Patent Publication Number: US-2018047518-A1

Title: Electricity storage module

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of Japanese patent application JP2015-055920 filed on Mar. 19, 2015, the entire contents of which are incorporated herein. 
     TECHNICAL FIELD 
     The present invention relates to an electricity storage module including a plurality of electricity storage elements. 
     BACKGROUND ART 
     An electricity storage device disclosed in Patent Document 1 (JP 2010-211963A) is known as a conventional electricity storage device. This electricity storage device includes a plurality of electricity storage elements, a case that accommodates the plurality of electricity storage elements, and absorption sheets that are in contact with the outer surfaces of the electricity storage elements and have absorbed a coolant. 
     In this electricity storage device, heat generated in the electricity storage elements during charge/discharge is transferred from the outer surfaces of the electricity storage elements to the absorption sheets. When the heat is transferred to the coolant absorbed by the absorption sheets, the coolant is evaporated. At this time, the heat generated in the electricity storage elements is absorbed as evaporation heat of the coolant. The evaporated coolant moves to the upper space in the case, and transfers the heat to a top panel of the case at the inner surface of the top panel. The vapor of the coolant is devolatilized due to a decrease in temperature. The devolatilized coolant falls inside the case due to gravity, and accumulates at the bottom of the case. The coolant accumulating at the bottom of the case is absorbed by the absorption sheets and rises, and then absorbs the heat of the electricity storage elements again. 
     SUMMARY 
     However, with the above-mentioned technique, the absorption sheets are not in contact with connection portions where electrodes of the plurality of electricity storage elements are electrically connected. A relatively large electric current flows through the connection portions. Moreover, since the connection portions have cross sections that are smaller than those of the electricity storage element bodies, their electric resistance is relatively large, and thus they tend to generate heat. Therefore, when the plurality of electricity storage elements are charged/discharged, there is a concern that the connection portions generate heat, and temperature rises locally. 
     The present design was accomplished based on the aforementioned circumstances, and it is an object thereof to suppress a local increase in temperatures of the connection portions where a plurality of electricity storage elements are electrically connected. 
     An electricity storage module according to the present invention design a housing filled with a coolant, a plurality of electricity storage elements that include electrode terminals located above a liquid surface of the coolant and that are accommodated in the housing, and an absorption sheet that absorbs the coolant and is in contact with an outer surface of at least one of the plurality of electricity storage elements, wherein the electrode terminals include connection portions that electrically connect the electrode terminals of the adjacent electricity storage elements of the plurality of electricity storage elements and that are integral with or separate from the electrode terminals, and the absorption sheet includes a contact portion that is in contact with the connection portion. 
     With the above configuration, heat generated in the electricity storage elements that are in contact with the absorption sheet is transferred to the coolant absorbed by the absorption sheet, and the coolant is evaporated due to this heat. As a result, heat generated in the electricity storage elements is absorbed as evaporation heat of the coolant. Moreover, heat generated in the connection portions is transferred to the coolant that has reached the contact portion of the absorption sheet, and the coolant is evaporated due to this heat. As a result, heat generated in the connection portions is absorbed as evaporation heat of the coolant. 
     An electric current that flows through the electricity storage elements flows through the connection portions where the electrode terminals are connected to each other. However, the connection portions have cross sections that are smaller than those of the electricity storage elements. Therefore, the connection portions relatively tend to generate heat, and temperature is likely to rise locally. In this embodiment, the contact portion is configured to come into contact with the connection portion, and therefore, the connection portion can be reliably cooled by the coolant absorbed up to the contact portion. As a result, a local increase in temperature of the connection portion can be suppressed. 
     The following embodiments are preferred as embodiments of the present design. 
     It is preferable that the contact portion is in contact with the connection portion from a side opposite to the electricity storage elements. 
     With the above configuration, the contact portion is configured to be placed on the connection portion from above. On the other hand, the electricity storage elements are arranged at positions below the connection portions. With such a configuration, when the contact portion is brought into contact with the connection portion, interference between the electricity storage element and the contact portion can be prevented. As a result, a step of bringing the contact portion into contact with the connection portion can be simplified. 
