All-solid-state secondary battery, stacked all-solid-state secondary battery, and method for manufacturing same

Abstract

Provided are an all-solid-state secondary battery and a method for manufacturing same. The all-solid secondary battery includes a positive electrode layer, solid electrolyte layers respectively provided on both sides of the positive electrode layer, negative electrode layers respectively provided on a surface of each of the solid electrolyte layers which is opposite to the surface facing the positive electrode layer, an insulating member arranged to cover the side surface of the positive electrode layer, a sheet-shaped first conductive member protruding externally from the positive electrode layer while passing through the insulating member, and a sheet-shaped second conductive member protruding externally from the negative electrode layer, wherein the first conductive member is integrally formed with the positive electrode layer, and the second conductive member is integrally formed with the negative electrode layer. The first conductive member and the second conductive member are insulated from each other, and the edges of the first conductive member and the edges of the second conductive member are provided outside the negative electrode layer.

Description

All-solid-state secondary battery, stacked all-solid-state secondary battery and method for manufacturing the same

[0001] The present invention relates to an all-solid-state secondary battery, a stacked all-solid-state secondary battery, and a method for manufacturing the same.

[0002] Compared to conventional lithium-ion batteries that use liquid electrolytes, all-solid-state rechargeable batteries have recently been attracting attention because they can improve energy density. One method to further enhance the energy density of all-solid-state rechargeable batteries is to stack multiple cells. As a result, the overall size of the rechargeable battery can be reduced.

[0003] For example, there is a method of obtaining a stacked all-solid-state secondary battery by pressing a pair of temporary cells equipped with a positive current collector having a rough surface (roughened).

[0004] However, as the energy density of all-solid-state secondary batteries increases, if a short circuit occurs inside the battery due to, for example, an external impact or penetration such as a nail, a large local current may flow, causing the all-solid-state secondary battery to heat up and ignite.

[0005] The present invention aims to solve the aforementioned problems by further improving the safety of all-solid-state secondary batteries and simplifying the manufacturing process of all-solid-state secondary batteries and stacked all-solid-state secondary batteries.

[0006] In other words, the all-solid-state secondary battery, the stacked all-solid-state secondary battery, and the method for manufacturing the same according to the present invention are as follows.

[0007] According to an embodiment of the present invention, an all-solid-state secondary battery is provided. The all-solid-state secondary battery comprises: a positive electrode layer; a solid electrolyte layer provided on each of the two sides of the positive electrode layer; a negative electrode layer provided on the side facing the positive electrode layer and the side opposite to the solid electrolyte layer; an insulating member disposed to cover the side of the positive electrode layer; a thin first conductive member protruding outwardly from the positive electrode layer through the insulating member; and a thin second conductive member protruding outwardly from the negative electrode layer, wherein the first conductive member is formed integrally with the positive electrode layer and the second conductive member is formed integrally with the negative electrode layer, the first conductive member and the second conductive member are insulated from each other, and the edges of the first conductive member and the edges of the second conductive member may be provided on the outer side of the negative electrode layer.

[0008] The above-described all-solid-state secondary battery further includes a thin first current collector protruding outwardly from the positive electrode layer through the insulating member, and the first conductive member and the first current collector may protrude in different directions.

[0009] The above-described all-solid-state secondary battery further includes a thin second current collector protruding outward from the negative electrode layer, and the second conductive member and the second current collector may protrude in different directions.

[0010] The above-described all-solid-state secondary battery further comprises a thin first current collector protruding outwardly from the positive electrode layer through the insulating member; and a thin second current collector protruding outwardly from the negative electrode layer, wherein the first current collector and the second current collector may protrude in different directions.

[0011] A harmonizing member may be provided on at least a portion of the side of the above insulating member.

[0012] The above insulating member may contain resin.

[0013] The above insulating member may contain an insulating filler.

[0014] The insulating filler may include one or more materials selected from the group consisting of fibrous resin, resin nonwoven fabric, aluminum oxide, magnesium oxide, silica, boehmite, barium titanate, barium carbonate, yttria, and manganese oxide.

[0015] The first current collector extends outward from one end of the anode layer, and when viewed in the stacking direction, part or all of the outer edge of the insulating member on the side where the first current collector is placed may be provided outward from the outer edge of the cathode layer.

[0016] The above solid electrolyte layer may include a sulfide-based solid electrolyte containing lithium, phosphorus, and sulfur.

[0017] The above-mentioned negative electrode layer comprises one or more of a negative electrode active material that forms an alloy with lithium and a negative electrode active material that forms a compound with lithium, and metallic lithium may be precipitated inside the negative electrode layer during charging.

[0018] More than 80% of the charge capacity of the above-mentioned cathode layer can be exerted by the above-mentioned metallic lithium.

[0019] The above cathode layer may include one or more selected from the group consisting of amorphous carbon, gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, and zinc.

[0020] According to one embodiment of the present invention, a stacked all-solid-state secondary battery is provided in which two or more of the aforementioned all-solid-state secondary batteries are stacked.

[0021] According to one embodiment of the present invention, a method for manufacturing a stacked all-solid-state secondary battery is provided. The stacked all-solid-state secondary battery comprises a positive electrode layer, a solid electrolyte layer provided on each side of the positive electrode layer, a negative electrode layer provided on each side of the solid electrolyte layer facing the positive electrode layer and a negative electrode layer opposite to it, an insulating member disposed to cover the side of the positive electrode layer, a thin first conductive member protruding outwardly from the positive electrode layer through the insulating member, and a thin second conductive member protruding outwardly from the negative electrode layer, wherein the first conductive member may be formed integrally with the positive electrode layer and the second conductive member may be formed integrally with the negative electrode layer. The manufacturing method comprises a step of preparing the stacked battery by folding the first conductive member and the second conductive member, wherein the first conductive member and the second conductive member are insulated from each other, and the edge portion of the first conductive member and the edge portion of the second conductive member are provided on the outside of the negative electrode layer; And it may include a pressurizing process for pressing the laminate in its stacking direction.

[0022] The laminate further comprises: a thin first current collector protruding outward from the anode layer; and a first current collector protection member that protects the first current collector, and may further include a removal process for removing the first current collector protection member after the pressurization process.

[0023] The first current collection member protection part can be integrally formed on the side of the insulating member.

[0024] The above manufacturing method may further include a process of forming a notch between the insulating member and the first current collector protection part to facilitate the removal of the first current collector protection part.

[0025] The above notch may be formed in a range of 5% to 99% of the thickness of the first current collection protection part.

[0026] According to the present invention, an all-solid-state secondary battery comprises a first conductive member formed integrally with (i.e., electrically connected to) a positive electrode layer, and a second conductive member formed integrally with (i.e. electrically connected to) a negative electrode layer. Since the first conductive member and the second conductive member are disposed on the outer side of the negative electrode layer, current can flow in a dispersed manner even when a short circuit occurs in the all-solid-state secondary battery. As a result, heat generation in the all-solid-state secondary battery caused by a local increase in current is suppressed, thereby improving the safety of the all-solid-state secondary battery compared to conventional batteries.

[0027] In addition, since the first conductive member and the second conductive member are formed integrally with the positive and negative layers, respectively, the manufacturing process of the all-solid-state secondary battery can be simplified by adding only a folding process for the first conductive member and the second conductive member to the conventional manufacturing process of the all-solid-state secondary battery.

[0028] FIG. 1 is a cross-sectional view showing the schematic configuration of an all-solid-state secondary battery according to one embodiment of the present invention.

[0029] FIG. 2 is a plan view showing the schematic configuration of an all-solid-state secondary battery according to one embodiment of the present invention.

[0030] FIG. 3 is a cross-sectional view showing the schematic configuration of an all-solid-state secondary battery according to one embodiment of the present invention.

[0031] FIGS. 4A and FIGS. 4B are schematic diagrams illustrating a method for manufacturing an all-solid-state secondary battery according to one embodiment of the present invention.

[0032] Figure 5 is a plan view of the laminate of Figure 4B viewed from the stacking direction.

[0033] FIGS. 6A and 6B are schematic diagrams showing the structure of excess insulating material used in an all-solid-state secondary battery according to one embodiment of the present invention, where FIG. 6A is a plan view seen in the stacking direction and FIG. 6B is a cross-sectional view cut along the CC line.

[0034] FIG. 7 is a schematic diagram showing a method for manufacturing an all-solid-state secondary battery according to one embodiment of the present invention.

[0035] FIG. 8 is a schematic diagram showing a method for manufacturing an all-solid-state secondary battery according to one embodiment of the present invention.

[0036] FIG. 9 is a schematic diagram showing a method for manufacturing an all-solid-state secondary battery according to one embodiment of the present invention.

[0037] FIG. 10 is a cross-sectional view showing the schematic configuration of a stacked all-solid-state secondary battery according to one embodiment of the present invention.

[0038] FIG. 11 is a cross-sectional view showing the schematic configuration of an all-solid-state secondary battery according to another embodiment of the present invention.

[0039] FIG. 12 is a graph showing the evaluation results of an all-solid-state secondary battery according to an embodiment of the present invention.

[0040] FIG. 13 is a graph showing the evaluation results of an all-solid-state secondary battery according to a comparative example of the present invention.

[0041] FIG. 14 is a graph showing the evaluation results of an all-solid-state secondary battery according to a comparative example of the present invention.

