JP7655285B2 - Bipolar battery module - Google Patents

Description

The present invention relates to a bipolar battery module.

A bipolar battery module is a battery module in which two or more unit cells are stacked in series. Such bipolar battery modules have attracted attention because it is relatively easy to increase voltage, reduce the number of parts, reduce electrical resistance between unit cells, and increase energy density by eliminating unnecessary space.

In bipolar battery modules, a problem may occur in which two or more unit cells stacked in series become misaligned during manufacture or use. To prevent such problems, it is known to stack the unit cells together via an adhesive layer.

In response to this, Patent Documents 1 and 2 propose stacking unit cells together via an adhesive resin layer having through-holes.

Patent Documents 3 and 4 propose an adhesive sheet that uses intermolecular forces to bond or hold articles and/or materials, specifically, an adhesive sheet that has a sheet-like substrate and a number of nanofibers fixed to the substrate, and that adheres and holds an adherend to the surface of the nanofibers by intermolecular forces acting between the adherend and the nanofibers that are in contact with the nanofibers.

JP 2017-073374 A JP 2020-109762 A Special Publication No. 2006-526059 JP 2010-031193 A

When unit cells are laminated together via an adhesive resin layer having through holes as in Patent Documents 1 and 2, the thickness of the adhesive resin layer can make it difficult to achieve electrical contact between the unit cells at the through holes.

In addition, when unit cells are stacked together via an adhesive resin layer having through holes, the adhesive resin layer is disposed even on the periphery of the unit cells. Therefore, when replacing only some of the unit cells that have poor performance during the manufacturing stage or in the market, it may be difficult to peel off the unit cells without damaging them. In particular, unit cells with large electrode areas are prone to deformation, such as bending, when peeled off, and therefore the unit cells are prone to damage.

Therefore, the present invention provides a bipolar battery module that solves the above problems.

After extensive research, the inventors discovered that the above problems could be solved by the following means, and completed the present invention. That is, the present invention is as follows.

<Aspect 1>
A bipolar battery module in which two or more unit cells are stacked in series,
the unit cell is a laminate of a positive electrode layer, an electrolyte layer, and a negative electrode layer, and the unit cell has, in a planar direction, a peripheral region and a central region that is a region other than the peripheral region,
Either one of the following (i) or (ii) is satisfied:
(i) an anode layer of a first unit cell among the two or more unit cells and a cathode layer of a second unit cell among the two or more unit cells are bonded to each other in the central region via a first adhesive layer and are in electrical contact with each other in the peripheral region; and (ii) a conductive material layer is disposed between the anode layer of the first unit cell and the cathode layer of the second unit cell, the anode layer of the first unit cell and the conductive material layer are bonded to each other in the central region via a second adhesive layer and are in electrical contact with each other in the peripheral region, and the conductive material layer and the cathode layer of the second unit cell are bonded to each other in the central region via a third adhesive layer and are in electrical contact with each other in the peripheral region.
Bipolar battery module.
<Aspect 2>
The bipolar battery module according to aspect 1, which satisfies (i).
Aspect 3
The bipolar battery module according to claim 1, which satisfies (ii).
<Aspect 4>
Satisfies the above (ii),
the conductive member layer has a thick portion in contact with the peripheral region, and the conductive member layer is a conductive cooling member layer having a coolant flow path through which a coolant flows.
A bipolar battery module according to aspect 3.
<Aspect 5>
A bipolar battery module according to any one of Aspects 1 to 4, wherein the adhesive layer is an adhesive sheet having a sheet-like substrate and a plurality of nanofibers fixed to the sheet-like substrate, and adhesively holds the adherend in contact with the nanofibers on a surface of the nanofibers by intermolecular forces acting between the adherend and the nanofibers.

