Battery

Abstract

The battery disclosed herein comprises a first solid battery cell and a buffer layer, wherein the first solid battery cell comprises a positive electrode, a negative electrode, and a solid electrolyte layer located between the positive electrode and the negative electrode, wherein the positive electrode or the negative electrode has a current collector, and the buffer layer contacts the surface of the current collector opposite to the solid electrolyte layer, and the buffer layer comprises a PTC material, a resin, and a first metal, wherein the first metal is at least one selected from Sn, Cu, Al, Mg, and Zn.

Description

Technical Field

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

[0002] Batteries may generate heat rapidly due to short circuits, etc. As a technology to suppress such a rise in battery temperature, for example, Patent Document 1 discloses an all-solid-state battery in which a collector having a PTC (Positive Temperature Coefficient) characteristic is formed on a positive electrode active material. Patent Document 2 discloses an all-solid-state battery in which a PTC layer is arranged between an active material layer and a collector.

[0003] Prior Art Literature

[0004] Patent Document 1: Japanese Patent Application Publication No. 2017-130281

[0005] Patent Document 2: Japanese Patent Application Publication No. 2018-116810 Summary of the invention

[0006] Problems to be solved by the invention

[0007] In the prior art, it is required to suppress the heat generation of the battery.

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

[0009] Means for solving problems

[0010] A technical solution disclosed herein involves a battery comprising a first solid battery unit and a buffer layer, wherein the first solid battery unit comprises a positive electrode, a negative electrode, and a solid electrolyte layer located between the positive electrode and the negative electrode, wherein the positive electrode or the negative electrode has a current collector, and the buffer layer contacts the surface of the current collector opposite to the solid electrolyte layer, and the buffer layer comprises a PTC material, a resin, and a first metal, wherein the first metal is at least one selected from Sn, Cu, Al, Mg, and Zn.

[0011] Effects of the Invention

[0012] According to the present disclosure, it is possible to realize a highly reliable battery capable of suppressing heat generation of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0015] Figure 3It is a diagram showing a schematic structure of a battery according to Modification 2 of the embodiment.

[0016] Figure 4 It is a diagram showing a schematic structure of a battery according to Modification 3 of the embodiment.

[0017] Figure 5 It is a diagram showing a schematic structure of a particulate PTC material and a first metal layer in a buffer layer of a battery according to Modification 4 of the embodiment.

[0018] Figure 6 It is a diagram showing a schematic structure of a laminated battery according to Modification 5 of the embodiment. DETAILED DESCRIPTION

[0019] (Overview of the present disclosure)

[0020] A battery according to a technical solution of the present disclosure comprises a first solid battery cell and a buffer layer. The first solid battery cell comprises 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 opposite to the solid electrolyte layer. The buffer layer comprises a PTC material, a resin and a first metal. The first metal is at least one selected from Sn, Cu, Al, Mg and Zn.

[0021] For example, when using a semiconductor PTC material of the barium titanate (BaTiO3) type that is easily reduced in a battery, there is a problem of reduction degradation. Specifically, due to the reduction of the PTC material, there is a problem that the switching characteristics to the high resistance state of cutting off the current disappear. In addition, there is a problem that the high resistance loss caused by the non-ohmic contact between the PTC material and the collector deteriorates the battery characteristics.

[0022] In this regard, according to the battery involved in the above technical solution, the above problem can be solved by the buffer layer containing the PTC material, the resin and the first metal. Specifically, by the buffer layer containing the resin, a buffer layer softer than the battery component can be realized, so that the buffer layer and the collector can be joined with high reliability.

[0023] In addition, Sn, Cu, Al, Mg or Zn has a lower work function than the surface of the PTC material of the BaTiO3-based semiconductor. Therefore, the first metal can ensure low-resistance ohmic contact with the PTC material.

[0024] In addition, by making the PTC material and the first metal in ohmic contact with the PTC material coexist in the resin, the resistance loss can be reduced. In addition, the stress of impact and thermal cycle can be absorbed, and the PTC material can be protected from the influence of reducing atmosphere, etc. In this way, the battery can be given a PTC characteristic with high environmental resistance and low loss.

[0025] Therefore, when the battery is abnormally heated, the buffer layer is effectively made highly resistive, and the effect of cutting off the current can be obtained. That is, the buffer layer with PTC characteristics acts as a current cutting mechanism during heating. In addition, in the normal battery operating state where the PTC characteristic does not work, since there is no polarity caused by ohmic contact, the loss of battery characteristics accompanying charging and discharging is suppressed to a small extent. Therefore, a highly reliable and high-performance battery that can suppress fire or smoking combustion can be provided.

[0026] In addition, for example, the first metal may be at least one selected from Sn, Al, Mg, and Zn.

[0027] This can improve the electronic conductivity of the buffer layer, and thus can provide a battery with PTC characteristics with smaller resistance loss.

[0028] In addition, for example, the buffer layer may include a PTC layer and a conductive resin layer. The PTC layer may include the PTC material, and the conductive resin layer may include the resin and the first metal, and not include the PTC material. The conductive resin layer may cover the surface of the PTC layer opposite to the collector.

[0029] Thus, the conductive resin layer can protect one side of the PTC layer and ensure ohmic contact with the PTC layer, thereby suppressing resistance loss in battery characteristics and obtaining a battery with PTC characteristics that are strong against external stress and highly reliable.

[0030] In addition, for example, the conductive resin layer may also cover the surface of the PTC layer on the collector side.

[0031] Thus, the conductive resin layer can protect the PTC layer from both sides and ensure ohmic contact with the PTC layer and the current collector. Therefore, the resistance loss caused to the battery characteristics can be suppressed, and a battery with strong and reliable PTC characteristics such as resistance to external stress can be obtained.

[0032] In addition, for example, the buffer layer may include a metal layer covering the surface of the PTC layer on the collector side. The metal layer may include the first metal.

[0033] Thus, the metal layer can ensure ohmic contact with the PTC layer and the current collector, thereby suppressing resistance loss that affects battery characteristics.

[0034] In addition, for example, the buffer layer may include an alloy layer in contact with the current collector. The alloy layer may be composed of an alloy containing a second metal, and the second metal may be at least one selected from Sn, Ag, Cu, Bi, Al, and Zn.

[0035] Thus, the buffer layer can ensure low-resistance ohmic contact with the current collector and can be firmly connected to the current collector via the alloy layer.

[0036] In addition, for example, the second metal may be at least one selected from Sn, Bi, Al, and Zn.

[0037] Thus, the buffer layer can ensure low-resistance ohmic contact with the current collector and can be firmly connected to the current collector via the alloy layer.

