Patent Publication Number: US-2023135817-A1

Title: Power supply device, electric vehicle provided with power supply device, and power storage device

Description:
TECHNICAL FIELD 
     The present invention relates to a power supply device in which a large number of battery cells are stacked, and an electric vehicle and a power storage device provided with the power supply device. 
     BACKGROUND ART 
     A power supply device in which a large number of battery cells are stacked is suitable as a power source that is mounted on an electric vehicle and supplies electric power to a motor that drives the vehicle, a power source that is charged with a natural energy such as a solar battery or midnight electric power, and a backup power source in the event of a power failure. In the power supply device having this structure, a separator is sandwiched between the stacked battery cells. The power supply device in which a large number of battery cells are stacked with a separator interposed therebetween fixes the stacked battery cells in a pressurized state in order to prevent positional displacement due to expansion of the battery cells. In order to realize this, in the power supply device, a pair of end plates is disposed on both end surfaces of a battery block in which a large number of battery cells are stacked, and the pair of end plates are connected by a bind bar. (See PTL 1) 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: Unexamined Japanese Patent Publication No. 2018-204708 
       
    
     SUMMARY OF THE INVENTION 
     Technical Problem 
     In the power supply device, a plurality of battery cells are stacked to form a battery block, a pair of end plates are disposed on both end surfaces of the battery block, and the battery cells are held in a pressurized state by a considerably strong pressure from both end surfaces and the pair of end plates are connected by a binding bar. In the power supply device, the battery cells are fixed in a strongly pressurized state to prevent malfunction due to relative movement or vibration of the battery cells. When the power supply device uses, for example, a battery cell with a stacked surface having an area of about 100 cm 2 , the end plates are pressed with a strong force of several tons and fixed with the binding bar. In the power supply device having this structure, a plate-shaped insulating plastic plate is used as the separator in order to insulate the adjacently stacked battery cells with the separator. The separator of the plastic plate cannot absorb the expansion of the battery cells in a state where an internal pressure of each of the battery cells increases and expands, and in this state, a surface pressure between the battery cell and the separator rapidly increases, and an extremely strong force acts on the end plates and the binding bar. For this reason, the end plates and the binding bar are required to have a very strong material and shape, and there is an adverse effect that the power supply device becomes heavy and large, and the material cost increases. 
     The present invention has been developed to solve the above disadvantages, and an object of the present invention is to provide a technique for absorbing expansion of battery cells by a separator. 
     Solution to Problem 
     A power supply device according to an aspect of the present invention includes: a battery block formed by stacking a plurality of battery cells in a thickness with a separator interposed between the battery cells; a pair of end plates disposed on both end surfaces of the battery block; and a binding bar connected to the pair of end plates and configured to fix the battery block in a pressurized state via the end plates. The separator is formed by stacking an elastomer layer, and a plastic foam layer having a larger amount of deformation with respect to a pressing force than the elastomer layer. 
     An electric vehicle according to an aspect of the present invention includes the above-described power supply device, a motor for traveling to which electric power is supplied from the power supply device, a vehicle body on which the power supply device and the motor are mounted, and wheels driven by the motor to cause the vehicle body to travel. 
     A power storage device according to an aspect of the present invention includes the above-described power supply device, and a power supply controller that controls charging and discharging to the power supply device, wherein the power supply controller enables charging to the battery cells by electric power from an outside, and performs control to charge the battery cells. 
     Advantageous Effect of Invention 
     In the power supply device described above, the expansion of the battery cells is absorbed by the separator, and a rapid increase in surface pressure between each of the battery cells and the separator can be suppressed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a power supply device according to an exemplary embodiment of the present invention. 
         FIG.  2    is a vertical cross-sectional view of the power supply device illustrated in  FIG.  1   . 
         FIG.  3    is a horizontal cross-sectional view of the power supply device illustrated in  FIG.  1   . 
         FIG.  4    is an exploded perspective view illustrating a stacked structure of battery cells and a separator. 
         FIG.  5    is a partially enlarged cross-sectional view illustrating a stacked structure of battery cells and a separator. 
         FIG.  6    is an enlarged cross-sectional view of a main part illustrating a state in which a surface of an expanding battery cell is pushed by parallel ridges and deformed into a wave shape. 
         FIG.  7    is a perspective view illustrating another example of the separator. 
         FIG.  8    is a partially enlarged cross-sectional view illustrating another example of the separator. 
         FIG.  9    is a partially enlarged cross-sectional view illustrating another example of the separator. 
         FIG.  10    is an exploded perspective view illustrating a stacked structure of battery cells and a separator of another example. 
         FIG.  11    is a block diagram illustrating an example in which a power supply device is mounted on a hybrid vehicle that travels by an engine and a motor. 
         FIG.  12    is a block diagram illustrating an example in which a power supply device is mounted on an electric vehicle that travels only by a motor. 
         FIG.  13    is a block diagram illustrating an example of application to a power supply device for power storage. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     Hereinafter, the present invention will be described in detail with reference to the drawings. Note that, in the following description, terms (e.g., “top”, “bottom”, and other terms including those terms) indicating specific directions or positions are used as necessary; however, the use of those terms is for facilitating the understanding of the invention with reference to the drawings, and the technical scope of the present invention is not limited by the meanings of the terms. Further, parts denoted by the same reference marks in a plurality of drawings indicate the same or equivalent parts or members. 