According to the bipolar battery module of the present invention, the adhesive layer in the central region suppresses misalignment between the unit cells, while the sagging (i.e., distortion or deformation) of the unit cells in the peripheral region can be utilized to improve electrical contact between the unit cells. In addition, according to the bipolar battery module of the present invention, the adhesive layer is provided only in the central region, rather than on the entire surface or the peripheral region, so that when replacing only some of the unit cells among a plurality of unit cells, it is relatively easy to peel off the adhesive layer without damaging the unit cells.

FIG. 1 is a schematic cross-sectional side view showing a stacked structure of a bipolar battery module according to (a) a first embodiment of the present invention, and (b) a second embodiment of the present invention. FIG. 2 is a schematic cross-sectional side view showing a stacking structure of adjacent unit cells of a bipolar battery module according to (a) a first embodiment of the present invention, (b) a second embodiment of the present invention, (c) a modified embodiment of the second embodiment of the present invention, and (d) an embodiment other than the present invention. FIG. 3 is a schematic cross-sectional top view showing adhesive layers of a bipolar battery module according to (a) the present invention and (b) other than the present invention. FIG. 4 is a schematic side cross-sectional view showing a stacked structure of unit cells that can be used in the bipolar battery module of the present invention.

The bipolar battery module of the present invention is a bipolar battery module in which two or more unit cells are stacked in series. This unit cell is a laminate of a positive electrode layer, an electrolyte layer, and a negative electrode layer, and has a peripheral region and a central region other than the peripheral region in the planar direction. Here, the "planar direction" means the direction perpendicular to the stacking direction of the positive electrode layer, electrolyte layer, and negative electrode layer of the unit cell, i.e., the direction in which each layer of the unit cell extends.

In addition, the bipolar battery module of the present invention satisfies either one of the following (i) and (ii):
(i) an anode layer of a first unit cell among the two or more unit cells and a cathode layer of a second unit cell among the two or more unit cells are bonded to each other in a central region via a first adhesive layer and are in electrical contact with each other in a peripheral region; and (ii) a conductive member layer is disposed between the anode layer of the first unit cell and the cathode layer of the second unit cell, the anode layer and the conductive member layer of the first unit cell are bonded to each other in the central region via a second adhesive layer and are in electrical contact with each other in the peripheral region, and the conductive member layer and the cathode layer of the second unit cell are bonded to each other in the central region via a third adhesive layer and are in electrical contact with each other in the peripheral region.

In the unit cell, the peripheral region may be at least 3 cm, at least 5 cm, at least 7 cm, at least 10 cm, at least 15 cm, at least 20 cm, or at least 25 cm from the peripheral edge of the unit cell in the planar direction. In addition, in the unit cell, the central region means a region other than the peripheral region, and may be, for example, 1% or more, 1% or more, 3% or more, 5% or more, 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, or 50% or more of the area of the unit cell in the planar direction, or 80% or less, 75% or less, 70% or less, 65% or less, 60% or less, 55% or less, 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, or 10% or less.

In order to promote adhesion between adjacent unit cells or between adjacent unit cells and the conductive member layer, it is preferable that the central area where the adhesive layer is provided is relatively large. On the other hand, in order to promote electrical contact between adjacent unit cells or between adjacent unit cells and the conductive member layer, and peeling of the adhesive layer for replacing only some of the unit cells among the multiple unit cells, it is preferable that the central area where the adhesive layer is provided is relatively small.

(Adhesive Layer)
The adhesive layer used in the bipolar battery module of the present invention may be any adhesive layer capable of bonding adjacent unit cells or adjacent unit cells and a conductive material layer. Therefore, the adhesive layer may be a conductive adhesive layer or an insulating adhesive layer. However, according to the bipolar battery module of the present invention, even when an insulating adhesive layer is used, electrical contact between adjacent unit cells or between adjacent unit cells and a conductive material layer can be promoted.

