Patent Publication Number: US-2023138950-A1

Title: Energy storage apparatus

Description:
TECHNICAL FIELD 
     The present invention relates to an energy storage apparatus including an energy storage device and a spacer disposed adjacent to the energy storage device. 
     BACKGROUND ART 
     Conventionally, there has been known an energy storage apparatus including an energy storage device and a spacer disposed adjacent to the energy storage device. Patent Document 1 discloses an assembled battery including a plurality of battery cells each having a metal case. In this assembled battery, the plurality of battery cells are stacked with a separator of an insulating material interposed therebetween. The separator has an insulating plate portion that insulates adjacent battery cells from each other, and a peripheral wall provided on a peripheral portion of the insulating plate portion. A bottom peripheral wall of the peripheral wall which is disposed on a bottom surface side of the battery cell has a convex part which projects downward. According to Patent Document 1, it is described that a more preferable insulation state is realized since the convex part is disposed so that the battery cell is separated from a plate such as a bottom plate or a cooling plate of a case disposed below the assembled battery. 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document 1: JP-A-2012-119156 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     As an energy storage apparatus, a structure capable of improving safety by improving fixability and electric insulation of an energy storage device is required. 
     An object of the present invention is to provide an energy storage apparatus with improved safety. 
     Means for Solving the Problems 
     An energy storage apparatus according to one aspect of the present invention includes: an energy storage device; a spacer disposed adjacent to the energy storage device; and an outer case which accommodates the energy storage device and the spacer, in which the spacer includes a projecting portion which projects from a bottom surface of the energy storage device, and an inner surface of the outer case which faces the bottom surface of the energy storage device is provided with an accommodating portion which accommodates the projecting portion, and a placement surface portion which is disposed adjacent to the accommodating portion in an arrangement direction of the spacer and the energy storage device and on which the bottom surface of the energy storage device is placed. 
     Advantages of the Invention 
     According to the energy storage apparatus of the present invention, the safety can be improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view showing an external appearance of an energy storage apparatus according to an embodiment. 
         FIG.  2    is an exploded perspective view of the energy storage apparatus according to the embodiment. 
         FIG.  3    is an exploded perspective view of an energy storage unit according to the embodiment. 
         FIG.  4    is a cut view showing a part of an internal configuration of an outer case according to the embodiment. 
         FIG.  5 A  is a perspective view showing an external appearance of a spacer according to the embodiment. 
         FIG.  5 B  is a perspective view showing an external appearance of a spacer according to the embodiment. 
         FIG.  6    is a perspective view showing an external appearance of an inner surface of the outer case according to the embodiment. 
         FIG.  7 A  is a first cross-sectional view of the inner surface of the outer case according to the embodiment. 
         FIG.  7 B  is a second cross-sectional view of the inner surface of the outer case according to the embodiment. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     When the spacer has the convex part which projects downward as in the separator (spacer) in the conventional assembled battery (energy storage apparatus), the presence of the convex part becomes an obstacle for fixing the bottom surface of the energy storage device to a bottom wall of an outer case, and it becomes difficult to fix the energy storage device to the outer case. This is not preferable from the viewpoint of safety of the energy storage apparatus. Therefore, it is conceivable to remove the convex part (projecting portion) which projects downward and is provided in the lower portion of the spacer. However, since such a projecting portion is also related to reliability of electric insulation between two members adjacent to each other with the spacer interposed therebetween, it is not preferable to simply remove the projecting portion from the viewpoint of safety of the energy storage apparatus. 
     An object of the present invention is to provide an energy storage apparatus with improved safety. 
     An energy storage apparatus according to one aspect of the present invention includes: an energy storage device; a spacer disposed adjacent to the energy storage device; and an outer case which accommodates the energy storage device and the spacer, in which the spacer includes a projecting portion which projects from a bottom surface of the energy storage device, and an inner surface of the outer case which faces the bottom surface of the energy storage device is provided with an accommodating portion which accommodates the projecting portion, and a placement surface portion which is disposed adjacent to the accommodating portion in an arrangement direction of the spacer and the energy storage device and on which the bottom surface of the energy storage device is placed. 
     With such a configuration, the energy storage device and another member (another energy storage device or the like) disposed adjacent to the energy storage device can be insulated from each other by the spacer, and a creepage distance between the bottom surface of the energy storage device and the another member can be increased by providing the projecting portion. Therefore, the safety is improved. Since the projecting portion is accommodated in the accommodating portion, the projecting portion is accommodated in an aspect in which the projecting portion does not become an obstacle in the inside of the outer case. Accordingly, the bottom surface of the energy storage device can be directly or indirectly placed on and adhered to the placement surface portion, for example, and by providing a groove in the inner surface, the accommodating portion can be configured by the groove. That is, the energy storage apparatus with improved safety can be obtained with a simple configuration. By fixing the energy storage device to the placement surface portion by adhesion or the like, it is also possible to improve vibration resistance or impact resistance of the energy storage apparatus, and this also contributes to safety of the energy storage apparatus. As described above, according to the energy storage apparatus of the present aspect, the safety can be improved. 
     The projecting portion may include a restricting portion which is brought into contact with the bottom surface of the energy storage device, the restricting portion restricting a position of the bottom surface. 
