JP2018190538A - All solid battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To disclose an all-solid-state battery capable of suppressing an excessive temperature rise in power generation elements at both ends in the stacking direction during a nail penetration test. A power generation element has a laminated body in which a positive electrode current collector layer, a positive electrode material layer, a solid electrolyte layer, a negative electrode material layer, and a negative electrode current collector layer are laminated. A plurality of the power generating elements are electrically connected in parallel, is an all-solid-state battery, in the laminate, by arranging a heat absorbing sheet in at least a portion between the plurality of power generating elements, It is assumed that the heat absorption amount Q2 at the end of the stack in the stacking direction is larger than the heat absorption amount Q1 at the center of the stack in the stacking direction. [Selection diagram] Figure 1

Description

  The present application discloses an all-solid battery in which a plurality of power generation elements are stacked.

  Patent Document 1 discloses a battery module in which an endothermic material is disposed between a battery cell and a fixing member. Also, there is a technique for storing an endothermic substance in the battery as in Patent Document 2, and a technique for making the outermost current collector thickness of the laminated battery thicker than the inner current collector thickness as in Patent Document 3. Are known. In a battery as disclosed in Patent Documents 1 to 3, it is considered that an excessive temperature rise of the battery can be suppressed by heat absorption or heat conduction even when the battery is short-circuited and generates heat during a nail penetration test or the like.

JP, 2006-533022, A JP 2010-287492 A JP 2002-110170 A

  In an all-solid-state battery in which a plurality of power generation elements are stacked and electrically connected in parallel, when the power generation elements are short-circuited by a nail penetration test, electrons flow from one power generation element to another (hereinafter referred to as this). May be referred to as “sneak current”), and the problem arises that the temperature of some power generation elements rises locally. Conventionally, when a nail penetration test is performed on a stacked battery, it is expected that the effect of heat accumulation will be large. Therefore, the power generation element located at the center in the stacking direction ) Was thought to be hot.

  On the other hand, the present inventors conducted a nail penetration test for an all-solid battery electrically connected in parallel while laminating a plurality of power generation elements, particularly in the power generation elements located at both ends in the stacking direction, It has been found that the short-circuit resistance becomes small and the sneak current tends to concentrate. That is, the present inventors have found a new problem that in such a laminated all-solid battery, an excessive temperature rise is likely to occur in the power generation elements located at both ends in the lamination direction during the nail penetration test. It was.

The present application is one of the means for solving the above problems.
A plurality of power generation elements, wherein a positive electrode current collector layer, a positive electrode material layer, a solid electrolyte layer, a negative electrode material layer, and a negative electrode current collector layer are stacked; In the all-solid-state battery in which elements are electrically connected in parallel, and in the laminated body, an endothermic sheet is disposed at least at a part between the plurality of power generation elements, thereby stacking the laminated body An all-solid battery is disclosed in which the endothermic amount Q2 at the end in the stacking direction of the laminate is greater than the endothermic amount Q1 at the center in the direction.

The “stacking direction end of the stacked body” refers to a portion from the stacking direction end (stacking direction outermost side) to 20 when the total number of stacked power generation elements in the stacked body is 100. For example, in a laminate formed by laminating 66 power generation elements, 13 power generation elements from one end in the stacking direction can constitute one end in the stacking direction, and 13 power generation elements from the other end in the stacking direction are stacked. The other end in the direction can be configured.
The “lamination direction central portion of the laminate” refers to a portion of the laminate excluding the end in the lamination direction.
“The endothermic amount Q1 at the center of the laminate in the stacking direction” means the total endothermic amount (endothermic capacity) of the endothermic sheet when the endothermic sheet is arranged at the center of the stack in the stacking direction. When the endothermic sheet is not arranged at the center in the stacking direction, the endothermic amount Q1 is zero.
“The endothermic amount Q2 at the end of the laminate in the stacking direction” means the total endothermic amount (endothermic capacity) Q2a of the endothermic sheet disposed at one end of the stack in the stacking direction, and the other end of the stack in the stacking direction It means both the total endothermic amount (endothermic capacity) Q2b of the endothermic sheets arranged in the. That is, "the endothermic amount Q2 at the end in the stacking direction of the laminate is greater than the endothermic amount Q1 at the center in the stacking direction of the laminate" means that the endothermic amount Q1 at the center in the stacking direction of the stack. In addition, the endothermic amount Q2a at the one end in the stacking direction of the laminate is larger, and the endothermic amount Q2b at the other end in the stacking direction of the laminate is larger than the total endothermic amount Q1 at the center in the stacking direction of the stack. Means big.
The “endothermic amount” (J) of the endothermic sheet can be measured by a DSC apparatus. Specifically, in the DSC apparatus, from an DSC curve in the case where the endothermic sheet piece was heated from 50 ° C. to 500 ° C. in an argon atmosphere using an open pan, the heating rate was 10 ° C./min, The endothermic amount (J) of the endothermic sheet can be measured by measuring the endothermic amount (J / cm ³ ) per volume of the endothermic sheet and multiplying this by the volume of the endothermic sheet.