[0042] The optimal embodiment of the present invention will be described in detail below with reference to the attached drawings.

[0043] Meanwhile, in this specification and drawings, components having substantially the same functional configuration are given the same reference numerals and redundant descriptions are omitted.

[0044] Additionally, to facilitate explanation, each component of the drawing is appropriately enlarged or reduced, and the size and proportions of each component of the drawing may differ from the actual size.

[0045] <1. Basic configuration of an all-solid-state secondary battery according to the present invention>

[0046] Referring to FIG. 1, the all-solid-state secondary battery (1) according to the present invention may include, for example, a positive electrode layer (10), a negative electrode layer (20), and a solid electrolyte layer (30). More specifically, the all-solid-state secondary battery (1) is an all-solid-state lithium secondary battery comprising a positive electrode layer (10), a solid electrolyte layer (30) provided on each side of the positive electrode layer (10), a negative electrode layer (20) provided on each side of the solid electrolyte layer (30) facing the positive electrode layer (10) and on the opposite side, and an insulating member (13) disposed on a side (S) of the positive electrode layer (10). Meanwhile, the side refers to an edge end that is not in the stacking direction and means an end in a direction perpendicular to the stacking direction.

[0047] (1-1. Anode layer)

[0048] Referring to FIG. 1, the positive layer (10) may include a positive current collector (11) and a positive active material layer (12). The positive current collector (11) may be, for example, stainless steel, titanium, nickel, aluminum, or an alloy thereof. The positive current collector (11) may be plate-shaped or foil-shaped. The thickness of the positive current collector (11) may be, for example, 1 μm or more and 50 μm or less, more preferably 5 μm or more and 30 μm or less.

[0049] Referring to FIG. 1, the positive active material layer (12) is disposed on both sides of the positive current collector (11). The positive active material layer (12) may include a positive active material and a solid electrolyte.

[0050] The solid electrolyte of the positive active material layer (12) may be the same as the solid electrolyte of the solid electrolyte layer (30), but is not limited thereto. Details of the solid electrolyte will be explained in the section on the solid electrolyte layer (30) described later.

[0051] The positive electrode active material can reversibly absorb and release lithium ions.

[0052] The positive electrode active material may be formed from a lithium salt comprising, for example, lithium cobaltate (hereinafter referred to as LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium cobalt aluminum oxide (hereinafter referred to as NCA), lithium cobalt manganese oxide (hereinafter referred to as NCM), lithium manganate, and / or lithium iron phosphate. Furthermore, the positive electrode active material may be formed from nickel sulfide, copper sulfide, sulfur, iron oxide, or vanadium oxide. Each of these positive electrode active materials may be used individually or may be formed in a combination of two or more.

[0053] The positive electrode active material preferably contains a lithium salt of a transition metal oxide having a layered rock salt structure. Here, "layered" means having a thin sheet shape. "Rock salt structure" refers to a sodium chloride type structure, which is a type of crystal structure, and specifically, means a structure in which face-centered cubic lattice formed by each of the cations and anions is offset from each other by half the ridge of the unit cell.

[0054] Lithium salts of transition metal oxides having such a layered rock salt structure are, for example, LiNi x Co y Al z O2(NCA) or LiNi x Co y Mn z O2(NCM) (where 0 <x <1, 0 <y <1, 0 <z <1, 그리고 x+y+z=1)과 같은 삼원계 전이 금속산화물의 리튬염을 포함할 수 있다.

[0055] When the positive electrode active material contains a lithium salt of a ternary transition metal oxide having the above-mentioned layered rock salt structure, the energy density and thermal stability of the all-solid-state secondary battery can be improved.

[0056] The positive electrode active material may be covered by a coating layer. The coating layer of this embodiment may be any known coating layer for the positive electrode active material of an all-solid-state secondary battery. The coating layer may be, for example, Li2-ZrO2.

[0057] Furthermore, when the positive electrode active material is formed from a lithium salt of a ternary transition metal oxide such as NCA or NCM and contains nickel, the capacity density of the all-solid-state secondary battery is increased, and metal leaching into the positive electrode active material in the charged state can be reduced. Accordingly, the long-term reliability and cycle characteristics of the all-solid-state secondary battery according to the present embodiment in the charged state can be improved.

[0058] Here, the positive active material may have a particle shape such as a true spherical shape or an elliptical spherical shape. The particle size of the positive active material is not particularly limited and may be within a range applicable to the positive active material of a conventional all-solid-state secondary battery. Meanwhile, the content of the positive active material in the positive layer (10) is not particularly limited and may be within a range applicable to the positive layer (10) of a conventional all-solid-state secondary battery (1).

[0059] In addition, in addition to the aforementioned positive active material and solid electrolyte, the positive composite material layer (12) may additionally suitably incorporate additives such as, for example, a positive layer conductor, a binder, a filler, a dispersant, or an ion conductor.

[0060] The anode layer conductive aid may be, for example, graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanotube, graphene, or metal powder. The binder may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, or polyethylene. The fillers, dispersants, and ion conductive aids that can be incorporated into the anode composite layer may be known materials that can generally be used in electrodes of all-solid-state secondary batteries.

[0061] The thickness of the positive active material layer (12) in the completed battery state is not particularly limited, but, for example, preferably 20 μm or more and 1000 μm or less, more preferably 50 μm or more and 500 μm or less, and particularly preferably 100 μm or more and 300 μm or less.

[0062] (1-2. Cathode layer)

[0063] Referring to FIG. 1, the negative electrode layer (20) may include, for example, a plate-shaped or thin negative electrode current collector (21) and a negative electrode active material layer (22) provided on the negative electrode current collector (21). If the first conductive member and the second conductive member described later are not further laminated on the outside, the negative electrode current collector (21) may form the outermost layer of the all-solid-state secondary battery (1).

[0064] It is preferable that the negative current collector (21) be formed of a material that does not react with lithium (i.e., does not form both an alloy and a compound). The negative current collector (21) may be any one selected from metals including, for example, stainless steel, copper, titanium, iron, cobalt, and nickel. Furthermore, the negative current collector (21) may be an alloy or clad material of two or more metals selected from these metals. Additionally, the negative current collector (21) may be a base metal in which another metal is plated or coated.

[0065] The thickness of the negative current collector (21) can be, for example, 1 μm or more and 50 μm or less, more preferably 5 μm or more and 30 μm or less.

[0066] The negative electrode active material layer (22) may include, for example, at least one of a negative electrode active material that forms an alloy with lithium and a negative electrode active material that forms a compound with lithium. And, as described below, by the negative electrode active material layer (22) including such a negative electrode active material, metallic lithium can be deposited on the surface of one or both sides of the negative electrode active material layer (22).

[0067] The cathode active material may be, for example, amorphous carbon, gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, antimony, or zinc.

[0068] Amorphous carbon can be, for example, carbon black or graphene. Carbon black can be acetylene black, furnace black, or ketjen black.

[0069] The shape of the negative electrode active material may be granular or a uniform layer such as a plating layer, but is not particularly limited thereto.

[0070] In the former case, lithium ions or lithium may pass through the interior of the granular negative electrode active material or through the gaps between the negative electrode active materials, so that a metal layer formed mainly of lithium may be formed between the negative electrode active material layer (22) and the negative electrode current collector (21). Some of the lithium may form an alloy with metal elements within the negative electrode active material and exist within the negative electrode active material layer (22).

[0071] Meanwhile, in the latter case, a metal layer may be deposited between the negative active material layer (22) and the solid electrolyte layer (30).

[0072] When the negative electrode active material layer (22) contains amorphous carbon, the negative electrode active material layer (22) has a specific surface area of ​​100 m² as measured by the nitrogen gas adsorption method. 2 Amorphous carbon having a low surface area of ​​1 / g or less, and a specific surface area of ​​300 m² measured by nitrogen gas adsorption method 2 It may be desirable to include a mixture of amorphous carbon having a high surface area of ​​1 / g or more.

[0073] The negative active material layer (22) may include one or more of the aforementioned negative active materials. For example, the negative active material layer (22) may include not only amorphous carbon but also one or more metals selected from the group consisting of gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, antimony, and zinc. Additionally, the negative active material layer (22) may include a mixture of one or more selected from the group consisting of gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, antimony, and zinc and amorphous carbon.

[0074] It is preferable that the mixing ratio (mass ratio) of the mixture of amorphous carbon and the aforementioned metal be 1:1 to 1:3. Accordingly, the characteristics of the all-solid-state secondary battery (1) can be further improved.

[0075] When the negative electrode active material includes one or more selected from the group consisting of gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, antimony, and zinc together with amorphous carbon, it is preferable that the particle size of such negative electrode active material be 4 μm or less. In this case, the characteristics of the all-solid-state secondary battery (1) can be further improved.

[0076] Additionally, if the negative electrode active material is a material capable of forming an alloy with lithium (e.g., one or more metals selected from the group consisting of gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, antimony, and zinc), the negative electrode active material layer (22) may be a layer formed of such metal. For example, the metal layer may be a plating layer.