     Furthermore, exemplary embodiments to be described below show a specific example of the technical idea of the present invention, and the present invention is not limited to the exemplary embodiments below. Further, unless otherwise specified, dimensions, materials, shapes, relative dispositions, and the like of the configuration components described below are not intended to limit the scope of the present invention only to them, but are intended to be illustrative. Furthermore, the contents described in one exemplary embodiment or example are also applicable to other exemplary embodiments and examples. Additionally, sizes, positional relationships, and the like of members illustrated in the drawings may be exaggerated for clarity of description. 
     A power supply device according to a first exemplary embodiment of the present invention includes a battery block formed by stacking a plurality of battery cells in a thickness with a separator interposed between the battery cells, a pair of end plates disposed on both end surfaces of the battery block, and a binding bar connected to the pair of end plates and configured to fix the battery block in a pressurized state via the end plates. The separator is formed by stacking an elastomer layer, and a plastic foam layer having a larger amount of deformation with respect to a pressing force than the elastomer layer. 
     In the separator of the power supply device described above, since the elastomer layer and the plastic foam layer that is more easily deformed than the elastomer layer are stacked, both the elastomer layer and the plastic foam layer elastically deform and absorb the expansion of each of the battery cells. Since the plastic foam layer is thinly deformed by crushing innumerable bubbles, the plastic foam layer is easily deformed as compared with the elastomer layer, and thus has a small Young&#39;s modulus and more effectively absorbs the expansion of the battery cell. When the expansion of the battery cell increases and the pressing force of the separator increases, the plastic foam layer that is easily deformed exceeds an elastic limit and cannot absorb the expansion of the battery cell. The elastomer layer is less likely to deform than the plastic foam layer, and elastically deforms in a region where the plastic foam layer exceeds the elastic limit to absorb the expansion of the battery cell. Accordingly, in the separator in which the elastomer layer and the plastic foam layer are stacked, small expansion of the battery cell is naturally absorbed by the plastic foam layer that is easily deformed, and in a region where the expansion of the battery cell becomes large and the pressing force of the separator becomes strong, the elastomer layer that is hardly deformed absorbs the expansion. Therefore, the separator described above has an advantage of being able to absorb even large expansion while more smoothly absorbing small expansion of the battery cell having a high occurrence frequency. Further, the plastic foam layer can also be expected to have an effect of absorbing dimensional tolerances of the battery cell and the separator. 
     Furthermore, in the power supply device described above, since the elastomer layer and the plastic foam layer that is more easily deformed than the elastomer layer suppress an increase in surface pressure due to expansion of the battery cell, it is possible to prevent the battery cell from expanding and an excessive stress from acting on the end plates and the binding bar. The plastic foam layer can efficiently absorb small expansion of the battery cell, but when the expansion of the battery cell becomes large and exceeds the elastic limit, the plastic foam layer cannot be elastically deformed and causes a rapid increase in stress of the end plates and the binding bar. However, in a region where the plastic foam layer exceeds the elastic limit, the elastomer layer stacked on the plastic foam layer is elastically deformed to suppress an increase in stress of the end plates and the binding bar, so that it is possible to suppress an increase in maximum stress acting on the end plates and the binding bar due to an increase in expansion of the battery cell. In the power supply device capable of suppressing the maximum stress acting on the end plates and the binding bar, the weight can be reduced by thinning the end plates and the binding bar. 
     Further, in the power supply device in which both the elastomer layer and the plastic foam layer are elastically deformed to be able to effectively absorb the expansion of the battery cell, it is also possible to suppress the relative position from being shifted due to the expansion of the battery cell. This can also prevent adverse effects of an electrical connection part of the battery cell. This is because, although the stacked battery cells are electrically connected by fixing bus bars of metal sheets to electrode terminals, when the battery cells are displaced relative to each other, an excessive stress acts on the bus bars and the electrode terminals, which causes a failure. 
     In the power supply device according to a second exemplary embodiment of the present invention, the elastomer layer is a non-foamed synthetic rubber. 
     In the power supply device according to a third exemplary embodiment of the present invention, the synthetic rubber of the elastomer layer is any one of a fluororubber, an isoprene rubber, a styrene butadiene rubber, a butadiene rubber, a chloropron rubber, a nitrile rubber, a hydrogenated nitrile rubber, a folylisobutylene rubber, an ethylene propylene rubber, an ethylene-vinyl acetate copolymer rubber, a chlorosulfonated polyethylene rubber, an acrylic rubber, an epichlorohydrin rubber, a urethane rubber, a silicone rubber, a thermoplastic olefin rubber, an ethylene propylene diene rubber, a butyl rubber, and a polyether rubber. 
     In the power supply device according to a fourth exemplary embodiment of the present invention, the plastic foam layer is an open-cell plastic foam. 
     In this power supply device, the open-cell plastic foam layer is more smoothly crushed, and expansion of the battery cell can be more effectively absorbed. Further, the open-cell plastic foam layer can equalize a surface pressure distribution on the surface of the battery cell to prevent an adverse effect that the pressure locally increases. This is because, in the open-cell plastic foam, air in the pressed and crushed cells flows to the surroundings through the open cells and is easily deformed. 
