JP2021005483A - Solid state battery - Google Patents

Abstract

To provide a solid state battery that is more preferably prevented from deteriorating in battery performance.SOLUTION: A solid state battery 500 is provided that includes a solid state battery laminate 500' with a positive electrode layer 10A, a negative electrode layer 10B, and a solid electrolyte layer 20 interposed between the positive electrode layer and the negative electrode layer, the solid state battery 500 comprises external terminals of a positive electrode terminal 30A and a negative electrode terminal 30B provided on the opposite side surfaces of the solid state battery laminate, respectively and the entire positive electrode terminal and the entire negative electrode terminal are covered with two metal layers 100A and 100B, respectively, and the two metal layer extend to reach at least three side surfaces of the solid state battery laminate in a cross-sectional view, and one metal layer overlaps at least a part of the other metal layer, and resin layers 40A, 40B, and 40 are interposed between the two metal layers.SELECTED DRAWING: Figure 1

Description

The present invention relates to a solid state battery.

Conventionally, secondary batteries capable of repeated charging and discharging have been used for various purposes. For example, a secondary battery may be used as a power source for electronic devices such as smartphones and notebook computers.

In a secondary battery, a liquid electrolyte is generally used as a medium for ion transfer that contributes to charging and discharging. That is, a so-called electrolytic solution is used in the secondary battery. However, in such a secondary battery, safety is generally required in terms of preventing leakage of the electrolytic solution. In addition, since the organic solvent used in the electrolytic solution is a flammable substance, safety is also required in that respect.

Therefore, research is underway on solid-state batteries that use solid electrolytes instead of electrolytes.

JP-A-2015-22009

Solid-state batteries need to be sure to take the necessary measures against moisture in the air. This is because if water enters the inside of the solid-state battery, a side reaction other than the battery reaction occurs in the solid-state battery component, which may cause deterioration of the battery characteristics.

The inventor of the present application has noticed that there are still problems to be overcome with the previously proposed solid-state battery, and has found the need to take measures for that purpose. Specifically, the inventor of the present application has found that there are the following problems.

The solid-state battery includes a solid-state battery laminate composed of a positive electrode layer, a negative electrode layer, and a solid electrolyte layer between them (see Patent Document 1). For example, as shown in FIG. 9, in the solid-state battery laminate 500', the positive electrode layer 10A, the solid electrolyte layer 20, and the negative electrode layer 10B are laminated in this order. The solid-state battery laminate 500'is provided with positive electrode terminals 30A and negative electrode terminals 30B which are external terminals in contact with two opposite side surfaces (that is, positive electrode side side surface 500'A and negative electrode side side surface 500'B). ing. Here, the positive electrode layer 10A and the negative electrode layer 10B extend so as to terminate at the positive electrode side side surface 500'A and the negative electrode side side surface 500'B, respectively.

The solid-state battery laminate 500', the positive electrode terminal 30A, and the negative electrode terminal 30B are covered with a metal layer 100 having a particularly high water vapor barrier property and a resin layer 40 having an insulating property and a cushioning property. The external electrode 300 is connected to the positive electrode terminal 30A and the negative electrode terminal 30B, respectively, and extends from the resin layer 40. When a metal material is used as the water vapor barrier layer in this way, it is necessary to interpose an insulating material (for example, a resin layer 40) between the external electrodes 300 of the positive electrode and the negative electrode and the metal layer 100, respectively, from the viewpoint of preventing short circuits. ..

In such a solid-state battery, moisture may enter the inside of the solid-state battery laminate via an insulating material located between the external electrode and the metal layer. In the configuration as described above, since the invasion route of water is short, the invaded water easily reaches the inside of the solid-state battery laminate, and an undesired side reaction may occur, which may cause deterioration of battery characteristics.

The present invention has been made in view of such a problem. That is, a main object of the present invention is to provide a solid-state battery in which the intrusion of water into the solid-state battery laminate is further reduced.

The inventor of the present application has attempted to solve the above-mentioned problems by dealing with it in a new direction, instead of dealing with it as an extension of the prior art. As a result, the invention of the solid-state battery which achieved the above-mentioned main purpose was reached.

The present invention provides a solid state battery. Such a solid battery includes a solid battery laminate having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer interposed between the positive electrode layer and the negative electrode layer, and is provided on opposite side surfaces of the solid battery laminate. The positive electrode terminal and the negative electrode terminal are provided with external terminals, and the entire positive electrode terminal and the entire negative electrode terminal are each covered with two metal layers, and the two metal layers are at least one of the side surfaces of the solid battery laminate in a cross-sectional view. Each extends over three sides, one metal layer overlaps at least a portion of the other metal layer, and a resin layer is interposed between the two metal layers.

The present invention also provides a method for manufacturing a solid-state battery. In one embodiment of such a solid-state battery manufacturing method, a metal layer is provided so as to cover the entire external terminal by a vapor deposition method or a sputtering method, and to cover at least three side surfaces of the solid-state battery laminate in a cross-sectional view. It includes a step of forming, a step of forming a resin layer so as to cover the metal layer by a wet method, and a step of peeling a part of the resin layer so as to form an external electrode connecting portion on the metal layer.

Another embodiment of the method for manufacturing a solid-state battery is a step of peeling a part of a resin layer from a laminate film including a metal layer and a resin layer to expose a part of the metal layer, an exposed portion of the metal layer. In the process of forming the laminated film into a bent shape so that is inside, insert the solid battery inside the bent shape of the laminated film so that the external terminal of the solid battery and the exposed part of the metal layer come into contact with each other. It includes a step of pressing the metal layer so as to join and adhere to the metal layer, and a step of peeling a part of the resin layer covering the metal layer so as to form an external electrode connecting portion on the metal layer.

The solid-state battery according to the present invention can further reduce the intrusion of water into the solid-state battery laminate. Therefore, it is a solid-state battery that more preferably prevents deterioration of battery performance.

More specifically, in the solid-state battery of the present invention, the entire external terminal is covered with a metal layer so that the metal layer covers at least three side surfaces of the solid-state battery laminate in a cross-sectional view. Due to the extension, the path for moisture to enter the inside of the solid-state battery laminate from the external terminal side can be made longer. Thereby, the invasion of water into the solid-state battery can be further reduced, and the occurrence of unwanted side reactions in the electrode layer can be reduced. Therefore, it is possible to more preferably prevent deterioration of the battery performance of the solid-state battery, and it is possible to improve the long-term reliability of the solid-state battery.

