Battery

Abstract

The battery of the present disclosure includes a first solid battery unit and a buffer layer. The first solid battery unit includes a positive electrode, a negative electrode, and a solid electrolyte layer located between the positive electrode and the negative electrode. The positive electrode or the negative electrode has a current collector. The buffer layer contacts the surface of the current collector on the side opposite to the solid electrolyte layer. The buffer layer contains a thermally expandable material and a conductive resin.

Description

Technical Field

[0001] The present disclosure relates to a battery. Background Art

[0002] Batteries sometimes heat up rapidly due to short circuits or the like. As a technique for suppressing such an increase in the temperature of a battery, for example, Patent Document 1 discloses a secondary battery in which a current collector is formed of a thermally expandable material. Patent Document 2 discloses a battery using a conductive material containing a foaming substance.

[0003] Prior Art Documents

[0004] Patent Document 1: International Publication No. 2011 / 062065

[0005] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2015-38876 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] There is a need in the prior art to suppress the heat generation of a battery.

[0008] Therefore, the present disclosure provides a highly reliable battery capable of suppressing the heat generation of a battery.

[0009] Means for Solving the Problems

[0010] A battery according to one aspect of the present disclosure includes a first solid battery unit and a buffer layer. The first solid battery unit includes a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode. The positive electrode or the negative electrode has a current collector. The buffer layer contacts a surface of the current collector on a side opposite to the solid electrolyte layer. The buffer layer includes a thermally expandable material and a conductive resin.

[0011] Effects of the Invention

[0012] According to the present disclosure, it is possible to realize a highly reliable battery capable of suppressing the heat generation of a battery. Brief Description of the Drawings

[0013] Figure 1 is a diagram showing a schematic structure of a battery according to an embodiment.

[0014] Figure 2 is a diagram showing a schematic structure of a battery according to Modification 1 of the embodiment.

[0015] Figure 3 is a diagram showing a schematic structure of particulate thermally expandable material and a metal layer in a buffer layer of a battery according to Modification 2 of the embodiment.

[0016] Figure 4This is a diagram showing the general structure of a stacked battery according to Modification Example 3 of the embodiment. Detailed Embodiment

[0017] (Summary of the Present Disclosure)

[0018] A battery according to one aspect of the present disclosure includes a first solid battery unit and a buffer layer. The first solid battery unit includes a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode. The positive electrode or the negative electrode has a current collector. The buffer layer contacts a surface of the current collector on a side opposite to the solid electrolyte layer. The buffer layer includes a thermally expandable material and a conductive resin.

[0019] Thus, in the case of abnormal heat generation of the battery, the thermally expandable material contained in the buffer layer can thermally expand, making the buffer layer highly resistive and thus cutting off the current. In this way, a highly reliable and high-performance battery capable of suppressing ignition and smoldering combustion can be provided.

[0020] In addition, for example, the buffer layer may further contain a metal. The metal may be at least one selected from Sn, Cu, Ag, Bi, Al, and Zn.

[0021] Thus, through the buffer layer in close contact with the current collector, the metal component can be firmly joined to the current collector, thereby achieving high impact resistance.

[0022] In addition, for example, the buffer layer may have an alloy layer at the interface with the current collector. The metal may be at least one selected from Sn, Bi, Al, and Zn. The alloy layer is composed of an alloy containing the metal.

[0023] Thus, for example, an alloy layer is formed at the bonding interface between a current collector such as Cu or Al and the buffer layer to be integrated with each other, and its effect can achieve a firm and low-resistance connection. Therefore, the battery characteristics are not deteriorated during normal battery operation, and it can function as a highly reliable buffer layer.

[0024] In addition, for example, the thermally expandable material may be particles. The particles may be coated with the metal.

[0025] Thus, in the case where the thermally expandable particles expand due to a temperature rise such as ignition, it is easy for the metal coating the thermally expandable particles to peel off, thereby cutting off the conduction path. In this way, a highly reliable and high-performance battery capable of suppressing ignition and smoldering combustion can be provided.

[0026] In addition, for example, the battery according to one aspect of the present disclosure may further include a second solid battery unit. The first solid battery unit and the second solid battery unit may be stacked with the buffer layer therebetween.

[0027] Thus, even in a multi-layered battery, its characteristics will not deteriorate, and a highly reliable and high-performance battery capable of suppressing ignition and smoldering combustion can be achieved.

[0028] In addition, for example, the solid electrolyte layer may include a solid electrolyte having lithium ion conductivity.

[0029] In addition, for example, the thermally expandable material may be foaming particles.

[0030] Thus, for example, due to the thermal expansion of the foaming particles present between the conductive resin or metal particles, it is easy to separate the conductive particles from each other, thereby cutting off the conduction path. Thus, a highly reliable and high-performance battery capable of suppressing ignition and smoldering combustion can be provided.

[0031] In addition, for example, the foaming particles may be microcapsules containing gas inside.

[0032] Thus, for example, in addition to the thermal expansion of the foaming particles, the conduction path between the conductive particles can be further separated by the gas components discharged from the particles, and the current can be more effectively cut off by the high resistance of the buffer layer. In addition, the high-resistance temperature can be controlled by the gas components.

[0033] Hereinafter, embodiments will be specifically described with reference to the drawings.

[0034] Furthermore, the embodiments described below are all illustrative or specific examples. The numerical values, shapes, materials, constituent elements, arrangement positions of the constituent elements, connection methods, etc. shown in the following embodiments are only examples, and their main purpose is not to limit the present disclosure. In addition, among the constituent elements in the following embodiments, the constituent elements not described in the independent claims are described as optional constituent elements.

