Patent Publication Number: US-2013244089-A1

Title: Secondary battery device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2012-057519, filed Mar. 14, 2012, the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to a secondary battery device comprising a plurality of secondary battery cells. 
     BACKGROUND 
     In recent years, attention has been paid to a secondary battery, for example, to a lithium ion secondary battery that is a nonaqueous secondary battery as a power supply of an electric vehicle, a hybrid electric vehicle, an electric moped or as a power supply of electrical equipment because the secondary battery has an high output and a high energy density. 
     In general, a secondary battery is configured as a battery cell including an exterior vessel, an electrode group accommodated in the exterior vessel together with an electrolyte, and an electrode terminal disposed to the exterior vessel. To obtain a large capacity and a high output, a battery module is configured by disposing a plurality of battery cells in an outer case side by side and connecting battery cells in series or in parallel and further a battery pack is configured by connecting a plurality of battery modules. 
     In the battery module, a resin is employed as a material of the outer case for the purpose of insulating the battery cell. The outer case is configured to cover the battery cells and the respective battery cells are mounted in a frame disposed to the outer case side. However, from a viewpoint of an assembly property when the battery cells are inserted, since a dimensional tolerance cannot help being increased, slight intervals exist between the battery cells and the outer case. When the intervals exist between the battery cells and the outer case, the battery cells are vibrated in the intervals between them and the outer case due to vibration in operation and thus a relative displacement is generated between the cells. In the case, since a load acts on a bus-bar attached to terminals of the battery cells and on junctions between the bus-bar and the terminals, there is a possibility that the bus-bar and the junctions are broken or damaged. Accordingly, a method of filling the intervals between the battery cells and the outer case with an adhesive and fixing the battery cells is employed. Otherwise, a method of pressing the battery cells in a stacked direction by bolt, presser member, and the like and fixing the battery cells is used. 
     However, since a process for filling the adhesive is additionally required, it is difficult to reduce an assembly time of the battery module. It is preferable to employ fixing that does not depend on an adhesive from a point of view of maintaining reliability of a secondary battery device over a long period. Likewise, it is also difficult to reduce an assembly time of the battery module also in a case that battery cells are fixed by bolt, presser member, and the like. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating a secondary battery device according to an embodiment; 
         FIG. 2  is an exploded perspective view illustrating a case main body, a battery cell group, and an upper case of the secondary battery device; 
         FIG. 3  is a perspective view illustrating an inner surface side of the upper case; 
         FIG. 4  is a perspective view illustrating a bottom wall side of the case main body in a broken fashion; 
         FIG. 5  is a sectional view of the secondary battery device along line V-V of  FIG. 1 ; 
         FIG. 6  is a sectional view illustrating an engaging state of a bottom wall of the case main body with a battery cell in enlargement; 
         FIG. 7  is a sectional view of the secondary battery device along line VII-VII of  FIG. 1 ; 
         FIG. 8  is a sectional view illustrating an engaging state of the case main body and an upper case with a battery cell in enlargement; 
         FIG. 9  is an exploded sectional view illustrating the case main body, battery cell, and upper case; 
         FIG. 10  is a table showing a plurality of examples of a foaming paint for forming a foam coating layer in the secondary battery device and an evaluation thereof; and 
         FIG. 11  is a perspective view illustrating a battery cell of a secondary battery device according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments will be described hereinafter with reference to the accompanying drawings. In general, according to one embodiment, a secondary battery device comprises a secondary battery cell; a case configured to accommodate the secondary battery cell; and foam coating layers sandwiched between an outer surface of the secondary battery cell and an inner surface of the case and configured to hold the secondary battery cell. 
