JP2018010848A - battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery which can suppress the rise in battery temperature when the battery generates heat owing to short circuit or the like while suppressing the worsening of a battery output performance.SOLUTION: A battery comprises a plurality of unit cells laminated. The plurality of unit cells each have: a pair of current collectors disposed at opposing ends in a laminating direction respectively; and at least one electrode body between the pair of current collectors, provided that the at least one electrode body includes an active material layer of a first electrode and an active material layer of a second electrode different from the first electrode, and a solid electrolyte layer disposed between the first and second electrode active material layers. The current collectors are put in contact with the first electrode active material layer or the second electrode active material layer. The battery further comprises heat-absorbing layers each including a heat-absorbing material and disposed between the unit cells adjacent to each other in the laminating direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a battery including a plurality of stacked solid state batteries and an endothermic layer.

  A battery may suddenly generate heat due to a short circuit caused by an external impact such as nail penetration. In this case, by using an endothermic material for a part of the battery, it is possible to appropriately absorb heat and suppress an increase in temperature.

As a technique related to a battery using such an endothermic material, for example, Patent Document 1 discloses a non-aqueous electrolyte secondary battery in which an endothermic material is provided on at least one of a positive electrode and a negative electrode. Patent Document 2 discloses a lithium secondary battery containing an endothermic substance that causes an endothermic reaction at the time of temperature rise of the battery and suppresses thermal runaway of the battery. This Patent Document 2 describes that an endothermic substance can be contained in the positive electrode and the negative electrode, and a form in which the endothermic substance is mixed into the solid electrolyte is also disclosed.
Further, in Patent Document 3, at least one of a positive electrode and a negative electrode has a conductive layer interposed between a current collector and an electrode mixture, and the conductive layer includes a conductive material and a binder. A non-aqueous secondary battery including a non-aqueous electrolyte solution containing polyvinylidene fluoride is disclosed. And this patent document 3 describes that the mass ratio of acetylene black as a conductive material to polyvinylidene fluoride as a binder is 28:72. Patent Document 4 discloses that a lithium secondary battery having a positive electrode, a negative electrode, and a separator that holds an electrolytic solution disposed between the positive electrode and the negative electrode has a melting point of 65 ° C. or higher and lower than 100 ° C., and a heat of fusion. It is disclosed to add an endothermic agent that is endothermic. Further, FIG. 1 of Patent Document 4 discloses a form in which an endothermic agent layer is disposed between the positive electrode and the separator, and FIG. 3 illustrates a configuration between the positive electrode and the separator and between the negative electrode and the separator. A form in which the endothermic agent layer is disposed between the two is disclosed, and FIG. 4 discloses a form in which the endothermic agent layer is disposed between the negative electrode and the separator. Patent Document 4 also discloses a form in which an endothermic agent is mixed in the positive electrode and / or the negative electrode.

Japanese Patent Laid-Open No. 10-233237 JP-A-11-233150 JP 2012-104422 A JP 2009-238705 A

  As disclosed in Patent Document 1 and Patent Document 4, when a heat absorbing material is used for a secondary battery using an electrolytic solution, it is possible to appropriately absorb heat without greatly degrading ion conduction performance. It is thought that it becomes. On the other hand, as disclosed in Patent Document 2, a battery having a solid electrolyte layer using a flame-retardant solid electrolyte (for example, a lithium ion secondary battery or the like. Hereinafter, it may be referred to as a “solid battery”). )), It is considered possible to absorb heat when the positive electrode, the negative electrode, or the solid electrolyte layer contains a heat absorbing material, but the heat absorbing material generally has low ion conductivity and electronic conductivity. It is considered that the ionic conductivity and the electronic conductivity are remarkably lowered. Since the output performance of a solid state battery decreases when the ionic conductivity or the electronic conductivity decreases, the conventional technology uses a heat absorbing material in the solid state battery to suppress a decrease in output performance while the battery generates heat such as a short circuit. It was difficult to suppress the temperature rise. In addition, the conductive layer disclosed in Patent Document 3 is considered to be able to stop the battery reaction by increasing the resistance when abnormal heat is generated due to a short circuit or the like. However, since this conductive layer takes a long time until the shutdown function for stopping the battery reaction is exhibited, the effect of suppressing the temperature rise of the battery is limited. Therefore, even when the techniques disclosed in Patent Documents 1 to 4 are combined, it is difficult to suppress a rise in battery temperature during battery heat generation such as a short circuit while suppressing a decrease in battery output performance.

  Then, this invention makes it a subject to provide the battery which can suppress the temperature rise of a battery at the time of battery heat_generation | fever, such as a short circuit, suppressing the fall of battery output performance.

  The present inventor provides a positive electrode active material layer, a negative electrode active material layer, and a battery including a plurality of electrode bodies each having a solid electrolyte layer provided between a positive electrode active material layer and a negative electrode active material layer. It was considered to arrange a heat absorbing material having low property outside the electrode body, not inside the electrode body. As a result, at least two current collectors are provided between at least one adjacent electrode bodies to form a unit cell, and an endothermic material is disposed between the unit cells, that is, between the two current collectors. Thus, it has been found that it is possible to suppress an increase in battery temperature during battery heat generation such as a short circuit while suppressing a decrease in the output performance of the battery. The present invention has been completed based on this finding.

In order to solve the above problems, the present invention takes the following means. That is,
The present invention is a battery comprising a plurality of unit batteries stacked, the unit batteries being disposed between a pair of current collectors disposed at both ends in the stacking direction, and the pair of current collectors, respectively. And at least one electrode body comprising a first electrode active material layer, a second electrode active material layer different from the first electrode, and a solid electrolyte layer disposed therebetween. The pair of current collectors is in contact with the active material layer of the first electrode or the active material layer of the second electrode, and includes a heat absorbing layer including a heat absorbing material between unit cells adjacent in the stacking direction. It is.

Here, in the present invention, the “first electrode” refers to a positive electrode or a negative electrode. The “second pole different from the first pole” means that the second pole is a negative electrode when the first pole is a positive pole, and the second pole when the first pole is a negative pole. Is the positive electrode. In the present invention, the pair of current collectors may both be in contact with the active material layer of the first electrode, or both of them may be in contact with the active material layer of the second electrode. One may be in contact with the active material layer of the first electrode and the other may be in contact with the active material layer of the second electrode.
Multiple unit cells are formed in the battery stacking direction, and an endothermic layer is provided between the unit cells, so that the ionic conduction and electronic conduction inside the solid battery are not hindered during normal use of the battery, thus maintaining the output performance of the battery. it can. In addition, when the battery generates heat such as a short circuit, the heat generated in the electrode body inside the battery (for example, the center in the stacking direction) can also be absorbed by the endothermic layer, so that the temperature rise can be quickly suppressed. Thereby, the temperature rise of the battery at the time of battery heat generation, such as a short circuit, can be suppressed, suppressing the fall of battery output performance.

