Battery

Abstract

This battery comprises a plurality of solid-state battery cells, and connection layers positioned between the plurality of solid-state battery cells. Each of the plurality of solid-state battery cells has a structure in which a positive electrode current collector, a positive electrode active material layer, a solid electrolyte layer containing an inorganic solid electrolyte, a negative electrode active material layer, and a negative electrode current collector are laminated in the stated order. The plurality of solid-state battery cells are electrically connected in series. In two adjacent solid-state battery cells among the plurality of solid-state battery cells, the positive electrode current collector of one and the negative electrode current collector of the other are laminated with the connection layer interposed therebetween. The connection layer contains an electrically conductive material. The Young's modulus of the connection layer is less than the Young's modulus of each of the positive electrode current collector, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode current collector.

Description

[Technical field]

[0001] The present disclosure relates to batteries. [Background technology]

[0002] The voltage and output of a battery can be increased by electrically connecting unit cells such as battery cells in series. As a technology related to such a series-connected battery, for example, Patent Document 1 discloses an all-solid-state battery in which a bipolar electrode is formed by a composite current collector of a positive electrode and a negative electrode. Patent Document 2 discloses a battery using a bipolar electrode having an adhesive layer made of a metal filler, a carbon filler, and an epoxy resin that bonds the current collector, and a gel polymer electrolyte. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-195495 A [Patent Document 2] JP 2005-317468 A Summary of the Invention [Problem to be solved by the invention]

[0004] There is a need in the art for a highly reliable series connected battery. Accordingly, the present disclosure provides a highly reliable series connected battery. [Means for solving the problem]

[0005] A battery according to an embodiment of the present disclosure includes a plurality of solid-state battery cells and a connection layer located between the plurality of solid-state battery cells, each of the plurality of solid-state battery cells having a structure in which a positive electrode current collector, a positive electrode active material layer, a solid electrolyte layer containing an inorganic solid electrolyte, a negative electrode active material layer, and a negative electrode current collector are stacked in this order, the plurality of solid-state battery cells are electrically connected in series, and the positive electrode current collector of one of two adjacent solid-state battery cells among the plurality of solid-state battery cells and the negative electrode current collector of the other are stacked via the connection layer, the connection layer includes a conductive material, and the Young's modulus of the connection layer is smaller than the Young's modulus of the positive electrode current collector, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode current collector. Effect of the Invention

[0006] According to the present disclosure, a highly reliable series-connected battery can be provided. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a battery according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing a schematic configuration of a battery according to a first modification of the embodiment. [Diagram 3] FIG. 3 is a diagram showing a schematic configuration of a battery according to a second modification of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] (How one aspect of the present disclosure was achieved) In order to obtain a high-voltage battery, for example, battery cells are connected in series via a bipolar collector having a positive electrode active material layer laminated on one side and a negative electrode active material layer laminated on the other side. However, when stacking (connecting) the battery cells, or when a defect such as a pinhole or a tear occurs in the bipolar collector due to an external impact or a thermal cycle, the voltage of the battery decreases, and the desired characteristics cannot be obtained. Such a problem becomes more evident when the battery is enlarged, that is, when the electrode plate area is enlarged and the number of connections is increased. For example, a battery having a bipolar collector is generally produced by coating a positive electrode active material layer on one side of the front and back of the bipolar collector and a negative electrode active material layer on the other side, forming each battery cell, and integrating them by pressing them. During the manufacturing process, if there is an in-plane variation in the thickness of the active material layer on the front and back of the bipolar electrode, or if there is a difference in the compression characteristics when pressure is applied, the bipolar electrode is sandwiched between the active material layers, so that stress is likely to concentrate on the bipolar electrode, which is likely to cause defects such as breakage of the bipolar electrode. In addition, since multiple battery cells are stacked, the stress on each battery cell caused by expansion or contraction due to temperature changes in each component of the battery cell is likely to increase, making the battery prone to damage. Thus, improved reliability is desired for series-connected batteries in which multiple battery cells are electrically connected in series.

[0009] Therefore, the present disclosure provides a highly reliable series-connected battery.

[0010] (Summary of the Disclosure) An outline of one embodiment of the present disclosure is as follows.

[0011] A battery according to one embodiment of the present disclosure includes a plurality of solid-state battery cells and a connection layer located between the plurality of solid-state battery cells, each of the plurality of solid-state battery cells having a structure in which a positive electrode current collector, a positive electrode active material layer, a solid electrolyte layer containing an inorganic solid electrolyte, a negative electrode active material layer, and a negative electrode current collector are stacked in this order, the plurality of solid-state battery cells are electrically connected in series, and the positive electrode current collector of one of two adjacent solid-state battery cells among the plurality of solid-state battery cells and the negative electrode current collector of the other are stacked via the connection layer, the connection layer includes a conductive material, and the Young's modulus of the connection layer is smaller than the Young's modulus of the positive electrode current collector, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode current collector.

[0012] In this way, since the solid-state battery cells are electrically connected in series, the battery according to this embodiment is a series-connected battery. In addition, the positive electrode collector of one of the adjacent solid-state battery cells and the negative electrode collector of the other are stacked via a connection layer that is smaller in Young's modulus than each component of the solid-state battery cells and therefore easily deforms. Therefore, the deformation of the connection layer alleviates the stress on the solid-state battery cells caused by the expansion or contraction of each component of the solid-state battery cells due to temperature changes and repeated charging and discharging. As a result, damage to each component of the solid-state battery cells is suppressed. In addition, the connection layer also alleviates stress caused by external heat, impact, vibration, etc. on the battery. Therefore, according to this embodiment, a highly reliable series-connected battery can be realized.

[0013] For example, the connection layer may include a resin.

[0014] This makes it easier to form a connection layer with a small Young's modulus because it contains resin, which is a soft material compared to metals, ceramics, etc. In addition, since resin tends to have a smaller specific gravity than inorganic materials, the inclusion of resin in the connection layer can increase the weight energy density of the battery.

[0015] For example, the connection layer may include a solid electrolyte.

[0016] This makes it easier to alleviate stress on the solid-state battery cell since the solid electrolyte is a material that is easily deformed by pressure, thereby improving the reliability of the battery.

[0017] For example, the connection layer may have voids.

[0018] As a result, the voids in the connection layer also relieve stress on the solid-state battery cells. Also, by changing the shape and volume of the voids, the Young's modulus of the connection layer can be controlled over a wide range.

[0019] For example, the connection layer may have a thickness of not less than 1 μm and not more than 20 μm.

[0020] This makes it possible to reduce stress on the solid-state battery cell while suppressing a decrease in volumetric energy density, thereby achieving both high battery reliability and high volumetric energy density.

[0021] Furthermore, for example, the connection layer may be located inside the outer periphery of the positive electrode current collector and the negative electrode current collector in a plan view.

[0022] This makes it possible to prevent the connection layer from coming into contact with the side surface of the positive electrode active material layer or the negative electrode active material layer due to growth of the conductive material contained in the connection layer, or from coming into contact with and adhering to the side surface of the positive electrode active material layer or the negative electrode active material layer when the stacked solid-state battery cell is cut, etc. As a result, it is possible to prevent short circuits and deterioration of the characteristics of the battery, thereby improving the reliability of the battery.

[0023] In addition, for example, the battery may further include a buffer layer located between the plurality of solid-state battery cells and made of a material different from the connection layer, and the Young's modulus of the buffer layer may be equal to or lower than the Young's modulus of the positive electrode current collector, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode current collector.

[0024] As a result, the multiple solid-state battery cells are stacked via the connection layers and buffer layers made of different materials, thereby mitigating stress on the multiple solid-state battery cells under a wider range of conditions.