[0077] If necessary, the negative electrode active material layer (22) may further include a binder. The binder may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, or polyethylene. The binder may include at least one of these. By including such a binder in the negative electrode active material layer (22), the detachment of the negative electrode active material can be suppressed, particularly when the negative electrode active material is in granular form. The content of the binder may be, for example, 0.3 mass% or more and 20.0 mass% or less, preferably 1.0 mass% or more and 15.0 mass% or less, and more preferably 3.0 mass% or more and 15.0 mass% or less, with respect to the total mass of the negative electrode active material layer (22).

[0078] In addition, the negative electrode active material layer (22) may be appropriately mixed with additives used in conventional all-solid-state secondary batteries (1), such as fillers, dispersants, or ion conductors.

[0079] When the negative electrode active material is in granular form, the thickness of the negative electrode active material layer (22) in the completed battery state may be 1 μm or more and 30 μm or less, preferably 5 μm or more and 20 μm or less. However, it is not particularly limited thereto. Due to the thickness of the negative electrode active material layer (22), the above-described effect of the negative electrode active material layer (22) can be sufficiently obtained, the resistance value of the negative electrode active material layer (22) can be reduced, and the characteristics of the all-solid-state secondary battery (1) can be improved.

[0080] When the negative electrode active material forms a uniform layer, the thickness of the negative electrode active material layer (22) may be, for example, 1 nm or more and 100 nm or less. In this case, the upper limit of the thickness of the negative electrode active material layer (22) may preferably be 95 nm, more preferably 90 nm, and even more preferably 50 nm.

[0081] Meanwhile, the present invention is not limited to the aforementioned embodiments, and the negative electrode active material layer (22) may have any configuration that can be used as the negative electrode active material layer (22) of the all-solid-state secondary battery (1). For example, the negative electrode active material layer (22) may include the aforementioned negative electrode active material, solid electrolyte, and negative electrode layer conductive agent.

[0082] In this case, for example, the negative electrode active material may be a metal active material or a carbon active material. The metal active material may be, for example, a metal such as lithium, indium, aluminum, tin, and silicon, and an alloy thereof. In addition, the carbon active material may be, for example, artificial graphite, graphite carbon fiber, resin calcined carbon, pyrolytic vapor-grown carbon, coke, mesocarbon microbeads (MCMB), furfuryl alcohol resin calcined carbon, polyacene pitch-based carbon fiber, vapor-grown carbon fiber, natural graphite, or non-graphitizable carbon. Meanwhile, the negative electrode active material may be one or a combination of two or more of the aforementioned materials.

[0083] The cathode layer conductive agent and the solid electrolyte may be the same as the anode layer conductive agent and solid electrolyte included in the anode active material layer (12). Therefore, a description of the composition of these is omitted.

[0084] (1-3. Solid Electrolyte Layer)

[0085] As illustrated in FIG. 1, for example, a solid electrolyte layer (30) is formed between the anode layer (10) and the cathode layer (20) and may contain a solid electrolyte. Meanwhile, the Z direction refers to the stacking direction, and the X direction refers to a direction perpendicular to the stacking direction.

[0086] The thickness of the solid electrolyte layer (30) in the completed battery state can be configured to be 5㎛ or more and 100㎛ or less. This thickness can preferably be 8㎛ or more and 80㎛ or less, and more preferably 10㎛ or more and 50㎛ or less.

[0087] For example, the solid electrolyte is in powder form and can be composed of a sulfide-based solid electrolyte.

[0088] Sulfide-based solid electrolytes are, for example, Li2S-P2S5, Li2S-P2S5-LiX (where X is a halogen element, e.g., I, Br, Cl), 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 defined numbers, Z is any one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, or Li2S-SiS2-Li p MO q(p and q are integers, and M is any one of P, Si, Ge, B, Al, Ga, or In). Here, such a solid electrolyte can be formed by melt quenching or mechanical milling of a starting material (e.g., Li2S, P2S5, etc.). Additionally, further heat treatment may be provided after such treatment. The solid electrolyte may be amorphous, crystalline, or a mixture thereof.

[0089] Additionally, it is preferable that the solid electrolyte be the above-mentioned sulfide-based solid electrolyte containing one or more elements selected from the group consisting of sulfur, silicon, phosphorus, and boron. By this, the lithium conductivity of the solid electrolyte layer (30) is improved, and the characteristics of the all-solid-state secondary battery (1) can be further improved. In particular, it is preferable that the solid electrolyte contains at least sulfur, phosphorus, and lithium, and it is more preferable that it contains Li2S-P2S5.

[0090] Here, when the sulfide-based solid electrolyte forming the solid electrolyte includes Li2S-P2S5, the mixed molar ratio of Li2S and P2S5 is preferably in the range of, for example, Li2S:P2S5 = 50:50 to 90:10. Additionally, the solid electrolyte layer (30) may further include a binder. The binder may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDG), polyethylene (PE), or polyacrylic acid (PAA). The binder may be of the same type as the binder in the positive active material layer (12) and the negative active material layer (22), but is not limited thereto.

[0091] (1-4. Household Department)

[0092] As illustrated in FIGS. 1 and 2, the positive electrode layer (10) has a positive current collector (111) protruding to one side from the positive current collector (11) and is connected to external wiring through the positive current collector (111). Similarly, the negative electrode layer (20) has a negative current collector (211) protruding to the other side from the negative current collector (21) and is connected to external wiring through the negative current collector (211). Meanwhile, FIG. 2 is a view of the all-solid-state secondary battery (1) according to the present embodiment from the Z direction (the side of the second conductive member (42) in FIG. 1), and FIG. 1 is a cross-sectional view of the all-solid-state secondary battery (1) cut along line AA in FIG. 2.

[0093] In the present invention, the lateral direction is, for example, a direction facing outward along the surface from the outer edge of the positive current collector (11), and more specifically, a direction perpendicular to the stacking direction of each layer constituting the all-solid-state secondary battery (1).

[0094] In the present invention, the positive current collector (111) is configured to penetrate the insulating member (13) and protrude toward the outside of the insulating member (13). Meanwhile, for convenience of explanation, the direction in which the positive current collector (111) protrudes is called the X direction (protrusion direction), and the direction perpendicular to the protrusion direction in the plan view from the stacking direction is called the Y direction (width direction).

[0095] Meanwhile, in the present invention, the positive current collector (111) and the negative current collector (211) protrude almost parallel and protrude with almost the same length, but the direction of protrusion and the length of protrusion may be the same or different from each other.

[0096] The positive current collector (111) and the negative current collector (211) may protrude in the same direction, but may also protrude in different directions. In this embodiment, the positive current collector (111) and the negative current collector (211) protrude in opposite directions.

[0097] (1-5. Insulating Member)

[0098] The insulating member (13) is provided in close contact with the side (S) of the positive active material layer (12) so as to cover the entire side (S) of the positive active material layer (12) of the positive layer (10), for example. The volume resistivity of the insulating member (13) is 10 12 It is preferable that the value be Ω / cm or higher. The insulating member (13) may be a resin film containing a resin such as polypropylene, polyethylene, or a copolymer thereof. In addition to the polyolefin-based resins mentioned above, the resin may be a vinyl-based resin such as polyvinyl chloride (PVC), a polyacetal resin, an acrylic-based resin such as polymethyl methacrylate (PMMA), a polycarbonate (PC), a polyamide resin, a polyurethane resin, a fluorine-based resin such as polytetrafluoroethylene (PTFE), or a composite resin thereof.

[0099] Since this resin film adheres to the anode layer (10) by a pressurizing process such as an isotropic press, it can be difficult to peel off. Additionally, the insulating member (13) can be formed by mixing insulating fillers, etc., with this resin. By including insulating fillers in the insulating member (13), the adhesion of the insulating member (13) is improved, and the strength of the insulating member (13) can be enhanced. Furthermore, by including insulating fillers along with the resin in the insulating member (13), fine irregularities can be formed on the surface of the insulating member (13). Due to the irregular shape of the surface of the insulating member (13), it can be difficult for the solid electrolyte layer (30) to peel off from the insulating member (13). The insulating fillers can have various shapes, such as particle shape, fiber shape, needle shape, or plate shape. To make the above effect particularly significant, it is preferable that the insulating fillers be fiber shape or non-woven fabric shape.

[0100] From a cost perspective, it is preferable that the insulating filler be composed of one or more materials selected from the group consisting of, for example, fibrous resin, resin nonwoven fabric, aluminum oxide, magnesium oxide, silica, boehmite, barium titanate, barium carbonate, yttrium oxide, and manganese oxide.

[0101] The thickness of the insulating member (13) in the completed state as a battery may, for example, preferably be 20 μm or more and 1000 μm or less, more preferably 50 μm or more and 500 μm or less, and particularly preferably 100 μm or more and 300 μm or less. However, it is not limited thereto. Preferably, the thickness of the insulating member (13) may be changed according to the thickness of the anode layer (10). It is suitable for the thickness of the insulating member (13) to be close to the thickness of the anode layer (10).

[0102] As in the present embodiment, when the positive active material layer (12) is formed on both sides of the positive current collector (11), an insulating member (13) may also be provided on both sides of the positive current collector (11) and the positive current collector (111). In this way, it is preferable that the sum of the two layers of insulating members (13) provided on both sides of the positive current collector (11) and the positive current collector (111) is approximately equal to the sum of the two positive active material layers (12) formed on both sides of the positive current collector (11).

