Solid battery

Abstract

To provide a solid state battery with an exterior material that has excellent water vapor barrier properties and mechanical strength.SOLUTION: A solid state battery 1 includes a battery body 2 including a positive electrode layer 11 and a negative electrode layer 12 laminated via a solid electrolyte layer 13, and an exterior material 3 covering a surface of the battery body 2, and the exterior material 3 is a sintered body containing a vitreous material and at least two crystalline materials, and the vitreous material and the crystalline material contain at least one kind of a common element.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a solid battery. More specifically, the present invention relates to a laminated solid battery in which each layer constituting a battery constituent unit is laminated.

Background Art

[0002] Conventionally, secondary batteries capable of repeated charge and discharge have been used in various applications. For example, secondary batteries are used as power sources for electronic devices such as smartphones and notebook computers.

[0003] In secondary batteries, a liquid electrolyte (electrolyte solution) such as an organic solvent has been conventionally used as a medium for moving ions. However, in secondary batteries using an electrolyte solution, there are problems such as leakage of the electrolyte solution. Therefore, the development of solid batteries having a solid electrolyte instead of the liquid electrolyte has been promoted.

[0004] On the other hand, as an exterior material for covering a battery element which is a power generation element of a solid battery, a resin material has been proposed (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, exterior materials made of resin materials have a problem that the effect of suppressing the intrusion of water vapor in the ambient atmosphere into the battery element (hereinafter referred to as water vapor barrier property) is not sufficient. When the water vapor barrier property is low, moisture intrudes into the inside of the battery element, and the positive electrode layer, negative electrode layer, and solid electrolyte layer absorb the moisture, resulting in a decrease in battery performance. On the other hand, the inventors of the present invention examined an exterior material using a glass material. Although the water vapor barrier property is improved compared to the exterior material using a resin material, it is still insufficient for practical use, and the mechanical strength is also insufficient.

[0007] Therefore, an object of the present invention is to provide a solid battery including an exterior material excellent in water vapor barrier property and mechanical strength.

Means for Solving the Problems

[0008] In order to solve the above problems, a solid battery according to an aspect of the present invention includes a battery element including a positive electrode layer and a negative electrode layer laminated via a solid electrolyte layer, and an exterior material covering the surface of the battery element. The exterior material is a sintered body including a glassy material and at least two crystalline materials, and is characterized in that the glassy material and the crystalline materials contain at least one common element.

[0009] Further, a solid battery according to another aspect of the present invention includes a battery element including a positive electrode layer and a negative electrode layer laminated via a solid electrolyte layer, and an exterior material covering the surface of the battery element. The exterior material is a sintered body including a glassy material and at least one crystalline material, and is characterized in that the volume fraction of the crystalline material with respect to the sintered body is 40% by volume or more and 99% by volume or less.

Effects of the Invention

[0010] According to the present invention, it is possible to provide a solid battery including an exterior material excellent in water vapor barrier property and mechanical strength.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0012] Hereinafter, the "solid-state battery" of the present invention will be described in detail. Although the description will be made with reference to the drawings as necessary, the illustrated content is only schematically and exemplarily shown for the understanding of the present invention, and the appearance, dimensional ratios, etc. may be different from the actual ones.

[0013] As used in the present invention, the "solid battery" generally refers to a battery whose components are composed of solids, and more specifically refers to an all-solid battery whose battery components (particularly preferably all battery components) are composed of solids. In a preferred embodiment, the solid battery in the present invention is a laminated solid battery configured such that each layer forming a battery component unit is laminated on top of each other, and preferably each such layer is made of a sintered body. Note that the "solid battery" includes not only so-called "secondary batteries" that can be repeatedly charged and discharged, but also "primary batteries" that can only be discharged. According to a preferred embodiment of the present invention, the "solid battery" is a secondary battery. The "secondary battery" is not to be overly restricted by its name and may include, for example, power storage devices.

[0014] As used in this specification, "plan view" is based on the form when the object is viewed from above or below along the thickness direction based on the lamination direction of each layer constituting the solid battery. Also, as used in this specification, "cross-sectional view" is based on the form when viewed from a direction substantially perpendicular to the thickness direction based on the lamination direction of each layer constituting the solid battery (specifically, the form when cut along a plane parallel to the thickness direction). The "vertical direction" and "horizontal direction" directly or indirectly used in this specification correspond to the vertical direction and horizontal direction in the figure, respectively. Unless otherwise specified, the same reference numerals or symbols indicate the same members, parts, or the same meaning content. In a preferred embodiment, it can be understood that the vertically downward direction (i.e., the direction in which gravity acts) corresponds to the "downward direction", and the opposite direction corresponds to the "upward direction".