[0038] In addition, for example, the PTC material may be particles, and the particles may be coated with the first metal.

[0039] Thus, the characteristics of all ohmic contact PTC particles can be brought out. Therefore, the loss of battery characteristics is suppressed to a smaller extent. In addition, since the environmentally fragile PTC material can be further protected, a highly reliable PTC characteristic can be achieved. Therefore, a high-performance battery that can suppress fire or smoking combustion can be provided.

[0040] In addition, for example, a battery according to one aspect of the present disclosure may further include a second solid battery cell. The first solid battery cell and the second solid battery cell may be stacked with the buffer layer interposed therebetween.

[0041] Therefore, even if the battery is multi-layered, its characteristics will not be deteriorated, and a highly reliable and high-performance stacked battery that can suppress combustion such as ignition or smoking can be provided.

[0042] In addition, for example, the solid electrolyte layer may include a solid electrolyte having lithium ion conductivity.

[0043] Hereinafter, the embodiments will be described in detail with reference to the drawings.

[0044] Furthermore, the embodiments described below are all general or specific examples. The numerical values, shapes, materials, components, configuration positions of components, and connection methods shown in the following embodiments are only examples, and their main purpose is not to limit the present disclosure. In addition, the components in the following embodiments that are not recorded in the independent claims are described as arbitrary components.

[0045] In addition, each figure does not necessarily illustrate strictly. In each figure, the same code|symbol is attached|subjected to the substantially same structure, and the repeated description is abbreviate|omitted or simplified.

[0046] 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 the thickness direction of the battery. In addition, in this specification, the "thickness direction" refers to the direction perpendicular to the surface on which each layer is stacked.

[0047] In this specification, “plan view” refers to a state where a 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.

[0048] In the present specification, “inside” and “outside” in “inside” and “outside” refer to the inside and outside when the battery is viewed along the stacking direction of the battery.

[0049] In addition, in this specification, the terms "upper" and "lower" in the structure of the battery do not refer to the upper direction (vertically above) and the lower direction (vertically below) in absolute spatial cognition, but are used as terms defined by relative positional relationships based on the stacking order in the stacking structure. In addition, the terms "upper" and "lower" are not only applicable to the case where two components are arranged at a distance from each other and there is another component between the two components, but also to the case where two components are arranged closely to each other and the two components are in contact.

[0050] (Implementation Method)

[0051] [Battery Overview]

[0052] First, the battery according to this embodiment will be described.

[0053] Figure 1 : is a diagram showing a general structure of a battery according to this embodiment. Specifically, Figure 1 (a) is a cross-sectional view of a battery 1 according to this embodiment, Figure 1 (b) is a plan view of the battery 1 as viewed from the positive side in the z-axis direction. Figure 1 (a) shows Figure 1 (b) A cross section at the position indicated by line II. Figure 1 (c) Figure 1 (a) is a cross-sectional view schematically enlarging a part of the cross-sectional shape.

[0054] like Figure 1 As shown, the battery 1 includes a solid battery cell 2 and a buffer layer 40. The battery 1 is an all-solid battery.

[0055] The solid battery cell 2 is an example of a first solid battery cell, and includes a first electrode 10, a second electrode 20, and a solid electrolyte layer 30. The first electrode 10 includes 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 includes 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 opposite side to the solid electrolyte layer 30. The buffer layer 40 includes a PTC material 41, a first metal 42, and a resin 43.

[0056] like Figure 1 As 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 for the entire surface of the first current collector 11 on the buffer layer 40 side to be in contact with the buffer layer 40 .

[0057] [Solid-state battery cell]

[0058] Hereinafter, each component of the solid battery cell 2 will be described in detail.

[0059] 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 a plan view. The shapes 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 a plan view are not particularly limited, and may be shapes other than rectangles such as circles, ellipses, or polygons.

[0060] In this embodiment, the first electrode 10 is a positive electrode, and the second electrode 20 is a negative electrode. That is, the first current collector 11 is a positive electrode current collector, and the first active material layer 12 is a positive electrode active material layer. The second current collector 21 is a negative electrode current collector, and the second active material layer 22 is a negative electrode active material layer. The buffer layer 40 is connected to the positive electrode current collector.

[0061] Furthermore, the first electrode 10 may be a negative electrode and the second electrode 20 may be a positive electrode. In other words, the first current collector 11 may be a negative electrode current collector and the first active material layer 12 may be a negative electrode active material layer. The second current collector 21 may be a positive electrode current collector and the second active material layer 22 may be a positive electrode active material layer. The buffer layer 40 may be connected to the negative electrode current collector.

[0062] In this specification, the first current collector 11 and the second current collector 21 may be collectively referred to as a “current collector.” The current collector is not particularly limited as long as it is made of a conductive material.

[0063] As the current collector, for example, a foil, plate or mesh 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 can be used. The material of the current collector can be appropriately selected considering the manufacturing process, the use temperature and the use pressure without melting and decomposition, 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 cladding material laminated with heterogeneous metal foils.

[0064] The thickness of the collector is, for example, in the range of 10 μm to 100 μm. Furthermore, from the viewpoint of making the surface of the collector firmly adhere to the first active material layer 12, the second active material layer 22 and the buffer layer 40, a collector whose surface is processed into a rough surface with uneven surfaces can be used. In addition, an adhesive component such as an organic adhesive can also be applied to the surface of the collector. As a result, the adhesion of the interface between the collector and other layers is enhanced, which can improve the reliability of the PTC characteristics not only from the mechanical and thermal reliability and cycle characteristics of the battery, but also from the adhesion with the buffer layer 40.

[0065] The first active material layer 12 is configured to contact 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 positive electrode materials such as positive electrode active materials. The positive electrode active material is a substance that inserts or detaches metal ions such as lithium (Li) ions or magnesium (Mg) ions in the crystal structure at a higher potential than the negative electrode, and is subsequently oxidized or reduced. The type of positive electrode active material can be appropriately selected according to the type of battery, and a known positive electrode active material can be used.

[0066] Examples of positive electrode active materials include compounds containing lithium and transition metal elements, such as oxides containing lithium and transition metal elements, and phosphate compounds containing lithium and transition metal elements. Examples of oxides containing lithium and transition metal elements include LiNi x M 1-xLithium nickel composite oxides such as lithium nickel oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), or lithium manganese oxide with a spinel structure (e.g., LiMn2O4, Li2MnO3, LiMnO2) can be used. As a phosphate compound containing lithium and a transition metal element, for example, lithium iron phosphate (LiFePO4) with an olivine structure can be used. In addition, as a positive electrode active material, sulfides such as sulfur (S) and lithium sulfide (Li2S) can also be used. In this case, a material coated with or added with lithium niobate (LiNbO3) or the like can be used as a positive electrode active material. Furthermore, as a positive electrode active material, only one of these materials can be used, or two or more of these materials can be used in combination.

