All-solid-state secondary battery

Abstract

Provided is an all-solid-state secondary battery in which a current collector layer and an electrode layer can be reliably brought into contact with each other, and stable battery characteristics can be obtained.　An all-solid-state battery 1 comprises: 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 a main surface 2a on one side of the power storage element 2; a second current collector layer 7 provided on a main surface 2b on the other side of the power storage element 2; and a sealing layer 8 that is provided between the first current collector layer 6 and the second current collector layer 7 and seals the power storage element 2. An internal space 1a surrounded by the first current collector layer 6, second current collector layer 7, and sealing layer 8 is formed. Where the atmospheric pressure of the internal space 1a at 25°C is denoted by P1 and the atmospheric pressure of an external space at 25°C is denoted by P2, the difference between P2 and P1 (P2 - P1) is 10-100 kPa.

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] The following Patent Document 1 discloses an all-solid-state battery produced by bonding the end face of a folded seal portion with a thermosetting resin 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, as in Patent Document 1, all-solid-state batteries sealed with a resin material have the problem of being difficult to use in high-temperature environments. Furthermore, in all-solid-state secondary batteries, the contact between the electrode layer and the current collector layer to ensure electrical continuity is not always reliable, and partial or total separation may occur between the electrode layer and the current collector layer. This may result in power loss due to increased contact resistance and a decrease in battery capacity due to insufficient ion mobility.

[0006] An object of the present invention is to provide an all-solid-state secondary battery that can ensure reliable contact between a current collector layer and an electrode layer and can provide stable battery characteristics.

[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 electricity 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 electricity storage element; a second current collector layer provided on the other main surface of the electricity storage element; and a sealing layer provided between the first current collector layer and the second current collector layer and sealing the electricity storage element; an internal space surrounded by the first current collector layer, the second current collector layer, and the sealing layer; and a pressure of the internal space at 25°C is P １ and the atmospheric pressure in the external space at 25°C is P ２ When this is done, P ２ and P １ The difference between ２ -P １ ) is 10 kPa or more and 100 kPa or less.

[0009] An all-solid-state secondary battery according to a second 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 internal space is defined by the first current collector layer, the second current collector layer, and the sealing layer, and at least one of the first current collector layer and the second current collector layer is elastically deformed towards the internal space.

[0010] The all-solid-state secondary battery according to Aspect 3 is the same as Aspect 1 or Aspect 2, and preferably further includes an elastic member provided between the first current collector layer and the positive electrode layer and / or between the second current collector layer and the negative electrode layer.

[0011] In the all-solid-state secondary battery according to Aspect 4, in Aspect 3, it is preferable that the elastic member is a spring member.

[0012] In the all solid state secondary battery according to Aspect 5, in any one of Aspects 1 to 4, it is preferable that the internal space is filled with an inert gas or a mixed gas of an inert gas and a reducing gas.

[0013] In the all-solid-state secondary battery according to Aspect 6, in Aspect 5, it is preferable that the inert gas is at least one selected from the group consisting of a rare gas, a nitrogen gas, and a carbon dioxide gas.

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

[0015] An all-solid-state secondary battery according to Aspect 8 is the battery of Aspect 7, wherein the sealing layer is made of Bi ２ O ３ -B ２ O ３ ZnO-Bi based glass ２ O ３ Glass or SnO-P ２ O ５ It is preferable that the glass contains a glass-based material.

[0016] In the all-solid-state secondary battery according to Aspect 9, in any one of Aspects 1 to 8, 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 that can reliably bring the current collector layer and the electrode layer into contact with each other and can obtain stable battery characteristics.

[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 cross-sectional view showing an all-solid-state secondary battery according to an eighth embodiment of the present invention. FIG. 11 is a schematic cross-sectional view showing an all-solid-state secondary battery according to a ninth embodiment of the present invention. FIG. 12 is a graph showing the change in voltage over time in the all-solid-state secondary battery obtained in Example 1. FIG. 13 is a diagram showing the battery characteristics of the all-solid-state secondary battery obtained in Example 1.

[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 6 a of the first current collector layer 6 and the outer peripheral portion 7 a 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 1 a. The energy storage element 2 is disposed in and sealed within this internal space 1 a. 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 1 a together with the first current collector layer 6 and the second current collector layer 7 and seal the energy storage element 2.

[0028] In the all-solid-state secondary battery 1 of the first invention of the present application, the pressure in the internal space 1a at 25°C is P １ and the atmospheric pressure outside the all-solid-state secondary battery 1 (external space) at 25°C is P ２ When this is done, P ２ and P １ The difference between ２ -P １ ) is 10 kPa or more and 100 kPa or less.

