Abstract:
A secondary battery module includes a plurality of secondary battery units each including at least one secondary battery, each secondary battery including an electrode assembly, a case accommodating the electrode assembly, and first and second electrode terminals electrically connected to the electrode assembly, wherein for at least the first secondary battery unit of the plurality of secondary battery units, each of the corresponding at least one secondary batteries further includes a short-circuit member electrically connected to the corresponding first electrode terminal and protruding to the outside of the case upon the internal pressure of the case reaching a high-pressure condition; at least one fuse connecting at least two of the plurality of secondary battery units to one another in series; and a short circuit connection member having a first side facing each of the short-circuit members of the at least one secondary battery of the first of the plurality of secondary battery units and a second side electrically connected to a second electrode terminal of a secondary batter of another of the plurality of secondary battery units.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2013-0141791, filed on Nov. 20, 2013, the entire content of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    Aspects of the present invention relate to a secondary battery module. 
         [0004]    2. Description of the Related Art 
         [0005]    A secondary battery module usually includes a plurality of secondary batteries connected in parallel/series as unit cells. Each of the unit cells includes an electrode assembly having a positive electrode and a negative electrode with a separator positioned therebetween, a case having a space to receive the electrode assembly therein, a cap assembly coupled to the case and sealing the case, and positive and negative terminals protruding from the cap assembly and electrically connected to positive and negative current collectors provided in the electrode assembly. 
         [0006]    In some instances, each of the unit cells has a membrane and a fuse installed to be electrically connected to the positive electrode terminal. The membrane makes contact with the negative electrode terminal when the internal pressure of the case increases due to overcharge of the unit cell, and creates short circuit between the positive and negative electrodes. When short circuit is created, the fuse is cut off, thereby blocking an electrical connection of the unit cell. 
         [0007]    As the number of secondary batteries included in a battery module increases, the number of membranes and fuses to be installed also increase, thereby increasing a probability of malfunction of an overcharge preventing safety device. Even during normal operation, most of the unit cells included in the secondary battery module may be unavoidably damaged. 
       SUMMARY 
       [0008]    Aspects of embodiments of the present invention are directed to a secondary battery module, which can reduce a probability of malfunction of an overcharge preventing safety device and can save the manufacturing cost by minimizing the number of components used in the secondary battery module. 
         [0009]    In accordance with one embodiment of the present invention, a secondary battery module includes a plurality of secondary battery units each including at least one secondary battery, each secondary battery including an electrode assembly, a case accommodating the electrode assembly, and first and second electrode terminals electrically connected to the electrode assembly, wherein for at least the first secondary battery unit of the plurality of secondary battery units, each of the corresponding at least one secondary batteries further includes a short-circuit member electrically connected to the corresponding first electrode terminal and protruding to the outside of the corresponding case upon the internal pressure of the case reaching a high-pressure condition; at least one fuse connecting at least two of the plurality of secondary battery units to one another in series, and a short circuit connection member having a first side facing each of the short-circuit members of the at least one secondary battery of the first of the plurality of secondary battery units and a second side electrically connected to a second electrode terminal of a secondary battery of another of the plurality of secondary battery units. 
         [0010]    The secondary battery module may further include a first connection member electrically connecting the first electrode terminals of the corresponding plurality of secondary batteries; and a second connection member electrically connecting the second electrode terminals of the corresponding plurality of secondary batteries. 
         [0011]    The fuse may electrically connect the second connection member of the first secondary battery unit and a first connection member of another of the plurality of secondary battery units. 
         [0012]    The fuse may have a smaller sectional area than the first connection members or the second connection members. 
         [0013]    On the high-pressure condition, the short circuit member may be inverted to electrically contact the first side of the short circuit connection member. 
         [0014]    When the short circuit connection member electrically contacts the short-circuit member, the current may be bypassed from the first secondary battery unit to the second electrode terminal of a secondary battery of the last secondary battery unit of the plurality of secondary battery units. 
         [0015]    The first side of the short circuit connection member may include at least one protrusion that protrudes toward a short-circuit member. 
         [0016]    As described above, the secondary battery module according to the present invention can reduce a probability of malfunction of an overcharge preventing safety device and can save the manufacturing cost by minimizing the number of components used in a secondary battery module. 