     Moreover, it is preferable that the housing includes a case provided with an opening that opens upward, and a lid portion that has a shape following an opening edge of the opening of the case and that closes the opening, and the lid portion includes a heat dissipation fin projecting outward from the housing, and a heat absorption fin projecting inward into the housing. 
     After the coolant absorbs heat generated in the electricity storage elements and the connection portions and is thus evaporated, the coolant rises inside the housing and is in contact with the heat absorption fin that is formed on the lower side of the lid portion. Then, heat is transferred from the vapor of the coolant to the heat absorption fin. Heat transferred to the heat absorption fin is transmitted to the heat dissipation fin, and then dissipated from the heat dissipation fin to the outside. Accordingly, heat absorbed by the coolant is efficiently dissipated to the outside of the housing, and therefore, a local increase in temperatures of the electricity storage elements is further suppressed. 
     It is preferable that the heat absorption fin is arranged above the connection portions. 
     With the above configuration, when the vapor of the coolant comes into contact with the heat absorption fin, heat of the vapor of the coolant is transferred to the heat absorption fin. Then, the coolant is condensed into a liquid form. The devolatilized coolant falls downward from the cooling fin due to gravity. With this embodiment, the cooling fin is arranged above the connection portions, and therefore, the coolant that has fallen from the cooling fin reliably flows down on the connection portions. As a result, the devolatilized coolant first cools the connection portions, and therefore, a local increase in temperatures of the connection portions is further suppressed. 
     With the present design, a local increase in temperatures of the connection portions where a plurality of electricity storage elements are electrically connected can be suppressed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of an electricity storage module according to Embodiment 1. 
         FIG. 2  is a plan view of the electricity storage module. 
         FIG. 3  is a right side view of the electricity storage module in which a case is omitted. 
         FIG. 4  is a front view of the electricity storage module in which a case is omitted. 
         FIG. 5  is a perspective view showing a state in which a plurality of electricity storage elements are connected in series. 
         FIG. 6  is a cross-sectional view taken along line VI-VI in  FIG. 3 . 
         FIG. 7  is a right side view of an absorption sheet. 
         FIG. 8  is a perspective view of the absorption sheet. 
         FIG. 9  is an enlarged view of a circle  40  in  FIG. 6 . 
         FIG. 10  is a perspective view of a separator. 
         FIG. 11  is a plan view of the separator. 
         FIG. 12  is a perspective view showing a state in which the separators and the absorption sheets are lined up and assembled to a wiring member, and then the contact portions are fixed to the connection portions. 
         FIG. 13  is a perspective view showing a state in which the electricity storage elements, the separators, and the absorption sheets are lined up. 
         FIG. 14  is a perspective view showing a state in which the electricity storage elements, the separators, and the absorption sheets are lined up and assembled to the wiring member. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiment 1 
     Embodiment 1 of the present design will be described with reference to  FIGS. 1 to 14 . An electricity storage module  10  according to this embodiment includes a housing  11 , and a plurality of electricity storage elements  12  that are accommodated in the housing  11 . In the following description, the X direction indicates a “right side”, the Y direction indicates a “front side”, and the Z direction indicates an “upper side”. Moreover, where a plurality of members have the same shape, only some of the members may be denoted by reference numerals, and the other members may not be denoted by reference numerals. 
     As shown in  FIGS. 1 to 4 , the housing  11  of the electricity storage module  10  has a substantially rectangular parallelepiped shape as a whole. The housing  11  includes a case  14  provided with an opening  13  that opens upward, and a lid portion  15  that closes the opening  13  of the case  14 . The case  14  includes a bottom wall  16  having a substantially rectangular shape, and side walls  17  that rise upward from the side edges of the bottom wall  16 . The upper ends of the side walls  17  are taken as an opening edge  18  of the opening  13 . 