     In the power supply device according to a fifth exemplary embodiment of the present invention, the plastic foam layer is a closed-cell plastic foam. 
     In this power supply device, since closed cells of the plastic foam layer of the separator serve as an air cushion and are elastically deformed, a foam rate of the plastic foam layer can be increased and the material cost can be reduced. Further, the closed-cell air cushion can be elastically deformed in a wide pressure range to absorb expansion of the battery cell. 
     In the power supply device according to a sixth exemplary embodiment of the present invention, the plastic foam layer is a urethane foam. 
     In the power supply device according to a seventh exemplary embodiment of the present invention, the elastomer layer includes a comb-teeth-shaped cross-sectional shape by alternately disposing a plurality of rows of parallel ridges and a plurality of rows of parallel grooves on a surface of a plate-shaped part, the surface facing each of the battery cells. 
     In the power supply device described above, the parallel ridges of the separator locally press an electrode of the battery cell to improve the fluidity of an electrolyte solution. The reason why the comb-teeth-shaped separator in which the parallel ridges and the parallel grooves are alternately provided on the surface facing the battery cell can improve the fluidity of the electrolyte solution is that the electrode has a high density in a region pressed by the parallel ridges, but the electrode has a low density in a region facing the parallel grooves not pressed by the parallel ridges, so that the electrolyte solution easily moves. 
     In the power supply device according to an eighth exemplary embodiment of the present invention, lateral width (W1) of the parallel ridges and opening width (W2) of the parallel grooves are in a range from 1 mm to 20 mm, inclusive. 
     In the power supply device according to a ninth exemplary embodiment of the present invention, height (h) of the parallel ridges is in a range from 0.1 mm to 2 mm, inclusive. 
     In the power supply device according to a tenth exemplary embodiment of the present invention, ratio (W1/W2) between lateral width (W1) of the parallel ridges and opening width (W2) of the parallel grooves are in a range from 0.1 to 10, inclusive. 
     In the power supply device according to an eleventh exemplary embodiment of the present invention, each of the battery cells includes an electrode that is a plate-shaped electrode in which positive and negative electrode layers extending in a band shape are spirally wound and pressed into a planar shape, and the elastomer layer of the separator is disposed in an attitude in which the parallel ridges and the parallel grooves extend in a width direction of the positive and negative electrode layers that are in a band shape. 
     In the power supply device according to a twelfth exemplary embodiment of the present invention, the separator includes a two-layer structure of the elastomer layer and the plastic foam layer. 
     In the power supply device according to a thirteenth exemplary embodiment of the present invention, the separator includes a three-layer structure in which a plurality of the elastomer layers are stacked on both surfaces of the plastic foam layer. 
     First Exemplary Embodiment 
     Power supply device  100  illustrated in a perspective view of  FIG.  1   , a vertical cross-sectional view of  FIG.  2   , and a horizontal cross-sectional view of  FIG.  3    includes battery block  10  in which a plurality of battery cells  1  are stacked in a thickness with separator  2  interposed therebetween, a pair of end plates  3  disposed on both end surfaces of battery block  10 , and binding bars  4  that connect the pair of end plates  3  and fix battery block  10  in a pressurized state via end plates  3 . 
     (Battery Block  10 ) 
     In battery block  10 , a plurality of battery cells  1 , which are prismatic battery cells having a quadrangular outer shape, are stacked in a thickness with separator  2  interposed therebetween. The plurality of battery cells  1  are stacked such that top surfaces thereof are flush with each other to constitute battery block  10 . 
     (Battery Cell  1 ) 
     As illustrated in  FIGS.  4  and  5   , in each of battery cells  1 , electrode  15  is inserted into battery case  11  whose bottom is closed, and sealing plate  12  is laser-welded and airtightly fixed to an upper end opening part, so that the inside has a sealed structure. Further, the inside of battery case  11  is filled with an electrolyte solution (not illustrated). As illustrated in  FIG.  1   , sealing plate  12  is provided with a pair of positive and negative electrode terminals  13  protruding upward at both end parts of the top surface. Safety valve  14  is provided between electrode terminals  13 . Safety valve  14  is opened to release internal gas when an internal pressure of battery cell  1  rises to more than or equal to a predetermined value. Safety valve  14  prevents an increase in internal pressure of battery cell  1 . 
     Battery cell  1  is a lithium ion secondary battery. Power supply device  100  provided with a lithium ion secondary battery serving as battery cell  1  has an advantage in that a charging capacity per volume and weight can be increased. However, battery cell  1  may be any other chargeable battery such as a non-aqueous electrolyte secondary battery other than the lithium ion secondary battery. 
     (End Plates  3 , Binding Bars  4 ) 
     Each of end plates  3  is a metal sheet substantially coinciding in outer shape with battery cell  1  and is not deformed by being pressed by battery block  10 , and binding bars  4  are connected to both side edges of end plate  3 . End plates  3  connect stacked battery cells  1  in a pressurized state, and binding bars  4  fix battery block  10  in the pressurized state at a predetermined pressure. 