     In this case, when the spacer includes the projecting portion which projects from the bottom surface of the energy storage device, the spacer cannot be usually positioned by a method of aligning the lower end of the spacer with the position of the bottom surface of the energy storage device. However, in the spacer according to the present aspect, since the projecting portion includes the restricting portion, the bottom surface of the energy storage device can be brought into contact with the restricting portion to easily position the spacer with respect to the energy storage device. As a result, the effect of increasing the creepage distance by the projecting portion can be reliably obtained. 
     The accommodating portion may include a first accommodating portion which accommodates a portion of the projecting portion, the portion including the restricting portion, and a second accommodating portion which accommodates a portion of the projecting portion, the portion not including the restricting portion. 
     According to this configuration, in a top view, the portion of the projecting portion where the restricting portion that is a wide portion is present can be accommodated in the first accommodating portion having a wide width, and a narrow portion without the restricting portion can be accommodated in the second accommodating portion having a narrow width. That is, in a top view, since the projecting portion having irregularities by including the restricting portion can be accommodated in the accommodating portion having a shape corresponding to the irregularities. Therefore, rattling of the projecting portion is suppressed, whereby the stability of the position of the spacer is improved. As a result, the electric insulation performance of the spacer is maintained, and the position restriction of the energy storage device by the spacer is reliably performed. 
     The projecting portion may extend along a peripheral edge portion of the bottom surface of the energy storage device, and the accommodating portion may extend along the projecting portion on the inner surface of the outer case. 
     With such a configuration, the projecting portion is provided in a range where the bottom surface of the energy storage device extends, and the entire region of the projecting portion can be accommodated in the accommodating portion. With such a configuration, it is possible to increase a creepage distance between the bottom surface of the energy storage device and another member disposed on an opposite side with the spacer interposed therebetween in a wide range. This contributes to further improvement of safety. 
     Hereinafter, an energy storage apparatus according to an embodiment of the present invention (including modification examples thereof) will be described with reference to the drawings. The embodiment described below describes a comprehensive or specific example. The numerical values, shapes, materials, components, positions for arranging the components and connection forms of the components, manufacturing processes, the order of the manufacturing processes, and the like described in the following embodiment are merely examples, and are not intended to limit the present invention. In each drawing, dimensions and the like are not strictly shown. 
     In the following description and drawings, an arrangement direction of a pair of (positive electrode side and negative electrode side) electrode terminals in one energy storage device, a facing direction of short side surfaces of a case of the energy storage device, or an arrangement direction of a pair of side plates is defined as an X-axis direction. An arrangement direction of a plurality of energy storage devices, a facing direction of long side surfaces of the case of the energy storage device, or an arrangement direction of a pair of end plates is defined as a Y-axis direction. An arrangement direction of an outer case body and a lid body of the energy storage apparatus, an arrangement direction of a case body and a lid portion of the energy storage device, an arrangement direction of the energy storage device and a bus bar, or a vertical direction is defined as a Z-axis direction. The X-axis direction, the Y-axis direction, and the Z-axis direction are directions intersecting (orthogonal in the present embodiment) each other. Although it is considered that the Z-axis direction may not be the vertical direction depending on the usage mode, the Z-axis direction will be described below as the vertical direction for convenience of description. 
     In the following description, the X-axis positive direction indicates an arrow direction of the X axis, and the X-axis negative direction indicates a direction opposite to the X-axis positive direction. The same applies to the Y-axis direction and the Z-axis direction. Expressions indicating relative directions or postures, such as parallel and orthogonal include cases of being not strictly the directions or postures. Two directions being orthogonal to each other not only means that the two directions are completely orthogonal to each other, but also means that the two directions are substantially orthogonal to each other, that is, a difference of about several percent is allowed. 
     EMBODIMENT 
     1. General Description of Energy Storage Apparatus 
     First, general description of an energy storage apparatus  10  according to the present embodiment will be made.  FIG.  1    is a perspective view showing an external appearance of the energy storage apparatus  10  according to the embodiment.  FIG.  2    is an exploded perspective view of the energy storage apparatus  10  according to the embodiment.  FIG.  3    is an exploded perspective view of an energy storage unit  200  according to the embodiment. 
     The energy storage apparatus  10  is an apparatus capable of charging electricity from the outside and discharging electricity to the outside, and has a substantially rectangular parallelepiped shape in the present embodiment. The energy storage apparatus  10  is a battery module (assembled battery) used for power storage application, power supply application, or the like. Specifically, the energy storage apparatus  10  is used as a battery or the like for driving or starting an engine of a moving body such as an automobile, a motorcycle, a watercraft, a ship, a snowmobile, an agricultural machine, a construction machine, or a railway vehicle for an electric railway. Examples of the automobile include an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and a gasoline vehicle. Examples of the railway vehicle for an electric railway include a train, a monorail, and a linear motor car. The energy storage apparatus  10  can also be used as a stationary battery or the like used for home use, a generator, or the like. 
     As shown in  FIG.  1   , the energy storage apparatus  10  includes an outer case  100 . As shown in  FIG.  2    and  FIG.  3   , the energy storage unit  200  having an energy storage device array  201  including a plurality of energy storage devices  210  is disposed in the inside of the outer case  100 . In addition to the above-mentioned components, the energy storage apparatus  10  may include a bus bar frame on which a bus bar is placed, a circuit board for monitoring a charged state and a discharged state of the energy storage devices  210 , electric devices such as a fuse, a relay, and a connector, and an exhaust portion for exhausting a gas discharged from the energy storage devices  210  outward from the outer case  100 . 
