce a slurry-like solid electrolyte layer-forming composition, then applying and drying the composition onto a first release film (35) to form the solid electrolyte layer (33) on the first release film (35). Subsequently, a second release film may be laminated on the solid electrolyte layer (33).

[0096] The solid electrolyte may preferably include a sulfide-based solid electrolyte, as described above. Furthermore, the binder and solvent may be used without particular limitations, as long as they are materials that do not react with sulfur in the solid electrolyte.

[0097] Step (b) is a step of pressurizing the solid electrolyte layer laminate manufactured in step (a), and may be the same as the process of pressurizing the negative electrode laminate and the positive electrode laminate.

[0098] Step (c) is a step of peeling off the first release film (35) and the second release film of the pressurized solid electrolyte layer laminate, and by peeling off the first release film (35) and the second release film, the solid electrolyte layer (33) can be manufactured.

[0099] Therefore, the solid electrolyte layer (33) may be in the form of a film, and the film-like solid electrolyte layer (33) may be interposed between the negative electrode (32) laminated on the first release film (35) and the positive electrode (34) laminated on the first release film (35).

[0100] Furthermore, since the solid electrolyte layer (33) is manufactured using a release film, the surfaces on both sides of the solid electrolyte layer (33) can be manufactured to be very uniform.

[0101] In another embodiment, the solid electrolyte layer (33) may be manufactured by mixing solid electrolyte powder, a binder, and a solvent to produce a slurry-like solid electrolyte layer forming composition, then applying and drying the composition onto a first release film (35) to form a solid electrolyte layer (33) on the first release film (35), and finally peeling off the first release film (35).

[0102] In another embodiment, the solid electrolyte layer (33) may be manufactured by coating and drying a solid electrolyte layer forming composition onto the positive electrode (34) or the negative electrode (32).

[0103] For example, a solid electrolyte layer (33) may be manufactured by applying and drying a solid electrolyte layer forming composition onto a negative electrode (32) laminated on a first release film (35), and a positive electrode (34) laminated on the first release film (35) may be laminated on the solid electrolyte layer (33). In this case, the negative electrode (32) and the positive electrode (34) may be located on both sides of the solid electrolyte layer (33), respectively.

[0104] For example, a solid electrolyte layer (33) may be manufactured by applying and drying a solid electrolyte layer forming composition onto a positive electrode (34) laminated on a first release film (35), and then a negative electrode (32) laminated on the first release film (35) may be laminated onto the solid electrolyte layer (33). In this case, the negative electrode (32) and positive electrode (34) may be located on both sides of the solid electrolyte layer (33), respectively.

[0105] The (4) step may involve manufacturing a laminate in which the first release film (35) - negative electrode (32) - solid electrolyte layer (33) - positive electrode (34) - first release film (35) are stacked in that order.

[0106] The process may further include a pressurizing step after step (4) and before step (5). The pressurizing may be performed using high-temperature pressurization with CIP, WIP, or upper and lower plates. The pressurizing conditions are not particularly limited, and pressurizing conditions used for manufacturing all-solid-state batteries may be used. Preferably, pressurizing at 60 to 100°C and a pressure of 300 to 800 MPa for 10 to 60 minutes can be used to produce a solid electrolyte layer (33) with a thickness of 20 to 100 μm after pressurization. For example, pressurizing at 80°C and a pressure of 500 MPa for 30 minutes can produce a solid electrolyte layer (33) with a thickness of 50 μm after pressurization.

[0107] By applying the aforementioned pressure, the negative electrode (32) and positive electrode (34) adhere to the solid electrolyte layer (33), strengthening the bond and potentially facilitating the removal of the first release film (35) in step (5) described later.

[0108] Step (5) above is the step of peeling off the first release film (35) of the negative electrode (32) and the first release film (35) of the positive electrode (34), punching them out to a certain size, and manufacturing a plurality of unit cells (30) including the negative electrode (32), solid electrolyte layer (33), and positive electrode (34).

[0109] By manufacturing a unit cell (30) using the first release film (35) and the second release film, the surfaces of the negative electrode (32) in contact with the first release film (35), the negative electrode (32) in contact with the second release film, the positive electrode (34) in contact with the first release film (35), and the positive electrode (34) in contact with the second release film can be manufactured to be very uniform. That is, both sides of the negative electrode (32) and both sides of the positive electrode (34) can be manufactured to be very uniform. Therefore, the negative electrode (32) and positive electrode (34) contained in the unit cell (30) may have very low surface resistance.