[0035] In addition, the drawings are not necessarily drawn strictly. In each drawing, the same reference numerals are given to substantially the same structures, and repeated descriptions are omitted or simplified.

[0036] In addition, in this specification and the drawings, the x-axis, y-axis, and z-axis represent the three axes of a three-dimensional rectangular coordinate system. In each embodiment, the z-axis direction is taken as the thickness direction of the battery. In addition, in this specification, the "thickness direction" refers to the direction perpendicular to the plane on which each layer is stacked.

[0037] In addition, in this specification, "looking down" refers to observing the battery along the stacking direction of the battery, and the "thickness" in this specification refers to the length in the stacking direction of the battery and each layer.

[0038] In addition, in this specification, "inner" and "outer" in "inner side" and "outer side" etc. refer to the inside and outside when observing the battery along the stacking direction of the battery.

[0039] In addition, in this specification, terms such as "upper" and "lower" in the structure of the battery do not refer to the upper direction (vertically upward) and the lower direction (vertically downward) in the absolute spatial perception, but are used as terms defined by the relative positional relationship based on the stacking order in the stacked structure. In addition, terms such as "above" and "below" are applicable not only to the case where two constituent elements are arranged at intervals and there are other constituent elements between the two constituent elements, but also to the case where two constituent elements are arranged in close contact with each other and the two constituent elements are in contact.

[0040] (Embodiment)

[0041] [Overview of the battery]

[0042] First, the battery according to this embodiment will be described.

[0043] Figure 1 is a diagram showing the general structure of the battery according to this embodiment. Specifically, Figure 1 (a) is a cross-sectional view of the battery 1 according to this embodiment, Figure 1 (b) is a top view of the battery 1 observed from the positive side in the z-axis direction. Figure 1 Shown in (a) is Figure 1 the cross-section at the position indicated by the I-I line in (b). Figure 1 (c) is Figure 1 a cross-sectional view schematically enlarging a part of the cross-sectional shape shown in (a).

[0044] As Figure 1 shown, the battery 1 includes a solid battery unit 2 and a buffer layer 40. The battery 1 is an all-solid-state battery.

[0045] The solid battery unit 2 is an example of a first solid battery unit, and includes a first electrode 10, a second electrode 20, and a solid electrolyte layer 30. The first electrode 10 has a first current collector 11 and a first active material layer 12 arranged in contact with the first current collector 11. The second electrode 20 is a counter electrode of the first electrode 10, and has a second current collector 21 and a second active material layer 22 arranged in contact with the second current collector 21. The solid electrolyte layer 30 is located between the first electrode 10 and the second electrode 20, and is in contact with the first active material layer 12 and the second active material layer 22. The buffer layer 40 is in contact with the surface of the first current collector 11 on the side opposite to the solid electrolyte layer 30. The buffer layer 40 includes a thermally expandable material 41 and a resin 43.

[0046] As Figure 1As shown, the first current collector 11 and the buffer layer 40 of the solid battery cell 2 have the same shape, position, and size in plan view. From the viewpoint of reducing the resistance of the contact portion, it is advantageous that the entire surface of the first current collector 11 on the side of the buffer layer 40 is in contact with the buffer layer 40.

[0047] [Solid battery cell]

[0048] Hereinafter, the details of each component of the solid battery cell 2 will be described.

[0049] The first current collector 11, the first active material layer 12, the solid electrolyte layer 30, the second active material layer 22, the second current collector 21, and the buffer layer 40 are each rectangular in plan view. There is no particular limitation on the shape of the first current collector 11, the first active material layer 12, the solid electrolyte layer 30, the second active material layer 22, the second current collector 21, and the buffer layer 40 in plan view, and it may be a shape other than a rectangle such as a circle, an ellipse, or a polygon.

[0050] In the present embodiment, the first electrode 10 is the positive electrode and the second electrode 20 is the negative electrode. That is, the first current collector 11 is the positive electrode current collector and the first active material layer 12 is the positive electrode active material layer. The second current collector 21 is the negative electrode current collector and the second active material layer 22 is the negative electrode active material layer. The buffer layer 40 is connected to the positive electrode current collector.

[0051] Furthermore, it may be set that the first electrode 10 is the negative electrode and the second electrode 20 is the positive electrode. That is, it may be set that the first current collector 11 is the negative electrode current collector and the first active material layer 12 is the negative electrode active material layer. It may be set that the second current collector 21 is the positive electrode current collector and the second active material layer 22 is the positive electrode active material layer. It may be set that the buffer layer 40 is connected to the negative electrode current collector.

[0052] Furthermore, in this specification, the first current collector 11 and the second current collector 21 may be collectively referred to as "current collectors". Furthermore, the current collector only needs to be formed of a conductive material and is not particularly limited.

[0053] As the current collector, for example, a foil-like body, a plate-like body, or a net-like body made of stainless steel, nickel (Ni), aluminum (Al), iron (Fe), titanium (Ti), copper (Cu), palladium (Pd), gold (Au), or platinum (Pt), or an alloy of two or more of these may be used. The material of the current collector can be appropriately selected in consideration of the manufacturing process, no melting and decomposition under the use temperature and use pressure, and the working potential and conductivity of the battery applied to the current collector. In addition, the material of the current collector can also be selected according to the required tensile strength and heat resistance. The current collector can be, for example, a high-strength electrolytic copper foil or a clad material in which different metal foils are laminated.