[0029] In the all-solid-state secondary battery 1 according to the second aspect of the present invention, at least one of the first current collector layer 6 and the second current collector layer 7 is elastically deformed toward the internal space 1 a. In this embodiment, the first current collector layer 6 is elastically deformed toward the internal space 1 a.

[0030] Hereinafter, the first and second inventions may be collectively referred to as the present invention. The first and second inventions may be implemented either alone or in combination.

[0031] The all-solid-state secondary battery 1 of this embodiment has the above-described configuration of the present invention, and therefore can reliably bring the current collector layer (first current collector layer 6) and the electrode layer (positive electrode layer 4) into contact with each other, thereby achieving stable battery characteristics.

[0032] In conventional all-solid-state secondary batteries, the contact between the electrode layer and the current collector layer to ensure electrical continuity is not always reliable, and partial or total separation may occur between the electrode layer and the current collector layer, which may result in power loss due to increased contact resistance or a decrease in battery capacity due to current concentration.

[0033] In contrast, in the first invention, the pressure P ２ and the atmospheric pressure P １ The difference between ２ -P １) is 10 kPa or more and 100 kPa or less, the first current collector layer 6 is elastically deformed toward the internal space 1 a side. Therefore, the first current collector layer 6 and the positive electrode layer 4 can be reliably contacted with each other, power loss due to an increase in contact resistance and a decrease in battery capacity due to insufficient ion mobility are unlikely to occur, and stable battery characteristics can be obtained.

[0034] Also in the second invention, the first current collector layer 6 is elastically deformed toward the internal space 1a, so that the first current collector layer 6 and the positive electrode layer 4 can be reliably contacted with each other, and power loss due to increased contact resistance and a decrease in battery capacity due to insufficient ion mobility are unlikely to occur, thereby achieving stable battery characteristics.

[0035] In the first invention, the pressure P outside the all-solid-state secondary battery 1 at 25°C ２ and the atmospheric pressure P １ The difference between ２ -P １ ) is 10 kPa or more, preferably 20 kPa or more, more preferably 30 kPa or more, even more preferably 40 kPa or more, particularly preferably 50 kPa or more, and is 100 kPa or less, preferably 95 kPa or less, more preferably 90 kPa or less, even more preferably 85 kPa or less, particularly preferably 80 kPa or less. ２ -P １ When the value of (a) is equal to or greater than the lower limit, the current collector layer and the electrode layer can be brought into more reliable contact with each other, and more stable battery characteristics can be obtained.

[0036] In addition, as in the case where the internal space 1a of the all-solid-state secondary battery 1 is a vacuum, the pressure P ２ and the atmospheric pressure P １ The difference between ２ -P １ If the pressure P ) is too large, bubbles may be generated during the formation of the sealing layer 8, causing leakage, or the sealing layer 8 may become brittle, reducing the strength of the entire all-solid-state secondary battery 1. ２ and the atmospheric pressure P １ The difference between２ -P １ ) is preferably set to the above upper limit or less.

[0037] The internal space 1a of the all-solid-state secondary battery 1 is preferably 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 a mixture of these inert gases can also be used. 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 a mixture of these rare gases can also be used. 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.

[0038] 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.

[0039] In this embodiment, the thickness of the first current collector layer 6 is preferably 20 μm or more, more preferably 30 μm or more, 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 is equal to or greater than the above-mentioned lower limit, the current collecting function as a current collector can be further improved. On the other hand, when the thickness of the first current collector layer 6 is equal to or less than the above-mentioned upper limit, the first current collector layer 6 can be easily elastically deformed toward the internal space 1 a, and the first current collector layer 6 and the positive electrode layer 4 can be more reliably contacted with each other.

[0040] The material of the first current collector layer 6 is not particularly limited, and metal materials such as aluminum, titanium, silver, copper, stainless steel (SUS), or alloys thereof can be used. These metal materials may be used alone or in combination. The alloy is an alloy containing at least one of the above metals. From the viewpoint of reducing the thermal expansion coefficient and making the first current collector layer 6 less susceptible to damage due to temperature changes during battery operation, the material of the first current collector layer 6 is preferably SUS, and more preferably SUS430.

[0041] In this embodiment, the thickness of the second current collector layer 7 is preferably 40 μm or more, more preferably 50 μm or more, and even more preferably 100 μm or more, and is preferably 2000 μm or less, more preferably 1000 μm or less, and even more preferably 500 μm or less. When the thickness of the second current collector layer 7 is within the above range, the current collecting function as a current collector can be further improved, and the all-solid-state secondary battery 1 can be easily mounted on various devices, etc.