FIG. 1 is a cross-sectional view schematically showing an embodiment in which a positive electrode terminal and a negative electrode terminal are covered with two metal layers in the solid-state battery according to the present invention. FIG. 2 is a cross-sectional view schematically showing an embodiment in which an external electrode is formed in the solid-state battery according to the present invention. 3A and 3B are cross-sectional views schematically showing embodiments in the solid-state battery according to the present invention, in which the ratio of the area of the external electrode connecting portion to the area of the external terminal is different. FIG. 4 is a cross-sectional view schematically showing an embodiment having an external electrode connecting portion on the side surface having a normal in the electrode stacking direction of the solid-state battery laminate according to the present invention. FIG. 5 is a cross-sectional view schematically showing a method for manufacturing a solid-state battery according to an embodiment of the present invention. FIG. 6 is a cross-sectional view schematically showing an embodiment in which a metal layer extends so as to straddle a side surface of a solid-state battery according to the present invention provided with an external terminal manufactured by a laminating method. Is. FIG. 7 is a cross-sectional view schematically showing an embodiment in which a metal layer extends so as to straddle a side surface of a solid-state battery according to the present invention, which is manufactured by a laminating method and is not provided with an external terminal. is there. FIG. 8 is a cross-sectional view schematically showing an embodiment in which an external electrode is integrally connected to a substrate terminal in the solid-state battery according to the present invention. FIG. 9 is a cross-sectional view schematically showing a conventional solid-state battery.

Hereinafter, the "solid-state battery" of the present invention will be described in detail. Although the description will be given with reference to the drawings as necessary, the contents shown are merely schematic and exemplary for the purpose of understanding the present invention, and the appearance, dimensional ratio, and the like may differ from the actual product.

The "solid-state battery" as used in the present invention refers to a battery whose components are composed of solids in a broad sense, and in a narrow sense, its components (particularly preferably all components) are composed of solids. Refers to an all-solid-state battery. In one preferred embodiment, the solid-state battery in the present invention is a laminated solid-state battery in which the layers forming the battery building unit are laminated to each other, and preferably such layers are made of a sintered body. The "solid-state battery" includes not only a so-called "secondary battery" capable of repeating charging and discharging, but also a "primary battery" capable of only discharging. In one preferred embodiment of the invention, the "solid-state battery" is a secondary battery. The "secondary battery" is not overly bound by its name and may include, for example, a "storage device".

The "cross-sectional view" referred to in the present specification is a cross-sectional view along a surface formed by a thickness direction based on a stacking direction of electrode layers constituting a solid-state battery and a longitudinal direction in which the electrode layer extends in contact with an external terminal. It is based on morphology. In short, it is based on the cross-sectional shape of the solid-state battery shown in FIG.

[Basic configuration of solid-state battery]
The solid-state battery comprises a solid-state battery laminate having at least one battery building block composed of a positive electrode layer, a negative electrode layer, and a solid electrolyte layer interposed between them along the stacking direction.

In a solid-state battery, where each layer constituting the solid-state battery is formed by firing, a positive electrode layer, a negative electrode layer, a solid electrolyte layer, and the like form a sintered layer. Preferably, the positive electrode layer, the negative electrode layer and the solid electrolyte are each integrally fired, and therefore the battery building blocks form an integrally sintered body.

The positive electrode layer is an electrode layer including at least a positive electrode active material. The positive electrode layer may further include a solid electrolyte and / or a positive electrode current collector layer. In one preferred embodiment, the positive electrode layer is composed of a sintered body containing at least a positive electrode active material, solid electrolyte particles, and a positive electrode current collector layer. On the other hand, the negative electrode layer is an electrode layer including at least a negative electrode active material. The negative electrode layer may further include a solid electrolyte and / or a negative electrode current collector layer. In one preferred embodiment, the negative electrode layer is composed of a sintered body containing at least a negative electrode active material, solid electrolyte particles, and a negative electrode current collector layer.

The positive electrode active material and the negative electrode active material are substances involved in the transfer of electrons in a solid-state battery. Charging and discharging are performed by the movement (conduction) of ions between the positive electrode layer and the negative electrode layer via the solid electrolyte and the transfer of electrons between the positive electrode layer and the negative electrode layer via an external circuit. The positive electrode layer and the negative electrode layer are particularly preferably layers capable of occluding and releasing lithium ions. That is, it is preferable to use an all-solid-state secondary battery in which lithium ions move between the positive electrode layer and the negative electrode layer via the solid electrolyte to charge and discharge the battery.

(Positive electrode active material)
The positive electrode active material contained in the positive electrode layer is, for example, a lithium-containing compound. The type of the lithium compound is not particularly limited, and is, for example, a lithium transition metal composite oxide and a lithium transition metal phosphoric acid compound. Lithium transition metal composite oxide is a general term for oxides containing lithium and one or more types of transition metal elements as constituent elements, and lithium transition metal phosphoric acid compounds are one or more types of lithium. It is a general term for phosphoric acid compounds containing the transition metal element of. The type of the transition metal element is not particularly limited, and examples thereof include cobalt (Co), nickel (Ni), manganese (Mn), and iron (Fe).

The lithium transition metal composite oxide is, for example, a compound represented by Li _x M1O ₂ and Li _y M2O ₄ , respectively. Lithium transition metal phosphate compound, for _example, a compound represented by Li z M3PO _4, and the like. However, each of M1, M2 and M3 is one kind or two or more kinds of transition metal elements. The respective values of x, y and z are arbitrary.

Specifically, the lithium transition metal composite oxide is, for example, LiCoO ₂ , LiNiO ₂ , LiVO ₂ , LiCrO ₂ and LiMn ₂ O ₄ . Further, the lithium transition metal phosphoric acid compound is, for example, LiFePO ₄ and LiCoPO ₄ .

(Negative electrode active material)
Examples of the negative electrode active material contained in the negative electrode layer include carbon materials, metal-based materials, lithium alloys and lithium-containing compounds.

Specifically, the carbon material is, for example, graphite, graphitizable carbon, non-graphitizable carbon, mesocarbon microbeads (MCMB), highly oriented graphite (HOPG) and the like.