     The energy storage unit  200  includes the energy storage device array  201  in which the plurality of energy storage devices  210  are arranged, a plurality of spacers  300  ( 301  and  302 ), a pair of end plates  400 , and a pair of side plates  500 . The plurality of energy storage devices  210  are connected in series by a plurality of bus bars (not shown). 
     The outer case  100  is a case (module case) having a box shape (substantially rectangular parallelepiped shape) which forms an outer case of the energy storage apparatus  10 . That is, the outer case  100  fixes the energy storage unit  200  and the like at a predetermined position and protects the energy storage unit  200  from an impact or the like. The outer case  100  is formed of an insulating member such as polycarbonate (PC), polypropylene (PP), polyethylene (PE), polystyrene (PS), a polyphenylene sulfide resin (PPS), polyphenylene ether (PPE (including modified PPE)), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyether ether ketone (PEEK), tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene (PTFE), polyether sulfone (PES), an ABS resin, or a composite material thereof, or an insulation-coated metal. With such a configuration, the outer case  100  prevents the energy storage devices  210  and the like from coming into contact with an external metal member or the like. The outer case  100  may be formed of a conductive member such as metal as long as the electric insulation of the energy storage devices  210  and the like is maintained. 
     The outer case  100  includes an outer case body  110  which forms a body of the outer case  100  and an outer case lid body  120  which forms a lid body of the outer case  100 . The outer case body  110  is a bottomed rectangular cylindrical housing (casing) in which an opening is formed, and accommodates the energy storage devices  210  and the like therein. The outer case lid body  120  is a flat rectangular member which closes the opening of the outer case body  110 . The outer case lid body  120  is joined to the outer case body  110  by an adhesive, heat sealing, ultrasonic welding, or the like. The outer case lid body  120  is provided with a positive electrode external terminal  121  and a negative electrode external terminal  122 . The positive electrode external terminal  121  is electrically connected to an electrode terminal  220  which is a total positive terminal of the energy storage unit  200 . The negative electrode external terminal  122  is electrically connected to an electrode terminal  220  which is a total negative terminal of the energy storage unit  200 . The energy storage apparatus  10  charges electricity from the outside and discharges electricity to the outside through the positive electrode external terminal  121  and the negative electrode external terminal  122 . 
     The energy storage device  210  is a secondary battery (battery cell) capable of charging and discharging electricity, and more specifically, is a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery. The energy storage device  210  has a flat rectangular parallelepiped shape (prismatic shape), and in the present embodiment, four energy storage devices  210  are arranged side by side in the Y-axis direction. The size and shape of the energy storage devices  210  and the number of the arranged energy storage devices  210  are not limited, and only one energy storage device  210  may be arranged. The energy storage device  210  is not limited to the nonaqueous electrolyte secondary battery, and may be a secondary battery other than the nonaqueous electrolyte secondary battery, or may be a capacitor. The energy storage device  210  may be not a secondary battery but a primary battery that can use stored electricity unless being charged by a user. 
     The energy storage device  210  according to the present embodiment includes a case  211  and the pair of (positive electrode side and negative electrode side) electrode terminals  220  (see  FIG.  3   ). An electrode assembly, a pair of current collectors, an electrolyte solution (nonaqueous electrolyte), and the like are accommodated in the case  211 , and a gasket is disposed between the case  211  and the electrode terminal  220  and the current collector, but these are not shown. A type of the electrolyte solution is not particularly limited as long as performance of the energy storage device  210  is not impaired, and various types of electrolyte solutions can be selected. In addition to the above-mentioned configuration, the energy storage device  210  may include a spacer disposed on a side or the like of the current collector, an insulating sheet which covers an outer surface of the case  211 , and the like. 
     The case  211  is a case having a rectangular parallelepiped shape (prismatic shape) including a container body in which an opening is formed and a lid portion that closes the opening of the case body, and is formed of metal such as stainless steel, aluminum, an aluminum alloy, iron, or a plated steel plate. In the present embodiment, as shown in  FIG.  3   , the case  211  is disposed in a posture in which long side surfaces  211   b  face the Y-axis direction and short side surfaces  211   c  face the X-axis direction, that is, a posture in which the pair of long side surfaces  211   b  face each other in the Y-axis direction and the pair of short side surfaces  211   c  face each other in the X-axis direction. The surface (lid portion) of the case  211  on the Z-axis positive direction side is provided with a gas release valve  230  that releases the pressure when the pressure in the case  211  increases (see  FIG.  3   ). That is, in the case  211 , the gas release valve  230  is disposed at a position facing a bottom surface  211   a  which is a surface of the case  211  on the Z-axis negative direction side. 
     The electrode terminal  220  is a terminal (positive electrode terminal or negative electrode terminal) of the energy storage device  210  disposed on the surface (lid portion) of the case  211  on the Z-axis positive direction side, and is electrically connected to a positive electrode plate or a negative electrode plate of the electrode assembly via the current collector. That is, each of the pair of electrode terminals  220  is a metal member for leading out electricity stored in the electrode assembly to a space outward from the energy storage device  210  and for introducing electricity into a space inside the energy storage device  210  so as to store electricity in the electrode assembly. The electrode terminals  220  are formed of aluminum, an aluminum alloy, copper, a copper alloy, or the like. 