[0067] As described above, the first active material layer 12 that becomes the positive electrode active material layer may contain at least the positive electrode active material. The positive electrode active material layer may be a mixture layer composed of a mixture of the positive electrode active material and other additives. As other additives, for example, solid electrolytes such as inorganic solid electrolytes or sulfide solid electrolytes, conductive aids such as acetylene black, and bonding agents such as polyethylene oxide or polyvinylidene fluoride may be used. The positive electrode active material layer can improve the lithium ion conductivity in the positive electrode active material layer and can improve the electronic conductivity by mixing the positive electrode active material with other additives such as the solid electrolyte in a predetermined ratio.

[0068] Note that the thickness of the first active material layer 12 is, for example, not less than 5 μm and not more than 300 μm, but is not limited thereto.

[0069] The second active material layer 22 is configured to contact 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 negative electrode materials such as negative electrode active materials. The negative electrode active material is a substance that inserts or detaches metal ions such as lithium (Li) ions or magnesium (Mg) ions in the crystal structure at a lower potential than the positive electrode, and is subsequently oxidized or reduced. 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.

[0070] As the negative electrode active material, for example, carbon materials such as natural graphite, artificial graphite, graphite carbon fiber or resin sintered carbon, and alloy materials mixed with solid electrolytes can be used. As alloy materials, for example, LiAl, LiZn, Li3Bi, Li3Cd, Li3Sb, Li4Si, Li4.4 Pb、Li 4.4 Sn、Li 0.17 C or LiC6 and other lithium alloys, lithium titanate (Li4Ti5O 12 ) and other lithium and transition metal oxides, zinc oxide (ZnO) or silicon oxide (SiO x ) and other metal oxides. As 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.

[0071] As described above, the second active material layer 22 that becomes the negative electrode active material layer may contain at least the negative electrode active material. The negative electrode active material layer may be a mixture layer composed of a mixture of the negative electrode active material and other additives. As other additives, for example, solid electrolytes such as inorganic solid electrolytes or sulfide solid electrolytes, conductive aids such as acetylene black, and bonding agents such as polyethylene oxide or polyvinylidene fluoride may be used. The negative electrode active material layer can improve the lithium ion conductivity in the negative electrode active material layer and improve the electronic conductivity by mixing the negative electrode active material and other additives such as the solid electrolyte in a predetermined ratio.

[0072] Note that the thickness of the second active material layer 22 is, for example, not less than 5 μm and not more than 300 μm, but is not limited thereto.

[0073] 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 includes at least a solid electrolyte. For example, the solid electrolyte layer 30 includes a solid electrolyte as a main component.

[0074] The solid electrolyte can be any known solid electrolyte for batteries as long as it has ionic conductivity. As a 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 a sulfide solid electrolyte, 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 an oxide solid electrolyte, for example, lithium-containing metal oxides such as Li2O-SiO2 or Li2O-SiO2-P2O5, Li x P y O 1-z N zLithium-containing metal nitrides, lithium phosphate (Li3PO4) and lithium-containing transition metal oxides such as lithium titanium oxide. As a solid electrolyte, only one of these materials can be used, or two or more of these materials can be used in combination. In this embodiment, as an example, the solid electrolyte layer 30 includes a solid electrolyte having lithium ion conductivity.

[0075] Furthermore, the solid electrolyte layer 30 may contain a bonding agent such as polyethylene oxide or polyvinylidene fluoride in addition to the above-mentioned solid electrolyte material.

[0076] In addition, the thickness of the solid electrolyte layer 30 is, for example, not less than 5 μm and not more than 150 μm, but is not limited thereto.

[0077] Furthermore, the material of the solid electrolyte may be constituted as an aggregate of particles. Alternatively, the material of the solid electrolyte may be constituted as a sintered structure.

[0078] [Buffer layer]

[0079] Next, the specific structure of the buffer layer 40 will be described.

[0080] The buffer layer 40 is a conductive layer and is used to electrically connect the solid battery cell 2 to other solid battery cells or other components. In addition, the buffer layer 40 also plays a role in alleviating impact on the solid battery cell 2.

[0081] In the present embodiment, the buffer layer 40 contains an electronically conductive PTC material 41 having a PTC characteristic (positive temperature coefficient of resistance), a first metal 42, and a resin 43. The PTC material 41 is, for example, a BaTiO3-based semiconductor material. The first metal 42 is a metal with a low work function. For example, the first metal 42 is at least one selected from Sn (tin), Cu (copper), Al (aluminum), Mg (magnesium), and Zn (zinc), or an alloy thereof. The resin 43 is, for example, a thermosetting resin such as an epoxy resin. Furthermore, the resin 43 can be either an insulating resin or a conductive resin. The conductive resin contains, for example, a thermosetting resin such as an epoxy resin and conductive particles such as Ag. Alternatively, the conductive resin can be a resin containing conductive fillers such as metal particles in an insulating resin, or a conductive polymer that does not contain conductive fillers.

[0082] The first metal 42 and the PTC material 41 are crushed into particles and contained in the resin 43. As for the respective content ratios, it is sufficient as long as the PTC material 41 and the first metal 42 are contained so that the PTC characteristics can be obtained in the resistance-temperature characteristics of the buffer layer 40. For example, it is preferred that the first metal 42 is contained in a manner such that the temperature characteristics of the resistance value of the buffer layer 40 show the PTC characteristics, and then show a value of the room temperature resistance level corresponding to the content of the PTC material 41. By adopting such a structure, it is possible to obtain a connection in a state of ohmic contact between the buffer layer 40 and the collector, and between the interface of the PTC material 41 and the first metal 42. That is, there is no non-ohmic contact between the buffer layer 40 and the collector, and between the PTC material 41 and the first metal 42. Therefore, the PTC characteristics can be added to the battery with low loss. Assuming that there is a non-ohmic contact, the resistance loss will be added to the battery characteristics due to the addition of interface resistance.

[0083] Furthermore, for example, the resin 43 may contain 30% to 80% by volume of the PTC material 41 and 5% to 40% by volume of the first metal 42. The volume % here is a ratio relative to the volume of the entire buffer layer 40. The content ratio can be appropriately adjusted according to the dispersibility and resistance characteristics when included in the resin 43. Furthermore, the resistance of the buffer layer 40 can be measured by a 4-terminal method or a 4-terminal needle method, for example, using a measuring instrument such as the Loresta Series manufactured by Mitsubishi Analytical Science. For example, the thickness of the buffer layer 40 is greater than 5 μm and less than 300 μm, but is not limited to this.

