All-solid-state secondary battery

Abstract

The present invention provides an all-solid-state secondary battery in which a short circuit is less likely to occur between a positive electrode-side current collector member and a negative electrode-side current collector member.　An all-solid-state secondary battery 1 includes: a power storage element 2 having a solid electrolyte layer 3, a positive electrode layer 4, and a negative electrode layer 5; a first current collector layer 6 provided on one main surface of the power storage element 2; a second current collector layer 7 provided on the other main surface of the power storage element 2; and a sealing layer 8 provided between the first current collector layer 6 and the second current collector layer 7 and sealing the power storage element 2. In a plan view, an outer peripheral edge 8a of the sealing layer 8 is located outside an outer peripheral edge 6a of the first current collector layer 6.

Description

All-solid-state secondary battery

[0001] The present invention relates to an all-solid-state secondary battery.

[0002] Lithium-ion secondary batteries are essential for mobile devices, electric vehicles, and other devices, and have established themselves as high-capacity, lightweight power sources. However, current lithium-ion secondary batteries primarily use flammable organic electrolytes, raising concerns about the risk of fire. To address this issue, development is underway on all-solid-state secondary batteries, such as all-solid-state lithium-ion secondary batteries and all-solid-state sodium-ion secondary batteries, which use solid electrolytes instead of organic electrolytes.

[0003] Patent Document 1 listed below discloses an all-solid-state secondary battery produced by bonding, with a thermosetting resin, the end face of a folded seal portion to the side face of an electrode body of an all-solid-state battery element enclosed in a laminate exterior body made of a laminate core material and a laminate sealing material.

[0004] JP 2015-79719 A

[0005] However, all-solid-state secondary batteries sealed with a resin material as in Patent Document 1 have a problem in that they are difficult to use in high-temperature environments. Furthermore, in all-solid-state secondary batteries, a short circuit may occur between a positive electrode-side current collecting member such as a positive electrode-side current collector or a positive electrode-side tab lead and a negative electrode-side current collecting member such as a negative electrode-side current collector or a negative electrode-side tab lead.

[0006] An object of the present invention is to provide an all-solid-state secondary battery in which a short circuit is unlikely to occur between a positive electrode side current collecting member and a negative electrode side current collecting member.

[0007] Hereinafter, various aspects of all-solid-state secondary batteries that solve the above problems will be described.

[0008] An all-solid-state secondary battery according to a first aspect of the present invention includes: an energy storage element having a solid electrolyte layer, a positive electrode layer, and a negative electrode layer; a first current collector layer provided on one main surface of the energy storage element; a second current collector layer provided on the other main surface of the energy storage element; and a sealing layer provided between the first current collector layer and the second current collector layer and sealing the energy storage element, wherein an outer periphery of the sealing layer is located outward from an outer periphery of the first current collector layer in a plan view.

[0009] An all-solid-state secondary battery according to Aspect 2 is the all-solid-state secondary battery of Aspect 1, and it is preferable that, in plan view, an outer periphery of the second current collector layer is disposed outward from an outer periphery of the sealing layer.

[0010] The all-solid-state secondary battery according to Aspect 3 is the all-solid-state secondary battery according to Aspect 1 or Aspect 2, and it is preferable that the corners of the first current collector layer have a rounded shape.

[0011] An all-solid-state secondary battery according to Aspect 4 is the all-solid-state secondary battery of Aspect 3, wherein the corners of the second current collector layer are rounded, and the radius of curvature of the corners of the first current collector layer is larger than the radius of curvature of the corners of the second current collector layer.

[0012] An all-solid-state secondary battery according to Aspect 5 is the all-solid-state secondary battery according to any one of Aspects 1 to 4, and when a width of the sealing layer disposed outside an outer peripheral edge of the first current collector layer in a plan view is defined as an exposed width, it is preferable that the exposed width of the sealing layer at corner portions of the first current collector layer is larger than the exposed width of the sealing layer at side portions of the first current collector layer.

[0013] An all-solid-state secondary battery according to Aspect 6 is the all-solid-state secondary battery according to any one of Aspects 1 to 5, and it is preferable that the sealing layer is provided at a connection portion between at least one of the first current collector layer and the second current collector layer and a tab lead in plan view.

[0014] An all-solid-state secondary battery according to Aspect 7 is the all-solid-state secondary battery according to any one of Aspects 1 to 6, and it is preferable that the sealing layer contains glass having a softening point of 500° C. or lower.

[0015] An all-solid-state secondary battery according to Aspect 8 is the all-solid-state secondary battery of Aspect 7, wherein the sealing layer is made of Bi ２ O ３ -B ２ O ３ It is preferable that the glass contains a glass-based material.

[0016] An all-solid-state secondary battery according to Aspect 9 is the all-solid-state secondary battery according to any one of Aspects 1 to 8, wherein an absolute value of a difference in thermal expansion coefficient between a material constituting the sealing layer and a material constituting at least one of the first current collector layer and the second current collector layer in a temperature range of 30° C. to 300° C. is 2.0×10 －６ / K or less is preferable.

[0017] According to the present invention, it is possible to provide an all-solid-state secondary battery in which a short circuit is unlikely to occur between the positive electrode side current collecting member and the negative electrode side current collecting member.

[0018] FIG. 1 is a schematic plan view showing an all-solid-state secondary battery according to a first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing a portion along line A-A in FIG. 1. FIGS. 3(a) and 3(b) are schematic plan views for explaining a manufacturing method of an all-solid-state secondary battery according to the first embodiment of the present invention. FIG. 4 is a schematic cross-sectional view showing an all-solid-state secondary battery according to a second embodiment of the present invention. FIG. 5 is a schematic cross-sectional view showing an all-solid-state secondary battery according to a third embodiment of the present invention. FIG. 6 is a schematic cross-sectional view showing an all-solid-state secondary battery according to a fourth embodiment of the present invention. FIG. 7 is a schematic cross-sectional view showing an all-solid-state secondary battery according to a fifth embodiment of the present invention. FIG. 8 is a schematic cross-sectional view showing an all-solid-state secondary battery according to a sixth embodiment of the present invention. FIG. 9 is a schematic cross-sectional view showing an all-solid-state secondary battery according to a seventh embodiment of the present invention. FIG. 10 is a schematic plan view showing an all-solid-state secondary battery of a comparative example.

[0019] Preferred embodiments of the present invention will be described below. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. In addition, in each drawing, components having substantially the same functions may be referred to by the same reference numerals.

[0020] [First embodiment] Fig. 1 is a schematic plan view showing an all-solid-state secondary battery according to a first embodiment of the present invention, and Fig. 2 is a schematic cross-sectional view showing a portion along line AA in Fig. 1.

[0021] 1 and 2 , the all-solid-state secondary battery 1 includes a power storage element 2, a first current collector layer 6, a second current collector layer 7, and a sealing layer 8. Examples of the all-solid-state secondary battery 1 include an all-solid-state lithium-ion secondary battery, an all-solid-state sodium-ion secondary battery, or an all-solid-state magnesium-ion secondary battery. While an all-solid-state sodium-ion secondary battery will be described below as an example, the following embodiment is applicable to all-solid-state secondary batteries in general.

[0022] The energy storage element 2 has a first main surface 2 a and a second main surface 2 b facing each other. A first current collector layer 6 is provided on the first main surface 2 a of the energy storage element 2. A second current collector layer 7 is provided on the second main surface 2 b of the energy storage element 2.

[0023] In this embodiment, the energy storage element 2 has a solid electrolyte layer 3, a positive electrode layer 4, and a negative electrode layer 5. In the energy storage element 2, the negative electrode layer 5, the solid electrolyte layer 3, and the positive electrode layer 4 are stacked in this order. The positive electrode layer 4 is provided on the first main surface 2a side of the energy storage element 2. The negative electrode layer 5 is provided on the second main surface 2b side of the energy storage element 2.