The metal-based material is a general term for materials containing one or more of metal elements and metalloid elements capable of forming an alloy with lithium as constituent elements. This metallic material may be a simple substance, an alloy, or a compound. Since the purity of the simple substance described here is not necessarily limited to 100%, the simple substance may contain a trace amount of impurities.

Metallic elements and semi-metal elements include, for example, silicon (Si), tin (Sn), aluminum (Al), indium (In), magnesium (Mg), boron (B), gallium (Ga), germanium (Ge). , Lead (Pb), Bismus (Bi), Cadmium (Cd), Titanium (Ti), Chromium (Cr), Iron (Fe), Niob (Nb), Molybdenum (Mo), Silver (Ag), Zinc (Zn) , Hafnium (Hf), zirconium (Zr), indium (Y), palladium (Pd), platinum (Pt) and the like.

Specifically, the metal-based materials include, for example, Si, Sn, SiB ₄ , TiSi ₂ , SiC, Si ₃ N ₄ , SiO _v (0 <v ≦ 2), LiSiO, SnO _w (0 <w ≦ 2). , SnSiO ₃ , LiSnO, Mg ₂ Sn, and the like.

The lithium-containing compound is, for example, a lithium transition metal composite oxide. The definition of the lithium transition metal composite oxide is as described above. Specifically, the lithium transition metal double oxide is, for example, Li ₃ V ₂ (PO ₄ ) _3, Li ₃ Fe ₂ (PO ₄ ) _3, Li ₄ Ti ₅ O _{12, and the} like.

The positive electrode layer and / or the negative electrode layer may contain an electron conductive material. Examples of the electron conductive material contained in the positive electrode layer and / or the negative electrode layer include a carbon material and a metal material. Specifically, the carbon material is, for example, graphite and carbon nanotubes. The metal material is, for example, copper (Cu), magnesium (Mg), titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge). , Indium (In), gold (Au), platinum (Pt), silver (Ag), palladium (Pd), and the like, and two or more alloys thereof may be used.

Further, the positive electrode layer and / or the negative electrode layer may contain a binder. The binder is, for example, any one or more of synthetic rubber and polymer materials. Specifically, the synthetic rubber is, for example, styrene-butadiene rubber, fluorine-based rubber, ethylene propylene diene, or the like. As the polymer material, for example, at least one selected from the group consisting of polyvinylidene fluoride, polyimide and acrylic resin can be mentioned.

Further, the positive electrode layer and / or the negative electrode layer may contain a sintering aid. As the sintering aid, at least one selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, boron oxide, silicon oxide, bismuth oxide and phosphorus oxide can be mentioned.

The thicknesses of the positive electrode layer and the negative electrode layer are not particularly limited, and may be, for example, 2 μm or more and 100 μm or less, particularly 5 μm or more and 50 μm or less, respectively.

(Solid electrolyte)
The solid electrolyte is a material capable of conducting lithium ions. In particular, the solid electrolyte that forms a battery constituent unit in a solid-state battery forms a layer in which lithium ions can be conducted between the positive electrode layer and the negative electrode layer. The solid electrolyte may be provided at least between the positive electrode layer and the negative electrode layer. That is, the solid electrolyte may also be present around the positive electrode layer and / or the negative electrode layer so as to protrude from between the positive electrode layer and the negative electrode layer. Specific solid electrolytes include, for example, any one or more of crystalline solid electrolytes and glass-ceramic solid electrolytes.

The crystalline solid electrolyte is a crystalline electrolyte. Specifically, the crystalline solid electrolyte is, for example, an inorganic material and a polymer material, and the inorganic material is, for example, a sulfide and an oxide. Sulfide, for _{example, Li 2 S-P 2 S} 5, Li 2 S-SiS 2 -Li 3 PO 4, Li 7 P 3 S 11, Li 3.25 Ge 0.25 P 0.75 S and _{Li 10} For example, GeP ₂ S ₁₂ . Oxides, for _{example, Li x M y (PO 4} ) 3 (1 ≦ x ≦ 2,1 ≦ y ≦ 2, M is at least one selected from the group consisting of Ti, Ge, Al, Ga and Zr) , Li ₇ La ₃ Zr ₂ O ₁₂ , Li _6.75 La ₃ Zr _1.75 Nb _0.25 O ₁₂ , Li ₆ BaLa ₂ Ta ₂ O ₁₂ , Li _{1 + x} Al _x Ti _2-x (PO ₄ ) ₃ , La _{2 / 3- x} Li _3x TiO ₃ , Li _1.2 Al _0.2 Ti _1.8 (PO ₄ ) _3, La _0.55 Li _0.35 TiO ₃ and Li ₇ La ₃ Zr ₂ O ₁₂ etc. is there. The polymeric material is, for example, polyethylene oxide (PEO).

The glass-ceramic solid electrolyte is an electrolyte in which amorphous and crystalline are mixed. This glass-ceramic solid electrolyte is, for example, an oxide containing lithium (Li), silicon (Si) and boron (B) as constituent elements, and more specifically, lithium oxide (Li ₂ O) and oxidation. It contains silicon (SiO ₂ ), boron oxide (B ₂ O ₃ ) and the like. The ratio of the content of lithium oxide to the total content of lithium oxide, silicon oxide and boron oxide is not particularly limited, but is, for example, 40 mol% or more and 73 mol% or less. The ratio of the content of silicon oxide to the total content of lithium oxide, silicon oxide and boron oxide is not particularly limited, but is, for example, 8 mol% or more and 40 mol% or less. The ratio of the content of boron oxide to the total content of lithium oxide, silicon oxide and boron oxide is not particularly limited, but is, for example, 10 mol% or more and 50 mol% or less. In order to measure the respective contents of lithium oxide, silicon oxide and boron oxide, for example, inductively coupled plasma emission spectroscopy (ICP-AES) or the like is used to analyze a glass-ceramic solid electrolyte.

The solid electrolyte layer may contain a binder and / or a sintering aid. The binder and / or sintering aid contained in the solid electrolyte layer may be selected from, for example, materials similar to the binder and / or sintering aid that may be contained in the positive electrode layer and / or the negative electrode layer. Good.

The thickness of the solid electrolyte layer is not particularly limited, and may be, for example, 1 μm or more and 15 μm or less, particularly 1 μm or more and 5 μm or less.