  In the present invention, the endothermic layer is in contact with the first active material layer, between current collectors adjacent in the stacking direction, or in contact with the second active material layer. Further, it may be provided between current collectors adjacent in the stacking direction. As a result, adjacent current collectors have the same pole, and it is not necessary to consider the insulation between the current collectors. In addition to the above effects, the degree of freedom in design such as the thickness of the heat absorption layer is increased. can do.

  In the present invention, the pair of current collectors are preferably in contact with the active material layer of the first electrode or the active material layer of the second electrode. By adopting such a form, the unit battery can be provided with an even number (2, 4, 6,...) Of electrode bodies. Thereby, it can be set as a line symmetrical shape. As a result, in addition to the above effects, the warpage can be reduced when the unit battery is formed, particularly at the time of press molding, so that a battery with less warpage can be provided.

  In the present invention in which each of the pair of current collectors is in contact with the active material layer of the first electrode or the active material layer of the second electrode, the unit cell is disposed at both ends in the stacking direction. A pair of first-pole current collectors, a pair of first-pole current collectors, and a pair of first-pole active material layers respectively disposed so as to contact surfaces facing each other; A pair of solid electrolyte layers disposed so as to be in contact with the surfaces of the pair of first electrode active material layers opposite to the surfaces in contact with the current collector of the first electrode, and the pair of solid electrolyte layers , A pair of active material layers of a second electrode different from the first electrode, the active material layers disposed on the opposite side of the surface contacting the active material layer of the first electrode, and the pair A second electrode current collector disposed between the second electrode active material layers in contact with each of the pair of second electrode active material layers, It is preferable to Bei. By adopting such a form, the unit battery can be provided with two electrode bodies. Thereby, since there is much quantity of the thermal absorption material per electrode body, in addition to the said effect, the heat | fever which generate | occur | produced in the electrode body can be more effectively absorbed in the thermal absorption layer. Further, since the number of electrode bodies constituting the unit battery is small, there is an advantage that it is easy to manufacture.

  In the present invention, the endothermic material provided between the unit cells adjacent to each other in the stacking direction and on the surface of the unit cell disposed at the end in the stacking direction is provided with an endothermic layer and provided in the center in the stacking direction. More than the endothermic material provided at the end of the direction. Here, “the surface of the unit cell disposed at the end in the stacking direction” refers to the upper surface of the unit cell disposed at the upper end in the stacking direction and the lower surface of the unit cell disposed at the lower end in the stacking direction. When a battery including a plurality of unit batteries stacked generates heat more than usual due to a short circuit or the like, heat is more likely to be generated in the center in the stacking direction than at the end in the stacking direction. By disposing more heat-absorbing material at the center in the stacking direction, where heat is more likely to be generated and the temperature is likely to be higher than at the end in the stacking direction, it is easy to suppress the temperature rise of the battery during battery heat generation such as a short circuit.

  Moreover, in the said invention, it is preferable that the number of the electrode bodies with which the unit battery arrange | positioned in the center of the lamination direction is equipped is less than the number of the electrode bodies with which the unit battery arrange | positioned at the end of the lamination direction is equipped. By reducing the number of electrode bodies provided in the unit battery, it is possible to reduce the amount of heat generated during battery heat generation such as a short circuit. In addition, as described above, the center in the stacking direction tends to heat more easily than the end in the stacking direction, and the temperature tends to increase. Therefore, the number of electrode bodies provided in the unit cell arranged in the center in the stacking direction where heat is easily generated is determined. By reducing the number, it is possible to increase the portion between the unit batteries, that is, the portion where the endothermic layer can be arranged, and thus it is easy to suppress the temperature rise of the battery.

  In the present invention, the current collector in contact with the active material layer of the first electrode, or the surface on the active material layer side of the first electrode or in contact with the active material layer of the second electrode. The surface of the current collector on the second electrode active material layer side, or the surface of the current collector on the first electrode active material layer side in contact with the first electrode active material layer side, and It is preferable to provide a PPTC film having a conductive material and a resin on the surface on the second electrode active material layer side of the current collector in contact with the bipolar electrode active material layer. Here, the “PPTC (Polymer Positive Temperature Coefficient) film” refers to a film that functions as a PPTC element (a film that is a PPTC element). The PPTC film requires a predetermined time until the resistance is increased. In the present invention, since the PPTC film is used together with the endothermic layer, the temperature increase of the battery can be suppressed by the endothermic layer until the PPTC film increases in resistance. Then, after the battery reaction is stopped by increasing the resistance of the PPTC film, the heat generated in the battery can be absorbed by the endothermic layer, so that the temperature of the battery can be lowered. .

  In the present invention provided with a PPTC film, the resin is a thermoplastic resin that melts at a temperature higher than 100 ° C.

  ADVANTAGE OF THE INVENTION According to this invention, the battery which can suppress the temperature rise of the battery at the time of battery heat_generation | fever, such as a short circuit, can be provided, suppressing the fall of battery output performance.

It is a figure explaining the battery 10 of this invention. 1 is a diagram illustrating a unit battery 1. FIG. It is a conceptual diagram explaining the heat dissipation mechanism at the time of a short circuit. It is a conceptual diagram explaining the heat dissipation mechanism of a high capacity type battery. It is the schematic for demonstrating arrangement | positioning of a PPTC film | membrane. It is the schematic for demonstrating the preparation methods of an endothermic layer. It is a figure explaining the form of the sample for a test. It is a figure explaining the conditions of a nail penetration test. It is a figure explaining the relationship between the elapsed time after nail penetration and temperature. It is a figure explaining the charging / discharging performance of a battery. It is a figure explaining the relationship between the elapsed time after nail penetration and temperature. It is a figure explaining the result of a PPTC film | membrane characteristic evaluation test. It is a figure explaining the relationship between the elapsed time after nail penetration and temperature.

  The present invention will be described below with reference to the drawings. In addition, the form shown below is an example of this invention and this invention is not limited to the form shown below.

