Abstract:
A secondary battery includes a can having an open end and housing an electrode assembly; a cap assembly sealing the open end of the can; and an insulating case located between the electrode assembly and the cap assembly, the insulating case comprising folding protrusions protruding from a peripheral surface of the insulating case and oriented such that a first side of the folding protrusion contacts the insulating case and a second side of the folding protrusion contacts the can.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2010-0069104, filed on Jul. 16, 2010, in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     Embodiments relate to a secondary battery. 
     2. Discussion of Related Art 
     Recently, as portable electronic devices have been significantly reduced in size and weight, many studies for secondary batteries used as a power supply of the devices have been conducted. Examples of secondary batteries include nickel-cadmium battery, a nickel-hydrogen batteries, a nickel-zinc batteries, and a lithium secondary batteries. Of those batteries, the lithium secondary battery can be made rechargeable, decreased in size and increase in capacity, and has high operation voltage and energy density per unit weight, such that it has been widely used for high-technology electronic devices. 
     A rectangular secondary battery of the lithium secondary battery is formed by locating an electrode assembly including an anode plate, a cathode plate, and a separator therebetween in a can together with an electrolyte, and then sealing the upper end of the can with a cap assembly. Further, an insulating case is inserted in the upper end of the can. 
     The insulating case has a hole for an anode tap and a hole for a cathode tap and is inserted to prevent a short circuit between the top of the electrode assembly received in the can and the bottom of the cap assembly. Further, the insulating case can prevent a short circuit that may be generated by contact between the cathode and anode taps and the inner wall of the can. Further, the insulating case can prevent the electrode assembly from moving within the can. 
     However, the insulating case can become dislodged and separated from the can when the elasticity of the electrode assembly in the can is excessive. Further, when the thickness of the electrode assembly is large, the top of the can may open causing the insulating case to loosen and separate from the can during transportation. Further, the inner side of the can may be scratched by the outer side of the insulating case and burrs are generated, such that welding between the can and the can assembly is deficient resulting in leakage of the electrolyte. 
     SUMMARY 
     An embodiment provides a secondary battery having an insulating case stably seated in the upper portion in a can and by the formation of folding protrusions on a pair of long sides of the insulating case. 
     According to one embodiment, a secondary battery includes a can having an open end and housing an electrode assembly; a cap assembly sealing the open end of the can; and an insulating case located between the electrode assembly and the cap assembly, the insulating case including folding protrusions protruding from the insulating case and oriented such that a first side of the folding protrusion contacts the insulating case and a second side of the folding protrusion contacts the can. 
     In one embodiment, the folding protrusions are spaced from a bottom of the insulating case, for example, by between about ⅙ to about ⅚ of the height of the insulating case. Additionally, the folding protrusions may be on opposing long sides of the pair of long sides and may be substantially symmetrical to each other. 
     Further, in one embodiment, the folding protrusions each have a groove substantially adjacent to a hinge at which the folding protrusion is folded. Additionally, the secondary battery as claimed in claim  1 , wherein a plurality of notches are on the insulating case and wherein each of the folding protrusions protrude from one of the notches. In one embodiment, a depth of the notch is substantially equal to a thickness of the folding protrusions. 
     As described above, according to the present invention, it is possible to prevent an insulating case inserted and fixed at the upper portion in a can from being scratched by the inner side of the can and the insulating case from separating outside from the can by forming folding protrusions on a pair of long sides of the insulating case to more stably seat the insulating case at the upper portion in the can. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, together with the specification, illustrate exemplary embodiments of the present invention, and, together with the description, serve to explain the principles of the present invention. 
         FIG. 1  is an exploded perspective view showing a secondary battery according to an embodiment of the present invention; 
         FIG. 2  is a plan view showing in detail the insulating case shown in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view taken along the line A-A′ of  FIG. 1 ; 
         FIG. 4A  is a cross-sectional view of the insulating case of  FIG. 1  resting on the can; 
         FIG. 4B  is a cross-sectional view when the insulating case of  FIG. 1  is being inserted in the can; 
         FIG. 4C  is a cross-sectional view when the insulating case of  FIG. 1  has been inserted and seated in the can; and 
         FIG. 5  is a plan view showing an insulating case according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, only certain exemplary embodiments of the present invention have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. In addition, when an element is referred to as being “on” another element, it can be directly on the another element or be indirectly on the another element with one or more intervening elements interposed therebetween. Also, when an element is referred to as being “connected to” another element, it can be directly connected to the another element or be indirectly connected to the another element with one or more intervening elements interposed therebetween. Hereinafter, like reference numerals refer to like elements. 