[0025] Furthermore, for example, the buffer layer may be provided so as to surround the outer periphery of the connection layer in a plan view and may be frame-shaped.

[0026] As a result, the buffer layer surrounds the outer periphery of the connection layer, so that the buffer layer and connection layer between the multiple solid-state battery cells tend to deform uniformly when subjected to stress from any direction.

[0027] Also, for example, the Young's modulus of the buffer layer may be smaller than the Young's modulus of the connection layer.

[0028] As a result, the buffer layer is more easily deformed than the connection layer, and can therefore deform and relieve stress before the connection layer does, thereby enhancing the effect of relieving stress on the multiple solid-state battery cells.

[0029] Also, for example, the buffer layer does not need to include a conductive material.

[0030] In this way, since the buffer layer does not contain a conductive material, it becomes soft and has a low thermal conductivity, which makes it easier to deform and less susceptible to temperature changes, so that it functions as a buffer against external shocks and thermal shocks, and can enhance the effect of mitigating stress on the multiple solid-state battery cells.

[0031] For example, the buffer layer may include the inorganic solid electrolyte.

[0032] In this way, by using the same inorganic solid electrolyte as the solid electrolyte layer as the material of the buffer layer, the battery can be produced efficiently in terms of the manufacturing process.

[0033] For example, the inorganic solid electrolyte may have lithium ion conductivity.

[0034] This makes it possible to improve the reliability of the series-connected lithium ion batteries.

[0035] Hereinafter, the embodiment will be described in detail with reference to the drawings.

[0036] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement positions and connection forms of the components shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components that are not described in an independent claim showing a top concept are described as optional components.

[0037] In addition, the drawings are not necessarily strict illustrations. In the drawings, the same reference numerals are used for substantially the same configurations, and duplicated explanations are omitted or simplified.

[0038] In this specification and the drawings, the x-axis, y-axis, and z-axis represent the three axes of a three-dimensional Cartesian coordinate system. In each embodiment, the z-axis direction is the thickness direction of the battery. In this specification, the "thickness direction" refers to the direction perpendicular to the surface on which each layer is stacked.

[0039] In addition, in this specification, "plan view" refers to the case where the battery is viewed along the stacking direction of the battery, and "thickness" in this specification refers to the length of the battery and each layer in the stacking direction.

[0040] In addition, in this specification, the terms "inside" and "outside" refer to the inside and outside when the battery is viewed along the stacking direction of the battery.

[0041] In this specification, the terms "upper" and "lower" in the battery configuration do not refer to the upper direction (vertically upward) and lower direction (vertically downward) in absolute spatial recognition, but are used as terms defined by a relative positional relationship based on the stacking order in the stacking configuration. In addition, the terms "upper" and "lower" are applied not only to the case where two components are arranged with a gap between them and another component is present between the two components, but also to the case where two components are arranged in close contact with each other and the two components are in contact with each other.

[0042] (Embodiment) [Overview of stacked battery] First, the battery according to the present embodiment will be described.

[0043] Fig. 1 is a diagram showing a schematic configuration of a battery according to the present embodiment. Specifically, Fig. 1(a) is a cross-sectional view of a battery 100 according to the present embodiment, and Fig. 1(b) is a plan view of the battery 100 as viewed from above in the z-axis direction. Fig. 1(a) shows a cross section taken along line II in Fig. 1(b). Fig. 1(b) shows, with solid lines, the planar shapes of the components of the battery when the battery 100 is viewed from above.

[0044] 1, the battery 100 has a structure in which two solid-state battery cells 1a and 1b are stacked, and includes the solid-state battery cells 1a and 1b and a connection layer 16 located between the solid-state battery cells 1a and 1b. The battery 100 is a series-connected battery, and the solid-state battery cells 1a and 1b are electrically connected in series. For example, the connection layer 16 electrically connects the solid-state battery cell 1a and the solid-state battery cell 1b in series.

[0045] The solid-state battery cells 1a and 1b each have a positive electrode current collector 11, a positive electrode active material layer 12 arranged in contact with the positive electrode current collector 11, a negative electrode current collector 13, a negative electrode active material layer 14 arranged in contact with the negative electrode current collector 13, and a solid electrolyte layer 15 arranged between the positive electrode active material layer 12 and the negative electrode active material layer 14 and containing an inorganic solid electrolyte. The positive electrode active material layer 12 and the negative electrode active material layer 14 are arranged between the positive electrode current collector 11 and the negative electrode current collector 13. The solid-state battery cells 1a and 1b each have a structure in which the positive electrode current collector 11, the positive electrode active material layer 12, the solid electrolyte layer 15, the negative electrode active material layer 14, and the negative electrode current collector 13 are stacked in this order from the bottom.

[0046] The positive electrode current collector 11, the positive electrode active material layer 12, the solid electrolyte layer 15, the negative electrode active material layer 14, and the negative electrode current collector 13 are each rectangular in plan view. The shapes of the positive electrode current collector 11, the positive electrode active material layer 12, the solid electrolyte layer 15, the negative electrode active material layer 14, and the negative electrode current collector 13 in plan view are not particularly limited, and may be shapes other than a rectangle, such as a circle, an ellipse, or a polygon. The positive electrode current collector 11, the positive electrode active material layer 12, the solid electrolyte layer 15, the negative electrode active material layer 14, and the negative electrode current collector 13 have the same shape, position, and size in plan view.

[0047] The positive electrode current collector 11 of one solid-state battery cell 1a of two adjacent solid-state battery cells and the negative electrode current collector 13 of the other solid-state battery cell 1b are stacked via a connection layer 16. That is, the two adjacent solid-state battery cells 1a and 1b are stacked via the connection layer 16 so that their up-down directions are the same. The solid-state battery cells 1a and 1b and the connection layer 16 have the same shape, position, and size in a plan view. The solid-state battery cell 1a and the solid-state battery cell 1b are separated from each other with the connection layer 16 sandwiched therebetween.

[0048] The positive electrode current collector 11, the negative electrode current collector 13, and the solid electrolyte layer 15 of each of the solid battery cells 1a and 1b have the same shape, position, and size in a plan view. The positive electrode current collector 11 of the solid battery cell 1a and the negative electrode current collector 13 of the solid battery cell 1b are in contact with a connection layer 16. In this specification, the positive electrode current collector 11 and the negative electrode current collector 13 may be collectively referred to simply as "current collectors". The current collectors are not particularly limited as long as they are made of a material having electrical conductivity.

[0049] The current collector may be, for example, a foil, plate or mesh made of stainless steel, nickel, aluminum, iron, titanium, copper, palladium, gold and platinum, or an alloy of two or more of these metals. The material of the current collector may be appropriately selected in consideration of the fact that it does not melt or decompose during the manufacturing process, the temperature at which it is used, and the pressure at which it is used, as well as the battery operating potential and electrical conductivity applied to the current collector. The material of the current collector may also be selected according to the required tensile strength and heat resistance. The current collector may be a high-strength electrolytic copper foil, or a clad material in which different metal foils are laminated.

[0050] The thickness of the current collector is, for example, not less than 10 μm and not more than 100 μm.

[0051] The surface of the current collector in contact with the connection layer 16 may be roughened to improve adhesion with the connection layer 16 and strengthen the laminated structure of the solid-state battery cells 1a and 1b. The surface of the current collector in contact with the connection layer 16 may be coated with an adhesive component such as a conductive organic binder. This can improve the adhesion between the current collector and the connection layer 16.