  FIG. 1 is a diagram illustrating a battery 10 of the present invention. 1 is the stacking direction, and FIG. 1 shows the battery 10 in a simplified manner. As shown in FIG. 1, the battery 10 of the present invention accommodates a plurality of unit batteries 1, a sheet-like endothermic layer 3 (hereinafter sometimes referred to as “endothermic sheet 3”), and these. And an exterior body 2. The plurality of unit cells 1 and the endothermic sheets 3 accommodated in the exterior body 2 are stacked so as to be alternately arranged, and the endothermic sheet 3 is arranged at the upper end of the stacking direction, the unit cells 1 adjacent to each other in the stacking direction. It is arrange | positioned in between and the lower end of the lamination direction. Each unit battery 1 has a positive electrode current collector connected to the positive electrode lead 4 and a negative electrode current collector connected to the negative electrode lead 5, and one end of each of the positive electrode lead 4 and the negative electrode lead 5 goes to the outside of the outer package 2. It is led with. A seal member (not shown) is arranged at a location where the positive electrode lead 4 and the negative electrode lead 5 penetrate the outer package 2, and thereby the hermeticity of the outer package 2 is maintained.

  FIG. 2 is a diagram illustrating the unit battery 1. The vertical direction on the paper surface of FIG. 2 is the stacking direction, and FIG. 2 shows the unit battery 1 in a simplified manner. As shown in FIG. 2, the unit battery 1 includes a pair of positive electrode current collectors 1 a disposed at both ends in the stacking direction, and contacts the surfaces of the pair of positive electrode current collectors 1 a facing each other. A pair of disposed positive electrode active material layers 1b, and a pair of solid electrolyte layers disposed so as to be in contact with the surfaces of the pair of positive electrode active material layers 1b opposite to the surfaces in contact with the positive electrode current collector 1a, respectively. 1c, a pair of negative electrode active material layers 1d disposed so as to be in contact with the surfaces of the pair of solid electrolyte layers 1c opposite to the surfaces in contact with the positive electrode active material layer 1b, and the pair of negative electrodes A negative electrode current collector 1e is provided between the active material layers 1d so as to be in contact with each of the pair of negative electrode active material layers 1d. That is, the unit battery 1 includes a positive electrode active material layer 1b and a negative electrode active material layer 1d disposed so as to be in contact with each other, and an electrode body 1f including a solid electrolyte layer 1c disposed therebetween. 1e is provided on each of the upper side and the lower side.

  As described above, in the battery 10 of the present invention, the endothermic sheet 3 is disposed between the unit batteries 1 adjacent in the stacking direction or at the end in the stacking direction. The reason for this will be described below.

  FIG. 3A is a conceptual diagram illustrating a heat dissipation mechanism at the time of a short circuit generated by nail penetration, and FIG. 3B is a diagram illustrating a heat dissipation mechanism at the time of a short circuit generated in a high capacity battery by nail penetration. FIG. 3A shows that a nail X is stuck from the upper side in the stacking direction of two solid batteries 9 each including a positive electrode current collector, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector in this order. A state in which a short circuit occurs and heat is thereby generated is shown in a simplified manner. On the other hand, FIG. 3B shows a simplified state in which a plurality of unit cells 1 are short-circuited when the nail X is pierced from the upper side in the stacking direction, thereby generating heat. 3A and 3B is the stacking direction.

  As shown in FIG. 3A, when the battery generates heat during nail penetration, the heat diffuses in the in-plane direction (direction intersecting the stacking direction) through the current collector of the solid battery 9, and the positive electrode active material layer And also diffused in the stacking direction (battery outermost surface direction) through the negative electrode active material layer.

  As shown in FIG. 3B, when a short circuit occurs due to the nail X being stuck in the stacked unit cells 1, heat is diffused in the in-plane direction and the stacking direction, as in FIG. 3A. . At this time, the heat generated in the unit cells 1 arranged in the center in the stacking direction is less likely to escape to the end in the stacking direction than the heat generated in the unit cells 1 arranged in the end in the stacking direction. Therefore, in the battery of the form shown in FIG. 3B, heat is likely to be generated at the center in the stacking direction. In the present invention, by using the endothermic sheet 3, this heat distortion is suppressed. It is not the inside of the unit cell 1 but the endothermic sheet 3 that is arranged between the unit cells 1 adjacent in the stacking direction or at the end in the stacking direction, that is, on the surface of the current collector provided in the unit cell 1. This is to prevent the movement of ions and electrons in the interior of 1. By disposing the endothermic sheet 3 between the unit cells 1 adjacent to each other in the stacking direction or at the end in the stacking direction, it is possible to absorb heat without hindering the movement of ions inside the unit cell 1. It is possible to suppress a temperature rise during battery heat generation such as a short circuit while suppressing a decrease in output performance.

  The materials that can be used for the battery 10, the form of each layer, and the manufacturing method will be described below.

1. Endothermic Layer The battery according to the present invention has one characteristic in the arrangement of the endothermic layer. In the present invention, the form of the endothermic layer is not particularly limited as long as it has a substance (endothermic material) that exhibits endothermic performance in a predetermined temperature range (for example, a temperature range of 60 ° C. to 250 ° C.). The endothermic layer in the present invention preferably contains at least one organic endothermic material selected from sugar alcohols and hydrocarbons and an inorganic hydrate from the viewpoint of making the endothermic performance easy to improve. Moreover, it is preferable that the heat absorption layer contains the binder further from a viewpoint of making it easy to improve a moldability.

1.1. Organic endothermic material In the present invention, the endothermic layer preferably contains at least one organic endothermic material selected from sugar alcohols and hydrocarbons. The organic endothermic material normally exists as a solid in a battery, but absorbs heat by melting when the battery generates heat such as a short circuit (hereinafter sometimes referred to as “abnormal heat generation”). As a result, the organic endothermic material melted around the nail can be adhered during the nail penetration test of the battery, so that the amount of current flowing to the nail during the nail penetration can be reduced, and as a result, the abnormal heat generation of the battery is suppressed. An effect (hereinafter, this effect may be referred to as a “shutdown effect”) is obtained. Such an effect is a characteristic effect exhibited by the endothermic layer containing the organic endothermic material, and such an effect cannot be obtained in the endothermic layer made of inorganic hydrate or inorganic hydroxide.

  According to the inventor's knowledge, both sugar alcohols and hydrocarbons are (I) materials that absorb heat by melting, (II) are softer than inorganic hydrates, and can be plastically deformed during molding, (III) Difficult to react with inorganic hydrates. Therefore, even if any of sugar alcohol and hydrocarbon is included in the endothermic layer, the density of the endothermic layer can be appropriately increased, and the unit of the endothermic layer can be obtained by a synergistic effect with the inorganic hydrate. The endothermic amount per volume can be greatly increased. Preferably, a sugar alcohol and a hydrocarbon having a high endothermic temperature (melting temperature) and a large endothermic amount per unit volume are selected. As far as the present inventors have confirmed, sugar alcohols are preferable to hydrocarbons.