[0054] The thickness of the current collector is, for example, in the range of 10 μm or more and 100 μm or less. Further, from the viewpoint of firmly bonding the surface of the current collector to the first active material layer 12, the second active material layer 22, and the buffer layer 40, a current collector having a rough surface with irregularities can be used. In addition, an adhesive component such as an organic adhesive can be coated on the surface of the current collector. Thereby, the bonding property of the interface between the current collector and other layers is strengthened. Not only in terms of the mechanical and thermal reliability and cycle characteristics of the battery, but also in terms of the bonding property with the buffer layer 40, the in-plane operation of the buffer layer 40, that is, the in-plane characteristics of high resistance and current interruption are made uniform, and its reliability can be improved.

[0055] The first active material layer 12 is disposed in contact with one surface of the first current collector 11. In the present embodiment, since the first active material layer 12 is a positive electrode active material layer, the first active material layer 12 contains at least a positive electrode active material. The first active material layer 12 is a layer mainly composed of a positive electrode material such as a positive electrode active material. The positive electrode active material is a material that inserts or extracts metal ions such as lithium (Li) ions or magnesium (Mg) ions into or from the crystal structure at a potential higher than that of the negative electrode, and is oxidized or reduced accordingly. The type of the positive electrode active material can be appropriately selected according to the type of the battery, and a known positive electrode active material can be used.

[0056] Examples of the positive electrode active material include compounds containing lithium and transition metal elements. For example, oxides containing lithium and transition metal elements, and phosphate compounds containing lithium and transition metal elements can be cited. As the oxide containing lithium and transition metal elements, for example, LiNi x M 1-x O2 (where M is at least one element selected from 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 cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), and lithium manganese oxide (LiMn2O4), or lithium manganese oxide having a spinel structure (for example, LiMn2O4, Li2MnO3, LiMnO2). As the phosphate compound containing lithium and transition metal elements, for example, lithium iron phosphate (LiFePO4) having an olivine structure can be used. In addition, as the positive electrode active material, sulfides such as sulfur (S) and lithium sulfide (Li2S) can also be used. In this case, a material obtained by coating or adding lithium niobate (LiNbO3) or the like to the positive electrode active material particles can be used as the positive electrode active material. Further, as the positive electrode active material, only one of these materials can be used, or two or more of these materials can be used in combination.

[0057] As described above, the first active material layer 12 that becomes the positive electrode active material layer only needs to contain a positive electrode active material. The positive electrode active material layer may be a binder layer composed of a binder of a positive electrode active material and other additive materials. As other additive materials, for example, solid electrolytes such as inorganic solid electrolytes or sulfide solid electrolytes, conductive aids such as acetylene black, and binder adhesives such as polyethylene oxide or polyvinylidene fluoride can be used. By mixing the positive electrode active material and other additive materials such as solid electrolytes in a predetermined ratio, the lithium ion conductivity in the positive electrode active material layer can be improved, and the electron conductivity can also be improved.

[0058] Furthermore, the thickness of the first active material layer 12 is, for example, 5 μm or more and 300 μm or less, but is not limited thereto.

[0059] The second active material layer 22 is disposed in contact with one surface of the second current collector 21. In the present embodiment, since the second active material layer 22 is a negative electrode active material layer, the second active material layer 22 contains at least a negative electrode active material. The second active material layer 22 is a layer mainly composed of a negative electrode material such as a negative electrode active material. The negative electrode active material is a material that inserts or removes metal ions such as lithium (Li) ions or magnesium (Mg) ions into or from the crystal structure at a potential lower than that of the positive electrode, and is oxidized or reduced accordingly. The types of positive and negative electrode active materials can be appropriately selected according to the type of battery, and known negative electrode active materials can be used.

[0060] As the negative electrode active material, for example, carbon materials such as natural graphite, artificial graphite, graphite carbon fiber or resin-fired carbon, and alloy-based materials combined with a solid electrolyte binder can be used. As the alloy-based materials, for example, 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 and transition metal element oxides such as lithium titanate (Li4Ti5O 12 )), metal oxides such as zinc oxide (ZnO) or silicon oxide (SiO x )), etc. Furthermore, as the negative electrode active material, only one of these materials can be used, or two or more of these materials can be used in combination.

[0061] As described above, the second active material layer 22 serving as the negative electrode active material layer only needs to contain at least a negative electrode active material. The negative electrode active material layer may be a binder layer composed of a binder of a negative electrode active material and other additive materials. As other additive materials, for example, solid electrolytes such as inorganic solid electrolytes or sulfide solid electrolytes, conductive aids such as acetylene black, and binder adhesives such as polyethylene oxide or polyvinylidene fluoride can be used. By mixing the negative electrode active material and other additive materials such as solid electrolytes in a predetermined ratio, the lithium ion conductivity within the negative electrode active material layer can be improved, and the electron conductivity can also be improved.

[0062] Furthermore, the thickness of the second active material layer 22 is, for example, 5 μm or more and 300 μm or less, but is not limited thereto.

[0063] The solid electrolyte layer 30 is disposed between the first active material layer 12 and the second active material layer 22 and is in contact with each of them. The solid electrolyte layer 30 contains at least a solid electrolyte. The solid electrolyte layer 30 contains, for example, a solid electrolyte as a main component.