     The electrode assembly is an energy storage element (power generating element) formed by stacking the positive electrode plate, the negative electrode plate, and a separator. The positive electrode plate is obtained by forming a positive active material layer on a positive electrode substrate layer which is a current collecting foil made of metal such as aluminum or an aluminum alloy. The negative electrode plate is obtained by forming a negative active material layer on a negative electrode substrate layer which is a current collecting foil made of metal such as copper or a copper alloy. As the active material used for the positive active material layer and the negative active material layer, a known material can be appropriately used as long as it can occlude and release lithium ions. The electrode assembly may be an electrode assembly in any form such as a winding-type electrode assembly formed by winding plates (a positive electrode plate and a negative electrode plate), a stacking-type (a stacked-type) electrode assembly formed by stacking a plurality of plate-shaped plates, or a bellows-type electrode assembly formed by folding plates in a bellows shape. 
     The current collector is a conductive member (a positive electrode current collector or a negative electrode current collector) electrically connected to the electrode terminal  220  and the electrode assembly. The positive electrode current collector is formed of aluminum, an aluminum alloy, or the like similarly to the positive electrode substrate layer of the positive electrode plate, and the negative electrode current collector is formed of copper, a copper alloy, or the like similarly to the negative electrode substrate layer of the negative electrode plate. 
     The spacer  300  (spacer  301 ,  302 ) is a rectangular plate-like member which is disposed on a side (the Y-axis positive direction or the Y-axis negative direction) of the energy storage device  210  and electrically insulates the energy storage device  210  from another member. To be more specific, the spacer  301  is a member which is disposed between two energy storage devices  210  adjacent to each other and electrically insulates the two energy storage devices  210  from each other, and is a member called an inter-cell spacer. The spacer  302  is a member called an end spacer, and is a member which is disposed between the energy storage device  210  at the end portion and the end plate  400  and electrically insulates the energy storage device  210  at the end portion and the end plate  400  from each other. Each of the spacers  301  and  302  is disposed so as to cover both sides (short side surface  211   c  sides) of the energy storage device  210  in the X-axis direction, and electrically insulates the energy storage device  210  from the side plates  500 . 
     In the present embodiment, the three spacers  301  and the two spacers  302  are arranged corresponding to the four energy storage devices  210 , but when the number of the energy storage devices  210  is other than four, the number of the spacers  301  is also appropriately changed according to the number of the energy storage devices  210 . The spacer  300  is formed of any electrically insulating resin material or the like that can be used for the outer case  100 . In the present embodiment, the spacer  300  has a portion which projects downward from the bottom surface of the energy storage device  210  located on the side. With such a configuration, an electric insulation between two energy storage devices  210  adjacent to each other with the spacer  300  interposed therebetween or between the energy storage device  210  and the end plate  400  is enhanced. Details of the spacer  300  will be described later with reference to  FIGS.  4  to  7 B . 
     The end plates  400  and the side plates  500  are binding members which press (bind) the energy storage device array  201  from the outside in the arrangement direction (Y-axis direction) of the energy storage devices  210  in the energy storage device array  201 . That is, the pair of end plates  400  sandwich the energy storage device array  201  from both sides in the arrangement direction, and the pair of side plates  500  apply a binding force to the pair of end plates  400 . With such a configuration, the respective energy storage devices  210  included in the energy storage device array  201  are pressed (bound) from both sides in the arrangement direction. 
     In the present embodiment, the side plate  500  is connected (joined) to the end plates  400  by a plurality of nuts  500   a  arranged in the Z-axis direction (see  FIG.  3   ). Specifically, the nuts  500   a  are screwed with screw portions of the end plates  400  penetrating the side plate  500  and are fastened to the screw portions. The end plate  400  and the side plate  500  are formed of metal such as iron, stainless steel, or an aluminum alloy. 
     In the present embodiment, a reinforcing member  40  is disposed outward from the outer case  100 . The reinforcing member  40  is a member formed of a material having high strength such as iron, and has a function of enhancing impact resistance and the like of the energy storage apparatus  10 . In the present embodiment, as shown in  FIG.  2   , the reinforcing member  40  is disposed along a bottom wall  115  of the outer case  100 , and the reinforcing member  40  is fixed to the outer case  100  by four bolts  80 . 
     2. Structure of Spacer and its Periphery 
     Next, the structure of the spacer  300  and its periphery will be described with reference to  FIGS.  4  to  7 B .  FIG.  4    is a cut view showing a part of an internal configuration of the outer case  100  according to the embodiment.  FIG.  4    shows the outer case body  110  in a state where a part of the outer case body  110  is cut along a YZ plane parallel to a line IV-IV in  FIG.  2    and the energy storage unit  200  is floated from the bottom wall  115  of the outer case body  110 .  FIG.  5 A  is a perspective view showing an external appearance of the spacer  301  according to the embodiment, and  FIG.  5 B  is a perspective view showing an external appearance of the spacer  302  according to the embodiment.  FIG.  6    is a perspective view showing an external appearance of an inner surface  113  of the outer case  100  which faces the bottom surfaces  211   a  of the energy storage devices  210  according to the embodiment.  FIG.  7 A  is a first cross-sectional view of the inner surface  113  of the outer case  100  according to the embodiment, and  FIG.  7 B  is a second cross-sectional view of the inner surface  113 .  FIG.  7 A  shows a part of a cross section of the energy storage apparatus  10  in a YZ plane passing through a line VIIA-VIIA of  FIG.  6   .  FIG.  7 B  shows a part of a cross section of the energy storage apparatus  10  in a YZ plane passing through a line VIIB-VIIB of  FIG.  6   . 