[0015] All various numerical ranges mentioned in this specification are intended to include the numerical values of the lower and upper limits themselves, unless otherwise specified. That is, for example, taking a numerical range of 1 to 10 as an example, unless there is an additional specific explanation, it can be interpreted as including the lower limit value of "1" and also the upper limit value of "10".

[0016] Embodiment 1 The solid-state battery according to this embodiment includes a battery element including a positive electrode layer and a negative electrode layer laminated via a solid electrolyte, and an exterior member covering the surface of the battery element. The exterior member is a sintered body including a glassy material and at least two crystalline materials, and is characterized in that the glassy material and the crystalline materials contain at least one common element.

[0017] FIG. 1 is a partially cutaway schematic perspective view showing an example of the structure of a solid-state battery 1 according to Embodiment 1. The solid-state battery 1 includes a battery element 2, an exterior member 3, a positive electrode terminal 4, and a negative electrode terminal 5. The battery element 2 has a laminate structure in which a positive electrode layer 11 and a negative electrode layer 12 are laminated via a solid electrolyte layer 13. Further, the battery element 2 has a first end face (not shown) and a second end face (not shown) located on opposite sides of each other, and a peripheral surface disposed between the first end face and the second end face. The end face of the positive electrode layer 11 is exposed on the first end face, and the end face of the negative electrode layer 12 is exposed on the second end face. The exterior member 3 is provided so as to cover the peripheral surface of the battery element 2. Further, the positive electrode terminal 4 covers the first end face of the battery element 2, covers the first end face side of the peripheral surface of the battery element 2 via the exterior member 3, and is electrically connected to the positive electrode layer 11. Further, the negative electrode terminal 5 covers the second end face of the battery element 2, covers the second end face side of the peripheral surface of the battery element 2 via the exterior member 3, and is electrically connected to the negative electrode layer 12. Note that electrode separation portions 14 are provided on the first end face and the second end face, respectively, to prevent the positive electrode terminal 4 and the negative electrode layer 12 from directly contacting each other on the first end face, and to prevent the negative electrode terminal 5 and the positive electrode layer 11 from directly contacting each other on the second end face. In the figure, T indicates the height direction of the solid-state battery 1, L indicates the length direction of the solid-state battery 1, and W indicates the width direction of the solid-state battery 1.

[0018] The solid-state battery according to this embodiment includes a battery element (hereinafter also referred to as a solid-state battery laminate) including at least one battery constituent unit including a positive electrode layer, a negative electrode layer, and a solid electrolyte layer interposed therebetween along the stacking direction, and an exterior member covering the surface of the battery element.

[0019] In a solid-state battery, when each layer constituting it is formed by firing, layers such as a positive electrode layer, a negative electrode layer, and a solid electrolyte constitute a sintered layer. Preferably, the positive electrode layer, the negative electrode layer, and the solid electrolyte are integrally fired with each other, and thus the solid-state battery laminate constitutes an integral sintered body.

[0020] The positive electrode layer is an electrode layer containing at least a positive electrode active material. The positive electrode layer may further contain a solid electrolyte. For example, the positive electrode layer is composed of a sintered body containing at least positive electrode active material particles and solid electrolyte particles. In one preferred embodiment, the positive electrode layer is composed of a sintered body substantially containing only positive electrode active material particles and solid electrolyte particles. On the other hand, the negative electrode layer is an electrode layer containing at least a negative electrode active material. The negative electrode layer may further contain a solid electrolyte. For example, the negative electrode layer is composed of a sintered body containing at least negative electrode active material particles and solid electrolyte particles. In one preferred embodiment, the negative electrode layer is composed of a sintered body substantially containing only negative electrode active material particles and solid electrolyte particles.

[0021] The positive electrode active material and the negative electrode active material are substances involved in the transfer of electrons in a solid-state battery. Through the solid electrolyte, ions move (conduct) between the positive electrode layer and the negative electrode layer, and charge and discharge are performed by the transfer of electrons. The positive electrode layer and the negative electrode layer are preferably layers capable of occluding and releasing sodium ions or lithium ions, preferably lithium ions, as ions. That is, the solid-state battery is preferably an all-solid-state secondary battery in which sodium ions or lithium ions move between the positive electrode layer and the negative electrode layer through the solid electrolyte to perform charge and discharge of the battery.