[0024] In this embodiment, the solid electrolyte layer 3 is made of a sodium ion conductive oxide and has a first main surface 3a and a second main surface 3b that face each other.

[0025] A positive electrode layer 4 is provided on a first main surface 3 a of the solid electrolyte layer 3. In this embodiment, the positive electrode layer 4 contains a positive electrode active material capable of absorbing and desorbing sodium. A first current collector layer 6 is provided on the main surface of the positive electrode layer 4 opposite to the side on which the solid electrolyte layer 3 is disposed.

[0026] An anode layer 5 is provided on the second main surface 3b of the solid electrolyte layer 3. In this embodiment, the anode layer 5 contains an anode active material capable of absorbing and releasing sodium. A second current collector layer 7 is provided on the main surface of the anode layer 5 opposite to the side on which the solid electrolyte layer 3 is disposed.

[0027] A sealing layer 8 is provided between the outer peripheral portion 6A of the first current collector layer 6 and the outer peripheral portion 7A of the second current collector layer 7. The sealing layer 8, together with the first current collector layer 6 and the second current collector layer 7, forms an internal space 1a. The energy storage element 2 is disposed in and sealed within this internal space 1a. In this embodiment, the sealing layer 8 has a frame-like shape. However, the shape of the sealing layer 8 is not particularly limited as long as it can form the internal space 1a together with the first current collector layer 6 and the second current collector layer 7 and seal the energy storage element 2.

[0028] In this embodiment, the outer peripheral edge 8 a of the sealing layer 8 is disposed outward from the outer peripheral edge 6 a of the first current collector layer 6 in a plan view. Therefore, in this embodiment, the outer peripheral edge 6 a of the first current collector layer 6 does not protrude beyond the outer peripheral edge 8 a of the sealing layer 8 in a plan view. However, in a plan view, a portion of the first current collector layer 6 may protrude beyond the outer peripheral edge 8 a of the sealing layer 8, or the first current collector layer 6 may not protrude completely. Specifically, in a plan view, an area portion of the first current collector layer 6 that protrudes beyond the outer peripheral edge 8 a of the sealing layer 8 is allowed as long as it accounts for 20% or less of the entire area of ​​the first current collector layer 6. However, in a plan view, it is preferable that the first current collector layer 6 does not protrude beyond the outer peripheral edge 8 a of the sealing layer 8 except for a portion that unintentionally protrudes beyond the outer peripheral edge 8 a of the sealing layer 8 against the design, and it is preferable that the first current collector layer 6 does not protrude at all beyond the outer peripheral edge 8 a of the sealing layer 8.

[0029] On the other hand, in this embodiment, the outer peripheral edge 7a of the second current collector layer 7 is disposed outward from the outer peripheral edge 8a of the sealing layer 8. Therefore, naturally, the outer peripheral edge 7a of the second current collector layer 7 is disposed outward from the outer peripheral edge 6a of the first current collector layer 6. From the viewpoint of more reliably exerting the effects of the present invention, it is preferable that the outer peripheral edge 7a of the second current collector layer 7 is disposed outward from the outer peripheral edge 6a of the first current collector layer 6, as in this embodiment.

[0030] The all-solid-state secondary battery 1 of this embodiment has the above-described configuration of the present invention, and therefore is less likely to cause a short circuit between the positive electrode side current collecting member and the negative electrode side current collecting member.

[0031] In conventional all-solid-state secondary batteries, a short circuit may occur between a positive electrode-side current collecting member, such as a positive electrode-side current collector or a positive electrode terminal, and a negative electrode-side current collecting member, such as a negative electrode-side current collector or a negative electrode terminal. For example, as in the all-solid-state secondary battery 101 of the comparative example shown in Fig. 10 , when the first current collecting layer 106 is configured to be the same size as the second current collecting layer 107 (when the outer peripheral edge of the sealing layer 108 is located inside the outer peripheral edge of the first current collecting layer 106), there is a problem that a short circuit is likely to occur particularly at the corner X.

[0032] In contrast, in the all solid state secondary battery 1 of this embodiment, in a plan view, the outer peripheral edge 8 a of the sealing layer 8 is disposed outward from the outer peripheral edge 6 a of the first current collector layer 6, and therefore the outer peripheral edge 6 a of the first current collector layer 6 does not protrude from the outer peripheral edge 8 a of the sealing layer 8. Therefore, as shown in FIG. 1 , a short circuit is unlikely to occur between the first current collector layer 6 on the positive electrode side and the second current collector layer 7 on the negative electrode side.

[0033] In the all-solid-state secondary battery 1 of this embodiment, a sealing layer 18A is provided at the connection between the first current collector layer 6 on the positive electrode side and the positive electrode tab lead 16. By providing the sealing layer 18A, it is possible to further reduce the likelihood of a short circuit occurring between the positive electrode tab lead 16 and a negative electrode current collecting member, such as the second current collector layer 7 on the negative electrode side or the negative electrode tab lead 17. In this embodiment, the sealing layer 18A is provided so as to extend from the portion of the first current collector layer 6 where the sealing layer 8 is provided to a portion of the positive electrode tab lead 16. However, it is sufficient that the sealing layer 18A is provided in at least a region overlapping with the second current collector layer 7 in a plan view. The sealing layer 18A may also be provided on the entire surface of the positive electrode tab lead 16. The sealing layer 18A is made of the same material as the sealing layer 8, but an appropriate insulating layer may be provided instead of the sealing layer 18A. The insulating layer may be made of, for example, polyimide, polyamideimide, epoxy resin, silicone resin, fluororesin such as polytetrafluoroethylene (PTFE), glass fiber, inorganic binder such as sodium silicate, or the like.

[0034] Furthermore, in the all-solid-state secondary battery 1 of this embodiment, a sealing layer 18B is provided at the connection between the negative electrode side second current collector layer 7 and the negative electrode side tab lead 17. By providing the sealing layer 18B, it is possible to further reduce the likelihood of a short circuit occurring between the negative electrode side tab lead 17 and a positive electrode side current collecting member such as the positive electrode side first current collector layer 6 or the positive electrode side tab lead 16. In this embodiment, the sealing layer 18B is provided so as to extend from the portion of the second current collector layer 7 where the sealing layer 8 is provided to a portion of the negative electrode side tab lead 17. However, it is sufficient that the sealing layer 18B is provided in at least a region overlapping with the first current collector layer 6 in a plan view. The sealing layer 18B may also be provided on the entire surface of the negative electrode side tab lead 17. Furthermore, the sealing layer 18B is made of the same material as the sealing layer 8, but an appropriate insulating layer may be provided instead of the sealing layer 18B. The insulating layer may be made of, for example, polyimide, polyamideimide, epoxy resin, silicone resin, fluororesin such as polytetrafluoroethylene (PTFE), glass fiber, inorganic binder such as sodium silicate, or the like.

[0035] In the all-solid-state secondary battery 1 of this embodiment, as described above, the outer peripheral edge 7 a of the second current collector layer 7 is disposed outward from the outer peripheral edge 6 a of the first current collector layer 6. Therefore, in a plan view, the area of ​​the second current collector layer 7 is larger than the area of ​​the first current collector layer 6. In a plan view, the area ratio of the first current collector layer 6 to the second current collector layer 7 (first current collector layer 6 / second current collector layer 7) can be, for example, 0.5 or more and 0.99 or less. In this case, a short circuit is even less likely to occur between a positive-electrode-side current collector member such as the first current collector layer 6 or the positive-electrode-side tab lead 16 on the positive electrode side and a negative-electrode-side current collector member such as the second current collector layer 7 or the negative-electrode-side tab lead 17 on the negative electrode side.