(Positive current collector layer / Negative electrode current collector layer)
As the positive electrode current collector constituting the positive electrode current collector layer and the negative electrode current collector material constituting the negative electrode current collector layer, it is preferable to use a material having a high conductivity, for example, carbon material, silver, palladium, gold, platinum, aluminum, etc. It is preferable to use at least one selected from the group consisting of copper and nickel. Each of the positive electrode current collector layer and the negative electrode current collector layer has an electrical connection portion for electrically connecting to the outside, and may be configured to be electrically connectable to the terminal. The positive electrode current collector layer and the negative electrode current collector layer may each have a foil form, but from the viewpoint of improving electron conductivity and reducing manufacturing cost by integral sintering, it is preferable to have an integral sintering form. When the positive electrode current collector layer and the negative electrode current collector layer have the form of a sintered body, they may be composed of, for example, a sintered body containing an electron conductive material, a binder and / or a sintering aid. The electron conductive material contained in the positive electrode current collector layer and the negative electrode current collector layer may be selected from, for example, the same materials as the electron conductive material that can be contained in the positive electrode layer and / or the negative electrode layer. The binder and / or sintering aid contained in the positive electrode current collector layer and the negative electrode current collector layer is the same as the binder and / or sintering aid which may be contained in the positive electrode layer and / or the negative electrode layer, for example. It may be selected from materials.

The thicknesses of the positive electrode current collector layer and the negative electrode current collector layer are not particularly limited, and may be, for example, 1 μm or more and 10 μm or less, particularly 1 μm or more and 5 μm or less, respectively.

(Inorganic layer)
The inorganic layer is made of an inorganic material and has an insulating property. Although not particularly limited, the inorganic layer may be made of, for example, a glass material, a ceramic material, or the like. As such an inorganic layer, for example, a glass material may be selected. The glass material is not particularly limited, but the glass material is soda lime glass, potash glass, borate glass, borosilicate glass, barium borate glass, subsalt borate glass, barium borate glass, etc. At least one selected from the group consisting of bismuth borosilicate glass, bismuth zinc borate glass, bismuth silicate glass, phosphate glass, aluminophosphate glass, and phosphate subsalt glass. Can be mentioned. Further, although not particularly limited, the ceramic material is aluminum oxide (Al ₂ O ₃ ), boron nitride (BN), silicon dioxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), zirconium oxide (ZrO). ₂ ), at least one selected from the group consisting of aluminum nitride (AlN), silicon carbide (SiC) and barium titanate (BaTIO ₃ ) can be mentioned.

(Metal layer)
The metal layer is made of a metal material and refers to a layer that is substantially impermeable to moisture and / or gas. Specifically, it refers to a layer having a water vapor permeability of 10 ^-3 g / m ² / day or less. By way of example only, such metal layers include, for example, at least one selected from the group consisting of titanium, tin, gold, platinum, aluminum, copper, stainless steel, nickel and nickel plated steel sheets and alloys thereof. It may consist of. As defined in "JIS G 0203 Steel Terminology", stainless steel is an alloy steel containing chromium or chromium and nickel, and generally has a chromium content of about 10.5% or more of the total. Refers to steel. Examples of such stainless steels include martensite-based stainless steels, ferrite-based stainless steels, austenitic stainless steels, austenitic-ferritic stainless steels, and precipitation-hardened stainless steels.

(Resin layer)
The resin layer is made of a resin material and has at least an insulating property. In other words, it is a layer made of an insulating resin. The resin layer preferably further has cushioning properties, water vapor barrier properties, and the like. The resin layer is used to ensure insulation between the electrodes in the solid-state battery and / or insulation from the outside of the solid-state battery, but may have other effects. For example, when the resin layer covers the outermost side of the solid-state battery, it may be used as a protective layer that physically and / or chemically protects the solid-state battery. Further, when the resin layer is arranged inside the metal layer, a smooth surface as a base of the metal layer may be provided. Although not particularly limited, such a resin layer may contain, for example, at least one selected from the group consisting of acrylic, epoxy, nylon, polyimide, polyamide, polypropylene, polyethylene, polyester and liquid crystal polymers.

(External terminal)
The solid-state battery is generally provided with an external terminal. In particular, positive and negative electrode terminals are provided on the side surface of the solid-state battery so as to form a pair. More specifically, the terminal on the positive electrode side connected to the positive electrode layer and the terminal on the negative electrode side connected to the negative electrode layer are provided so as to form a pair. It is preferable to use a material having a high conductivity for the external terminal. The material of the external terminal is not particularly limited, and at least one selected from the group consisting of silver, gold, platinum, aluminum, copper, tin, nickel, and stainless steel can be mentioned.

(External electrode)
The external electrode can be formed so as to be conductive with the external terminal of the solid-state battery, and is a conductor for exchanging current with the outside. The external electrode may be formed in any form as long as it is conductive with the external terminal. From the viewpoint of further preventing the intrusion of moisture into the solid-state battery laminate, it is preferable that the external electrode is conducted with the external terminal via the metal layer. It is preferable to use a material having a high conductivity for the external electrode. As the material of the external electrode, the same material as that of the external terminal may be used.

[Characteristics of the solid-state battery of the present invention]
The solid-state battery of the present invention comprises a solid-state battery laminate having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer interposed between the positive electrode layer and the negative electrode layer, and is provided on opposite side surfaces of the solid-state battery laminate. It is a solid-state battery provided with an external terminal of a positive electrode terminal and an external terminal of the negative electrode terminal, and is characterized in the shape of a metal layer covering the external terminal.

More specifically, the entire positive electrode terminal and the entire negative electrode terminal are each covered with two metal layers, and the two metal layers cover at least three side surfaces of the solid-state battery laminate in cross-sectional view. Each is extended as. Further, one metal layer overlaps at least a part of the other metal layer, and a resin layer is interposed between the two metal layers. With such a configuration, it is possible to lengthen the path for moisture to enter the inside of the solid-state battery laminate from the external terminal side covered with the metal layer. Therefore, it is possible to further reduce the intrusion of water into the solid-state battery.

Here, the "cross-sectional view" is a cross section of a solid-state battery along a surface formed by a direction in which the electrode layer extends in contact with an external terminal (that is, a longitudinal direction) and an electrode stacking direction (that is, a thickness direction). Refers to the form of. As an example, the "side surface of the solid-state battery laminate" is, in cross-sectional view, from two opposing side surfaces of the solid-state battery laminate provided with external terminals and two opposing side surfaces having normals in the electrode stacking direction. The metal layer extends over at least three of these four sides.