[0022] (Positive electrode active material) Examples of the cathode active material capable of occluding and releasing lithium ions include at least one selected from the group consisting of a lithium-containing phosphate compound having a NASICON-type structure, a lithium-containing phosphate compound having an olivine-type structure, a lithium-containing layered oxide, and a lithium-containing oxide having a spinel-type structure. Examples of the lithium-containing phosphate compound having a NASICON-type structure include Li3V2(PO4)3. Examples of the lithium-containing phosphate compound having an olivine-type structure include LiFePO4, LiMnPO4, etc. Examples of the lithium-containing layered oxide include LiCoO2, LiCo 1 / 3 Ni 1 / 3 Mn 1 / 3 O2, etc. Examples of the lithium-containing oxide having a spinel-type structure include LiMn2O4, LiNi 0.5 Mn 1.5 O4, etc.

[0023] Examples of the cathode active material capable of occluding and releasing sodium ions include at least one selected from the group consisting of sodium-containing phosphate compounds such as Na3V2(PO4)3, NaCoFe2(PO4)3, Na2Ni2Fe(PO4)3, Na3Fe2(PO4)3, Na2FeP2O7, Na4Fe3(PO4)2(P2O7), and a sodium-containing layered oxide such as NaFeO2.

[0024] (Anode active material) Examples of the negative electrode active material capable of occluding and releasing lithium ions include, for example, oxides containing at least one element selected from the group consisting of Ti, Si, Sn, Cr, Fe, Nb, and Mo, graphite-lithium compounds, lithium alloys, lithium-containing phosphate compounds having a NASICON structure, lithium-containing phosphate compounds having an olivine structure, and lithium-containing oxides having a spinel structure. Examples of the lithium alloy include Li-Al and the like. Examples of the lithium-containing phosphate compound having a NASICON structure include Li3V2(PO4)3, LiTi2(PO4)3, and the like. Examples of the lithium-containing phosphate compound having an olivine structure include LiCuPO4 and the like. Examples of the lithium-containing oxide having a spinel structure include Li4Ti5O 12 and the like.

[0025] Examples of the negative electrode active material capable of occluding and releasing sodium ions include at least one selected from the group consisting of sodium-containing phosphate compounds and transition metal oxides.

[0026] The positive electrode layer and / or the negative electrode layer may contain a conductive assistant. Examples of the conductive assistant contained in the positive electrode layer and the negative electrode layer include at least one selected from metal materials such as silver, palladium, gold, platinum, aluminum, copper, and nickel, and carbon.

[0027] Furthermore, the positive electrode layer and / or the negative electrode layer may contain a sintering assistant. Examples of the sintering assistant include at least one selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, boron oxide, silicon oxide, bismuth oxide, and phosphorus oxide.

[0028] The thicknesses of the positive electrode layer and the negative electrode layer are not particularly limited, and for example, they may each independently be 2 μm or more and 50 μm or less, particularly 5 μm or more and 30 μm or less.

[0029] (Solid electrolyte) A solid electrolyte is a substance that can conduct sodium ions or lithium ions. In particular, the solid electrolyte that forms a battery constituent unit in a solid battery forms a layer that can conduct sodium ions or lithium ions between the positive electrode layer and the negative electrode layer. Note that the solid electrolyte only needs to be provided at least between the positive electrode layer and the negative electrode layer. That is, the solid electrolyte may also exist around the positive electrode layer and / or the negative electrode layer so as to protrude from between the positive electrode layer and the negative electrode layer. Examples of the solid electrolyte that can conduct lithium ions include, for example, lithium-containing polyanion-based compounds having a NASICON structure, oxides having a perovskite structure, oxides having a garnet type or a garnet type similar structure, and the like. Examples of the lithium-containing polyanion-based compound having a NASICON structure include, for example, a lithium-containing phosphate compound, Li x M y (PO4)3 (1 ≤ x ≤ 2, 1 ≤ y ≤ 2, M is at least one selected from the group consisting of Ti, Ge, Al, Ga, and Zr). An example of the lithium-containing phosphate compound having a NASICON structure is, for example, Li 1.2 Al 0.2 Ti 1.8 (PO4)3 and the like. An example of the oxide having a perovskite structure is La 0.55 Li 0.35 TiO3 and the like. An example of the oxide having a garnet type or a garnet type similar structure is Li7La3Zr2O 12 and the like. Further, examples of the solid electrolyte that can conduct sodium ions include, for example, sodium-containing phosphate compounds having a NASICON structure. Examples of the sodium-containing phosphate compound having a NASICON structure include Na x M y (PO4)3 (1 ≤ x ≤ 4, 1 ≤ y ≤ 2, M is at least one selected from the group consisting of Zr, Ti, Ge, Al, Ga, Fe, etc., and a part of P may be substituted with Si, S, etc.).

[0030] The solid electrolyte layer may contain a sintering aid. The sintering aid contained in the solid electrolyte layer may be selected from the same materials as the sintering aids that may be contained in the positive electrode layer and / or the negative electrode layer, for example.