       FIG. 1  is a perspective view illustrating an outside appearance of a secondary battery device according to a first embodiment, and  FIG. 2  is an exploded perspective view illustrating a case main body, a battery cell group inside of the secondary battery device, and a top cover. 
     As shown in  FIGS. 1 and 2 , the secondary battery device  10  comprises, for example, a rectangular box-shaped case  12 , a plurality of battery cells (secondary battery cells)  14 , for example, 12 battery cells  14  accommodated in the case side by side, and a battery monitor substrate  66  for detecting the voltage and the temperature of the respective battery cells and is configured as a battery module (assembled battery). Electrode terminals of adjacent battery cells  14  are electrically connected to each other by a bus-bar as a conductive member. 
     The case  12  comprises a rectangular box-shaped case main body  16  having an upper surface opened as well as a bottom wall, an upper case  18  for covering the open upper surface of the case main body, and further a not illustrated top cover which are formed of a synthetic resin having an insulation property, for example, polycarbonate (PC) polyphenylene ether (PPE), and the like, respectively. 
       FIG. 8  illustrates a cross section of the secondary battery device including the battery cells  14 . As shown in  FIGS. 2 and 8 , each battery cell  14  is a nonaqueous electrolyte secondary battery, for example, a lithium ion battery and the like and includes a flat and approximately rectangular parallelepiped-shaped exterior vessel  30  formed of aluminum or aluminum alloy and an electrode body  31  accommodated in the exterior vessel  30  together with an nonaqueous electrolyte. The exterior vessel  30  has a vessel main body  32  having an upper end opened and a rectangular sheet-shaped lid member  33  welded to the vessel main body and closing the opening of the vessel main body, and an inside of the exterior vessel  30  is formed to be liquid-tight. The electrode body  31  is wound with, for example, a positive electrode plate and negative electrode plate in a swirl state with a separator interposed therebetween and further is formed in a flat rectangular shape by being compressed in a radial direction. 
     A positive electrode terminal  34   a  and a negative electrode terminal  34   b  are disposed to both ends of the lid member  33  in a longitudinal direction, respectively and projects from the lid member. The positive electrode terminal  34   a  and the negative electrode terminal  34   b  are connected to a positive electrode and a negative electrode of the electrode body  31 , respectively. One of the terminals, for example, the positive electrode terminal  34   a  is electrically connected to the lid member  33  and becomes the same potential as that of the exterior vessel  30 . The negative electrode terminal  34   b  extends passing through the lid member  33 . A seal member composed of an insulator such as a synthetic resin, glass, and the like, for example, a gasket is interposed between the negative electrode terminal  34   b  and the lid member  33   b.    
     A safety valve  36  having, for example, a rectangular shape is formed in a central portion of the lid member  33 . The safety valve  36  is formed of a thin-wall portion created by forming a part of the lid member  33   b  to a thickness about half that of the original thickness and a plurality of carved seals are formed in a central portion of an upper surface of the thin-wall portion. When a gas is generated in the exterior vessel  30  by an abnormal mode of the battery cells  14  and the like and the internal pressure in the exterior vessel is increased to a predetermined value or higher, the safety valve  36  is opened and a failure such as an explosion and the like of the exterior vessel  30  is prevented by reducing the internal pressure. 
     As shown in  FIGS. 2 and 5 , the plurality of battery cells  14  are disposed side by side in a row in a state in which the main surfaces of the exterior vessels  30  confront each other at predetermined intervals, as well as upper ends of the exterior vessels  30 , to which the electrode terminals  34   a ,  34   b  are disposed, face in the same direction. 
     Next, a configuration of the case  12  will be described in detail. As shown in  FIGS. 1 ,  2 ,  5 , and  7 , the case main body  16  has a rectangular bottom wall  22  formed in a size corresponding to the 12 battery cells  14  and confronting bottoms of the 12 battery cells  14 , a pair of first sidewalls  24   a ,  24   b  standingly disposed along two confronting side edges of the bottom wall  22 , here, along a long side and confronting side surfaces of the battery cells  14 , and a pair of second sidewalls  26   a ,  26   b  standingly disposed along the other two side edges of the bottom wall  22 , here, along a short side and confronting the main surfaces of the battery cells  14 . 