In other words, in the cross-sectional view of the solid-state battery, the external terminals are covered with a substantially U-shaped metal layer. Here, the "substantially U-shaped" means that the shape of the cross section of the solid-state battery along the surface formed by the longitudinal direction and the thickness direction is substantially U-shaped.

In the exemplary embodiment shown in FIG. 1, the positive electrode layer 10A, the solid electrolyte layer 20, and the negative electrode layer 10B are provided in this order in the cross-sectional view of the solid-state battery laminate 500'. The solid-state battery laminate 500'is provided with a positive electrode terminal 30A and a negative electrode terminal 30B so as to be in contact with two opposite side surfaces (that is, a positive electrode side side surface 500'A and a negative electrode side side surface 500'B). The positive electrode layer 10A and the negative electrode layer 10B extend so as to terminate at the positive electrode side side surface 500'A and the negative electrode side side surface 500'B, respectively. Here, the positive electrode layer 10A and the negative electrode layer 10B are electrically connected to the positive electrode terminal 30A and the negative electrode terminal 30B, respectively.

The positive electrode terminal 30A and the negative electrode terminal 30B are covered with metal layers 100A and 100B, respectively. The metal layers 100A and 100B have four side surfaces of the solid-state battery laminate 500'(that is, positive electrode side side surface 500'A, negative electrode side side surface 500'B, and side surfaces 500'C and 500'D having normals in the electrode stacking direction. ), Each extends over three aspects. More specifically, the metal layer 100A extends so as to extend to the positive electrode side side surface 500'A and the side surfaces 500'C and 500'D having normals in the electrode stacking direction. Further, the metal layer 100B extends so as to extend to the negative electrode side side surface 500'B and the side surfaces 500'C and 500'D having a normal in the electrode stacking direction. Here, the metal layer 100B overlaps a part of the metal layer 100A, and the resin layer 40A is interposed between the metal layers 100A and 100B.

In the present embodiment, moisture cannot enter the inside of the solid-state battery laminate 500'via the metal layers 100A and 100B. That is, water cannot penetrate into the solid-state battery laminate 500'from the positive electrode side side surface 500'A and the negative electrode side side surface 500'B covered with the metal layers 100A and 100B, and the water penetration path can be lengthened. ..

More specifically, since moisture cannot enter the inside of the solid-state battery laminate 500'through the metal layers 100A and 100B, it is passed through other components (for example, resin layers 40, 40A and / or 40B). Invade. Here, focusing on the positive electrode side in FIG. 1, moisture can enter through the resin layers 40, 40A and / or 40B which are constituent parts other than the metal layer 100A, but the position and the solid in contact with the outside in such a constituent portion. The distance from the position in contact with the battery laminate (that is, the moisture intrusion route) is long. Further, when the component has a water vapor barrier property, the water molecule has a movement resistance to the component, and the substantially water invasion route becomes longer.

Thereby, the occurrence of unwanted side reactions in the electrode layer due to the intrusion of water can be reduced. Therefore, it is possible to more preferably prevent deterioration of the battery performance of the solid-state battery, and it is possible to further improve the long-term reliability of the solid-state battery.

Further, in the above-described configuration, when the metal layers 100A and 100B are electrically connected to the positive electrode terminals 30A and the negative electrode terminals 30B by interposing the resin layer 40A between the metal layers 100A and 100B, a short circuit occurs. It can be prevented from doing so.

The two metal layers extend so as to straddle the side surfaces (that is, the positive electrode side side surface 500'A and the negative electrode side side surface 500'B) where the external terminals (that is, the positive electrode terminal 30A and the negative electrode terminal 30B) are provided. It may be present (see FIG. 1). Alternatively, they may extend so as to straddle the side surfaces (that is, the side surfaces 500'C and 500'D having normals in the electrode stacking direction) where the external terminals are not provided (see FIG. 7). From the viewpoint of lengthening the moisture intrusion path into the solid-state battery laminate, it is preferable that each of the two metal layers extends so as to straddle the side surface where the external terminal is provided.

In the embodiment in which the two metal layers extend so as to straddle the side surface on which the external terminal is provided, the metal layer (for example, the metal layer 100A) covering one of the external terminals (for example, the positive electrode terminal 30A) is covered. ) Is preferably extended to the vicinity thereof so as not to come into contact with the other external terminal (for example, the negative electrode terminal 30B) (see FIG. 1). Specifically, it is preferable that the ratio (L1 / L2) of the longitudinal dimension L1 of the metal layer to the longitudinal dimension L2 of the solid-state battery laminate is 0.5 or more and 0.8 or less. Here, it is more preferable that the ratio is 0.5 or more and 0.8 or less in both the metal layers 100A and 100B. When such a ratio is 0.5 or more, the moisture intrusion route into the solid-state battery laminate can be made longer. Further, when such a ratio is 0.8 or less, a short circuit due to contact between the electrodes of the solid-state battery can be particularly prevented.

In the solid-state battery 500 according to the present invention, the component portion that substantially determines the distance of the moisture intrusion path can be the resin layer 40A interposed between the two metal layers 100A and 100B (see FIG. 1). In order to lengthen the moisture intrusion path through the resin layer 40A, it is preferable to increase the longitudinal dimension of the portion where the metal layers 100A and 100B overlap. Here, the longitudinal dimension of the portion where the metal layers 100A and 100B overlap is preferably 2 mm or more, for example, 10 mm or more.

In one embodiment, at least part of the metal layer is covered with a resin layer. In the exemplary embodiment shown in FIG. 1, the metal layers 100A and 100B are covered with the resin layers 40A and 40B, respectively. Since the resin layer has an insulating property, it is possible to prevent a short circuit due to contact between the electrodes by covering the metal layer. Further, when the resin layer has cushioning property, chemical resistance and the like, it can function as a protective layer that physically / chemically protects the solid-state battery.

In one embodiment, the metal layer is in contact with the external terminals. In the exemplary embodiment shown in FIG. 2, the metal layer 100A and the metal layer 100B are in contact with the positive electrode terminal 30A and the negative electrode terminal 30B, respectively. The metal layer 100A and the metal layer 100B may be in direct contact with the positive electrode terminal 30A and the negative electrode terminal 30B, respectively. When the solid-state battery laminate 500'is covered with the resin layer 40, the metal layer 100A and the metal layer 100B are in contact with the positive electrode terminal 30A and the negative electrode terminal 30B, respectively, through the gaps provided in the resin layer 40, respectively. Good.