     A secondary battery according to the present invention is described hereafter in detail with reference to the accompanying drawings showing embodiments of the present invention. 
       FIG. 1  is an exploded perspective view showing a secondary battery according to an embodiment of the present invention. 
     Referring to  FIG. 1 , a secondary battery according to an embodiment of the present invention includes a can  10  having a open end and accommodating an electrode assembly  12 , a cap assembly  20  sealing the opening of the can  10 , and an insulating case  70  positioned between the electrode assembly  12  and the cap assembly  20  and inserted at the upper portion in the can  10 . Further, folding protrusions  71  are formed at positions on the outer side of the insulating case  70  which is in contact with the can  10 . 
     The folding protrusions  71  are folded upward (i.e., towards the cap assembly) from the insulating case  70  when being inserted in the can  10  such that one side is in contact with the outer side of the insulating case  70  and the other side is in contact with the inner side of the can  10 . Therefore, the insulating case  70  is stably seated at the upper portion in the can  10 , such that it is possible to prevent the outer side of the insulating case  70  from being scratched by the inner side of the can  10  and to reduce the likelihood of the insulating case  70  from separating from the can  10 . In other words, the folding protrusions  71  folded upward from the insulating case  70  prevent the insulation case from dislodging from the can  10  by compression generated therefrom. 
     The horizontal (i.e., lateral) cross section of the insulating case  70  is substantially rectangular with a pair of long sides  75   a  and a pair of short sides  75   b  forming the outer periphery  75  of the insulating case  70 . In embodiments, the folding protrusions  71  may be formed on either the pair of short sides  75   b  or on the pair of long sides  75   a , or on both the short sides and the long sides. In this configuration, the horizontal cross section of the insulating case may be a rectangle with the corners rounded, but the shape is not limited thereto. 
     In one embodiment, the folding protrusions  71  are symmetrically formed at the same positions on the long sides  75   a  opposite to each other, such that it is possible to prevent an imbalanced insertion in which the insulating case  70  inclines to one of the long sides  75   a  when being inserted in the can  10 . Only one pair of folding protrusions  71  may be formed, but two pairs may be formed, as shown in the figures, to more stably seat the insulating case  70  and in other embodiments additional numbers of folding protrusions may be formed. 
     Further, the folding protrusions  71  are spaced from the bottom  74  of the insulating case  70 , which is described below with reference to  FIG. 3 . 
     The insulating case  70  is positioned between the electrode assembly  12  and the cap assembly  20  for electric insulation, and in detail, it is kept inserted at the upper portion in the can  10 . The insulating case  70  is generally made of hard plastic resin having excellent electric insulation. Therefore, when the insulating case  70  is inserted in the can  10 , it is not substantially deformed by the electrolyte and it is easy to ensure insulation between the electrode assembly  12  and the cap assembly  20 . However, when the insulating case  70  is made of hard plastic resin, the elasticity is small and it may be difficult to insert the insulating can  10 . As such, the insulating case  70  includes a base  74  and a support  75  to be stably inserted in the can  10 . In this configuration, the base  74  is the bottom of the insulating case  70  which was described above and the support  75  is the outer side of the insulating case  70 ; therefore, the base  74  and the support  75  are hereafter referred to the bottom and the outer side of the insulating case  70 , respectively, for the convenience of the description. 
     In more detail, the bottom  74  of the insulating case  70  is formed of a plate having a substantially uniform thickness and has a shape similar to the horizontal cross-sectional shape of the can  10 . Further, in one embodiment the bottom  74  of the insulating case  70  is slightly larger than the cross section of the can for press-fitting in the can  10 . An electrolyte inlet and lead-through holes  72  are formed through the bottom  74  of the insulating case  70 . 
     Further, the outer side  75  of the insulating case  70  is integrally formed with the bottom  74  along the edge of the bottom  74 . The outer side  75  of the insulating case  70  makes it possible to ensure a gap between the cap assembly  20  and the bottom  74  of the insulating case  70  when the cap assembly  20  and the insulating case  70  are accommodated in the can  10 . 
     Since the folding protrusions  71  are formed on the pair of long sides  75   a  of the outer side  75  of the insulating case  70 , the insulating case  70  can be more easily seated when the insulating case  70  is press-fitted in the can  10 , such that the insulating case  70  can be prevented from separating from the can  10 . 