[0052] The positive electrode active material layer 12 is laminated in contact with one surface of the positive electrode current collector 11. The positive electrode active material layer 12 contains at least a positive electrode active material. The positive electrode active material layer 12 is mainly a layer composed of a positive electrode material such as a positive electrode active material. The positive electrode active material is a substance in which metal ions such as lithium (Li) ions or magnesium (Mg) ions are inserted into or detached from the crystal structure at a potential higher than that of the negative electrode, and oxidation or reduction is performed accordingly. The type of the positive electrode active material can be appropriately selected according to the type of the battery, and known positive electrode active materials can be used.

[0053] Examples of the positive electrode active material include compounds containing lithium and transition metal elements. Specifically, oxides containing lithium and transition metal elements, and phosphate compounds containing lithium and transition metal elements can be mentioned. Examples of the oxides containing lithium and transition metal elements include, for example, LiNi x M 1-x O2 (where M is at least one element among Co, Al, Mn, V, Cr, Mg, Ca, Ti, Zr, Nb, Mo, and W, and x is 0 < x ≦ 1), such as lithium nickel composite oxides, layered oxides such as lithium cobaltate (LiCoO2), lithium nickelate (LiNiO2), and lithium manganate (LiMn2O4), and lithium manganate having a spinel structure (for example, LiMn2O4, Li2MnO3, and LiMO2) are used. Examples of the phosphate compounds containing lithium and transition metal elements include, for example, lithium iron phosphate (LiFePO4) having an olivine structure. In addition, sulfides such as sulfur (S) and lithium sulfide (Li2S) can also be used as the positive electrode active material. In that case, a material in which lithium niobate (LiNbO3) or the like is coated on or added to the positive electrode active material particles can be used as the positive electrode active material. Note that only one type of these materials may be used as the positive electrode active material, or two or more of these materials may be combined and used.

[0054] As described above, the positive electrode active material layer 12 may contain at least a positive electrode active material. The positive electrode active material layer 12 may be a mixture layer composed of a mixture of a positive electrode active material and other additive materials. As the other additive materials, for example, a solid electrolyte such as an oxide-based solid electrolyte or a sulfide-based solid electrolyte, a conductive assistant such as acetylene black, and a binding binder such as polyethylene oxide or polyvinylidene fluoride can be used. The positive electrode active material layer 12 can improve ion conductivity such as lithium ion conductivity in the positive electrode active material layer 12 and can improve electronic conductivity by mixing the positive electrode active material and other additive materials such as a solid electrolyte at a predetermined ratio.

[0055] The thickness of the positive electrode active material layer 12 is, for example, not less than 5 μm and not more than 300 μm.

[0056] The negative electrode active material layer 14 is laminated in contact with one surface of the negative electrode current collector 13. The negative electrode active material layer 14 includes at least a negative electrode active material. The negative electrode active material layer 14 is a layer mainly composed of a negative electrode material such as a negative electrode active material. The negative electrode active material refers to a material in which metal ions such as lithium (Li) ions or magnesium (Mg) ions are inserted or extracted into or from a crystal structure at a potential lower than that of the positive electrode, and oxidation or reduction occurs accordingly. The type of positive electrode / negative electrode active material can be appropriately selected depending on the type of battery, and a known negative electrode active material can be used.

[0057] Examples of the negative electrode active material include carbon materials such as natural graphite, artificial graphite, graphite carbon fiber, and resin-sintered carbon, and alloy-based materials that are mixed with a solid electrolyte. Examples of the alloy-based materials include LiAl, LiZn, Li3Bi, Li3Cd, Li3Sb, Li4Si, Li 4.4 Pb, Li 4.4 Sn, Li 0.17 C or lithium alloys such as LiC6, lithium titanate (Li4Ti5O 12 ), zinc oxide (ZnO) and silicon oxide (SiO x) and other metal oxides can be used. For the negative electrode active material, only one of these materials may be used, or two or more of these materials may be used in combination.

[0058] As described above, the negative electrode active material layer 14 may contain at least a negative electrode active material. The negative electrode active material layer 14 may be a mixture layer composed of a mixture of a negative electrode active material and other additive materials. Examples of the other additive materials include solid electrolytes such as oxide-based solid electrolytes or sulfide-based solid electrolytes, conductive assistants such as acetylene black, and binding binders such as polyethylene oxide or polyvinylidene fluoride. The negative electrode active material layer 14 can improve ion conductivity such as lithium ion conductivity in the negative electrode active material layer 14 and electronic conductivity by mixing a positive electrode negative electrode active material and other additive materials such as solid electrolytes at a predetermined ratio.

[0059] The negative electrode active material layer 14 has a thickness of, for example, 5 μm or more and 300 μm or less.

[0060] The positive electrode active material layer 12 and the negative electrode active material layer 14 of each of the solid-state battery cells 1a and 1b have the same shape, position and size in a plan view.

[0061] The solid electrolyte layer 15 of each of the solid battery cells 1a and 1b is disposed between the positive electrode active material layer 12 and the negative electrode active material layer 14, and is in contact with the positive electrode active material layer 12 and the negative electrode active material layer 14.

[0062] The solid electrolyte layer 15 includes at least an inorganic solid electrolyte as a solid electrolyte. The solid electrolyte layer 15 includes, for example, an inorganic solid electrolyte as a main component. The inorganic solid electrolyte may be a known inorganic solid electrolyte for batteries that does not have electronic conductivity and has ionic conductivity. For the inorganic solid electrolyte, for example, an inorganic solid electrolyte that conducts metal ions such as lithium ions or magnesium ions may be used. The type of inorganic solid electrolyte may be appropriately selected according to the type of conductive ions. For example, solid electrolytes such as sulfide-based solid electrolytes, halogen-based solid electrolytes, and oxide-based solid electrolytes may be used as the inorganic solid electrolyte. For example, a sulfide-based solid electrolyte, a halogen-based solid electrolyte, or an oxide-based solid electrolyte having lithium ion conductivity may be used as the inorganic solid electrolyte.

[0063] Examples of sulfide-based solid electrolytes that can be used include lithium-containing sulfides such as Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, Li2S-SiS2-LiI, Li2S-SiS2-Li3PO4, Li2S-Ge2S2, Li2S-GeS2-P2S5, and Li2S-GeS2-ZnS. Examples of oxide-based solid electrolytes include lithium-containing metal oxides such as Li2O-SiO2 and Li2O-SiO2-P2O5, Li x P y O 1-z N z Lithium-containing metal nitrides such as lithium phosphate (Li3PO4), lithium-containing transition metal oxides such as lithium titanium oxide, etc. As the solid electrolyte, only one of these materials may be used, or two or more of these materials may be used in combination.

[0064] The halogen-based solid electrolyte is a solid electrolyte containing a halide. The halide is, for example, a compound consisting of Li, M', and X'. M' is at least one element selected from the group consisting of metal elements and metalloid elements other than Li. X' is at least one element selected from the group consisting of F, Cl, Br, and I. The "metal element" refers to all elements contained in Groups 1 to 12 of the periodic table (excluding hydrogen), and all elements contained in Groups 13 to 16 of the periodic table (excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se). The "metalloid element" refers to B, Si, Ge, As, Sb, and Te. For example, M' may contain Y (yttrium). Examples of halides containing Y include Li3YCl6 and Li3YBr6.

[0065] Other halides include, for example, Li2MgX'4, Li2FeX'4, Li(Al,Ga,In)X'4, Li3(Al,Ga,In)X'6, LiOX', and LiX'.Specific halides include, for example, Li3InBr6, Li3InCl6, Li2FeCl4, Li2CrCl4, Li3OCl, and LiI.