[0084] Furthermore, as the electrical properties of the buffer layer 40, it is expected to have electronic conductivity with PTC characteristics and ohmic contact with the collector. The ohmic contact between the collector and the buffer layer 40 can be evaluated by the presence or absence of polarity from the bidirectional evaluation of voltage-current characteristics under direct current. In addition, the ohmic contact between the powder of the PTC material 41 and the first metal 42 can also be directly confirmed by the presence or absence of polarity in the evaluation of fine structures such as nanofibers. Furthermore, the resistance value that does not have polarity caused by the measurement direction is of course in ohmic contact.

[0085] In addition, the PTC material 41 is, for example, a particle obtained by crushing a BaTiO3 semiconductor ceramic. Specifically, as the PTC material 41, an N-type semiconductor having a donor formed on BaTiO3 is used. The donor is formed by replacing a small portion of the Ba site with a trivalent rare earth element such as yttrium (Y), or by containing a pentavalent element such as niobium (Nb) and partially replacing the Ti site. The particle size of BaTiO3 is, for example, in the range of 0.2 μm or more and 10 μm or less.

[0086] In order to improve the PTC characteristics, a small amount of transition elements such as manganese (Mn) or cobalt (Co) can be contained in the PTC material 41. In this way, the jump amplitude of the resistance value during heating can be increased, so that the switching performance of the PTC material 41 can be made clear. For example, the resistance value when the PTC characteristics appear increases by about 5 to 8 orders of magnitude. In this way, the current can be effectively cut off and the operation of the battery can be stopped.

[0087] In addition, the switching temperature can be raised from 120°C without substitution by replacing Ba sites with lead (Pb) having a larger ion radius than Ba ​​ions. Alternatively, the switching temperature can be lowered by replacing Ba sites with strontium (Sr) having a smaller ion radius than Ba ​​ions. Furthermore, the switching temperature refers to the temperature at which the resistance value of the PTC material 41 increases. For example, the switching temperature can be adjusted in the range of about 70°C to 250°C. It can be arbitrarily controlled so that the suppression temperature of heat generation reaches the desired level. In addition, the switching temperature can also be lowered by replacing Ti sites with Sn. In addition, for example, by reducing the size of crystal particles, the withstand voltage and current characteristics can be improved. In addition, by making Ba excessive in the ratio of Ba to Ti, or using a trivalent element as a semiconductor element, the reduction resistance can be improved. Ba excess refers to a range of, for example, +0.05% to +5.0% relative to Ti. As a result, the reliability of battery operation and the reliability of PTC characteristics relative to the outside air can be further improved.

[0088] In addition, the first metal 42 can be any metal that is in ohmic contact with the PTC material 41. As a result, the first metal 42 is also in ohmic contact with the collector. The first metal 42 is, for example, at least one selected from Sn, Cu, Al, Mg and Zn. Alternatively, the first metal 42 can be at least one selected from Sn, Al, Mg and Zn other than Cu, which is a metal element contained in a general conductive resin. In the case of using a BaTiO3-based PTC material 41, if a metal with a smaller work function than Ag with a work function of about 4.5eV to 4.7eV is used as the first metal 42, it is easy to form an ohmic contact. Furthermore, as the first metal 42, a powder can be used. There is no particular limitation on the particle size and shape of the first metal 42, as long as it is in ohmic contact with the PTC material 41 and the collector within a range that does not short-circuit the buffer layer 40. In addition, the first metal 42 can be mixed with metal particles having a work function lower than that of Ag and particles with high conductivity such as Ag, Ni, Pd or Pt. In addition, from the viewpoint of manufacturing process such as easy dispersion, the type of the first metal 42 can be appropriately adjusted within the range where PTC characteristics can be obtained. The particle size of the first metal 42 is, for example, in the range of 0.1 μm to 10 μm. The particle shape of the first metal 42 is spherical or flat.

[0089] In addition, the buffer layer 40 contains resin 43, which is softer than battery components such as collectors, and is easy to form a connection state with a low Young's modulus. Therefore, the stress generated at the interface between the buffer layer 40 and the collector is absorbed, so that the durability of the connection interface to mechanical and thermal shocks and charge and discharge cycles is improved. In addition, by making the PTC material 41 exist in the resin 43, the PTC material 41 with weak environmental resistance can be protected.

[0090] In addition, as the resin 43 used in the buffer layer 40, from the viewpoint of environmental resistance such as the reducibility of the PTC material 41 of the BaTiO3 system, a resin material with high sealing performance of gas and moisture can be used. For example, no communicating pores are provided in the resin 43. In addition, the resin 43 can be either a thermoplastic resin or a thermosetting resin. As the thermoplastic resin, for example, 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-ethylene copolymer (SBS), styrene-ethylene-butadiene-ethylene copolymer (SEBS), ethylene-propylene rubber, butyl rubber, chloroprene rubber and acrylonitrile-butadiene rubber etc. can be cited. Examples of thermosetting resins include (i) amino resins such as urea resins, melamine resins, and guanamine resins, (ii) epoxy resins such as bisphenol A type, bisphenol F type, phenol novolac type, and alicyclic type, (iii) oxetane resins, (iv) phenolic resins such as resol type and novolac type, and (v) silicone-modified organic resins such as silicone epoxy resins and silicone polyesters.

[0091] In addition, for example, the Young's modulus of the resin 43 as the buffer layer 40 is expected to be lower than the Young's modulus of the collector from the perspective of the function of the buffer layer 40. In addition, the Young's modulus of the resin 43 is lower than the Young's modulus of the PTC material 41 and the first metal 42, for example. As a result, the stress at the interface between the solid battery cell 2 and the buffer layer 40 caused by temperature changes or external stress is alleviated, and the stress around the PTC material 41 and the first metal 42 in the buffer layer 40 is absorbed. As a result, the generation of gaps connected to the outside and the generation of poor connection resistance can be suppressed. In addition, since the buffer layer 40 deforms in the process of stacking and pressing to follow the surface of the collector and the PTC material 41 and the first metal 42, the bonding is improved. Through these effects, the PTC characteristics can be obtained with high reliability.

[0092] In addition, from the viewpoint of alleviating the stress between the solid battery cell 2 and the buffer layer 40 caused by the expansion or contraction of the first active material layer 12 and the second active material layer 22 due to temperature changes or charge and discharge, and improving the reliability of the battery 1 with PTC, the buffer layer 40 may be made of a material having a smaller Young's modulus than the solid electrolyte layer 30, the first active material layer 12, and the second active material layer 22. The relative relationship between their Young's moduli can be compared based on the displacement characteristics relative to the pressure when the probe is pressed or the size of the depression.