     As shown in  FIG.  4   , the energy storage unit  200  is placed on the inner surface  113  facing the bottom surfaces  211   a  of the energy storage devices  210  in the inside of the outer case  100 . The inner surface  113  is an inner surface (a surface of the outer case  100  on the inner side) of the bottom wall  115  of the outer case  100  (outer case body  110 ). To be more specific, the inner surface  113  has placement surface portions  113   a  on which the energy storage devices  210  are placed and fixing surface portions  113   b  formed with through holes through which the bolts  80  pass. The bolts  80  penetrate the through holes of the bottom wall  115  of the outer case  100  and are screwed into screw holes of the reinforcing member  40  to fix the reinforcing member  40  to the outer case  100 . 
     In the present embodiment, the spacer  300  is disposed on the long side surface  211   b  (see  FIG.  3   ) side of the energy storage device  210  included in the energy storage unit  200 , and the spacer  300  has a projecting portion which projects downward from the bottom surface  211   a  of the energy storage device  210 . To be more specific, as shown in  FIG.  5 A  and  FIG.  7 A , the spacer  301  disposed between two energy storage devices  210  adjacent to each other has a spacer body  301   a  and a projecting portion  310  formed on a lower end portion of the spacer body  301   a . As shown in  FIG.  5 B  and  FIG.  7 A , the spacer  302  disposed between the energy storage device  210  and the end plate  400  has a spacer body  302   a  and a projecting portion  320  formed on a lower end portion of the spacer body  302   a.    
     Since the spacer  301  has the projecting portion  310 , a creepage distance between the bottom surfaces  211   a  of the two energy storage devices  210  adjacent to each other is increased at the lower end portion of the spacer body  301   a  as compared with a case where the spacer  301  does not have the projecting portion  310 . That is, the electric insulation between the cases  211  of the two energy storage devices  210  adjacent to each other is improved. Since the spacer  302  has the projecting portion  320 , a creepage distance between the energy storage device  210  and the end plate  400  is also increased. As a result, the electric insulation between the case  211  of the energy storage device  210  and the end plate  400  is improved. 
     However, while the effect of increasing the creepage distance can be obtained by the projecting portions  310  and  320 , in the energy storage unit  200 , the projecting portions  310  and  320  project downward from the plurality of bottom surfaces  211   a  arranged flush with each other in the Y-axis direction. That is, when the energy storage unit  200  is placed on a simple flat surface, the energy storage unit  200  is supported by the projecting portions  310  and  320 , and it is difficult to stably support the energy storage unit  200  by the flat surface. 
     Therefore, in the present embodiment, accommodating portions are provided on the inner surface  113  of the outer case  100  so as to accommodate the projecting portions  310  and  320  disposed so as to project downward from the bottom surface  211   a  as described above. To be more specific, as shown in  FIG.  6   ,  FIG.  7 A , and  FIG.  7 B , the inner surface  113  of the outer case  100  is provided with accommodating portions  111  which each accommodate the projecting portion  310  of the spacer  301  and accommodating portions  112  which each accommodate the projecting portion  320  of the spacer  302 . With such a configuration, the bottom surface  211   a  of each of the plurality of energy storage devices  210  can be brought into contact with the inner surface  113  and hence, the energy storage unit  200  is stably supported on the inner surface  113  of the outer case  100 . To be more specific, in the present embodiment, the bottom surface  211   a  of each of the plurality of energy storage devices  210  is adhered and fixed to the inner surface  113 . More specifically, as shown in  FIG.  7 A  and  FIG.  7 B , the placement surface portion  113   a  is disposed adjacent to the accommodating portion  111  in the arrangement direction of the spacer  301  and the energy storage device  210 . By disposing an adhesive  90  between the placement surface portion  113   a  and the bottom surface  211   a  of the energy storage device  210 , the bottom surface  211   a  of the energy storage device  210  is fixed to the placement surface portion  113   a . With such a configuration, each of the plurality of energy storage devices  210  is firmly fixed to the outer case  100 . 
     Each of the projecting portions  310  and  320  has a portion which restricts a position of the energy storage device  210 . To be more specific, as shown in  FIG.  5 A  and  FIG.  7 A , the projecting portion  310  of the spacer  301  has restricting portions  311  which are brought into contact with the bottom surfaces  211   a  of the energy storage devices  210  disposed adjacently to the spacer  301 . That is, the projecting portion  310  has the restricting portions  311  on both sides in the Y-axis direction. As shown in  FIG.  5 B  and  FIG.  7 A , the projecting portion  320  of the spacer  302  has restricting portions  322  which are brought into contact with the bottom surface  211   a  of the energy storage device  210  disposed adjacently to the spacer  302 . As shown in  FIGS.  7 A and  7 B , the projecting portion  320  has a facing portion  321  disposed to face the end surface of the end plate  400  adjacent to the spacer  302 . 