The average thickness of the adhesive layer may be 1 mm or less, 800 μm or less, 600 μm or less, 400 μm or less, 200 μm or less, 100 μm or less, 50 μm or less, 30 μm or less, 15 μm or less, 10 μm or less, 8 μm or less, or 5 μm or less, from the viewpoint of effective electrical contact between adjacent unit cells or between adjacent unit cells and the conductive material layer in the peripheral region. The average thickness of the adhesive layer may be 0.5 μm or more, 1 μm or more, 3 μm or more, 5 μm or more, 10 μm or more, 50 μm or more, 100 μm or more, 300 μm or more, or 500 μm or more, from the viewpoint of the ease of handling the adhesive layer and effective adhesion between adjacent unit cells or between adjacent unit cells and the conductive material layer.

Specifically, an example of an insulating adhesive layer is an adhesive resin layer. Any resin that exhibits adhesiveness or tackiness can be used as the adhesive resin for such an adhesive resin layer. Specifically, such adhesive resins include acrylic thermoplastic resins, methacrylic thermoplastic resins, silicone resins, urethane resins, polyvinyl ether, rubber, etc.

In order to reduce the average thickness while improving the ease of handling, the adhesive layer may be configured to include a sheet-like substrate and an adhesive resin provided on one or both sides of the substrate. In this case, the substrate may be a film, a woven fabric, a nonwoven fabric, a mesh cloth, a porous membrane, an expanded sheet, a punched sheet, or the like. The material constituting the substrate may be a resin material such as nylon or polyethylene terephthalate (PET); or a natural fiber such as hemp, wood pulp, or cotton linter.

The conductive adhesive layer may be the insulating adhesive layer described above, for example, an adhesive layer in which conductive particles are dispersed in an adhesive resin layer. The conductive particles that can be used here are not particularly limited as long as they are fine particles having conductivity, and examples include metal particles such as gold, silver, platinum, zinc, stainless steel, nickel, copper, cobalt, molybdenum, antimony, iron, and chromium; alloy particles such as aluminum-magnesium alloys and aluminum-nickel alloys, metal oxide particles such as tin oxide and indium oxide; metal particles such as nickel coated with precious metals such as gold, silver, and platinum; non-conductive particles such as glass, ceramic, and plastic coated with precious metals such as gold, silver, and platinum; graphites such as natural graphite and artificial graphite, and carbon particles such as carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black.

However, in the bipolar battery module of the present invention, electrical contact between adjacent unit cells or electrical contact between adjacent unit cells and the conductive material layer is achieved in the peripheral region where no adhesive layer is present, so the adhesive layer does not need to be conductive. In addition, in terms of adhesion, it is preferable that the adhesive layer does not contain conductive particles.

As the adhesive layer, an adhesive sheet using intermolecular forces can be used, specifically, an adhesive sheet having a sheet-like substrate and a plurality of nanofibers fixed to the substrate, which adheres and holds the adherend on the surface of the nanofiber by the intermolecular forces acting between the adherend and the nanofibers in contact with the nanofibers. Since such an adhesive sheet using intermolecular forces has an adhesive force of intermolecular forces, it has the property of being difficult to peel off in the horizontal direction and easy to peel off in the vertical direction. Therefore, such an adhesive sheet using intermolecular forces can be adhered to the adherend by sliding it in the surface direction of the sheet and pressing it against the adherend, and can be detached from the adherend by sliding it in the surface direction of the sheet. For details of the adhesive sheet using intermolecular forces, refer to Patent Documents 3 and 4.

Therefore, by using such an adhesive sheet that utilizes intermolecular forces as the adhesive layer of the bipolar battery module of the present invention, when a defect is found in one or more unit cells or conductive material layers after bonding the unit cells together or the unit cells and the conductive material layers, it is possible to detach the unit cells from each other or the unit cells and the conductive material layers and replace only the defective unit cells or conductive material layers.

(others)
The bipolar battery module of the present invention can be manufactured by stacking unit cells together with an adhesive layer and an optional conductive material layer, and external electrodes for inputting and outputting electric power to and from the outside can be formed on both end surfaces of the bipolar battery module. The bipolar battery module of the present invention may be housed inside an exterior body. Any known exterior body for batteries can be used as the exterior body.