[0093] In addition, considering the difficulty of manufacturing process and stress relaxation performance, heat shock resistance and resistance to cold and hot cycles, the buffer layer 40 can be used by adjusting the type, shape and combination of each material. In addition, pores can be appropriately formed in the buffer layer 40 in a manner that does not penetrate the buffer layer 40 to adjust the Young's modulus of the buffer layer 40. In order not to expose the PTC material 41 to the reducing atmosphere, it is preferred that there are no connected pores that cross the upper and lower parts of the buffer layer 40. Furthermore, the state of the pores can be confirmed by conventional cross-sectional observation methods such as optical microscopy or electron microscopy. In addition, it can also be analyzed in any cross section by means such as CT scanning (Computed Tomography). In addition, as a strict evaluation of air permeability, the tissue can also be taken out and confirmed by generally used methods such as ceramic packaging using nitrogen or helium leak testers. Through such an organizational structure, the environmental resistance of the PTC characteristics in the buffer layer 40 can be improved.

[0094] In addition, in the buffer layer 40, the resin 43 may contain a material containing particles of a conductive material or particles of a semiconductor material in a solid electrolyte. As a result, the expansion and contraction characteristics of the buffer layer 40 and the solid battery cell 2 become closer. Therefore, the stress generated between the buffer layer 40 and the collector during temperature changes or charging and discharging is relaxed, and a battery 1 with highly reliable PTC characteristics can be realized.

[0095] In addition, the buffer layer 40 may not be formed on the entire surface of the collector, but may be partially formed by forming a pattern on the surface of the collector in contact. In other words, the buffer layer 40 only needs to be connected in series with the collector. In addition, the buffer layer 40 may also be composed of multiple layers of different materials, for example, multiple layers with different composition ratios of the PTC material 41 and the first metal 42.

[0096] 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, within the range that can ensure the reliability of the voltage resistance characteristics of the PTC, the thickness of the buffer layer 40 can be thinner. 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, the reduction in volume energy density can be suppressed, and the stress caused by the expansion or contraction of the collector due to temperature changes can be easily alleviated.

[0097] In addition, the specific gravity of the buffer layer 40 is not particularly limited, but is preferably smaller from the perspective of gravimetric energy density. For example, the specific gravity of the buffer layer 40 may be smaller than the specific gravity of the current collector made of a metal material. This can reduce the impact on gravimetric energy density.

[0098] [Effects, etc.]

[0099] Comparing the structure of the battery 1 according to the present embodiment with the structures of the batteries described in Patent Documents 1 and 2, there are the following differences.

[0100] First, Patent Document 1 discloses a fully solid battery using a resin having PTC characteristics as a current collector. However, in the battery disclosed in Patent Document 1, the PTC layer is formed using a carbon conductive agent such as acetylene black and a heat-expandable resin, which is different from the material constituting the buffer layer 40 disclosed in this embodiment. Therefore, the resistance of the PTC material disclosed in Patent Document 1 becomes high, thereby deteriorating the charge and discharge characteristics of the battery. In addition, in the battery disclosed in Patent Document 1, there are also problems in repeated use after expansion.

[0101] In contrast, according to the battery 1 of the present embodiment, the buffer layer 40 contains the first metal 42, so that ohmic contact is made with the current collector and the PTC material 41. Therefore, it is possible to reduce the resistance of the buffer layer 40. In addition, in the battery 1, the resin 43 of the buffer layer 40 is not a heat-expandable resin, so expansion due to heat generation does not occur itself.

[0102] In addition, in Patent Document 1, a PTC layer is arranged on the surface of the active material. That is, the active material layer is in contact with the PTC layer, so the PTC layer is directly affected by the redox reaction on the surface. Therefore, there is a big problem in terms of the stability of the battery operation.

[0103] In addition, Patent Document 2 discloses a fully solid battery in which a PTC layer is arranged between the active material layer and the current collector. The PTC layer is arranged between the active material layer and the current collector using a heat-expandable resin as a substrate, similarly to Patent Document 1. Therefore, the battery described in Patent Document 2 also increases the resistance loss of the battery similarly to Patent Document 1, and has problems in terms of the stability of the battery operation.

[0104] In contrast, according to the battery 1 involved in this embodiment, the buffer layer 40 containing the PTC material 41 is arranged on the side of the collector opposite to the surface on which the active material layer is arranged. Therefore, it is possible to avoid contact between the PTC material and the active material layer, and suppress the reduction of the PTC material. Furthermore, in Patent Documents 1 and 2, there is no disclosure or revelation about the battery described in this embodiment in which the buffer layer 40 formed by containing the PTC material 41 and the first metal 42 in the resin 43 is arranged on the surface on the opposite side of the active material layer of the collector.

[0105] As described above, according to the battery 1 of this embodiment, it is possible to suppress ignition and smoking combustion of the battery due to heat generation or overcurrent, that is, it is possible to realize a highly reliable and high-performance battery 1.

[0106] [Modification 1]

[0107] Hereinafter, Modification 1 of the embodiment will be described. In the following description of Modification 1, the differences from the embodiment will be mainly described, and the description of the common points will be omitted or simplified.

[0108] Figure 2 1 is a diagram showing a schematic structure of a battery according to a first modification of the embodiment. Specifically, Figure 2 (a) is a cross-sectional view of a battery 100 according to Modification 1. Figure 2 (b) is a plan view of the battery 100 as viewed from the positive side in the z-axis direction. Figure 2 (a) shows Figure 2 (b) A cross section at the position indicated by line II-II. Figure 2 (c) Figure 2 (a) is a cross-sectional view schematically enlarging a part of the cross-sectional shape.

[0109] like Figure 2 As shown, the battery 100 involved in the modification example 1 of the embodiment is different from the battery 1 involved in the embodiment in that it includes a buffer layer 140 instead of the buffer layer 40. The buffer layer 140 includes an alloy layer 144 in contact with the current collector. The alloy layer 144 mainly contains the second metal 142. The alloy layer 144 is a layer in which the second metal 142 with a low melting point is diffused into the current collector, so that the current collector and the buffer layer 140 are firmly bonded. For example, the formation of the alloy layer 144 can be made by curing a PTC layer containing the second metal 142 as a low melting point metal in a thermosetting resin, and diffusing the second metal 142 from the resin 43 to the current collector.

[0110] As the second metal 142, metal particles with a low melting point can be used. For example, the second metal 142 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 second metal 142 may be at least one selected from Sn, Al, Mg, and Zn in addition to Ag and Cu, which are metal elements contained in a general conductive resin.