[0064] The solid electrolyte may be any known solid electrolyte for batteries having ion conductivity. As the solid electrolyte, for example, a solid electrolyte that conducts metal ions such as Li lithium ions or Mg magnesium ions can be used. The type of solid electrolyte can be appropriately selected according to the type of conductive ions. For example, inorganic solid electrolytes such as sulfide solid electrolytes or oxide solid electrolytes can be used as the solid electrolyte. As sulfide solid electrolytes, for example, lithium-containing sulfides such as Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, Li2S-SiS2-LiI, Li2S-SiS2-Li3PO4, Li2S-Ge2S2, Li2S-GeS2-P2S5, or Li2S-GeS2-ZnS can be used. As oxide solid electrolytes, for example, lithium-containing metal oxides such as Li2O-SiO2 or Li2O-SiO2-P2O5, Li x P y O 1-z N z and other lithium-containing metal nitrides, and lithium-containing transition metal oxides such as lithium phosphate (Li3PO4) and lithium titanium oxide can be used. As the solid electrolyte, only one of these materials can be used, or two or more of these materials can be used in combination. In the present embodiment, as an example, the solid electrolyte layer 30 contains a solid electrolyte having lithium ion conductivity.

[0065] Furthermore, in addition to the above solid electrolyte materials, the solid electrolyte layer 30 may further contain binder adhesives such as polyethylene oxide or polyvinylidene fluoride.

[0066] Furthermore, the thickness of the solid electrolyte layer 30 is, for example, 5 μm or more and 150 μm or less, but is not limited thereto.

[0067] Furthermore, the material of the solid electrolyte may be configured as an aggregate of particles. In addition, the material of the solid electrolyte may also be composed of a sintered structure.

[0068] [Buffer layer]

[0069] Next, the specific structure of the buffer layer 40 will be described.

[0070] The buffer layer 40 is a conductive layer. The buffer layer 40 is used for the electrical connection between the solid battery unit 2 and other solid battery units or other components. In addition, the buffer layer 40 also plays a role in mitigating the impact on the solid battery unit 2.

[0071] The buffer layer 40 contains a thermal expansion material 41 having thermal expansibility and a conductive resin 43. The conductive resin 43 contains, for example, a thermosetting resin such as an epoxy resin and conductive particles such as Ag. The conductive resin 43 may be a resin containing conductive fillers such as metal particles in an insulating resin, or may be a conductive polymer containing no conductive fillers.

[0072] The thermal expansion material 41 includes at least one of a thermal expansion resin or thermal expansion particles that expand due to a temperature rise.

[0073] As the thermal expansion resin, known thermal expansion resins can be used. For example, thermal expansion resins include polymers such as polyamide (PA), polyimide, polyamideimide, wholly aromatic polyamide, polyetherimide, polysulfone, polyethersulfone, polyethylene terephthalate (PET), polyetheretherketone (PEEK), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), and polyethylene (PE). These polymers can be used alone or in combination of two or more. In addition, they can be used in combination with the thermal expansion particles described later.

[0074] The thermal expansion particles are, for example, foaming particles. The foaming particles are microcapsules containing gas inside. Specifically, the foaming particles are thermal expansion microcapsules in which a low-boiling gas is filled in minute capsules made of a thermoplastic resin. The material of the microcapsule, that is, the shell, is not particularly limited as long as it is electrochemically stable and exhibits a strength such that it can maintain its shape even after expansion, and may also be the above-mentioned thermal expansion resin. In addition, the thermal expansion material filled in the microcapsule is not particularly limited as long as it does not affect the properties of the battery even if it leaks from the microcapsule, and may be, for example, a low-boiling gas such as a low-boiling hydrocarbon. In addition, for example, thermal expansion particles having an average particle diameter of about 10 μm are used.

[0075] The heat expansion start temperature of the microcapsules of the heat-expandable particles is, for example, in the range of 150°C or higher and 250°C or lower. The heat expansion start temperature can be, for example, 200°C, or can be 180°C or lower. Regarding the heat expansion rate, as long as it can make the microstructure of the conductive resin discontinuous and separated, and cut off the conduction between the buffer layers 40, various heat expansion rates can be adopted according to the design. Furthermore, cutting off the conduction between the buffer layers 40 means increasing the resistance to a high level between the joined current collectors. In order to divide the microstructure of the conductive resin, the heat expansion rate of the heat-expandable particles is, for example, 30 times or more and 80 times or less. As the heat-expandable particles, particles with different heat expansion rates can be mixed and used.

[0076] Furthermore, the temperature for suppressing abnormal heat generation, that is, the temperature at which heat generation stops, can be adjusted by appropriately selecting and combining heat-expandable materials 41 such as heat-expandable particles and heat-expandable resins. If the heat expansion temperature can be adjusted to a desired temperature, the heat-expandable material 41 can be expanded before the battery catches fire or smokes and burns due to abnormal heat generation, thereby cutting off the current. In addition, in the buffer layer 40, in addition to the heat-expandable particles, for example, a bonding adhesive such as polyethylene oxide or polyvinylidene fluoride can also be contained.

[0077] Furthermore, the buffer layer 40 can contain a high thermal conductivity material within a range that does not deteriorate the battery characteristics. Thereby, by quickly and uniformly promoting heat conduction within the buffer layer 40, the current collector can be electrically separated from the buffer layer 40. As the high thermal conductivity material, for example, powders such as alumina or aluminum nitride with high insulation or various metal powders can be used. Furthermore, as the high heat conduction material, for example, a heat-expandable resin such as an epoxy resin can be used.

[0078] In addition, for example, the thickness of the buffer layer 40 is 5 μm or more and 300 μm or less, but it is not limited thereto.

[0079] In addition, for example, regarding the Young's modulus of the conductive resin 43 of the buffer layer 40, from the function of the buffer layer 40, it is expected to be lower than the Young's modulus of the current collector. Thereby, the stress at the interface between the solid battery unit 2 and the buffer layer 40 generated due to temperature change or external stress is alleviated. Thus, the generation of voids at the connection interface between the current collector and the buffer layer 40 and the generation of poor connection resistance during normal battery operation can be suppressed. In addition, since the buffer layer 40 is easily deformed following the shape between the surface of the current collector and the heat-expandable particles during the lamination and pressing process, the buffer layer 40 can be obtained with high reliability. Regarding the relative relationship of their Young's moduli, the relative relationship can be compared based on the displacement characteristics with respect to the pressure or the size of the indentation when pressing the probe.