[0036] As shown in FIG. 1 , the corners 6 b of the first current collector layer 6 are preferably rounded. In this case, a short circuit is even less likely to occur between the positive electrode side current collector and the negative electrode side current collector. The corners 7 b of the second current collector layer 7 may also be rounded. In this case, the radius of curvature of the corners 6 b of the first current collector layer 6 is preferably larger than the radius of curvature of the corners 7 b of the second current collector layer 7. In this case, a short circuit is even less likely to occur between the positive electrode side current collector and the negative electrode side current collector. The corners 8 b of the sealing layer 8 may also be rounded.

[0037] Furthermore, when the width of sealing layer 8 disposed outside outer peripheral edge 6 a of first current collector layer 6 in a plan view is defined as the exposed width, the exposed width of sealing layer 8 at corners 6 b of first current collector layer 6 is preferably larger than the exposed width of sealing layer 8 at sides 6 c of first current collector layer 6. In this case, it is possible to further reduce the likelihood of a short circuit occurring between the positive electrode current collector and the negative electrode current collector at corners 6 b of first current collector layer 6.

[0038] In this embodiment, as shown in FIG. 2 , sealing layer 8 has a tapered shape. More specifically, sealing layer 8 is provided so that its width increases from the first current collector layer 6 side to the second current collector layer 7 side. Sealing layer 8 is provided so that its width increases outward. When sealing layer 8 has a tapered shape, contact between the first current collector layer 6 and the second current collector layer 7 is reduced, making it even less likely for a short circuit to occur. Note that in the present invention, sealing layer 8 does not necessarily have a tapered shape. Even in this case, it is preferable that the area of ​​the portion of sealing layer 8 in contact with the first current collector layer 6 be smaller than the area of ​​the portion of sealing layer 8 in contact with the second current collector layer 7 in a plan view.

[0039] In this embodiment, the internal space 1a of the all-solid-state secondary battery 1 is hollow. As described above, the internal space 1a of the all-solid-state secondary battery 1 is preferably hollow, but the internal space 1a may be filled with an inorganic porous body. The inorganic porous body is preferably an insulating material. Examples of the inorganic porous body that can be used include glass wool, rock wool, ceramic fiber, alkaline earth silicate fiber, and porous ceramic body.

[0040] In this embodiment, the internal space 1a of the all-solid-state secondary battery 1 is a vacuum. The internal space 1a of the all-solid-state secondary battery 1 may be filled with an inert gas or a mixed gas of a reducing gas and an inert gas. Examples of the inert gas that can be used include rare gas, nitrogen gas, and carbon dioxide gas, and these inert gases can also be mixed. Of these, the inert gas is preferably a rare gas. In this case, more stable battery characteristics can be obtained in the all-solid-state secondary battery 1. Examples of rare gases include helium, neon, and argon, and these rare gases can also be mixed. Of these, argon is preferably used as the rare gas. Examples of the mixed gas of a reducing gas and an inert gas that can be used include a mixed gas of hydrogen gas and nitrogen gas.

[0041] Pressure P outside the all-solid-state secondary battery 1 at 25°C ２ and the pressure P １The difference between ２ -P １ ) is preferably 10 －６ The difference (P ２ -P １ ) is equal to or greater than the lower limit, the first current collector layer 6 and the second current collector layer 7 can be elastically deformed toward the internal space 1 a, and the current collector layers can be brought into more reliable contact with the electrode layers. Therefore, in this case, the all-solid-state secondary battery 1 can achieve even more stable battery characteristics.

[0042] Hereinafter, each layer constituting the all-solid-state secondary battery 1 will be described in detail.

[0043] (Solid Electrolyte Layer) The solid electrolyte layer 3 can be formed of an ion-conductive material such as a sodium ion-conductive oxide. Examples of sodium ion-conductive oxides include compounds containing at least one element selected from Al, Y, Zr, Si, and P, Na, and O. Specific examples of sodium ion-conductive oxides include beta-alumina and NASICON crystals, which have excellent sodium ion conductivity. Of these, beta-alumina is preferred as the sodium ion-conductive oxide from the viewpoint of achieving even better sodium ion conductivity.

[0044] Beta alumina includes β-alumina (theoretical composition formula: Na ２ O.11Al ２ O ３ ) and β″-alumina (theoretical composition formula: Na ２ O 5.3 Al ２ O ３ β"-alumina is a metastable material, so it is usually ２The beta-alumina is preferably made of β"-alumina alone or a mixture of β"-alumina and β-alumina, since β"-alumina has a higher sodium ion conductivity than β-alumina. １．４９ Li ０．２５ Al １０．７５ O １７ , Na １．７ Li ０．３ Al １０．７ O １７ , Na １．７２ Li ０．３ Al １０．６６ O １７ , Na １．６ Li ０．３４ Al １０．６６ O １７ Li etc. ２ O-stabilized β″-alumina or (Al １０．３２ Mg ０．６８ O １６ ) (Na １．６８ O), (Al １０．３５ Mg ０．６５ O １６ ) (Na １．６５ O), (Al ８．８７ Mg ２．１３ O １６ ) (Na ３．１３ O), Na １．６７ Mg ０．６７ Al １０．３３ O １７ It is more preferable to use MgO-stabilized β″-alumina such as

[0045] NASICON crystals include Na ３ Zr ２ Si ２ P.O. １２ , Na ３．２ Zr １．３ Si ２．２ P ０．７ O １０．５ , Na ３ Zr １．６ Ti ０．４ Si ２ P.O. １２ , Na ３ Hf ２ Si ２ P.O. １２ , Na ３．４Zr ０．９ Hf １．４ Al ０．６ Yes １．２ P １．８ O １２ 、No ３ Zr １．７ N﹂ ０．２４ Yes ２ PO １２ 、No ３．６ Today ０．２ Y ０．８ Yes ２．８ O ９ 、No ３ Zr １．８８ Y ０．１２ Yes ２ PO １２ 、No ３．１２ Zr １．８８ Y ０．１２ Yes ２ PO １２ 、No ３．０５ Zr ２ Yes ２．０６ P ０．９５ O １２ 、No ３．４ Zr ２ Yes ２．４ P ０．６ O １２ 、No ３．４ Zr １．９ Zn ０．１ Yes ２．４ P ０．６ O １２ 、No ３．４ Zr １．９ Mg ０．１ Yes ２．４ P ０．６ O １２ 、No ３．４ Zr １．９ Zn ０．１ Yes ２．２ P ０．８ O １２ 、No ３．４ Zr １．９ Mg ０．１ Yes ２．２ P ０．８ O １２ 、No ２．８ Zr ２ Yes ２．４ P ０．６ O １２ 、No ５ YSi ４ O１２ 、No ３．１ Zr １．９５ Mg ０．０５ Yes ２ PO １２ 、No ３．１ Zr １．９ Yes ０．１ Yes ２ PO １２ 、No ３．１ Zr １．９ N$ ０．１ Yes ２ PO １２ 、No ３．１ Zr １．９ Y ０．１ Yes ２ PO １２ 、No ３．２５６ Zr １．８７２ Mg ０．１２８ Yes ２ PO １２ 、No ３．２ Zr １．９ Ca ０．１ Yes ２ PO １２ 、No ３．２ Zr １．９ Mg ０．１ Yes ２ PO １２ 、No ３．２ Zr ２ Yes ２．２ P ０．８ O １２ 、No ３．３８ Zr １．８０ Al ０．２６ Yes ２．０６ P ０．８８ O １２ 、No ３．４３ Zr １．８３ Zn ０．２２ Yes １．９３ P １．０２ O １２ 、No ３．４ Sc ０．４ Zr １．６ Yes ２ PO １２ 、No ３．４ Zr １．８ Mg ０．２ Yes ２ PO １２ 、No ３．４ Zr １．９ Zn ０．１ Yes２．２ P ０．８ O １２ , Na ３．５７ Zr １．７２ La ０．２１ Si ２．０８ P ０．９２ O １２ , Na ３ Zr １．９８ Nb ０．０８ Si ２ P.O. １２ , Na ３ Zr １．９ Ce ０．１ Si ２ P.O. １２ , Na ３ Zr １．９ Gd ０．１ Si ２ P.O. １２ , Na ３ Zr １．９ Ti ０．１ Si ２ P.O. １２ , Na ３ Zr １．９ Yb ０．１ Si ２ P.O. １２ , or Na ３．６ Zr ０．１３ Yb １．６７ Si ０．１１ P ２．９ O １２ From the viewpoint of superior sodium ion conductivity, Na ３．１２ Zr １．８８ Y ０．１２ Si ２ P.O. １２ , Na ３．４ Zr ２ Si ２．４ P ０．６ O １２ , Na ３．４ Zr １．９ Zn ０．１ Si ２．４ P ０．６ O １２ , Na ３．４ Zr １．９ Mg ０．１ Si ２．４ P ０．６ O １２ , Na ３．４ Zr １．９Zn ０．１ Si ２．２ P ０．８ O １２ , Na ３．４ Zr １．９ Mg ０．１ Si ２．２ P ０．８ O １２ , Na ３．４３ Zr １．８３ Zn ０．２２ Si １．９３ P １．０２ O １２ , Na ３．４ Sc ０．４ Zr １．６ Si ２ P.O. １２ , Na ３．４ Zr １．８ Mg ０．２ Si ２ P.O. １２ , or Na ３．４ Zr １．９ Zn ０．１ Si ２．２ P ０．８ O １２ It is preferable to use