     The electrode assembly  12  is formed by locating a separator  14  between an anode plate  15  and a cathode plate  13 . An anode tap  16  is connected to the anode plate  15 , protruding upward from the electrode assembly  12 , and a cathode tap  17  is connected to the cathode plate  13 , protruding upward from the electrode assembly  12 . The anode tap  16  and the cathode tap  17  are spaced from each and are electrically connected in the electrode assembly  12 . Further, a lamination tape  18  is wound at the portion where the anode tap  16  and the cathode tap  17  are drawn from the electrode assembly  12 . Further, the lamination plate  18  blocks heat generated from the anode tap  16  or the cathode tap  17  and prevents the electrode plate  12  from being pressed by the edges of the anode tap  16  and the cathode tap  17 . 
     In this configuration, the anode tap  16  and the cathode tap  17  are electrically connected with the anode plate  15  and the cathode plate  13  of the electrode assembly, respectively, and are drawn out to the opening of the can  10 . In this configuration, the anode tap  16  and the cathode tap  17  are electrically connected with the can  10  or the terminal plate  60  through the lead-through holes  72  of an insulating case  70  fixed to the upper portion of the electrode assembly  12  in the can  10 . 
     The anode plate  15  and the cathode plate  13  are formed by dry coating a slurry on a thin aluminum layer and a thin copper layer, respectively. The slurry contains the active substances of the anode plate  15  and the cathode plate  13  and a fixing agent bonding the active substances to the thin metal layer. Further, for lithium secondary batteries, although the anode active substance is usually a lithium containing oxide and the cathode active substance may be any one of hard carbon, soft carbon, graphite, and carbon substances, the present invention is not limited to those lithium secondary batteries. 
     The can  10  accommodates the electrode assembly through the opening and the horizontal cross section of the can  10  is formed in a rectangle with the corners rounded, including a pair of short sides  10   a  and a pair of long sides  10   b . The horizontal cross-sectional shape of the can  10  is not limited to the above, and the horizontal cross-sectional shape of the can  10  may be a rectangle or an ellipse. In one embodiment, the can  10  is made of aluminum or an aluminum alloy that is light and has flexibility. Further, the can  10  may be manufactured by a deep drawing method. 
     The cap assembly  20  includes a cap plate  40 , an electrode terminal  30 , an insulating plate  50 , a terminal plate  60 , and a gasket  35 . The cap plate  40  can define one side of the can  10  by sealing the opening of the can  10  when the cap assembly  20  and the can  10  are combined. For this configuration, the cap plate  40  may be attached to the opening of the can  10  by, for example, welding, etc. Further, the cap plate  40  is electrically connected with any one of the anode tap  16  and the cathode tap  17  drawn out through the lead-through holes  72  of the insulating case  70 . Further, the cap plate  40  has a first terminal hole  41  for combination with a gasket  35  and an electrolyte inlet  42  for injecting an electrolyte. The electrolyte inlet  42  formed in the cap plate  40  is used as a channel for injecting an electrolyte into the can  10 . Further, the electrolyte inlet  42  is sealed with a cap  43  after the electrolyte is injected. 
     The gasket  35  is provided for insulation between the electrode terminal  30  and the cap plate  40  and has a first terminal hole  41  for combination with the electrode terminal  30 , and the electrode terminal  30  is combined with the gasket  35  through the first terminal hole  41 . 
     Further, the insulating plate  50  is located between the cap plate  40  and the terminal plate  60  for insulation and a second terminal hole  51  through which the electrode terminal  30  passes is formed in the insulating plate  50 . 
     Additionally, the terminal plate  60  is electrically connected with the electrode terminal  30  by the third terminal hole  61  and the terminal plate  61  is electrically connected with the other one of the anode tap  16  and the cathode tap  17  which is not connected with the cap plate  40 . In other words, when the cap plate  40  is electrically connected with the anode tap  16 , the terminal plate  60  is connected with the cathode tap  17  and accordingly, electric connection between the electrode terminal  30  and the cathode tap  17  can be achieved. 
       FIG. 2  is a plan view showing in detail the insulating case shown in  FIG. 1 . 
     Referring to  FIG. 2 , two folding protrusions  71  are formed on the pair of long sides  75   a  of the insulating case  70 , with the folding protrusions on opposing sides generally corresponding to each other. In this configuration, the width W of the folding protrusion  71  may be within the range of about 0.5 mm to about 2.0 mm. When the width W of the folding protrusion  71  is less than about 0.5 mm, it is difficult to not only form the folding protrusion  71 , but also to sufficiently prevent the insulating case  70  from protruding from the can  10 . Further, when the width W of the folding protrusion  71  is more than about 2.0 mm, the folding protrusion  71  is not easily folded upward when being inserted into the can  10 , such that it is difficult to insert the insulating case  70  in the can  10 . Accordingly, in one embodiment, the width W of the folding protrusion  71  is in the range of about 0.5 mm to about 2.0 mm. 