     (Separator  2 ) Separator  2  is sandwiched between stacked battery cells  1 , suppresses a decrease in fluidity of the electrolyte solution while absorbing expansion of battery cells  1  due to an increase in internal pressure, and further insulates adjacent battery cells  1 . Battery block  10  has bus bars (not illustrated) fixed to electrode terminals  12  of adjacent battery cells  1  to connect battery cells  1  in series or in parallel. In battery cells  1  connected in series, since a potential difference is generated between battery cases  11 , battery cells  1  are insulated and stacked by separator  2 . Although battery cells  1  connected in parallel cause no potential difference to be generated between battery cases  11 , battery cells  1  are stacked while being thermally insulated by separator  2  to prevent induction of thermal runaway. 
     Separator  2  illustrated in the enlarged sectional view of  FIG.  5    has a stacked structure of elastomer layer  5  and plastic foam layer  6  having different deformation amounts with respect to a pressing force. Elastomer layer  5  and plastic foam layer  6  having different deformation amounts with respect to the pressing force are elastically deformed so as to be pressed by expanding battery cell  1  and become thin, and absorb the expansion of battery cell  1 . In power supply device  100 , in order to miniaturize battery block  10  and increase the charging capacity, it is important to thin separator  2  to absorb the expansion of battery cell  1 . Thus, entire thickness (d) of separator  2  having a stacked structure is, for example, in a range from 2 mm to 8 mm inclusive, more preferably in a range from 1.5 mm to 5 mm inclusive. 
     Elastomer layer  5  of separator  2  is a non-foamed rubber-like elastic body or foamed rubber. Elastomer layer  5  can elastically deform and absorb the expansion of battery cell  1  with a hardness of, for example, A30 degrees to A90 degrees. As elastomer layer  5 , a synthetic rubber sheet is suitable. As the synthetic rubber sheet, any one of fluororubber, isoprene rubber, styrene butadiene rubber, butadiene rubber, chloropron rubber, nitrile rubber, hydrogenated nitrile rubber, folylisobutylene rubber, ethylene propylene rubber, ethylene vinyl acetate copolymer rubber, chlorosulfonated polyethylene rubber, acrylic rubber, epichlorohydrin rubber, urethane rubber, silicone rubber, thermoplastic olefin rubber, ethylene propylene diene rubber, butyl rubber, and polyether rubber can be used singly or in a stacked state of a plurality of the synthetic rubber sheets. In particular, the ethylene propylene rubber, the ethylene vinyl acetate copolymer rubber, the chlorosulfonated polyethylene rubber, the acrylic rubber, the fluororubber, and the silicone rubber have excellent heat insulating properties, and thus can realize high safety until a temperature of battery cell  1  rises to a high temperature. Further, when elastomer layer  5  is made of urethane rubber, it is particularly preferable to use thermoplastic polyurethane rubber or foamed polyurethane rubber. 
     Separator  2  illustrated in  FIG.  4    and  FIG.  5    has a cross section in a comb-teeth shape by alternately disposing a plurality of rows of parallel ridges  21  and a plurality of rows of parallel grooves  22  on a surface of plate-shaped part  20 , which is a surface facing a battery cell surface. In separator  2 , the plurality of rows of parallel ridges  21  locally press the surface of expanding battery cell  1 . In battery cell  1  whose surface is pressed by the plurality of rows of parallel ridges  21 , a region pressed by the parallel ridges  21  becomes a recess, and a region facing the parallel grooves  22  protrudes, and battery cell  1  is deformed into a wave shape. The enlarged cross-sectional view of the main part of  FIG.  6    exaggeratedly illustrates a state in which the surface of battery cell  1  is pushed by parallel ridges  21  and deformed into a wave shape. Battery cell  1  whose surface is deformed into a wave shape deforms a surface of electrode  15  having a stacked structure housed in battery case  11  into a wave shape. In electrode  15  having the stacked structure, region A which is pressed by the plurality of rows of parallel ridges  21  to become the recess has a high density, and protruding region B which is a region facing parallel grooves  22  has a low density. Therefore, low density region B is generated in a stripe manner, and low density region B improves the fluidity of the electrolyte solution. Further, since separator  2  described above generates low density region B in a stripe manner in electrode  15  while absorbing the expansion of battery cell  1  by the elastic deformation of elastomer layer  5 , separator  2  is characterized in that low density region B can be generated in a stripe manner in electrode  15  to improve the fluidity of the electrolyte solution even at the time of expansion of battery cell  1  in which the fluidity of the electrolyte solution decreases. 
     Battery cell  1  illustrated in  FIGS.  4  to  6    is a prismatic battery in which a stacked surface of battery case  11  on which separator  2  is stacked is a quadrangular shape, positive and negative electrode layers  15   a ,  15   b  having an elongated band shape are wound to form spiral electrode  15 , and spiral electrode  15  is housed in battery case  11  as a plate shape pressed in a planar shape. In electrode  15 , elongated band-shaped positive and negative electrode layers  15   a ,  15   b  are stacked with insulating sheet  15   c  interposed therebetween, and wound to form spiral electrode  15 , and spiral electrode  15  is pressed into a planar shape and housed in rectangular battery case  11 . In separator  2  of elastomer layer  5 , as illustrated in  FIG.  4   , parallel ridges  21  and parallel grooves  22  are arranged in an attitude extending in a width direction of band-shaped positive and negative electrode layers  15   a ,  15   b . In separator  2 , parallel ridges  21  are arranged in parallel with an extending direction of U-shaped curved part  15 A of spiral electrode  15 , and high density region A and low density region B extending in the width direction of electrode layers  15   a ,  15   b  are formed in a strip shape on the surface of electrode  15 , so that high density region A and low density region B can be naturally provided in a stripe shape on spiral electrode  15  to improve the fluidity of the electrolyte solution. 