[0066] As an oxide-based solid electrolyte, for example, Li7La3Zr2O 12 (LLZ), Li 1.3 Al 0.3 Ti 1.7 (PO4)3(LATP) or (La,Li)TiO3(LLTO) are used.

[0067] The solid electrolyte layer 15 may contain, in addition to the inorganic solid electrolyte, a binding binder such as polyethylene oxide or polyvinylidene fluoride.

[0068] The thickness of the solid electrolyte layer 15 is, for example, not less than 5 μm and not more than 150 μm.

[0069] The inorganic solid electrolyte material may be composed of an aggregate of particles, or may be composed of a sintered structure.

[0070] 1, the positive electrode current collector 11 and the negative electrode current collector 13 of each of the solid-state battery cells 1a and 1b have the same shape, position, and size in a plan view as the connection layer 16. The positive electrode current collector 11 of the solid-state battery cell 1a and the negative electrode current collector 13 of the solid-state battery cell 1b are in contact with the connection layer 16 on their entire surfaces on the connection layer 16 side.

[0071] The Young's modulus of the connection layer 16 is smaller than that of the positive electrode current collector 11 and the negative electrode current collector 13. As a result, the stress on the solid-state battery cells 1a and 1b caused by the expansion or contraction of the current collectors due to temperature changes is alleviated by the deformation of the connection layer 16. Furthermore, the connection layer 16 is deformed between the current collectors by pressure in the lamination process in the manufacture of the battery 100, improving the bonding between the connection layer 16 and the current collectors above and below the connection layer 16. In addition, peeling and cracks caused at the interface between the current collectors and the connection layer 16 due to external impacts, thermal cycles, and the like are suppressed. As a result, the reliability of the battery 100 is improved.

[0072] Furthermore, the Young's modulus of the connection layer 16 is smaller than that of the solid electrolyte layer 15. As a result, the stress on the solid-state battery cells 1a and 1b caused by the expansion or contraction of the solid electrolyte layer 15 due to temperature changes and repeated charging and discharging is alleviated by the deformation of the connection layer 16. This improves the reliability of the battery 100.

[0073] Furthermore, the Young's modulus of the connection layer 16 is smaller than those of the positive electrode active material layer 12 and the negative electrode active material layer 14. As a result, the stress on the solid-state battery cells 1a and 1b caused by the expansion or contraction of the positive electrode active material layer 12 and the negative electrode active material layer 14 due to temperature changes and repeated charging and discharging is alleviated by the deformation of the connection layer 16. As a result, the reliability of the battery 100 is improved.

[0074] The relative relationship of these Young's moduli can be measured by comparing the relative relationship of the displacement characteristics against the pressure when a probe is pressed into each component along the stacking direction, or the size of the depression, etc.

[0075] The connection layer 16 is made of a material having electronic conductivity. That is, the connection layer 16 includes a conductive material. The connection layer 16 may be made of a material obtained by mixing an insulating material having insulating properties, such as a resin material and a solid electrolyte material, and a conductive material having electronic conductivity. The material for the connection layer 16 may be made by adjusting the type and composition of the material in consideration of ease of manufacture in the manufacturing process, stress relaxation performance, thermal shock resistance, and thermal cycle resistance. The connection layer 16 may be made of a material obtained by mixing, for example, a conductive metal and a solid electrolyte or various resin materials that are softer than the current collectors, from the viewpoint of bonding property when stacked and pressed with the current collectors, and relaxation of stress on the solid battery cells 1a and 1b caused by expansion or contraction of the current collectors due to temperature change.

[0076] Examples of the conductive material contained in the connection layer 16 include silver, copper, nickel, zinc, aluminum, palladium, gold, platinum, and alloys of combinations of these metals. The conductive material contained in the connection layer 16 may be a semiconductor material.

[0077] The connection layer 16 may also contain a solid electrolyte. Examples of the solid electrolyte used in the connection layer 16 include the inorganic solid electrolyte used in the solid electrolyte layer 15. The solid electrolyte used in the connection layer 16 and the inorganic solid electrolyte used in the solid electrolyte layer 15 may be the same type or different types. From the viewpoint of easily manufacturing the battery 100 with good productivity, the connection layer 16 may contain the same material as the solid electrolyte layer 15. In particular, it is well known that soft solid electrolytes, such as sulfide-based solid electrolytes, are easily deformed by pressure and form a bonding interface between particles of the solid electrolyte. By including a solid electrolyte having such characteristics in the connection layer 16, it becomes easier to alleviate stress on the solid battery cells 1a and 1b caused by the expansion or contraction of the current collector due to temperature change. As a result, the thermal shock resistance and cold-heat cycle resistance of the battery 100 are improved.

[0078] The connection layer 16 may also contain a resin. This makes it easier to form a connection layer 16 that is softer than the current collector and has a smaller Young's modulus. Since resin tends to have a smaller specific gravity than inorganic materials, the weight energy density of the battery 100 can be increased by including a resin in the connection layer 16.

[0079] The resin used in the connection layer 16 may be a thermoplastic resin or a thermosetting resin. Examples of the thermoplastic resin include polyethylene resin, polypropylene resin, acrylic resin, polystyrene resin, vinyl chloride resin, silicone resin, polyamide resin, polyimide resin, fluorinated hydrocarbon resin, polyether resin, butadiene rubber, isoprene rubber, styrene-butadiene rubber (SBR), styrene-butadiene-styrene copolymer (SBS), styrene-ethylene-butadiene-styrene copolymer (SEBS), ethylene-propylene rubber, butyl rubber, chloroprene rubber, and acrylonitrile-butadiene rubber. Examples of the thermosetting resin include (i) amino resins such as urea resin, melamine resin, and guanamine resin, (ii) epoxy resins such as bisphenol A type, bisphenol F type, phenol novolac type, and alicyclic type, (iii) oxetane resin, (iv) phenol resins such as resol type and novolac type, and (v) silicone-modified organic resins such as silicone epoxy and silicone polyester. Among these, from the viewpoint of connection strength, the thermosetting resin used in the connection layer 16 may be a phenol resin. Similarly, from the viewpoint of connection strength, the thermosetting resin used in the connection layer 16 may be an epoxy resin.

[0080] The connection layer 16 may be made of a material in which conductive material particles or semiconductor material particles are contained in a solid electrolyte or a resin. The connection layer 16 may contain a conductive material as a main component. For example, the connection layer 16 is made of a solid electrolyte and a conductive material. This makes it possible to reduce the electrical resistance component while mitigating the stress caused by the expansion or contraction of the current collector due to temperature change as described above, thereby realizing a battery 100 with small electrical loss.

[0081] The connection layer 16 may also be made of a thermosetting conductive paste containing metal and resin as main components.

[0082] From the viewpoint of adjusting the thermal expansion coefficient and softness (Young's modulus) of the connection layer 16, the connection layer 16 may be made of a material in which the above-mentioned conductive paste contains a solid electrolyte or the like.

[0083] The connection layer 16 may have voids such as pores or bubbles containing air. The voids may be formed by being surrounded by the material of the connection layer 16, or may be formed by being surrounded by the connection layer 16 and the current collector. The voids in the connection layer 16 can relieve stress on the solid-state battery cells 1a and 1b. The softness (Young's modulus) of the connection layer 16 can be controlled over a wide range by changing the shape and volume of the voids. Therefore, the stress on the solid-state battery cells 1a and 1b caused by the expansion or contraction of the current collector due to temperature change can be further relieved. There is no particular limit to the method of forming the voids, and the voids are formed, for example, by forming the connection layer 16 from an aggregate of a powder material. The voids may also be formed by forming the connection layer 16 from a resin containing bubbles.