First Aspect
In the first embodiment of the bipolar battery module of the present invention which satisfies the above-mentioned (i), that is, for example as shown in FIG. 1( a ), in a bipolar battery module 100 in which two or more unit cells 11, 12, 13 are stacked in series via adhesive layers 21 a, 21 b, 21 c, 21 d, the negative electrode layer of the first unit cell 11 and the positive electrode layer of the second unit cell 12 are joined to each other in a central region 91 via the first adhesive layer 21 b and are in electrical contact with each other in a peripheral region 81, the adhesive layer 21 a in the central region 91 can suppress misalignment between the unit cells 11, 12.

In this case, electrical contact can be made between the unit cells 11 and 12 in the peripheral region 81. Here, the electrical contact 51 in the peripheral region 81 can be made reliably by utilizing the sagging of the unit cells in the peripheral region 81, as shown in FIG. 2(a). In contrast, as shown in FIG. 2(d), when a through hole is provided in the central region of the adhesive layer 25 and electrical contact is made between adjacent unit cells 11 and 12 through the through hole 25, good electrical contact between adjacent unit cells may not be made depending on the thickness of the adhesive layer.

Figure 3(a) is a top cross-sectional view of the case where an adhesive layer 21 is disposed in the central region to bond adjacent unit cells 12 as shown in Figure 2(a) and adjacent unit cells 12 are electrically contacted to each other in the peripheral region other than the central region. Figure 3(b) is a top cross-sectional view of the case where an adhesive layer 25 having a through hole is disposed in the central region to bond adjacent unit cells 12 as shown in Figure 2(d) and adjacent unit cells 12 are electrically contacted to each other in the central region.

Second Aspect
In the second embodiment of the bipolar battery module of the present invention, which satisfies the above (ii), that is, for example, as shown in FIG. 1(b), in a bipolar battery module 100 in which two or more unit cells 11, 12, 13 are stacked in series with adhesive layers 23a, 22b, 23b, 22c, 23c, 24d interposed therebetween, a conductive member layer 31a is disposed between the negative electrode layer of the first unit cell 11 and the positive electrode layer of the second unit cell 12, and the conductive member layer 31a is electrically connected to the negative electrode layer of the first unit cell 11. In an embodiment in which the conductive member layer 31 a and the positive electrode layer of the second unit cell 12 are joined to each other in the central region 92 via the second adhesive layer 22 b and are in electrical contact with each other in the peripheral region 82, and the conductive member layer 31 a and the positive electrode layer of the second unit cell 12 are joined to each other in the central region 92 via the third adhesive layer 23 b and are in electrical contact with each other in the peripheral region 82, the adhesive layers 22 b, 23 b in the central region 92 can suppress misalignment between the unit cells 11, 12.

In this case, electrical contact can be made between the unit cells 11 and 12 in the peripheral region 82. Here, the electrical contact 52 in the peripheral region 82 can be reliably made by utilizing the sagging of the unit cells in the peripheral region 82, as shown in FIG. 2(b).

Also, as shown in FIG. 2(c), for example, the conductive member layer 32 used in this embodiment can have a thickened portion 32a that contacts the peripheral regions of the unit cells 11 and 12. When the conductive member layer has such a thickened portion, the contact 53 between the peripheral regions of the unit cells and the conductive member layer can be improved.

This thick portion is a portion thicker than the conductive member layer at a position where the adhesive layer is disposed in contact with the central region of the unit cell. The thickness of this thick portion may be a portion having an additional thickness compared to the thickness of the conductive member layer at a position where the adhesive layer is disposed in contact with the central region of the unit cell. This additional thickness may be a thickness that compensates for the thickness of the adhesive layer. Therefore, this additional thickness may be 30% or more, 40% or more, 60% or more, 80% or more, 100% or more, 120% or more, 140% or more, or 160% or more of the average thickness of the adhesive layer, and may be 200% or less, 180% or less, 160% or less, 140% or less, 120% or less, 100% or less, 80% or less, or 60% or less of the average thickness of the adhesive layer.