[0103] <2. Characteristic configuration of the all-solid-state secondary battery according to the present invention>

[0104] The all-solid-state secondary battery (1) according to the present invention may further include a first conductive member (41) and a second conductive member (42) that are electrically connected to the positive electrode layer (10) and the negative electrode layer (20), respectively.

[0105] In the present invention, the first conductive member (41) is a conductive member for an anode formed integrally with the anode current collector (11).

[0106] The first conductive member (41) is electrically connected to the positive current collector (11) and can disperse the current flowing in the all-solid-state secondary battery (1) when a short circuit occurs inside the battery due to external impact or penetration such as a nail. The material and shape of the first conductive member (41) are not particularly limited, but it is preferable that it be thin like the positive current collector (11) and preferably formed of the same material as the positive current collector (11).

[0107] Referring to FIG. 3, the first conductive member (41) is provided to extend outward from the positive current collector (11) and may protrude outward through an insulating member. The first conductive member (41) may have, for example, a covering portion (411) having a shape similar to that of the positive current collector (11), and a connecting portion (412) connected to the covering portion (411) and the positive current collector (11).

[0108] It is preferable that, by folding the connection portion (412), the covering portion (411) is provided outside the negative electrode current collector (21) of the all-solid-state secondary battery (1) to cover the outer surface of the negative electrode current collector (21) and to cover part or all of the negative electrode current collector (21) in the stacking direction of the all-solid-state secondary battery (1). FIG. 3 is a cross-sectional view (cross-sectional view along line B-B of FIG. 2) of the all-solid-state secondary battery (1) after the all-solid-state secondary battery (1) is completed by folding the connection portion (412). According to the present embodiment, as described above, the covering portion (411) is formed integrally with the positive current collector (11) and is formed to extend from the positive current collector (11), which is a metal foil formed in a rectangular shape as described below. Therefore, from the perspective of preventing cutting at the connection portion and / or ease of manufacturing, it is preferable that the covering portion (411) be a metal foil with the same width as the positive current collector (11). The shape and thickness of the covering portion (411) are not limited to those described above and can be appropriately changed. The covering portion (411) does not necessarily have the same thickness and shape as the positive current collector (11), and may have various thicknesses and shapes as needed.

[0109] The connecting portion (412) is preferably formed as a strip-shaped metal foil with the same width as the positive current collector (11), as the covering portion (411), but is not limited to this and can have various shapes.

[0110] According to the present invention, the second conductive member (42) is a conductive member for the cathode formed integrally with the cathode current collector (21). The second conductive member (42) is formed integrally with the cathode current collector (21) and is a thin film protruding outward from the cathode current collector (21). It is preferable that it has the same configuration (covering part (421), connection part (422)) and properties as the first conductive member (41) described above, but is not limited to this and can be modified in various ways as long as it has the same function.

[0111] Meanwhile, since the positive electrode layer (10) and the negative electrode layer (20) are short-circuited when the first conductive member (41) and the second conductive member (42) come into contact with each other, they are arranged so as not to come into direct contact with each other. To prevent them from coming into contact, it is preferable to provide an insulating layer (43) for conductive members between the first conductive member (41) and the second conductive member (42). Furthermore, for example, when using an all-solid-state secondary battery (1), an insulating sheet covering both sides thereof can function as the insulating layer (43) for conductive members. Alternatively, when manufacturing the stacked all-solid-state secondary battery (100) of FIG. 10, a buffer material (X) placed on the outermost layer of the stacked all-solid-state secondary battery (100) or between each of the all-solid-state secondary batteries (1) can function as the insulating layer (43) for conductive members.

[0112] <3. Method for manufacturing an all-solid-state secondary battery according to the present invention>

[0113] Next, with reference to FIGS. 4 to 9, an example of a method and sequence for manufacturing an all-solid-state secondary battery (1) according to the present embodiment will be described. FIGS. 4, 7, 8 and 9 are cross-sectional views of an all-solid-state secondary battery in the middle of manufacturing, cut along line AA of FIG. 2.

[0114] The method for manufacturing an all-solid-state secondary battery (1) according to the present embodiment may include the following processes.

[0115] (3-1. Fabrication of the anode layer)

[0116] The materials constituting the positive active material layer (12) (positive active material, binder, etc.) are mixed, and the mixture is stretched into a sheet shape to form a positive sheet, which is then shaped into a rectangular shape using a Thomson knife to produce the positive active material layer (12). The positive active material layer (12) thus produced is pressed and adhered to a positive current collector (11) formed of a rectangular aluminum foil to create a positive structure (see FIG. 4A).

[0117] Referring to FIG. 4B, the anode structure is placed on an aluminum plate covered with a PET film, an insulating member (13) is placed to fit an anode active material layer (12) at both ends of the anode structure, a PET film is placed on the structure to form a laminate pack, and pressure is applied from the lamination direction by isotropic pressure to produce an anode insulating member composite (10A).

[0118] Meanwhile, during the aforementioned pressurization, it is preferable that the aforementioned insulating member (13) has a first current collector protection part (14) that protects the protrusion of the positive current collector part (111). As shown in FIG. 4B, it is preferable that the first current collector protection part (14) covers the positive current collector part (111).

[0119] During the above pressurization, it is preferable that the first current collector protection part (14) has a surface area larger than the area of ​​the positive current collector part (111) so as to cover the positive current collector part (111) without gaps, but its shape is not particularly limited.

[0120] As illustrated in FIG. 5, the first current collector protection part (14) may be formed integrally with, for example, the insulating member (13) and may have the same width and thickness as the insulating member (13). The first current collector protection part (14) is preferably a rectangular shape that protrudes further than the positive current collector (111) in the direction of the positive current collector (111) from the insulating member (13). Meanwhile, for ease of understanding, a virtual line is shown between the insulating member (13) and the first current collector protection part (14) in the drawings.

[0121] Since the first conductive member (41) extends from the positive current collector (111) as well as the positive current collector (11), it is preferable for the insulating member (13) to have a first conductive member protection part (15) that surrounds and protects the first conductive member (41). It is preferable for the first conductive member protection part (15) to cover the entire first conductive member (41) on both sides.

[0122] As shown in FIG. 8C, the first conductive member protection part (15) preferably has an area equal to or larger than the first conductive member (41) so as to cover the entire first conductive member (41) without gaps, and its shape is not particularly limited.

[0123] As illustrated in FIG. 5, the first conductive member protection portion (15) is formed integrally with the insulating member (13) and may have the same width and thickness as the insulating member (13). The first conductive member protection portion (15) is preferably a rectangular shape protruding from the insulating member (13) toward the first conductive member (41). For ease of understanding, a virtual line is shown between the insulating member (13) and the first conductive member protection portion (15) in the drawings.

[0124] In this embodiment, as shown in FIGS. 6A and 6B, two insulating materials (13A) are prepared. As shown in FIG. 4B, the two insulating materials (13A) are arranged so that both sides of the positive current collector (111) are fitted in the first current collector protection part (14) and both sides of the first conductive member (41) are fitted in the first conductive member protection part (15), respectively, and isotropic treatment is performed.

[0125] (3-2. Fabrication of the Cathode Layer)

[0126] A material (negative active material, binder, etc.) constituting the negative active material layer (22) is added to a polar solvent or a non-polar solvent to produce a negative active material layer coating solution. Then, as shown in FIG. 7A, the negative active material layer coating solution is applied onto a negative current collector (21) and dried. This is then shaped into a rectangular form using a Thomson knife to produce a negative layer (20). Meanwhile, a negative current collector (211) and a second conductive member (42) extend from the negative current collector (21).

[0127] (3-3. Fabrication of Solid Electrolyte Layer)

[0128] The solid electrolyte layer (30) can be made of a solid electrolyte formed from a sulfide-based solid electrolyte material. The method of making the solid electrolyte is as follows.

[0129] First, the starting material is processed using the melt quenching method or mechanical milling method.

[0130] For example, in the case of the melt quenching method, a sulfide-based solid electrolyte material can be produced by mixing a predetermined amount of starting materials (e.g., Li2S, P2S5, etc.) and forming them into pellets, reacting them in a vacuum at a predetermined reaction temperature, and then quenching them. Meanwhile, the reaction temperature of the mixture of Li2S and P2S5 is preferably 400°C to 1000°C, and more preferably 800°C to 900°C. The reaction time is preferably 0.1 hours to 12 hours, and more preferably 1 hour to 12 hours. The quenching temperature of the reactants is usually 10°C or lower, and preferably 0°C or lower. The quenching rate is usually 1°C / sec to 10000°C / sec, and preferably 1°C / sec to 1000°C / sec.

[0131] In the case of mechanical milling, sulfide-based solid electrolyte materials can be produced by using a ball mill or the like to react starting materials (e.g., Li2S, P2S5, etc.) by stirring. Meanwhile, although the stirring speed and stirring time in mechanical milling are not particularly limited, a faster stirring speed can accelerate the formation rate of the sulfide-based solid electrolyte material, and a longer stirring time can increase the conversion rate of the raw materials into the sulfide-based solid electrolyte material.

[0132] Subsequently, a mixed raw material obtained by melt quenching or mechanical milling can be heat-treated at a predetermined temperature and then ground to produce a particulate solid electrolyte. If the solid electrolyte has a glass transition point, it can be transformed from an amorphous state to a crystalline state through heat treatment.