     A plurality of partition plates  23 , for example, 11 partition plates  23  stand on the bottom wall  22 . The partition plates  23  are formed in an elongated rectangular shape and confront the second sidewalls  26   a ,  26   b  approximately in parallel therewith as well as disposed side by side at predetermined intervals in a longitudinal direction of the bottom wall  22 . Both end edges and lower edges of the respective the partition plates  23  are coupled with inner surfaces of the pair of the first sidewalls  24   a ,  24   b  and an inner surface of the bottom wall  22 , respectively. The partition plates  23  may be molded integrally with the case main body  16  or the partition plates formed separately may be fixed to the case main body. 
     A plurality of accommodation portions, here, 12 accommodation portions for accommodating lower end portions of the battery cells  14  are prescribed by the bottom wall  22 , the first sidewalls  24   a ,  24   b , and the second sidewalls  26   a ,  26   b  or by the partition plates  23 . Each accommodation portion is formed in a slender rectangular shape corresponding to a cross-sectional shape of the exterior vessel  30  of the battery cell  14  and extends along a width direction of the case main body  16 . The plurality of accommodation portions are disposed side by side at predetermined intervals in a longitudinal direction of the case main body  16 . 
     As shown in  FIGS. 1 and 2 , the pair of the first sidewalls  24   a ,  24   b  extending in the longitudinal direction of the case main body  16  is formed with a plurality of ventilation holes  28 , respectively. Each ventilation hole  28  is formed in, for example, a slender rectangular shape at a position where it stands in a row with each partition plate  23  and extends along a height direction of the case main body  16 . That is, the respective ventilation holes  28  are disposed at positions where they confront the intervals between the plurality of battery cells  14  accommodated in the case  12 . Cooling air can be supplied into the case  12  as well as to a periphery of the battery cells  14  via the ventilation holes  28 . 
     As shown in  FIGS. 2 ,  4 , and  5  to  8 , a foaming paint is coated on an inner surface of the case main body  16  and a foam coating layer is formed. In the embodiment, the foaming paint is coated on an inner surface of the bottom wall  22 , the partition plates  23 , lower inner surfaces of the first sidewalls  24   a ,  24   b , and lower inner surfaces of the second sidewalls  26   a ,  26   b  and forms the foam coating layer  40  having a predetermined thickness, for example, a thickness of about 300 μm to 1 mm. After a temperature foaming paint or humidity foaming paint has been previously coated on the inner surface of the case main body  16 , foaming agents in the foaming paint are foamed by being applied with a predetermined temperature or humidity, and the foam coating layer  40  including a number of independent bubbles is formed. The foaming magnification of the foaming paint can be adjusted by adjusting the temperature or humidity applied to the foaming paint. 
     The foam coating layer  40  can adjust the reactive force by the number of independent bubbles and the foaming magnification can be changed by the mixing ratio of a main agent (binder) and the foaming agent (foaming beads). The foam coating layer  40  can elastically press and positionally fix the battery cells  14  by its frictional force and compression reactive force of the bubbles. The foaming paint and the foaming agent will be explained later in detail. 
     As shown in  FIGS. 3 ,  5 , and  7 , the upper case  18  has a rectangular frame member  18   a  and a rectangular ceiling wall  18   b  that positions in an intermediate portion in a height direction of the frame member integrally therewith. A plurality of partition plates  42 , for example, 11 partition plates  42  are standingly disposed on an inner surface of the ceiling wall  18   b . The partition plates  42  are formed in a slender rectangular shape, respectively, extend in parallel in a width direction of the ceiling wall  18   b  as well as are disposed side by side at predetermined intervals in a longitudinal direction of the ceiling wall  18   b . Both the end edges of each partition plate  42  in its axis direction and an upper edge of the each partition plate  42  are coupled with an inner surface of the frame member  18   a  and the inner surface of the ceiling wall  18   b , respectively. The partition plates  42  may be molded integrally with the upper case  18  or the partition plates  42  molded separately may be fixed to the upper case. 