[0080] In addition, considering the manufacturing difficulty in the manufacturing process, as well as the stress relaxation performance, heat shock resistance, and heat and cold cycle resistance, the buffer layer 40 can be used by adjusting the types, shapes, and combinations of various materials. Pores can be appropriately formed in the buffer layer 40 to adjust the Young's modulus of the buffer layer 40. Furthermore, the pore state can be confirmed by common cross-sectional observation methods such as optical microscopes or electron microscopes. In addition, analysis can also be performed on any cross-section by means such as CT scanning (Computed Tomography).

[0081] In addition, in the buffer layer 40, in addition to the thermal expansion material 41, the conductive resin 43 can contain a material including particles of a solid electrolyte, an active material, and a current collector material. As a result, the expansion and contraction characteristics of the buffer layer 40 and the solid battery unit 2 become closer. Therefore, the stress generated between the buffer layer 40 and the current collector during temperature changes or charge and discharge is alleviated, and a battery 1 with a high-resistance temperature characteristic with high reliability can be realized.

[0082] In addition, the buffer layer 40 may not be formed on the entire surface of the current collector, and may be partially formed by forming a pattern or the like on the surface of the adjacent current collector. That is, the buffer layer 40 only needs to have a structure connected in series with the current collector.

[0083] In addition, there is no particular limitation on the thickness of the buffer layer 40, but from the perspective of the volume energy density of the battery 1, the thinner the better. Therefore, it can be thinned within a range that can ensure the reliability such as the withstand voltage and current resistance characteristics of the buffer layer 40. The thickness of the buffer layer 40 is, for example, 1 μm or more and 100 μm or less, preferably 2 μm or more and 10 μm or less. With such a structure, a decrease in the volume energy density can be suppressed, and it is easy to alleviate the stress generated due to the expansion or contraction of the current collector caused by temperature changes.

[0084] In addition, there is no particular limitation on the specific gravity of the buffer layer 40, and from the perspective of the weight energy density, a smaller value is preferred. For example, the specific gravity of the buffer layer 40 can be less than the specific gravity of the current collector made of a metal material. Thereby, the influence on the weight energy density can be reduced.

[0085] [Effects, etc.]

[0086] Comparing the structure of the battery 1 according to the present embodiment with the structures of the batteries described in Patent Document 1 and Patent Document 2, there are the following differences.

[0087] First, Patent Document 1 discloses a secondary battery in which a current collector is formed of a thermally expandable material 41. However, in the battery described in Patent Document 1, the thermally expandable material is the current collector, and the electrolyte is a polymer solid electrolyte. That is, the structure of the battery described in Patent Document 1 is different from that of the battery 1 according to the present embodiment.

[0088] As in the case of the battery described in Patent Document 1, in the case of a current collector made of a thermally expandable material, the conductivity deteriorates compared to a current collector such as Cu, and the resistance at the bonding interface between the active material and the current collector becomes high. Therefore, the charge and discharge characteristics of the battery deteriorate. In addition, when bonding to a solid-state power generation element using a rigid solid electrolyte, there is a problem that structural defects such as peeling are caused by the stress of Joule heat due to the resistance at the interface, deteriorating the cycle characteristics.

[0089] In addition, Patent Document 2 discloses a battery using a conductive material containing a foaming substance. However, the conductive material layer containing the foaming substance is in contact with the active material layer in the same manner as in Patent Document 1. Therefore, the same problems as those in Patent Document 1 exist. In addition, the battery disclosed in Patent Document 2 is not a battery containing a solid electrolyte.

[0090] In contrast, according to the battery 1 according to the present embodiment, a buffer layer 40 containing a thermally expandable material 41 is provided on the side of the current collector opposite to the surface on which the active material layer is provided. That is, the buffer layer 40 containing the thermally expandable material 41 is provided as a component different from the current collector on the current collector. Therefore, it is possible to suppress an increase in the resistance at the bonding interface between the active material and the current collector. Furthermore, in Patent Document 1 and Patent Document 2, there is no disclosure or suggestion regarding a battery in which the buffer layer 40 formed by containing the thermally expandable material 41 in the conductive resin 43 is disposed on the surface opposite to the active material layer of the current collector.

[0091] As described above, according to the battery 1 according to the present embodiment, it is possible to suppress the ignition and smoking combustion of the battery accompanied by heat generation or overcurrent. That is, it is possible to realize a highly reliable and high-performance battery 1.

[0092] [Modification Example 1]

[0093] Hereinafter, Modification Example 1 of the embodiment will be described. Furthermore, in the following description of Modification Example 1, the description will focus on the differences from the embodiment, and the description of the common points will be omitted or simplified.

[0094] Figure 2 It is a diagram showing a schematic structure of the battery according to Modification Example 1 of the embodiment. Specifically, Figure 2 (a) is a cross-sectional view of the battery 100 according to Modification Example 1, Figure 2(b) is a top view of the battery 100 as viewed from the positive side in the z-axis direction. Figure 2 shown in (a) Figure 2 a cross-section at the position shown by line II-II in (b). Figure 2 (c) is Figure 2 a cross-sectional view schematically enlarging a part of the cross-sectional shape shown in (a).