[0031] The thickness of the solid electrolyte layer is not particularly limited, and may be, for example, 1 μm or more and 15 μm or less, particularly 1 μm or more and 5 μm or less.

[0032] (Outer packaging material) The outer packaging material is generally formed on the outermost side of the solid battery and is for electrical, physical, and / or chemical protection. The outer packaging material used for the solid battery according to the present embodiment is a sintered body containing a glassy material and at least two crystalline materials, and the glassy material and the crystalline material contain at least one common element. It is difficult to obtain a fired body composed only of a glassy material that is stronger than a crystalline material mechanically or chemically. In the present invention, by containing a common element, the crystalline material and the glassy material are strongly joined, making it easier to form a denser fired body than a single glass, and furthermore, the mechanical strength and chemical stability of the fired body are improved. Thereby, it becomes possible to improve the water vapor barrier property and mechanical strength of the outer packaging material.

[0033] The common element contained in the glassy material and the crystalline material is at least one selected from the group consisting of Zn, Al, Si, and Mg, and preferably Zn or Al.

[0034] Examples of the glassy material include borosilicate glass containing at least one selected from the group consisting of Zn, Al, Si, and Mg. Preferably, it is borosilicate glass containing Zn and / or Al.

[0035] In addition, examples of the crystalline material include at least two selected from the group consisting of alumina (Al2O3), magnesium oxide (MgO), silicon monoxide (SiO), silicon dioxide (SiO2), gahnite (ZnAl2O4), forsterite (Mg2SiO4), wollastonite (CaSiO3), anorthite (CaAl2Si2O8), kyanite (Al2SiO5), sillimanite (Al2SiO5), and andalusite (Al2SiO5). Preferably, they are at least two selected from the group consisting of alumina (Al2O3), gahnite (ZnAl2O4), forsterite (Mg2SiO4), magnesium oxide (MgO), silicon monoxide (SiO), and silicon dioxide (SiO2). More preferably, they are alumina (Al2O3) and gahnite (ZnAl2O4), or alumina (Al2O3) and forsterite (Mg2SiO4). Here, as common elements, alumina contains Al, magnesium oxide contains Mg, silicon monoxide and silicon dioxide contain Si, gahnite contains Zn and Al, forsterite contains Si and Mg, wollastonite contains Si, anorthite contains Al and Si, and kyanite, sillimanite, and andalusite contain Al and Si.

[0036] The sintered body used in this embodiment can be prepared by mixing a glassy material and a crystalline material at a predetermined mixing ratio, adding an organic material and a solvent and mixing them to form a paste, and applying the paste to a predetermined substrate and firing it. Also, a paste can be prepared using raw material powders that become a glassy material and a crystalline material by firing. As the raw material powders that become a glassy material and a crystalline material, for example, devitrified glass powder can be used. Further, a mixture obtained by mixing a crystalline material with the devitrified glass powder as needed may be used as the raw material powder.

[0037] In addition, the crystalline material has a particulate shape. The particles of the crystalline material (hereinafter also referred to as crystalline particles) are preferably dispersed in the vitreous material. The average particle size of the crystalline particles is preferably 10 μm or less. Here, the average particle size of the crystalline particles can be determined by the following method. First, a cross-section of the exterior material is prepared by ion milling or the like, and a cross-sectional SEM image is taken. Next, 100 crystalline particles are randomly selected from the cross-sectional SEM image, the particle sizes of these particles are measured, and the arithmetic mean is calculated to obtain the average particle size. When the particles are not spherical, the maximum distance (so-called maximum Feret diameter) between two parallel lines drawn from all angles so as to contact the contour of the particle is taken as the particle size.

[0038] In addition, from the viewpoint of ensuring the denseness of the sintered body, the volume fraction of the vitreous material in the exterior material is 1% by volume or more, preferably 1% by volume or more and 60% by volume or less. Here, the volume fraction of the vitreous material can be determined by the following method. First, the procedure of preparing a cross-section of the exterior material by ion milling or the like and taking a cross-sectional SEM image is repeated to obtain a three-dimensional SEM image. Next, the volume fraction of the vitreous material in a cube having a height about the thickness of the exterior material is calculated from the three-dimensional SEM image.

[0039] In addition, in the present embodiment, two or more types of crystalline materials are dispersed in the vitreous material. FIG. 2 is a schematic diagram showing an example of the cross-sectional structure of the exterior material in the present embodiment, and shows an example including two types of crystalline materials having a particle shape. In the vitreous material 21, the first crystalline material 23 and the second crystalline material 24 are dispersed. The average particle size of the first crystalline material 23 is larger than the average particle size of the second crystalline material 24. In addition, the first crystalline material 23 is polycrystalline. In addition, the second crystalline material 24 is present at the grain boundaries of the polycrystals and / or at the interface between the first crystalline material 23 and the vitreous material 21.