         [0017]    Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The objects, features and advantages of the present invention will be more apparent from the following detailed description in conjunction with the accompanying drawings, in which: 
           [0019]      FIG. 1  is a perspective view of a secondary battery module according to an embodiment of the present invention; 
           [0020]      FIG. 2  is a cross-sectional view of the secondary battery module, taken along the line I-I′ of  FIG. 1 ; 
           [0021]      FIG. 3  is a circuit view illustrating the flow of current during a normal charge operation of the secondary battery module shown in  FIG. 1 ; and 
           [0022]      FIGS. 4 and 5  are circuit views illustrating operation mechanism during an overcharge of a secondary battery module according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Hereinafter, an exemplary embodiment of the invention will be described in detail with reference to the accompanying drawings. In the following detailed description, certain exemplary embodiments of the present invention are 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. Like reference numerals generally designate like elements throughout the specification. Further, the use of “may” when describing embodiments of the present invention refers to “one or more embodiments of the present invention.” 
         [0024]      FIG. 1  is a perspective view of a secondary battery module according to an embodiment of the present invention. 
         [0025]    Referring to  FIG. 1 , the secondary battery module  100  according to an embodiment of the present invention includes a plurality of secondary battery units  100 A and  100 B, a first connection member  160 , which serves as a short circuit connection member, and a fuse  170 . In some embodiments, the secondary battery module  100  may further include second connection members  171  and  173 , third connection members  172  and  174  and an insulation film  180 . 
         [0026]    The plurality of secondary battery units  100 A and  100 B may include a plurality of secondary batteries. For example, as shown in  FIG. 1 , the secondary battery units  100 A and  100 B may include a first secondary battery unit  100 A and a second secondary battery unit  100 B connected to each other in series. The first secondary battery unit  100 A includes first to fifth secondary batteries  100 A 1 ,  100 A 2 ,  100 A 3 ,  100 A 4  and  100 A 5  connected to each other in parallel, and the second secondary battery unit  100 B includes sixth to tenth secondary batteries  100 B 1 ,  100 B 2 ,  100 B 3 ,  100 B 4  and  100 B 5  connected to each other in parallel. However, the secondary battery module  100  according to the present invention is not limited to that with the aforementioned configuration. The number of secondary batteries connected to each other in parallel and the number of secondary battery units connected to each other in series may vary according to the specification of the secondary battery module. 
         [0027]    In the secondary battery module  100  according to an embodiment of the present invention, the first secondary battery unit  100 A may be defined as being positioned in the first place in a row of secondary battery units and the second secondary battery unit  100 B may be defined as being positioned in the last place. In some embodiments, in the first secondary battery unit  100 A, the first secondary battery  100 A 1  is defined as being positioned in the first place in a row of secondary batteries, and the fifth secondary battery  100 A 5  is defined as being positioned in the last place. In other words, the first to fifth secondary batteries are defined as being arranged sequentially from  100 A 1  to  100 A 2 ,  100 A 3 ,  100 A 4  and to  100 A 5  in that order. In some embodiments, in the second secondary battery unit  100 B, the sixth secondary battery  100 B 1  is defined as being positioned in the first place in a row of secondary batteries, and the tenth secondary battery  100 B 5  is defined as being positioned in the last place. In other words, the sixth to tenth secondary batteries are defined as being arranged sequentially from  100 B 1  to  100 B 2 ,  100 B 3 ,  100 B 4  and to  100 B 5  in that order. For a better understanding of the present invention, the aforementioned arrangement order is defined according to the flow of the charge current of the secondary battery module  100 . 
         [0028]    The second connection members  171  and  173  and the third connection members  172  and  174  may connect the first to fifth secondary batteries  100 A 1 ,  100 A 2 ,  100 A 3 ,  100 A 4  and  100 A 5  to each other in parallel, and may connect the sixth to tenth secondary batteries  100 B 1 ,  100 B 2 ,  100 B 3 ,  100 B 4  and  100 B 5  to each other in parallel. The fuse  170  may connect the first secondary battery unit  100 A and the second secondary battery unit  100 B to each other in series, which will later be described in more detail. 
         [0029]      FIG. 2  is a cross-sectional view of the secondary battery module, taken along the line of  FIG. 1 . 
