Abstract:
A secondary battery comprises a bare cell comprising an electrode assembly and a pouch housing the electrode assembly, wherein the bare cell comprises a first side at one end of the bare cell; a molded portion covering at least a part of the first side of the bare cell; and a circuit module disposed over the molded portion.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to and the benefit of U.S. Provisional Application No. 61/323,752 filed on Apr. 13, 2010, the entire content of which is incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    Embodiments of the invention relates to a secondary battery. In particular, embodiments are directed to a secondary battery having an improved combination of a bare cell and a printed circuit module. 
         [0004]    2. Description of the Related Art 
         [0005]    Many studies on secondary batteries are performed in various fields, since there are many applications for secondary batteries. In particular, lithium ion secondary batteries typically have an operation voltage of 3.7V, which is three times higher than nickel-cadmium batteries and nickel-hydrogen batteries. Because it provides higher energy intensity per unit weight, the use of lithium ion secondary batteries as the power source of portable electronic devices is rapidly increasing. 
         [0006]    The lithium ion secondary battery can accumulate high energy within itself. If an internal short occurs within the lithium ion secondary battery, the energy accumulated in the lithium ion secondary battery will be discharged in a short time, resulting in the lithium ion secondary battery burning out or even exploding. To avoid those risks, the lithium ion secondary battery is provided with a variety of safety components. The safety components are commonly electrically connected with the bare cell by welding connection terminals, e.g. a lead plate, to the bare cell. 
         [0007]    These safety components can cut off the electric connection between the bare cell and an outside electric load, resulting in prevention of flow of electric current, in cases where the battery is overcharged or excessively heated. For the safety components, a protecting circuit, a PCT (Positive Temperature Coefficient; hereafter “PCT”) element, or a bimetal may be used. 
         [0008]    A bare cell may be accommodated in a case with safety components equipped. Alternatively, a bare cell may not be accommodated in a case. Without the use of a case, the size and the weight of a secondary battery may be reduced, resulting in the reduction of the size and the weight of portable devices equipped with secondary batteries, as well. However, secondary batteries without cases might have poor mechanical strength or heat resistance at the connecting section between the bare cell and the safety components. When external stroke is experienced, the connection section may be damaged, thereby causing safety problems in the batteries. 
         [0009]    Further, in existing pouch type batteries, it is difficult to perform tab bending because an insulating tape is typically required for the sealing section of the pouch, which has relatively low mechanical strength. Further, because the low mechanical strength of the combination of the covering material and the PCM is correspondingly poor, safety problems may occur in the batteries. 
       SUMMARY 
       [0010]    Embodiments of the present invention increase the productivity by improving a combination of a bare cell and a PCM and fixing a position of the PCM in the bare cell. 
         [0011]    In particular, in a pouch type secondary battery, the mechanical strength of a sealing section is improved. Therefore, bending taps is done easily without using an insulating tape. The pouch type secondary battery further may include a covering material with the top and bottom exposed. Therefore, the PCM is more firmly combined with the bare cell and the strength of the second battery is increased by the covering material, providing for a secondary battery having improved safety. 
         [0012]    According to an embodiment, a pouch type secondary battery includes a bare cell comprising an electrode assembly and a pouch housing the electrode assembly, wherein the bare cell comprises a first side at one end of the bare cell; a molded portion covering at least a part of the first side of the bare cell; and a circuit module disposed over the molded portion. 
         [0013]    According to another embodiment, the pouch type secondary battery further comprises at least one tab extending from the electrode assembly and the pouch, wherein the molded portion is formed along one end of the pouch, and wherein the tab is exposed through an opening in the molded portion. 
         [0014]    According to another embodiment, the exposed tab is folded over the molded portion and parallel to the first side of bare cell. The molded portion may also further extend outwards on edges of the bare cell adjacent to the at least one lateral edge, on opposite ends of the lateral edge. The molded portion may contact substantially an entire long side of the circuit module. The molded portion further contacts sides of the circuit module adjacent to the long side, on opposite ends of the long side. The molded portion may further extend outwards on an edge of the bare cell opposite to the at least one lateral edge. 