  In the all solid state battery of the present disclosure, the amount of heat absorption (endothermic capacity) at both ends in the stacking direction is larger than the center portion in the stacking direction of the stack, and efficient heat absorption is possible at both ends in the stacking direction. During the nail penetration test, an excessive temperature rise can be suppressed for the power generation elements at both ends in the stacking direction.

It is the schematic for demonstrating the layer structure of the all-solid-state battery 100 (100a). 3 is a schematic diagram for explaining a layer configuration of a power generation element 20. FIG. (A) is an external perspective view, (B) is a IIB-IIB sectional view. It is the schematic for demonstrating the layer structure of the all-solid-state battery 100 (100b). It is the schematic for demonstrating the layer structure etc. of the all-solid-state battery for evaluation. It is a figure which shows the result normalized about the electric current which flows into each electric power generation element of an all-solid-state battery at the time of a nail penetration test.

1. All solid state battery 100
FIG. 1 schematically shows the layer structure of the all-solid battery 100 (100a). In FIG. 1, for convenience of explanation, a connection portion between current collector layers or current collector tabs, a battery case, and the like are omitted. FIG. 2 schematically shows the layer configuration of the power generation element 20 constituting the all-solid battery 100. 2A is an external perspective view, and FIG. 2B is a IIB-IIB sectional view.

  As shown in FIGS. 1 and 2, the all-solid-state battery 100 includes a stacked body 50 in which a plurality of power generation elements 20 (20 a and 20 b) are stacked, and in the power generation element 20, a positive electrode current collector layer 21 and a positive electrode material layer. 22, the solid electrolyte layer 23, the negative electrode material layer 24, and the negative electrode current collector layer 25 are laminated, and the plurality of power generation elements 20, 20... Are electrically connected in parallel. Here, in the laminated body 50, the endothermic sheet 10 (10a, 10b) is disposed at least at a part between the plurality of power generation elements 20, 20,. In the all-solid-state battery 100, the endothermic sheet 10 makes the endothermic amount Q2 at the end in the stacking direction of the stacked body 50 larger than the endothermic amount Q1 at the center in the stacking direction of the stacked body 50. There are features.

1.1. Endothermic sheet 10
The heat absorbing sheet 10 absorbs heat when the power generation element 20 generates heat. The endothermic sheet 10 can be made of an endothermic material. Examples of the endothermic material include sugar alcohols such as mannitol and xylitol, hydrocarbons such as anthracene, inorganic hydrates such as gypsum, zirconium sulfate and tetrahydrate, and mixtures thereof. Of these, sugar alcohols and hydrocarbons are preferred. (I) a material that absorbs heat by melting, (II) can be plastically deformed and can be easily layered, and (III) a product (such as water) that degrades the battery material at the battery operating temperature or endothermic temperature. ) Is not released. In particular, sugar alcohol is preferred. This is because it is easy to ensure a large amount of heat absorption.

  The size and thickness of the endothermic sheet 10 are not particularly limited. As will be described later, the size and thickness of the endothermic sheet 10 so that the endothermic amount Q2 at the end in the stacking direction of the stacked body 50 is larger than the endothermic amount Q1 at the center in the stacking direction of the stacked body 50. Furthermore, the material may be determined.