For example, the conductive member layer used in this embodiment may be a conductive cooling member layer having a refrigerant flow path through which a refrigerant flows. In this case, the conductive cooling member layer can be made of metals such as stainless steel or aluminum, or carbon, thereby achieving electrical contact between the unit cells while cooling the unit cells. Examples of the refrigerant include air, water, and silicone oil.

"Unit Cell"
In the present invention, the unit cell is, for example, a unit cell 10 consisting of a laminate of a positive electrode layer 10x, an electrolyte layer 10c, and a negative electrode layer 10y, as shown in Fig. 4. Here, the positive electrode layer 10x may be composed of a positive electrode current collector layer 10a and a positive electrode active material layer 10b, and the negative electrode layer 10y may be composed of a negative electrode active material layer 10d and a negative electrode current collector layer 10e. In addition, this unit cell 10 has a peripheral region 80 and a central region 90 other than the peripheral region 80 in the planar direction.

Below, we will give examples of each configuration of the unit cell when the unit cell is a lithium secondary battery, but the unit cells used in the bipolar battery module of the present invention are not limited to these configurations. Therefore, the unit cells used in the bipolar battery module of the present invention are not limited to lithium secondary batteries, and may be zinc secondary batteries, etc.

<Positive electrode layer>
The positive electrode layer includes at least a positive electrode active material. When the unit cell is charged, lithium ions move from the positive electrode active material to the negative electrode layer through the electrolyte layer. When the battery is discharged, the lithium in the negative electrode layer is ionized and returned to the positive electrode active material. The positive electrode layer may have any of the known forms for the positive electrode layer of the unit cell. For example, the positive electrode layer may include a positive electrode current collector layer and a positive electrode active material layer.

(Positive electrode current collector layer)
The positive electrode collector layer may be any of those commonly used as a positive electrode collector layer for a secondary battery. The positive electrode collector layer may be a metal foil or a metal mesh. In particular, metal foil is excellent in terms of ease of handling. The positive electrode collector layer may be made of a plurality of metal foils. Examples of metals constituting the positive electrode collector layer include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel. The thickness of the positive electrode collector layer is not particularly limited, and may be, for example, 0.1 μm or more or 1 μm or more, and may be 1 mm or less or 100 μm or less.

(Positive Electrode Active Material Layer)
The positive electrode active material layer includes a positive electrode active material, and may further include an electrolyte, a conductive assistant, a binder, etc., as desired. Furthermore, the positive electrode active material layer may include various other additives. The contents of the positive electrode active material, electrolyte, conductive assistant, binder, etc. in the positive electrode active material layer may be appropriately determined according to the intended battery performance. For example, the total (total solid content) of the positive electrode active material layer may be 100 mass%, and the content of the positive electrode active material may be 40 mass% or more, 50 mass% or more, or 60 mass% or more, or may be less than 100 mass% or 90 mass% or less. The shape of the positive electrode active material layer is not particularly limited, and may be, for example, a sheet having a substantially flat surface.

The thickness of the positive electrode active material layer is not particularly limited, and may be, for example, 0.1 μm or more, 1 μm or more, 10 μm or more, or 30 μm or more, and may be 2 mm or less, 1 mm or less, 500 μm or less, or 100 μm or less.

The positive electrode active material may be a known positive electrode active material for a secondary battery, and may be any material capable of supplying lithium to the negative electrode side during charging. For example, various lithium-containing composite oxides such as lithium cobalt oxide, lithium nickel oxide, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , lithium manganate, and spinel-based lithium compounds can be used as the positive electrode active material. Only one type of positive electrode active material may be used alone, or two or more types may be used in combination. The positive electrode active material may be, for example, particulate, and the size is not particularly limited. The particles of the positive electrode active material may be solid particles or hollow particles. The particles of the positive electrode active material may be primary particles, or may be secondary particles in which a plurality of primary particles are aggregated. The average particle size of the particles of the positive electrode active material may be, for example, 1 nm or more, 5 nm or more, or 10 nm or more, and may be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less.