     A plurality of accommodation portions, here, 12 accommodation portions for accommodating upper end portions of the battery cells  14  are defined by the ceiling wall  18   b , the frame member  18   a , and the partition plates  42 . Each accommodation portion is formed in a slender rectangular shape corresponding to a cross-sectional shape of the exterior vessel  30  of the battery cell  14  and extends along a width direction of the case  12 . The plurality of accommodation portions are disposed side by side in a longitudinal direction of the case  12  at predetermined intervals. 
     In the upper case  18 , bottoms of the respective accommodation portions, that is, the ceiling wall  18   b  is formed with rectangular transparent holes  44   a ,  44   b  corresponding to the positive electrode terminals  34   a  and the negative electrode terminals  34   b  of the battery cells  14  and further formed with exhaust holes  46  confronting the safety valves  36  of the battery cells  14 , The transparent holes  44   a ,  44   b  are positioned on both end portions of the accommodation portions, and the exhaust holes  46  position at the centers between the transparent holes  44   a ,  44   b.    
     As shown in  FIGS. 3 ,  5 ,  7 , and  8 , in the embodiment, the foaming paint is coated on an inner surface of the upper case  18  and a foam coating layer  50  is formed. The foaming paint is coated on the inner surface of the frame member  18   a , the inner surface of the ceiling wall  18   b , and the partition plates  42  and forms the foam coating layer  50  having a predetermined thickness, for example, a thickness of about 300 μm to 1 mm. After a temperature foaming paint or humidity foaming paint has been previously coated on the inner surface of the upper case  18 , a foaming agent in the foaming paint is foamed by being applied with a predetermined temperature or humidity, and the foam coating layer  50  including a number of independent bubbles is formed. The foaming magnification of the foaming paint can be adjusted by adjusting the temperature or humidity applied to the foaming paint. The foam coating layer  50  is the same as the foam coating layer  40  on the case main body  16  side described above and can elastically press and positionally fix the battery cells  14  by the compression reactive force and frictional force of the bubbles. Note that a plurality of recesses may be formed in a coating region of a case inner surface so that the foaming paint is easily adhered to the coating region. 
     The upper case  18  configured as described above is caused to cover the upper surface opening of the case main body  16  and fixed to upper ends of sidewalls of the case main body  16  by screw. With configuration, the upper case  18  constitutes the ceiling wall and upper portions of respective sidewalls of the case  12 . 
     As shown in  FIG. 9 , at the time of assembly, the battery cells  14  are inserted into the case main body  16  from the upper opening of the case main body and the lower end portions of the battery cells  14  are pushed into corresponding accommodation portions on the bottom wall  22  side. An outer surface of the lower end portion of the battery cell  14  comes into intimate contact with the foam coating layer  40  and is pushed to a predetermined position while compressing the foam coating layer  40 . With the operation, the foam coating layer  40  is sandwiched between the outer surface of the battery cell  14  and the inner surface of the case  12  in a compressed state. 
     After the 12 battery cells  14  have been mounted in the case main body  16 , the upper case  18  is caused to cover the case main body  16  and fixed to the case main body by screw. At the time, the upper end portion of each battery cell  14  is pushed into a corresponding accommodation portion of the upper case  18 , and the outer surface of the upper end portion of the battery cell  14  comes into intimate contact with the foam coating layer  50  and is pushed to a predetermined position while compressing the foam coating layer  50 . With the operation, the foam coating layer  50  is sandwiched between the outer surface of the battery cell  14  and the inner surface of the case  12  in a compressed state. 