  The organic endothermic material preferably has an endothermic onset temperature and an endothermic peak temperature at 60 ° C. or higher and 250 ° C. or lower from the viewpoint of being able to absorb heat more appropriately during abnormal heat generation of the battery. Alternatively, the organic endothermic material is preferably one that completes the endothermic reaction at 60 ° C. or more and 250 ° C. or less in a DSC curve obtained by differential scanning calorimetry (in an argon atmosphere, a temperature increase rate of 10 ° C./min). Examples of such hydrocarbons include hectane and anthracene. On the other hand, examples of the sugar alcohol include mannitol, xylitol, erythritol, lactitol, maltitol, sorbitol, galactitol and the like. The most preferred sugar alcohol is mannitol. As far as the present inventors have confirmed, mannitol has a large endotherm at 90 ° C. or more and 200 ° C. or less compared to other sugar alcohols. Further, by using mannitol, the heat generation temperature at the time of abnormal heat generation of the battery can be matched with the heat absorption temperature of the heat absorption layer.

1.2. Inorganic hydrate In the present invention, the endothermic layer preferably contains an inorganic hydrate. The inorganic hydrate exists as a solid during normal battery operation, and absorbs heat by releasing hydration water during abnormal battery heat generation.

  In view of more appropriate heat absorption during abnormal heat generation of the battery, it is preferable that the inorganic hydrate lose at least a part of the hydrated water at any temperature between 60 ° C. and 250 ° C. Alternatively, the inorganic hydrate is preferably one in which the endothermic reaction is completed at 60 ° C. or more and 250 ° C. or less in a DSC curve obtained by differential scanning calorimetry (under an argon atmosphere, a heating rate of 10 ° C./min). Specific examples of such inorganic hydrates include calcium sulfate dihydrate, copper sulfate (II) pentahydrate, lithium sulfate monohydrate, magnesium chloride dihydrate, zirconium sulfate. (IV) tetrahydrate. The most preferred inorganic hydrate is calcium sulfate dihydrate. Calcium sulfate dihydrate has a large endotherm at 60 ° C. or more and 250 ° C. or less. Further, by using calcium sulfate dihydrate, the heat generation temperature at the time of abnormal heat generation of the battery can be matched with the heat absorption temperature of the heat absorption layer.

1.3. Binder In the present invention, the endothermic layer may contain a binder. The binder binds the organic endothermic material and the inorganic hydrate. The binder may be any one that does not cause a chemical reaction with respect to the organic endothermic material and the inorganic hydrate. Various binders such as butadiene rubber (BR), acrylate butadiene rubber (ABR), and polyvinylidene fluoride (PVdF) can be used.

  In addition, in the range which does not inhibit the effect of this invention, components other than said organic endothermic material, inorganic hydrate, and a binder may be contained in the endothermic layer.

1.4. Content of each component in the endothermic layer The endothermic layer preferably contains 5% by mass to 95% by mass of the organic endothermic material and 5% by mass to 95% by mass of the inorganic hydrate. Moreover, it is preferable that an endothermic layer contains 98 mass% or more of organic endothermic materials and inorganic hydrates in total. On the other hand, when the endothermic layer contains a binder, the content is preferably 2% by mass or less.

On the other hand, the present inventor has shown that the endothermic layer exhibits a predetermined coexistence effect when the endothermic layer contains a large amount of the above-mentioned organic endothermic material rather than the inorganic hydrate on a mass basis through intensive studies. I found out. That is, the endothermic layer contains 50% by mass or more of the organic endothermic material based on the total of the organic endothermic material and the inorganic hydrate (100% by mass), or the endothermic layer contains 10 mg / cm ^{2 of the} organic endothermic material. It is most preferable to include the above. As a result, the density of the endothermic layer increases to 90% or more, and the endothermic layer has a shutdown effect (for example, during the nail penetration test, the amount of current flowing through the nail during nail penetration can be reduced, resulting in abnormal heat generation of the battery. (The same applies to the following).

1.5. Shape of endothermic layer The shape of the endothermic layer may be appropriately determined according to the shape of the battery, but is preferably in the form of a sheet. In this case, the thickness of the endothermic layer is preferably 5 μm or more and 500 μm or less. The lower limit is more preferably 0.1 μm or more, and the upper limit is more preferably 1000 μm or less. By making the endothermic layer into a sheet, the volume ratio of the endothermic layer in the battery can be reduced. In addition, the endothermic layer according to the present invention includes the organic endothermic material that can be plastically deformed, so that the endothermic layer has excellent moldability and excellent flexibility than the endothermic layer made of inorganic hydrate. Can be. That is, by adopting such a configuration, even if the endothermic layer is thinned, it can be made difficult to break.

  The endothermic layer preferably has a density of 80% or more. More preferably, the density is 85% or more. In the present invention, such a high density can be achieved, for example, when the endothermic layer contains the organic endothermic material. When the density is high, the amount of heat absorbed per unit volume can be increased. In addition, since heat from the battery can be quickly propagated in the endothermic layer, there is an effect that heat can be quickly absorbed with respect to abnormal heat generation of the battery. The “dense density” of the endothermic layer is calculated as follows. First, the weight and volume of the endothermic layer are measured, and the density is calculated. The density can be calculated by dividing the calculated density by the true density.

1.6. In the present invention, for example, the endothermic layer can be produced by molding the organic endothermic material, inorganic hydrate, and optionally a binder, into various shapes. it can. Molding may be dry or wet. For example, in the case of wet molding, each of the above components is added to a solvent to form a slurry, and the slurry is applied onto a substrate, dried, and optionally pressed to form a sheet-like endothermic layer as described above. Can be obtained. As the solvent, for example, heptane, ethanol, N-methylpyrrolidone, butyl acetate, and butyl butyrate can be used.

2. Exterior Body The exterior body is not particularly limited in material and shape as long as it can accommodate a unit battery and an endothermic layer. For example, a metal housing, a laminated film having a laminated metal foil and a resin film, or the like can be used as the exterior body. In addition, it is good also as a battery by preparing several exterior bodies which included the unit battery, and enclosing this further in an exterior body.

3. Unit Battery In the present invention, the unit battery accommodated in the exterior body is a solid battery. The unit battery according to the present invention includes a pair of current collectors disposed at both ends in the stacking direction, a first electrode active material layer disposed so as to be in contact with each other between the pair of current collectors, and the What is necessary is just to comprise the active material layer of the 2nd pole different from a 1st pole, and the electrode body which comprises the solid electrolyte layer arrange | positioned among these. Although FIG. 2 shows the unit battery 1 including two electrode bodies, the number of electrode bodies included in the unit battery in the present invention can be any number of 1 or more. However, it is preferable that the number of electrode bodies provided in the unit battery is an even number (2, 4, 6,...) From the viewpoint of easily providing a battery with less warpage.