[0046] The solid electrolyte layer 3 can be produced by mixing raw material powders, molding the mixed raw material powders, and then firing the molded product. For example, the solid electrolyte layer 3 can be produced by forming a green sheet from the raw material powders into a slurry, and then firing the green sheet. The solid electrolyte layer 3 may also be produced by a sol-gel method.

[0047] The thickness of the solid electrolyte layer 3 is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more, and is preferably 1000 μm or less, more preferably 500 μm or less, and even more preferably 300 μm or less. When the thickness of the solid electrolyte layer 3 is equal to or greater than the above-mentioned lower limit, the mechanical strength of the all-solid-state secondary battery 1 can be further increased, making it less susceptible to breakage and internal short circuits. When the thickness of the solid electrolyte layer 3 is equal to or less than the above-mentioned upper limit, the internal resistance can be further reduced, making it possible to further improve the capacity and operating voltage of the all-solid-state secondary battery 1. Also, the energy density per unit volume of the all-solid-state secondary battery 1 can be further improved.

[0048] (Positive Electrode Layer) The positive electrode active material contained in the positive electrode layer 4 is not particularly limited, but for example, ｘ M ｙ P ２ O ｚ (1≦x≦2.8, 0.95≦y≦1.6, 6.5≦z≦8, M is at least one element selected from the group consisting of Fe, Ni, Co, Mn, and Cr) can be used as a positive electrode active material. ｘ MP ２ O ７ (1≦x≦2, M is at least one selected from the group consisting of Fe, Ni, Co, Mn, and Cr), or ４ M ３ (P.O. ４ ) ２ (P ２ O ７ ) (M is at least one selected from the group consisting of Fe, Ni, Co, Mn, and Cr). ２ FeP ２ O ７ , Na ２ CoP ２ O ７ , or Na ２ NiP ２ O ７、 Na ４ Fe ３ (P.O. ４ ) ２ (P ２ O ７ ) etc. can be used.

[0049] In this specification, crystallized glass refers to the precursor glass containing amorphous phase that is heated (fired) to precipitate crystals (crystallization).In crystallized glass, all of the amorphous phase may be transformed into crystalline phase, or amorphous phase may remain.In addition, in crystallized glass, one type of crystal may be precipitated, or two or more types of crystal may be precipitated.For example, it is possible to determine whether crystallized glass is crystallized glass by the peak angle shown by powder X-ray diffraction (XRD).

[0050] The positive electrode layer 4 may contain a sodium ion conductive solid electrolyte and a conductive additive in addition to the positive electrode active material. The positive electrode layer 4 may contain, for example, in mass %, 60% to 99.9% of the positive electrode active material, 0% to 30% of the sodium ion conductive solid electrolyte, and 0.1% to 10% of the conductive additive.

[0051] The sodium ion conductive solid electrolyte may be, for example, one of those described in the section on the solid electrolyte layer 3. The conductive additive may be, for example, conductive carbon. Examples of conductive carbon include acetylene black, carbon black, ketjen black, vapor grown carbon fiber (VGCF), and carbon nanotubes.

[0052] The positive electrode layer 4 can be formed, for example, by forming an electrode material layer on the first main surface 3 a of the solid electrolyte layer 3 and firing the electrode material layer. The electrode material layer can be obtained, for example, by applying a paste containing a positive electrode active material precursor and, if necessary, a solid electrolyte powder and a conductive additive, and then drying the paste. The paste may contain, if necessary, a binder, a plasticizer, a solvent, or the like. The electrode material layer may be a powder compact.

[0053] The thickness of the positive electrode layer 4 is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more, and is preferably 500 μm or less, more preferably 300 μm or less, and even more preferably 200 μm or less. When the thickness of the positive electrode layer 4 is equal to or greater than the above-mentioned lower limit, the capacity of the all-solid-state secondary battery 1 can be further improved. When the thickness of the positive electrode layer 4 is equal to or less than the above-mentioned upper limit, the capacity and operating voltage of the all-solid-state secondary battery 1 can be further improved, and the positive electrode layer 4 is less likely to shrink due to firing when formed, and the positive electrode layer 4 can be made less likely to peel off.

[0054] A metal thin film may be provided on the main surface of the positive electrode layer 4 facing the first current collector layer 6. In this case, the electronic conductivity at the interface between the positive electrode layer 4 and the first current collector layer 6 can be further increased. Examples of the metal thin film include an aluminum film. The metal thin film can be formed by, for example, a sputtering method or a vacuum deposition method. In particular, from the viewpoint of improving adhesion to the positive electrode layer 4, the metal thin film is preferably a sputtered film formed by a sputtering method.

[0055] (Negative Electrode Layer) The negative electrode active material contained in the negative electrode layer 5 is not particularly limited, and may be, for example, a carbon electrode material such as hard carbon or soft carbon. The carbon electrode material is preferably hard carbon. However, the negative electrode active material may be an alloy-based negative electrode active material capable of absorbing sodium, such as tin, bismuth, lead, or phosphorus, or may contain metallic sodium. The negative electrode active material may also be an oxide-based negative electrode active material capable of absorbing sodium, such as anatase-type titanium oxide, rutile-type titanium oxide, or brookite-type titanium oxide. It is preferable that the negative electrode layer 5 is not a negative electrode layer consisting of a single phase of metallic sodium.

[0056] The negative electrode layer 5 may contain a sodium ion conductive solid electrolyte and a conductive additive in addition to the negative electrode active material. The negative electrode layer 5 may contain, for example, by mass %, 60% to 95% of the negative electrode active material, 5% to 35% of the sodium ion conductive solid electrolyte, and 0% to 5% of the conductive additive.