[0084] The connection layer 16 may also contain a non-flammable material such as a metal, ceramics, or a solid electrolyte. When the connection layer 16 contains a non-flammable material, it also has the effect of acting as a layer wall that suppresses the spread of fire when the battery generates abnormal heat.

[0085] Furthermore, the connection layer 16 does not have to be formed on the entire surface of the contacting current collector, and may be formed partially on the surface of the contacting current collector by, for example, patterning.

[0086] The connection layer 16 may be made up of multiple layers of different materials.

[0087] The thickness of the connection layer 16 is not particularly limited, but from the viewpoint of the volumetric energy density of the battery, it is advantageous to have a smaller thickness. From the viewpoint of the volumetric energy density, the thickness of the connection layer 16 may be thinner than the thickness of the current collector. The thickness of the connection layer 16 is, for example, 1 μm or more and 20 μm or less, and preferably 2 μm or more and 10 μm or less. When the thickness of the connection layer 16 is within the above range, it is easy to alleviate stress caused by expansion or contraction of the current collector due to temperature change while suppressing a decrease in the volumetric energy density.

[0088] In addition, the specific gravity of the connection layer 16 is not particularly limited, but is preferably small from the viewpoint of weight energy density. The specific gravity of the connection layer 16 may be smaller than the specific gravity of the current collector. This reduces the effect on weight energy density, thereby obtaining a battery with a high energy density.

[0089] As described above, the battery 100 according to the present embodiment includes a plurality of solid-state battery cells 1a and 1b, and a connection layer 16 located between the plurality of solid-state battery cells 1a and 1b. Each of the plurality of solid-state battery cells 1a and 1b has a structure in which a positive electrode current collector 11, a positive electrode active material layer 12, a solid electrolyte layer 15 containing an inorganic solid electrolyte, a negative electrode active material layer 14, and a negative electrode current collector 13 are stacked in this order. The plurality of solid-state battery cells 1a and 1b are electrically connected in series. The positive electrode current collector 11 of the solid-state battery cell 1a and the negative electrode current collector 13 of the solid-state battery cell 1b are stacked via a connection layer 16. The connection layer 16 includes a conductive material, and the Young's modulus of the connection layer 16 is smaller than the Young's modulus of the positive electrode current collector 11, the positive electrode active material layer 12, the solid electrolyte layer 15, the negative electrode active material layer 14, and the negative electrode current collector 13.

[0090] In this way, the solid-state battery cells 1a and 1b are electrically connected in series, so that the battery 100 is a battery of a series connection type. In addition, the positive electrode collector 11 of the solid-state battery cell 1a and the negative electrode collector 13 of the solid-state battery cell 1b are laminated via the connection layer 16, which has a smaller Young's modulus than each component of the solid-state battery cells 1a and 1b and is therefore more easily deformed. Therefore, the deformation of the connection layer 16 reduces the stress on the solid-state battery cells 1a and 1b caused by expansion or contraction due to temperature changes in each component of the solid-state battery cells 1a and 1b, and by repeated charging and discharging. As a result, damage to each component of the solid-state battery cells 1a and 1b is suppressed. In addition, the connection layer 16 also reduces stress caused by external heat, impact, and vibration on the battery 100. Thus, a highly reliable series-connected battery 100 can be realized.

[0091] Furthermore, by including such a connection layer 16, the components of the solid-state battery cell are less likely to be damaged, even when the battery is further multi-layered and enlarged, and therefore a highly reliable battery with high output and large capacity can be realized.

[0092] In addition, since two current collectors and a connection layer 17 are present between the positive electrode active material layer 12 of the solid-state battery cell 1a and the negative electrode active material layer 14 of the solid-state battery cell 1b, even if one of the current collectors is damaged, the positive electrode active material layer 12 of the solid-state battery cell 1a and the negative electrode active material layer 14 of the solid-state battery cell 1b do not come into contact with each other, and the battery characteristics of the battery 100 are maintained.

[0093] When the configuration of battery 100 according to the present embodiment is compared with the configurations of the batteries described in Patent Documents 1 and 2, there are the following differences.

[0094] Patent Document 1 discloses an all-solid-state battery in which a bipolar electrode is formed with a composite current collector. However, the composite current collector described in Patent Document 1 is formed by metal bonding two current collectors, for example, the two current collectors are joined by plating or clad material. Therefore, the composite current collector does not have a connection part having a stress relaxation effect. Therefore, a connection part joined with a metal material cannot obtain a stress relaxation effect like the connection layer 16 of the battery 100 according to the present embodiment. For this reason, when a battery is multi-layered, the stress generated in the bipolar electrode due to the lamination process and thermal shock, etc., is likely to cause breakage, poor adhesion between the current collector and the power generation element, and voids. For this reason, there are problems in forming a multi-layered bipolar battery.

[0095] Also, Patent Document 2 discloses a bipolar battery using a bipolar electrode having an adhesive layer connecting the current collectors and a gel polymer electrolyte. However, simply connecting the current collectors with an adhesive layer made of a metal filler and an epoxy resin or the like does not provide the reliability improvement effect due to the stress relaxation property of the adhesive layer, as in the battery 100 according to the present embodiment. In order for the connection layer 16 to relax the stress, as in the battery 100 according to the present embodiment, it is essential that the adhesive layer is softer than the components of the battery, such as the current collectors and the electrolyte. Therefore, in a configuration in which a soft material such as a gel polymer electrolyte is used for the electrolyte, the adhesive layer cannot exert the stress relaxation effect between the bipolar electrodes. For this reason, in a multi-layered stacked battery, structural defects and deterioration of characteristics are likely to occur due to the stress generated in the bipolar electrodes, and there are problems with multi-layering the battery. In contrast, according to the battery 100 according to the present embodiment, the connection layer 16 relaxes the stress generated in the solid battery cells 1a and 1b, so the occurrence of the above-mentioned problems is suppressed. Furthermore, Patent Document 1 and Patent Document 2 do not disclose or suggest a series-connected battery having the connection layer 16 according to the present embodiment.

[0096] [Variation 1] The following describes Modification 1 of the embodiment. In the following description of Modification 1, differences from the embodiment will be mainly described, and descriptions of commonalities will be omitted or simplified.

[0097] Fig. 2 is a diagram showing a schematic configuration of a battery according to a first modified example of the embodiment. Specifically, Fig. 2(a) is a cross-sectional view of a battery 110 according to the present embodiment, and Fig. 2(b) is a plan view of the battery 110 as viewed from above in the z-axis direction. Fig. 2(a) shows a cross section taken along line II-II in Fig. 2(b). Fig. 2(b) shows the planar shapes of the components of the battery 110 as viewed from above using solid or broken lines.

[0098] As shown in FIG. 2, battery 110 according to variant 1 of the embodiment differs from battery 100 according to the embodiment in that, instead of connection layer 16, battery 110 according to variant 1 has connection layer 17 that is positioned inside the outer periphery of the current collector in a planar view.

[0099] The battery 110 has a structure in which two solid-state battery cells 1a and 1b are stacked, and includes the solid-state battery cells 1a and 1b and a connection layer 17 located between the solid-state battery cells 1a and 1b.

[0100] Of two adjacent solid-state battery cells, the positive electrode current collector 11 of one solid-state battery cell 1a and the negative electrode current collector 13 of the other solid-state battery cell 1b are stacked via a connection layer 17. That is, the solid-state battery cell 1a and the solid-state battery cell 1b are stacked via the connection layer 17 so that their up-down directions are the same.