       FIG. 3  is a cross-sectional view taken along the line A-A′ of  FIG. 1 . 
       FIG. 3  shows the insulating case  70  with the folding protrusions  71 , when seen in a cross section horizontally with the cross-sectional side of the insulating case  70 . The folding protrusions  71  formed on the pair of long sides  75   a  (see  FIG. 1 ) of the insulating case  70  are spaced at a distance from the bottom  74  (see  FIG. 1 ) of the insulating case  70 . 
     In this configuration, the distance H 1  between the folding protrusions  71  and the bottom  74  of the insulating case  70  may be about ⅙ to about ⅚ of the height H 2  of the insulating case  70 . When the distance is less than about ⅙ of the height H 2  of the insulating case  70 , it may not be possible to easily insert the insulating case  70  into the can  10 , and when it is more than about ⅚, folding the folding protrusions  71  has little effect. 
     Further, in one embodiment, the length L 1  of the folding protrusions  71  is smaller than the distance H 3  obtained by subtracting the distance H 1  from the bottom  74  from the height H 2  of the insulating case  70 . That is, the length L 1  should be determined such that the folding protrusions  71  do not protrude from the insulating case  70  after being inserted and folded in the can  10 . 
     Further, the thickness D 1  of the folding protrusions  71  is in the range of about 0.1 mm to about 0.5 mm. It is difficult to form the folding protrusions  71  when the thickness D 1  of the folding protrusions  71  is less than 0.1 mm. Further, when the thickness D 1  of the folding protrusion  71  is more than 0.5 mm, similar to when the width W (see  FIG. 2 ) of the folding protrusions  71  is large, the folding protrusion  71  is not easily folded upward when being inserted into the can  10 , such that it is difficult to insert the insulating case  70  in the can  10 . 
     As described above, the folding protrusions  71  are easily folded when the insulating case  70  is inserted into the can  10 , and the width W, the thickness D 1 , and the distance H 1  from the bottom  74  of the insulating case  70  should be appropriately determined for easy insertion. 
     Further, the folding protrusions  71  may have a groove  77  at the folded portion on one side (i.e., adjacent to a hinge at which the folding protrusion is folded). The grooves  77  allow the folding protrusions  71  to be easily folded when they are inserted into the case. 
       FIG. 4A  is a cross-sectional view of the insulating case  75  according to an embodiment of the present invention resting on the can before the insulating case is inserted in the can,  FIG. 4B  is a cross-sectional view of the insulating case being inserted in the can, and  FIG. 4B  is a cross-sectional view of when the insulating case has been inserted and seated in the can. 
     Referring to  FIGS. 4A to 4C , the distance between the inner sides of the can  10  which are in contact with the folding protrusions  71  is larger than the width of the short side  75   b  (see  FIG. 1 ) of the insulating case  70 , and smaller than the width of the short side  75   b  of the insulating case  70  including the folding protrusions  71 . Accordingly, the folding protrusions  71  are stopped by the uppermost end of the can  10  when the insulating case  70  is inserted into the can  10 . 
     Since the insulating case  70  is press-fitted in the can  10 , the folding protrusions  71  made of a material having strength less than the can are folded upward from the insulating case  70  by forcibly inserting the insulating case  70  into the can  10  from above. 
     Thereafter, the insulating case  70  is seated at the upper portion in the can  10 , in which the folded portions of the folding protrusions  71  are in contact with the long sides  75   a  of the insulating case  70  ( FIG. 4C ). As described above, it is possible to more stably seat the insulating case  70  at the upper portion in the can  10  by using the folding protrusions  71 , and it is also possible to prevent the outer side  75  of the insulating case  70  inserted and fixed at the upper portion in the case from being scratched by the inner side of the can  10 . Further, it is possible to prevent or reduce the likelihood of the insulating case  70  being separated from the can  10 . 
       FIG. 5  is a plan view showing an insulating case according to another embodiment of the present invention. 
     Referring to  FIG. 5 , notches  76  recessed inward toward a center of the insulation case are formed on the long sides  75   a  of the outer side of an insulating case and folding protrusions  71  may be formed at the notches  76 . In one embodiment, the notches  76  are recessed inward about as much as the thickness of the folding protrusions  71 . Since the folding protrusions  71  are folded upward from the insulating case  70  and pressed inside the can, the insulating case can be tightly inserted, even if the folding protrusions  71  are formed in the notches  76 . Further, it is possible to prevent the insulating case  70  from protruding from the can. 
     While the present invention has been described in connection with certain exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, and equivalents thereof.