[0057] The sodium ion conductive solid electrolyte may be, for example, one described in the section on the solid electrolyte layer 3. The conductive additive may be, for example, one described in the section on the positive electrode layer 4.

[0058] The negative electrode layer 5 can be formed, for example, by forming an electrode material layer on the second main surface 3b of the solid electrolyte layer 3 and firing the electrode material layer. The electrode material layer can be obtained, for example, by applying and drying a paste containing a carbon electrode material precursor (a precursor of a carbon electrode material made of hard carbon) and, as necessary, a sodium ion conductive solid electrolyte and a conductive additive. The paste may contain, as necessary, a binder, a plasticizer, a solvent, or the like. The electrode material layer may be a compact.

[0059] The thickness of the anode layer 5 is preferably 3 μm or more, more preferably 7 μm or more, and even more preferably 10 μm or more, and is preferably 300 μm or less, more preferably 200 μm or less, and even more preferably 100 μm or less. When the thickness of the anode layer 5 is equal to or greater than the above lower limit, deposition of sodium metal in the anode layer 5 during charging of the all-solid-state secondary battery 1 can be suppressed, and the cycle performance of the all-solid-state secondary battery 1 can be improved. When the thickness of the anode layer 5 is equal to or less than the above upper limit, the capacity and operating voltage of the all-solid-state secondary battery 1 can be further improved.

[0060] A metal thin film may be provided on the main surface of the negative electrode layer 5 facing the second current collector layer 7. In this case, the electronic conductivity at the interface between the negative electrode layer 5 and the second current collector layer 7 can be further increased. The metal thin film can be, for example, an aluminum film. The metal thin film can be formed by, for example, a sputtering method or a vacuum deposition method. In particular, from the viewpoint of improving adhesion to the negative electrode layer 5, the metal thin film is preferably a sputtered film formed by a sputtering method.

[0061] (First current collector layer and second current collector layer) The materials for the first current collector layer 6 and the second current collector layer 7 are not particularly limited, and metal materials such as aluminum, titanium, silver, copper, stainless steel (SUS), or alloys thereof can be used, respectively. These metal materials may be used alone or in combination. The above alloy refers to an alloy containing at least one of the above metals.

[0062] The thickness of each of the first current collector layer 6 and the second current collector layer 7 is preferably 10 μm or more, more preferably 30 μm or more, and even more preferably 40 μm or more, and is preferably 1000 μm or less, more preferably 500 μm or less, and even more preferably 300 μm or less. When the thickness of the first current collector layer 6 and the second current collector layer 7 is within the above range, the current collecting function as a current collector can be further improved.

[0063] In plan view, the outer peripheral edges of the first current collector layer 6 and the second current collector layer 7 are disposed outside the outer peripheral edge of the energy storage element 2. The protrusion width of the first current collector layer 6 and the second current collector layer 7 from the solid electrolyte layer 3 is preferably 0.1 mm or more, more preferably 0.2 mm or more, and is preferably 3 mm or less, more preferably 2 mm or less.

[0064] The positive electrode tab lead 16 and the negative electrode tab lead 17 can be made of, for example, aluminum, nickel, stainless steel (SUS), titanium, iron, copper, silver, gold, or the like.

[0065] If the positive electrode tab lead 16 and the negative electrode tab lead 17 are made of a material that is difficult to solder, such as SUS430, a metal layer may be formed on the surface of the tab lead before welding to the tab. Examples of the metal layer include copper (Cu), gold (Au), silver (Ag), palladium (Pd), tin (Sn), zinc (Zn), cobalt (Co), nickel (Ni), a Ni-Cu alloy, or a Ni-P alloy. These materials may be used alone or in combination.

[0066] (Sealing Layer) As a material for the sealing layer 8, for example, glass can be used. The softening point of the glass is not particularly limited, but is preferably 300°C or higher, more preferably 350°C or higher, even more preferably 400°C or higher, and is preferably 600°C or lower, more preferably 550°C or lower, and even more preferably 500°C or lower. When the softening point of the glass is equal to or higher than the above lower limit, the all-solid-state secondary battery 1 can be used more stably at high temperatures. Furthermore, when the softening point of the glass is equal to or lower than the above upper limit, the thermal stability and chemical stability of the glass can be further improved, and the glass can be more easily handled as a powder or paste.

[0067] The glass is not particularly limited, but for example, Bi ２ O ３ -B ２ O ３ Bismuth-based glass such as Bi-based glass can be used. Bismuth-based glass has a glass composition of, in mol %, Bi ２ O ３ 25% to 60%, B ２ O ３ It is preferable that the content of CuO+MnO is 10% to 35%, and CuO+MnO is 1% to 40%.

[0068] When the first current collector layer 6 and the second current collector layer 7 are made of aluminum, the glass contained in the sealing layer 8 may be, for example, a tellurium-based glass. The tellurium-based glass has a glass composition, in mol %, of TeO ２ 15% to 80%, MoO ３ + Ag ２ O 0.1% to 30%, V ２ O ５ It is preferable that the content of SiO2 is 5% to 40% and that of CuO is 0.1% to 35%.

[0069] The thickness of sealing layer 8 is not particularly limited, but is preferably 1 μm or more, more preferably 10 μm or more, even more preferably 100 μm or more, and is preferably 100 mm or less, more preferably 10 mm or less, and even more preferably 1 mm or less. When the thickness of sealing layer 8 is equal to or greater than the above-mentioned lower limit, the first current collector layer 6 and the second current collector layer 7 can be more reliably bonded to each other. On the other hand, when the thickness of sealing layer 8 is equal to or less than the above-mentioned upper limit, thermal strain resulting from the difference in thermal expansion coefficients between sealing layer 8 and the first current collector layer 6 and the second current collector layer 7 can be further reduced, thereby further increasing the bonding strength.

[0070] The width of sealing layer 8 is not particularly limited, but is preferably 10 μm or more, more preferably 100 μm or more, even more preferably 1000 μm or more, and is preferably 500 mm or less, more preferably 100 mm or less, and even more preferably 10 mm or less. When the width of sealing layer 8 is equal to or greater than the above-mentioned lower limit, the airtightness of internal space 1 a can be more reliably maintained, and leakage from internal space 1 a can be more reliably prevented. On the other hand, when the width of sealing layer 8 is equal to or less than the above-mentioned upper limit, thermal strain resulting from the difference in thermal expansion coefficients between sealing layer 8 and first current collector layer 6 and second current collector layer 7 can be further reduced, and bonding strength can be further increased.

[0071] In this embodiment, the absolute value of the difference in thermal expansion coefficient between the material constituting the sealing layer 8 and the material constituting at least one of the first current collector layer 6 and the second current collector layer 7 in the temperature range of 30°C to 300°C is preferably 2.0 x 10 －６ / K or less, more preferably 1.0 × 10 －６ / K or less, more preferably 0.5 × 10 －６ / K or less. In this case, it is possible to further increase the adhesion between the sealing layer 8 and at least one of the first current collector layer 6 and the second current collector layer 7. Therefore, it is desirable that the materials constituting the first current collector layer 6 and the second current collector layer 7 both satisfy the above-mentioned range of the absolute value of the difference in thermal expansion coefficient.

[0072] A method for manufacturing the all-solid-state secondary battery 1 will be described below.

[0073] (Method for manufacturing all-solid-state secondary battery) First, an energy storage element 2 is prepared. At this time, a single energy storage element 2 may be prepared, or a stack of a plurality of energy storage elements 2 may be prepared. Note that, hereinafter, both of the above cases will be referred to as the energy storage element 2.