[0040] Figures 3 to 5 are schematic diagrams showing examples of the structure of the first crystalline material 23. Figure 3 shows an example in which the crystalline material 22 has a core-shell structure with the first crystalline material 23 as the core and the second crystalline material 24 as the shell. Further, Figure 4 shows an example in which the second crystalline material 24 is supported on the surface of the first crystalline material 23. Figure 5 is an example including both the structures of Figures 3 and 4, showing an example in which the crystalline material 22 has a core-shell structure and, further, the second crystalline material 24 is supported on the surface of the shell. Here, as a combination of materials from which a core-shell structure can be obtained, for example, a case where the glassy material is borosilicate glass, the first crystalline material is alumina (Al2O3), and the second crystalline material is gahnite (ZnAl2O4) can be cited. The crystalline material has a core-shell structure with alumina particles as the core part and gahnite as the shell part. By the strong bonding of the gahnite in the shell part with the glassy material, the denseness of the sintered body can be further improved. Note that the first crystalline material is alumina (Al2O3), magnesium oxide (MgO), silicon monoxide (SiO), silicon dioxide (SiO2), etc., and the second crystalline material is gahnite (ZnAl2O4), forsterite (Mg2SiO4), etc.

[0041] Also, from the viewpoint of ensuring the water vapor barrier property, the water vapor transmission rate of the exterior material is 1 × 10 -4 g / m 2 / day or less, preferably 1 × 10 -5 g / m 2 / day or less, more preferably 1 × 10 -6 g / m 2 / day or less. Here, the water vapor transmission rate of the exterior material can be determined by the following method. First, a part of the exterior material is taken out as a rectangular small piece by ion milling, polishing, or the like. Next, the water vapor transmission rate (23°C, 90% RH) of the exterior material is measured in accordance with JIS K7129-C (ISO15106-4).

[0042] The exterior material is preferably insulating from the viewpoint of suppressing a short circuit of the solid battery. Specifically, the ionic conductivity is 1 × 10 -7S / cm or less, preferably 1×10 -10 S / cm or less. Further, the electronic conductivity is 1×10 -7 S / cm or less, preferably 1×10 -10 S / cm or less.

[0043] In addition, it is preferable that the exterior material forms an integral sintering with the peripheral surface of the battery element and between the sintered bodies. Here, the peripheral surface of the battery element with which the exterior material integrally sinters is the side surface excluding the uppermost layer and the lowermost layer of the battery element, and the first end surface and the second end surface where the positive electrode terminal and the negative electrode terminal are formed. The uppermost layer and the lowermost layer of the battery element may be a positive electrode layer or a negative electrode layer, or a connection layer for joining with the exterior material may be provided. By joining the connection layer with the exterior material, the integration of the battery element and the exterior material becomes easy. It is preferable to use a solid electrolyte layer containing a polyanion-based compound for the connection layer. Here, examples of the solid electrolyte containing a polyanion-based compound include a lithium-containing phosphate compound as a lithium ion conductor and a sodium-containing phosphate compound as a sodium ion conductor. Also, a solid electrolyte layer containing at least one of the above common elements can be used for the connection layer. Here, the solid electrolyte layer containing at least one of the above common elements is a solid electrolyte layer containing at least one element selected from the group consisting of Zn, Al, Si, and Mg. For example, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, Li 1.2 Al 0.2 Ti 1.8 (PO4)3, Li 1.4 Mg 0.2 Ti 1.8 (PO4)3, etc. can be mentioned.

[0044] From the perspective of integral sintering, the positive electrode layer, negative electrode layer, and solid electrolyte layer that constitute the battery element may contain at least one of the above common elements. As such an example, for the positive electrode layer, those obtained by adding Al2O3, SiO2, MgO, etc. in addition to the positive electrode active material and the solid electrolyte can be mentioned. Also, for the negative electrode layer, those obtained by adding Al2O3, SiO2, MgO, etc. in addition to the negative electrode active material and the solid electrolyte can be mentioned. For the solid electrolyte layer, those obtained by adding Al2O3, SiO2, MgO, etc. in addition to the solid electrolyte can be mentioned.

[0045] Also, from the perspective of ensuring water vapor barrier properties and mechanical strength, the average thickness of the exterior material is 500 μm or less and 1 μm or more, preferably 100 μm or less and 5 μm or more. Here, the average thickness of the exterior material uses the average thickness calculated from the thicknesses of 100 locations on the upper surface portion, lower surface portion, and side surface portion of the exterior material.