1.2. Power generation element 20
The power generation element 20 is formed by laminating a positive electrode current collector layer 21, a positive electrode material layer 22, a solid electrolyte layer 23, a negative electrode material layer 24, and a negative electrode current collector layer 25. That is, the power generation element 20 can function as a unit cell. In FIGS. 1 and 2, two power generation elements 20 a and 20 b share one negative electrode current collector layer 25.

1.2.1. Positive electrode current collector layer 21
The positive electrode current collector layer 21 may be made of a metal foil, a metal mesh, or the like. Metal foil is particularly preferable. Examples of the metal constituting the positive electrode current collector layer 21 include Ni, Cr, Au, Pt, Al, Fe, Ti, Zn, and stainless steel. The positive electrode current collector layer 21 may have some coat layer for adjusting contact resistance on the surface thereof. The thickness of the positive electrode current collector layer 21 is not particularly limited. For example, it is preferably 0.1 μm or more and 1 mm or less, and more preferably 1 μm or more and 100 μm or less.

  As shown in FIG. 2, the positive electrode current collector layer 21 preferably includes a positive electrode current collector tab 21 a at a part of the outer edge. The tab 21a allows the first current collector layer 11 and the positive electrode current collector layer 21 to be easily electrically connected, and the positive electrode current collector layers 21 are easily electrically connected in parallel. be able to.

1.2.2. Positive electrode material layer 22
The positive electrode material layer 22 is a layer that includes at least an active material, and optionally further includes a solid electrolyte, a binder, a conductive additive, and the like. A known active material may be used as the active material. Of the known active materials, two materials having different potentials for storing and releasing predetermined ions (charge / discharge potentials) 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. Each can be used as a negative electrode active material. For example, in the case of constituting a lithium ion battery, various positive electrode active materials such as lithium cobaltate, lithium nickelate, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , lithium manganate, spinel lithium compound, etc. A lithium-containing composite oxide can be used. The surface of the positive electrode active material may be coated with an oxide layer such as a lithium niobate layer, a lithium titanate layer, or a lithium phosphate layer. 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. Furthermore, as compared with the organic polymer electrolyte, the pressure applied to the power generation element 20 at the time of nail penetration is high, and the effect of the all-solid battery 100 of the present disclosure becomes remarkable. Examples thereof include oxide solid electrolytes such as lithium lanthanum zirconate and sulfide solid electrolytes such as Li ₂ S—P ₂ S ₅ . In particular, a sulfide solid electrolyte containing Li ₂ S—P ₂ S ₅ is preferable, and a sulfide solid electrolyte containing 50 mol% or more of Li ₂ S—P ₂ S ₅ is more preferable. As the binder, various binders such as butadiene rubber (BR), acrylate butadiene rubber (ABR), and polyvinylidene fluoride (PVdF) 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 material layer 22 may be the same as the conventional one. The shape of the positive electrode material layer 22 may be the same as the conventional one. In particular, the sheet-like positive electrode material layer 22 is preferable from the viewpoint that the laminated battery 100 can be easily configured. In this case, the thickness of the positive electrode material layer 22 is, for example, preferably from 0.1 μm to 1 mm, and more preferably from 1 μm to 150 μm.

1.2.3. Solid electrolyte layer 23
The electrolyte layer 23 is a layer containing a solid electrolyte and optionally a binder. The solid electrolyte is preferably the inorganic solid electrolyte described above. A binder similar to the binder used for the positive electrode material layer 22 can be appropriately selected and used. What is necessary is just to make content of each component in the solid electrolyte layer 23 the same as the past. The shape of the solid electrolyte layer 23 may be the same as the conventional one. In particular, the sheet-like solid electrolyte layer 23 is preferable from the viewpoint that the laminated battery 100 can be easily configured. In this case, the thickness of the solid electrolyte layer 23 is, for example, preferably 0.1 μm or more and 1 mm or less, and more preferably 1 μm or more and 100 μm or less.