[0111] The metal with a low melting point is, for example, a metal with a melting point of 300°C or less. Specifically, 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 can be used. For example, in the case where the current collector is Cu, if Sn is used as the second metal 142 and heat-treated, an alloy layer 144 can be formed at its interface by diffusion of the tin-copper alloy. In the case of using a low melting point metal, it is possible to combine even at a temperature of about half the melting point to obtain a strong bonding interface.

[0112] The content ratio of the second metal 142 is, for example, 1 volume % to 10 volume % relative to the buffer layer 140. The components and content are adjusted from the viewpoint of the thickness and bonding strength of the alloy layer 144. The thickness of the alloy layer 144 can be appropriately adjusted by the heat treatment temperature.

[0113] Furthermore, the first metal 42 is a metal that can make ohmic contact with the PTC material 41, so an appropriate metal is selected according to the type of the PTC material 41. The second metal 142 is a metal that can form an alloy with the metal contained in the collector, so an appropriate metal is selected according to the type of the collector. As a result, the first metal 42 and the second metal 142 can be the same metal. Alternatively, the first metal 42 and the second metal 142 can also be different types of metals.

[0114] As described above, according to the battery 100 according to Modification 1, the current collector and the buffer layer 140 can be firmly bonded to each other. Therefore, the battery 100 having a more reliable PTC characteristic in terms of shock resistance, thermal cycling, and charge and discharge cycling can be realized.

[0115] [Modification 2]

[0116] Hereinafter, Modification 2 of the embodiment will be described. In the following description of Modification 2, the differences from the embodiment will be mainly described, and the description of the common points will be omitted or simplified.

[0117] Figure 3 : is a diagram showing a schematic structure of a battery according to a second modification of the embodiment. Specifically, Figure 3 (a) is a cross-sectional view of a battery 200 according to Modification 2. Figure 3 (b) is a plan view of the battery 200 as viewed from the positive side in the z-axis direction. Figure 3 (a) shows Figure 3 (b) A cross section at the position indicated by line III-III. Figure 3 (c) Figure 3 (a) is a cross-sectional view schematically enlarging a part of the cross-sectional shape.

[0118] like Figure 3 As shown, the battery 200 according to the second modification of the embodiment is different from the battery 1 according to the embodiment in that a buffer layer 240 is provided instead of the buffer layer 40. The buffer layer 240 has a three-layer structure including a PTC layer 241 and two conductive resin layers 242 and 243 provided so as to sandwich the PTC layer 241 from both sides.

[0119] The PTC layer 241 includes the above-mentioned PTC material. For example, the PTC layer 241 is a layer composed of the PTC material 41 formed into a plate shape. Alternatively, the PTC layer 241 may be a layer formed of the particulate PTC material 41 using a bonding agent or the like.

[0120] The conductive resin layers 242 and 243 respectively contain the first metal 42 and the resin 43. The conductive resin layer 242 covers the surface of the PTC layer 241 opposite to the current collector.

[0121] The conductive resin layer 243 covers the collector-side surface of the PTC layer 241. The conductive resin layer 243 is disposed between the collector and the PTC layer 241 and is in contact with each. That is, the PTC layer 241 is electrically connected to the collector via the conductive resin layer 243 containing the first metal 42. Thus, ohmic contact with the PTC layer 241 can be ensured, and the high resistance of the buffer layer 240 can be suppressed. With such a three-layer structure, the PTC layer 241 can be protected, and ohmic contact can be achieved on both sides of the PTC layer 241.

[0122] Furthermore, the thickness of the three layers can be appropriately adjusted from the perspective of the manufacturing method and the characteristics. In addition, the alloy layer 144 shown in the modification 1 can be formed between the conductive resin layer 243 and the collector. In addition, as long as the conductive resin layers 242 and 243 contain the first metal 42 so as to be able to make ohmic contact with the PTC layer 241, they can contain Ag particles or other conductor metals with electronic conductivity. In addition, in order to effectively obtain the PTC characteristics, as long as the PTC characteristics can be drawn out mainly through the first metal 42 on the PTC layer 241, it is not limited to this modification.

[0123] As described above, according to the battery 200 according to the second modification, it is possible to suppress the battery from catching fire or emitting smoke due to heat or overcurrent. In other words, it is possible to realize a highly reliable and high-performance battery 200.

[0124] [Variation 3]

[0125] Hereinafter, Modification 3 of the embodiment will be described. In the following description of Modification 3, the differences from the embodiment or Modification 2 will be mainly described, and the description of the common points will be omitted or simplified.

[0126] Figure 4 : is a diagram showing a schematic structure of a battery according to a third variation of the embodiment. Specifically, Figure 4 (a) is a cross-sectional view of a battery 300 according to Modification 2. Figure 4 (b) is a plan view of the battery 300 as viewed from the positive side in the z-axis direction. Figure 4 (a) shows Figure 4 (b) A cross section at the position indicated by line IV-IV. Figure 4 (c) Figure 4 (a) is a cross-sectional view schematically enlarging a part of the cross-sectional shape.

[0127] like Figure 4 As shown, the battery 300 according to the modification 3 of the embodiment includes a buffer layer 340 instead of the buffer layer 240 , as compared with the battery 200 according to the modification 2. The buffer layer 340 includes a metal layer 343 instead of the conductive resin layer 243 .

[0128] The metal layer 343 includes the first metal described above. For example, the metal layer 343 is a layer composed of the first metal 42 formed into a plate shape. The metal layer 343 does not contain the resin 43.

[0129] In this structure, the PTC layer 241 is electrically connected to the current collector via the metal layer 343. This ensures ohmic contact with the PTC layer 241 and suppresses the buffer layer 340 from becoming more resistant.

[0130] The thickness of the metal layer 343 can be appropriately adjusted from the viewpoint of the manufacturing method and characteristics. In addition, the alloy layer 144 shown in Modification 1 may be formed between the metal layer 343 and the current collector.

[0131] As described above, according to the battery 300 according to the third modification, it is possible to suppress the ignition and smoking of the battery due to heat generation or overcurrent. That is, it is possible to realize a highly reliable and high-performance battery 300.

[0132] [Variation 4]

[0133] Hereinafter, Modification 4 of the embodiment will be described. In the following description of Modification 4, the differences from the embodiment will be mainly described, and the description of the common points will be omitted or simplified.

[0134] Figure 5 FIG. 4 is a diagram showing a schematic structure of a particulate PTC material and a first metal in a buffer layer of a battery according to Modification 4. Figure 5 As shown, the surface of the granular PTC material 41 is covered by the first metal layer 442. In the embodiment, the granular PTC material 41 and the granular first metal 42 are mixed and dispersed, but in the modification 4, the granular PTC material 41 is coated with the first metal layer 442. Furthermore, the origin of the PTC characteristics of the BaTiO3 semiconductor is at the interface of the crystal particles. Therefore, the granular PTC material 41 is preferably a polycrystalline particle with a directly bonded grain boundary.