[0046] (Terminal) Generally, a terminal (for example, an external terminal) is provided in the solid battery. In particular, a positive electrode terminal and a negative electrode terminal are provided on the first end face and the second end face located on opposite sides of the battery element. More specifically, a positive electrode terminal connected to the positive electrode layer and a negative electrode terminal connected to the negative electrode layer are provided. It is preferable to use a material with high conductivity for such a terminal. The material of the terminal is not particularly limited, and examples include at least one selected from the group consisting of silver, gold, platinum, aluminum, copper, tin, and nickel.

[0047] [Manufacturing Method of Solid Battery] Hereinafter, the manufacturing method of the solid battery according to Embodiment 1 of the present invention will be described.

[0048] The solid-state battery according to Embodiment 1 can be manufactured by combining the green sheet method using a green sheet, a printing method such as a screen printing method, and a dipping method. In one aspect, a solid electrolyte layer is formed by the green sheet method, a positive electrode layer and a negative electrode layer are formed by screen printing, and an exterior material is provided on the peripheral surface of the laminated body by dipping, whereby a solid-state battery according to one embodiment of the present invention can be manufactured. Hereinafter, the description will be made on the premise of this aspect, but it is not limited thereto, and a predetermined laminated body may be formed by the green sheet method or the screen printing method.

[0049] (Formation step of the unfired laminate) First, a paste for a solid electrolyte layer is applied onto a base material (for example, a PET film). Also, a paste for a positive electrode layer, a paste for a negative electrode layer, a paste for an electrode separation part, and a paste for an exterior material are prepared.

[0050] Each paste can be produced by wet mixing a predetermined constituent material of each layer appropriately selected from the group consisting of a positive electrode active material, a negative electrode active material, a conductive material, a solid electrolyte material, an insulating material, and a sintering aid, and an organic vehicle in which an organic material is dissolved in a solvent. The paste for the positive electrode layer contains a positive electrode active material, a conductive material, a solid electrolyte material, an organic material, and a solvent. The paste for the negative electrode layer contains a negative electrode active material, a conductive material, a solid electrolyte material, an organic material, and a solvent. The paste for the solid electrolyte layer contains a solid electrolyte material, a sintering aid, an organic material, and a solvent. The paste for the electrode separation part contains an insulating material (for example, a solid electrolyte material), a sintering aid, an organic material, and a solvent. The paste for the exterior material contains a glassy material, a crystalline material, an organic material, and a solvent.

[0051] Media can be used in wet mixing. Specifically, a ball mill method, a viscomill method, or the like can be used. On the other hand, a wet mixing method without using media may be used, and a sand mill method, a high-pressure homogenizer method, a kneader dispersion method, or the like may also be used.

[0052] The support substrate is not particularly limited as long as it can support the green laminate. For example, a substrate made of a polymer material such as polyethylene terephthalate can be used. When the green laminate is subjected to the firing process while being held on the substrate, a substrate having heat resistance against the firing temperature may be used.

[0053] As the solid electrolyte material contained in the solid electrolyte layer paste, a powder composed of a lithium-containing phosphate compound having a NASICON structure, an oxide having a perovskite structure, and / or an oxide having a garnet-type or garnet-type similar structure may be used as described above.

[0054] As the positive electrode active material contained in the positive electrode layer paste, for example, at least one selected from the group consisting of a lithium-containing phosphate compound having a NASICON-type structure, a lithium-containing phosphate compound having an olivine-type structure, a lithium-containing layered oxide, and a lithium-containing oxide having a spinel-type structure may be used.

[0055] As the negative electrode active material contained in the negative electrode layer paste, for example, an oxide containing at least one element selected from the group consisting of Ti, Si, Sn, Cr, Fe, Nb, and Mo, a lithium-containing phosphate compound having a NASICON-type structure, a lithium-containing phosphate compound having an olivine-type structure, and a negative electrode active material selected from at least one selected from the group consisting of a lithium-containing oxide having a spinel-type structure, the materials contained in the above solid electrolyte paste, and a conductive material may be used.

[0056] The organic material contained in the paste is not particularly limited, but at least one polymer material selected from the group consisting of polyvinyl acetal resin, cellulose resin, polyacrylic resin, polyurethane resin, polyvinyl acetate resin, and polyvinyl alcohol resin can be used. The solvent is not particularly limited as long as it can dissolve the above organic material, and for example, toluene and / or ethanol may be used.

[0057] As the sintering aid, at least one selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, boron oxide, silicon oxide, bismuth oxide, and phosphorus oxide may be used.