         [0030]    Since the first to tenth secondary batteries  100 A 1 ,  100 A 2 ,  100 A 3 ,  100 A 4 ,  100 A 5 ,  100 B 1 ,  100 B 2 ,  100 B 3 ,  100 B 4  and  100 B 5  have substantially the same configuration, only the first secondary battery  100 A 1  will be representatively described in detail in the following description. In one embodiment, the first to fifth secondary batteries  100 A 1 ,  100 A 2 ,  100 A 3 ,  100 A 4  and  100 A 5  have first to fifth short-circuit members  151   c   1 ,  151   c   2 ,  151   c   3 ,  151   c   4  and  151   c   5  formed therein, respectively. However, short-circuit members corresponding to the sixth to tenth secondary batteries  100 B 1 ,  100 B 2 ,  100 B 3 ,  100 B 4  and  100 B 5  may not be formed, which will later be described in more detail. 
         [0031]    Referring to  FIG. 2 , the first secondary battery  100 A 1  according to an embodiment of the present invention may include an electrode assembly  110 , a first current collector  120 , a second current collector  130 , a case  140  and a cap assembly  150 . 
         [0032]    The electrode assembly  110  may be formed by winding or laminating a stack of a first electrode plate  111 , a separator  113  and a second electrode plate  112 , which are all thin plates or layers. In one embodiment, the first electrode plate  111  may function as a positive electrode, and the second electrode plate  112  may function as a negative electrode. 
         [0033]    The first electrode plate  111  may be formed by coating a first electrode active material, e.g., a transition metal oxide, on a first electrode made of a metal foil, e.g., aluminum foil. The first electrode plate  111  may include a first uncoated portion  111   a  that is not coated with the first electrode active material. The first uncoated portion  111   a  may correspond to a path of current flow between the first electrode plate  111  and the outside of the first electrode plate  111 . However, the present invention is not limited to the material of the first electrode plate  111  listed herein. 
         [0034]    The second electrode plate  112  may be formed by coating a second electrode active material, e.g., graphite or carbon, onto a second electrode made of a metal foil, e.g., nickel or copper. The second electrode plate  112  may include a second uncoated portion  112   a  that is not coated with the second active material. The second uncoated portion  112   a  may correspond to a path of current flow between the second electrode plate  112  and the outside of the second electrode plate  112 . However, the present invention is not limited to the material of the second electrode plate  112  listed herein. 
         [0035]    The separator  113 , located between the first and second electrode plates  111  and  112 , may prevent short circuits between the first and second electrode plates  111  and  112 , and may allow lithium ions to move. The separator  113  may be made of, e.g., polyethylene, polypropylene, or a composite film of polyethylene and polypropylene. However, the present invention is not limited to the material of the separator  113  listed herein. 
         [0036]    The first current collector  120  and the second current collector  130  may be coupled to opposite ends of the electrode assembly  110  to be electrically connected to the first and second electrode plates  111  and  112 , respectively. 
         [0037]    The first current collector  120  may be formed of a conductive material, such as aluminum or an aluminum alloy and may be electrically connected to the first electrode plate  111  by contacting the first electrode uncoated portion  111   a  protruding from one end of the electrode assembly  110 . The first current collector  120  may include a first coupling part  121  and a first extension part  123 . A first terminal hole  125  may be formed in the first coupling part  121 . The first terminal hole  125  may provide a space into which a lower portion of a first electrode terminal  152 A 1  is inserted and coupled. The first extension part  123  is bent and extended from an end of the first coupling part  121  and is generally shaped as a plate substantially contacting the first electrode uncoated portion  111   a . Assuming that a corner at which the first coupling part  121  and the first extension part  123  meet is denoted by ‘C’, the first coupling part  121  and the first extension part  123  may be substantially perpendicular to each other at the corner C. 
         [0038]    The second current collector  130  may be formed of a conductive material, such as copper, a copper alloy, nickel or a nickel alloy, and may be electrically connected to the second electrode plate  112  by contacting the second electrode uncoated portion  112   a  protruding from the other end of the electrode assembly  110 . The second current collector  130  may include a second coupling part  131  and a second extension part  133 . A second terminal hole  135  may be formed in the second coupling part  131 . The second terminal hole  135  may provide a space into which a second electrode terminal  155 A 1  is inserted and coupled. The second extension part  133  is bent and extended from an end of the second coupling part  131  and is generally shaped as a plate substantially contacting the second electrode uncoated portion  112   a . Assuming that a corner at which the second coupling part  131  and the second extension part  133  meet is denoted by ‘C’, the second coupling part  131  and the second extension part  133  may be substantially perpendicular to each other at the corner C. 