     The case  14  is made of metal such as aluminum or stainless steel, and can be made of any metal as necessary. A power terminal  19 A of the electricity storage module  10  is provided via a grommet  20 A made of an insulating material (e.g., synthetic resin) at a position that is located near the upper end and front end of a right side wall  17 A of the case  14 . The grommet  20 A achieves liquid tightness between the power terminal  19 A and the right side wall  17 A of the case  14 . Moreover, a power terminal  19 B of the electricity storage module  10  is provided via a grommet  20 B made of an insulating material (e.g., synthetic resin) at a position that is located near the upper end and front end of a left side wall  17 B of the case  14 . The grommet  20 B achieves liquid tightness between the power terminal  19 B and the left side wall  17 B of the case  14 . 
     The lid portion  15  is made of metal such as aluminum or stainless steel, and can be made of any metal as necessary. The lid portion  15  has a substantially rectangular shape as viewed from above, following the shape of the opening  13 . A gap between the lid portion  15  and the upper ends of the side walls  17  of the case  14  is sealed in a liquid-tight manner using a known method such as welding, soldering, or brazing. As a result, a coolant  21  that has been placed in the housing  11  is sealed in the housing  11 . A configuration may also be applied in which a gap between the lid portion  15  and the upper ends of the side walls  17  of the case  14  is sealed via a packing (not shown) in a liquid-tight manner using a known method such as bolting. 
     Insulating liquid can be used as the coolant  21 , and examples thereof include perfluorocarbon, hydrofluoroether, hydrofluoroketone, and fluorine inert liquid. 
     A plurality of (twelve in this embodiment) heat dissipation fins  22  that project upward and extend in a front-rear direction are formed with a constant pitch on the top surface of the lid portion  15 . In addition, a plurality of (twelve in this embodiment) heat absorption fins  23  that project downward and extend in a front-rear direction are formed with a constant pitch on the lower surface of the lid portion  15 . In this embodiment, the pitch between the heat dissipation fins  22  and the pitch between the heat absorption fins  23  are set to the same value, and the heat dissipation fins  22  and the heat absorption fins  23  are formed at corresponding positions on both sides of lid portion  15  in the vertical direction. The lid portion  15  may be formed through extrusion molding or die casting. 
     As shown in  FIG. 5 , the electricity storage element  12  is obtained by sandwiching an electricity storage constituent (not shown) between a pair of laminated sheets  24  having a substantially rectangular shape, and joining the side edges of the pair of laminated sheets  24  in a liquid-tight manner using a known method such as welding. Joined portions  25  projecting outward are formed at the upper edge, lower edge, front end edge, and rear end edge of the laminated sheets  24 . A pair of electrode terminals  26  that is electrically connected to the electricity storage constituent projects upward from the upper end edge of the laminated sheet  24 . The pair of electrode terminals  26  is made of a metal foil. The pair of electrode terminals  26  includes a positive electrode and a negative electrode. A gap between the pair of electrode terminals  26  and the inner surfaces at the upper end edges of the laminated sheets  24  are sealed in a liquid-tight manner. 
     In this embodiment, a secondary battery such as a lithium-ion secondary battery or a nickel-metal hydride secondary battery may be used as the electricity storage element  12 , for example, and a capacitor such as an electric double layer capacitor or a lithium-ion capacitor may be used as the electricity storage element  12 . In this manner, regarding the electricity storage element  12 , any electricity storage element  12  can be selected as necessary. 
     The electricity storage element  12  has a substantially rectangular flat shape as viewed in the left-right direction. A plurality of (six in this embodiment) electricity storage elements  12  are lined up in the left-right direction such that the polarities of the adjacent electrode terminals  26  are different. 
     The electrode terminals  26  to be electrically connected, out of the electrode terminals  26  of adjacent electricity storage elements  12 , are bent in directions in which they come closer to each other, and placed one on top of the other in the vertical direction, and then, in this state, they are electrically connected using a known method such as laser-welding, soldering, or brazing. 
     As shown in  FIG. 5 , the electrode terminal  26  on the rear side of the electricity storage element  12  located furthest to the right is bent toward the left at a substantially right angle. Moreover, the electrode terminal  26  on the rear side of the electricity storage element  12  located at the second position from the right is bent toward the right at a substantially right angle. In this embodiment, the electrode terminals  26  bent in a direction in which they come closer to each other are welded through laser-welding in a state in which they are placed one on top of the other. As a result, the electricity storage element  12  located furthest to the right and the electricity storage element  12  located at the second position from the right are connected in series. Other electricity storage elements  12  are connected to one another in a similar manner, and thus the plurality of electricity storage elements  12  are connected in series. 