[0058] By drying the applied paste on a hot plate heated to 30°C or higher and 50°C or lower, a solid electrolyte layer sheet having a predetermined thickness is formed on a substrate (for example, a PET film).

[0059] (Lamination process of battery element) FIG. 6 is an exploded perspective view of a solid-state battery showing an example of the lamination process of the battery element 2. The solid electrolyte layer sheet 13 is peeled from the substrate. The positive electrode layer 11 is formed on the solid electrolyte layer sheet 13 by screen printing, and an electrode separation portion 14 is formed by screen printing around the positive electrode layer 11 to produce a positive electrode layer-integrated solid electrolyte layer sheet. Also, the negative electrode layer 12 is formed on the solid electrolyte layer sheet 13 by screen printing, and an electrode separation portion 14 is formed by screen printing around the negative electrode layer 12 to produce a negative electrode layer-integrated solid electrolyte sheet. The positive electrode layer-integrated solid electrolyte layer sheet and the negative electrode layer-integrated solid electrolyte sheet are alternately laminated so that the solid electrolyte layer 13 is interposed therebetween, and a battery element 2 having the solid electrolyte layer 13 disposed as a connection layer on the uppermost layer and the lowermost layer is obtained. Next, it is preferable to perform thermocompression bonding at a predetermined pressure (for example, about 50 or more and about 100 MPa or less) and subsequent isostatic pressing at a predetermined pressure (for example, about 150 or more and about 300 MPa or less). Thus, a predetermined battery element 2 can be manufactured. Next, the outermost packaging material 3 is formed by dipping the uppermost surface and the lowermost surface of the battery element 2 into a paste for the outermost packaging material. Also, the outermost packaging material 3 is formed by dipping the side surface of the battery element 2 where the end faces of the positive electrode layer and the negative electrode layer are not exposed into the paste for the outermost packaging material.

[0060] (Firing process) In the firing process, the unfired laminate is fired. Although this is merely an example, firing is carried out by removing the organic material at, for example, 500°C in a nitrogen gas atmosphere containing oxygen gas or in the air, and then heating in a nitrogen gas atmosphere or in the air at, for example, 550°C or higher and 1000°C or lower. Firing may be performed while pressing the unfired laminate in the stacking direction (in some cases, the stacking direction and the direction perpendicular to the stacking direction). Note that firing may be carried out at once (simultaneous firing) after providing the exterior material to the battery element body, or after firing the battery element body, the exterior material may be provided and further firing may be carried out (sequential firing).

[0061] Next, terminals are attached to the obtained laminate. The terminals are provided so as to be electrically connectable to the positive electrode layer and the negative electrode layer, respectively. For example, it is preferable to form the terminals by dipping them in a metal paste or the like. Although not particularly limited, the terminals are preferably composed of at least one selected from silver, gold, platinum, aluminum, copper, tin, and nickel.

[0062] In the above manufacturing method, the case where the solid battery is a lithium ion secondary battery has been described. However, by using a negative electrode active material and a positive electrode active material capable of occluding and releasing sodium ions, and a solid electrolyte through which sodium ions can conduct, a solid battery that is a sodium ion secondary battery can also be manufactured.

[0063] According to the present embodiment, it is possible to improve the water vapor barrier property and the mechanical strength of the exterior material.

[0064] Embodiment 2 The solid battery according to the present embodiment includes a battery element body including a positive electrode layer and a negative electrode layer laminated via a solid electrolyte layer, and an exterior material covering the surface of the battery element body. The exterior material is a sintered body containing a glassy material and at least one crystalline material, and the volume fraction of the crystalline material with respect to the sintered body of the crystalline material is 40% by volume or more and 99% by volume or less.

[0065] The solid-state battery according to this embodiment has an exterior material that is a sintered body containing a glassy material and at least one crystalline material, and has the same configuration as the solid-state battery according to Embodiment 1, except that the volume fraction of the crystalline material with respect to the sintered body of the crystalline material is 40% by volume or more and 99% by volume or less.

[0066] In this embodiment, the volume fraction of the crystalline material with respect to the sintered body of the crystalline material is 40% by volume or more and 99% by volume or less. Preferably, the volume fraction of the crystalline material with respect to the sintered body of the crystalline material is 50% by volume or more and 60% by volume or less. The glassy material in the sintered body joins the crystalline materials to improve the density, but when the volume fraction of the glassy material increases, the mechanical strength of the sintered body decreases. In this embodiment, by setting the volume fraction of the crystalline material with respect to the sintered body of the crystalline material to 40% by volume or more and 99% by volume or less, it is possible to improve the density of the sintered body while suppressing a decrease in the mechanical strength of the sintered body.