[0101] The connection layer 17 has an area smaller than those of the positive electrode current collector 11 and the negative electrode current collector 13 in a planar view. Moreover, the connection layer 17 is located inside the outer periphery of the positive electrode current collector 11 and the negative electrode current collector 13 in a planar view. The material used for the connection layer 17 and the characteristics of the connection layer 17 are similar to those of the connection layer 16.

[0102] Since the connection layer 17 is located inside the outer periphery of the positive electrode current collector 11 and the negative electrode current collector 13 in a plan view, it is possible to prevent the conductive material such as metal contained in the connection layer 17 from contacting the side surface of the positive electrode active material layer 12 or the negative electrode active material layer 14 due to migration (i.e., growth of the conductive material such as metal contained in the connection layer 17) or from contacting and adhering to the side surface of the positive electrode active material layer 12 or the negative electrode active material layer 14 when the stacked solid-state battery cells are cut with a Thomson blade or the like. As a result, it is possible to prevent short circuits and deterioration of the characteristics of the battery 110, and thus it is possible to realize a highly reliable series-connected battery 110.

[0103] [Variation 2] The following describes Modification 2 of the embodiment. In the following description of Modification 2, differences from Modification 1 will be mainly described, and descriptions of commonalities will be omitted or simplified.

[0104] Fig. 3 is a diagram showing a schematic configuration of a battery according to a second modified example of the embodiment. Specifically, Fig. 3(a) is a cross-sectional view of a battery 120 according to the present embodiment, and Fig. 3(b) is a plan view of the battery 120 as viewed from above in the z-axis direction. Fig. 3(a) shows a cross section taken along line III-III in Fig. 3(b). Fig. 3(b) shows the planar shapes of the components of the battery 110 as viewed from above, using solid or dashed lines.

[0105] As shown in FIG. 3, battery 120 according to the second embodiment of the present invention differs from battery 110 according to the first embodiment of the present invention in that it further includes a buffer layer 18 arranged to surround the outer periphery of connection layer 17.

[0106] The battery 120 has a structure in which two solid-state battery cells 1a and 1b are stacked, and includes the solid-state battery cells 1a and 1b, a connection layer 17 and a buffer layer 18 located between the solid-state battery cells 1a and 1b.

[0107] The positive electrode current collector 11 of the solid-state battery cell 1a and the negative electrode current collector 13 of the solid-state battery cell 1b are stacked via a connection layer 17 and a buffer layer 18. In other words, the solid-state battery cell 1a and the solid-state battery cell 1b are stacked via the connection layer 17 and the buffer layer 18 so that the top and bottom directions are the same.

[0108] The buffer layer 18 is in contact with the positive electrode current collector 11 of the solid battery cell 1a and the negative electrode current collector 13 of the solid battery cell 1b. In a plan view, the outer periphery of the buffer layer 18 overlaps with the outer periphery of the positive electrode current collector 11, the positive electrode active material layer 12, the solid electrolyte layer 15, the negative electrode active material layer 14, and the negative electrode current collector 13. In a plan view, the buffer layer 18 is provided so as to surround the connection layer 17 and has a frame shape. The buffer layer 18 is in contact with all side surfaces of the connection layer 17. The buffer layer 18 and the connection layer 17 may be disposed apart from each other. The outer periphery of the buffer layer 18 may be located inside the outer periphery of the positive electrode current collector 11 and the negative electrode current collector 13.

[0109] The Young's modulus of the buffer layer 18 is equal to or lower than the Young's modulus of the positive electrode current collector 11, the positive electrode active material layer 12, the solid electrolyte layer 15, the negative electrode active material layer 14, and the negative electrode current collector 13. In addition, the buffer layer 18 is made of a material different from that of the connection layer 17. In this manner, the solid battery cells 1a and 1b are stacked via the connection layer 17 and the buffer layer 18 made of different materials, and therefore stress on the solid battery cells 1a and 1b is alleviated under a wider range of conditions.

[0110] The Young's modulus of the buffer layer 18 may be smaller than that of the connection layer 17. As a result, the buffer layer 18 is more easily deformed than the connection layer 17, and therefore can deform and relieve stress before the connection layer 17 does, thereby enhancing the effect of relieving stress on the solid-state battery cells 1a and 1b in the battery 120.

[0111] The buffer layer 18 may contain an inorganic solid electrolyte used in the solid electrolyte layer 15. The buffer layer 18 is formed, for example, using the same material as the inorganic solid electrolyte used in the solid electrolyte layer 15. By using the material of the solid electrolyte layer 15, which is a component of the solid battery cells 1a and 1b, as the material of the buffer layer 18, the battery 120 can be produced efficiently in the manufacturing process.

[0112] The buffer layer 18 can be formed, for example, by coating such as die coating in a normal thick film process, and a printing process using a screen and a metal mask. The buffer layer 18 may be formed after the connection layer 17 is formed, or may be formed in the reverse order. In addition, a layer of a mixed structure may be formed using a paste in which the material of the connection layer 17 and the material of the buffer layer 18 are mixed, as long as the conductivity between the solid-state battery cell 1a and the solid-state battery cell 1b is not impaired.

[0113] The buffer layer 18 may contain at least one of the solid electrolyte, the positive electrode active material, and the negative electrode active material used in the positive electrode active material layer 12 and the negative electrode active material layer 14 of the solid battery cells 1a and 1b. This allows the softness, compression characteristics under pressure, and thermal expansion and contraction characteristics of the buffer layer 18 between the solid battery cells 1a and 1b to be closer to the characteristics of the positive electrode active material layer 12 and the negative electrode active material layer 14, thereby improving the reliability of the multi-layered battery. In addition, the presence of the connection layer 17 and the buffer layer 18 having electronic conductivity between the solid battery cells 1a and 1b allows the stress relaxation performance of the solid battery cells 1a and 1b to be controlled over a wide range. Such an effect is also exhibited when the buffer layer 18 contains an inorganic solid electrolyte used in the solid electrolyte layer 15.

[0114] In addition, the buffer layer 18 may not include a conductive material. For example, the buffer layer 18 may be composed of a material obtained by removing the conductive material from the constituent material of the connection layer 17. By removing the conductive material such as metal from the material of the buffer layer 18, a material with a large Young's modulus and thermal conductivity is removed. Since the buffer layer 18 does not include a conductive material, it is likely to be softer than the connection layer 17 and has a lower thermal conductivity. As a result, the buffer layer 18 is easily deformed and is less susceptible to temperature changes, so that it functions as a buffer material against external impacts and thermal shocks, and can enhance the effect of relaxing the stress on the solid-state battery cells 1a and 1b. In addition, since the buffer layer 18 is easily deformed, the bonding between the buffer layer 18 and the current collector in contact with it is improved.

[0115] [Battery manufacturing method] Next, an example of a method for manufacturing the battery according to the present embodiment will be described. Hereinafter, a method for manufacturing the battery 120 according to the second modification of the above-mentioned embodiment will be described.

[0116] First, pastes to be used for printing the positive electrode active material layer 12 and the negative electrode active material layer 14 are prepared. As a solid electrolyte to be used for the mixture of the positive electrode active material layer 12 and the negative electrode active material layer 14, for example, a glass powder of Li2S-P2S5-based sulfide mainly composed of triclinic crystals having an average particle size of about 10 μm is prepared. As the glass powder, for example, 2 to 3×10 -3 As the positive electrode active material, for example, a glass powder having a high ionic conductivity of about 1.0 S / cm can be used. 0.8 Co 0.15 Al 0.05 O2) powder is used. A mixture containing the above-mentioned positive electrode active material and the above-mentioned glass powder is dispersed in an organic solvent or the like to prepare a paste for a positive electrode active material layer. In addition, as the negative electrode active material, for example, a powder of natural graphite having an average particle size of about 10 μm is used. A mixture containing the above-mentioned negative electrode active material and the above-mentioned glass powder is dispersed in an organic solvent or the like to prepare a paste for a negative electrode active material layer in the same manner.