[0095] As Figure 2 shown, the battery 100 according to Modification 1 of the embodiment is different from the battery 1 according to the embodiment in that it includes a buffer layer 140 instead of the buffer layer 40. The buffer layer 140 includes a metal 142 and a resin 143. In addition, the buffer layer 140 includes an alloy layer 144 in contact with the current collector. The alloy layer 144 mainly contains the metal 142. The alloy layer 144 is a layer in which the low-melting-point metal 142 diffuses into the current collector, firmly joining the current collector and the buffer layer 140. For example, in the formation of the alloy layer 144, first, a resin layer containing a low-melting-point metal 142 in a thermosetting resin is heat-treated at an appropriate temperature to cure it. Thereby, the alloy layer 144 can be formed by diffusion from the resin layer into the current collector.

[0096] As the metal 142, for example, there is at least one selected from Sn (tin), Ag (silver), Cu (copper), bismuth (Bi), Al (aluminum), and Zn (zinc), or an alloy thereof. Alternatively, the metal 142 can be at least one selected from Sn, Al, Mg, and Zn other than Ag and Cu which are metal elements contained in a general conductive resin.

[0097] The low-melting-point metal is, for example, a metal having a melting point of 300°C or lower. Specifically, tin, a tin-zinc alloy, a tin-silver alloy, a tin-copper alloy, a tin-aluminum alloy, a tin-lead alloy, indium, an indium-silver alloy, an indium-zinc alloy, an indium-tin alloy, bismuth, a bismuth-silver alloy, a bismuth-nickel alloy, a bismuth-tin alloy, a bismuth-zinc alloy, or a bismuth-lead alloy can be used. For example, when the current collector is Cu, if Sn is used as the metal 142 for heat treatment, an alloy layer 144 of the metal 142 can be formed at the interface by diffusion of the tin-copper alloy. In the case of using a low-melting-point metal 142, a firm bonding interface can be obtained by bonding even at a temperature about half of the melting point. Furthermore, if the particle size of the metal 142 is small, the temperature for alloying and diffusion is lowered.

[0098] Furthermore, the content ratio of the metal 142 is, for example, 1 vol% to 10 vol% based on the volume ratio of the buffer layer 140. The content and composition are adjusted from the viewpoints of the thickness of the alloy layer 144 and the bonding strength. In addition, the thickness of the alloy layer 144 etc. can be appropriately adjusted according to the heat treatment temperature.

[0099] Furthermore, in this modification example, the resin 143 is a conductive resin in the same manner as the conductive resin 43 according to the first embodiment. Alternatively, the resin 143 may be an insulating resin. That is, the metal 142 can perform the conductive function of the buffer layer 140. In the resin 143, not only the metal 142 for alloying with the current collector is included, but also metal powders generally used as electrodes such as Ag, Ni, Pd, or Pt may be mixed and contained. Alternatively, a metal material obtained by alloying these metal powders with the metal 142 may be adjusted and used within a range where conductivity and ohmic contact can be ensured.

[0100] In this modification example, the buffer layer 140 may also be composed of multiple layers of different materials, for example, multiple layers with different composition ratios of the thermal expansion material 41 and the metal 142.

[0101] As described above, according to the battery 100 according to the first modification example, the current collector and the buffer layer 140 can be firmly joined. Therefore, for impact resistance, thermal cycling, and thermal cycling, a battery 100 with higher reliability of the buffer layer 140 can be achieved.

[0102] [Modification Example 2]

[0103] Hereinafter, a second modification example of the embodiment will be described. Furthermore, in the following description of the second modification example, the description will focus on the differences from the embodiment and the first modification example, and the description of the common points will be omitted or simplified.

[0104] Figure 3 is a diagram showing a schematic structure of the particulate thermal expansion material and the metal layer in the buffer layer of the battery according to the second modification example. As Figure 3 shown, the surface of the particulate thermal expansion material 41 is coated with the metal layer 242. In the first modification example of the embodiment, it is a structure in which the particulate thermal expansion material 41 and the metal 142 are mixed and dispersed, but in the second modification example, the particulate thermal expansion material 41 is coated with the metal layer 242.

[0105] According to such a structure, the connection between the particulate thermal expansion material 41 and the metal layer 242 is made by a conductor covering the surface. When heated, the conductor structure of the metal layer 242 on the surface expands and the resistance increases. Thereby, a battery having a function of suppressing battery heating can be realized.

[0106] Furthermore, the coating of the metal layer 242 can be formed by powder coating or vapor deposition treatment such as a mechanical particle compounding process. The coating thickness of the metal layer 242 is, for example, 1 μm or less.

[0107] As described above, according to the battery according to the second modification example, the ignition and smoking combustion of the battery associated with heat generation or overcurrent can be suppressed. That is, a highly reliable and high-performance battery can be realized.

[0108] Furthermore, the thermally expandable material 41 covered with the metal layer 242 according to Modification 2 can be included in the conductive resin 43 or the resin 143 as the thermally expandable material 41 of each of the embodiment and Modifications 1 and 3.

[0109] [Modification 3]

[0110] Hereinafter, Modification 3 of the embodiment will be described. Furthermore, in the following description of Modification 3, the description will focus on the differences from the embodiment, and the description of the common points will be omitted or simplified.

[0111] Figure 4 FIG. is a diagram showing a schematic structure of a battery according to Modification 3 of the embodiment. Specifically, Figure 4 (a) is a cross-sectional view of the stacked battery 300 according to Modification 3, Figure 4 (b) is a plan view of the stacked battery 300 viewed from the positive side in the z-axis direction. Figure 4 In (a), Figure 4 a cross-section at the position shown by the line IV-IV in (b) is shown.