     In this manner, the projecting portion  310  has the restricting portions  311 , and the projecting portion  320  has the restricting portions  322 . With such a configuration, the two energy storage devices  210  adjacent to each other and the spacer  301  disposed between the two energy storage devices  210  can be easily positioned with respect to one another in the Z-axis direction. The energy storage device  210  at the end portion of the energy storage device array  201  and the spacer  302  adjacent to the energy storage device  210  can be easily positioned with respect to one another in the Z-axis direction. Since the projecting portion  310  has the restricting portions  311 , a creepage distance between the cases  211  of the two energy storage devices  210  adjacent to each other with the spacer  301  having the projecting portion  310  interposed therebetween can be further increased. Since the projecting portion  320  has the restricting portions  322  and the facing portion  321 , a creepage distance between the energy storage device  210  and the end plate  400  adjacent to each other with the spacer  302  having the projecting portion  320  interposed therebetween can be further increased. 
     As shown in  FIG.  5 A , the projecting portion  310  of the spacer  301  has the restricting portions  311  only at both end portions in the X-axis direction. With such a configuration, a wide range of the bottom surface  211   a  which is brought into contact with the restricting portion  311  can be used as an adhesion surface (fixing surface) which is adhered to the inner surface  113  (placement surface portion  113   a ) of the outer case  100 . That is, in the present embodiment, the accommodating portion  111  which accommodates the projecting portion  310  is also formed to have a width corresponding to the presence or absence of the restricting portions  311 . Specifically, as shown in  FIGS.  6 ,  7 A, and  7 B , the accommodating portion  111  includes first accommodating portions  111   a  which accommodate portions of the projecting portion  310  having the restricting portions  311  and a second accommodating portion  111   b  which accommodates a portion of the projecting portion  310  not having the restricting portions  311 . On the bottom surface  211   a  of the energy storage device  210  disposed adjacently to the spacer  302 , a portion which is brought into contact with the restricting portion  322  is not fixed to the placement surface portion  113   a  as shown in  FIG.  7 A . However, in the portion of the projecting portion  320  where the restricting portion  322  is not formed, the bottom surface  211   a  of the energy storage device  210  disposed adjacently to the spacer  302  can be fixed to the placement surface portion  113   a  by the adhesive  90  as shown in  FIG.  7 B . Accordingly, out of the four energy storage devices  210  included in the energy storage device array  201 , the energy storage devices  210  at both ends can be fixed to the placement surface portions  113   a  of the inner surface  113  of the outer case  100  with the adhesives  90  although an adhesion area is small compared to the two energy storage devices  210  therebetween. 
     In the present embodiment, as shown in  FIG.  6    and  FIG.  7 A , a placement surface rib  113   c  is provided on the placement surface portions  113   a  so as to surround an aggregate region of the four placement surface portions  113   a  divided by the three accommodating portions  111 . This prevents the adhesives  90  before solidification from flowing out of the aggregate region of the four placement surface portions  113   a . The placement surface rib  113   c  equalizes the height (width in the Z-axis direction) of the gap between the bottom surface  211   a  and the placement surface portion  113   a  in the aggregate region. Accordingly, the adhesive  90  can be more reliably disposed in a range of the bottom surface  211   a  of each of the plurality of energy storage devices  210  which faces the placement surface portion  113   a . That is, the effectiveness of fixing the plurality of energy storage devices  210  using the adhesives  90  is improved. 
     3. Description of Effects 
     As described above, the energy storage apparatus  10  according to the embodiment of the present invention includes the energy storage devices  210 , the outer case  100  which accommodates the energy storage devices  210 , and the spacers  301  disposed adjacent to the energy storage devices  210 . The spacer  301  includes the projecting portion  310  which projects downward from the bottom surface  211   a  of the energy storage device  210 . The inner surface  113  of the outer case  100  is provided with the accommodating portions  111  which each accommodate the projecting portion  310 , and the placement surface portions  113   a  each disposed adjacent to the accommodating portion  111  in the arrangement direction of the spacer  301  and the energy storage device  210  and on which the bottom surface  211   a  of the energy storage device  210  is placed. The same applies to the spacer  302 , and the spacer  302  includes the projecting portion  320  which projects downward from the bottom surface  211   a  of the energy storage device  210 . The inner surface  113  of the outer case  100  is provided with the accommodating portions  112  which each accommodate the projecting portion  320 , and the placement surface portions  113   a  each disposed adjacent to the accommodating portion  112  in the arrangement direction of the spacer  302  and the energy storage device  210  and on which the bottom surface  211   a  of the energy storage device  210  is placed (see  FIG.  7 B ). 