  Hereinafter, a lithium all-solid battery will be described as an example of the unit battery. However, a battery applicable as the unit battery in the present invention is not limited to a lithium battery. A sodium battery may be used, and other metal ion batteries may be used. Further, the unit battery may be a primary battery or a secondary battery. However, abnormal heat generation of the battery is likely to occur when the battery is used for a long time by repeated charging and discharging. That is, the secondary battery is preferable to the primary battery from the viewpoint that the effect of the present invention becomes more remarkable.

3.1. Positive electrode active material layer and negative electrode active material layer The positive electrode active material layer and the negative electrode active material layer include at least an active material, and optionally further include a solid electrolyte, a binder, and a conductive additive. As the active material, any active material capable of occluding and releasing lithium ions can be used. Of the active materials, two materials having different potentials (charge / discharge potentials) for occluding and releasing lithium ions are selected, a material exhibiting a noble potential is used as a positive electrode active material, and a material exhibiting a base potential is described later as a negative electrode active material. Can be used respectively. For example, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ can be used as the positive electrode active material, and graphite can be used as the negative electrode active material. The solid electrolyte is preferably an inorganic solid electrolyte. This is because the ionic conductivity is higher than that of the organic polymer electrolyte. Moreover, it is because it is excellent in heat resistance compared with an organic polymer electrolyte. Preferred solid electrolytes include oxide solid electrolytes such as Li ₃ PO ₄ and sulfide solid electrolytes such as Li ₂ S—P ₂ S ₅ . Among these, a sulfide solid electrolyte containing Li ₂ S—P ₂ S ₅ is particularly preferable. As the binder, the same binder as that used for the endothermic layer can be used. As the conductive assistant, carbon materials such as acetylene black and ketjen black, and metal materials such as nickel, aluminum, and stainless steel can be used. The content of each component in the positive electrode active material layer and the negative electrode active material layer and the shapes of the positive electrode active material layer and the negative electrode active material layer can be the same as those in the past. In addition, the positive electrode active material layer and the negative electrode active material layer are obtained by obtaining a slurry-like electrode composition by kneading an active material and a solid electrolyte, a binder, and a conductive additive that are optionally contained in a solvent. The electrode composition can be produced by a process such as applying to the surface of the current collector and drying.

3.2. Positive electrode current collector and negative electrode current collector In the present invention, an endothermic layer is provided on the surface of the positive electrode current collector or the negative electrode current collector (the surface opposite to the positive electrode active material layer or the negative electrode active material layer). The positive electrode current collector and the negative electrode current collector may be formed of a metal foil, a metal mesh, or the like. Metal foil is particularly preferable. When a metal foil is used as the current collector, even if an endothermic layer is provided on the surface of the current collector, the endothermic layer is not in direct contact with the positive electrode active material layer or the negative electrode active material layer. The material does not react. Cu, Ni, Al, Fe, Ti etc. can be illustrated as a metal which can comprise a positive electrode collector and a negative electrode collector.

3.3. Solid electrolyte layer The solid electrolyte layer comprises a solid electrolyte and optionally a binder. The solid electrolyte is preferably the inorganic solid electrolyte described above. As the binder, the same binder as that used for the endothermic layer can be used. Content of each component in a solid electrolyte layer can be made into the same as the past. The solid electrolyte layer is obtained by applying a slurry electrolyte composition by mixing a solid electrolyte and an arbitrarily contained binder in a solvent to obtain a slurry electrolyte composition, and then applying the electrolyte composition to the surface of the substrate and drying it. It can be manufactured through a process such as. The thickness of the solid electrolyte layer can be, for example, about several tens of μm.

  In the above description related to the present invention, the unit battery 1 and the endothermic layer 3 having one electrode body on each of the upper and lower sides of the negative electrode current collector are exemplified, but the battery of the present invention is in this form. It is not limited. When a unit battery having two electrode bodies and an endothermic layer are laminated to form a battery of the present invention, the unit battery 1 has a configuration in which the positive electrode and the negative electrode are reversed (a pair of negative electrode current collectors at both ends in the stacking direction). The negative electrode active material layer is disposed so as to be in contact with each negative electrode current collector, and the positive electrode current collector is disposed at the center in the stacking direction, and the positive electrode active material is disposed on the upper and lower surfaces of the positive electrode current collector. A unit battery of a form in which layers are arranged may be provided.

  Moreover, in the said description, although the form with which the unit battery which has two electrode bodies was provided was illustrated, this invention is not limited to the said form. The number of electrode bodies provided in the unit battery in the present invention may be only one, or may be three or more.

  Moreover, in the said description, although the form with which the same number of electrode bodies (two electrode bodies) are provided in all the unit batteries with which a battery is equipped was illustrated, this invention is not limited to the said form. The unit batteries provided in the battery of the present invention may have different numbers of electrode bodies. From the viewpoint of forming a battery of the present invention by laminating a plurality of unit batteries each having a different number of electrode bodies and an endothermic layer, from the viewpoint of easily suppressing the temperature rise at the center in the stacking direction where heat is easily generated, It is preferable that the number of electrode bodies provided in the unit battery arranged at the center in the stacking direction is smaller than the number of electrode bodies provided in the unit battery arranged at the end in the stacking direction.

  Moreover, in the said description, although the form in which the endothermic layer 3 is arrange | positioned between the unit cell adjacent to the upper end and lower end of a lamination direction and a lamination direction was illustrated, this invention is not limited to the said form. It is also possible to adopt a form in which no endothermic layer is disposed at the upper end and / or the lower end in the stacking direction. However, from the viewpoint of making it easy to suppress temperature rise by disposing an endothermic layer in a place where heat is likely to be generated, at least between unit cells adjacent in the stacking direction, more preferably at least adjacent in the center of the stacking direction. It is preferable to dispose an endothermic layer between the unit cells.