In the above embodiment, the metal layer 100 has an external electrode connecting portion 110. The external electrode connecting portion 110 may be a portion where the metal layer 100 is exposed to the outside, or may be a portion made of a metal material integrated with the metal layer 100. The external electrode connecting portion 110 may be provided at any location as long as the metal layer 100 extends. Since the metal layer 100 has conductivity, it can be used as an electrode extraction portion by contacting the external terminal 30 to conduct the metal layer 100 and further contacting the external electrode 300 at the external electrode connecting portion 110.

In one embodiment in which the metal layer is covered with a resin layer, a part of the metal layer is exposed from the resin layer, and the exposed portion forms an external electrode connecting portion. In the exemplary embodiment shown in FIG. 2, a part of the metal layer 100A is exposed from the resin layer 40A to form a positive electrode side external electrode connecting portion 110A, and a part of the metal layer 100B is a resin layer 40B. It is exposed from and forms the negative electrode side external electrode connecting portion 110B. With such a configuration, the external electrode 300 can be taken out at a desired size and position while preventing damage and short circuit from occurring in the metal layer due to the resin layer.

In one embodiment, the ratio (S1 / S2) of the area S1 of the external electrode connecting portion 110 to the area S2 of the external terminal 30 is 0.1 or more and 1.0 or less (see FIGS. 3A and 3B). Here, the "area" refers to the area of the external terminal or the external electrode connecting portion on the same surface as the surface where the external terminal and the external electrode connecting portion contact. When the area ratio is 0.1 or more, the electron flow in the electrode layer in the width direction can be made more uniform. Further, when the area ratio is 1.0 or less, the size of the electrode extraction portion can be suppressed, and the solid-state battery can be mounted more compactly. Preferably, the area ratio is 0.3 or more and 0.8 or less.

In one embodiment, the solid-state battery has an external electrode connecting portion 110 on the side surface side having a normal in the electrode stacking direction of the solid-state battery laminate (see FIG. 4). When a solid-state battery is surface-mounted on a substrate, the side surface side having a normal in the electrode lamination direction of the solid-state battery laminate can be generally the side facing the substrate. With the above-described configuration, the side surface side having a normal in the electrode stacking direction of the solid-state battery laminate can be the mounting surface side, and the solid-state battery can be mounted more compactly.

The structure of the solid-state battery of the present specification is obtained by cutting out a cross-sectional view direction cross section with an ion milling device (Hitachi High-Tech Co., Ltd. model number IM4000PLUS) and using a scanning electron microscope (SEM) (Hitachi High-Tech Co., Ltd. model number SU-8040). It may be what is observed from the image. Further, as referred to in the present specification, the longitudinal dimension L1 on the side surface side of the metal layer and the longitudinal dimension L2 of the solid-state battery laminate, the longitudinal dimension of the portion where the two metal layers overlap, and The area S1 of the external electrode connecting portion and the area S2 of the external terminal may refer to the dimensions measured from the image acquired by the method described above.

The solid-state battery according to the present invention is a laminated solid-state battery in which each layer constituting the solid-state battery laminate is laminated, and is subjected to a printing method such as a screen printing method, a green sheet method using a green sheet, or a composite method thereof. Can be manufactured. Therefore, each layer constituting the solid-state battery laminate is made of a sintered body. Preferably, the positive electrode layer, the negative electrode layer and the solid electrolyte layer are integrally sintered with each other. That is, it can be said that the solid-state battery laminate is a fired integrated product. External terminals can be adhered to such a solid-state battery laminate using a conductive adhesive or the like. In a cross-sectional view of such a solid-state battery, a metal layer is formed by a vapor deposition method, a laminating method, or the like so as to cover the external terminals and to cover at least three side surfaces of the solid-state battery laminate.

[Manufacturing method of solid-state battery]
As described above, the solid-state battery of the present invention can be produced from a solid-state battery laminate by a printing method such as a screen printing method, a green sheet method using a green sheet, or a composite method thereof. Further, the solid-state battery laminate and the metal layer covering the external terminals can be formed by a vapor deposition method, a laminating method, or the like. Hereinafter, embodiments for producing a solid-state battery according to the present invention will be described in detail for the purpose of understanding the present invention, but the present invention is not limited to this method.

(Forming process of solid-state battery laminated precursor)
In this step, several kinds of pastes such as a positive electrode layer paste, a negative electrode layer paste, a solid electrolyte layer paste, a current collector layer paste, and an inorganic layer paste are used as inks. That is, a paste having a predetermined structure is formed on the support substrate by applying the paste by a printing method.

At the time of printing, a solid-state battery lamination precursor corresponding to a predetermined solid-state battery structure can be formed on the substrate by sequentially laminating the printing layers having a predetermined thickness and pattern shape. The type of the pattern forming method is not particularly limited as long as it is a method capable of forming a predetermined pattern, and is, for example, any one or two or more of a screen printing method and a gravure printing method.

The paste is a predetermined constituent material of each layer appropriately selected from the group consisting of a positive electrode active material, a negative electrode active material, an electron conductive material, a solid electrolyte material, a current collecting layer material, an inorganic material, a binder and a sintering aid. And an organic vehicle in which an organic material is dissolved in a solvent are wet-mixed with each other. The positive electrode layer paste includes, for example, a positive electrode active material, an electron conductive material, a solid electrolyte material, a binder, a sintering aid, an organic material and a solvent. The paste for the negative electrode layer includes, for example, a negative electrode active material, an electron conductive material, a solid electrolyte material, a binder, a sintering aid, an organic material and a solvent. The solid electrolyte layer paste includes, for example, solid electrolyte materials, binders, sintering aids, organic materials and solvents. The positive electrode current collector layer paste and the negative electrode current collector layer paste include an electron conductive material, a binder, a sintering aid, an organic material and a solvent. The paste for the inorganic layer includes, for example, an inorganic material, a binder, an organic material and a solvent.

The organic material contained in the paste is not particularly limited, but at least one polymer material selected from the group consisting of polyvinyl acetal resin, cellulose resin, polyacrylic resin, polyurethane resin, polyvinyl acetate resin, polyvinyl alcohol resin and the like can be used. Can be used. The type of the solvent is not particularly limited, and is, for example, any one or more of organic solvents such as butyl acetate, N-methyl-pyrrolidone, toluene, terpineol and N-methyl-pyrrolidone.