     With such a configuration, the energy storage device  210  and another member (the energy storage device  210  or the end plate  400 ) disposed adjacent to the energy storage device  210  can be insulated from each other by the spacer  301  or  302 . By disposing the projecting portion  310  or  320 , a creepage distance between the bottom surface  211   a  of the energy storage device  210  and the another member can be increased. Therefore, the safety of the energy storage apparatus  10  is improved. Since the projecting portions  310  and  320  are accommodated in the accommodating portions  111  and  112 , the projecting portions  310  and  320  are accommodated in an aspect in which the projecting portions  310  and  320  do not become an obstacle in the inside of the outer case  100 . Accordingly, the bottom surface  211   a  of the energy storage device  210  can be directly or indirectly placed on and adhered to the placement surface portion  113   a , for example. As shown in  FIG.  6   , by providing grooves in the inner surface  113 , the accommodating portions  111  and  112  can be configured by the grooves. That is, the energy storage apparatus  10  with improved safety can be obtained with a simple configuration. By fixing the energy storage device  210  to the placement surface portion  113   a  with the adhesive  90 , it is also possible to improve vibration resistance or impact resistance of the energy storage apparatus  10 , and this also contributes to safety of the energy storage apparatus  10 . As described above, according to the energy storage apparatus  10  of the present embodiment, the safety can be improved. 
     In the present embodiment, the projecting portion  310  has the restricting portions  311  which are each brought into contact with the bottom surface  211   a  of the energy storage device  210  to restrict the position of the bottom surface  211   a . The projecting portion  320  also includes the restricting portions  322  which are brought into contact with the bottom surface  211   a  of the energy storage device  210 , the restricting portion restricting the position of the bottom surface  211   a.    
     In general, when the spacer includes a projecting portion which projects from the bottom surface  211   a  of the energy storage device  210 , the spacer cannot be positioned by a method of aligning the lower end of the spacer with the position of the bottom surface  211   a  of the energy storage device  210 . However, in the spacer  301  according to the present aspect, since the projecting portion  310  includes the restricting portions  311 , the bottom surface  211   a  of the energy storage device  210  can be brought into contact with the restricting portions  311  to easily position the spacer  301  with respect to the energy storage device  210 . As a result, the effect of increasing the creepage distance by the projecting portion  310  can be reliably obtained. The same applies to the spacer  302 , and when the restricting portions  322  position the energy storage device  210  disposed adjacently to the spacer  302 , the effect of increasing the creepage distance by the projecting portion  320  can be reliably obtained. 
     In the present embodiment, the accommodating portion  111  includes the first accommodating portions  111   a  which accommodate a portion of the projecting portion  310 , the portions including the restricting portions  311  and the second accommodating portion  111   b  which accommodates a portion of the projecting portion  310 , the portion not including the restricting portions  311 . 
     In the present embodiment, as shown in  FIG.  6   , in a top plan view (as viewed in the Z-axis positive direction), portions of the projecting portion  310  where the restricting portions  311  that are wide portions are present are accommodated in the first accommodating portions  111   a  having a wide width. In the projecting portion  310 , a narrow portion without the restricting portions  311  is accommodated in the second accommodating portion  111   b  having a narrow width. That is, in a top view, since the projecting portion  310  having irregularities by including the restricting portions  311  can be accommodated in the accommodating portion  111  having a shape corresponding to the irregularities. Therefore, rattling of the projecting portion  310  is suppressed, whereby the stability of the position of the spacer  301  is improved. As a result, the electric insulation performance of the spacer  301  is maintained, and the position restriction of the energy storage device  210  by the spacer  301  is reliably performed. The area of the placement surface portion  113   a  located adjacent to the accommodating portion  111  can be increased as compared with a case where the width of the accommodating portion  111  in the Y-axis direction is constant (the same width as the first accommodating portion  111   a ) in the extending direction (X-axis direction) of the accommodating portion  111 . With such a configuration, an adhesion area between the bottom surface  211   a  of the energy storage device  210  and the placement surface portion  113   a  is increased, and as a result, a fixing force of the energy storage device  210  to the placement surface portion  113   a  is enhanced. 
     In the present embodiment, the projecting portion  310  extends along the peripheral edge portion of the bottom surface  211   a  of the energy storage device  210 , and the accommodating portion  111  extends along the projecting portion  310  on the inner surface  113  of the outer case  100 . To be more specific, the projecting portion  310  is linearly provided along a part of the peripheral edge portion of the bottom surface  211   a  of the energy storage device  210  disposed adjacently to the spacer  301 . The accommodating portion  111  is formed linearly along the projecting portion  310  on the inner surface  113  of the outer case  100 . The same applies to the projecting portion  320 , and the projecting portion  320  is provided linearly along a part of the peripheral edge portion of the bottom surface  211   a  of the energy storage device  210  adjacent to the spacer  302 . The accommodating portion  112  is formed linearly along the projecting portion  320  on the inner surface  113  of the outer case  100 . 
     With such a configuration, the projecting portion  310  or  320  is provided in a range where the bottom surface  211   a  of the energy storage device  210  extends, and the entire region of the projecting portion  310  or  320  can be accommodated in the accommodating portion  111  or  112 . With such a configuration, it is possible to increase a creepage distance between the bottom surface  211   a  of the energy storage device  210  and another member (the energy storage device  210  or the end plate  400 ) disposed on an opposite side with the spacer  301  or  302  interposed therebetween in a wide range. This contributes to further improvement of safety. 
     4. Description of Modification Examples 
     Although the energy storage apparatus  10  according to the present embodiment has been described above, the present invention is not limited to the above-mentioned embodiment. That is, the embodiment disclosed herein is illustrative in all respects and is not restrictive, and the scope of the present invention is defined by the claims, and includes all modifications within the meaning and scope equivalent to the claims. 