     Lateral width (W1) and height (h) of parallel ridges  21  and opening width (W2) of parallel grooves  22  are set to a dimension that allows parallel ridges  21  to press the surface of battery case  11  and deform into a wave shape in consideration of the hardness of elastomer layer  5 . In separator  2  in which a hardness of elastomer layer  5  is A30 degrees to A90 degrees, for example, lateral width (W1) of parallel ridges  21  is in a range from 1 mm to 20 mm inclusive, preferably in a range from 2 mm to 10 mm inclusive, height (h) is in a range from 0.1 mm to 2 mm inclusive, preferably in a range from 0.2 mm to 1.5 mm inclusive, opening width (W2) of parallel grooves  22  is in a range from 1 mm to 20 mm inclusive, preferably in a range from 2 mm to 10 mm inclusive, and ratio (W1/W2) of lateral width (W1) of parallel ridges  21  to opening width (W2) of parallel grooves  22  is in a range from 0.1 to 10 inclusive, preferably in a range from 0.5 to 2 inclusive so that separator  2  can be deformed into a wave shape by pressing metal battery case  11  of battery cell  1 . 
     In separator  2  of elastomer layer  5 , a deformation amount of battery case  11  can be increased by increasing height (h) of parallel ridges  21  to increase opening width (W2) of parallel grooves  22 . However, when parallel ridges  21  are too high, separator  2  becomes thick and buckles easily. Therefore, height (h) of parallel ridges  21  is set within the above range in consideration of the thickness allowed for separator  2  and the fact that battery case  11  can be deformed into a wave shape by being locally pressed. Further, opening width (W2) of parallel grooves  22 , and ratio (W1/W2) of lateral width (W1) of parallel ridges  21  to opening width (W2) of parallel grooves  22  specify a pitch at which the surface of battery case  11  is deformed into a wave shape, and thus are set within the above ranges in consideration of setting the fluidity of the electrolyte solution to a preferable state while the expansion of battery cell  1  is supported by the plurality of rows of parallel ridges  21 . For example, in power supply device  100  in which battery cell  1  is a prismatic lithium ion battery, battery case  11  is an aluminum plate having a thickness of 0.3 mm, an area of the stacked surface is 100 cm 2 , lateral width (W1) of parallel ridges  21  and opening width (W2) of parallel grooves  22  are 5 mm, a height of parallel ridges  21  is 0.5 mm, a hardness of elastomer layer  5  is A60 degrees, and the number of battery cells  1  to be stacked is 12, the surface facing separator  2  is deformed into a wave shape in a state where battery cell  1  expands, and the fluidity of the electrolyte solution can be improved. 
     Separator  2  illustrated in  FIG.  4    has a structure in which an entire length of the plurality of rows of parallel ridges  21  extending in a lateral width direction (horizontal direction in the drawing) of battery cell  1  is substantially equal to a lateral width of battery cell  1 , and a facing surface of battery cell  1  is pressed by the plurality of rows of parallel ridges  21  extending in a streak parallel to each other. Further, as illustrated in  FIG.  7   , separator  2  can also be divided into the plurality of parallel ridges  21  extending in a longitudinal direction. In separator  2  illustrated in  FIG.  7   , cut part  24  is provided at an intermediate part of parallel ridges  21  to divide one row of the parallel ridges  21  into a plurality of convex parts  23 . Further, in adjacent parallel ridges  21 , convex parts  23  are arranged in a staggered manner when viewed from a front. That is, the positions of convex parts  23  are shifted left and right between adjacent parallel ridges  21  such that convex part  23  of the other parallel ridge  21  is positioned at a position facing cut part  24  provided on one parallel ridge  21 . In separator  2  illustrated in the drawing, in order to form convex parts  23  of parallel ridges  21  adjacent to each other into a staggered shape, cut parts  24  are also provided at both ends of parallel ridges  21  in every other row. As described above, the structure in which the plurality of divided convex parts  23  are arranged in a staggered shape has an advantage that the pressing force received from battery cell  1  can be uniformly dispersed. However, the plurality of divided convex parts can be arranged vertically and horizontally or randomly. Separator  2  including parallel ridges  21  having the shape described above is more easily elastically deformed than separator  2  having a structure in which parallel ridges  21  are not divided, and has an advantage that expansion of battery cell  1  can be effectively absorbed. 
     Furthermore, in separator  2  having the shape illustrated in  FIG.  7   , the ease of elastic deformation of parallel ridges  21  can be adjusted by adjusting length (L1) of convex part  23  and length (L2) of cut part  24 . For example, separator  2  can be easily elastically deformed by increasing ratio (L2/L1) of length (L2) of cut part  24  to length (L1) of convex part  23 , and on the contrary, separator  2  can be hardly elastically deformed by decreasing ratio (L2/L1). That is, separators  2  can be deformed more easily by dividing parallel ridges  21  into a plurality of parts than a structure in which parallel ridges  21  are not divided, and can be deformed more easily by adjusting ratio (L2/L1). Furthermore, ratio (L2/L1) of length (L2) of cut part  24  to length (L1) of convex part  23  can be changed depending on the region even on one surface facing battery cell  1 . For example, ratio (L2/L1) can be increased to easily absorb the deformation in a region facing a central part where the deformation amount increases when battery cell  1  expands, and ratio (L2/L1) can be decreased to suppress the deformation in a region facing an outer peripheral part where the deformation amount during expansion is small. 