[0042] The material of the second current collector layer 7 is not particularly limited, and metal materials such as aluminum, titanium, silver, copper, stainless steel (SUS), or alloys thereof can be used. These metal materials may be used alone or in combination. The alloy is an alloy containing at least one of the above metals.

[0043] 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.

[0044] In this embodiment, for example, glass can be used as the material for the sealing layer 8. 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, making it easier to handle as a powder or paste.

[0045] 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%.

[0046] 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%.

[0047] 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 reduced, thereby further increasing the bonding strength.

[0048] 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.

[0049] 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, the adhesion between sealing layer 8 and at least one of first current collector layer 6 and second current collector layer 7 can be further improved. Therefore, it is desirable that both of the materials constituting first current collector layer 6 and second current collector layer 7 satisfy the above-mentioned range of absolute value of the difference in thermal expansion coefficient. Furthermore, it is preferable that the thermal expansion coefficient of the material constituting sealing layer 8 in the temperature range of 30°C to 300°C is smaller than the thermal expansion coefficient of the material constituting at least one of first current collector layer 6 and second current collector layer 7 in the temperature range of 30°C to 300°C. In this way, the bonding strength of sealing layer 8 can be further increased.

[0050] Each layer constituting the energy storage element 2 will be described in detail below.

[0051] (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.

[0052] 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 ２ The 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 O１７ , 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

[0053] 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 ３．４ Zr ０．９ Hf １．４ Al ０．６ Si １．２ P １．８ O １２ , Na ３ Zr １．７ Nb ０．２４ Si ２ P.O. １２ , Na３．６ Today ０．２ Y ０．７ 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 O １２ 、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 、No３．１ 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 Yes ２．２ P ０．８ O １２ 、No ３．５７ Zr １．７２ Yes ０．２１ Yes ２．０８ P ０．９２ O １２ 、No ３ Zr １．９８ N﹂ ０．０８Si 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 １．９ Zn 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 Zr１．８３ 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

[0054] 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.

[0055] 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.

[0056] (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 , Na ２ NiP ２ O ７ , Na ４ Fe ３ (P.O. ４ ) ２ (P ２ O ７ ) etc. can be used.

[0057] 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).

[0058] The positive electrode layer 4 may contain, in addition to the positive electrode active material, a sodium ion conductive solid electrolyte and a conductive additive. 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.

[0059] 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.

[0060] 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.

[0061] 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 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.

[0062] 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.

[0063] (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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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-mentioned lower limit, deposition of sodium metal in the anode layer 5 during charging can be suppressed, thereby further improving the cycle performance of the all-solid-state secondary battery 1. When the thickness of the anode layer 5 is equal to or less than the upper limit, the capacity and operating voltage of the all-solid-state secondary battery 1 can be further improved.

[0068] 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.

[0069] A method for manufacturing the all-solid-state secondary battery 1 will be described below.

[0070] (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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] The resin preferably has a low decomposition temperature, leaves little residue after firing, and is resistant to alteration 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).

[0079] 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) , 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) , 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.

[0080] 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 roughening 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 μm or more and 5 μm or less in terms of arithmetic mean roughness Ra.

[0081] Before applying the sealing layer-forming paste 8A, tab leads may be previously joined to the first current collector layer 6 and the second current collector layer 7 by welding, soldering, etc. The tab leads may be made of aluminum, nickel, stainless steel (SUS), etc.

[0082] If the tab lead is 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 it 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.

[0083] 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, 10 minutes or higher and 120 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.

[0084] 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 and bonded to the second current collector layer 7. When superimposing the first current collector layer 6 on the second current collector layer 7, the layers are superimposed such that the surfaces coated with the sealing layer-forming paste 8A face each other.

[0085] 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 120 minutes or shorter. The firing of the sealing layer-forming paste 8A is preferably performed in an inert gas atmosphere. Examples of the inert gas include a rare gas, nitrogen gas, and carbon dioxide gas. Of these, the inert gas is preferably a rare gas. Examples of rare gases include helium, neon, and argon. Of these, argon is preferably used as the rare gas.

[0086] 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 (PTFE).

[0087] In the manufacturing method of this embodiment, the sealing layer forming paste 8A is fired at a high temperature to form the sealing layer 8 and seal the energy storage element 2. In this way, in the manufacturing method of this embodiment, the sealing of the energy storage element 2 is performed at a high temperature, so that the air pressure in the internal space 1a is lower than the outside when the temperature is returned to room temperature. Therefore, in the obtained all-solid-state secondary battery 1, the air pressure P ２and the atmospheric pressure P １ The difference between ２ -P １ ) occurs. This is also clear from Boyle's law and Charles' law. ２ -P １ ) can be adjusted, for example, by the baking temperature during sealing, the air pressure during sealing, etc.