[0135] Through such a structure, the connection between the particle-shaped PTC material 41 and the first metal layer 442 becomes a surface connection. Therefore, compared with the point contact between powders, the conductive area of ​​the connection interface is significantly increased. Therefore, it is possible to further reduce the resistance loss while bringing out the characteristics of the PTC material 41, and improve the protection performance of the PTC material 41. As a result, a battery with higher reliability and high performance PTC characteristics can be realized.

[0136] The coating of the first metal layer 442 can be formed by powder coating such as a mechanical particle composite process or electroless plating of the particle-shaped PTC material 41. The coating thickness of the first metal layer 442 is, for example, 1 μm or less.

[0137] As described above, according to the battery according to Modification 4, it is possible to suppress ignition and smoking combustion of the battery due to heat generation or overcurrent. In other words, it is possible to realize a highly reliable and high-performance battery.

[0138] The PTC material 41 covered with the first metal layer 442 according to Modification 4 may be contained in the resin 43 as the PTC material 41 of each of the embodiment and Modifications 1 to 3. In this case, the resin 43 may not contain the first metal 42 in the form of particles.

[0139] [Variation 5]

[0140] Hereinafter, Modification 5 of the embodiment will be described. In the following description of Modification 5, the differences from the embodiment will be mainly described, and the description of the common points will be omitted or simplified.

[0141] Figure 6 : is a diagram showing a schematic structure of a battery according to a fifth modification of the embodiment. Specifically, Figure 6 (a) is a cross-sectional view of a stacked battery 500 according to Modification 5. Figure 6 (b) is a plan view of the stacked battery 500 as viewed from the positive side in the z-axis direction. Figure 6 (a) shows Figure 6 (b) A cross section at the position indicated by line VI-VI.

[0142] like Figure 6 As shown, a stacked battery 500 according to Modification 5 is different from the battery 1 according to the embodiment in that two solid battery cells 2 are stacked and connected via a buffer layer 40 .

[0143] The two solid battery cells 2 are examples of a first solid battery cell and a second solid battery cell, respectively. The two solid battery cells 2 are stacked with the buffer layer 40 interposed therebetween and are electrically connected in series.

[0144] exist Figure 6 In the example shown, the positive electrode collectors of the two solid battery cells 2 are connected to each other. Furthermore, as described in the embodiment, the first collector 11 may also be a negative electrode collector. That is, the stacked battery 500 may also include two solid battery cells 2 whose negative electrode collectors are connected to each other. The number of stacked solid battery cells 2 may also be 3 or more.

[0145] According to this structure, when a short circuit or abnormal heating occurs in one solid battery cell 2, the current is cut off by the PTC characteristics of the buffer layer 40. The buffer layer 40 can ohmically connect the solid battery cells 2 to each other by using the PTC characteristics, so that a series stacked battery with low-loss PTC characteristics can be formed.

[0146] As described above, according to the laminated battery 500 according to Modification 5, it is possible to suppress the battery from catching fire or emitting smoke due to heat or overcurrent. In other words, a highly reliable and large-capacity battery can be realized.

[0147] [Battery manufacturing method]

[0148] Next, an example of a method for manufacturing a battery according to the present embodiment will be described. Hereinafter, a method for manufacturing the battery 1 according to the above-mentioned embodiment will be described. First, each paste 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 is prepared. As a solid electrolyte raw material used in the respective mixtures of the positive electrode active material layer and the negative electrode active material layer, for example, a glass powder of Li2S-P2S5-based sulfide having an average particle size of about 10 μm and containing triclinic crystals as the main component is prepared. As the glass powder, for example, a powder having a particle size of 2×10 -3 S / cm~3×10 -3As the positive electrode active material, for example, a layered LiNiCoAl composite oxide (specifically, LiNi 0.8 Co 0.15 Al 0.05 O2) powder. A paste for positive electrode active material layer is prepared by dispersing a mixture containing the above-mentioned positive electrode active material and the above-mentioned glass powder in an organic solvent or the like. In addition, as the negative electrode active material, for example, a powder of natural graphite having an average particle size of about 10 μm can be used. Similarly, a paste for negative electrode active material layer is prepared by dispersing a mixture containing the above-mentioned negative electrode active material and the above-mentioned glass powder in an organic solvent or the like.

[0149] Next, as a 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), a copper foil of, for example, about 30 μm thick is prepared. Using a screen printing method, a paste for a positive electrode active material layer and a paste for a negative electrode active material layer are printed on the surface of one side of each copper foil in a predetermined shape and a thickness of about 50 μm to 100 μm, respectively. The paste for the positive electrode active material layer and the paste for the negative electrode active material layer are dried in the range of 80°C to 130°C to a thickness of about 30 μm to 60 μm. Thus, a current collector (copper foil) having a positive electrode active material layer and a negative electrode active material layer, that is, a first electrode 10 (hereinafter referred to as a positive electrode) and a second electrode 20 (hereinafter referred to as a negative electrode), are obtained.

[0150] Next, a solid electrolyte layer paste is prepared by dispersing the mixture containing the above-mentioned glass powder in an organic solvent or the like. The solid electrolyte layer paste is printed on the surface of the active material layer of each of the positive electrode and the negative electrode using a metal mask, for example, with a thickness of about 100 μm. Then, the positive electrode and the negative electrode printed with the solid electrolyte layer paste are dried at a temperature in the range of 80°C to 130°C.

[0151] 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 stacked so as to contact and face each other.

[0152] Next, a 5×10 6 The thickness of the elastic sheet is, for example, 70 μm. Then, the press mold plate is heated to 50° C. under a pressure of 300 MPa and pressurized for 90 seconds.

[0153] Through the above steps, the solid battery cell 2 is manufactured.

[0154] Next, a granular PTC material 41 (specifically, a BaTiO3-based semiconductor) having an average particle size of about 1 μm and a powder of a first metal 42 having an average particle size of 0.5 μm are added to a thermosetting conductive resin paste containing silver particles having an average particle size of 0.5 μm, and the powders are dispersed using three rollers to prepare a resin paste containing the PTC material 41 and the first metal 42 (i.e., a resin paste for the buffer layer 40). Next, the resin paste for the buffer layer 40 is printed on the surface of the collector of the prepared solid battery cell 2 using a metal mask. Next, a heat curing treatment is performed using a dryer, for example, at 120°C for 1 hour, and the mixture is cooled to room temperature, thereby forming a buffer layer 40 from the resin paste for the buffer layer 40.