     A portion in which the electrode terminals  26  of the adjacent electricity storage elements  12  are connected to each other is taken as a connection portion  27 . In this embodiment, the connection portion  27  is formed by welding the electrode terminals  26 , and therefore, the connection portion  27  is integral with the electrode terminals  26 . It should be noted that the connection portion  27  may also have a configuration in which the electrode terminals  26  of the adjacent electricity storage elements  12  are electrically connected using a conductive member (e.g., busbar) that is a member separate from the electrode terminals  26 . 
     As shown in  FIG. 4 , in a state in which the plurality of electricity storage elements  12  is accommodated in the case  14 , and the lid portion  15  is fixed to the case  14 , the electrode terminals  26  of the electricity storage elements  12  are located above the liquid surface of the coolant  21 . The liquid surface of the coolant  21  can be set at any position in the case  14 . 
     As shown in  FIG. 6 , an absorption sheet  28  is arranged on at least one of the left and right lateral surfaces of the electricity storage element  12  and is in contact with the outer surface of the electricity storage element  12 . In this embodiment, the absorption sheet  28  is arranged on the left lateral surface of the electricity storage element  12  and is in contact therewith, and the absorption sheet  28  is also arranged on the right lateral surface of the electricity storage element  12  and is in contact therewith. The absorption sheet  28  is made of a material that can absorb the coolant  21 . The absorption sheet  28  may be a fabric or a non-woven fabric made of a product obtained by processing a material that can absorb the coolant  21  into a fibrous form. The non-woven fabric may be in the form of a fiber sheet, a web (thin film-like sheet constituted by only fibers), or a batt (blanket-like fiber). A material constituting the absorption sheet  28  may be a natural fiber, a synthetic fiber made of a synthetic resin, or a material using both a natural fiber and a synthetic fiber. 
     As shown in  FIGS. 7 and 8 , the absorption sheet has a substantially rectangular shape as viewed in the left-right direction. The size of the absorption sheet  28  may be such that the absorption sheet  28  comes into contact with one lateral surface (at least one of the left and right lateral surfaces of the electricity storage element  12  in this embodiment) of the electricity storage element  12 . It is preferable that the size of the absorption sheet  28  is substantially the same as that of at least one of the left and right lateral surfaces of the electricity storage element  12 . It is more preferable that the size of the absorption sheet  28  is larger than that of at least one of the left and right lateral surfaces of the electricity storage element  12 . In this embodiment, the absorption sheet  28  is formed to have a size that is substantially the same as those of the left and right lateral surfaces of the electricity storage element  12 . 
     A contact portion  29  projecting upward is formed at at least one end in the front-rear direction of the upper end edge of the absorption sheet  28 . The contact portion  29  is formed in a substantially rectangular shape as viewed in the left-right direction. The contact portion  29  is placed on the connection portion  27  in which the electrode terminals  26  of the adjacent electricity storage elements  12  are connected, and is in contact with this connection portion  27 . In this embodiment, the contact portion  29  is placed, from above, on the connection portion  27  formed through laser-welding of the electrode terminals  26  of the adjacent electricity storage elements  12  placed one on top of the other, and is in contact therewith. 
       FIG. 9  is an enlarged view of a structure in a circle  40  in  FIG. 6 . As shown in  FIG. 9 , two contact portions  29  are placed one on top of the other and arranged on one connection portion  27 . 
     As shown in  FIG. 6 , a plurality of (five in this embodiment) separators  30  are arranged between the plurality of electricity storage elements  12 . As shown in  FIGS. 10 and 11 , each separator  30  is obtained by forming a plurality of recesses and protrusions extending in the vertical direction on both surfaces of a plate material having a substantially rectangular shape. 