         [0015]    According to an embodiment, the molded portion is rounded, polygonal or rectangular at both sides of the bare cell. 
         [0016]    According to an embodiment, the molded portion further comprises at least one structure over the first side to position the circuit module. 
         [0017]    According to an embodiment, the molded portion comprises at least two different structures over the first side to position the circuit module. 
         [0018]    According to an embodiment, the secondary battery further comprises a case covering the circuit module, wherein the case comprises one or more grooves; and one or more protrusions formed on a surface of the molded portion corresponding to the one or more grooves, wherein the molded portion is coupled to the case by inserting the protrusions into the grooves. 
         [0019]    According to an embodiment, the secondary battery further comprises an adhesive to adhere the molded portion to the case. 
         [0020]    According to an embodiment, the molded portion is formed only along an inner surface of a long side of the end of the pouch. 
         [0021]    According to an embodiment, the molded portion is formed along inner and outer surfaces of a long side of the end of the pouch. 
         [0022]    According to an embodiment, the secondary battery further comprises an external material around the bare cell, wherein the external material has upper and lower openings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    The accompanying drawings, together with the specification illustrate certain embodiments of the present invention, and, together with the description, serve to explain the principles of the present invention. 
           [0024]      FIG. 1  is a perspective view showing the upper section of a pouch type bare cell; 
           [0025]      FIG. 2A  is a perspective view showing a conventional pouch type secondary battery; 
           [0026]      FIG. 2B  is a view showing tab-bending according for a conventional pouch type secondary battery; 
           [0027]      FIG. 3A  is a perspective view showing a pouch type secondary battery according to an embodiment of the present invention; 
           [0028]      FIG. 3B  is a view showing tab-bending of the second battery according to an embodiment of the present invention; 
           [0029]      FIG. 4A  is a view showing a side of a molding section, a PCM, and a case covering the PCM, in the second battery according to an embodiment of the present invention; 
           [0030]      FIG. 4B  is a view showing the inside of a PCM case according to an embodiment of the present invention; 
           [0031]      FIG. 5A  is a view showing a covering material and a pouch type secondary battery according to an embodiment of the present invention; 
           [0032]      FIG. 5B  is a perspective view showing a pouch type secondary battery further including a covering material according to an embodiment of the present invention; 
           [0033]      FIG. 6  is a view showing a conventional can type bare cell; and 
           [0034]      FIG. 7  is a view showing a can type secondary battery according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0035]    Embodiments of the present invention are described hereafter in detail with the accompanying drawings. However, the present invention may be changed and modified in various ways within the scope described in the claims; therefore, it can be understood by those skilled in the art that the description below only illustrates certain embodiments. 
         [0036]    Even if the same components are shown in different figures of the drawings, it should be noted that they are represented by as many of the same reference numerals or characters as possible. In addition, the size or thickness may be exaggerated or reduced in the drawings for the convenience of description and clarity, and may be different from the thickness or size of the actual layers. 
         [0037]    Embodiments of the present invention are described hereafter in detail with reference to the drawings. 
         [0038]      FIG. 1  is a view showing a typical bare cell for pouch type secondary batteries, and  FIGS. 2A and 2B  are views showing the attachment of an insulating tape to the sealing section of a bare cell and the tap is bent according to the related art. 
         [0039]    Referring to  FIG. 1 , a bare cell  10  is formed by inserting an electrode assembly into a pouch. The electrode assembly typically includes a negative plate, a positive plate, and a separator. Further, the electrode assembly has taps  30  electrically connected with the plates, respectively. The bare cell  10  shown in  FIG. 1  is included in a pouch type secondary battery. The pouch type secondary battery includes a sealing section  20  sealing the pouch. The taps  30  are partly exposed to the outside through the sealing section  20 , respectively. The sealing section  20  is formed by applying heat and/or pressure to the edge of the pouch, using a heat-sealable material. 