Moreover, in the said description, although the endothermic layer 3 of the same form was arrange | positioned between the upper end and lower end of a lamination direction, and the unit cell adjacent to a lamination direction, this invention is not limited to the said form. . In the present invention, depending on the position in the stacking direction, the form of the endothermic layer may be changed.From the viewpoint of providing a battery in a form that easily absorbs heat appropriately, It is preferable to dispose more endothermic material than the end in the stacking direction. Here, as a specific form of disposing more endothermic material in the center of the stacking direction than the end of the stacking direction,
(1) After preparing a plurality of endothermic layers having the same form, the number of endothermic layers arranged in the center in the stacking direction is made larger than the number of endothermic layers disposed at the end in the stacking direction (for example, stacking direction). 3 to 5 endothermic layers are arranged between adjacent unit cells at the center of the center, and one endothermic layer is arranged at the end in the stacking direction.)
(2) After preparing a plurality of endothermic layers with different contents of the endothermic material, an endothermic layer having a relatively high endothermic material content among the plurality of endothermic layers is arranged at the center in the stacking direction. In addition, an endothermic layer having a relatively small endothermic material content among the plurality of endothermic layers is disposed at the end in the stacking direction. (3) A plurality of endothermic layers having different thicknesses using the same raw material. After the preparation, a relatively thick endothermic layer among the plurality of endothermic layers is disposed at the center in the stacking direction, and the end of the stacking direction is relatively positioned among the plurality of endothermic layers. For example, a thin endothermic layer may be disposed.

  Further, in the above description, since an example in which all the unit batteries are provided with two electrode bodies is illustrated, the endothermic sheet 3 is provided between the positive electrode current collectors 1a respectively provided in the unit batteries adjacent in the stacking direction. Although provided, this invention is not limited to the said form. For example, when a unit battery having a configuration in which the positive electrode and the negative electrode are reversed in the unit battery 1 is provided, an endothermic sheet is provided between the negative electrode current collectors respectively provided in the unit batteries adjacent in the stacking direction. It can be in the form. In addition, for example, when the battery of the present invention is provided with a unit battery having an odd number of electrode bodies, the positive electrode current collector provided in one unit battery adjacent in the stacking direction and the other unit battery are provided. An endothermic sheet can be provided between the negative electrode current collector provided.

3.4. PPTC membrane FIG. 4 is a diagram illustrating a preferred embodiment of the present invention. In FIG. 4, a portion where the PPTC film 6 is provided is extracted from the battery (battery provided with an endothermic layer) of the present invention, and this is shown enlarged and simplified. 4 shows a mode in which the PPTC film 6 is provided on the surface of the positive electrode current collector 1a on the positive electrode active material layer 1b side, the present invention is not limited to this mode. The PPTC film may be provided on the surface of the negative electrode current collector on the negative electrode active material layer side, the surface of the positive electrode current collector on the positive electrode active material layer side, and the negative electrode current collector on the negative electrode active material layer side The surface may be provided.

  As shown in FIG. 4, the battery of the present invention has a current collector surface in contact with the active material layer on the surface of the active material layer side (in the example of FIG. 4, the positive electrode active material 1a of the positive electrode current collector 1a). A PPTC film 6 having a conductive material and a resin is preferably provided on the surface of the material layer 1b. The PPTC film 6 is a film that increases the resistance at a predetermined temperature of 100 ° C. or higher, and stops the battery reaction by increasing the resistance. By stopping the battery reaction, it becomes possible to prevent further heat generation of the battery.

  The PPTC film requires a predetermined time until the resistance is increased. In the present invention, since the PPTC film 6 is provided together with the endothermic layer (the endothermic sheet 3), the temperature increase of the battery can be suppressed by the endothermic layer until the PPTC film 6 is increased in resistance. Then, after the battery reaction is stopped by increasing the resistance of the PPTC film 6, the heat generated in the battery can be absorbed by the endothermic layer, so that the temperature of the battery can be lowered. Become.

  The PPTC film 6 contains a conductive material and a resin. The conductive material used for the PPTC film 6 is not particularly limited as long as it is a conductive material that can be used for a PPTC element and can withstand the environment during use of the battery 10. Examples of such conductive materials include carbon materials such as furnace black, ketjen black, and acetylene black, metals such as silver, and conductive ceramics such as titanium carbide. The shape of the conductive material used for the PPTC film 6 is not particularly limited. For example, the conductive material is preferably in the form of a powder from the viewpoint of easily dispersing the conductive material in the PPTC film 6.

The resin used for the PPTC film 6 can be used for a PPTC element, can withstand the environment when the battery 10 is used, and is a resin that melts at a temperature higher than 100 ° C. There is no particular limitation. Examples of such a resin include polyvinylidene fluoride (hereinafter referred to as “PVDF”), polyethylene (PE), polypropylene (PP), and the like. These resins are thermoplastic resins. In addition, among the resins described above, the molecular weight of the PPTC film 6 remains between the current collector and the active material layer at a high temperature, so that an internal short circuit can be easily suppressed for a long time. It is preferable to use a resin having a large size. Examples of such a resin include ultra high molecular weight polyethylene and PVDF having a molecular weight of 1.0 × 10 ⁵ or more.

  An example of a method for producing the PPTC film 6 will be described below. When the PPTC film 6 is produced, the carbon material is dispersed by dispersing the carbon material, which is a conductive material, in an organic solvent such as N-methyl-2-pyrrolidone (hereinafter referred to as “NMP”). Prepare the solution. Moreover, a resin dispersion solution is prepared by dispersing PVDF in NMP. Thereafter, the conductive layer forming composition prepared by mixing the carbon material dispersion solution and the resin dispersion solution is applied to the front surface (for example, the front and back surfaces) of the current collector, and then dried to obtain a PPTC film. 6 can be produced. The PPTC film 6 that can be produced in this manner is preferably thinned as long as the above effects can be exhibited, from the viewpoint of easily increasing the energy density of the battery. Further, from the viewpoint of making the PPTC film 6 in a form in which resistance can be easily increased, it is preferable to heat-treat at a temperature in the range of 120 ° C. to 165 ° C. after the PPTC film is formed on the conductive layer. As a result, the resistance of the solid battery is low during normal operation (for example, 100 ° C. or lower), and it is easy to increase the resistance after the solid battery is heated and heated to 150 ° C. or higher. It becomes easy to stop. As a result, the battery performance is high due to the low resistance of the PPTC film 6 during normal operation, and the resistance of the PPTC film 6 increases only at high temperatures, and the battery reaction is safely stopped to suppress the temperature rise. A battery can be provided.

1. Production of endothermic layer and unit cell 1.1. Production of Endothermic Layer An endothermic layer was formed on the positive electrode current collector by the method shown in FIG. First, an organic endothermic material (mannitol), an inorganic hydrate (calcium sulfate dihydrate), and a solvent (heptane) containing a binder (acrylate butadiene rubber, ABR) are prepared ("Weighing" in FIG. 5). These were mixed and a solid content was dispersed in a solvent using an ultrasonic homogenizer to obtain a slurry (“kneading” in FIG. 5). The obtained slurry was coated on a positive electrode current collector (aluminum foil) and then dried (“Coating / Drying” in FIG. 5), and then pressed by a cold isostatic press (CIP). (4 ton / cm ² ) (“pressing step” in FIG. 5), an endothermic layer was formed on the positive electrode current collector. The mass ratio of the organic endothermic material, the inorganic hydrate, and the binder in the endothermic layer was organic endothermic material: inorganic hydrate: binder = 49: 49: 2.