1.2.4. Negative electrode material layer 24
The negative electrode material layer 24 is a layer that includes at least an active material, and optionally further includes a solid electrolyte, a binder, a conductive additive, and the like. A known active material may be used as the active material. Among the known active materials, two materials having different potentials for storing and releasing predetermined ions (charge / discharge potentials) are selected, and a material exhibiting a noble potential is used as the positive electrode active material described above, and a material exhibiting a base potential is selected. Each can be used as a negative electrode active material. For example, when configuring a lithium ion battery, a carbon material such as graphite or hard carbon, various oxides such as lithium titanate, Si or Si alloy, or metallic lithium or lithium alloy may be used as the negative electrode active material. it can. In particular, Si and Si alloy are preferable, and Si is more preferable. This is because the variation of the short-circuit resistance of each of the power generation elements 20, 20,... Tends to increase more easily during the nail penetration, and the effect of the endothermic sheet 10 becomes greater. As the solid electrolyte, the binder, and the conductive additive, those similar to the solid electrolyte used for the positive electrode material layer 22 can be appropriately selected and used. The content of each component in the negative electrode material layer 24 may be the same as the conventional one. The shape of the negative electrode material layer 24 may be the same as the conventional one. In particular, the sheet-like negative electrode material layer 24 is preferable from the viewpoint that the all-solid battery 100 can be easily configured. In this case, the thickness of the negative electrode material layer 24 is, for example, preferably from 0.1 μm to 1 mm, and more preferably from 1 μm to 100 μm. However, it is preferable to determine the thickness of the negative electrode material layer 24 so that the capacity of the negative electrode is larger than the capacity of the positive electrode.

1.2.5. Negative electrode current collector layer 25
The negative electrode current collector layer 25 may be composed of a metal foil, a metal mesh, or the like. Metal foil is particularly preferable. Examples of the metal constituting the negative electrode current collector layer 25 include Cu, Ni, Fe, Ti, Co, Zn, and stainless steel. The negative electrode current collector layer 25 may have some coat layer for adjusting contact resistance on the surface thereof. The thickness of the negative electrode current collector layer 25 is not particularly limited. The thickness of the negative electrode current collector 25 is not particularly limited. For example, it is preferably 0.1 μm or more and 1 mm or less, and more preferably 1 μm or more and 100 μm or less.

  As shown in FIG. 2, the negative electrode current collector layer 25 preferably includes a negative electrode current collector tab 25a at a part of the outer edge. The tab 25a allows the second current collector layer 12 and the negative electrode current collector layer 25 to be easily electrically connected, and the negative electrode current collector layers 25 to be easily electrically connected in parallel. be able to.

1.3. Arrangement and connection form of endothermic sheet and power generation element 1.3.1. Arrangement of Power Generation Elements In the all-solid-state battery 100, the number of stacked power generation elements 20 is not particularly limited, and may be appropriately determined according to the output of the target battery. Usually, the number of stacked power generation elements (unit cells) is 10 or more. In particular, the number of stacked power generating elements (unit cells) is preferably 20 or more and 100 or less. The lower limit is more preferably 30 or more, and the upper limit is more preferably 80 or less. In this case, the plurality of power generation elements 20 may be stacked so as to be in direct contact with each other, or the plurality of power generation elements 20 may be stacked via some layer (for example, an insulating layer) or an interval (air layer). Good. However, as described above, the heat absorbing sheet 10 needs to be disposed at least at a part between the plurality of power generation elements 20. From the viewpoint of improving the output density of the battery, as shown in FIG. 1, it is preferable that a plurality of power generation elements 20 are laminated so as to be in direct contact with each other, excluding the heat absorbing sheet 10. As shown in FIGS. 1 and 2, it is preferable that the two power generation elements 20 a and 20 b share the negative electrode current collector 25. By doing in this way, the output density of a battery further improves. Furthermore, as shown in FIG. 1, in the all-solid-state battery 100, it is preferable that the stacking direction of the plurality of power generation elements 20 and the stacking direction of the layers 21 to 25 in the power generation element 20 are matched. By doing in this way, restraint of the all-solid-state battery 100 becomes easy and the output density of a battery further improves.

1.3.2. Electrical connection between power generation elements In the all-solid-state battery 100, a plurality of power generation elements 20, 20, ... are electrically connected in parallel. In the power generation elements connected in parallel in this way, when one power generation element is short-circuited, electrons flow from another power generation element to the one power generation element in a concentrated manner. That is, Joule heat tends to increase when the battery is short-circuited. In other words, in the all solid state battery 100 including the plurality of power generation elements 20, 20,... Connected in parallel as described above, the effect of providing the heat absorbing sheet 10 becomes more remarkable. As a member for electrically connecting the power generation elements 20 to each other, a conventionally known member may be used. For example, as described above, the positive electrode current collector tab 21 is provided with the positive electrode current collector tab 21a, the negative electrode current collector layer 25 is provided with the negative electrode current collector tab 25a, and the power generation elements 20 are connected to each other via the tabs 21a and 25a. They can be electrically connected in parallel.