     Plastic foam layer  6  is more easily deformed than elastomer layer  5 , and in a state where the expansion of battery cell  1  is small, the deformation of plastic foam layer  6  is larger than the deformation of elastomer layer  5 , and plastic foam layer  6  absorbs the expansion of battery cell  1  more than elastomer layer  5 . In a state where the expansion of battery cell  1  increases and the deformation of plastic foam layer  6  exceeds the elastic limit, elastomer layer  5  that is hardly deformed is deformed and absorbs the expansion. Plastic foam layer  6  that is more easily deformed than elastomer layer  5  is an open-cell or closed-cell foam. The open-cell plastic foam has a smaller Young&#39;s modulus than the closed-cell plastic foam. Therefore, the open-cell plastic foam layer is elastically deformed in a region where the expansion of battery cell  1  is small to effectively absorb the expansion. This is because when the open-cell foam is pressed and the cell is crushed, the air inside the foam is smoothly discharged. Since a thin film constituting the cell is deformed in the cell from which the air inside is exhausted, the deformation amount with respect to the pressing force increases. On the other hand, when the closed-cell foam is pressed and the cell is compressed, the air in the cell is pressurized, and thus the air cushion in the cell suppresses the deformation of the cell, so that the deformation with respect to the pressing force is smaller than that of the open-cell foam. In the open-cell plastic foam having a large deformation amount with respect to the pressing force, the Young&#39;s modulus can be adjusted by an expansion ratio and a porosity, and the Young&#39;s modulus can be decreased by increasing the porosity. 
     Even when the closed-cell plastic foam layer is pressed by battery cell  1  to compress the cell, the air in the cell is not pushed out, the air pressure increases in the cell to prevent the deformation of the cell, and an internal pressure in the cell increases as the cell is crushed to be small to suppress the deformation of the cell. Since the closed-cell plastic foam layer suppresses deformation of the air cushion of the cells in a state where the air cushion is pressed, the Young&#39;s modulus can be increased while achieving a high expansion ratio. Therefore, the expansion of battery cell  1  can be absorbed while reducing the material cost and the weight. 
     In separator  2  illustrated in the partially enlarged view of  FIG.  5   , non-foam layer  6 B is provided on a surface of open-cell plastic foam layer  6 . Non-foam layer  6 B on the surface of separator  2  is in surface contact with the surface of battery cell  1  in a state of being sandwiched between battery cells  1 . Separator  2  absorbs expansion of battery cell  1  by elastic deformation of foam layer  6 A in a state where non-foam layer  6 B is in close contact with the surface of battery cell  1 . Therefore, separator  2  can absorb the expansion of battery cell  1  by deformation of foam layer  6 A into a shape that follows the expansion of battery cell  1  while non-foam layer  6 B is deformed into a curved shape along the surface of battery cell  1  that expands. 
     Separator  2  illustrated in the enlarged sectional view of  FIG.  8    is foam layer  6 C which is a surface of plastic foam layer  6  having open cells and from which cells obtained by cutting a stacked surface with battery cells  1  are exposed, and has an infinite number of irregularities formed on the surface by the open cells. In separator  2 , an infinite number of continuous bubbles absorb dew condensation water adhering to the surface of battery cell  1 , and electric leakage and a decrease in insulation resistance due to the dew condensation water can be suppressed. Since the power supply device is used in various temperature environments, dew condensation water may adhere to the surface due to a change in the temperature environment. The dew condensation water adhering to the surface of battery cell  1  flows down to the surface of an energization part to cause electric leakage or reduce the insulation resistance of the energization part. Separator  2  in which the open cells are exposed on the surface absorbs the dew condensation water to prevent adverse effects of the dew condensation water. Further, separator  2  in which the open cells are exposed on the surface and elastically deformed to be brought into close contact with the surface of battery cell  1  can transfer the dew condensation water to be absorbed into separator  2 , and therefore has an advantage that the amount of the dew condensation water to be absorbed can be increased to effectively prevent adverse effects caused by the dew condensation water. 
     Plastic foam layer  6  is adjusted to have elasticity and a thickness that allow expanding battery cells  1  to absorb expansion by being pressurized and deformed. An amount of deformation of plastic foam layer  6  due to expansion of the battery cells can be adjusted by the type and apparent density of the plastic to be foamed, and the apparent density can be adjusted by a foaming rate. Open-cell plastic foam layer  6  has an apparent density, for example, in a range from 150 kg/m 3  to 750 kg/m 3  inclusive, preferably in a range from 200 kg/m 3  to 500 kg/m 3  inclusive, and has a thickness, for example, in a range from 0.2 mm to 7 mm inclusive, preferably in a range from 1 mm to 5 mm inclusive. As open-cell plastic foam layer  6 , urethane foam is suitable. The separator of urethane foam has excellent temperature characteristics, and can be compressed to 50% for 22 hours at 100° C., for example, to have a compression set of less than or equal to 20%. 