[0133] Next, a solid electrolyte layer coating solution comprising the solid electrolyte obtained by the above method, other additives (e.g., binder, etc.), and a dispersant is prepared. The dispersant may be a general-purpose non-polar solvent such as xylene or diethylbenzene. Alternatively, the dispersant may be a polar solvent that is relatively less reactive with the solid electrolyte. The concentrations of the solid electrolyte and other additives may be appropriately adjusted according to the composition of the solid electrolyte layer (30) and the viscosity of the liquid composition, etc.

[0134] A solid electrolyte sheet is produced by applying the liquid composition of the aforementioned solid electrolyte to a PET film with a demolded surface using a blade and drying it, thereby forming a solid electrolyte layer (30) on the PET film.

[0135] (3-4. Additive Manufacturing Process)

[0136] As shown in FIG. 7A, a solid electrolyte sheet having the same shape as or a larger shape than the cathode layer (20) is laminated on one side of the cathode layer (20) fabricated above. As shown in FIG. 7B, this is pressed under equal pressure to bring the cathode layer (20) and the solid electrolyte layer (30) into close contact and become one. If the solid electrolyte layer (30) is larger than the cathode layer (20), the portion of the solid electrolyte layer (30) protruding outward from the cathode layer (20) can be removed. The laminated structure formed in this way is called an electrolyte cathode structure (20A).

[0137] Next, as shown in FIG. 8A, two electrolyte negative structures (20A) are laminated on both sides of the aforementioned positive insulating member composite (10A). At this time, the electrolyte negative structures (20A) are laminated so that the solid electrolyte layer (30) of the electrolyte negative structures (20A) comes into contact with both sides of the positive layer (10). As shown in FIG. 8B, the entire assembly is laminated and pressed at an equal pressure to manufacture an all-solid-state secondary battery (1A).

[0138] As illustrated in FIGS. 6A and 6B, in order to protect the cathode current collector (211) and the second conductive member (42) during such isobaric pressurization, the insulating material (13A) may further include a second current collector protection part (16) and a second conductive member protection part (17) that support the cathode current collector (211).

[0139] As shown in FIG. 8B, it is preferable that the second current collector protection part (16) has a larger area than the negative current collector part (211) so as to support the entire negative current collector part (211) when pressure is applied at equal pressure. However, its shape is not particularly limited. As shown in FIG. 5, it is preferable that the second current collector protection part (16) be formed integrally with, for example, the insulating member (13) and have a rectangular shape that protrudes from the insulating member (13) in the same direction as the negative current collector part (211) with the same width and thickness as the insulating member (13). For ease of understanding, a virtual line is indicated between the insulating member (13) and the second conductive member protection part (16) in the drawings.

[0140] As shown in FIG. 8C, the second conductive member protection part (17) preferably has an area equal to or larger than that of the second conductive member (42) so as to support the entire second conductive member (42) when equal pressure is applied, and its shape is not particularly limited. As shown in FIG. 5, the second conductive member protection part (17) is preferably formed integrally with the insulating member (13), for example, and has a rectangular shape that protrudes from the insulating member (13) in the same direction as the second conductive member (42) with the same width and thickness as the insulating member (13). For ease of understanding, a virtual line is shown between the insulating member (13) and the second conductive member protection part (17) in the drawings.

[0141] Meanwhile, referring to FIGS. 1, 8B and 8C, it appears that there are gaps between the negative current collector (211) and the insulating member (13), and between the second conductive member (42) and the insulating member (13). However, in the stacked state, there are actually mostly no gaps between them, and when pressed, the negative current collector (211) and the second conductive member (42) can be supported by the insulating member (13) by being pressed by the insulating member (13).

[0142] In the direction in which the positive current collector (111) and / or negative current collector (211) protrude, it is preferable that part or all of the outer edge (1E) of the insulating member (13) be provided outside the outer edge (2E) of the negative layer (20). Furthermore, it is preferable that the outer edge (2E) of the negative layer (20) be located on the insulating member (13). Accordingly, even if the negative layer (20) is pressed tightly against the positive layer (10) by external pressure and deformation occurs, a short circuit caused by physical contact between the positive layer (10) and the negative layer (20) can be suppressed.

[0143] As illustrated in FIGS. 1 and 2, the outer magnetic edge (1E) of the insulating member (13) refers to the outermost edge in a direction perpendicular to the stacking direction from the side of the insulating member (13). Additionally, the outer magnetic edge (2E) of the cathode layer (20) refers to the outermost edge in a direction perpendicular to the stacking direction from the side of the cathode layer (20). In the present invention, for example, the outer magnetic edge (2E) of the cathode layer (20) is the outermost edge in a direction perpendicular to the stacking direction from the side of the cathode current collector (21) or the cathode active material layer (22). Meanwhile, in the present invention, since the covering portion (421) of the second conductive member (42) has the same shape as the cathode layer (20), the outer magnetic edge of the second conductive member (42) in FIG. 2 is the same as the outer magnetic edge (2E) of the cathode layer (20).

[0144] (3-5. Isostatic Press)

[0145] Below, the pressurization treatment (pressurization process) by the aforementioned isostatic press is described.

[0146] The isostatic pressing is performed by placing a support plate, for example, a SUS plate, on at least one side of the laminate. By this isostatic pressing, the laminates forming the all-solid-state secondary battery (1), such as the positive insulating member composite (10A) and the electrolyte negative electrode structure (20A), can be pressed in the stacking direction.

[0147] The pressure medium may be a liquid (water, oil, etc.) or a powder. It is more preferable to use a liquid as the pressure medium. The pressure is not particularly limited, but may be, for example, 10 MPa to 1000 MPa, preferably 100 MPa to 500 MPa. The pressurization time is not particularly limited, but may be, for example, 1 minute to 120 minutes, preferably 5 minutes to 30 minutes. The temperature of the pressure medium is not particularly limited, but may be, for example, 20°C to 200°C, preferably 50°C to 100°C.

[0148] Meanwhile, during the isostatic pressing, it is preferable that the laminate constituting the all-solid-state secondary battery (1) be laminated with a resin film together with a support plate and isolated from the external atmosphere.

[0149] Compared to other press methods such as roll presses, the isostatic press is advantageous in that it enables high pressure pressing that does not affect the suppression of breakage of the layers constituting the all-solid-state secondary battery (1), prevention of bending of the all-solid-state secondary battery (1), and increase in electrode area.

[0150] After that, one or more excess portions of the first current collector protection part (14), the second current collector protection part (16), the first conductive member protection part (15), and the second conductive member protection part (17) of the all-solid-state secondary battery (1A) before cutting are removed, and the all-solid-state secondary battery (1B) before folding is obtained. Meanwhile, FIGS. 8B and FIGS. 8C illustrate the all-solid-state secondary battery (1A) before cutting, and FIGS. 9A and FIGS. 9B illustrate the all-solid-state secondary battery (1B) before folding. Referring to FIGS. 9A and FIGS. 9B, the insulating member (13) is formed from two insulating materials (13A), but the insulating materials (13A) can be heated, for example, to become one.

[0151] At this time, for example, as illustrated in FIG. 6B, it is preferable to provide a notch (13C) in the thickness direction between the insulating member (13) and the first current collector protection part (14), and between the insulating member (13) and the second current collector protection part (16), so that they can be easily removed. Additionally, it is preferable that the edge of the notch (13C) penetrates the insulating member (13). This is because it makes it easy to remove the first current collector protection part (14) and the second current collector protection part (16). It is also preferable that such a notch be formed between the insulating member (13) and the first conductive member protection part (15), and between the insulating member (13) and the second conductive member protection part (17).

[0152] Meanwhile, the method of removing the first current collector protection part (14) and the second current collector protection part (16) is not limited to the above. For example, they may be removed by tools or machines rather than by human hands. The method of removing the first conductive member protection part (15) and the second conductive member protection part (17) is also similar. Thus, by removing the first current collector protection part (14), the first conductive member protection part (15), the second current collector protection part (16), and the second conductive member protection part (17) from the insulating member material (13A), the side surface of the insulating member (13) may be rougher compared to other surfaces of the insulating member material (13A).

[0153] Finally, the all-solid-state secondary battery (1) illustrated in FIGS. 1 to 3 is completed by folding the first conductive member (41) and the second conductive member (42) so that at least a portion of the first conductive member (41) and the second conductive member (42) are provided on the outside of the negative electrode current collector (21). At this time, both the first conductive member (41) and the second conductive member (42) may be provided on the outside of the negative electrode current collector (21) in one direction of the all-solid-state secondary battery (1).

[0154] When the first conductive member (41) is folded as described above, there is a possibility that a portion of the side of the first conductive member (41) may come into contact with the negative current collector (21) or the negative active material layer (22) and short circuit. According to the present invention, a second insulating member (44) is provided between the sides of the negative current collector (21) and the negative active material layer (22) and the side of the first conductive member (41), so that the side of the first conductive member (41) does not come into contact with the negative current collector (21) or the negative active material layer (22). For example, before folding the first conductive member (41), the second insulating member (44) may be provided on the side of the negative current collector (21) and the negative active material layer (22). Additionally, when the second conductive member (42) is folded, there is a possibility that a portion of the side of the second conductive member (42) may come into contact with the edge of the folded first conductive member (41) and short circuit. Here, it is preferable to provide a third insulating member (45) between the side of the second conductive member (42) and the edge of the first conductive member (41). In this case, before folding the second conductive member (42), the third insulating member (45) may be provided at the edge of the first conductive member (41).