[0088] In the all-solid-state secondary battery 1 obtained by the manufacturing method of this embodiment, the difference (P ２ -P １ ) occurs, the first current collector layer 6 can be elastically deformed toward the internal space 1a. This allows the first current collector layer 6 and the positive electrode layer 4 to be in reliable contact with each other, making it difficult for power loss due to increased contact resistance or a decrease in battery capacity due to insufficient ion mobility to occur, thereby achieving stable battery characteristics.

[0089] Second Embodiment FIG. 4 is a schematic cross-sectional view showing an all-solid-state secondary battery according to a second embodiment of the present invention.

[0090] As shown in Fig. 4, in an all-solid-state secondary battery 21 of the second embodiment, an elastic member 22 is provided between a first current collector layer 6 and a positive electrode layer 4. As the elastic member 22, for example, a spring member can be used. Examples of materials for the elastic member 22 include SUS, steel, nickel, aluminum, copper, and titanium. Other points are the same as those of the first embodiment.

[0091] As in the second embodiment, an elastic member 22 may be provided between the first current collector layer 6 and the positive electrode layer 4. In this case, when the first current collector layer 6 is elastically deformed toward the internal space 1a, the first current collector layer 6 and the positive electrode layer 4 can be more reliably contacted via the elastic member 22. This makes it even less likely that power loss due to increased contact resistance or a decrease in battery capacity due to insufficient ion mobility will occur, and more stable battery characteristics can be obtained.

[0092] Third Embodiment 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] 5 , in the all-solid-state secondary battery 31 of the third embodiment, the second current collector layer 37 also elastically deforms toward the internal space 1a. This allows the second current collector layer 37 to be in more secure contact with the negative electrode layer 5. In this case, the elastic member 22 as in the second embodiment may also be provided between the second current collector layer 37 and the negative electrode layer 5.

[0094] In the third embodiment, the thickness of the second current collector layer 37 is preferably 20 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 second current collector layer 37 is equal to or greater than the above-mentioned lower limit, the current collecting function as a current collector can be further improved. On the other hand, when the thickness of the second current collector layer 37 is equal to or less than the above-mentioned upper limit, the second current collector layer 37 can be more easily elastically deformed toward the internal space 1 a, and the second current collector layer 37 and the negative electrode layer 5 can be more reliably contacted. Other points are the same as those of the first embodiment.

[0095] As in the third embodiment, the second current collector layer 37 may also be elastically deformed toward the internal space 1 a. However, from the viewpoint of facilitating mounting of the all-solid-state secondary battery in various devices, it is desirable that the second current collector layer 7 is not elastically deformed toward the internal space 1 a, as in the all-solid-state secondary battery 1 of the first embodiment.

[0096] (Fourth and Fifth Embodiments) Fig. 6 is a schematic cross-sectional view showing an all-solid-state secondary battery according to a fourth embodiment of the present invention, and Fig. 7 is a schematic cross-sectional view showing an all-solid-state secondary battery according to a fifth embodiment of the present invention.

[0097] As shown in Fig. 6, in an all-solid-state secondary battery 41 of the fourth embodiment, a second current collector layer 47 has a container-like shape. An energy storage element 42 is mounted inside this container-like second current collector layer 47. In the energy storage element 42, 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 47 side. A sealing layer 8 is provided on the upper surface of the container-like second current collector layer 47 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 47. Other points are the same as those of the first embodiment.

[0098] As shown in FIG. 7 , in an all-solid-state secondary battery 51 of the fifth embodiment, a second current collector layer 57 is drawn into a rectangular tube shape. An energy storage element 52 is mounted inside the second current collector layer 57 drawn into this rectangular tube shape. In the energy storage element 52, 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 57 side. A sealing layer 8 is provided on the upper surface of the second current collector layer 57 drawn into a rectangular tube 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 57 drawn into a rectangular tube shape. Other points are the same as those of the first embodiment.

[0099] In the fourth and fifth embodiments, the first current collector layer 6 is also elastically deformed toward the internal space 1 a. Therefore, in the all-solid-state secondary battery 41 and the all-solid-state secondary battery 51, the first current collector layer 6 and the positive electrode layer can be reliably contacted, power loss due to increased contact resistance and a decrease in battery capacity due to insufficient ion mobility are unlikely to occur, and stable battery characteristics can be obtained.

[0100] 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.

[0101] As shown in Fig. 8, in an all-solid-state secondary battery 61 of the sixth embodiment, a spacer pin 62 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 62 is not particularly limited, and examples thereof include a cylindrical shape, a rectangular pillar shape, and a hollow cylinder. Examples of the spacer pin 62 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.