     In separator  2 , plastic foam layer  6  is stacked on one surface of elastomer layer  5 . As illustrated in  FIGS.  4  and  5   , separator  2  is stacked between battery cells  1  adjacent to each other and sandwiched from both sides. Separator  2  presses the surface of one battery cell  1  adjacent to elastomer layer  5 , and plastic foam layer  6  presses the surface of the other battery cell  1 . In separator  2 , parallel ridges  21  of elastomer layer  5  press one surface of battery cell  1  to improve fluidity of the electrolyte solution on the battery cell surface facing elastomer layer  5 . In separator  2  having this structure, as illustrated in  FIG.  4   , in a state in which the plurality of battery cells  1  and separator  2  are alternately stacked to form battery block  10 , parallel ridges  21  of elastomer layer  5  can be brought into contact with the stacked surfaces of all battery cells  1  by stacking so that the surfaces of elastomer layer  5  provided with parallel ridges  21  and parallel grooves  22  are oriented in the same direction, and the fluidity of the electrolyte solution of all battery cells  1  can be improved. 
     In separator  2  illustrated in  FIG.  9   , plastic foam layer  6  is sandwiched in the middle, and both sides of plastic foam layer  6  are formed as elastomer layers  5 . In separator  2 , parallel ridges  21  and parallel grooves  22  are provided in elastomer layers  5  on both surfaces, and battery cells  1  are pressed by parallel ridges  21  on both surfaces, so that the fluidity of the electrolyte solution on the surfaces of the respective battery cells can be improved. 
     In battery cell  1  described above, as illustrated in  FIG.  4   , plate-shaped spiral electrode  15  is housed in battery case  11  such that the axis along the width of battery cell  1 . Therefore, separator  2  is stacked on the facing surface of battery cell  1  such that the extending direction of parallel ridges  21  and parallel grooves  22  is the width direction of battery cell  1 . As described above, parallel ridges  21  and parallel grooves  22  of separator  2  are stacked so as to extend in the horizontal direction in the drawing, whereby parallel ridges  21  and parallel grooves  22  can be arranged on the surface of battery cell  1  so as to be parallel to the axis of spiral electrode  15 . As a result, when battery cell  1  expands, the high density region and the low density region extending in the width direction of electrode layers  15   a ,  15   b  are formed in a stripe shape on the surface of spiral electrode  15 , and the fluidity of the electrolyte solution can be improved. 
     However, as illustrated in  FIG.  10   , in battery cell  1 , plate-shaped spiral electrode  15  can also be housed in battery case  1  such that the axis along the height of battery cell  1  and the depth of battery case  11 . Separator  2  stacked on battery cell  1  having this structure is stacked on the facing surface of battery cell  1  such that the extending direction of parallel ridges  21  and parallel grooves  22  is the height direction of battery cell  1 . According to this structure, parallel ridges  21  and parallel grooves  22  of separator  2  are stacked on battery cells  1  so as to be in an attitude extending in the up-down direction in the drawing, whereby parallel ridges  21  and parallel grooves  2  can be arranged on the surface of battery cells  1  so as to be parallel to the axis of spiral electrode  15 . As a result, when battery cell  1  expands, the high density region and the low density region extending in the width direction of electrode layers  15   a ,  15   b  are formed in a stripe shape on the surface of spiral electrode  15 , and the fluidity of the electrolyte solution can be improved. 
     The power supply device described above can be used as a power source for a vehicle where electric power is supplied to a motor used for causing an electric vehicle to travel. As an electric vehicle on which the power supply device is mounted, an electric vehicle such as a hybrid automobile or a plug-in hybrid automobile that travels by both an engine and a motor, or an electric automobile that travels only by a motor can be used, and the power supply device is used as a power source for the vehicle. Note that, in order to obtain electric power for driving a vehicle, an example of constructing large-capacity and high-output power supply device  100  will be described below in which a large number of the above-described power supply devices are connected in series or in parallel, and a necessary controlling circuit is further added. 
     (Power Supply Device for Hybrid Automobile) 
       FIG.  11    illustrates an example in which the power supply device is mounted on the hybrid automobile that travels by both the engine and the motor. Vehicle HV illustrated in the drawing on which the power supply device is mounted includes: vehicle body  91 ; engine  96  and motor  93  for traveling that cause vehicle body  91  to travel; wheels  97  that are driven by engine  96  and motor  93  for traveling; power supply device  100  that supplies electric power to motor  93 ; and power generator  94  that charges a battery of power supply device  100 . Power supply device  100  is connected to motor  93  and power generator  94  via DC/AC inverter  95 . Vehicle HV travels using both motor  93  and engine  96  while charging and discharging the battery of power supply device  100 . Motor  93  is driven in a region where engine efficiency is low, for example, during acceleration or low-speed traveling, and causes the vehicle to travel. Motor  93  is driven by electric power supplied from power supply device  100 . Power generator  94  is driven by engine  96  or by regenerative braking when the vehicle is braked to charge the battery of power supply device  100 . Note that, as illustrated in  FIG.  11   , vehicle HV may be provided with charging plug  98  for charging power supply device  100 . Connecting charging plug  98  to an external power source enables charging of power supply device  100 . 
