Case containing secondary battery

A case for a secondary battery includes a pan having a space for accommodating a battery main body and an opening. A first bonding portion extends along the edge of the pan. A second bonding portion extends along the edge of the cover portion for corresponding attachment to the first bonding portion when folded onto the pan. Thus, mass production of the case is possible and the bonding portion becomes firm when the first and second bonding portions are bonded together.

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, a lithium secondary battery is
 manufactured after the battery main body is inserted in a case in the 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.

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
 90.degree. 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 terminal 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 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 8 are sectional views taken along the lines VI--VI and VII--VII
 of FIG. 4 and FIG. 7 is a sectional view taken along the line VII--VII of
 FIG. 2. 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.