[0102] As in the sixth embodiment, spacer pins 62 may be provided between the first current collector layer 6 and the second current collector layer 7. By providing the spacer pins 62, the distance between the first current collector layer 6 and the second current collector layer 7 can be maintained more reliably. This makes it possible to prevent the first current collector layer 6 and the second current collector layer 7 from being excessively elastically deformed toward the energy storage element 2, thereby preventing damage to the energy storage element 2.

[0103] 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.

[0104] 9 , in an all-solid-state secondary battery 71 of the seventh 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 72 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 72 may be provided between the positive electrode layers 4 of the two energy storage elements 2.

[0105] In the all-solid-state secondary battery 71, the sealing layer 8 is composed of a first sealing layer portion 78 a and a second sealing layer portion 78 b. In the stacking direction of the energy storage element 2, a metal intermediate layer 73 is provided between the first sealing layer portion 78 a and the second sealing layer portion 78 b.

[0106] The first sealing layer portion 78a and the second sealing layer portion 78b have the same shape and material as the sealing layer 8. Therefore, the first sealing layer portion 78a and the second sealing layer portion 78b have a frame-like shape. The metal intermediate layer 73 also has a frame-like shape.

[0107] The metal intermediate layer 73 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 73 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 73 is preferably SUS, and more preferably SUS430. Note that the metal intermediate layer 73, the first current collector layer 6, and the second current collector layer 7 may be made of different materials.

[0108] In this embodiment, the wiring conductor 72 provided between the negative electrode layers 5 of the two energy storage elements 2 is electrically connected to a negative electrode terminal 74 via a metal intermediate layer 73. Other points are the same as those in the first embodiment.

[0109] As in the seventh embodiment, a metal intermediate layer 73 may be provided between the first sealing layer portion 78 a and the second sealing layer portion 78 b. In particular, when the energy storage elements 2 are stacked in the internal space 1 a of the all-solid-state secondary battery 71 as in the seventh 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 73 between the first sealing layer portion 78 a and the second sealing layer portion 78 b as in the seventh embodiment, the thermal stress can be further reduced.

[0110] The ratio of the sum of the thicknesses of first sealing layer portion 78a and second sealing layer portion 78b to the thickness of metal intermediate layer 73 (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.

[0111] The thickness of each of the first sealing layer portion 78 a and the second sealing layer portion 78 b can be, for example, 1 μm or more and 100 mm or less. The thickness of each of the first sealing layer portion 78 a and the second sealing layer portion 78 b is preferably 1 μm or more, more preferably 10 μm or more, even more preferably 100 μm or more, and preferably 100 mm or less, more preferably 10 mm or less, even more preferably 1 mm or less.

[0112] The thickness of the metal intermediate layer 73 can be, for example, 1 μm or more and 100 mm or less. The thickness of the metal intermediate layer 73 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, even more preferably 1 mm or less.

[0113] Eighth Embodiment FIG. 10 is a schematic cross-sectional view showing an all-solid-state secondary battery according to an eighth embodiment of the present invention.

[0114] 10 , an all-solid-state secondary battery 81 of the eighth embodiment does not have the metal intermediate layer 73 of the seventh embodiment, and has a sealing layer 8 similar to that of the first embodiment. In the all-solid-state secondary battery 81, a wiring conductor 82 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 74 of the seventh embodiment. Other points are the same as those of the seventh embodiment.

[0115] When a plurality of energy storage elements 2 are stacked as in the eighth embodiment, the metal intermediate layer 73 as in the seventh embodiment does not need to be provided. In this case, the wiring conductor 82 is provided so as to penetrate the sealing layer 8, and may also serve as the negative electrode terminal 74 of the seventh embodiment.

[0116] Ninth Embodiment FIG. 11 is a schematic cross-sectional view showing an all-solid-state secondary battery according to a ninth embodiment of the present invention.

[0117] 11 , in an all solid state secondary battery 91 of the ninth embodiment, a through hole 92 is provided in the first current collector layer 6. The through hole 92 is provided as an exhaust port for evacuating the internal space 1 a in the manufacturing process of the all solid state secondary battery 91. The through hole 92 may be provided in the second current collector layer 7. The position of the through hole 92 is not particularly limited as long as it allows the internal space 1 a to be evacuated.

[0118] The diameter of the through holes 92 is preferably 0.1 μm or more, more preferably 1 μm or more, and 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 92 is equal to or greater than the above-mentioned lower limit, the interior space 1 a can be more reliably decompressed and evacuated through the through holes 92. When the diameter of the through holes 92 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.