         [0040]    In  FIGS. 2A and 2B , bending the taps  30  improves the electrical connection between the PCM and the bare cell  10 . An insulating tape  40  is attached to the contact section of the pouch and the taps  30 , before bending the taps  30 . The insulating tape  40  is provided only to prevent the short circuit with no other function, even though it is quite expensive. Further, the sealing section  20  does not have enough strength to support the taps  30  in bending. Accordingly, it is difficult to uniformly bend the taps  30 . 
         [0041]      FIGS. 3A and 3B  show a second battery according to the present invention, in which a molding section is formed at the sealing section of a pouch and the molding section has a stepped height. 
         [0042]    A pouch type secondary battery according to embodiments comprises a PCM, a case covering the PCM, a bare cell including an electrode assembly, and a pouch accommodating the electrode assembly. The pouch has a sealing section, through which taps  30  are partly exposed. The sealing section may include a molding section, and the molding section and a PCM mounting section may be formed on at least one side of the bare cell. 
         [0043]    Referring to  FIGS. 3A and 3B , the sealing section of the pouch has a molding section  50  between the pouch and the PCM, formed in the sealing section of the pouch. The molding section  50  may cover only one cross section  50   a  of the PCM in the sealing section. The molding section  50  also may cover one cross section  50   a  and both sides  50   b  of the PCM. Preferably, the molding section  50  covers the whole sealing section that contacts the PCM. 
         [0044]    The molding section  50   a  formed on the long side cross section of the sealing section can prevent a short circuit. The molding section  50   a  also may have functions similar to a conventional insulating tape in the process of bending the taps  30 . In addition, the molding section  50  may increase the mechanical strength of the sealing section  20 . 
         [0045]    The molding section  50  may cover both the sides and the bottom of the bare cell  10 . The shape of the molding section  50  may be modified into a flat plane shape, a polygonal shape, or a rounded shape. The shape depends on the design of the secondary battery.  FIGS. 3A-3B  show a rounded shape  53 . As described above, the molding section  50  covering the sides of the bare cell  10  functions as a case for the secondary battery. In addition, the secondary battery should have a certain mechanical strength, even without an additional case. 
         [0046]    The molding section  50  may include a PCM mounting section  60 . The PCM mounting section  60  is where the PCM is positioned in the bare cell  10 . The PCM mounting section  60  may be formed on any side of the bare cell  10 . Preferably, the PCM mounting section  60  is formed adjacent to the tabs. 
         [0047]    Further, as shown in  FIGS. 3A and 3B , the PCM mounting section  60  may include PCM mounting structures  61  and  62 . The PCM mounting structure may be one or more, and include the first and second mounting structures  61  and  62 . The first and second mounting structures  61  and  62  are shown in  FIG. 3A . Preferably, the shapes of the first and second mounting structures  61  and  62  are different. The first and second mounting structures  61  and  62  can prevent the reverse insertion of the terminal of the PCM in the bare cell  10 . Therefore, the process of combining the PCM with the bare cell  10  is simplified, such that it is possible to reduce the rate of errors. 
         [0048]      FIG. 4A  shows an embodiment where the PCM and the case covering the PCM are connected to the molding section, and  FIG. 4B  shows the inside of the case. 
         [0049]    In  FIG. 4A , one or more protrusions are formed at the lower portion on the outside of the molding section  50 , and one or more grooves  81  are formed at positions corresponding to the protrusions  52  in the case  80  covering the PCM. After the taps  30  are bent, the PCM  70  is placed in the PCM mounting section. Thereafter, the case  80  covers the molding section  50  and the PCM  70  of the bare cell  10 . At this point, the case  80  contacts the outside of the molding section  50 , and the protrusions  52  combines with the grooves  81  ( FIG. 4B ). 
         [0050]    In  FIG. 4A , the protrusions  52  are formed at the lower portion on the outside of the molding section  50 , and the grooves  81  are formed at the positions corresponding to the protrusions in the case  80 . Therefore, the protrusions and grooves have only to be formed at the positions corresponding to each other, such that the position and the number of the protrusions and grooves can be properly modified in accordance with the design of the secondary battery. In addition, adhesive materials may be further used to secure a more firm combination. Alternatively, it is possible to use only adhesive materials such as glue when the protrusions or the grooves are not formed. 