[0155] Through the above steps, the battery 1 is manufactured. Note that the method and sequence for forming the battery 1 are not limited to the above example.

[0156] Furthermore, in the above-mentioned manufacturing method, an example of applying the positive electrode active material layer paste, the negative electrode active material layer paste, the solid electrolyte layer paste, and the resin paste for the buffer layer 40 by printing is shown, but it is not limited to this. As a printing method, for example, a doctor blade method, a calendar method, a spin coating method, a dip coating method, an inkjet method, an offset printing method, a die coating method, a spray coating method, etc. can also be used.

[0157] In the above-mentioned manufacturing method, as the resin paste for the buffer layer 40, a thermosetting conductive resin paste containing silver metal particles is exemplified, but not limited to this. As the conductive resin paste, for example, a thermosetting conductive resin paste containing high-conductive metal particles with a high melting point of more than 400°C, or a thermosetting conductive resin paste containing metal particles with a low melting point below the curing temperature of the conductive resin paste, for example, 300°C and a resin can be used. As materials of high-conductive metal particles with a high melting point, for example, silver, copper, nickel, zinc, aluminum, palladium, gold, platinum, or alloys of these metals can be cited. As materials of low-melting metal particles with a melting point of less than 300°C, for example, tin, tin-zinc alloys, tin-silver alloys, tin-copper alloys, tin-aluminum alloys, tin-lead alloys, indium, indium-silver alloys, indium-zinc alloys, indium-tin alloys, bismuth, bismuth-silver alloys, bismuth-nickel alloys, bismuth-tin alloys, bismuth-zinc alloys, or bismuth-lead alloys can be cited. By using a conductive resin paste containing such low-melting-point metal particles, even at a thermosetting temperature lower than the melting point of the high-melting-point highly conductive metal particles, a solid-phase and liquid-phase reaction will occur at the contact site between the metal particles in the conductive resin paste and the metal constituting the collector. Thus, in the interface between the conductive resin paste and the surface of the collector, a diffusion region alloyed by solid-phase and liquid-phase reactions is formed around the above-mentioned contact site. This can be used as an alloy layer 144 that firmly bonds the interface.

[0158] As an example of the alloy formed, when silver or a silver alloy is used for the conductive metal particles and copper is used for the current collector, a silver-copper alloy of a high conductive alloy can be cited. In addition, by combining the conductive metal particles with the current collector, a silver-nickel alloy or a silver-palladium alloy can also be formed. With this structure, since the current collector and the buffer layer are more firmly bonded, for example, the effect of suppressing the peeling of the bonded portion due to thermal cycles or impacts can be obtained.

[0159] Furthermore, the shapes of the high melting point highly conductive metal particles and the low melting point metal particles can be any shapes such as spherical, flaky, needle-shaped, etc. In addition, there is no particular limitation on the particle size of the high melting point highly conductive metal particles and the low melting point metal particles. For example, since the smaller the particle size, the lower the temperature at which the alloy reaction and diffusion will proceed, 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.

[0160] In addition, the resin used in the thermosetting conductive resin paste can be any resin that functions as a bonding adhesive, and the appropriate resin is selected according to the manufacturing process adopted, such as printability and coating properties. The resin used in the thermosetting conductive resin paste includes, for example, a thermosetting resin. As thermosetting resins, for example, (i) amino resins such as urea resins, melamine resins, and guanamine resins, (ii) epoxy resins such as bisphenol A type, bisphenol F type, phenol novolac type, and alicyclic type, (iii) oxetane resins, (iv) phenolic resins such as resol type and novolac type, and (v) silicone-modified organic resins such as silicone epoxy resins and silicone polyesters. The resin can be used with only one of these materials, or with a combination of two or more of these materials.

[0161] (Other embodiments)

[0162] The battery involved in the present disclosure is described above based on the embodiments, but the present disclosure is not limited to these embodiments. As long as it does not depart from the main purpose of the present disclosure, the various modifications that can be thought of by those skilled in the art are applied to the embodiments to obtain the scheme, or other schemes constructed by combining some of the constituent elements in the embodiments are all included in the scope of the present disclosure.

[0163] In addition, various changes, substitutions, additions, omissions, etc. can be made to the above-described embodiments within the scope of the claims or the scope equivalent thereto.

[0164] Industrial Availability

[0165] The battery according to the present disclosure can be used as a secondary battery such as an all-solid-state battery used in various electronic devices, automobiles, and the like.

[0166] Description of Reference Numerals

[0167] 1, 100, 200, 300 batteries

[0168] 2 Solid battery cells

[0169] 10. First electrode (positive electrode)

[0170] 11. First current collector (positive electrode current collector)

[0171] 12. First active material layer (positive electrode active material layer)

[0172] 20 Second electrode (negative electrode)

[0173] 21. Second current collector (negative electrode current collector)

[0174] 22. Second active material layer (negative electrode active material layer)

[0175] 30 Solid electrolyte layer

[0176] 40, 140, 240, 340 buffer layer

[0177] 41 PTC materials

[0178] 42 First Metal

[0179] 43 Resin

[0180] 142 Second Metal

[0181] 144 Alloy layer

[0182] 241 PTC layer

[0183] 242, 243 Conductive resin layer

[0184] 343 Metal Layer

[0185] 442 First Metal Layer

[0186] 500 stacked batteries

Claims

1. A battery comprising a first solid battery cell and a buffer layer, The first solid battery cell 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 opposite to the solid electrolyte layer. The buffer layer comprises a PTC material, a resin and a first metal, The first metal is at least one selected from Sn, Cu, Al, Mg and Zn, The buffer layer comprises a PTC layer and a conductive resin layer, The PTC layer comprises the PTC material, The conductive resin layer contains the resin and the first metal and does not contain the PTC material. The conductive resin layer covers the surface of the PTC layer opposite to the current collector.

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

3. The battery according to claim 1 or 2, The conductive resin layer also covers the surface of the PTC layer on the collector side.

4. The battery according to claim 1 or 2, The buffer layer includes a metal layer covering the surface of the PTC layer on the collector side. The metal layer includes the first metal.

5. The battery according to claim 1 or 2, The buffer layer includes an alloy layer in contact with the current collector, The alloy layer is composed of an alloy containing a second metal, The second metal is at least one selected from Sn, Ag, Cu, Bi, Al and Zn.

6. The battery according to claim 5, The second metal is at least one selected from Sn, Bi, Al and Zn.

7. The battery according to claim 1 or 2, The PTC material is a particle, The particles are coated with the first metal.

8. The battery according to claim 1 or 2, further comprising a second solid battery cell, The first solid battery cell and the second solid battery cell are stacked with the buffer layer interposed therebetween.

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

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