1.3.3. Positional relationship between endothermic sheet and power generation element In the all-solid-state battery 100, the endothermic sheet 10 is disposed at least in part between the power generation elements 20, 20,. In particular, in the all-solid-state battery 100 (100a) shown in FIG. 1, the endothermic sheet 10 is not disposed at the center of the stack 50 in the stacking direction, whereas the endothermic sheet 10 is disposed at the end of the stack 50 in the stacking direction. Thus, the endothermic amount Q2 at the end in the stacking direction of the stacked body 50 is greater than the endothermic amount Q1 at the center in the stacking direction of the stacked body 50 (Q2> Q1 = 0).

  Alternatively, even in the case where the endothermic sheet 10 is arranged at both the stacking direction end and the stacking direction center of the stacked body 50, the end of the stack 50 in the stacking direction is more than the endothermic amount Q1 at the stacking center of the stacked body 50. It is possible to increase the endothermic amount Q2 in the portion. For example, like the all-solid-state battery 100 (100b) shown in FIG. 3, the endothermic sheets 10a and 10b having a large endothermic amount are arranged at the end in the stacking direction of the laminate 50, while the endotherm having a small endotherm is disposed at the center in the stacking direction. The sheet 10c is disposed. In this case, the heat absorption amount of the heat absorption sheets 10a and 10b may be made larger than the heat absorption amount of the heat absorption sheet 10c by changing the thickness, size, and material of the heat absorption sheet. That is, the endothermic amount Q2a of the endothermic sheet 10a and the endothermic amount Q2b of the endothermic sheet 10b are larger than the endothermic amount Q1c of the endothermic sheet 10c (Q2a> Q1c, Q2b> Q1c).

  The heat-absorbing sheet 10 and the power generation element may be directly laminated with each other, or may be indirectly laminated with other layers (insulating layer, heat conductive layer, etc.) within a range in which the above problem can be solved. Good.

  As described above, in the all-solid-state battery 100, the endothermic sheet 10 makes the endothermic amount (endothermic capacity) at both ends in the stacking direction larger than the central portion in the stacking direction of the stacked body 50, and is efficient at both ends in the stacking direction. Therefore, an excessive temperature rise can be suppressed for the power generating elements 20 at both ends in the stacking direction during the nail penetration test.

1.4. Presumed mechanism As described above, in an all-solid battery in which a plurality of power generation elements are stacked and electrically connected in parallel, the short-circuit resistance tends to be small in the power generation elements located at both ends in the stacking direction during the nail penetration test. Excessive temperature rise is likely to occur. The inventors consider this cause as follows. That is, in the all-solid-state battery, since the restraint pressure is high, it is presumed that the current collector foil is easily wound on the upper surface of the battery by nail penetration, and a short circuit due to contact between the foils is likely to occur. In addition, it is estimated that the lower part of the battery is short-circuited due to a layer shift or the like due to being sandwiched between the load from the upper part and the restraining jig. On the other hand, it is considered that the battery central portion is pushed by the nail and deforms while the foils of the electrode body are kept parallel to each other, so that it shows high short-circuit resistance without contact.

2. Manufacturing method of all-solid-state battery The heat-absorbing sheet 10 can be comprised with various endothermic materials as mentioned above. The endothermic sheet 10 may be manufactured by forming the endothermic material into a sheet shape.

The power generation element 20 can be produced by a known method. For example, the cathode material layer 22 is formed by applying the cathode material on the surface of the cathode current collector layer 21 in a wet manner and drying, and the anode material is applied on the surface of the anode current collector layer 25 in a wet manner. Then, a negative electrode material layer 24 is formed by drying, and an electrolyte layer 23 containing a solid electrolyte or the like is transferred between the positive electrode material layer 21 and the negative electrode material layer 24, and is pressed and integrated to generate a power generation element. 20 can be produced. The pressing pressure at this time is not particularly limited, but for example, it is preferably ² ton / cm ² or more. These production procedures are merely examples, and the power generating element 20 can be produced by other procedures. For example, it is possible to form a positive electrode material layer or the like by a dry method instead of the wet method.