         [0051]    Referring to  FIGS. 2A and 2B , the conventional pouch type secondary battery had the problem of low mechanical strength of the sealing section  20  and the taps  30 . Therefore, it was difficult to bend the taps  30 , and the bending shapes were not uniform. 
         [0052]    In  FIGS. 3A-3B , the sealing section of the secondary battery according to an embodiment of the present invention has improved mechanical strength by the presence of molding section  50 . The molding section can be formed only inside the long side of the sealing section. In addition, the molding section can further have a molding surface covering the outside of the long side of the sealing section. Preferably, the molding surfaces have the stepped height  51  where the taps  30  of the sealing section are formed. Preferably, the lower section is inside. The molding section  50  makes the sealing section stronger, and the stepped height  51  makes bending the taps  30  easier. Therefore, the bent taps have a uniform shapes (see  FIG. 3B ). 
         [0053]    On the other hand,  FIGS. 5A-5B  are views showing a pouch type secondary battery according to another embodiment of the present invention. The pouch type secondary battery further includes a covering material with the top and bottom open. 
         [0054]      FIG. 5A  shows a covering material and a bare cell before a molding section is formed in a sealing section, and  FIG. 5B  shows the bare cell including the covering material. 
         [0055]    In a pouch type secondary battery according to embodiments, the bare cell  10  includes the covering material  90 . As described above, the covering material  90  may cover the bare cell  10  before the molding section is formed in the sealing section  20 . The covering material  90  may cover the bare cell  10  without the top and bottom of bare cell. The bare cell  10 , except for the top and bottom, is partially or entirely enclosed by the covering material  90 . Preferably, as shown in the figure, the bare cell  10  is entirely enclosed except for the top and bottom of bare cell. Further, any one of the top and bottom opening parts may include the sealing section with the taps  30 . In  FIG. 5 , the taps of the bare cells are exposed. 
         [0056]    The covering material may be a sheet shape or a tube shape. In a sheet shape, as shown in the figure, the sheet-shaped covering material  90  covers the bare cell  10 . One edge and the other edge of the covering material  90  may be attached by an adhesive material, such as glue (see  FIG. 4 ). Alternatively, the bare cell  10  may be inserted into the covering material when the covering material is a tube shape. 
         [0057]    In the bare cells further including the covering material  90  according to embodiments, the covering material  90  supports the secondary battery, such that the mechanical strength of the sealing section is improved. Therefore, it is possible to more easily form the molding section and more firmly combine the bare cell  10  with the PCM. 
         [0058]    Further, the covering material  90  can increase the mechanical strength of the secondary battery. Since the covering material is a non-conducting material, the secondary battery is afforded electrical safety. The pouch type secondary battery further includes the covering material  90  according to embodiments of the present invention. The covering material  90  increases the mechanical strength of the secondary battery, and allows the secondary battery to meet electrical safety requirements. 
         [0059]    An embodiment of a can type secondary battery according to another aspect of the present invention is described hereafter. 
         [0060]      FIG. 6  shows a can type bare cell and a lead plate, and  FIG. 7  shows a can type secondary battery having the molding section according to embodiments of the present invention. 
         [0061]    Referring to  FIG. 6 , an electrode assembly (not shown) includes a negative plate, a positive plate, and a separator. The electrode assembly accommodated in a can  110 , and a cap assembly  120  closes the opening of the can  110  using a welding process. 
         [0062]    In a conventional can type secondary battery, several components would be required to fix the PCM to a bare cell  100  and electrically connect it to the exterior of the battery. As shown in  FIG. 6 , fixing protrusions  122  would be needed to fix the position of the PCM on the cap assembly for conventional batteries. Moreover, a terminal component, such as the lead plate  123  would be weld to the cap assembly for electrical connection with the bare cell  100 . The material cost of the battery was increased by the fixing protrusions  122  and the lead plate  123 , and the manufacturing cost of the battery was increased by the additional processes, such as welding. Furthermore, the protrusions  122  and the lead plate  123  are not sufficient in stably fixing, physically and electrically, the PCM etc. to the bare cell  100 . 
