Abstract:
A method for manufacturing a case for a secondary battery includes preparing a case material in a plate state; setting a plurality of sections on the case material, each section including parts for forming a pan for a battery main body, a gas receiving portion disposed at a side of the pan, a path connecting the pan and the gas receiving portion, and a cover portion covering the pan and the gas receiving portion together; forming the pan of the battery main body, the gas receiving portion, and the path by molding the case material; and severing each section from the case material.

Description:
This is a division of copending application Ser. No. 09,328,295, filed on Jun. 9, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a case for a secondary battery and a manufacturing method thereof, and more particularly, to a case for a secondary battery which seals a main body of a current-generating battery, and to a manufacturing method thereof. 
     2. Description of the Related Art 
     Secondary batteries usually include a battery main body for generating current formed by stacking an anode plate, a cathode plate and a separator. An electrode terminal is connected to the battery main body which functions as an electrical passage to the outside. The battery main body and a portion of the electrode terminal are coupled, forming a seal. 
     According to the conventional technology, the lithium secondary battery is manufactured after the battery main body is inserted in a case in a form of a pouch. However, due to the structure as above, mass production of the battery is not easy and furthermore a bonding surface which closes a receiving portion of the case where the battery is received is not stable. 
     SUMMARY OF THE INVENTION 
     To solve the above problems, it is an objective of the present invention to provide a case for a secondary battery which can be manufactured through mass production and has an improved bonding surface. 
     It is another objective of the present invention to provide a method for manufacturing the case for a secondary battery 
     Accordingly, to achieve the first objective, there is provided a case for a secondary battery which comprises: a pan having a space for accommodating a battery main body and an opening at the upper side thereof; a first bonding portion extended along the edge of the pan; a cover portion extended from the upper portion of one side of the pan for closing the opening of the pan by being folded onto the pan; and a second bonding portion extended along the edge of the cover portion and correspondingly attached to the first bonding portion when folded onto the pan. 
     It is preferable in the present invention that the pan, the first bonding portion, the cover portion, and the second bonding portion are integrally formed. 
     It is also preferable in the present invention that the first bonding portion and the second bonding portion are attached to each other without deformation. 
     It is yet preferable in the present invention that an emboss is formed at corresponding portions of the first bonding portion and the second bonding portion and the embossed portions of the first bonding portion and the second bonding portion are attached to each other. 
     It is further preferable in the present invention that concave and convex portions are formed at corresponding portions of the first bonding portion and the second bonding portion along the edge thereof and the concave and convex portions of the first bonding portion and the second bonding portion are attached to each other. 
     According to another aspect of the present invention, there is provided a case for a secondary battery which comprises: a pan having a space for accommodating a battery main body and an opening at the upper side thereof; a first bonding portion extended along the edge of the pan; a cover portion formed separately from the pan for closing the opening of the pan; and a second bonding portion extended along the edge of the cover portion and correspondingly attached to the first bonding portion. 
     To achieve the second objective, there is provided a method for manufacturing a case for a secondary battery which comprises the steps of: sectioning a plate material for the case to form a pan and a cover portion on the plate material; molding the material to form the pan; and severing the material according to each section of the plate material preparing a case material in a plate state: setting a plurality of sections on the case material for forming a pan of a battery main body, a gas receiving portion disposed at a side surface of the pan of the battery main body, a path connecting between the pan of the battery main body and the gas receiving portion, and a cover portion covering the pan of the battery main body and the gas receiving portion together; forming the pan of the battery main body, the gas receiving portion, and the path by molding the case material; and severing the case material according to each section. 