  The heat-absorbing sheet 10 thus produced and the plurality of power generation elements 20, 20,... Are stacked so that the heat-absorption sheet 10 is sandwiched between at least a part of the power generation elements 20, 20,. By connecting the tabs 21a of the electric current layer 21 and connecting the tabs 25a of the negative electrode current collector layer 25, a stacked body 50 in which a plurality of power generation elements 20 are electrically connected in parallel can be obtained. it can. An all-solid battery can be produced by vacuum-sealing the laminate 50 thus obtained in a battery case such as a laminate film or a stainless steel can. These manufacturing procedures are merely examples, and an all-solid-state battery can be manufactured by other procedures.

  As described above, the all-solid battery 100 of the present disclosure can be easily manufactured by applying the conventional method for manufacturing an all-solid battery.

3. Supplementary Items In the above description, two power generation elements have shown a form in which one negative electrode current collector layer is shared. However, the all-solid-state battery of the present disclosure is not limited to this form. The power generation element may be any element as long as it functions as a unit cell, and it is sufficient that the positive electrode current collector layer, the positive electrode material layer, the electrolyte layer, the negative electrode material layer, and the negative electrode current collector layer are laminated.

  In the above description, the current collecting tab protrudes from the power generation element. However, the current collecting tab may not be provided in the all solid state battery of the present disclosure. For example, a current collector layer having a large area is used, and the outer edges of a plurality of current collector layers are projected in the laminate, and a tab is provided by sandwiching a conductive material between the projected current collector layers. At least, the current collector layers can be electrically connected to each other. Or you may electrically connect collector layers not with a tab but with conducting wires.

  The technology of the present disclosure solves the problems that occur peculiarly in all solid state batteries. In the case of an electrolyte battery, the pressure applied to the power generation element when pressure is applied is low because of liquid fluidity, but in the case of an all-solid battery, the pressure is applied to the power generation element as it is without flowing the solid electrolyte when pressure is applied. When a nail penetrates the power generation element during nail penetration, the pressure applied to the power generation element is high. Therefore, in the all-solid-state battery, for example, the positive electrode current collector and the negative electrode current collector of the power generation element are in contact with each other at a strong pressure (or with a large contact area) at the time of nail penetration, and those that do not contact are mixed, The short circuit resistance of some power generation elements is smaller than the short circuit resistance of other power generation elements (that is, the short circuit resistance varies), and a large amount of sneak current flows into some power generation elements having a short circuit resistance. It is considered to be. Furthermore, in an all-solid-state battery, a binding pressure may be applied to the power generation element in order to reduce internal resistance in the power generation element. In this case, a binding pressure is applied in the stacking direction of the power generating elements (the direction in which the positive electrode current collector layer faces the negative electrode current collector layer), and when the nail is inserted, the positive electrode current collector layer, the negative electrode current collector layer, Is likely to contact and short-circuit, and the short-circuit resistance of the power generation element is likely to be small. Therefore, during the nail penetration test, the Joule heat generation of the power generation element is considered to be larger, and the effect of providing the heat absorption sheet to absorb the heat of the power generation element is considered to be more remarkable. On the other hand, in an electrolytic solution battery, the inside of a battery case is usually filled with an electrolytic solution, each layer is immersed in the electrolytic solution, and the electrolytic solution is supplied to the gap between the layers. In the electrolyte battery, the pressure applied by the nail at the time of nail penetration is smaller than that of an all-solid battery. In other words, in an electrolyte battery, the short-circuit resistance is less likely to vary during nail penetration, and the short-circuit resistance of the power generation element at the stacking direction end during nail penetration is the short-circuit resistance of the power generation element at the center of the stacking direction. It may not be smaller than.