[0112] As Figure 4 shown, the stacked battery 300 according to Modification 3 is different from the battery 1 in the embodiment in that two solid battery units 2 are stacked and connected with a buffer layer 40 interposed therebetween.

[0113] The two solid battery units 2 are each an example of a first solid battery unit and a second solid battery unit. The two solid battery units 2 are stacked with the buffer layer 40 interposed therebetween and are electrically connected in series, respectively.

[0114] In Figure 4 the example shown, the positive electrode current collectors of the two solid battery units 2 are connected to each other. Furthermore, as described in the embodiment, the first current collector 11 may also be a negative electrode current collector. That is, the stacked battery 300 may also include two solid battery units 2 in which the negative electrode current collectors are connected to each other. The number of stacked solid battery units 2 may also be three or more.

[0115] According to this structure, in the case where a short circuit or abnormal heat generation occurs in one of the solid battery units 2, the current is cut off by an increase in the resistance of the buffer layer 40.

[0116] As described above, according to the stacked battery 300 according to Modification 3, it is possible to suppress the ignition and smoking combustion of the battery accompanied by heat generation or overcurrent. That is, it is possible to realize a battery with high reliability and large capacity.

[0117] [Method for manufacturing battery]

[0118] Next, an example of the manufacturing method of the battery according to this embodiment will be described. Hereinafter, the manufacturing method of the battery 1 according to the above embodiment will be described. First, pastes used in the printing formation of the first active material layer (hereinafter referred to as the positive electrode active material layer) 12 and the second active material (hereinafter referred to as the negative electrode active material layer) 22 are prepared. As the solid electrolyte raw material used in each binder of the positive electrode active material layer and the negative electrode active material layer, for example, glass powder of a Li2S-P2S5-based sulfide with an average particle size of about 10 μm and mainly composed of triclinic crystals is prepared. As this glass powder, for example, glass powder with a high ionic conductivity of about 2×10 -3 S / cm to 3×10 -3 S / cm can be used. As the positive electrode active material, for example, powder of a layered-structured LiNiCoAl composite oxide (specifically LiNi 0.8 Co 0.15 Al 0.05 O2) with an average particle size of about 5 μm is used. A paste for the positive electrode active material layer is prepared by dispersing a binder containing the above positive electrode active material and the above glass powder in an organic solvent or the like. In addition, as the negative electrode active material, for example, powder of natural graphite with an average particle size of about 10 μm is used. Similarly, a paste for the negative electrode active material layer is prepared by dispersing a binder containing the above negative electrode active material and the above glass powder in an organic solvent or the like.

[0119] Next, as the material for the first current collector 11 (hereinafter referred to as the positive electrode current collector) and the second current collector 21 (hereinafter referred to as the negative electrode current collector), for example, a copper foil with a thickness of about 30 μm is prepared. By using the screen printing method, the paste for the positive electrode active material layer and the paste for the negative electrode active material layer are respectively printed on the surface of one side of each copper foil in a predetermined shape and with a thickness of about 50 μm to 100 μm. The paste for the positive electrode active material layer and the paste for the negative electrode active material layer become a thickness of about 30 μm to 60 μm by drying in the range of 80°C to 130°C. Thus, current collectors (copper foils) respectively formed with the positive electrode active material layer and the negative electrode active material layer are obtained, that is, the first electrode 10 (hereinafter referred to as the positive electrode) and the second electrode 20 (hereinafter referred to as the negative electrode).

[0120] Next, a paste for the solid electrolyte layer is prepared by dispersing a binder containing the above glass powder in an organic solvent or the like. On the surface of the active material layer of each of the positive electrode and the negative electrode, using a metal mask, the above paste for the solid electrolyte layer is printed with a thickness of, for example, about 100 μm. Then, the positive electrode and the negative electrode printed with the paste for the solid electrolyte layer are dried in the range of 80°C to 130°C.

[0121] Next, the solid electrolyte printed on the positive electrode active material layer of the positive electrode and the solid electrolyte printed on the negative electrode active material layer of the negative electrode are laminated in contact with and facing each other.

[0122] Next, between the pressure die plate, an elastic sheet having an elastic modulus of about 5×10 6 Pa is inserted on the upper surface of the current collector. The thickness of the elastic sheet is, for example, 70 μm. Then, the pressure die plate is heated to 50°C under a pressure of 300 MPa and pressed for 90 seconds.

[0123] Through the above processes, the solid battery unit 2 is fabricated.

[0124] Next, to the thermosetting conductive resin paste containing silver particles with an average particle size of 0.5 μm, a particulate thermal expansion material 41 with an average particle size of about 5 μm is added and dispersed by three rollers to fabricate a resin paste containing the thermal expansion material 41 (i.e., the resin paste for the buffer layer 40). At this time, the resin paste for the buffer layer 140 can be fabricated by further adding Sn powder with an average particle size of 0.5 μm as the metal 142. Next, on the surface of the current collector of the fabricated solid battery unit 2, the resin paste for the buffer layer 40 or 140 is printed using a metal mask. Then, a heat curing treatment is performed at 120°C for 1 hour using a dryer and cooled to room temperature, thereby forming the buffer layer 40 or 140 from the resin paste for the buffer layer 40 or 140.

[0125] Through the above processes, the battery 1 is fabricated. Furthermore, the formation method and sequence of the battery 1 are not limited to the above examples.