     As shown in  FIGS. 5 to 8 , the 12 battery cells  14  are accommodated in the case  12 , respectively and disposed side by side in a row each other at the intervals. The foam coating layer  40  is sandwiched between the outer surface of the lower end portion of each battery cell  14  and the inner surface of the case. Further, the foam coating layer  50  is sandwiched between the outer surface of the upper end portion of each battery cell  14  and the inner surface of the case. Each battery cell  14  receives a reactive force from the foam coating layers  40 ,  50  from six directions, i.e., from both up-and-down sides, both right-and-left sides, and both front-and-back sides and further is positioned and kept at the predetermined position by the frictional force between the battery cell  14  and the foam coating layers without backlash. At the same time, vibration acting on the battery cell  14  is absorbed by the foam coating layers  40 ,  50 . 
     As shown in  FIGS. 1 ,  2 ,  5 , and  7 , upper end positions of the plurality of battery cells  14 , in particular, height positions of the electrode terminals  34   a ,  34   b  are determined by abutting the plurality of battery cells  14  on the inner surface of the upper case  18 . With the configuration, the plurality of battery cells  14  are disposed in a uniform state without dispersion of height positions of the electrode terminals. The positive electrode terminal  34   a  and the negative electrode terminal  34   b  of each battery cell  14  are inserted into the corresponding transparent holes  44   a ,  44   b  of the ceiling wall  18   b , respectively and are exposed upward. The safety valve  36  of each battery cell  14  confronts the exhaust hole  46  of the ceiling wall  18   b.    
     The plurality of battery cells  14  are electrically connected in, for example, series by a plurality of bus-bars  62  as conductive members. The plurality of battery cells  14  are disposed in a direction where the positive electrode terminals and the negative electrode terminals of adjacent battery cells  14  are alternately disposed. Each bus-bar  62  is formed of a metal plate composed of a conductive material, for example, aluminum and the like. Each bus-bar  62  has one end portion joined to the positive electrode terminal  34   a  of a battery cell  14  and the other end portion jointed to the negative electrode terminal  34   b  of an adjacent battery cell  14  to thereby electrically connect the electrode terminals. As described above, the 12 battery cells  14  are connected in series by the plurality of bus-bars  62 . Note that the plurality of battery cells  14  are not limited to being connected in series and may be connected in parallel. 
     In the plurality of battery cells  14 , the positive electrode terminal  34   a  of the battery cell  14  positioned at one end of an arrangement and the negative electrode terminal  34   b  of the battery cell  14  positioned at the other end of the arrangement are connected with output terminals  64   a ,  64   b , respectively. As shown in  FIGS. 1 and 2 , the upper case  18  is installed with the battery monitor substrate  66  for detecting the voltage and temperature of the battery cells  14  and electrically connected to the respective bus-bars  62  and output terminals  64 . Further, the upper case  18  is installed with an exhaust pipe  60  that communicates with the exhaust holes  46  formed on the upper case. 
     Next, examples of the foaming paint and foaming agent that form the foam coating layer will be explained in detail. 
     The foaming paint contains foaming particles and a binder component. The foaming particles are foamed by being heated and form foamed beads. The foamed beads and the binder component are contained in the foam coating layer molded by heat-foaming. 
     A binder resin used as the binder component in the examples contains polyol containing a hydroxyl group and a curing agent containing an isocyanate group (an isocyanate crosslinking agent). As the polyol, for example, polycarbonate polyol, polyester polyol, and the like can be used. As the isocyanate crosslinking agent, hexamethylene diisocyanurate (HMDI nurate) can be used. 
     The foaming paint used in the examples contains 3-20% foaming resin particles to a resin solid content of the binder component. The temperature of a foaming temperature region of the foaming resin particles at which they can be used is 70 to 160° C. The foaming paint can further contain a tin catalyst, for example, dibutyltin dilaurate (DBTDL) and the like. 
     The universal hardness of a coating film obtained by coating a paint in which the foaming particles are excluded from the foaming paint is preferably 10.0 N/mm 2  or less. Further, the elastic deformation ratio (We/Wtot) of the coating film is preferably 80% or more. 
     The plurality of examples are shown below and a foam coating layer used in the examples will be specifically explained. A result obtained in the respective examples is shown in Table 1 of  FIG. 10 . 
     Example 1 
     Composition of Foaming Paint J-1 
       