[0117] Next, for example, copper foil having a thickness of about 30 μm is prepared as a material used for the positive electrode current collector 11 and the negative electrode current collector 13. For example, a paste for a positive electrode active material layer and a paste for a negative electrode active material layer are printed on one surface of each copper foil by a screen printing method in a predetermined shape and with a thickness of about 50 μm to 100 μm. The paste for a positive electrode active material layer and the paste for a negative electrode active material layer are dried at 80° C. to 130° C. to a thickness of 30 μm to 60 μm. As a result, a positive electrode plate is obtained as the positive electrode current collector 11 on which the positive electrode active material layer 12 is formed, and a negative electrode plate is obtained as the negative electrode current collector 13 on which the negative electrode active material layer 14 is formed.

[0118] Next, a paste to be used for printing the solid electrolyte layer 15 is prepared. The mixture containing the above-mentioned glass powder is dispersed in an organic solvent or the like to prepare a paste for the solid electrolyte layer. The above-mentioned paste for the solid electrolyte layer is printed, for example, to a thickness of about 100 μm on the surfaces of the positive electrode active material layer 12 of the positive electrode plate and the negative electrode active material layer 14 of the negative electrode plate using a metal mask. Thereafter, the positive electrode plate and the negative electrode plate on which the paste for the solid electrolyte layer is printed are dried at 80°C to 130°C.

[0119] Next, the positive and negative electrode plates are stacked so that the solid electrolyte printed on the positive electrode active material layer 12 of the positive electrode plate and the solid electrolyte printed on the negative electrode active material layer 14 of the negative electrode plate are in contact with and face each other.

[0120] Next, the laminate is pressed with a pressing die. Specifically, a 70 μm thick, 5×10 elastic modulus SiO2 film is placed between the laminate and the pressing die plate, that is, on the top surface of the current collector of the laminate. 6 An elastic sheet with a pressure of about 100 MPa is inserted. With this configuration, pressure is applied to the laminate via the elastic sheet. After that, the pressurizing die is pressed for 90 seconds at a pressure of 300 MPa while being heated to 50°C. This results in a solid-state battery cell 1a. Also, a solid-state battery cell 1b is obtained by the same method as above.

[0121] Next, a thermosetting conductor paste containing silver particles with an average particle size of 0.5 μm is pattern-printed by screen printing as a material for the connection layer 17 to a thickness of about 30 μm on the surface of the negative electrode current collector 13 of the solid-state battery cell 1b produced as described above. At this time, the conductor paste is printed inside the outer periphery of the negative electrode current collector 13 in a plan view. Next, a paste for a solid electrolyte layer is pattern-printed as a material for the buffer layer 18 using a metal mask. At this time, the paste for a solid electrolyte layer is printed so as to surround the outer periphery of the conductor paste in a plan view. As a result, the connection layer 17 and the buffer layer 18 are formed on the negative electrode current collector 13 of the solid-state battery cell 1b.

[0122] Next, the positive electrode current collector 11 of the solid-state battery cell 1a is placed at a predetermined position and compressed so as to be in contact with the connection layer 17 and the buffer layer 18 formed on the negative electrode current collector 13 of the solid-state battery cell 1b. After this, the solid-state battery cell 1b is compressed under a pressure of, for example, about 1 kg / cm 2 While applying this pressure, the solid-state battery cells 1a and 1b are prevented from moving, and a heat curing treatment is performed in the atmosphere at about 100°C to 300°C for 60 minutes, and then cooled to room temperature. This results in a battery 120. When three or more solid-state battery cells are stacked, the number of solid-state battery cells to be stacked is prepared, and the formation of the connection layer 17 and buffer layer 18 and the stacking of the solid-state battery cells are repeated.

[0123] The method and order of forming the battery are not limited to the above example.

[0124] In the above-mentioned manufacturing method, the positive electrode active material layer paste, the negative electrode active material layer paste, the solid electrolyte layer paste, and the conductor paste are applied by printing, but the present invention is not limited to this. As the printing method, for example, a doctor blade method, a calendar method, a spin coating method, a dip coating method, an inkjet method, an offset method, a die coating method, a spray method, etc. may be used.

[0125] In the above-mentioned manufacturing method, the conductive paste is a thermosetting conductive paste containing silver metal particles, but is not limited thereto. The conductive paste is, for example, a conductive resin paste containing metal particles and resin as main components. The conductive paste is a thermosetting conductive paste containing high-melting-point highly conductive metal particles, low-melting-point metal particles, and resin. The melting point of the high-melting-point highly conductive metal particles is, for example, 400°C or higher. Examples of materials for the high-melting-point highly conductive metal particles include silver, copper, nickel, zinc, aluminum, palladium, gold, platinum, and alloys of these metals. The melting point of the low-melting-point metal particles may be lower than the hardening temperature of the conductive paste, for example, lower than 300°C. Examples of materials for low-melting-point metal particles having a melting point of 300° C. or less include tin, tin-zinc alloy, tin-silver alloy, tin-copper alloy, tin-aluminum alloy, tin-lead alloy, indium, indium-silver alloy, indium-zinc alloy, indium-tin alloy, bismuth, bismuth-silver alloy, bismuth-nickel alloy, bismuth-tin alloy, bismuth-zinc alloy, or bismuth-lead alloy. By using a conductor paste containing such low-melting-point metal particles, solid and liquid phase reactions proceed at the contact site between the metal particles in the conductor paste and the metal constituting the current collector, even at a heat curing temperature lower than the melting point of the high-melting-point highly conductive metal particles. As a result, at the interface between the conductor paste and the surface of the current collector, a diffusion region alloyed by solid and liquid phase reactions is formed around the contact site. An example of the alloy formed is a silver-copper alloy, which is a highly conductive alloy, when silver or a silver alloy is used for the high-melting-point highly conductive metal particles and copper is used for the current collector. Furthermore, a silver-nickel alloy or a silver-palladium alloy can be formed by combining a high-melting-point highly conductive metal particle with a current collector. With this configuration, the current collector in contact with the connection layer 17 is more firmly bonded, and for example, peeling of the bond between the connection layer 17 and the current collector due to thermal cycles or impacts is suppressed.

[0126] The shape of the high melting point highly conductive metal particles and the low melting point metal particles may be any shape, such as spherical, flaky, needle-like, etc. The particle size of the high melting point highly conductive metal particles and the low melting point metal particles is not particularly limited. For example, the smaller the particle size, the lower the alloy reaction and diffusion progress at low temperature, so the particle size and shape are appropriately selected in consideration of the effect of heat history on process design and battery characteristics.

[0127] The resin used in the thermosetting conductive paste may be any resin that functions as a binder for bonding, and may be selected appropriately depending on the manufacturing process to be adopted, such as printability and applicability. The resin used in the thermosetting conductive paste may include, for example, a thermosetting resin. Examples of the thermosetting resin include (i) amino resins such as urea resin, melamine resin, and guanamine resin, (ii) epoxy resins such as bisphenol A type, bisphenol F type, phenol novolac type, and alicyclic type, (iii) oxetane resin, (iv) phenol resins such as resol type and novolac type, and (v) silicone-modified organic resins such as silicone epoxy and silicone polyester. Only one of these materials may be used as the resin, or two or more of these materials may be used in combination.