  When the power generation elements are electrically connected in series via the bipolar electrode, if some of the power generation elements are pierced with a nail, the other power generation elements wrap around the power generation element via the nail. It is considered that current flows. That is, it goes around through a nail having a high contact resistance, and its current amount is small. In addition, when the power generation elements are electrically connected in series via the bipolar electrode, it is considered that the sneak current is maximized when the nail is pierced by all of the power generation elements. Is already sufficiently advanced, and it is unlikely that the temperature of some power generation elements will rise locally. In this respect, it is considered that the effect of arranging the heat absorbing sheet is small compared to the case where the power generation elements are electrically connected in parallel. Therefore, it can be said that the technique of the present disclosure exhibits a particularly remarkable effect in a battery in which power generation elements are electrically connected in parallel.

1. Production of all-solid-state battery (production of positive electrode active material)
LiNbO ₃ is coated on Li _1.15 Ni _1/3 Co _1/3 Mn _1/3 W _0.005 O ₂ particles in an atmospheric environment using a rolling fluid coating apparatus (manufactured by POWREC) in an atmospheric environment. To obtain a positive electrode active material.

(Preparation of positive electrode material layer)
In a polypropylene container, butyl butyrate, a 5 wt% butyl butyrate solution of a PVDF binder (manufactured by Kureha), the positive electrode active material, and a sulfide solid electrolyte (Li ₂ S containing an average particle size of 0.8 μm, LiI, LiBr) -P ₂ S ₅ -based glass ceramic) was added, further VGCF the (Showa Denko KK) was added as a conductive additive, and stirred for 30 seconds with an ultrasonic dispersing device (manufactured by SMT Co., Ltd. UH-50). Next, the container was shaken with a shaker (TTM-1 manufactured by Shibata Kagaku Co., Ltd.) for 3 minutes, and then stirred for 30 seconds with an ultrasonic dispersion apparatus. Furthermore, after shaking for 3 minutes with a shaker, the obtained paste was applied onto an aluminum foil (manufactured by Nihon Foil Co., Ltd.) by a blade method using an applicator. After natural drying, the positive electrode material layer was formed on the aluminum foil (positive electrode current collector layer) by drying on a hot plate at 100 ° C. for 30 minutes.

(Preparation of negative electrode material layer)
In a polypropylene container, butyl butyrate, a 5 wt% butyl butyrate solution of PVDF binder (manufactured by Kureha), silicon having an average particle size of 5 μm as a negative electrode active material (single Si, manufactured by Kojundo Chemical Co., Ltd.), and sulfide solid An electrolyte (Li ₂ S—P ₂ S ₅ glass ceramic containing an average particle size of 0.8 μm, LiI, and LiBr) was added, and the mixture was stirred for 30 seconds with an ultrasonic dispersion device (UH-50 manufactured by SMT). Next, the container was shaken with a shaker (TTM-1 manufactured by Shibata Kagaku Co., Ltd.) for 30 minutes, and then stirred for 30 seconds with an ultrasonic dispersion apparatus. Furthermore, after shaking for 3 minutes with a shaker, the obtained paste was applied onto a copper foil by a blade method using an applicator. After natural drying, the negative electrode material layer was formed on both surfaces of the copper foil (negative electrode current collector layer) by drying on a hot plate at 100 ° C. for 30 minutes.

(Preparation of solid electrolyte layer)
Li ₂ SP—P ₂ S ₅ glass containing 5 wt% heptane solution of heptane, BR binder (manufactured by JSR) and sulfide solid electrolyte (average particle size 2.5 μm, LiI, LiBr in a polypropylene container Ceramic) was added, and the mixture was stirred for 30 seconds with an ultrasonic dispersion apparatus (UH-50 manufactured by SMT). Next, the container was shaken with a shaker (TTM-1 manufactured by Shibata Kagaku Co., Ltd.) for 30 minutes, and then stirred for 30 seconds with an ultrasonic dispersion apparatus. Furthermore, after shaking for 3 minutes with a shaker, the obtained paste was applied onto an aluminum foil by a blade method using an applicator. After natural drying, the solid electrolyte layer was formed on the aluminum foil (base material) by drying on a hot plate at 100 ° C. for 30 minutes.