[0126] Furthermore, in the above manufacturing method, examples of coating the paste for the positive electrode active material layer, the paste for the negative electrode active material layer, the paste for the solid electrolyte layer, and the resin paste for the buffer layer 40 or 140 by printing are shown, but are not limited thereto. As the printing method, for example, a doctor blade method, a calendering method, a spin coating method, a dip coating method, an inkjet method, an offset printing method, a die coating method, a spraying method, etc. can also be adopted.

[0127] In the above manufacturing method, as the resin paste for the buffer layer 40 or 140, a thermosetting conductive resin paste containing silver metal particles and / or Sn particles is exemplified, but it is not limited thereto. As the conductive resin paste, for example, a conductive resin paste containing high-conductivity metal particles with a melting point of 400 °C or higher, or low-melting-point metal particles with a melting point of 300 °C or lower, which is below the curing temperature of the conductive resin paste, can be used. As the material of the high-conductivity metal particles with a high melting point, for example, silver, copper, nickel, zinc, aluminum, palladium, gold, platinum, or an alloy formed by combining these metals can be cited. As the low-melting-point metal material with a melting point of 300 °C or lower, for example, 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, etc. can be cited. By using a conductive resin paste containing such low-melting-point metal particles, at the contact part with the metal constituting the current collector, by the effect of increasing the surface area of the powder, that is, the effect of increasing the reaction area, the solid-phase and liquid-phase reactions are carried out at a lower temperature. Thus, in the interface between the buffer layer 40 or 140 and the surface of the current collector, a diffusion region alloyed by the solid-phase and liquid-phase reactions is formed over the interface of the above contact part. Therefore, the buffer layer 40 or 140 can be firmly joined at the interface with the current collector. As an example of the formed alloy, in the case where silver or a silver alloy is used for the conductive metal particles and copper is used for the current collector, due to the reaction-promoting effect of Cu, a silver-copper-based alloy of a high-conductivity alloy is easily formed. With this structure, the buffer layer 40 or 140 is joined more firmly with the current collector. Thus, for example, an effect of suppressing the peeling of the buffer layer 40 or 140 due to thermal cycling or shock can be obtained.

[0128] Furthermore, the shapes of the high-conductivity metal particles with a high melting point and the low-melting-point metal particles can be any shape such as spherical, flaky, needle-like, etc. In addition, there is no particular limitation on the particle size of the high-conductivity metal particles with a high melting point and the low-melting-point metal particles. For example, since the smaller the particle size, the alloy reaction and diffusion will occur at a lower temperature, the particle size and shape are appropriately selected in consideration of the process design and the influence of the thermal history on the battery characteristics.

[0129] In addition, the resin used in the thermosetting conductive resin paste only needs to be a resin that functions as a bonding adhesive, and an appropriate resin is selected according to the manufacturing process such as printability and coatability. The resin used in the thermosetting conductive resin paste includes, 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) phenolic resins such as resol type and novolac type, and (v) silicone-modified organic resins such as silicone epoxy resin and silicone polyester. The resin may use only one of these materials, or two or more of these materials may be used in combination.

[0130] (Other Embodiments)

[0131] As described above, the battery according to the present disclosure has been described based on the embodiments, but the present disclosure is not limited to these embodiments. As long as it does not deviate from the gist of the present disclosure, a variety of modifications conceivable by those skilled in the art applied to the embodiments, or other schemes constructed by combining a part of the constituent elements in the embodiments, are included in the scope of the present disclosure.

[0132] In addition, the above embodiments can be variously changed, replaced, added, omitted, etc. within the scope of the claims or the equivalent scope thereof.

[0133] Industrial Applicability

[0134] The battery according to the present disclosure can be used, for example, as a secondary battery such as an all-solid-state battery used in various electronic devices or automobiles.

[0135] Explanation of Reference Numerals

[0136] 1, 100 Battery

[0137] 2 Solid Battery Unit

[0138] 10 First Electrode (Positive Electrode)

[0139] 11 First Current Collector (Positive Current Collector)

[0140] 12 First Active Material Layer (Positive Active Material Layer)

[0141] 20 Second Electrode (Negative Electrode)

[0142] 21 Second Current Collector (Negative Current Collector)

[0143] 22 Second Active Material Layer (Negative Active Material Layer)

[0144] 30 Solid Electrolyte Layer

[0145] 40 and 140 Buffer layers

[0146] 41 Thermally expandable material

[0147] 43 Conductive resin

[0148] 142 Metal

[0149] 143 Resin

[0150] 144 Alloy layer

[0151] 242 Metal layer

[0152] 300 Stacked battery

Claims

1. A battery comprising a first solid battery unit and a buffer layer, The first solid battery unit includes a positive electrode, a negative electrode, and a solid electrolyte layer located between the positive electrode and the negative electrode, The positive electrode or the negative electrode has a current collector, The buffer layer contacts the surface of the current collector on the side opposite to the solid electrolyte layer, The buffer layer contains a thermally expandable material and a conductive resin, The thermally expandable material is foaming particles, The buffer layer further contains a metal, The metal is at least one selected from Sn, Cu, Ag, Bi, Al, and Zn, The buffer layer has an alloy layer at the interface with the current collector, The alloy layer is composed of an alloy containing the metal.

2. The battery according to claim 1, The metal is at least one selected from Sn, Bi, Al, and Zn.

3. The battery according to claim 1 or 2, The foaming particles are coated with the metal.

4. The battery according to claim 1 or 2, Further comprising a second solid battery unit, The first solid battery unit and the second solid battery unit are stacked with the buffer layer therebetween.

5. The battery according to claim 1 or 2, The solid electrolyte layer contains a solid electrolyte having lithium ion conductivity.

6. The battery according to claim 1 or 2, The foaming particles are microcapsules containing gas inside.

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