The electrolyte that can be contained in the positive electrode active material layer may be a solid electrolyte, a liquid electrolyte (electrolytic solution), or a combination of these.

The solid electrolyte may be any known solid electrolyte for secondary batteries. The solid electrolyte may be an inorganic solid electrolyte or an organic polymer electrolyte. In particular, inorganic solid electrolytes have excellent ionic conductivity and heat resistance.

Examples of inorganic solid electrolytes include oxide solid electrolytes such as lithium lanthanum zirconate, LiPON, Li _1+X Al _X Ge _2-X (PO ₄ ) ₃ , Li-SiO-based glass, and Li-Al-S-O-based glass; Li ₂ S-P ₂ S ₅ , Li ₂ S-SiS ₂ , LiI-Li ₂ S-SiS ₂ , LiI-Si ₂ S-P ₂ S ₅ , Li ₂ S-P ₂ S ₅ -LiI-LiBr, LiI-Li ₂ S-P ₂ S ₅ , LiI-Li ₂ S-P ₂ O ₅ , LiI-Li ₃ PO ₄ -P ₂ S ₅ , and Li ₂ S-P ₂ S ₅ -GeS. Examples of the sulfide solid electrolyte include sulfide solid electrolytes such as sulfide solid electrolyte _2. In particular, the performance of the sulfide solid electrolyte, particularly the sulfide solid electrolyte containing at least Li, S, and P as constituent elements, is high. The solid electrolyte may be amorphous or crystalline. The solid electrolyte may be, for example, particulate. Only one type of solid electrolyte may be used alone, or two or more types may be used in combination.

The electrolyte may contain, for example, lithium ions as carrier ions. The electrolyte may be, for example, a non-aqueous electrolyte. For example, an electrolyte obtained by dissolving a lithium salt in a carbonate-based solvent at a predetermined concentration may be used. Examples of carbonate-based solvents include fluoroethylene carbonate (FEC), ethylene carbonate (EC), and dimethyl carbonate (DMC). Examples of lithium salts include hexafluorophosphate.

Examples of conductive assistants that may be included in the positive electrode active material layer include carbon materials such as vapor grown carbon fiber (VGCF), acetylene black (AB), ketjen black (KB), carbon nanotubes (CNT), and carbon nanofibers (CNF); and metal materials such as nickel, aluminum, and stainless steel. The conductive assistant may be, for example, particulate or fibrous, and its size is not particularly limited. Only one type of conductive assistant may be used alone, or two or more types may be used in combination.

Examples of binders that may be included in the positive electrode active material layer include butadiene rubber (BR)-based binders, butylene rubber (IIR)-based binders, acrylate butadiene rubber (ABR)-based binders, styrene butadiene rubber (SBR)-based binders, polyvinylidene fluoride (PVdF)-based binders, polytetrafluoroethylene (PTFE)-based binders, polyimide (PI)-based binders, polyacrylic acid-based binders, and the like. Only one type of binder may be used alone, or two or more types may be used in combination.

(others)
In addition to the above configuration, the positive electrode layer may have a general configuration as a positive electrode of a secondary battery, such as a tab or a terminal. The positive electrode layer can be manufactured by applying a known method. For example, the positive electrode active material layer can be easily formed by forming a positive electrode mixture containing the above various components in a dry or wet manner. The positive electrode active material layer may be formed together with the positive electrode current collector layer, or may be formed separately from the positive electrode current collector layer.