[0155] It is preferable that the second insulating member (44) and the third insulating member (45) are provided to cover the entire side surface in a direction different from the protruding direction of the aforementioned negative current collector (21), negative active material layer (22), and first conductive member (41).

[0156] <4. Effects of the all-solid-state secondary battery according to the present invention>

[0157] According to the present invention, the all-solid-state secondary battery (1) includes a first conductive member (41) and a second conductive member (42) integrally formed on each of the positive electrode current collector (11) and the negative electrode current collector (21). Therefore, even if a short circuit occurs between the positive electrode layer (10) and the negative electrode layer (20) due to an external impact or penetration of an electrical conductor such as a nail, the short-circuit current can be distributed to the first conductive member (41) and the second conductive member (42). Accordingly, heat generation of the all-solid-state secondary battery (1) is suppressed, thereby avoiding ignition or explosion.

[0158] Furthermore, since the first conductive member (41) and the second conductive member (42) are formed integrally with the positive current collector (11) and the negative current collector (21), respectively, a solid-state secondary battery (1) having the first conductive member (41) and the second conductive member (42) can be manufactured in the same order as in the conventional method, without the cumbersome work of attaching a multilayer metal foil by welding, etc., when forming the conductive member separately.

[0159] <5. Method for manufacturing a stacked all-solid-state secondary battery according to the present invention>

[0160] A stacked all-solid-state secondary battery (100) can be manufactured by stacking a plurality of all-solid-state secondary batteries (1) manufactured by the above-described method.

[0161] The first conductive member (41) and the second conductive member (42) may be arranged for each solid-state secondary battery (1). Alternatively, as shown in FIG. 10, the first conductive member (41) and the second conductive member (42) may be arranged in a stacking direction for one solid-state secondary battery (1) or a plurality of solid-state secondary batteries (1).

[0162] In this manner, when multiple all-solid-state secondary batteries (1) are bundled and stacked, the positive current collectors (111) and the negative current collectors (211) are arranged neatly and stacked, and then pressure or welding is applied. Then, the positive current collectors (111) and the negative current collectors (211) are each made electrically connected.

[0163] <6. Charging and discharging of an all-solid-state secondary battery according to the present invention>

[0164] The charging and discharging of the all-solid-state secondary battery (1) according to the present invention will be described below.

[0165] Since the negative active material, which forms an alloy or compound with lithium within the negative active material layer (22), forms an alloy or compound with lithium ions, lithium is absorbed within the negative active material layer (22) during the initial charging of the all-solid-state secondary battery (1) according to the present invention. Subsequently, after the charging capacity of the negative active material layer (22) is exceeded, metallic lithium is precipitated on one or both surfaces of the negative active material layer (22), and a metallic lithium layer is formed. Since the metallic lithium is formed by diffusing through the negative active material capable of forming an alloy or compound, it is not formed in a tree-branch shape (dendrite shape) but is formed uniformly mainly between the negative active material layer (22) and the negative current collector (21). During discharge, the metallic lithium within the negative active material layer (22) and the metallic lithium layer ionizes and moves toward the positive active material layer (12). Consequently, since metallic lithium can be used as a negative active material, the energy density can be improved.

[0166] The precipitation of metallic lithium occurs because the negative electrode active material forms a specific material (i.e., a material that forms an alloy or compound with lithium). During discharge, lithium within the negative electrode active material layer (22) and the metallic lithium layer ionizes and moves toward the positive electrode layer (10). Therefore, the all-solid-state secondary battery (1) can use metallic lithium as the negative electrode active material. More specifically, if the charging capacity of the negative electrode layer (20) (the total charging capacity by the negative electrode active material layer (22) and the metallic lithium layer) is 100%, it is desirable to ensure that at least 80% of the charging capacity is exerted by the metallic lithium layer.

[0167] Furthermore, it is preferable that the metal lithium layer be formed inside the negative electrode layer (20) (i.e., between the negative electrode active material layer (22) and the negative electrode current collector (21). In this case, since the negative electrode active material layer (22) covers the metal lithium layer, the negative electrode active material layer (22) can function as a protective layer for the metal lithium layer. Accordingly, short circuits and capacity degradation of the all-solid-state secondary battery (1) are suppressed, and the characteristics of the all-solid-state secondary battery (1) can be improved.

[0168] A method to enable the deposition of metallic lithium in the negative electrode active material layer (22) may, for example, make the charging capacity of the positive electrode active material layer (12) greater than the charging capacity of the negative electrode active material layer (22). Specifically, it is preferable that the ratio (capacity ratio) of the charging capacity of the positive electrode active material layer (12) and the charging capacity of the negative electrode active material layer (22) satisfies the requirements of Formula 1 below.

[0169] [Formula 1]

[0170] 0.002

[0171] a: Charge capacity (mAh) of the anode composite layer

[0172] b: Charge capacity (mAh) of the cathode composite layer

[0173] ​If the capacity ratio expressed by formula (1) is greater than 0.002, the negative electrode active material layer (22) can sufficiently mediate the precipitation of metallic lithium into lithium ions regardless of the composition of the negative electrode active material layer (22), so that a metallic lithium layer can be easily formed. In addition, if the metallic lithium layer is formed between the negative electrode active material layer (22) and the negative electrode current collector (21), the negative electrode active material layer (22) can sufficiently function as a protective layer. Therefore, the capacity ratio may be more preferably 0.01 or greater, and even more preferably 0.03 or greater. In addition, if the capacity ratio is less than 0.5, the negative electrode active material layer (22) does not store most of the lithium during charging, so a metallic lithium layer can be uniformly formed regardless of the composition of the negative electrode active material layer (22). The capacity ratio may be more preferably 0.2 or less, and even more preferably 0.1 or less.

[0174] It is more desirable for the capacity ratio to be greater than 0.01. This is because if the capacity ratio is 0.01 or less, there is a concern that the characteristics of the all-solid-state secondary battery (1) may deteriorate. This is because the negative electrode active material layer (22) may not function sufficiently as a protective layer. For example, if the thickness of the negative electrode active material layer (22) is very thin, the capacity ratio may be 0.01 or less. In this case, the negative electrode active material layer (22) may collapse due to repeated charging and discharging, and there is a possibility that dendrites may precipitate or grow. As a result, the characteristics of the all-solid-state secondary battery (1) may deteriorate. In addition, it is desirable for the capacity ratio to be less than 0.5. This is because if the capacity ratio is 0.5 or more, the amount of lithium precipitated in the negative electrode layer (20) decreases, and the battery capacity may decrease. For the same reason, it is more desirable for the capacity ratio to be less than 0.25. In addition, if the capacity ratio is less than 0.25, the output characteristics of the battery may also be improved.

[0175] Here, the charging capacity of the positive active material layer (12) can be obtained by multiplying the charging capacity (mAh / g) of the positive active material by the mass of the positive active material within the positive active material layer (12). When multiple types of positive active materials are used, the value of charging capacity × mass for each positive active material can be calculated, and the sum of these can be the charging capacity of the positive active material layer (12). The charging capacity of the negative active material layer (22) can also be calculated in the same way. In other words, the charging capacity of the negative active material layer (22) can be obtained by multiplying the charging capacity (mAh / g) of the negative active material by the mass of the negative active material within the negative active material layer (22). When multiple types of negative active materials are used, the value of charging capacity × mass for each negative active material can be calculated, and the sum of these can be the capacity of the negative active material layer (22). Here, the charging capacity of the positive active material and the negative active material is the capacity estimated using an all-solid-state half cell using lithium metal as the opposite electrode. In fact, the charging capacity of the positive active material layer (12) and the negative active material layer (22) can be directly measured by using an all-solid-state half cell.

[0176] A specific method for directly measuring the charge capacity may be as follows. A test cell using a positive composite material layer as the working electrode and Li as the opposite electrode is fabricated, and the charge capacity of the positive composite material layer can be measured by CC-CV charging from the open-circuit voltage (OCV) to the upper charge voltage limit. The upper charge voltage limit can be determined according to the standard of JIS C 8712:2015. The upper charge voltage limit for a lithium cobalt acid-based positive composite material layer is 4.25 V, and the upper charge voltage limit for other positive composite material layers can be obtained by applying the provisions of A.3.2.3 (Safety requirements when applying other upper charge voltage limits) of JIS C 8712:2015. A test cell using a negative composite material layer as the working electrode and Li as the opposite electrode is fabricated, and the charge capacity of the negative composite material layer can be measured by CC-CV charging from the open-circuit voltage (OCV) to 0.01 V.

[0177] The charging capacity measured in this way is divided by the mass of each active material to calculate the charging capacity. The charging capacity of the positive active material layer (12) may be the initial charging capacity measured during the first cycle of charging.

[0178] <7. Other embodiments according to the present invention>

[0179] The all-solid-state secondary battery according to the present invention may not be limited to the aforementioned.

[0180] As described above, it is preferable that two second conductive members extend from the cathode layer, but as shown in FIG. 11, one second conductive member may also extend from the cathode layer.

[0181] The solid electrolyte layer (30) provided between the anode layer and the cathode layer may be at least one layer, and may be stacked in two, three, four layers or more layers.