         [0063]    Therefore, a can type secondary battery according to embodiments of the present invention includes a PCM, a case covering the PCM, an electrode assembly, a can, and a cap assembly. The can accommodates the electrode assembly, and the cap assembly closes an opening of the can. Further, at least one side of the bare cell includes a molding section and a PCM mounting section thereon. 
         [0064]    Unlike the conventional secondary battery, in the secondary battery according to embodiments of the present invention, the molding section is formed to fix and electrically connect the PCM the bare cell. Therefore, the secondary battery according to embodiments of the present invention does not need fixing protrusions or a lead plate. 
         [0065]      FIG. 7  is a view showing a can type secondary battery according to an embodiment of the present invention. 
         [0066]    Referring to  FIG. 7 , the molding section  200  is formed at the top of the bare cell  100  and positioned between the bare cell and the PCM. 
         [0067]    The molding section  200  may be in contact with only one cross section  200   a  of the PCM. Alternatively, the molding section  200  may cover one cross section  200   a  and both sides  200   b  of the PCM. The larger the contact area between the molding section  200  and the PCM, the more the PCM is firmly combined with the bare cell  100 . Further, the molding section  200  may be in partial or entire contact with the cross section of the PCM. Preferably, the molding section  200  is in contact with the entire cross section of the PCM. In the figure, the molding section  200  is in contact with one long side and both cross sections of the PCM. 
         [0068]    The molding section  200  may be formed on any section of the bare cell  100 . However, it is preferable to be formed on the cap assembly ( 120  in  FIG. 6 ) to be easily electrically connected with the PCM. 
         [0069]    The molding section may extend, for example, to include both sides and bottom of the bare cell  100 . The molding section extending at both sides of the bare cell  100  may be properly modified depending on the design of the secondary battery. For example the shape of the molding section may have a flat plane shape, a polygonal shape, or a rounded shape.  FIG. 7  shows an embodiment in which the molding section  200  has a rounded shape. The molding section covering the sides of the bare cell, as described above, can function as a case of the secondary battery. Therefore, it is possible to improve mechanical strength of the conventional can type secondary battery, even without adding a case to the secondary battery. Further, it was difficult to implement changes to the appearance of the conventional can type secondary battery in accordance with changes in the design of electronic devices. In the can type secondary battery according to embodiments of the present invention, it is possible to easily change the appearance of the can type secondary battery by simply changing the shape of the molding section. 
         [0070]    Further, the molding section  200  may include a PCM mounting section  300 . The PCM mounting section  300  is where the PCM is seated in the bare cell  100  and may be formed on any side of the bare cell  100 . It is preferable to form the PCM mounting section to a section where an electrode  121  of the bare cell  100  is formed, in order to easily form an electrode  121  in the PCM mounting section  300 . 
         [0071]    As shown in  FIG. 7 , the PCM mounting section  300  may include PCM mounting sections  310  and  320 . The PCM mounting structure may be one or more. In  FIG. 7 , the first and second mounting structures  310  and  320  are shown. Preferably, the shapes of the first and second mounting structures  310  and  320  are different. The first and second mounting structures  310  and  320  can prevent the reverse insertion of the terminal of the PCM in the bare cell  10 , and fix the position of the PCM. 
         [0072]    As described above, the molding section  200  can include protrusions  210 , and the case covering the PCM can include one or more grooves. The protrusions  210  may be formed at the lower portion on the outside of the molding section  200 , and the grooves corresponding to the protrusions may be formed on the case covering the PCM. The molding section  200  and the case covering the PCM can be combined by the protrusions and the grooves. The bare cell  100  may be combined with the PCM and then the PCM may be covered with the case. In this structure, the case is in contact with the outside of the molding section and combined with the molding section at the contact sections by the protrusions and the grooves. The sections with the protrusions and the grooves have only to correspond to the protrusions and the groove, without being fixed. In addition, it is possible to achieve the combination with adhesive materials such as glue when the protrusions or the grooves are not formed.