     As shown in  FIG. 6 , the recesses and protrusions formed on both of the left and right lateral surfaces of the separator  30  are vertically continuous. The separators  30  are arranged between the plurality of electricity storage elements  12  in such an orientation that the recesses and protrusions extend in the vertical direction. As a result, in the state in which the separators  30  are arranged between the plurality of electricity storage elements  12 , the recesses and protrusions located between the separator  30  and the absorption sheet  28  serve as airways  31  through which the vapor of the coolant  21  flows in the vertical direction. 
     As shown in  FIG. 12 , a wiring member  32  made of an insulating synthetic resin is provided above the plurality of electricity storage elements  12 . The wiring member  32  has a plate shape that is thick in the vertical direction. The wiring member  32  has a substantially rectangular shape as viewed from above, and is formed to be slightly smaller than the lid portion  15 . 
     As shown in  FIGS. 6 and 12 , recesses  33  into which the power terminals  19 A and  19 B of the electricity storage module  10  are to be respectively inserted are formed near the front end of both of the left and right lateral edges of the wiring member  32 . The electrode terminals  26  of the electricity storage elements  12  arranged at both ends in the left-right direction are placed on the power terminals  19 A and  19 B of the electricity storage module  10 . The power terminals  19 A and  19 B are electrically connected to the electrode terminals  26  using a known method such as welding, soldering, or brazing. 
     Two window rows in which a plurality of windows  34 A,  34 B and  34 C are lined up with intervals in the left-right direction are formed, spaced apart in the front-rear direction, in the top surface of the wiring member  32 . A front window row located on the front side includes two windows  34 A located at the left and right, and two windows  34 B located near the center in the left-right direction. The two windows  34 A located at the left and right are formed such that its width dimensions in the left-right direction are smaller than those of the two windows  34 B located near the center in the left-right direction. 
     A rear window row located on the rear side, out of the window rows, includes three windows  34 C. The windows  34 C included in the rear window row all have the same size. 
     The contact portions  29  placed on the connection portions  27  of the electrode terminals  26  are exposed through the two windows  34 B located near the center in the left-right direction in the front window row and the three windows  34 C included in the rear window row. Moreover, the contact portions  29 , which are placed on the electrode terminals  26  placed on the power terminals  19 A and  19 B, are exposed through the two windows  34 A located at both ends in the left-right direction in the front window row. 
     As shown in  FIG. 6 , in the state in which the plurality of electricity storage elements  12  are accommodated in the case  14 , and the lid portion  15  is fixed to the case  14 , the heat absorption fins  23  are located above the contact portions  29  exposed through the windows  34 A,  34 B, and  34 C. 
     Base portions  35  on which the electrode terminals  26  that have been placed one on top of the other are to be mounted are formed below the two windows  34 B located near the center in the left-right direction in the front window row and the three windows  34 C included in the rear window row. The base portions  35  are coupled to the inner lateral surfaces in the front-rear direction of the windows  34 B and  34 C, which are not specifically shown in the drawings. 
     In the lower surface of the wiring member  32 , slits  36  that are vertically in communication with the windows  34 B and  34 C are formed on the lateral sides in the left-right direction of the base portions  35 . The electrode terminals  26  and the contact portions  29  of the absorption sheets  28  are inserted through the slits  36  from below. 
     Next, an example of a process for manufacturing this embodiment will be described. It should be noted that the process for manufacturing this embodiment is not limited to the following description. 
     As shown in  FIG. 13 , the plurality of electricity storage elements  12 , the plurality of absorption sheets  28 , and the plurality of separators  30  are stacked and lined up in the left-right direction. More specifically, absorption sheets  28  are placed on each of the left and right surfaces of one electricity storage element  12 . Six electricity storage elements  12  on which the absorption sheets  28  are placed on the left and right surfaces are produced. Five separators  30  are respectively arranged between the six electricity storage elements  12 . In this state, the electrode terminals  26  that have been vertically placed one on top of the other are laser-welded. As a result, the connection portions  27  are formed on the electrode terminals  26 . 