[0110] The surface resistance of the positive electrode (34) in contact with the solid electrolyte layer (33) contained in the unit cell (30) and the negative electrode (32) in contact with the solid electrolyte layer (33) is 3 mΩ / cm 2 Preferably, 1 mΩ / cm2 More preferably, 0.5 mΩ / cm 2 Below, the most preferred value is 0.3 mΩ / cm 2 The following is also possible: If the unit cell (30) is manufactured by conventional methods such as overcoating without using the first release film (35) and the second release film, the surfaces of the negative electrode (32) and positive electrode (34) will be non-uniform and the surface resistance will be 5 mΩ / cm 2 Even if the surface resistance is higher than the stated value, in this case, it is not possible to manufacture an all-solid-state battery with superior performance due to the high surface resistance.

[0111] Step (6) above is a step of interposing a current collector (31) between one unit cell (30a) and another unit cell (30b), and the current collector (31) may have electrodes of the same polarity on both sides.

[0112] The thickness of the current collector is 5 to 20 μm, and the description of the current collector is as described above.

[0113] In one embodiment, the current collector (31) may be a negative electrode current collector (31a), and the negative electrode (32) of one unit cell (30a) and the negative electrode (32) of another unit cell (30b) may be located on both sides of the negative electrode current collector (31a). Furthermore, the total thickness, which is the sum of the thickness of the current collector (31) and the thickness of the negative electrode (32), may be 20 to 80 μm, preferably 30 to 70 μm.

[0114] In another embodiment, the current collector (31) may be a positive electrode current collector (31b), and the positive electrode (34) of one unit cell (30a) and the positive electrode (34) of another unit cell (30b) may be located on both sides of the positive electrode current collector (31b). Furthermore, the total thickness, including the thickness of the current collector (31) and the thickness of the positive electrode (34), may be 100 to 200 μm, preferably 120 to 170 μm.

[0115] The above step (6) may be repeated to manufacture a stack cell type all-solid-state battery (100) in which multiple unit cells (30) are stacked.

[0116] Step (7) is the step of stacking the current collector (31) on the electrode located in the outermost layer. The two electrodes located in the outermost layer may have the same or different polarities.

[0117] When the all-solid-state battery (100) manufactured in step (7) is placed in a jig and the charging and discharging of the all-solid-state battery (100) is activated, the driving voltage causes electrical contact between the current collector (31) and the positive electrode (34) or negative electrode (32) of the unit cell (30), and finally the all-solid-state battery (100) can be manufactured. Since the current collector (31) is difficult to detach, an all-solid-state battery (100) with excellent stability can be provided.

[0118] Furthermore, the present invention relates to an all-solid-state battery (100) manufactured by the manufacturing method of the present invention. In a unit cell (30) constituting the all-solid-state battery (100) of the present invention, the surface resistance of the positive electrode (34) in contact with the solid electrolyte layer (33) and the negative electrode (32) in contact with the solid electrolyte layer (33) is 3 mΩ / cm 2 Preferably, 1 mΩ / cm 2 More preferably, 0.5 mΩ / cm 2 Below, the most preferred value is 0.3 mΩ / cm 2 The following is also possible: Because the surface resistance of the positive electrode (34) and the negative electrode (32) is very low, the all-solid-state battery (100) of the present invention can exhibit excellent performance.

[0119] The following are preferred embodiments to aid in understanding the present invention. These embodiments are illustrative of the present invention, and it will be apparent 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 that these variations and modifications fall within the scope of the appended claims.

[0120] <Manufacturing of all-solid-state batteries> Example 1. As the first and second release films, silicone-coated polyethylene terephthalate was used.

[0121] A slurry-like negative electrode-forming composition, containing nano-sized silver (Ag) powder and amorphous carbon, was applied to one side of the first release film and dried to form a negative electrode on the first release film. Subsequently, a second release film was laminated on the negative electrode to produce a negative electrode laminate.

[0122] A cathode active material (NCM811 coated with LiNbO3), a conductive material (amorphous carbon), a binder (SBR-based), and a solid electrolyte (Li6PS5Cl) were mixed in a ratio of 70:5:5:20 and added to a solvent to produce a slurry-like cathode-forming composition. This composition was applied to one side of a first release film and dried at 100°C for 6 hours to form a cathode on the first release film. Subsequently, a second release film was laminated on the cathode to produce a cathode laminate.

[0123] Li6PS5Cl was used as the solid electrolyte, and it was added to a solvent to produce a slurry-like composition for forming a solid electrolyte layer. This composition was then applied to one side of a first release film and dried to form a solid electrolyte layer on the first release film. Subsequently, a second release film was laminated on the solid electrolyte layer to produce a solid electrolyte layer laminate.