     It is preferable in the present invention that the molding of the material is performed by a pressing process. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objectives and advantages of the present invention will become more apparent by describing in detail a preferred embodiment thereof with reference to the attached drawings in which: 
     FIG. 1 is an exploded perspective view illustrating a secondary battery having a case according to a preferred embodiment of the present invention; 
     FIG. 2 is a plan view of the secondary battery of FIG. 1 in an assembled is state; 
     FIG. 3 is an exploded perspective view illustrating a secondary battery having a case according to another preferred embodiment of the present invention; 
     FIG,  4  is a plan view of the secondary battery of FIG. 3 in an assembled state; 
     FIG. 5 is a perspective view for explaining a method for manufacturing the case of the secondary battery shown in FIG. 1; and 
     FIGS. 6,  7 , and  8  are sectional views taken along the lines VI—VI and VII—VII of FIG.  2  and the line VIII—VIII of FIG. 4, respectively. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a case of a secondary battery according to a preferred embodiment of the present invention. Referring to the drawing, the secondary battery includes a battery main body  4  for generating current, in which an anode plate  1 , a cathode plate  2  and a separator  3  are stacked, and a case  10  for housing the battery main body  4 . The battery main body  4  can have a different structure according to the type of lithium secondary battery, for example, a lithium ion battery, a lithium polymer battery, and a plastic lithium ion battery. One end of an electrode terminal  5  functioning as an electrical passage to the outside is connected to each electrode plate of the battery main body  4  when the battery main body  4  is coupled to the case  10  forming a seal. The other end of the electrode terminal  5  is exposed to the outside. 
     According to the present invention, the case  10  includes a pan  11  where the battery main body  4  is received, a first bonding portion  12  which is a flange along the edge of the pan  11 , a cover portion  15  which is to be folded onto the pan  11  to close the opening of the pan  11 , and a second bonding portion  14  which is extends along the edge of the cover portion  15  and attached to the first bonding portion  12  when the cover portion is folded onto the pan  11 . The pan  11  is a cubic space for accommodating the battery main body  4  and has an opening only at the upper surface thereof. The cover portion  15  is an extended flange on one side of the pan  11  and can close the pan  11  when folded. 
     The pan  11 , the first bonding portion  12 , the cover portion  15 , and the second bonding portion  14  are integrally formed. The battery main body  4  is inserted in the pan  11  through the opening. As shown in the drawing, the first bonding portion  12  and the second bonding portion  14  form one rectangular flange when the cover portion  15  is not folded onto and does not close the pan  11 . The cover portion  15  closes the upper opening of the pan  11  after the battery main body  5  is inserted in the pan  11 . The first bonding portion  12  and the second bonding portion  14  can be bent to 90° after being bonded together. 
     FIG. 2 is a plan view showing the secondary battery of FIG. 1 in an assembled state. Referring to the drawing, after the battery main body  4  is inserted into the pan  11 , the electrode terminals  5  connected to each electrode plate (not shown) of the battery main body  4  are exposed outside the case  10  to a predetermined length and the cover portion  15  closes the pan  11 . The hatched area  21  in the drawing shows the area where the first and second bonding portions  12  and  14  are coupled to each other. Here, since no additional bonding portion is needed for the portion where the cover portion  15  extends from the pan  11 , the ratio of occupancy of the battery main body  4  to the total volume of the case  10  increases. Thus, battery efficiency per unit volume is improved in the secondary battery. 
     FIG. 3 shows a case for a secondary battery according to another preferred embodiment of the present invention. Referring to the drawing, the secondary battery, as in the secondary battery shown in FIG. 1, includes a battery main body  4  for generating current, in which an anode plate  1 , a cathode plate  2  and a separator  3  are stacked, and a case  30  for sealing the battery main body  4 . Here, the case  30  includes a pan  31  and a cover portion  35  separately manufactured to cover the opening of the pan  31 . The pan  31  is rectangular. The pan  31  has a flange as a first bonding portion  32 . The cover portion  35  is a plate capable of closing the opening of the pan  31  after the battery main body  4  is inserted into the pan  31 . A second bonding portion  34  is a marginal area of the cover portion  35  and the second bonding portion  34  is attached to the first bonding portion  32 . The pan  31  and the cover portion  35  can be manufactured by a molding process such as metal molding of plate material for the case. 
     FIG. 4 is a plan view showing the secondary battery of FIG. 3 in an assembled state. Referring to the drawing, the battery main body  4  is inserted into the pan  31  and the cover portion  35  covers the pan  31  in a state in which the electrode terminals  5  connected to the respective electrode plates (not shown) of the battery main body  4  are exposed outside the case  30  to a predetermined length. The hatched area  41  of the drawing indicates a portion where the first bonding portion  32  and the second bonding portion  34  are attached to each other. Here, to increase the bonding strength between the first bonding portion  32  and the second bonding portion  34 , the pan  31  and the cover portion  35  can be manufactured using different materials and in different thicknesses. 
     The case for the secondary battery having the above structure may be manufactured as follows. 