[0182] The present invention is not limited to all-solid-state lithium-ion secondary batteries, but can be applied to all-solid-state secondary batteries having a thin current collector and formed by pressure treatment such as an isostatic press.

[0183] <Example>

[0184] The present invention will be described below with more specific examples, but the invention is not limited to these.

[0185] (Example 1)

[0186] [Fabrication of the bipolar layer structure]

[0187] LiNi as the positive active material 0.8 Co 0.15 Mg 0.05O2 (NCM) was used. This positive active material can be coated with Li2O-ZrO2. Li6PS5Cl, an argyrodite-type crystal, was used as the solid electrolyte. Additionally, polytetrafluoroethylene (DuPont’s Teflon (registered trademark) binder) was used as the binder. Additionally, carbon nanofibers (CNF) were used as the conductive aid. Next, these materials were mixed in a mass ratio of positive active material:solid electrolyte:conductive aid:binder = 85:15:3:1.5, and the mixture was stretched into a sheet shape to produce a positive sheet. This positive sheet was cut into an appropriate shape for use. A 10㎛ thick aluminum foil coated with a 1㎛ thick undercoating layer was processed into a predetermined shape using a pinnacle die (registered trademark) and used as a positive current collector (11). The positive current collector (11) is rectangular in shape and is formed integrally with a first conductive member (41) that is also rectangular in shape.

[0188] The positive current collector (11) and the positive active material layer (12) are placed on a PET film (hereinafter referred to as a release film) having a release-treated surface, and the edge portions of two insulating materials (13A) surround the positive active material layer (12). Meanwhile, the first current collector protection portion (14) is provided to sandwich the positive current collector (111) protruding from the positive current collector (11), and the first conductive member protection portion (15) is provided to sandwich the first conductive member (41). After that, this is covered with a release film, and a SUS metal plate (support material) having a thickness of 0.3 mm is covered on both sides with a shape that fits the edge portions of the positive active material layer (12) and the insulating material (13A) (i.e., a shape that does not cover the first current collector protection portion (14) and the first conductive member protection portion (15) within the insulating material (13A), and then a vacuum laminate pack is formed. This was placed in a pressurized medium and subjected to hydrostatic treatment at 490 MPa (a compaction process by an isostatic press) to integrate the insulating member (13) of the insulating material (13A) with the positive current collector (11) and the positive active material layer (12).

[0189] In this way, an anode insulating member composite (10A) is manufactured having an anode layer (10) in which an anode active material layer (12) is laminated on both sides of an anode current collector (11), a first conductive member (41), an insulating member (13) covering a side (side cross-section (S)) different from the lamination direction of the anode active material layer (12), a first current collector protection member (14), and a first conductive member protection member (15).

[0190] The aforementioned insulating material (13A) was manufactured by cutting an insulating resin film with a pinnacle die (registered trademark). The insulating resin film used in this embodiment is xCcure (registered trademark) made of polycarbonate material from AGC. As shown in FIG. 6A, the insulating material (13A) has a shape having four extensions extending in all directions from a ring-shaped insulating material (13A) having a receiving hole sized to precisely surround the edge of the positive active material layer (12). The square first and second current collector protection parts (14, 16) protecting the current collectors (111, 211) extend in opposite directions. The square first and second conductive member protection parts (15, 17) protecting the first and second conductive members (41, 42) extend in opposite directions from the direction in which the first and second current collection member protection parts (14, 16) extend.

[0191] [Fabrication of the cathode layer]

[0192] A negative current collector (21) with a total thickness of 11 μm is formed on both sides of it, plated with nickel with a thickness of 0.5 μm. The negative current collector (21) is formed integrally with the second conductive member. As the negative active material, CB1 (nitrogen adsorption ratio) manufactured by Asahi Carbon Co., Ltd. (the surface area is approximately 339 m²) is used. 2 / g, DBP feeding amount is approximately 193ml / 100g), Asahi Carbon CB2 (nitrogen adsorption ratio surface area is approximately 52 m² 2 / g, DBP feeding amount was approximately 193 ml / 100 g), and silver particles with a particle size of 60 nm were prepared. Meanwhile, the particle size of the silver particles was, for example, the median diameter (so-called D50) measured using a laser particle size distribution meter. Next, 1.5 g of CB1, 1.5 g of CB2, and 1 g of silver particles were placed in a container, and 4 g of N-methylpyrrolidone (NMP) solution containing 5 mass% of a binder (#9300 of Kureha Co., Ltd.) was added to it. Then, the mixed solution was stirred while gradually adding a total amount of 30 g of NMP to this mixed solution to prepare a cathode active material layer coating solution. Using a blade coater, a cathode active material layer coating solution was applied onto a cathode current collector (21), and the cathode active material layer (22) was formed by drying in air at 80°C for about 20 minutes. The laminate thus obtained was vacuum dried at 100°C for about 12 hours and processed into a predetermined shape using a pinnacle die (registered trademark). By the above process, a cathode layer (20) was produced.

[0193] [Fabrication of Solid Electrolyte Sheets]

[0194] A solid electrolyte layer coating solution was prepared.

[0195] To this end, a primary mixed slurry was formed by adding an SBR binder dissolved in dehydrated xylene to Li2-P2S5 (80:20 mol%) amorphous powder for a sulfide-based solid electrolyte at a mass of 1% relative to the solid electrolyte. A secondary mixed slurry was formed by adding appropriate amounts of dehydrated xylene and dehydrated diethylbenzene to the primary mixed slurry to adjust the viscosity.

[0196] To improve the dispersibility of the secondary mixing slurry, a tertiary mixing slurry was formed by adding zirconia balls with a diameter of 5 mm to the secondary mixing slurry such that the space, the secondary mixing slurry, and the zirconia balls each occupied 1 / 3 of the total volume of the mixing container. The tertiary mixing slurry was fed into a rotary mixer and stirred at 3000 rpm for 3 minutes to prepare a solid electrolyte layer coating solution. The solid electrolyte layer coating solution was applied onto a PET film with a release-treated surface using a blade, dried on a hot plate at 40°C for 10 minutes, and then vacuum dried at 40°C for 12 hours to obtain a solid electrolyte sheet. The thickness of the solid electrolyte layer after drying was approximately 65 μm. The dried solid electrolyte sheet was processed to a predetermined size using a Thomson knife.

[0197] [Fabrication of Electrolyte Cathode Structure]

[0198] A solid electrolyte sheet is provided on the surface of the cathode layer (20) so that the solid electrolyte layer (30) and the cathode active material layer (22) come into contact, and this is placed on a support material (e.g., an aluminum plate with a thickness of 3 mm with a release film attached) and vacuum laminated in a pack including the support material.

[0199] By sinking it in a pressurized medium and performing hydrostatic treatment (a compaction process by an isostatic press) at 50 MPa, the solid electrolyte layer on the solid electrolyte sheet is transformed into an integral with the cathode layer (20). In this way, an electrolyte cathode structure (20A) is formed.

[0200] [Production of All-Solid State Secondary Batteries]

[0201] A composite of an anode layer insulating member (10A) was placed on a release film to be sandwiched between two electrolyte negative structures (20A) to obtain an all-solid-state secondary battery laminate before pressurization. The all-solid-state secondary battery laminate was covered with a release film, and both sides thereof were covered with a support material (e.g., a 0.3 mm thick SUS metal plate having the same shape as that used in the fabrication of the anode layer), and then vacuum laminated and packed including the support material. It was immersed in a pressurized medium and subjected to hydrostatic treatment (a compaction process by an isostatic press) at 490 MPa to obtain an all-solid-state secondary battery (1A) before cutting. Finally, a first current collector protection part and a second current collector protection part were cut from the all-solid-state secondary battery (1A) before cutting to obtain a single cell (single cell) of an all-solid-state secondary battery (1B) before folding.

[0202] Meanwhile, according to the present embodiment, an aluminum plate or a SUS metal plate is used as the support material, but any material having sufficient strength to withstand pressure treatment by isostatic pressure may be used.

[0203] [Stacking of All-Solid State Secondary Batteries]

[0204] After placing all-solid-state secondary batteries one by one between six resin films having a thickness of 300 μm, the first conductive member and the second conductive member of each single cell were both folded in the stacking direction of the all-solid-state secondary battery cell, and the first conductive member and the second conductive member were gathered at one end of the stacked all-solid-state secondary battery and placed in a stacked state. At this time, to prevent the conductive members from making direct electrical contact with each other, a polyimide film with a thickness of 25 μm was inserted between the conductive members to provide insulation. After ultrasonically welding an aluminum tab to the positive current collector and a nickel tab to the negative current collector, respectively, the stacked all-solid-state secondary battery (100) was obtained by vacuum laminating.

[0205] [Charging and Discharging Evaluation of All-Solid State Secondary Batteries]

[0206] The stacked all-solid-state secondary battery fabricated in this manner was sandwiched between 1 mm thick insulating sheets in its stacking direction and sandwiched between two metal plates. A screw containing a disc spring was passed through a hole drilled in the metal plate, and the screw was tightened to apply a pressure of 1.0 MPa to the stacked all-solid-state secondary battery. After charging to an upper limit voltage of 4.25 V with a constant current of 0.1 C at 45°C, it was charged at a constant voltage until the current reached 0.05 C. The characteristics of the battery were evaluated by the charge / discharge evaluation device TOSCAT-3100 under charge / discharge conditions of discharging at 0.1 C to a cutoff voltage of 2.5 V. The results are shown in Fig. 12.