<Electrolyte layer>
The electrolyte layer includes at least an electrolyte. The electrolyte layer may include a solid electrolyte, and may further include a binder or the like. In this case, the content of the solid electrolyte and the binder or the like in the electrolyte layer is not particularly limited. The electrolyte layer may also include various additives. The electrolyte layer may also include a liquid component together with the solid electrolyte. Alternatively, the electrolyte layer may include an electrolytic solution, and may further include a separator or the like for holding the electrolytic solution and preventing contact between the positive electrode and the negative electrode. The thickness of the electrolyte layer is not particularly limited, and may be, for example, 0.1 μm or more or 1 μm or more, and may be 2 mm or less or 1 mm or less.

The electrolyte contained in the electrolyte layer may be appropriately selected from those exemplified as electrolytes that may be contained in the positive electrode active material layer described above. The binder that may be contained in the electrolyte layer may also be appropriately selected from those exemplified as binders that may be contained in the positive electrode active material layer described above. Only one type of electrolyte or binder may be used alone, or two or more types may be used in combination. The electrolyte layer can be easily formed, for example, by dry or wet molding an electrolyte mixture containing the above-mentioned electrolyte and binder.

On the other hand, when the electrolyte layer has an electrolyte solution and a separator, the separator may be a separator that is normally used in secondary batteries. The separator may be made of a resin such as polyethylene (PE), polypropylene (PP), polyester, or polyamide. The separator may have a single layer structure or a multi-layer structure. Examples of separators with a multi-layer structure include a separator with a two-layer structure of PE/PP, or a separator with a three-layer structure of PP/PE/PP or PE/PP/PE. The separator may be made of a nonwoven fabric such as a cellulose nonwoven fabric, a resin nonwoven fabric, or a glass fiber nonwoven fabric.

<Negative electrode layer>
The negative electrode layer may be composed of only a negative electrode collector layer, or may be composed of a negative electrode active material layer and a negative electrode collector layer. When the negative electrode layer is composed of only a negative electrode collector layer, lithium ions that have moved from the positive electrode during charging receive electrons and are precipitated as metallic lithium between the electrolyte layer and the negative electrode collector layer. When the negative electrode layer is composed of a negative electrode active material layer and a negative electrode collector layer, lithium ions that have moved from the positive electrode layer during charging receive electrons and are retained in the negative electrode active material of the negative electrode active material layer. When the battery is discharged, the lithium in the negative electrode layer is ionized and returned to the positive electrode layer.

(Negative Electrode Active Material Layer)
The negative electrode active material layer includes at least a negative electrode active material, and may further include an electrolyte, a conductive assistant, a binder, and the like. Furthermore, the negative electrode active material layer may include various other additives. The contents of the negative electrode active material, electrolyte, conductive assistant, binder, and the like in the negative electrode active material layer may be appropriately determined according to the intended battery performance. For example, the total (total solid content) of the negative electrode active material layer is taken as 100 mass%, and the content of the negative electrode active material may be 40 mass% or more, 50 mass% or more, or 60 mass% or more, and may be 100 mass% or less, or 90 mass% or less. The shape of the negative electrode active material layer is not particularly limited, and may be, for example, a sheet-like negative electrode active material layer having a substantially flat surface. The thickness of the negative electrode active material layer is not particularly limited, and may be, for example, 0.1 μm or more or 1 μm or more, and may be 2 mm or less or 1 mm or less.

As the negative electrode active material, various materials may be used that have a potential (charge/discharge potential) for absorbing and releasing lithium ions that is lower than the positive electrode active material of the present disclosure. For example, silicon-based active materials such as Si, Si alloys, and silicon oxide; carbon-based active materials such as graphite and hard carbon; various oxide-based active materials such as lithium titanate; metallic lithium, lithium alloys, and the like may be used. Only one type of negative electrode active material may be used alone, or two or more types may be used in combination.

The shape of the negative electrode active material may be any shape that is common for negative electrode active materials in batteries. For example, the negative electrode active material may be in a particulate form. The negative electrode active material particles may be primary particles or secondary particles formed by agglomeration of multiple primary particles. The average particle diameter (D50) of the negative electrode active material particles may be, for example, 1 nm or more, 5 nm or more, or 10 nm or more, and may be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less. Alternatively, the negative electrode active material may be in a sheet form (foil form, film form) such as lithium foil. In other words, the negative electrode active material layer may be made of a sheet of negative electrode active material.