     As shown in  FIG. 14 , the wiring member  32  is attached to a stack of the plurality of electricity storage elements  12 , the plurality of absorption sheets  28 , and the plurality of separators  30  from above. At this time, the electrode terminals  26  and the contact portions  29  of the absorption sheets  28  are inserted through the slits  36  of the wiring member  32  from below. In this state, the electrode terminals  26  and the contact portions  29  of the absorption sheets  28  project upward from the windows  34 A,  34 B, and  34 C of the wiring member  32 . 
     Next, as shown in  FIG. 12 , the contact portions  29  of the absorption sheets  28  are bent and placed on the connection portions  27  formed on the electrode terminals  26  from above. Then, the contact portions  29  of the absorption sheets  28  are fixed to the connection portions  27  using a known method such as bonding or heat-welding. 
     The case  14 A is filled with a predetermined amount of the coolant  21 . Thereafter, an assembly composed of the electricity storage elements  12  and the wiring member  32  is accommodated in the case  14  from above. Next, the lid portion  15  is placed on the opening edge  18  of the side walls  17  of the case  14  from above, and the lid portion  15  is adhered to the opening edge  18  of the side walls  17  of the case  14  in a liquid-tight manner through laser-welding, for example. As a result, the electricity storage module  10  is completed. 
     Next, the potential operational effects of this embodiment will be described. The electricity storage module  10  according to this embodiment includes a housing  11  filled with a coolant  21 , a plurality of electricity storage elements  12  that include electrode terminals  26  located above a liquid surface of the coolant  21  and that are accommodated in the housing  11 , and an absorption sheet  28  that absorbs the coolant  21  and is in contact with an outer surface of at least one of the plurality of electricity storage elements  12 , wherein the electrode terminals  26  include connection portions  27  that electrically connect the electrode terminals  26  of the adjacent electricity storage elements  12  of the plurality of electricity storage elements  12  and that are integral with or separate from the electrode terminals  26 , and the absorption sheet  28  includes a contact portion  29  that is in contact with the connection portion  27 . 
     With the above configuration, heat generated in the electricity storage elements  12  that are in contact with the absorption sheet  28  is transferred to the coolant  21  absorbed by the absorption sheet  28 , and the coolant  21  is evaporated due to this heat. As a result, heat generated in the electricity storage elements  12  is absorbed as evaporation heat of the coolant  21 . Moreover, heat generated in the connection portions  27  is transferred to the coolant  21  that has reached the contact portion  29  of the absorption sheet  28 , and the coolant  21  is evaporated due to this heat. As a result, heat generated in the connection portions  27  is absorbed as evaporation heat of the coolant  21 . 
     An electric current that flows through the electricity storage elements  12  flows through the connection portions  27  where the electrode terminals  26  are connected to each other. The connection portions  27  have cross sections that are smaller than those of the electricity storage elements  12 . Therefore, since electric resistance of the connection portions  27  is larger than that of the electricity storage elements  12 , heat is relatively likely to be generated, and temperature is likely to rise locally. In this embodiment, the contact portions  29  are configured to come into contact with the connection portions  27 . Therefore, the connection portion  27  can be reliably cooled by the coolant  21  absorbed up to the contact portions  29 . As a result, a local increase in temperature of the connection portions  27  can be suppressed. 
     With this embodiment, each contact portion  29  is in contact with a connection portion  27  from a side opposite to the electricity storage elements  12 . As a result, in this embodiment, the contact portion  29  is configured to be placed on the connection portion  27  from above. On the other hand, the electricity storage elements  12  are arranged at positions below the connection portions  27 . With such a configuration, when the contact portion  29  is brought into contact with the connection portion  27 , interference between the electricity storage elements  12  and the contact portion  29  can be prevented. As a result, a step of bringing the contact portion  29  into contact with the connection portion  27  can be simplified. In this embodiment, the contact portion  29  can be brought into contact with the connection portion  27  through a simple step of bending the contact portion  29 . 
     With this embodiment, the housing  11  includes a case  14  provided with an opening  13  that opens upward, and a lid portion  15  that has a shape following an opening edge  18  of the opening  13  of the case  14  and that closes the opening  13 , and the lid portion  15  includes heat dissipation fins  22  projecting outward from the housing  11 , and heat absorption fins  22  projecting inward into the housing  11 . 