[0207] [Nail Piercing Test]

[0208] A nail piercing test evaluation of a stacked all-solid-state secondary battery was performed using a nail piercing test device. Specifically, the stacked all-solid-state secondary battery charged in the same sequence as the charge-discharge evaluation described above was detached from the metal plate, placed and fixed on a bakelite plate with a Φ10mm hole, and a nail (Φ3mm, tip angle 36°) was pierced in the stacking direction from the side where the conductive material is stacked at a speed of 50mm / sec to evaluate the stability of the stacked all-solid-state secondary battery. The results are shown in Table 1.

[0209] (Example 2)

[0210] An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that an insulating material was used that has only the first current collector protection part and the second current collector protection part, and does not have the first conductive member protection part and the second conductive member protection part. As a result, there were cases where the first conductive member and the second conductive member physically detached from the positive current collector and the negative current collector after pressure molding of the all-solid-state secondary battery.

[0211] (Comparative Example 1)

[0212] A stacked all-solid-state secondary battery was fabricated in the same manner as in Example 1, except that the insulating material used in Example 2 was used, and a positive current collector without a first conductive member and a negative current collector without a second conductive member were used, and the aforementioned nail puncture test was performed. The results are shown in Table 1. In addition, the results of the aforementioned “charge-discharge evaluation of the all-solid-state secondary battery” are shown in FIG. 13.

[0213] (Comparative Example 2)

[0214] A stacked all-solid-state secondary battery was fabricated in the same manner as in Comparative Example 1. Subsequently, a separate nickel-plated copper foil with a thickness of 11 μm, which was not integrally formed with the current collector, was used as a conductive member. Six conductive members were welded to the positive current collector and the negative current collector, respectively. Ultrasonic welding and resistance welding methods were used for welding. A stacked all-solid-state secondary battery having conductive members was fabricated. Since the conductive members and the current collectors were made of different materials and a large number of conductive members were used, the welded portion became thick, making it difficult to weld the current collectors and the conductive members, resulting in some welding defects. The stacked all-solid-state secondary battery of Comparative Example 2 was subjected to the aforementioned nail puncture test. The results are shown in Table 1. In addition, the results of the aforementioned “Charge-Discharge Evaluation of All-Solid-State Secondary Battery” are shown in Fig. 14.

[0215] Ease of Manufacturing of Conductive Components Nail Piercing Test Results Example 1: Integrated Type - Easy Ignition and No Fire Comparative Example 1: None - Easy Explosion Comparative Example 2: Integrated Type - Difficult - No Ignition and Fire

[0216]

[0217] (Discussion of Results)

[0218] Referring to Table 1, the results of a nail puncture test on a stacked solid-state secondary battery using an all-solid-state secondary battery according to an embodiment of the present invention having a first conductive member and a second conductive member showed that the heat generation of the solid-state secondary battery was reduced. That is, thermal runaway did not occur, and ignition or fire did not occur.

[0219] As a result of a nail piercing test on a stacked solid-state secondary battery using a solid-state secondary battery according to Comparative Example 1, which does not have a first conductive member and a second conductive member, the solid-state secondary battery exploded.

[0220] In the all-solid-state secondary battery and stacked all-solid-state secondary battery according to Comparative Example 2, which use a first conductive member and a second conductive member that are not integrally formed with a positive current collector or a negative current collector, it is necessary to weld the positive current collector and the first conductive member, and the negative current collector and the second conductive member separately. In this case, welding may be difficult depending on the combination of materials between each current collector and each conductive member. In addition, there was a problem that welding was difficult as the thickness increased due to the presence of multiple welding sites.

[0221] Meanwhile, as shown in FIG. 12, the stacked all-solid-state secondary battery according to Example 1 exhibits good charge-discharge characteristics. As shown in FIG. 13, it exhibits the same charge-discharge characteristics as the all-solid-state secondary battery according to Comparative Example 1 (i.e., an all-solid-state secondary battery that does not have a first conductive member and a second conductive member). In addition, the same results are obtained for the all-solid-state secondary battery according to Comparative Example 2. From these results, the difference in the nail puncture test performance of the stacked all-solid-state secondary batteries according to the Examples and Comparative Examples is due to the presence or absence of a conductive member and whether the conductive member is formed integrally.

[0222] Comparing Example 1 and Example 2, using an insulating material having a first conductive member protection part and / or a second conductive member protection part made it easier to manufacture an all-solid-state secondary battery and a stacked all-solid-state secondary battery.

Claims

1. Bipolar layer; Solid electrolyte layers provided on each side of the anode layer; A cathode layer provided with the solid electrolyte layer on the side facing the anode layer and on the opposite side, respectively; An insulating member positioned to cover the side of the anode layer; A thin first conductive member protruding outwardly from the anode layer through the insulating member; and It includes a thin second conductive member protruding outward from the above cathode layer, and The first conductive member is formed integrally with the anode layer, and The second conductive member is formed integrally with the cathode layer, and A solid-state secondary battery in which the first conductive member and the second conductive member are insulated from each other, and the edges of the first conductive member and the edges of the second conductive member are provided on the outer side of the negative electrode layer.

2. In Claim 1, It further includes a thin first current collector that protrudes outwardly through the insulating member from the anode layer, and A solid-state secondary battery in which the first conductive member and the first current collector protrude in different directions.

3. In Claim 1, It further includes a thin second current collector protruding outward from the above cathode layer, and A solid-state secondary battery in which the second conductive member and the second current collector protrude in different directions.

4. In Claim 1, A thin first current collector protruding outwardly from the anode layer through the insulating member; and It further includes a thin second current collector protruding outward from the above cathode layer, and A solid-state secondary battery in which the first current collector and the second current collector protrude in different directions.

5. In Claim 1, A solid-state secondary battery provided with a harmonizing member on at least a portion of the side of the insulating member.

6. In Claim 1, The above insulating member is a solid-state secondary battery containing resin.

7. In Claim 1, The above insulating member is an all-solid-state secondary battery containing an insulating filler.

8. In Claim 7, The above insulating filler comprises one or more materials selected from the group consisting of fibrous resin, resin nonwoven fabric, aluminum oxide, magnesium oxide, silica, boehmite, barium titanate, barium carbonate, yttria, and manganese oxide, in an all-solid-state secondary battery.

9. In Claim 2, The above-mentioned first current collector extends outwardly from one end of the anode layer, and A solid-state secondary battery in which, when viewed in the stacking direction, part or all of the outer edge of the insulating member on the side where the first current collector is positioned is provided outside the outer edge of the negative electrode layer.

10. In Claim 1, The above solid electrolyte layer comprises a sulfide-based solid electrolyte containing lithium, phosphorus, and sulfur, in an all-solid-state secondary battery.

11. In Claim 1, The above-mentioned negative electrode layer comprises one or more of a negative electrode active material that forms an alloy with lithium and a negative electrode active material that forms a compound with lithium, and is an all-solid-state secondary battery in which metallic lithium is precipitated inside the negative electrode layer during charging.

12. In Claim 11, An all-solid-state secondary battery in which more than 80% of the charge capacity of the above-mentioned negative electrode layer is exerted by the above-mentioned metallic lithium.

13. In Claim 1, The above-mentioned cathode layer comprises one or more selected from the group consisting of amorphous carbon, gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, and zinc, forming an all-solid-state secondary battery.

14. A stacked all-solid-state secondary battery comprising two or more stacked all-solid-state secondary batteries as described in any one of claims 1 to 13.

15. A method for manufacturing a stacked all-solid-state secondary battery comprising: an anode layer; a solid electrolyte layer provided on each of the two sides of the anode layer; a cathode layer provided on each of the sides of the solid electrolyte layer facing the anode layer and the opposite side; an insulating member disposed to cover the side of the anode layer; a thin first conductive member protruding outwardly from the anode layer through the insulating member; and a thin second conductive member protruding outwardly from the cathode layer, wherein the first conductive member is formed integrally with the anode layer and the second conductive member is formed integrally with the cathode layer. A process for preparing a laminate in which, by folding the first conductive member and the second conductive member, the first conductive member and the second conductive member are insulated from each other, and the edge portion of the first conductive member and the edge portion of the second conductive member are provided to the outside of the cathode layer; and A method comprising a pressing process for pressing the above laminate in its stacking direction.

16. In Claim 15, The above laminate is: A thin first current collector protruding outward from the anode layer; and It further includes a first current collector protection member that protects the first current collector member, and A method for manufacturing an all-solid-state secondary battery, further comprising a removal process for removing the first current collection protection part after the above-mentioned pressurization process.

17. In Claim 16, A method for manufacturing an all-solid-state secondary battery in which the first current collection protection part is integrally formed on the side of the insulating member.

18. In Claim 17, A method for manufacturing an all-solid-state secondary battery, further comprising a process of forming a notch between the insulating member and the first current collector protection member to facilitate the removal of the first current collector protection member.

19. In Claim 18, A method for manufacturing an all-solid-state secondary battery in which the above notch is formed in a range of 5% or more and 99% or less of the thickness of the first current collection protection part.

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