[0074] Next, the first current collector layer 6 and the second current collector layer 7 are prepared. At this time, the first current collector layer 6 is prepared as a current collector layer having a smaller area than the second current collector layer 7. For example, when the dimensions of the first current collector layer 6 are 48 mm × 48 mm, the dimensions of the second current collector layer 7 can be set to 50 mm × 50 mm.

[0075] A positive electrode tab lead 16 is joined to the first current collector layer 6. A negative electrode tab lead 17 is joined to the second current collector layer 7. The positive electrode tab lead 16 and the negative electrode tab lead 17 can be joined to the current collector layers by welding, soldering, or the like.

[0076] Next, a paste for forming a sealing layer is prepared. The paste for forming a sealing layer can be prepared, for example, by the following method.

[0077] First, raw material powders prepared to obtain a desired glass composition are melted until a homogeneous glass is obtained. The melting temperature can be, for example, 700° C. or higher and 1000° C. or lower. The melting time can be, for example, 1 hour or higher and 2 hours or lower.

[0078] Next, the obtained molten glass is formed into a film or the like, and then crushed and classified to produce glass powder. ５０ The average particle size can be 1 μm or more and 20 μm or less. Alternatively, a refractory filler powder may be mixed with the glass powder to form the sealing material. In this case, the thermal expansion coefficient of the sealing material can be adjusted to be close to the thermal expansion coefficients of the first current collector layer 6 and the second current collector layer 7. Furthermore, the mechanical strength of the resulting sealing layer 8 can be further increased. The refractory filler powder can be added within a range that does not impair the fluidity of the glass powder. For example, the amount of the refractory filler powder added can be 40 volume % or less of the entire sealing material.

[0079] The refractory filler constituting the refractory filler powder is not particularly limited, and examples thereof include zircon, zirconia, tin oxide, quartz, β-spodumene, cordierite, willemite, mullite, quartz glass, β-eucryptite, β-quartz, zirconium phosphate, zirconium tungstate phosphate, zirconium tungstate, NbZr(PO ４ ) ３ [AB ２ (MO ４ ) ３

[0033] (wherein A is Li, Na, K, Mg, Ca, Sr, Ba, Zn, Cu, Ni, Mn, etc.; B is Zr, Ti, Sn, Nb, Al, Sc, Y, etc.; M is P, Si, W, Mo, etc.), or a solid solution thereof can be used. Among these, the refractory filler is preferably zirconium phosphate, cordierite, willemite, or zirconium tungstate phosphate. These refractory fillers have a low thermal expansion coefficient, and therefore can further increase the mechanical strength. In addition, Bi ２ O ３ -B ２ O ３ It also has excellent compatibility with glass powders.

[0080] Next, a vehicle is added to the sealing material and kneaded to obtain a sealing layer forming paste. Here, the vehicle mainly consists of an organic solvent and a resin. The resin can be added to adjust the viscosity of the paste. If the softening point of the sealing material is low and problems arise with the degreasing process, a high-viscosity organic solvent that does not contain a resin can also be used. If necessary, a surfactant, a thickener, or the like can also be added to the vehicle. Before kneading the glass powder or refractory filler powder with the vehicle, the glass powder or refractory filler powder may be subjected to vacuum treatment for a certain period of time at a temperature near the glass transition point of the glass powder in order to remove traces of moisture or organic matter adhering to the surface of the glass powder or refractory filler powder.

[0081] The organic solvent is preferably one that has a low boiling point and leaves little residue after firing. It is also preferable that the organic solvent does not alter the glass. The content of the organic solvent can be, for example, 10% by mass or more and 40% by mass or less, based on the total amount of the vehicle.

[0082] Examples of the organic solvent include propylene carbonate, toluene, N,N'-dimethylformamide (DMF), 1,3-dimethyl-2-imidazolidinone (DMI), dimethyl carbonate, butyl carbitol acetate (BCA), isoamyl acetate, dimethyl sulfoxide, acetone, and methyl ethyl ketone. The organic solvent is preferably a higher alcohol. Higher alcohols have viscosity in themselves, so they can be made into a paste without adding a resin to the vehicle. From the viewpoint of excellent viscosity, the organic solvent is preferably pentanediol or diethylpentanediol (C ９ H ２０ O ２ ) and other pentanediol derivatives.

[0083] The resin preferably has a low decomposition temperature, leaves little residue after firing, and is resistant to deterioration of the glass. The resin content can be 0.1% by mass or more and 20% by mass or less based on the total mass of the vehicle. Examples of resins that can be used include nitrocellulose, polyethylene glycol derivatives, polyethylene carbonate, and acrylic esters (acrylic resins).

[0084] Next, the prepared sealing layer-forming paste is applied to the first current collector layer 6 and the second current collector layer 7. Specifically, as shown in FIG. 3( a), the sealing layer-forming paste 8A is applied to the outer peripheral edge portion 6A of the first current collector layer 6 so as to form a frame shape. Furthermore, as shown in FIG. 3( b), the sealing layer-forming paste 8A is applied to the outer peripheral edge portion 7A of the second current collector layer 7 so as to form a frame shape. Note that the width of the sealing layer-forming paste 8A applied to the first current collector layer 6 is desirably smaller than the width of the sealing layer-forming paste 8A applied to the second current collector layer 7. The ratio of the width of the sealing layer-forming paste 8A applied to the second current collector layer 7 to the width of the sealing layer-forming paste 8A applied to the first current collector layer 6 (second current collector layer 7 / first current collector layer 6) can be, for example, 0.15 or more and 0.95 or less.

[0085] The sealing layer-forming paste 8A can be applied to the first current collector layer 6 and the second current collector layer 7 using, for example, a coater such as a dispenser or a screen printer. It is desirable to make the surface roughness of the area where the sealing layer-forming paste 8A is applied rougher than that of other areas. In this case, the adhesion between the resulting sealing layer 8 and the first current collector layer 6 and the second current collector layer 7 can be further improved. Examples of methods for increasing the surface roughness of the area where the sealing layer-forming paste 8A is applied include etching with hydrochloric acid or blasting, such as wet blasting. The surface roughness of the area where the sealing layer-forming paste 8A is applied can be, for example, 0.5 or more and 5 or less in terms of arithmetic mean roughness Ra.

[0086] The sealing layer-forming paste 8A is preferably also applied to the connection portion between the first current collector layer 6 and the positive electrode tab lead 16 (the portion where the above-mentioned sealing layer 18A is provided).The sealing layer-forming paste 8A is also preferably applied to the connection portion between the second current collector layer 7 and the negative electrode tab lead 17 (the portion where the above-mentioned sealing layer 18B is provided).

[0087] Next, the sealing layer forming paste 8A applied to the first current collector layer 6 and the second current collector layer 7 is pre-fired. The pre-fired temperature can be, for example, 200° C. or higher and 500° C. or lower. The pre-fired time can be, for example, 5 minutes or higher and 300 minutes or lower. Note that, before pre-firing, the sealing layer forming paste 8A may be dried in advance to dry out the organic solvent contained in the sealing layer forming paste 8A.

[0088] Next, as shown in FIG. 3( b), the energy storage element 2 is mounted on the second current collector layer 7. Next, the first current collector layer 6 is superimposed on the second current collector layer 7 and bonded. When superimposing the first current collector layer 6 on the second current collector layer 7, the layers are superimposed so that the surfaces coated with the sealing layer-forming paste 8A overlap each other. At this time, as shown in FIG. 1, the outer peripheral edge 8a of the resulting sealing layer 8 is positioned outside the outer peripheral edge 6a of the first current collector layer 6 in a plan view.