[0119] In this embodiment, the through-holes 92 are sealed with a sealing material. This forms a sealing portion 93 in the first current collector layer 6. In this embodiment, the sealing material forming the sealing portion 93 contains glass. When the sealing material contains glass, as in this embodiment, the all-solid-state secondary battery 91 can be used more stably in a high-temperature environment (for example, about 200°C). Note that the sealing material forming the sealing portion 93 is not particularly limited as long as it can seal the through-holes 92. The other points are the same as those in the first embodiment.

[0120] As in the ninth embodiment, a through hole 92 may be provided in the first current collector layer 6. In this case, after forming the sealing layer 8, the internal space 1 a can be evacuated via the through hole 92, and then the through hole 92 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 91 of the ninth embodiment can further improve reliability.

[0121] The present invention will be described in more detail below with reference to specific examples. The present invention is not limited to the following examples, and can be practiced with appropriate modifications within the scope of the present invention.

[0122] Example 1 In Example 1, an all-solid-state secondary battery 1 shown in Fig. 1 and Fig. 2 was fabricated. Specifically, first, SUS plates (length: 60 mm, width: 50 mm, thickness: 0.05 mm, thermal expansion coefficient: 11 × 10) were prepared as the first current collector layer 6 and the second current collector layer 7. －６ Next, a sealing layer forming paste (Bi) was applied to the sealing portions of the outer peripheral portion 6 a of the first current collector layer 6 and the outer peripheral portion 7 a of the second current collector layer 7. ２ O ３ -B ２ O ３ Glass, thermal expansion coefficient: 10.5 x 10 －６ A 2.5 g paste (containing 2.5 g of 1000 kJ / K (30°C to 300°C), including an organic binder) was applied to a frame-like shape using a dispenser coater with a width of 4 mm and a coating amount of 2.5 g, and then dried at 120°C for 30 minutes. After drying, the sealing layer-forming paste was pre-fired at 460°C for 20 minutes. Next, the energy storage element 2 was mounted on the second current collector layer 7, and the first current collector layer 6 was superimposed on the second current collector layer 7 so that the surfaces coated with the sealing layer-forming paste overlapped. Next, after argon vacuum substitution, the pressure was replaced with 1 atmosphere, and the temperature was maintained at 460°C for 1 hour while argon gas was flowed to form a sealing layer 8, thereby obtaining an all-solid-state secondary battery 1.

[0123] In Example 2, the all-solid-state secondary battery 1 shown in FIGS. 1 and 2 was fabricated. Specifically, first, SUS plates (length: 16 mm, width: 15 mm, thickness: 0.1 mm, thermal expansion coefficient: 11×10) were prepared as the first current collector layer 6 and the second current collector layer 7. －６ Next, a sealing layer forming paste (Bi) was applied to the sealing portions of the outer peripheral portion 6 a of the first current collector layer 6 and the outer peripheral portion 7 a of the second current collector layer 7. ２ O ３ -B ２ O ３ Glass, thermal expansion coefficient: 10.5 x 10 －６A 0.2 g coating of 0.7 mm thick PET / K (30°C to 300°C), including an organic binder, was applied to a frame-like shape using a dispenser coater, and the coating was dried at 120°C for 30 minutes. After drying, the sealing layer-forming paste was pre-fired at 460°C for 20 minutes. Next, the energy storage element 2 was mounted on the second current collector layer 7, and the first current collector layer 6 was superimposed on the second current collector layer 7 so that the surfaces coated with the sealing layer-forming paste overlapped. Next, after argon vacuum substitution, the temperature was maintained at 460°C for 1 hour while flowing argon gas to achieve 1 atmosphere, forming a sealing layer 8, and an all-solid-state secondary battery 1 was obtained.

[0124] Example 3 In Example 3, an all-solid-state secondary battery 21 shown in FIG. 4 was fabricated. Specifically, first, SUS plates (length: 60 mm, width: 50 mm, thickness: 0.1 mm, thermal expansion coefficient: 11×10) were prepared as the first current collector layer 6 and the second current collector layer 7. －６ Next, a sealing layer forming paste (Bi) was applied to the sealing portions of the outer peripheral portion 6 a of the first current collector layer 6 and the outer peripheral portion 7 a of the second current collector layer 7. ２ O ３ -B ２ O ３ Glass, thermal expansion coefficient: 10.5 x 10 －６ A 2.5 g paste (containing 2.5 g of 1000 kJ / K (30°C to 300°C), including an organic binder) was applied to a frame-shaped substrate using a dispenser coater with a width of 4 mm and a coating amount of 2.5 g, and then dried at 120°C for 30 minutes. After drying, the sealing layer-forming paste was pre-fired at 460°C for 20 minutes. Next, the energy storage element 2 was mounted on the second current collector layer 7, a SUS elastic member 22 was mounted on the energy storage element 2, and the first current collector layer 6 was superimposed on the second current collector layer 7 so that the coated surfaces of the sealing layer-forming paste overlapped. Next, after argon vacuum substitution, the pressure was replaced with 1 atmosphere, and the temperature was maintained at 460°C for 1 hour while argon gas was flowed to form a sealing layer 8, thereby obtaining an all-solid-state secondary battery 21.