     
       
         
           
               
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Polycarbonate polyol 
                 100 
                 parts by weight 
               
               
                   
                 (solid content amount 100%) 
               
               
                   
                 Hexamethylene diisocyanurate 
                 100 
                 parts by weight 
               
               
                   
                 (solid content amount 54%) 
               
               
                   
                 Foaming particles having a foaming 
                 15 
                 parts by weight 
               
               
                   
                 temperature region of 90 to 160° C. 
               
               
                   
                 a 1% solution of dibutyltin dilaurate 
                 2.0 
                 parts by weight 
               
               
                   
                   
               
            
           
         
       
     
     Foaming paint J-1 having the composition described above was prepared, and a foam coating layer having a thickness of 300 μm was formed by spraying the foaming paint on a test piece composed of a polycarbonate (PC) material that can be used to a case main body using a high-pressure spray gun and subsequently foaming a coating film by heating the coating film in an atmosphere of 120° C. for 7 minutes. The thickness of the coating film was measured by a soft-touch microgauge. The tolerance was ±100 μm. 
     The degree and uniformity of foaming were observed as the state of the obtained foam coating layer, and the foam coating layer was indicated by ∘ when foaming was sufficiently performed and uniform, whereas the foam coating layer was indicated by Δ when foaming was executed insufficiently or nonuniformly or was not yet executed. It was found that uniform foaming was executed sufficiently on the obtained foam coating layer. 
     Further, when the foam coating layer was confirmed, the feel of the foam coating layer was evaluated. A case that a foaming state was uniform and a sufficient reactive force could be obtained from the foam coating layer at the time it was pressed by a finger was indicated by ∘, whereas a case that although uniform foaming was obtained, a sufficient reactive force could not be obtained because the coating film was hard, a case that foaming was insufficient and a reactive force could not be obtained, or a case that foaming lacks uniformity and a stable reactive force could not be obtained was indicated by Δ. 
     When a coating film was formed by coating a paint having a composition in which the foaming particles were excluded from foaming paint J-1 and the universal hardness HuK of the coating film was measured, the hardness was 1.7 N/mm 2 . Further, when the elastic deformation ratio (We/Wtot) of a similar coating film was measured, the ratio was 95%. 
     Example 2 
     Composition of foaming paint J-2 
       
     
       
         
           
               
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Polyester polyol 
                 100 
                 parts by weight 
               
               
                   
                 (solid content amount 100%) 
               
               
                   
                 Hexamethylene diisocyanurate 
                 50 
                 parts by weight 
               
               
                   
                 (solid content amount 54%) 
               
               
                   
                 Foaming particles having a foaming 
                 13 
                 parts by weight 
               
               
                   
                 temperature region of 90 to 160° C. 
               
               
                   
                 A 1% solution of dibutyltin dilaurate 
                 1.5 
                 parts by weight 
               
               
                   
                   
               
            
           
         
       
     
     When a foam coating layer was formed as in example 1 except that foaming paint J-2 having the above composition was used and the state of the foam coating layer was evaluated in the same way, it was found that uniform foaming was executed sufficiently. Further, when the feel of the foam coating layer was evaluated, it was found that a sufficient reactive force could be obtained at the time the foam coating layer was pressed by a finger. 
     Further, when the universal hardness HuK and elastic deformation ratio (We/Wtot) of a coating film coated with a paint having a composition in which the foaming particles were excluded from foaming paint J-2, the universal hardness and the elastic deformation ratio were 0.6 N/mm 2  and 85%, respectively. 
     Example 3 
     Paint H-1 
       
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 Polycarbonate polyol 
                 100 
                 parts by weight 
               
               
                 (solid content amount 100%) 
               
               
                 Melamine resin (solid content amount 90%) 
                 30 
                 parts by weight 
               
               
                 Foaming particles having a foaming 
                 13 
                 parts by weight 
               
               
                 temperature region of 90 to 160° C. 
               
               
                   
               
            
           
         
       
     
     When a foam coating layer was formed as in example 1 except that foaming paint H-1 having the above composition was used and the state of the foam coating layer was evaluated in the same way, it was found that uniform foaming was executed sufficiently. Further, when the feel of the foam coating layer was evaluated, it was found that a sufficient reactive force could be obtained even if the foam coating layer was pressed by a finger because the coating film was hard. 
     Further, when the universal hardness HuK and elastic deformation ratio (We/Wtot) of a coating film coated with a paint having a composition in which the foaming particles were excluded from foaming paint H-1, the universal hardness and the elastic deformation ratio were 7.7 N/mm 2  and 50%, respectively. It was found from example 3 that there was a tendency for the elastic deformation ratio to be reduced by changing the crosslinking agent from the isocyanate crosslinking agent to the melamine resin. 
     Example 4 
     Paint H-2 
       
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 Acrylic polyol (solid content amount 100%) 
                 100 
                 parts by weight 
               
               
                 Hexamethylene diisocyanurate 
                 25 
                 parts by weight 
               
               
                 (solid content amount 54%) 
               
               
                 A 1% solution of dibutyltin dilaurate 
                 0.6 
                 parts by weight 
               
               
                 Foaming particles having a foaming 
                 6 
                 parts by weight 
               
               
                 temperature region of 90 to 160° C. 
               