In the wet mixing, a medium can be used, and specifically, a ball mill method, a viscomill method, or the like can be used. On the other hand, a wet mixing method that does not use media may be used, and a sand mill method, a high-pressure homogenizer method, a kneader dispersion method, or the like can be used.

The support substrate is not particularly limited as long as it is a support capable of supporting each paste layer, and is, for example, a release film having a release treatment on one surface. Specifically, a substrate made of a polymer material such as polyethylene terephthalate can be used. When each paste layer is subjected to the firing step while being held on the substrate, a substrate that exhibits heat resistance to the firing temperature may be used.

At the time of printing, by sequentially laminating the printing layers with a predetermined thickness and pattern shape, an unfired laminate corresponding to the structure of a predetermined solid-state battery can be formed on the base material. When forming each print layer, a drying process is performed. In the drying process, the solvent evaporates from the unfired laminate. After forming the unfired laminate, the unfired laminate may be peeled off from the base material and subjected to a firing step, or the unfired laminate may be subjected to a firing step while being held on the supporting substrate. May be good.

(Baking process)
In the firing step, the solid-state battery laminated precursor is subjected to firing. Although it is merely an example, firing is performed in a nitrogen gas atmosphere containing oxygen gas or in the atmosphere, for example, at 500 ° C., and then in a nitrogen gas atmosphere or in the atmosphere, for example, 550 ° C. or higher and 5000 ° C. or lower. It is carried out by heating with. The firing may be performed while pressurizing the solid-state battery lamination precursor in the lamination direction (in some cases, the lamination direction and the direction perpendicular to the lamination direction).

By undergoing such firing, a solid-state battery laminate is formed.

(External terminal forming process)
For the external terminals, the positive electrode terminals are adhered to the solid-state battery laminate using a conductive adhesive or the like, and the negative electrode terminals are adhered to the solid-state battery laminate using a conductive adhesive or the like. As a result, the solid-state battery is formed by attaching each of the positive electrode terminal and the negative electrode terminal to the solid-state battery laminate.

[About the production of the characteristic portion in the present invention]
The metal layer in the solid-state battery of the present invention is formed by any method as long as it covers the external terminals and extends so as to extend to at least three side surfaces of the solid-state battery laminate in cross-sectional view. May be done. As an example, a metal material may be vapor-deposited by masking a portion other than the portion where the metal layer is formed. Further, it may be formed by inserting a solid-state battery laminate into a laminate film containing a metal layer formed in a bent shape.

Hereinafter, a method for producing a solid-state battery by a vapor deposition method and a laminating method (particularly, a method for forming a metal layer and a resin layer) will be specifically described.

(Manufacturing method of solid-state battery by vapor deposition method)
First, the solid-state battery laminate is dipped in a resin (for example, polyimide) to form a resin layer 40 on the surface of the solid-state battery other than at least a part of each of the positive electrode terminal 30A and the negative electrode terminal 30B (see FIG. 1). .. Next, the desired position of the solid-state battery laminate is masked, and a metal material (for example, aluminum) is vapor-deposited by vacuum vapor deposition to form a metal layer 100A so as to cover the positive electrode terminal 30A. At this time, the metal layer 100A is formed so as to extend to the vicinity thereof so as not to come into contact with the negative electrode terminal 30B (for example, the end surface of the metal layer 100A with respect to the longitudinal dimension L2 of the solid-state battery laminate 500'). The ratio of the longitudinal dimension L1 on the side is 0.5 or more and 0.8 or less). Further, by dipping the metal layer 100A into the resin, the resin layer 40A is formed so as to cover the metal layer 100A. Finally, by irradiating the desired position of the resin layer 40A with a laser, the metal layer 100A is exposed and the external electrode connecting portion 110A is formed.

Similar to the positive electrode side, the metal layer 100B is formed so as to cover the negative electrode terminal 30B by masking a desired position of the solid-state battery laminate and depositing a metal material by vacuum vapor deposition. At this time, the metal layer 100B is formed so as to extend to the vicinity thereof so as not to come into contact with the positive electrode terminal 30A (for example, the end side surface of the metal layer 100B with respect to the longitudinal dimension L2 of the solid-state battery laminate 500'). Form so that the ratio of the longitudinal dimensions of the side is 0.5 or more and 0.8 or less). Further, by dipping the metal layer 100B into the resin, the resin layer 40B is formed so as to cover the metal layer 100B. Finally, by irradiating the desired position of the resin layer 40B with a laser, the metal layer 100B is exposed and the external electrode connecting portion 110B is formed.

The above-mentioned metal layer may be formed by another vacuum process such as a sputtering method. Further, the resin layer may be formed by another wet method such as spray coating.

(Manufacturing method of solid-state battery by laminating method)
First, a laminated film 200A laminated in the order of resin layer 40A / metal layer 100A / resin layer 40 is prepared, and the desired position of the resin layer 40 is peeled off to expose the metal layer 100A (see FIG. 5). After that, the laminate film 200A is formed in a bent shape (for example, a substantially U shape) so that the resin layer 40 is located inside. At this time, the inner edge of the bent shape of the laminated film 200A is formed so that it can be fitted to the outer edges of the three side surfaces of the solid-state battery laminate, and the exposed portion of the metal layer 100A is formed inside the bent shape. To do. Next, the solid-state battery laminate is inserted into the bent shape of the laminate film 200A so that the positive electrode terminal 30A attached to the solid-state battery laminate 500'and the exposed portion of the metal layer 100A are in contact with each other, and they are joined and joined. Press so that they are in close contact. Further, by irradiating the desired position of the resin layer 40A with a laser, the metal layer 100A is exposed and the external electrode connecting portion 110A is formed.

Similar to the positive electrode side, a laminated film laminated in the order of resin layer / metal layer / resin layer is prepared, and the desired position of the resin layer is peeled off to expose the metal layer (not shown). Then, the laminated film is formed in a bent shape so that one of the resin layers is located inside. At this time, the inner edge of the bent shape in the laminated film can be fitted to the three side surfaces of the solid-state battery laminate and the outer edge of the laminated film 200A, and the exposed portion of the metal layer is inside the bent shape. Form as. Next, the solid-state battery is inserted into the bent shape of the laminated film so that the negative electrode terminal attached to the solid-state battery laminate and the exposed portion of the metal layer are in contact with each other, and the solid-state batteries are pressed so as to be joined and brought into close contact with each other. Further, by irradiating a desired position of the resin layer with a laser, the metal layer is exposed and an external electrode connection portion is formed.