[0125] Comparative Example 1 Comparative Example 1 was designed to have the same configuration as the all-solid-state secondary battery 21 shown in FIG. 4. Specifically, first, nickel plates (length: 60 mm, width: 50 mm, thickness: 0.1 mm, thermal expansion coefficient: 13×10) were prepared as the first current collector layer 6 and the second current collector layer 7.－６ Next, a sealing layer forming paste (Bi) was applied to the sealing portions of the outer peripheral portion 6 a of the first current collector layer 6 and the outer peripheral portion 7 a of the second current collector layer 7. ２ O ３ -B ２ O ３ Glass, thermal expansion coefficient: 10.5 x 10 －６ A 2.5 g coating of 1000 kJ / K (30°C to 300°C), including an organic binder, was applied to a frame-shaped substrate using a dispenser coater with a width of 4 mm and a coating amount of 2.5 g, and then dried at 120°C for 30 minutes. After drying, the sealing layer-forming paste was pre-fired at 460°C for 20 minutes. Next, the energy storage element 2 was mounted on the second current collector layer 7, a SUS elastic member 22 was mounted on the energy storage element 2, and the first current collector layer 6 was superimposed on the second current collector layer 7 so that the coated surfaces of the sealing layer-forming paste overlapped. Next, after argon vacuum substitution, the pressure was replaced with 1 atmosphere, and the temperature was maintained at 460°C for 1 hour while argon gas was flowed to form a sealing layer 8, thereby obtaining an all-solid-state secondary battery.

[0126] Comparative Example 2 Comparative Example 2 was designed to have the same configuration as the all-solid-state secondary battery 1 shown in FIGS. 1 and 2. Specifically, first, SUS plates (length: 60 mm, width: 50 mm, thickness: 0.05 mm, thermal expansion coefficient: 11×10) were prepared as the first current collector layer 6 and the second current collector layer 7. －６ Next, a sealing layer forming paste (Bi) was applied to the sealing portions of the outer peripheral portion 6 a of the first current collector layer 6 and the outer peripheral portion 7 a of the second current collector layer 7. ２ O ３ -B ２ O ３ Glass, thermal expansion coefficient: 10.5 x 10 －６A 2.5 g coating of 1000kJ / K (30°C to 300°C), including an organic binder, was applied to a frame-like shape using a dispenser coater with a width of 4 mm and a coating amount of 2.5 g, and then dried at 120°C for 30 minutes. After drying, the sealing layer-forming paste was pre-fired at 460°C for 20 minutes. Next, the energy storage element 2 was mounted on the second current collector layer 7, and the first current collector layer 6 was superimposed on the second current collector layer 7 so that the surfaces coated with the sealing layer-forming paste overlapped. Next, after argon vacuum substitution, the container was sealed with argon gas to 2.5 atmospheres, and the container was maintained at 460°C for 1 hour to form a sealing layer 8, thereby obtaining an all-solid-state secondary battery.

[0127] Comparative Example 3 Comparative Example 3 was designed to have the same configuration as the all-solid-state secondary battery 1 shown in FIGS. 1 and 2. Specifically, first, SUS plates (length: 60 mm, width: 50 mm, thickness: 0.1 mm, thermal expansion coefficient: 11×10) were prepared as the first current collector layer 6 and the second current collector layer 7. －６ Next, a sealing layer forming paste (Bi) was applied to the sealing portions of the outer peripheral portion 6 a of the first current collector layer 6 and the outer peripheral portion 7 a of the second current collector layer 7. ２ O ３ -B ２ O ３ Glass, thermal expansion coefficient: 10.5 x 10 －６ A 2.5 g coating of 1000kJ / K (30°C to 300°C), including an organic binder, was applied to a frame-like shape using a dispenser coater with a width of 4 mm and a coating amount of 2.5 g, and then dried at 120°C for 30 minutes. After drying, the sealing layer-forming paste was pre-fired at 460°C for 20 minutes. Next, the energy storage element 2 was mounted on the second current collector layer 7, and the first current collector layer 6 was superimposed on the second current collector layer 7 so that the surfaces coated with the sealing layer-forming paste overlapped. Next, the pressure was evacuated to 0.1 Pa, and the temperature was maintained at 460°C for 1 hour to form a sealing layer 8, thereby obtaining an all-solid-state secondary battery.