[0089] The first current collector layer 6 and the second current collector layer 7 can be bonded by firing the sealing layer-forming paste 8A. The sealing layer 8 can be formed by firing the sealing layer-forming paste 8A. The firing temperature of the sealing layer-forming paste 8A is preferably 300°C or higher, more preferably 350°C or higher, and even more preferably 400°C or higher, and is preferably 700°C or lower, more preferably 600°C or lower, and even more preferably 500°C or lower. The firing time of the sealing layer-forming paste 8A can be, for example, 10 minutes or longer and 600 minutes or shorter. The sealing layer-forming paste 8A is fired in a N ２ It is desirable to carry out the treatment in an inert atmosphere such as argon or Ar, or in a vacuum atmosphere.

[0090] The area where sealing layer 8 is to be formed may be covered in advance with a highly heat-resistant adhesive. In this case, it is possible to further increase the adhesion between the resulting sealing layer 8 and the first and second current collector layers 6 and 7. Examples of highly heat-resistant adhesives include polyimide, polyamideimide, epoxy resin, silicone resin, and fluorine-based resins such as polytetrafluoroethylene.

[0091] In the all-solid-state secondary battery 1 obtained by the manufacturing method of this embodiment, the outer peripheral edge 8 a of the sealing layer 8 is disposed outward from the outer peripheral edge 6 a of the first current collector layer 6 in plan view, and therefore, a short circuit can be made less likely to occur between a positive-electrode-side current collecting member such as the first current collector layer 6 or the positive-electrode-side tab lead 16 on the positive electrode side and a negative-electrode-side current collecting member such as the second current collector layer 7 or the negative-electrode-side tab lead 17 on the negative electrode side.

[0092] [Second and Third Embodiments] Fig. 4 is a schematic cross-sectional view showing an all-solid-state secondary battery according to a second embodiment of the present invention, and Fig. 5 is a schematic cross-sectional view showing an all-solid-state secondary battery according to a third embodiment of the present invention.

[0093] As shown in Fig. 4, in the all-solid-state secondary battery 21 of the second embodiment, the second current collector layer 27 has a container-like shape. An energy storage element 22 is mounted inside this container-like second current collector layer 27. In the energy storage element 22, a positive electrode layer is provided on the first current collector layer 6 side, and a negative electrode layer is provided on the second current collector layer 27 side. A sealing layer 8 is provided on the upper surface of the container-like second current collector layer 27 and is joined to the flat plate-like first current collector layer 6. An insulating layer may be provided on the inner surface of the side wall of the container-like second current collector layer 27. The other points are the same as those of the first embodiment.

[0094] As shown in FIG. 5 , in an all-solid-state secondary battery 31 of the third embodiment, a second current collector layer 37 is drawn into a rectangular cylindrical shape. An energy storage element 32 is mounted inside the second current collector layer 37 drawn into this rectangular cylindrical shape. In the energy storage element 32, a positive electrode layer is provided on the first current collector layer 6 side, and a negative electrode layer is provided on the second current collector layer 37 side. A sealing layer 8 is provided on the upper surface of the second current collector layer 37 drawn into a rectangular cylindrical shape, and is joined to the flat first current collector layer 6. An insulating layer may be provided on the inner surface of the sidewall of the second current collector layer 37 drawn into a rectangular cylindrical shape. Other points are the same as those of the first embodiment.

[0095] In the second and third embodiments as well, the outer peripheral edge 8 a of the sealing layer 8 is positioned outward of the outer peripheral edge 6 a of the first current collector layer 6 in plan view, which makes it less likely that a short circuit will occur between a positive-electrode-side current collecting member such as the first current collector layer 6 or the positive-electrode-side tab lead 16 on the positive electrode side and a negative-electrode-side current collecting member such as the second current collector layer 27, 37 or the negative-electrode-side tab lead 17 on the negative electrode side.

[0096] Fourth Embodiment FIG. 6 is a schematic cross-sectional view showing an all-solid-state secondary battery according to a fourth embodiment of the present invention.

[0097] As shown in Fig. 6, in an all-solid-state secondary battery 41 of the fourth embodiment, a spacer pin 42 is provided between the first current collector layer 6 and the second current collector layer 7 in the internal space 1a. The shape of the spacer pin 42 is not particularly limited, and examples thereof include a cylindrical shape, a rectangular pillar shape, and a hollow cylinder. Examples of the spacer pin 42 include a ceramic pin. Examples of the material of the ceramic pin include alumina, zirconia, and yttria-stabilized zirconia. Other points are the same as those of the first embodiment.

[0098] As in the fourth embodiment, spacer pins 42 may be provided between the first current collector layer 6 and the second current collector layer 7. By providing the spacer pins 42, the distance between the first current collector layer 6 and the second current collector layer 7 can be maintained more reliably.

[0099] Fifth Embodiment FIG. 7 is a schematic cross-sectional view showing an all-solid-state secondary battery according to a fifth embodiment of the present invention.

[0100] 7 , in an all-solid-state secondary battery 51 according to the fifth embodiment, two energy storage elements 2 are stacked in an internal space 1 a. The two energy storage elements 2 are stacked such that their respective negative electrode layers 5 face each other. A wiring conductor 52 is provided between the negative electrode layers 5 of the two energy storage elements 2. Note that the two energy storage elements 2 may also be stacked such that their respective positive electrode layers 4 face each other, and a wiring conductor 52 may be provided between the positive electrode layers 4 of the two energy storage elements 2.

[0101] In addition, in the all-solid-state secondary battery 51, the sealing layer is composed of a first sealing layer portion 58 a and a second sealing layer portion 58 b. In the stacking direction of the energy storage element 2, a metal intermediate layer 53 is provided between the first sealing layer portion 58 a and the second sealing layer portion 58 b.

[0102] The first sealing layer portion 58a and the second sealing layer portion 58b are made of the same material as the sealing layer 8. The first sealing layer portion 58a and the second sealing layer portion 58b have a frame-like shape. The metal intermediate layer 53 also has a frame-like shape. The overall shape of the first sealing layer portion 58a, the metal intermediate layer 53, and the second sealing layer portion 58b is the same as that of the sealing layer 8.

[0103] The metal intermediate layer 53 can be made of the same material as the first current collector layer 6 and the second current collector layer 7. Therefore, the material of the metal intermediate layer 53 can be, for example, a metal material such as aluminum, titanium, silver, copper, stainless steel (SUS), or an alloy thereof. The material of the metal intermediate layer 53 is preferably SUS, and more preferably SUS430. Note that the metal intermediate layer 53, the first current collector layer 6, and the second current collector layer 7 may be made of different materials.

[0104] In this embodiment, the wiring conductor 52 provided between the negative electrode layers 5 of the two energy storage elements 2 is electrically connected to the negative electrode terminal 54 via the metal intermediate layer 53. Other points are the same as those in the first embodiment.

[0105] As in the fifth embodiment, a metal intermediate layer 53 may be provided between the first sealing layer portion 58 a and the second sealing layer portion 58 b. In particular, when the energy storage elements 2 are stacked in the internal space 1 a of the all-solid-state secondary battery 51 as in the fifth embodiment, the thickness of the sealing layer needs to be increased, which poses a problem of increased thermal stress. In this case, by providing the metal intermediate layer 53 between the first sealing layer portion 58 a and the second sealing layer portion 58 b as in the fifth embodiment, the thermal stress can be further reduced.

[0106] The ratio of the sum of the thicknesses of first sealing layer portion 58a and second sealing layer portion 58b to the thickness of metal intermediate layer 53 (sealing layer / metal intermediate layer) is preferably 0.001 or more, more preferably 0.01 or more, even more preferably 0.1 or more, and is preferably 1000 or less, more preferably 100 or less, even more preferably 10 or less. When the ratio (sealing layer / metal intermediate layer) is equal to or greater than the above lower limit, the bonding strength between the sealing layer and the current collector layer can be further increased. When the ratio (sealing layer / metal intermediate layer) is equal to or less than the above upper limit, thermal stress can be further reduced.