               
                   
               
            
           
         
       
     
     When a foam coating layer was formed as in example 1 except that foaming paint H-2 having the above composition was used and the state of the foam coating layer was evaluated in the same way, it was found that uniform foaming was executed sufficiently. Further, when the feel of the foam coating layer was evaluated, it was found that a sufficient reactive force could be obtained even if the foam coating layer was pressed by a finger because the coating film was hard. 
     Further, when the universal hardness HuK and elastic deformation ratio (We/Wtot) of a coating film coated with a paint having a composition in which the foaming particles were excluded from foaming paint H-2, the universal hardness and the elastic deformation ratio were 120 N/mm 2  and 35%, respectively. 
     It was found from example 4 that the universal hardness was increased and the elastic deformation ratio was reduced by changing polyol to acrylic polyol. 
     Example 5 
     Paint H-3 
       
     
       
         
           
               
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Polycarbonate polyol 
                 100 
                 parts by weight 
               
               
                   
                 (solid content amount 100%) 
               
               
                   
                 Hexamethylene diisocyanurate 
                 100 
                 parts by weight 
               
               
                   
                 (solid content amount 54%) 
               
               
                   
                 a 1% solution of dibutyltin dilaurate 
                 2.0 
                 parts by weight 
               
               
                   
                 Foaming particles having a foaming 
                 2.5 
                 parts by weight 
               
               
                   
                 temperature region of 90 to 160° C. 
               
               
                   
                   
               
            
           
         
       
     
     When a foam coating layer was formed as in example 1 except that foaming paint H-3 having the above composition was used and the state of the foam coating layer was evaluated in the same way, it was found that foaming was executed insufficiently. Further, when the feel of the foam coating layer was evaluated, it was found that a sufficient reactive force could not be obtained even if the foam coating layer was pressed by a finger because foaming was executed insufficiently. 
     Further, when the universal hardness HuK and elastic deformation ratio (We/Wtot) of a coating film coated with a paint having a composition in which the foaming particles were excluded from foaming paint H-3, the universal hardness HuK and the elastic deformation ratio were 1.7 N/mm 2  and 95%, respectively. 
     It was found from example 5 that when an amount of the foaming particles in the foaming paint was excessively small, there was a tendency for the foaming property to be reduced and it was difficult to obtain a sufficient foaming state. 
     Example 6 
     Paint H-4 
       
     
       
         
           
               
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Polycarbonate polyol 
                 100 
                 parts by weight 
               
               
                   
                 (solid content amount 100%) 
               
               
                   
                 Hexamethylene diisocyanurate 
                 100 
                 parts by weight 
               
               
                   
                 (solid content amount 54%) 
               
               
                   
                 A 1% solution of dibutyltin dilaurate 
                 2.0 
                 parts by weight 
               
               
                   
                 Foaming particles having a foaming 
                 35 
                 parts by weight 
               
               
                   
                 temperature region of 90 to 160° C. 
               
               
                   
                   
               
            
           
         
       
     
     When a foam coating layer was formed as in example 1 except that foaming paint H-4 having the above composition was used and the state of the foam coating layer was evaluated in the same way, it was found that foaming was nonuniform. Further, when the feel of the foam coating layer was evaluated, it was found that irregularity was caused to foaming and the film thickness of the foam coating layer and uniformity of reactive force of the foam coating layer at the time it was pressed by a finger were reduced. 
     Further, when the universal hardness HuK and elastic deformation ratio (We/Wtot) of a coating film coated with a paint having a composition in which the foaming particles were excluded from foaming paint H-4, the universal hardness and the elastic deformation ratio were the same as those of example 5. 
     It was found that an amount of the foaming particles in the foaming paint was excessively large, there was a tendency for the foaming property to become excessively high and foaming to become nonuniform. 
     Example 7 
     Paint H-5 
       