[0128] [Evaluation] (Differential Pressure Evaluation) An all-solid-state secondary battery was placed in a vacuum vessel that transmits laser light in a laser-type height measuring instrument, and the pressure inside the vacuum vessel when the total thickness of the all-solid-state secondary battery changed was measured as the atmospheric pressure P １ Considering that, atmospheric pressure P ２In the all-solid-state secondary batteries 1 and 21 obtained in Examples 1 to 3, the pressure P ２ and the atmospheric pressure P １ The difference between ２ -P １ In the all-solid-state secondary battery obtained in Comparative Example 1, sealing was not possible due to mismatching of the thermal expansion coefficient, so the difference (P ２ -P １ In the all-solid-state secondary battery obtained in Comparative Example 2, sealing was possible, but the difference (P ２ -P １ ) was 0 kPa. In the all-solid-state secondary battery obtained in Comparative Example 3, the difference (P ２ -P １ ) was 101 kPa.

[0129] (Voltage Evaluation) Fig. 12 is a diagram showing the time change of the voltage in the all-solid-state secondary battery 1 obtained in Example 1. In Fig. 12, Example 1 is described as having a differential pressure of 60 kPa. For comparison, Fig. 12 also shows a comparison example 3 of a vacuum-sintered product and a differential pressure (P ２ -P １ ) is 0 kPa (differential pressure: 0 kPa).

[0130] (Battery characteristic evaluation) Fig. 13 is a diagram showing the battery characteristics of the all solid state secondary battery 1 obtained in Example 1. In Fig. 13, the charge / discharge capacity of the all solid state secondary battery 1 was evaluated by a constant current charge / discharge test at an ambient temperature of 200°C. The coulombic efficiency of the all solid state secondary battery 1 was evaluated by the ratio of the discharge capacity to the charge capacity in the constant current charge / discharge test.

[0131] As is clear from Fig. 12 and Fig. 13, it was confirmed that stable battery characteristics were obtained in the all-solid-state secondary battery 1 obtained in Example 1. It was also confirmed that stable battery characteristics similar to those in Example 1 were obtained in the all-solid-state secondary batteries 1 and 21 obtained in Examples 2 and 3. On the other hand, the all-solid-state secondary batteries obtained in Comparative Examples 1 and 2 did not function as batteries due to insufficient contact between the current collector and the energy storage element. The all-solid-state secondary battery obtained in Comparative Example 3 did not function as a battery due to damage to the sealing portion and leakage during the process of raising the ambient temperature to 200°C.

[0132] DESCRIPTION OF SYMBOLS 1, 21, 31, 41, 51, 61, 71, 81, 91... All-solid-state secondary battery 1a... Internal space 2, 42, 52... 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 7, 37, 47, 57... Second current collector layer 8... Sealing layer 8A... Sealing layer forming paste 22... Elastic member 62... Spacer pin 72, 82... Wiring conductor 73... Metal intermediate layer 74... Negative electrode terminal 78a... First sealing layer portion 78b... Second sealing layer portion 92... Through hole 93... Sealing portion

Claims

1. An electric storage device comprising: an electric 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 electric storage element; a second current collector layer provided on the other main surface of the electric storage element; and a sealing layer provided between the first current collector layer and the second current collector layer and sealing the electric storage element; wherein an internal space is defined by the first current collector layer, the second current collector layer, and the sealing layer; and the pressure of the internal space at 25°C is P １ and the atmospheric pressure in the external space at 25°C is P ２ When this is done, P ２ and P １ The difference between ２ -P １ ) is 10 kPa or more and 100 kPa or less.

2. 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 an internal space is defined by the first current collector layer, the second current collector layer, and the sealing layer, and at least one of the first current collector layer and the second current collector layer is elastically deformed towards the internal space.

3. The all-solid-state secondary battery according to claim 1 or 2, wherein an elastic member is provided between the first current collector layer and the positive electrode layer and / or between the second current collector layer and the negative electrode layer.

4. The all-solid-state secondary battery according to claim 3, wherein the elastic member is a spring member.

5. The all-solid-state secondary battery according to claim 1 or 2, wherein the internal space is filled with an inert gas or a mixed gas of an inert gas and a reducing gas.

6. The all-solid-state secondary battery according to claim 5, wherein the inert gas is at least one selected from the group consisting of a rare gas, nitrogen gas, and carbon dioxide gas.

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 ZnO-Bi based glass ２ O ３ Glass or SnO-P ２ O ５ 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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