[0124] The negative electrode laminate, positive electrode laminate, and solid electrolyte layer laminate were each pressurized at a temperature of 25 to 60°C under a pressure of 10 to 100 MPa for 5 minutes.

[0125] The second release film of the negative electrode laminate was peeled off, and the second release film of the positive electrode laminate was peeled off. In addition, the first and second release films of the solid electrolyte layer laminate were peeled off to obtain the solid electrolyte layer.

[0126] A solid electrolyte layer was interposed between the negative electrode and the positive electrode, and this was pressurized to 500 MPa. Subsequently, the first release films located on one side of the positive electrode and the negative electrode were peeled off, and the cells were punched out to a size of 20 x 20 cm to produce multiple unit cells containing the positive electrode / solid electrolyte layer / negative electrode.

[0127] A 10 μm thick aluminum positive electrode current collector was interposed between the positive electrode of one unit cell and the positive electrode of another unit cell. Then, a 10 μm thick stainless steel negative electrode current collector was laminated onto the negative electrode, and another unit cell was laminated on top of it, so that the negative electrode of the unit cell was formed on the negative electrode current collector. The above process was repeated to stack the unit cells so that the negative electrode was formed on the outermost layer. After this, the negative electrode current collector was laminated on the outermost layer to manufacture an all-solid-state battery.

[0128] The aforementioned all-solid-state battery was placed in a jig, and a drive pressure of 10 MPa was applied to ultimately manufacture the all-solid-state battery.

[0129] Comparative Example 1. The negative electrode was manufactured by coating a 10 μm thick SUS (stainless steel) negative electrode current collector with a slurry-like negative electrode formation composition containing nano-sized silver (Ag) powder and amorphous carbon, to a thickness of 150 μm.

[0130] A cathode active material (NCM811 coated with LiNbO3), a conductive material (amorphous carbon), a binder (SBR-based), and a solid electrolyte (Li6PS5Cl) were mixed in a ratio of 70:5:5:20 and added to a solvent to produce a slurry-like cathode forming composition. This composition was then applied to one side of a 10 μm thick aluminum current collector, dried at 100°C for 6 hours, and then rolled to form the cathode.

[0131] A unit cell was manufactured by overcoating the positive electrode surface with a solid electrolyte (Li6PS5Cl) and pressurizing it at 500 MPa, stacking the positive electrode and the solid electrolyte layer, then stacking the negative electrode (one side not in contact with the negative electrode current collector) on the solid electrolyte layer and pressurizing it at 500 MPa. Multiple unit cells were manufactured by repeating the above process, and an all-solid-state battery was manufactured by stacking the unit cells with electrodes of the same polarity positioned between the current collectors.

[0132] The aforementioned all-solid-state battery was placed in a jig, and a drive pressure of 10 MPa was applied to ultimately manufacture the all-solid-state battery.

[0133] Experimental Example 1. Measurement of surface resistance of a unit cell electrode The surface resistance of the negative electrode constituting the unit cell manufactured in Example 1 and Comparative Example 1 was measured.

[0134] The aforementioned surface resistance was measured using a HIOKI RM2610 system.

[0135] As a result, the surface resistance of the negative electrode of the unit cell in Example 1 was 0.2132 mΩ / cm². 2 Therefore, the surface resistance of the negative electrode of the unit cell in Comparative Example 1 is 7.4283 mΩ / cm². 2 That was the case.

[0136] In other words, the surface resistance of the negative electrode of the unit cell in Example 1 was approximately 35 times lower than that of the negative electrode in Comparative Example 1. This is a result of manufacturing the negative electrode using a release film, which allows for the uniform production of the negative electrode surface, thus resulting in low surface resistance. On the other hand, the negative electrode of the unit cell in Comparative Example 1 is manufactured by overcoating the negative electrode active material onto the negative electrode current collector, making it difficult to produce a uniform surface, thus resulting in high surface resistance.

[0137] Since the lower the surface resistance, the better the performance of the all-solid-state battery; therefore, it can be predicted that the all-solid-state battery of the present invention will have superior performance.