     (Power Supply Device for Electric Automobile) 
     Further,  FIG.  12    illustrates an example in which a power supply device is mounted on an electric automobile that travels only with a motor. Vehicle EV illustrated in the drawing on which the power supply device is mounted includes vehicle body  91 , motor  93  for traveling that causes vehicle body  91  to travel, wheels  97  driven by motor  93 , power supply device  100  that supplies electric power to motor  93 , and power generator  94  that charges the battery of power supply device  100 . Power supply device  100  is connected to motor  93  and power generator  94  via DC/AC inverter  95 . Motor  93  is driven by electric power supplied from power supply device  100 . Power generator  94  is driven by the energy at the time of applying regenerative braking to vehicle EV and charges the battery of power supply device  100 . Further, vehicle EV includes charging plug  98 , and power supply device  100  can be charged by connecting charging plug  98  to an external power source. 
     (Power Supply Device for Power Storage Device) 
     Furthermore, the application of the power supply device of the present invention is not limited to the power source for the motor that causes a vehicle to travel. The power supply device according to the exemplary embodiment can also be used as a power source for a power storage device that stores electricity by charging a battery with electric power generated by solar power generation, wind power generation, or the like.  FIG.  13    illustrates a power storage device that charges and stores the battery of power supply device  100  with solar battery  82 . 
     The power storage device illustrated in  FIG.  13    charges the battery of power supply device  100  with electric power generated by solar battery  82  disposed on a roof, a rooftop, or the like of building  81  such as a house or a factory. The power storage device charges the battery of power supply device  100  via charging circuit  83  with solar battery  82  serving as a charging power source, and then supplies electric power to load  86  via DC/AC inverter  85 . Thus, this power storage device includes a charge mode and a discharge mode. In the power storage device illustrated in the figure, DC/AC inverter  85  is connected to power supply device  100  via discharging switch  87 , and charging circuit  83  is connected to power supply device  100  via charging switch  84 . Discharging switch  87  and charging switch  84  are turned on and off by power supply controller  88  of the power storage device. In the charge mode, power supply controller  88  turns on charging switch  84  and turns off discharging switch  87  to allow charging from charging circuit  83  to power supply device  100 . Further, when charging is completed and the battery is fully charged or when the battery is in a state where a capacity of a predetermined value or more is charged, power supply controller  88  turns off charging switch  84  and turns on discharging switch  87  to switch the mode to the discharge mode and allows discharging from power supply device  100  to load  86 . Furthermore, it is also possible to simultaneously supply electric power to load  86  and charge power supply device  100  by turning on charging switch  84  and turning on discharging switch  87  as necessary. 
     Further, although not illustrated, the power supply device can also be used as a power source of a power storage device that performs power storage by charging a battery using midnight electric power at night. The power supply device that is charged with midnight electric power is charged with the midnight electric power that is surplus electric power generated by a power station, and outputs the electric power during the daytime when an electric power load increases, which can limit peak electric power during the daytime to a small value. Furthermore, the power supply device can also be used as a power source charged with both output of a solar battery and the midnight electric power. This power supply device can efficiently perform power storage using both electric power generated by the solar battery and the midnight electric power effectively in consideration of weather and electric power consumption. 
     The power storage system as described above can be suitably used for applications such as a backup power supply device that can be mounted on a rack of a computer server, a backup power supply device for a wireless base station such as a cellular phone, a power source for household or factory power storage, a power source for street lamps, and the like, a power storage apparatus combined with a solar battery, and a backup power source for traffic lights and traffic indicators for roads. 
     INDUSTRIAL APPLICABILITY 
     The power source device according to the present invention is suitably used as a power source for a large current used for a power source of a motor for driving an electric vehicle such as a hybrid automobile, a fuel battery automobile, an electric automobile, or an electric motorcycle. Examples thereof include power supply devices for plug-in hybrid electric automobiles and hybrid electric automobiles capable of switching between an EV traveling mode and an HEV traveling mode, electric automobiles, and the like. Further, the present invention can be appropriately used for applications such as a backup power supply device that can be mounted on a rack of a computer server, a backup power supply device for a wireless base station such as a cellular phone, a power source for power storage for home and factory use, a power source for street lamps, and the like, a power storage apparatus combined with a solar battery, and a backup power source for traffic lights and the like. 
     REFERENCE MARKS IN THE DRAWINGS 
     
         
         
           
               100 : power supply device 
               1 : battery cell 
               2 : separator 
               3 : end plate 
               4 : binding bar 
               5 : elastomer layer 
               6 : plastic foam layer 
               6 A: foam layer 
               6 B: non-foam layer 
               6 C: foam layer from which cells are exposed 
               10 : battery block 
               11 : battery case 
               12 : sealing plate 
               13 : electrode terminal 
               14 : safety valve 
               15 : electrode 
               15 A: U-shaped curved part 
               15   a : electrode layer 
               15   b : electrode layer 
               15   c : insulating sheet 
               20 : plate-shaped part 
               21 : parallel ridge 
               22 : parallel groove 
               23 : convex part 
               24 : cut part 
               81 : building 
               82 : solar battery 
               83 : charging circuit 
               84 : charging switch 
               85 : DC/AC inverter 
               86 : load 
               87 : discharging switch 
               88 : power supply controller 
               91 : vehicle body 
               93 : motor 
               94 : power generator 
               95 : DC/AC inverter 
               96 : engine 
               97 : wheel 
               98 : charging plug 
             HV, EV: vehicle