In the above-mentioned laminating method, the metal layer 100 may be formed so as to straddle the side surface on which the external terminal 30 is provided (see FIG. 6). Alternatively, it may be formed so as to straddle a side surface on which the external terminal 30 is not provided (see FIG. 7).

By the thin-film deposition method or the laminating method as described above, a solid-state battery is formed in which a metal layer covers the external terminals and extends over at least three side surfaces of the solid-state battery laminate in cross-sectional view. ..

(External electrode forming process)
The external electrode 300 may be formed by applying a conductive paste (for example, a resin paste containing silver) to the external electrode connecting portion 110 by a wet method and then curing the external electrode 300 (see FIG. 2). Further, it may be connected to a terminal having an external electrode 300 (for example, a substrate terminal 400) (see FIG. 8).

Although the embodiments of the present invention have been described above, they merely exemplify typical examples. Therefore, those skilled in the art will easily understand that the present invention is not limited to this, and various aspects can be considered without changing the gist of the present invention.

For example, in the above description, for example, the solid-state battery exemplified in FIG. 1 and the like has been mainly described, but the present invention is not necessarily limited to this. The present invention has a solid-state battery laminate having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer, and has external terminals provided on opposite side surfaces of the solid-state battery laminate, and the metal layer serves as an external terminal in a cross-sectional view. Any one that covers and extends over at least three sides of the solid-state battery laminate can be similarly applied.

The solid-state battery of the present invention can be used in various fields where storage is expected. Although merely an example, the solid-state battery of the present invention is used in the fields of electricity, information, and communication (for example, mobile phones, smartphones, laptop computers and digital cameras, activity meters, arm computers, electronic papers) in which mobile devices and the like are used. Mobile device fields such as), home / small industrial applications (eg, power tools, golf carts, home / nursing / industrial robot fields), large industrial applications (eg, forklifts, elevators, bay port cranes) , Transportation system field (for example, hybrid car, electric car, bus, train, electric assist bicycle, electric motorcycle, etc.), power system application (for example, various power generation, road conditioner, smart grid, general household installation type power storage system, etc. Fields), medical applications (medical equipment fields such as earphone hearing aids), pharmaceutical applications (fields such as dose management systems), and IoT fields, space / deep sea applications (for example, space explorers, submersible research vessels, etc.) ) Etc. can be used.

10 Electrode layer 10A Positive electrode layer 10B Negative electrode layer 20 Solid electrolyte layer 30 External terminal 30A Positive electrode terminal 30B Negative electrode terminal 40 Resin layer 40A Positive electrode side resin layer 40B Negative electrode side resin layer 100 Metal layer 100A Positive electrode side metal layer 100B Negative electrode side metal layer 110 External Electrode connection part 110A Positive electrode side external electrode connection part 110B Negative electrode side external electrode connection part 200 Laminate film 200A Positive electrode side laminate film 200B Negative electrode side laminate film 300 External electrode 400 Substrate terminal 500'A Solid battery laminate 500'A Positive electrode side side surface 500' B Negative electrode side side surface 500'C Side surface having a normal line in the electrode stacking direction 500'D Side surface having a normal line in the electrode stacking direction 500 Solid battery

Claims (11)

It ’s a solid-state battery,
It comprises a solid-state battery laminate comprising a positive electrode layer, a negative electrode layer, and a solid electrolyte layer interposed between the positive electrode layer and the negative electrode layer.
External terminals of the positive electrode terminal and the negative electrode terminal provided on the opposite side surfaces of the solid-state battery laminate are provided.
The entire positive electrode terminal and the entire negative electrode terminal are each covered with two metal layers.
The two metal layers extend so as to extend to at least three side surfaces of the solid-state battery laminate in cross-sectional view.
A solid-state battery in which one metal layer overlaps at least a part of the other metal layer, and a resin layer is interposed between the two metal layers. The solid-state battery according to claim 1, wherein the two metal layers extend so as to straddle the side surface on which the external terminal is provided. The solid-state battery according to claim 2, wherein the ratio of the longitudinal dimensions of the two metal layers to the longitudinal dimensions of the solid-state battery laminate is 0.5 or more and 0.8 or less, respectively, in a cross-sectional view. The solid-state battery according to any one of claims 1 to 3, wherein at least a part of the metal layer is covered with a resin layer. The solid-state battery according to any one of claims 1 to 4, wherein the two metal layers are in contact with the positive electrode terminal and the negative electrode terminal, respectively, and the two metal layers each have an external electrode connecting portion. The solid according to claim 5, wherein each of the two metal layers has a portion exposed from the resin layer, and each of the exposed portions forms the external electrode connecting portion. battery. The solid-state battery according to claim 5 or 6, wherein the area of the external electrode connecting portion is 0.1 or more and 1.0 or less with respect to the area of the external terminal. The solid-state battery according to any one of claims 5 to 7, wherein the external electrode connecting portion is provided on a side surface side having a normal in the electrode stacking direction of the solid-state battery laminate. The solid-state battery according to any one of claims 1 to 8, wherein the positive electrode layer and the negative electrode layer are layers capable of occluding and releasing lithium ions. It is a method of manufacturing solid-state batteries.
A step of forming a metal layer by a vapor deposition method or a sputtering method so as to cover the entire external terminal and to cover at least three side surfaces of the solid-state battery laminate in cross-sectional view.
A manufacturing method including a step of forming a resin layer so as to cover the metal layer by a wet method, and a step of peeling a part of the resin layer so as to form an external electrode connecting portion on the metal layer. It is a method of manufacturing solid-state batteries.
A step of peeling a part of the resin layer from a laminated film including a metal layer and a resin layer to expose a part of the metal layer.
A step of forming the laminated film into a bent shape so that the exposed portion of the metal layer is on the inside.
A step of inserting the solid-state battery into the bent shape of the laminated film so that the external terminal of the solid-state battery and the exposed portion of the metal layer come into contact with each other, and pressing the solid-state battery so as to join and bring them into close contact with each other. A manufacturing method comprising a step of peeling a part of a resin layer covering the metal layer so as to form an external electrode connecting portion on the metal layer.

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