(Production of power generation elements)
After each layer was cut into a battery shape, a solid electrolyte layer was superimposed on both surfaces of the negative electrode material layer, and pressed by applying a pressure corresponding to 4 ton / cm ^{2 with} CIP (manufactured by Kobe Steel). Thereafter, the aluminum foil is peeled off from the surface of the solid electrolyte layer, and the positive electrode material layer is superposed on the aluminum foil and pressed by applying a pressure equivalent to 4 ton / cm ² , and the aluminum foil (positive electrode current collector layer) / positive electrode material layer is applied. A power generation element having a nine-layer structure of: / solid electrolyte layer / negative electrode material layer / copper foil (negative electrode current collector layer) / negative electrode material layer / solid electrolyte layer / positive electrode material layer / aluminum foil (positive electrode current collector layer) Two power generation elements share one negative electrode current collector layer).

(Lamination with power generation elements)
As shown in FIG. 4, 66 power generation elements are stacked and the current collection tabs are ultrasonically welded to each other to join the first current collector layer of the short-circuit current dispersion and the positive current collection of the power generation elements. The body layer was electrically connected, placed in a laminate pack, and the laminate unsealed portion was sealed by heat welding while evacuating to obtain an all-solid battery for evaluation. Here, a measuring instrument is connected to each current collecting tab so that the short-circuit resistances R _{1 to} R _{66 of} each power generation element and the currents I _{1 to} I ₆₆ flowing through each power generation element can be measured.

2. Evaluation by nail penetration test The produced all-solid-state battery was charged from 0 V to 4.55 V, discharged from 4.55 V to 3 V, and further charged to 4.35 V. After charging, as shown in FIG. 4, a nail (φ8 mm, tip angle 60 degrees, SK material) is inserted into the all-solid-state battery at a speed of 25 mm / sec. R _{1 to} R ₆₆ and currents I _{1 to} I ₆₆ flowing through the power generation elements were measured.

In the evaluation, the power generation elements 1 to 11 of the 1st to 11th layers, the power generation elements 12 to 22 of the 12th to 22nd layers, the power generation elements 23 to 33 of the 23rd to 33rd layers, and the power generation of the 34th to 44th layers For each of the elements 34 to 44, the power generation elements 45 to 55 in the 45th to 55th layers, and the power generation elements 56 to 66 in the 56th to 66th layers, the minimum short-circuit resistance of each power generation element and the maximum flowing to each power generation element The current was identified. The results are shown in Table 1 below and FIG. In Table 1 and FIG. 5, the minimum short-circuit resistance (minimum short-circuit resistance among R _{1 to} R ₁₁ ) in the power generation elements 1 to 11 in the _{1st to 11th} layers is 1.0, and the power generation in the _{1st to 11th} layers is performed. The maximum current in elements 1 to 11 (maximum current among I _{1 to} I ₁₁ ) was normalized as 100.

  As is clear from the results shown in Table 1 and FIG. 5, in the stacked all solid state battery, the short-circuit resistance of the power generation element at the end in the stacking direction is smaller than the short-circuit resistance of the power generation element at the center in the stacking direction. It was found that a large current flows into the power generation element at the end in the stacking direction. That is, it was found that Joule heat generation of the power generation element tends to occur at the end in the stacking direction. On the other hand, an endothermic sheet is arranged at the end in the stacking direction to increase the amount of heat absorption (endothermic capacity) at both ends in the stacking direction compared to the central portion in the stacking direction and efficiently absorb heat at both ends in the stacking direction. Thus, it is considered that an excessive temperature rise can be suppressed for the power generation elements at both ends in the stacking direction during the nail penetration test.

  The all-solid-state battery according to the present invention can be suitably used as, for example, a large-sized power source for mounting on a vehicle.

10a to 10c Endothermic sheet 20 Power generation element 21 Positive electrode current collector layer 21a Positive electrode current collector tab 22 Positive electrode material layer 23 Solid electrolyte layer 24 Negative electrode material layer 25 Negative electrode current collector layer 25a Negative electrode current collector tab 50 Laminate 100 All solid state battery

Claims (1)

A plurality of power generation elements, wherein a positive electrode current collector layer, a positive electrode material layer, a solid electrolyte layer, a negative electrode material layer, and a negative electrode current collector layer are stacked; An all-solid battery in which elements are electrically connected in parallel,
In the laminate, an endothermic sheet is disposed at least at a part between the plurality of power generation elements, so that the endothermic amount Q1 in the center in the stacking direction of the stack is higher than the end in the stacking direction of the stack. The endothermic amount Q2 is assumed to be larger.
All solid battery.