1.2. Synthesis of Solid Electrolyte 10LiI-90 (0.75Li ₂ S-0.25P ₂ S ₅ ), which is a sulfide solid electrolyte, was synthesized by the method described in JP 2012-48973 A. The synthesized sulfide solid electrolyte was crystallized and finely divided by the method described in JP-A No. 2014-102987.

1.3. Preparation of positive electrode mixture slurry LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (manufactured by Nichia Corporation, average particle diameter (D ₅₀ ) = 5 μm) and obtained by coating LiNbO ₃ A positive electrode mixture slurry is obtained by mixing 52 g, 1 g of vapor grown carbon fiber (VGCF) (manufactured by Showa Denko KK), 17 g of the sulfide solid electrolyte, and 15 g of dehydrated heptane (manufactured by Kanto Chemical Co., Inc.). It was. For coating LiNbO ₃ onto LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , the method described in JP 2010-73539 A was followed.

1.4. Preparation of Negative Electrode Mixture Slurry 36 g of graphite (Mitsubishi Chemical Co., Ltd.), 25 g of the sulfide solid electrolyte and 32 g of dehydrated heptane (Kanto Chemical Co., Ltd.) were mixed to obtain a negative electrode mixture slurry.

1.5. Preparation of unit battery Aluminum foil coated with an endothermic layer as a positive electrode current collector and copper foil as a negative electrode current collector were prepared, and the above-described positive electrode mixture slurry and negative electrode mixture slurry were respectively applied and dried. A pair of positive electrodes having a positive electrode active material layer on the surface of the current collector and a negative electrode having a negative electrode active material layer on the front and back surfaces of the negative electrode current collector were obtained. By placing the above-mentioned sulfide solid electrolyte (solid electrolyte layer) between the pair of positive electrode active material layers and the negative electrode active material layers formed on the front and back surfaces of the negative electrode current collector, pressing and integrating them, A unit cell having two electrode bodies was obtained. A plurality of unit cells were produced by the same method.

2. Heating verification test The temperature was measured in the form shown in FIG. 6 using a plurality of unit cells produced by the above-described method and a thermocouple. As shown in FIG. 6, three thermocouples are arranged at the center in the stacking direction of the unit cells and two at the upper end in the stacking direction, and are sandwiched between a pair of silicon sheets, a bake plate, and a restraint plate. Fixed. After operating the unit cell in this state, a nail having a diameter of 8 mm and a tip angle of 60 ° was pierced at a speed of 25 mm / s so as to penetrate the pair of restraint plates in a temperature environment of 25 ° C. As shown in FIG. 6, the distance between the thermocouple arranged at the upper end of the stacking direction and the nail is 16 mm, and among the thermocouples arranged in the center of the stacking direction, the distance between the thermocouple closest to the nail and the nail is 14 mm. FIG. 7 shows the conditions of the nail penetration test, and FIG. 8 shows the relationship between the elapsed time after the nail penetration and the temperature. The vertical axis in FIG. 8 is the temperature [° C.], and the horizontal axis is the elapsed time [s] after nail penetration.

  As shown in FIG. 8, the temperature at the center in the stacking direction of the battery was higher than the temperature at the end in the stacking direction. The reason why the temperature in the center in the stacking direction was high was that the heat was burned.

3. Battery Performance Evaluation Test A battery of the present invention having the form shown in FIG. 1 was prepared using the 10 unit batteries and the endothermic layer prepared by the method described above. On the other hand, a comparative battery was prepared in the same manner except that the endothermic layer was not used. The charge / discharge performance of the battery of the present invention and the battery of the comparative example was investigated by making the charge / discharge conditions the same except that the batteries used were different. The results are shown in FIG. The vertical axis of FIG. 9 is voltage [V], and the horizontal axis is capacity [mAh / g].

  As shown in FIG. 9, the battery of the present invention and the battery of the comparative example had the same charge characteristics and almost the same discharge characteristics. From this result, it was found that the battery performance hardly changed even when an insulating endothermic layer was disposed between the surface of the unit battery or between adjacent unit batteries.

4). Endothermic performance investigation Using the battery of the present invention used in the above "3. Battery performance evaluation test" and the battery of the comparative example, a battery nail penetration test was performed under the conditions shown in FIG. The endothermic performance of the endothermic layer was investigated by investigating the relationship between the elapsed time and the temperature measured by a thermocouple installed in the center of the stacking direction. The results are shown in FIG. The vertical axis in FIG. 10 is the temperature [° C.], and the horizontal axis is the elapsed time [s] after nail penetration.

As shown in FIG. 10, the battery of the present invention (with an endothermic sheet) gradually increased in temperature immediately after nail penetration and increased until about 30 seconds had passed since nail penetration. It was almost constant. This is considered to be because the temperature increase of the battery was suppressed by the endothermic layer provided in the battery of the present invention.
On the other hand, as shown in FIG. 10, the battery of the comparative example (without endothermic sheet) rapidly increased in temperature immediately after nail penetration and increased in temperature until about 15 seconds had passed since nail penetration. . When evaluated by the temperature increase obtained by subtracting the temperature before nail penetration from the maximum temperature after nail penetration, the temperature increase of the battery of the comparative example was about 5 times the temperature increase of the battery of the present invention. It was.
From the above, according to the present invention, the temperature increase after nail penetration could be reduced to about 1/5 of the case where no endothermic layer was used. When this result and the result shown in FIG. 9 are combined, according to the present invention, there is provided a battery capable of suppressing an increase in battery temperature during battery heat generation due to a short circuit while suppressing a decrease in battery output performance. It was confirmed that it was possible.

5. Production and performance evaluation of PPTC film 5.1. Production of PPTC film A conductive material, furnace black powder having an average primary particle diameter of 66 nm (manufactured by Tokai Carbon Co., Ltd.) and PVDF (Kureha KF Polymer L # 9130, produced by Kureha Co., Ltd.), in a volume ratio, are as follows: Weighed so that PVDF = 20: 80. And the paste-form composition for PPTC films | membranes was produced by mixing these with NMP (made by Nippon Refine Co., Ltd.).
Next, the paste composition for PPTC film was applied to the surface of an Al foil having a thickness of 15 μm as a current collector so that the thickness of the PPTC film after drying was 10 μm. Then, the collector with a PPTC film | membrane which has a PPTC film | membrane on the surface was produced by drying over 1 hour in a 100 degreeC stationary drying furnace.