[0067] In this embodiment, the glassy material is not particularly limited, and examples thereof include at least one selected from the group consisting of soda-lime glass, potash glass, borate glass, borosilicate glass, barium borosilicate glass, zinc borate glass, barium borate glass, bismuth borosilicate salt glass, bismuth zinc borate glass, bismuth silicate glass, phosphate glass, aluminophosphate glass, and zinc phosphate glass. Preferably, it is borosilicate glass. Examples of the crystalline material include alumina (Al2O3) and garnet (ZnAl2O4). Note that the glassy material and the crystalline material containing at least one selected from the group consisting of Zn, Al, Si, and Mg, which are the common elements described in Embodiment 1, can also be used as needed in this embodiment.

[0068] FIG. 7 is a schematic diagram showing an example of the cross-sectional structure of the exterior material in the present embodiment. In the present embodiment, a dense sintered body is obtained by joining crystalline materials 25 dispersed in a glassy material 21. Further, when two or more kinds of crystalline materials are included, two or more kinds of crystalline particles may be separately dispersed in the glassy material.

[0069] Note that if the volume fraction of the sintered body of the crystalline material is 40% by volume or more and 99% by volume or less, the particle size of the crystalline particles is not particularly limited.

[0070] Further, in the present embodiment, the specular reflectance of visible light of the exterior material is 6% or less, preferably 3% or less. When the solid battery is adsorbed and moved using a chip mounter or the like for mounting or the like, if the reflectance of the exterior material is too high, the imaging element of the chip mounter may not be able to accurately recognize the position of the solid battery. In such a case, by lowering the reflectance of the exterior material, the position of the solid battery can be accurately recognized. Further, by reducing the reflectance, the appearance inspection of the solid battery becomes easier. Here, the specular reflectance of visible light of the exterior material can be obtained, for example, by measuring the specular reflectance of 30° incident light using a gloss meter GM-060 (manufactured by Konica Minolta).

[0071] Also according to the present embodiment, as in the case of Embodiment 1, it is possible to improve the water vapor barrier property and mechanical strength of the exterior material.

[0072] As described above, the embodiments of the present invention have been described, but these are merely illustrative of typical examples. Therefore, it will be easily understood by those skilled in the art that the present invention is not limited thereto, and various aspects can be considered without changing the gist of the present invention.

Industrial Applicability

[0073] The solid battery according to an embodiment of the present invention can be used in various fields where power storage is assumed. Although it is merely an example, the solid battery according to an embodiment of the present invention can be used in the fields of electricity, information, and communication where mobile devices are used (for example, mobile device fields such as mobile phones, smartphones, notebook computers, digital cameras, activity monitors, arm computers, and electronic paper), home and small industrial applications (for example, fields of power tools, golf carts, home, care, and industrial robots), large industrial applications (for example, fields of forklifts, elevators, and port cranes), transportation system fields (for example, fields of hybrid vehicles, electric vehicles, buses, trains, electric assist bicycles, and electric motorcycles), power system applications (for example, fields of various power generations, load conditioners, smart grids, and general household installed energy storage systems), medical applications (fields of medical devices such as earphone hearing aids), pharmaceutical applications (fields of medication management systems), as well as the IoT field, space and deep sea applications (for example, fields of space exploration machines, submersible survey ships), and the like.

Explanation of Signs

[0074] 1 Solid battery 2 Battery element 3 Exterior material 4 Positive electrode terminal 5 Negative electrode terminal 11 Positive electrode layer 12 Negative electrode layer 13 Solid electrolyte layer 14 Electrode separation part 21 Glassy material 22, 25 Crystalline materials 23 First crystalline material 24 Second crystalline material

Claims

1. A battery element including a positive electrode layer and a negative electrode layer laminated via a solid electrolyte layer, and an exterior material covering the surface of the battery element, wherein the exterior material is a sintered body including a glassy material and at least one crystalline material, the glassy material and the crystalline material contain at least one common element, and the common element is at least one selected from the group consisting of Zn, Al, and Mg, and a solid battery in which a volume fraction of the crystalline material with respect to the sintered body is 40% by volume or more and 99% by volume or less.

2. The solid battery according to claim 1, wherein a volume fraction of the crystalline material with respect to the sintered body is 50% by volume or more and 60% by volume or less.

3. The solid battery according to claim 1, wherein the glassy material is a borosilicate glass, and the crystalline material is at least one selected from the group consisting of alumina, garnet, magnesium oxide, and forsterite.

4. The solid battery according to claim 3, wherein the crystalline material includes alumina particles and garnet covering at least a part of the surface of the alumina particles.

5. The solid battery according to any one of claims 1 to 4, wherein the exterior material has a visible light reflectance of 6% or less.

Images