     
       
         
           
               
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Polycarbonate polyol 
                 100 
                 parts by weight 
               
               
                   
                 (solid content amount 100%) 
               
               
                   
                 Hexamethylene diisocyanurate 
                 100 
                 parts by weight 
               
               
                   
                 (solid content amount 54%) 
               
               
                   
                 a 1% solution of dibutyltin dilaurate 
                 2.0 
                 parts by weight 
               
               
                   
                 Foaming particles having a foaming 
                 15 
                 parts by weight 
               
               
                   
                 temperature region of 160 to 280° C. 
               
               
                   
                   
               
            
           
         
       
     
     Although a coating film was heated in an atmosphere of 120° C. for 7 minutes using foaming paint H-5 having the above composition as in example 1, no foaming was caused. 
     Further, the universal hardness HuK and elastic deformation ratio (We/Wtot) of a coating film coated with a paint in which the foaming particles were excluded from foaming paint H-5 were the same as those of example 5. 
     It was found that when the temperature of a foaming temperature region of foaming particles in the foaming paint was excessively high the foaming particles were not foamed under a dry condition in the atmosphere of 120° C. 
     According to the secondary battery device configured as described above, the battery module having the case  12  in which the battery cells  14  are accommodated can be assembled only by mounting the battery cells  14  in the respective accommodation portions of the case main body  16  and attaching the upper case  18  from thereabove. At the time, the foam coating layers  40 ,  50  formed on the inner surface of the case  12  come into intimate contact with the outer surfaces of the battery cells  14  and press the battery cells from the 6 directions to thereby support and keep the battery cells in the accommodation portions without backlash as previously determined. With the configuration, the plurality of battery cells can be held without backlash without using adhesive or a fixing bolt. Accordingly, when the secondary battery device is assembled, the assembly time can be reduced by omitting the adhesive coating process, adhesive curing process, or bolting process. At the same time, since the battery cells can be supported without backlash for a long period without depending on adhesive, reliability can be improved. Further, since vibration acting on the battery cells  14  is absorbed by the foam coating layers  40 ,  50 , the battery cells can be suppressed from being positionally offset. 
     Further, since battery cells are not fixed by adhesive, the battery cells can be easily removed from the case, with a result that the secondary battery device can be disassembled and the battery cells can be replaced as maintenance of the secondary battery device. 
     From what has been described above, the secondary battery device that is compact and has an improved assembly property and reliability can be obtained. 
     Note that, in the embodiments described above, although the foam coating layer formed on the inner surface of the case is configured to confront the six surfaces of the battery cell, the present invention is not limited thereto and the foam coating layer may be formed so as to be sandwiched between at least one surface of the outer surface of the battery cell and the inner surface of the case. For example, the foam coating layer may be coated on the inner surface of the bottom wall of the case or the inner surface of the ceiling wall. Even in the case, the battery cells can be positioned and held in the accommodation portions of the case without backlash and the assembly property and the reliability can be improved. 
     It is sufficient for the foam coating layer to be disposed so as to be sandwiched between the outer surfaces of the battery cells and the inner surface of the case, and the foam coating layers  40 ,  50  may be coated and formed on the outer surfaces of the battery cells  14  as illustrated in  FIG. 11  in addition to that they are coated and formed on the inner surface of the case. Also in the case, the foam coating layer comes into intimate contact with the inner surface of the case, sandwiched between the outer surface of the battery cell and the inner surface of the case so that the battery cells can be positioned and held without backlash by mounting the battery cells  14  in the case  12 . Further, the foam coating layer formed on at least a surface of the battery cell can exhibit effect. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions. 
     For example, the plurality of battery cells are configured to be disposed in a row, they are not limited thereto and may be disposed in a plurality of rows. The number of battery cells can be increased and decreased according to a design output of the secondary battery device. Further, in the examples described above, although the case main body is configured to be integrally molded by the resin, the case main body may be formed by welding a bottom wall, sidewalls, and partition plates having been separately molded to each other.