     After the coolant  21  absorbs heat generated in the electricity storage elements  12  and the connection portions  27  and is thus evaporated, the coolant  21  rises inside the housing  11  and is in contact with the heat absorption fins  23  that are formed on the lower side of the lid portion  15 . Then, heat is transferred from the vapor of the coolant  21  to the heat absorption fins  23 . As a result, the coolant  21  is condensed from a gaseous form into a liquid form, and drips downward due to gravity. On the other hand, heat transferred to the heat absorption fins  23  is transmitted to the heat dissipation fins  22 , and then dissipated from the heat dissipation fins  22  to the outside. Accordingly, heat absorbed by the coolant  21  is efficiently dissipated to the outside of the housing  11 , and therefore, a local increase in temperatures of the electricity storage elements  12  is further suppressed. 
     With this embodiment, the heat absorption fins  23  are arranged above the connection portions  27 . Accordingly, when the vapor of the coolant  21  comes into contact with the heat absorption fins  23 , heat of the vapor of the coolant  21  is transferred to the heat absorption fins  23 . Then, the coolant  21  is condensed into a liquid form. The devolatilized coolant  21  falls downward from the cooling fins due to gravity. With this embodiment, the cooling fins are arranged above the connection portions  27 , and therefore, the coolant  21  that has fallen from the cooling fins reliably flows down on the connection portions  27 . As a result, the devolatilized coolant  21  first cools the connection portions  27 , and therefore, a local increase in temperatures of the connection portions  27  is further suppressed. 
     Other Embodiments 
     The present invention is not limited to the embodiment that has been described above with reference to the drawings, and embodiments such as those described below are also included in the technical scope of the present invention, for example. 
     Although the electricity storage element  12  in which the electricity storage constituent is sandwiched between the pair of laminated sheets  24  is used in this embodiment, there is no limitation thereto. A configuration may also be applied in which an electricity storage constituent is accommodated in the housing  11  having any shape such as a cylindrical tube shape, a polygonal tube shape, or a coin shape. 
     Although the configuration in which the electrode terminal  26  is made of a metal foil is applied in this embodiment, there is no limitation thereto. The electrode terminal  26  can be formed in any shape such as a stud bolt shape or a base shape as necessary. 
     Although the pitch between the heat dissipation fins  22  and the pitch between the heat absorption fins  23  are set to the same value in this embodiment, there is no limitation thereto. The pitch between the heat dissipation fins  22  and the pitch between the heat absorption fins  23  may also be set to different values. 
     Although the configuration in which the lid portion  15  includes both of the dissipation fins  22  and the heat absorption fins  23  is applied in this embodiment, there is no limitation thereto. A configuration in which the lid portion  15  is provided with no heat dissipation fins  22  may also be applied, and a configuration in which the lid portion  15  is provided with no heat absorption fins  23  may also be applied. 
     Although the configuration in which the plurality of electricity storage elements  12  are connected in series in this embodiment, there is no limitation thereto. The plurality of electricity storage elements  12  may also be connected in parallel. 
     Although the configuration in which the absorption sheets  28  come into contact with both of the left and right surfaces of the electricity storage element  12 , there is no limitation thereto. A configuration in which the absorption sheet  28  is in contact with one of the left and right lateral surfaces of the electricity storage element  12  may also be applied. When the housing  11  of the electricity storage elements  12  has a polygonal tube shape, for example, a configuration in which the absorption sheet  28  is in contact with any surface of the housing  11  may also be applied. 
     It is to be understood that the foregoing is a description of one or more preferred exemplary embodiments of the invention. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to come within the scope of the appended claims. 
     As used in this specification and claims, the terms “for example,” “e.g.,” “for instance,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation. 
     LIST OF REFERENCE NUMERALS 
       10 : Electricity storage module 
       11 : Housing 
       12 : Electricity storage element 
       13 : Opening 
       14 : Case 
       15 : Lid portion 
       18 : Opening edge 
       21 : Coolant 
       22 : Heat dissipation fin 
       23 : Heat absorption fin 
       26 : Electrode terminal 
       27 : Connection portion 
       28 : Absorption sheet 
       29 : Contact portion