     A metal plate is molded to form the pan  11  ( 31 ) and the first bonding portion  12  ( 32 ), and the second bonding portion  14  ( 34 ) at the cover portion  15  ( 35 ). Here, the cover portion  15  ( 35 ) and the second bonding portion  14  ( 34 ) are formed integrally with the pan  11  ( 31 ) and the first bonding portion  12  ( 32 ) or separately therefrom. The battery main body  4  is inserted into the pan  11  ( 31 ) and the electrode terminals  5  connected to the battery main body  4  are arranged to be exposed outward. The first bonding portion  12  ( 32 ), which is a flange of the pan  11  ( 31 ), and the second bonding portion  14  ( 34 ), which is a marginal area of the cover portion  15  ( 35 ), are attached to each other, forming a closed space inside the case  10  ( 30 ). The above manufacturing method is schematically described. In an actual case, a step for storing gas generated when the battery main body  4  is charged or discharged in the gas receiving portion, which will be described with reference to FIG.  5 . 
     FIG. 5 is a view for explaining a method for forming the secondary battery case shown in FIG. 1 in large quantities using a plate material. 
     Referring to the drawing, a plate material  51  is sectioned as indicated by the dotted lines and a unit case  54  can be formed per section. Each unit case  54  has a  1 s pan  52  and a gas receiving portion  55  of the battery main body. The gas generated in the battery pan  52  can be exhausted to the gas receiving portion  55  through a path  56 . When a battery is manufactured including a battery main body in a battery case, the battery main body is contained in the battery pan  52 . Next, a cover portion  53  covers over both the battery pan  52  and the gas receiving portion  55 , forming a seal. At this time, the path  56  is kept in an open state. When the battery main body charges and discharges, the gas generated from the battery main body flows toward the gas receiving portion  55  through the path  56  from the battery pan  52 . When the gas is gathered in the gas receiving portion  55 , the path  56  is closed. Finally, the gas receiving portion  55  is removed in a severing process. 
     The unit case  54 , as shown in FIG. 5, can be formed by severing the material along the line indicated by a dot-dash-dot line after the battery main body pan  55 , the gas receiving portion  55 , and the path  56  are formed per section through a predetermined process such as in a press. 
     In another embodiment, a separately manufactured battery main body is inserted in the pan  52  before the material  51  is severed along a dashed line extending in a lengthwise direction of the material  51  and along a dashed line extending in a widthwise direction thereof. Next, the cover portion  53  is folded concurrently so that the cover portion  53  is closely coupled to the pan  52 . Next, the battery main body is charged/discharged and the path  56  is closed. Finally, the material  51  is severed in a lengthwise direction so that the gas receiving portion  52  is removed and simultaneously each unit case can be separated. 
     In yet another example, separately from the severance of the portions indicated by the dotted lines, the portion where the pan  52  is formed and the portion where the cover portion  53  is formed are severed and separated from each other and thus the battery case shown in FIG. 3 can be manufactured. 
     FIGS. 6 and 7 are sectional views taken along the lines VI—VI and VII—VII of FIG.  2  and FIG. 8 is a sectional view taken along the line VIII—VIII of FIG.  4 . These drawings show methods of attaching the first bonding portion  12  ( 32 ) to the second bonding portion  14  ( 34 ). 
     FIG. 6 shows a surface bonding method, in which the first bonding portion  12  ( 32 ) and the second bonding portion  14  ( 34 ) are attached to each other without deformation. Although various attaching methods can be used, arc welding is preferred. 
     FIG. 7 shows an embossing method, in which an embossed portion is formed at the corresponding portions of the first bonding portion  12  ( 32 ) and the second bonding portion  14  ( 34 ) to increase the bonding strength. 
     FIG. 8 shows a linear method, in which concave and convex portions are formed at the corresponding portions of the first bonding portion  12  ( 32 ) and the second bonding portion  14  ( 34 ). This method also increases the bonding strength. 
     As described above, in secondary batteries according to the present invention, the case having a pan for accommodating a battery main body, a cover portion for closing the pan, and a bonding portion extended along the edge of the pan and the cover portion can be easily manufactured. Also, since the bonding portions can be attached by one of a surface method, an embossing method, and a linear method, mass production of the case is possible and the bonding portions are connected together firmly.