     A member other than the end plate  400  may be disposed outward from the spacer  302  located at the end portion of the energy storage device array  201 . A case in which an electric device such as a control board or a relay is accommodated may be disposed outward from the spacer  302 . Even in this case, when the case is made of metal, or when a metal terminal or the like is exposed from the case, there is a case where electric insulation is ensured between the case and the energy storage device  210  which is close to the case in distance. In this case, by disposing the spacer  302  having the projecting portion  320  between the case and the energy storage device  210 , a creepage distance between the case and the energy storage device  210  at least on a lower end side of the spacer  302  increases. With such a configuration, the safety of the energy storage apparatus  10  can be enhanced. 
     It is not essential that the bottom surface  211   a  of the energy storage device  210  and the inner surface  113  of the outer case  100  are adhered to each other by the adhesive  90 . When the energy storage unit  200  can be fixed at a predetermined position in the inside of the outer case  100  by another member such as an inner lid or a bus bar frame disposed above the energy storage unit  200 , the bottom surface  211   a  of the energy storage device  210  and the inner surface  113  may not be adhered to each other. 
     In  FIGS.  7 A and  7 B , the adhesive  90  is disposed only between the bottom surface  211   a  of the energy storage device  210  and the placement surface portion  113   a , but the adhesive  90  may be disposed between the projecting portion  310  and the accommodating portion  111 . The same applies to the projecting portion  320 , and the adhesive  90  may be disposed between the projecting portion  320  and the accommodating portion  112 . With such a configuration, a fixing force of the entire energy storage unit  200  with respect to the inner surface  113  of the outer case  100  can be enhanced. 
     The placement surface portion  113   a  may directly support the bottom surface  211   a  of the energy storage device  210  by a surface when the placement surface rib  113   c  is not provided. The placement surface portion  113   a  may support the bottom surface  211   a  of the energy storage device  210  via the adhesive  90 , an insulating film, or the like regardless of the presence or absence of the placement surface rib  113   c . In either case, it can be said that the bottom surface  211   a  of the energy storage device  210  is substantially placed on the placement surface portion  113   a.    
     The spacer  301  may not have the projecting portion  310  in the entire region in the X-axis direction at the lower end portion of the spacer body  301   a . A plurality of projecting portions  310  may be provided at the lower end portion of the spacer body  301   a  so as to be separated from each other in the X-axis direction. Even in this case, the effect of increasing the creepage distance can be obtained in the existence range of each of the plurality of projecting portions  310 . The projecting portion  310  is preferably disposed at the lower end portion of the spacer body  301   a  in the entire region of the existence range of the energy storage device  210  in the X-axis direction. That is, the projecting portion  310  is disposed at the lower portion of the energy storage device  210  on the long side surface  211   b  side without fail and hence, reliability of electric insulation between the cases  211  of the energy storage devices  210  adjacent to each other can be enhanced. 
     It is not essential that the projecting portion  310  has the restricting portions  311 . That is, since the spacer  301  has the projecting portion  310  which projects downward from the bottom surfaces  211   a  of the two energy storage devices  210  adjacent to each other with the spacer  301  interposed therebetween, it is possible to obtain the effect of increasing the creepage distance between the two energy storage devices  210  by the projecting portion  310 . When the restricting portions  311  are provided on the projecting portion  310  without changing the projecting length of the projecting portion  310 , not only the projecting portion  310  can restrict the position of the energy storage device  210  but also an effect of further extending the creepage distance can be obtained. 
     As a material for forming the spacer  300 , a material having an electric insulation property other than resin may be adopted. The spacer  300  may be formed of an inorganic material such as mica or glass fiber, or may be formed of a material containing both resin and those materials other than the resin. The spacer  300  may be formed by coating a surface of a metal substrate with an insulating resin. That is, the spacer  300  only needs to have an insulation property that does not conduct between the plurality of members in contact with the spacer  300 , and the material thereof may be appropriately determined according to required rigidity, durability, heat resistance, flame retardancy, weight, or the like. 
     The energy storage unit  200  may not include the binding members (the end plates  400  and the side plates  500 ). When the energy storage device array  201  including the plurality of energy storage devices  210  can be bound from both sides in the arrangement direction by the outer case  100 , the energy storage unit  200  may not include the binding members. 
     A form constructed by freely combining the components included in the above-mentioned embodiment and the modification examples thereof is also included in the scope of the present invention. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be applied to an energy storage apparatus or the like including the energy storage device  210  such as a lithium ion secondary battery. 
     DESCRIPTION OF REFERENCE SIGNS 
       10 : energy storage apparatus 
       90 : adhesive 
       100 : outer case 
       110 : outer case body 
       111 : accommodating portion 
       111   a : first accommodating portion 
       111   b : second accommodating portion 
       112 : accommodating portion 
       113 : inner surface 
       113   a : placement surface portion 
       113   b : fixing surface portion 
       113   c : placement surface rib 
       115 : bottom wall 
       210 : energy storage device 
       211 : case 
       211   a : bottom surface 
       211   b : long side surface 
       211   c : short side surface 
       300 ,  301 ,  302 : spacer 
       301   a ,  302   a : spacer body 
       310 ,  320 : projecting portion 
       311 ,  322 : restricting portion