[0128] (Other embodiments) Although the battery according to the present disclosure has been described above based on the embodiments, the present disclosure is not limited to these embodiments. As long as it does not deviate from the gist of the present disclosure, various modifications conceivable by a person skilled in the art to the embodiments and other forms constructed by combining some of the components in the embodiments are also included in the scope of the present disclosure.

[0129] For example, in the above embodiment and each modified example, the positive electrode collector 11, the positive electrode active material layer 12, the solid electrolyte layer 15, the negative electrode active material layer 14, and the negative electrode collector 13 have the same shape, position, and size in a plan view, but this is not limited thereto. In a plan view, the areas of the positive electrode collector 11, the negative electrode collector 13, and the solid electrolyte layer 15 may be larger than the areas of the positive electrode active material layer 12 and the negative electrode active material layer 14, and the solid electrolyte layer 15 may be in contact with the side surfaces of the positive electrode active material layer 12 and the negative electrode active material layer 14, as well as the positive electrode collector 11 and the negative electrode collector 13. In other words, the positive electrode collector 11 is in contact with the positive electrode active material layer 12 and the solid electrolyte layer 15, and the negative electrode collector 13 is in contact with the negative electrode active material layer 14 and the solid electrolyte layer 15. In this way, even when a plurality of layers made of different materials are in contact with the positive electrode current collector 11 and the negative electrode current collector 13, the positive electrode current collector 11 and the negative electrode current collector 13 are laminated via the connection layer 16, so that the stress caused by the material of either layer can be alleviated by the connection layer 16. Therefore, damage to the positive electrode current collector 11 and the negative electrode current collector 13 due to the stress is suppressed. Furthermore, the area of ​​the negative electrode active material layer 14 may be larger than the area of ​​the positive electrode active material layer 12 in a plan view.

[0130] In the second modification of the above embodiment, the buffer layer 18 is provided to surround the connection layer 17 in a plan view and has a frame shape, but is not limited thereto. The arrangement of the buffer layer 18 and the connection layer 17 is not particularly limited as long as it does not impair the conductivity between the solid-state battery cell 1a and the solid-state battery cell 1b, and for example, the buffer layer 18 may be provided on the outside of at least one side surface of the connection layer 17. The buffer layer 18 may be provided so as to be surrounded by the connection layer 17. The buffer layer 18 and the connection layer 17 may be alternately arranged in stripes.

[0131] Furthermore, the above-described embodiment can be modified, replaced, added, omitted, and the like in various ways within the scope of the claims or their equivalents. [Industrial Applicability]

[0132] The battery according to the present disclosure can be used, for example, as a secondary battery such as an all-solid-state battery for use in various electronic devices or automobiles. [Explanation of symbols]

[0133] 11 Positive electrode current collector 12 Cathode active material layer 13 Negative electrode current collector 14 Negative electrode active material layer 15 Solid electrolyte layer 16, 17 Connection layer 18 Buffer layer 100, 110, 120 batteries

Claims

1. A plurality of solid-state battery cells; a connection layer located between the plurality of solid-state battery cells; Equipped with each of the plurality of solid-state battery cells has a structure in which a positive electrode current collector, a positive electrode active material layer, a solid electrolyte layer containing an inorganic solid electrolyte, a negative electrode active material layer, and a negative electrode current collector are laminated in this order; the plurality of solid-state battery cells are electrically connected in series; the positive electrode current collector of one of two adjacent solid-state battery cells among the plurality of solid-state battery cells and the negative electrode current collector of the other of the two adjacent solid-state battery cells are stacked via the connection layer, the connection layer includes a conductive material; the Young's modulus of the connection layer is smaller than the Young's modulus of the positive electrode current collector, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode current collector; The connection layer includes a solid electrolyte. battery.

2. The connection layer includes a resin.

10. The battery of claim 1.

3. The connection layer has an air gap.

3. The battery of claim 1 or 2.

4. The thickness of the connection layer is 1 μm or more and 20 μm or less. The battery of any one of claims 1 to 3.

5. the connection layer is located inside the outer periphery of the positive electrode current collector and the negative electrode current collector in a plan view; The battery of any one of claims 1 to 4.

6. A buffer layer is disposed between the plurality of solid-state battery cells and is made of a material different from that of the connection layer. the Young's modulus of the buffer layer is equal to or lower than the Young's modulus of the positive electrode current collector, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode current collector; 6. The battery of claim 5.

7. The buffer layer is provided so as to surround the outer periphery of the connection layer in a plan view and has a frame shape.

7. The battery of claim 6.

8. The Young's modulus of the buffer layer is smaller than the Young's modulus of the connection layer. The battery according to claim 6 or 7.

9. The buffer layer does not contain a conductive material.

9. The battery of claim 6.

10. The buffer layer contains the inorganic solid electrolyte.

10. The battery of claim 6.

11. The inorganic solid electrolyte has lithium ion conductivity. The battery of any one of claims 1 to 10.

12. A plurality of solid-state battery cells; a connection layer located between the plurality of solid-state battery cells; Equipped with each of the plurality of solid-state battery cells has a structure in which a positive electrode current collector, a positive electrode active material layer, a solid electrolyte layer containing an inorganic solid electrolyte, a negative electrode active material layer, and a negative electrode current collector are laminated in this order; the plurality of solid-state battery cells are electrically connected in series; the positive electrode current collector of one of two adjacent solid-state battery cells among the plurality of solid-state battery cells and the negative electrode current collector of the other of the two adjacent solid-state battery cells are stacked via the connection layer, the connection layer includes a conductive material; the Young's modulus of the connection layer is smaller than the Young's modulus of the positive electrode current collector, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode current collector; The connection layer has an air gap. battery.

13. A plurality of solid-state battery cells; a connection layer located between the plurality of solid-state battery cells; a buffer layer located between the plurality of solid-state battery cells and made of a different material from the connection layer; Equipped with each of the plurality of solid-state battery cells has a structure in which a positive electrode current collector, a positive electrode active material layer, a solid electrolyte layer containing an inorganic solid electrolyte, a negative electrode active material layer, and a negative electrode current collector are laminated in this order; the plurality of solid-state battery cells are electrically connected in series; the positive electrode current collector of one of two adjacent solid-state battery cells among the plurality of solid-state battery cells and the negative electrode current collector of the other of the two adjacent solid-state battery cells are stacked via the connection layer, the connection layer includes a conductive material; the Young's modulus of the connection layer is smaller than the Young's modulus of the positive electrode current collector, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode current collector; the Young's modulus of the buffer layer is equal to or lower than the Young's modulus of the positive electrode current collector, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode current collector; The Young's modulus of the buffer layer is smaller than the Young's modulus of the connection layer. battery.

14. A plurality of solid-state battery cells; a connection layer located between the plurality of solid-state battery cells; a buffer layer located between the plurality of solid-state battery cells and made of a different material from the connection layer; Equipped with each of the plurality of solid-state battery cells has a structure in which a positive electrode current collector, a positive electrode active material layer, a solid electrolyte layer containing an inorganic solid electrolyte, a negative electrode active material layer, and a negative electrode current collector are laminated in this order; the plurality of solid-state battery cells are electrically connected in series; the positive electrode current collector of one of two adjacent solid-state battery cells among the plurality of solid-state battery cells and the negative electrode current collector of the other of the two adjacent solid-state battery cells are stacked via the connection layer, the connection layer includes a conductive material; the Young's modulus of the connection layer is smaller than the Young's modulus of the positive electrode current collector, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode current collector; the Young's modulus of the buffer layer is equal to or lower than the Young's modulus of the positive electrode current collector, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode current collector; The buffer layer contains the inorganic solid electrolyte. battery.

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