[0107] The thickness of each of first sealing layer portion 58 a and second sealing layer portion 58 b can be, for example, 1 μm or more and 100 mm or less. The thickness of each of first sealing layer portion 58 a and second sealing layer portion 58 b is preferably 1 μm or more, more preferably 10 μm or more, and even more preferably 100 μm or more, and is preferably 100 mm or less, more preferably 10 mm or less, and even more preferably 1 mm or less.

[0108] The thickness of the metal intermediate layer 53 can be, for example, 1 μm or more and 100 mm or less. The thickness of the metal intermediate layer 53 is preferably 1 μm or more, more preferably 10 μm or more, and even more preferably 100 μm or more, and is preferably 100 mm or less, more preferably 10 mm or less, and even more preferably 1 mm or less.

[0109] Sixth Embodiment FIG. 8 is a schematic cross-sectional view showing an all-solid-state secondary battery according to a sixth embodiment of the present invention.

[0110] 8 , an all-solid-state secondary battery 61 of the sixth embodiment does not have the metal intermediate layer 53 of the fifth embodiment, and has a sealing layer 8 similar to that of the first embodiment. In the all-solid-state secondary battery 61, a wiring conductor 62 provided between the negative electrode layers 5 of two energy storage elements 2 is provided so as to penetrate the sealing layer 8, and also serves as the negative electrode terminal 54 of the fifth embodiment. Other points are the same as those of the fifth embodiment.

[0111] When a plurality of energy storage elements 2 are stacked as in the sixth embodiment, the metal intermediate layer 53 as in the fifth embodiment may not be provided. In this case, the wiring conductor 62 is provided so as to penetrate the sealing layer 8, and may also serve as the negative electrode terminal 54 of the fifth embodiment.

[0112] Seventh Embodiment FIG. 9 is a schematic cross-sectional view showing an all-solid-state secondary battery according to a seventh embodiment of the present invention.

[0113] 9 , in an all-solid-state secondary battery 71 of the seventh embodiment, a through-hole 72 is provided in the first current collector layer 6. The through-hole 72 is provided as an exhaust port for evacuating the internal space 1 a in the manufacturing process of the all-solid-state secondary battery 71. The through-hole 72 may also be provided in the second current collector layer 7. The position of the through-hole 72 is not particularly limited as long as it allows the internal space 1 a to be evacuated.

[0114] The diameter of the through holes 72 is preferably 0.1 μm or more, more preferably 1 μm or more, even more preferably 10 μm or more, and is preferably 10 mm or less, more preferably 5 mm or less, and even more preferably 1 mm or less. When the diameter of the through holes 72 is equal to or greater than the above-mentioned lower limit, the internal space 1 a can be more reliably decompressed and evacuated through the through holes 72. When the diameter of the through holes 72 is equal to or less than the above-mentioned upper limit, the current collecting function of the first current collector layer 6 can be more effectively exhibited.

[0115] In this embodiment, the through-holes 72 are sealed with a sealing material. This forms a sealing portion 73 in the first current collector layer 6. In this embodiment, the sealing material forming the sealing portion 73 contains glass. When the sealing material contains glass, as in this embodiment, the all-solid-state secondary battery 71 can be used more stably in a high-temperature environment (for example, about 200°C). Note that the sealing material forming the sealing portion 73 is not particularly limited as long as it can seal the through-holes 72. The other points are the same as those in the first embodiment.

[0116] As in the seventh embodiment, the first current collector layer 6 may have a through hole 72. In this case, after the sealing layer 8 is formed, the internal space 1a can be evacuated via the through hole 72, and then the through hole 72 can be sealed. Therefore, the sealing layer 8 does not need to be formed in an evacuated state, and therefore the material of the sealing layer 8 is less likely to foam, and the resulting sealing layer 8 is less likely to become a foam. Therefore, the strength of the sealing layer 8 is less likely to decrease, and the strength of the package that seals the energy storage element 2 is also less likely to decrease. Therefore, the all-solid-state secondary battery 71 of the seventh embodiment can further improve reliability.

[0117] In the fourth to seventh embodiments, too, the outer peripheral edge of the sealing layer is disposed outward from the outer peripheral edge of the first current collector layer 6 in plan view, and therefore, it is possible to make it difficult for a short circuit to occur between a positive-electrode-side current collecting member such as a positive-electrode-side current collecting layer or tab lead and a negative-electrode-side current collecting member such as a negative-electrode-side current collecting layer or tab lead.

[0118] DESCRIPTION OF SYMBOLS 1, 21, 31, 41, 51, 61, 71... All-solid-state secondary battery 1a... Internal space 2, 22, 32... Energy storage element 2a, 3a... First main surface 2b, 3b... Second main surface 3... Solid electrolyte layer 4... Positive electrode layer 5... Negative electrode layer 6... First current collector layer 6A, 7A... Outer peripheral edge portion 6a, 7a, 8a... Outer peripheral edge 6b, 7b, 8b... Corner portion 6c... Side portion 7, 27, 37... Second current collector layer 8, 18A, 18B... Sealing layer 8A... Sealing layer forming paste 16... Positive electrode side tab lead 17... Negative electrode side tab lead 42... Spacer pin 52, 62... Wiring conductor 53... Metal intermediate layer 54... Negative electrode terminal 58a... First sealing layer portion 58b... Second sealing layer portion 72...Through hole 73...Sealing part

Claims

1. An all-solid-state secondary battery comprising: an energy storage element having a solid electrolyte layer, a positive electrode layer, and a negative electrode layer; a first current collector layer provided on one main surface of the energy storage element; a second current collector layer provided on the other main surface of the energy storage element; and a sealing layer provided between the first current collector layer and the second current collector layer and sealing the energy storage element, wherein, in a plan view, the outer periphery of the sealing layer is located outward from the outer periphery of the first current collector layer.

2. The all-solid-state secondary battery according to claim 1, wherein, in a plan view, the outer periphery of the second current collector layer is located outside the outer periphery of the sealing layer.

3. The all-solid-state secondary battery according to claim 1 or 2, wherein the corners of the first current collector layer have a rounded shape.

4. The all-solid-state secondary battery according to claim 1 or 2, wherein the corners of the second current collector layer have an R-shape, and the radius of curvature of the corners of the first current collector layer is larger than the radius of curvature of the corners of the second current collector layer.

5. The all-solid-state secondary battery according to claim 1 or 2, wherein, when the width of the sealing layer disposed outside the outer peripheral edge of the first current collector layer in a plan view is defined as an exposed width, the exposed width of the sealing layer at the corners of the first current collector layer is larger than the exposed width of the sealing layer at the sides of the first current collector layer.

6. The all-solid-state secondary battery according to claim 1 or 2, wherein, in a plan view, the sealing layer is provided at a connection point between at least one of the first current collector layer and the second current collector layer and a tab lead.

7. The all-solid-state secondary battery according to claim 1 or 2, wherein the sealing layer contains glass having a softening point of 500°C or less.

8. The sealing layer is made of Bi ２ O ３ -B ２ O ３ The all-solid-state secondary battery according to claim 7 , comprising a glass-based material.

9. The absolute value of the difference in thermal expansion coefficient between the material constituting the sealing layer and the material constituting at least one of the first current collector layer and the second current collector layer in a temperature range of 30°C to 300°C is 2.0 x 10 －６ The all-solid-state secondary battery according to claim 1 or 2, wherein the solubility is 0.1 / K or less.

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