Electrolytes that may be included in the negative electrode active material layer include the above-mentioned solid electrolytes, electrolytic solutions, or combinations thereof. Conductive assistants that may be included in the negative electrode active material layer include the above-mentioned carbon materials and metal materials. Binders that may be included in the negative electrode active material layer may be appropriately selected from, for example, those exemplified as binders that may be included in the above-mentioned positive electrode active material layer. Only one type of electrolyte or binder may be used alone, or two or more types may be used in combination.

(Negative electrode current collector layer)
The negative electrode layer may include a negative electrode collector layer in contact with the negative electrode active material layer. The negative electrode collector layer may be any of those generally used as a negative electrode collector layer for a battery. The negative electrode collector layer may be in the form of a foil, a plate, a mesh, a punching metal, or a foam. The negative electrode collector layer may be a metal foil or a metal mesh, or may be a carbon sheet. In particular, the metal foil is excellent in terms of ease of handling. The negative electrode collector layer may be made of a plurality of foils or sheets. Examples of metals constituting the negative electrode collector layer include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel. In particular, from the viewpoint of ensuring reduction resistance and being difficult to alloy with lithium, the negative electrode collector layer may contain at least one metal selected from Cu, Ni, and stainless steel. The thickness of the negative electrode collector layer is not particularly limited. For example, it may be 0.1 μm or more, or 1 μm or more, and may be 1 mm or less, or 100 μm or less.

10, 11, 12, 13 unit cell 10a positive electrode collector layer 10b positive electrode active material layer 10c electrolyte layer 10d negative electrode active material layer 10e negative electrode collector layer 10x positive electrode layer 10y negative electrode layer 21, 21a, 21b, 21c, 21d, 25 adhesive layer (between unit cells)
22, 22b, 22c, 22d Adhesive layer (between unit cell and positive electrode layer)
23, 23a, 23b, 23c Adhesive layer (between unit cell and negative electrode layer)
31, 31a, 31b Conductive member layer 32 Conductive member layer (with thick portion)
32a: Thick portion of conductive member layer 51, 52, 53: Electrical contact (good)
55 Electrical contact (poor)
81 Peripheral region of unit cell 91 Central region of unit cell 100, 200 Bipolar battery module of the present invention

Claims (3)

A bipolar battery module in which two or more unit cells are stacked in series,
the unit cell is a laminate of a positive electrode layer, an electrolyte layer, and a negative electrode layer,
The unit cell has, in a planar direction, a peripheral region and a central region that is a region other than the peripheral region, and satisfies the following ( ii ) :
(ii) a conductive member layer is disposed between a negative electrode layer of a first unit cell among the two or more unit cells and a positive electrode layer of a second unit cell among the two or more unit cells, the negative electrode layer of the first unit cell and the conductive member layer being bonded to each other in the central region via a second adhesive layer and being in electrical contact with each other in the peripheral region, and the conductive member layer and the positive electrode layer of the second unit cell being bonded to each other in the central region via a third adhesive layer and being in electrical contact with each other in the peripheral region;
Bipolar battery module. the conductive member layer has a thick portion in contact with the peripheral region, and the conductive member layer is a conductive cooling member layer having a coolant flow path through which a coolant flows.
The bipolar battery module according to claim 1 . The adhesive layer has a sheet-like substrate and a plurality of nanofibers fixed to the sheet-like substrate,
an adhesive sheet that adheres and holds an adherend that is in contact with the nanofiber to a surface of the nanofiber by intermolecular forces acting between the adherend and the nanofiber ; and
the adherends are the negative electrode layer of the first unit cell, the conductive member layer, and the positive electrode layer of the second unit cell;
The bipolar battery module according to claim 1 or 2 .

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