[0138] Furthermore, since the positive electrode is manufactured using the same method as the negative electrode, it can be predicted that the positive electrode will also have low surface resistance. [Explanation of Symbols]

[0139] 100: All-solid-state battery; 30, 30a, 30b: Unit cell 10: First unit cell 20: Second unit cell 11, 21, 31: Current collectors; 31a: Negative electrode current collector 31b: Positive electrode current collector 12,22,32: Negative electrode 13,23,33: Solid electrolyte layer 14,24,34: Positive electrode 35: First release film

Claims

1. A first unit cell in which a current collector, a negative electrode, a solid electrolyte layer, and a positive electrode are stacked in that order; and It includes a second unit cell in which a current collector, a positive electrode, a solid electrolyte layer, and a negative electrode are stacked in that order. An all-solid-state battery in which the first unit cell and the second unit cell are stacked alternately, and electrodes of the same polarity are located on both sides of the current collector, In the first and second unit cells, the interfacial resistance between the solid electrolyte layer and the negative electrode in contact with it, and the interfacial resistance between the solid electrolyte layer and the positive electrode in contact with it, are 0.3 mΩ·cm² or less, in an all-solid-state battery.

2. The all-solid-state battery according to claim 1, wherein the solid electrolyte layer includes a sulfide-based solid electrolyte.

3. The all-solid-state battery according to claim 1, wherein a current collector is formed on the electrode located in the outermost layer.

4. The total thickness, including the thickness of the current collector and the thickness of the negative electrode, is 20 to 80 μm. The all-solid-state battery according to claim 1, wherein the total thickness of the current collector and the positive electrode combined is 100 to 200 μm.

5. (1) A step of manufacturing a negative electrode laminate by laminating a first release film, a negative electrode, and a second release film in that order; (2) A step of manufacturing a positive electrode laminate by stacking a first release film, a positive electrode, and a second release film in that order; (3) The step of peeling off the second release film from the negative electrode laminate and the second release film from the positive electrode laminate; (4) Interposing a solid electrolyte layer between the negative electrode laminated on the first release film and the positive electrode laminated on the first release film; (5) The steps of peeling off the first release film of the negative electrode and the first release film of the positive electrode, punching out to a certain size, and manufacturing a plurality of unit cells including the negative electrode, a solid electrolyte layer, and a positive electrode; (6) The step of interposing a current collector between one unit cell and another unit cell, wherein electrodes of the same polarity are positioned on both sides of the current collector; (7) A method for manufacturing an all-solid-state battery according to claim 1, comprising the step of stacking a current collector on the electrode located in the outermost layer.

6. A method for manufacturing an all-solid-state battery according to claim 5, further comprising the step of pressurizing the negative electrode stack in step (1) and the step of pressurizing the positive electrode stack in step (2).

7. The thickness of the pressurized negative electrode laminate is 50 to 90% of the thickness of the negative electrode laminate before pressurization. The method for manufacturing an all-solid-state battery according to claim 6, wherein the thickness of the pressurized positive electrode stack is 50 to 90% of the thickness of the positive electrode stack before pressurization.

8. The solid electrolyte layer is (a) A step of manufacturing a solid electrolyte layer laminate by laminating a first release film, a solid electrolyte layer, and a second release film in that order; (b) The step of pressurizing the solid electrolyte layer laminate; (c) a step of peeling off a first release film and a second release film from the pressurized solid electrolyte layer laminate; a method for manufacturing an all-solid-state battery according to claim 5.

9. The method for manufacturing an all-solid-state battery according to claim 5, wherein the solid electrolyte layer is manufactured by applying a solid electrolyte layer forming composition onto a positive electrode or a negative electrode.

10. A method for manufacturing an all-solid-state battery according to claim 5, further comprising the step of pressurizing after step (4) and before step (5).

11. In step (5) above, the interfacial resistance between the solid electrolyte layer and the negative electrode in contact with it, and the interfacial resistance between the solid electrolyte layer and the positive electrode in contact with it are 3 mΩ·cm. ２ The method for manufacturing an all-solid-state battery according to claim 5 is as follows:

12. In step (5) above, the interfacial resistance between the solid electrolyte layer and the negative electrode in contact with it, and the interfacial resistance between the solid electrolyte layer and the positive electrode in contact with it, are 0.3 mΩ·cm. ２ The method for manufacturing an all-solid-state battery according to claim 11 is as follows:

13. The total thickness, including the thickness of the current collector and the thickness of the negative electrode, is 20 to 80 μm. The method for manufacturing an all-solid-state battery according to claim 5, wherein the total thickness of the current collector and the positive electrode combined is 100 to 200 μm.

14. A method for manufacturing an all-solid-state battery according to claim 5, wherein the above step (6) is repeated.

15. The method for manufacturing an all-solid-state battery according to claim 5, wherein the solid electrolyte layer includes a sulfide-based solid electrolyte.

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