5.2. PPTC Film Characteristic Evaluation The current collector with a PPTC film produced in this way is punched into a circular shape with a diameter of 11.28 mm (area 1 cm ² ), and then an Al foil is stacked on the PPTC film side, and this is made into a circle of the same diameter It was sandwiched between column terminals. Thereafter, the terminals sandwiching the current collector with the PPTC film were installed in a thermostatic chamber, and the electrical resistance was measured when the temperature was increased to 200 ° C. at a constant rate of temperature increase. Specifically, a constant current of 1 mA was applied between the terminals, the voltage between the terminals at this time was measured, and the resistance value was calculated. The results are shown in FIG. In FIG. 11, the horizontal axis represents temperature [° C.], and the vertical axis represents resistance [Ω · cm ² ]. As shown in FIG. 11, the resistance of the current collector with a PPTC film rapidly increased when the temperature exceeded 160 ° C.

5.3. Temperature rise verification test The battery of the present invention (without PPTC film) used in “3. Battery performance evaluation test”, and a current collector with a PPTC film comprising a PPTC film on the surface of the positive electrode active material layer side as a positive electrode current collector 7 using the battery (with PPTC film) of the present invention constructed in the same manner as the battery without the PPTC film except that the heat absorption layer is thinner than the battery without the PPTC film. A battery nail penetration test was performed under the conditions indicated. And the relationship between the elapsed time after nail penetration and the temperature measured with the thermocouple installed in the center of the lamination direction was investigated. The results are shown in FIG. The vertical axis in FIG. 12 is the temperature [° C.], and the horizontal axis is the elapsed time [s] after nail penetration. Table 1 shows the thickness of the endothermic layer in the battery without the PPTC film and the thickness of the endothermic layer and the PPTC film in the battery with the PPTC film.

  As shown in Table 1, the total thickness of the PTTC film and the endothermic layer in the battery with the PPTC film is 50 μm, and this thickness is thinner than the thickness of the endothermic layer in the battery without the PPTC film of 90 μm. It was. On the other hand, as shown in FIG. 12, in the battery with the PPTC film, the rate of temperature increase after nail penetration is slower than the battery without the PPTC film, and the maximum temperature reached after nail penetration is no PPTC film. It was lower than the battery. The reason why the temperature rise rate was slower in the battery with the PPTC film is that the heat absorption by the endothermic layer using the endothermic effect due to the phase change is faster than the resistance increase of the PPTC film. It is done. From this result, it was confirmed that by adopting a configuration in which the PPTC film is provided together with the endothermic layer, it is easy to suppress the temperature rise of the battery when the battery generates heat such as a short circuit.

  Further, since the endothermic amount of the endothermic layer is proportional to the amount of the endothermic material, it is considered that the use of a large amount of the endothermic material facilitates temperature suppression during battery heat generation such as a short circuit. However, when a large amount of the endothermic material is used, there is a concern that the battery volume increases. On the other hand, as shown in FIG. 12, the combined use of the PTTC film and the endothermic layer reduces the thickness of the entire battery and suppresses the increase in battery volume while suppressing the increase in battery temperature. It becomes possible. Therefore, by using the PTTC film and the endothermic layer in combination, a battery capable of improving the safety of misuse in a compact manner can be provided.

DESCRIPTION OF SYMBOLS 1 ... Unit battery 1a ... Positive electrode collector 1b ... Positive electrode active material layer 1c ... Solid electrolyte layer 1d ... Negative electrode active material layer 1e ... Negative electrode collector 1f ... Electrode body 2 ... Exterior body 3 ... Endothermic layer (endothermic sheet)
4 ... Positive electrode lead 5 ... Negative electrode lead 6 ... PPTC film 9 ... Solid battery 10 ... Battery

Claims (8)

A battery comprising a plurality of unit batteries stacked,
The unit battery includes a pair of current collectors disposed at both ends in the stacking direction, a first electrode active material layer disposed between the pair of current collectors, and a first electrode different from the first electrode. Comprising at least one electrode body comprising a bipolar active material layer and a solid electrolyte layer disposed therebetween,
The pair of current collectors are in contact with the active material layer of the first electrode or the active material layer of the second electrode,
A battery comprising an endothermic layer including an endothermic material between unit cells adjacent in the stacking direction. The endothermic layer is in contact with the first active material layer, between the current collectors adjacent in the stacking direction, or in contact with the second active material layer, in the stacking direction. The battery according to claim 1, provided between adjacent current collectors. 3. The battery according to claim 1, wherein each of the pair of current collectors is in contact with the active material layer of the first electrode or the active material layer of the second electrode. The unit cell is
A pair of first pole current collectors disposed at both ends in the stacking direction;
A pair of first electrode active material layers, each disposed so as to be in contact with mutually facing surfaces of the pair of first electrode current collectors;
A pair of solid electrolyte layers disposed so as to be in contact with the surfaces of the pair of first electrode active material layers opposite to the surfaces contacting the current collector of the first electrode,
A pair of second electrodes different from the first electrode, disposed so as to be in contact with the surfaces of the pair of solid electrolyte layers opposite to the surfaces contacting the active material layer of the first electrode, respectively. An active material layer, and
4. A second pole current collector disposed between the pair of second pole active material layers and in contact with each of the pair of second pole active material layers. 5. The battery described in 1. Between the unit cells adjacent to each other in the stacking direction, and on the surface of the unit cells disposed at the end in the stacking direction, the heat absorption layer is provided,
The battery according to any one of claims 1 to 4, wherein the endothermic material provided at the center in the stacking direction is larger than the endothermic material provided at an end in the stacking direction. The number of the electrode bodies provided in the unit battery disposed in the center in the stacking direction is smaller than the number of the electrode bodies provided in the unit battery disposed at the end in the stacking direction. The battery according to any one of 5. Further, the surface of the current collector that is in contact with the active material layer of the first electrode, on the active material layer side of the first electrode, or
The surface of the current collector in contact with the active material layer of the second electrode, or the surface on the active material layer side of the second electrode, or
The surface of the current collector in contact with the active material layer of the first electrode, the surface on the active material layer side of the first electrode, and the current collector in contact with the active material layer of the second electrode On the surface of the second electrode on the active material layer side,
The battery according to claim 1, comprising a PPTC film having a conductive material and a resin. The battery according to claim 7, wherein the resin is a thermoplastic resin that melts at a temperature higher than 100 ° C.