         [0039]    The case  140  may be formed of a conductive metal, such as aluminum, an aluminum alloy or a nickel plated steel, may have an approximately hexahedron shape, and may have a case opening through which the electrode assembly  110 , the first current collector  120  and the second current collector  130  are inserted and placed. Since the case  140  and the cap assembly  150  are illustrated in an assembled state in  FIGS. 1 and 2 , the case opening is not shown. However, it is to be understood that the case opening corresponds to a substantially opened portion of the edge of the cap assembly  150 . The inner surface of the case  140  may be insulated from the electrode assembly  110 , the first and second current collectors  120  and  130  and the cap assembly  150 . In one embodiment, the case  140  may be electrically connected to the first electrode terminal  152 A 1  and may function as a positive electrode, for example. 
         [0040]    The cap assembly  150  may be coupled to the case  140 . In one embodiment, the cap assembly  150  may be coupled to the case  140  at the opening of the case  140 . The cap assembly  150  may include a cap plate  151 , a first electrode terminal  152 A 1 , first nuts  153   a  and  153   b , a first gasket  154 , a second electrode terminal  155 A 1 , second nuts  156   a  and  156   b , a second gasket  157 , a safety vent  158  and an insulator  159 . 
         [0041]    The cap plate  151  may be coupled to the case  140  at the opening of the case  140  and may close the opening of the case  140 . A short circuit hole  151   a , terminal holes  151   b , a first short circuit member  151   c   1  and a safety vent  158  may be formed in the cap plate  151 . In one embodiment, the terminal holes  151   b  may be formed at both sides of the cap plate  151 , relative to the center of the cap plate  151 . In one embodiment, the cap plate  151  may be formed of the same material as that of the case  140  and may have the same polarity as that of the case  140 . 
         [0042]    In one embodiment, the first short circuit member  151   c   1  is installed in the short circuit hole  151   a  of the cap plate  151  and has the same polarity as that of the cap plate  151 . The first short circuit member  151   c   1  may include an inversion plate having a downwardly convex round part, and an edge part fixed to the first short circuit hole  151   a . In one embodiment, a peripheral part of the short circuit hole  151   a  is formed stepwise, and the edge part of the first short circuit member  151   c   1  is placed in the stepped peripheral part of the short circuit hole  151   a  to then be coupled to the cap plate  151  by, for example, welding. When the internal pressure of the first secondary battery  100 A 1  exceeds a preset pressure, the first short circuit member  151   c   1  may be inverted to then upwardly convexly protrude. The first short circuit member  151   c   1  may be formed in each of the first to fifth secondary batteries  100 A 1 ,  100 A 2 ,  100 A 3 ,  100 A 4  and  100 A 5 . In one embodiment, the first short circuit member  151   c   1  is preferably formed only in the first secondary battery  100 A 1  positioned in the first place among the plurality of secondary battery units. 
         [0043]    First nuts  153   a  and  153   b  include a first upper nut  153   a  and a first lower nut  153   b , which are fastened along the screw thread formed on the first electrode terminal  152 A 1 , thereby fixing the first electrode terminal  152 A 1  to the cap plate  151 . 
         [0044]    The first gasket  154  may be formed of an insulating material and may be located between the first electrode terminal  152 A 1  and the cap plate  151  to seal a space between the first electrode terminal  152 A 1  and the cap plate  151 . The first gasket  154  may prevent the introduction of moisture into the first secondary battery  100 A 1  or the leakage of the electrolyte from the first secondary battery  100 A 1 . 
         [0045]    The second electrode terminal  155 A 1  may pass through the terminal hole  151   b  formed at the side of the cap plate  151  opposite to the side of the cap plate  151  at which the first electrode terminal  152 A 1  is formed, and may be electrically connected to the second current collector  130 . The second electrode terminal  155 A 1  may be generally shaped as a pillar. A screw thread is formed at the outer circumferential edge of an upper pillar of the second electrode terminal  155 A 1  protruding from an upper portion of the cap plate  151 , and a flange  155   a  is formed at a lower pillar of the second electrode terminal  155 A 1  positioned at the lower portion of the cap plate  151  to prevent the second electrode terminal  155 A 1  from being dislodged from the cap plate  151 . In the second electrode terminal  155 A 1 , a portion of the lower pillar positioned at the lower portion of the cap plate  151  may be fitted into the terminal hole  135  of the second current collector  130 . The second electrode terminal  155 A 1  may be electrically insulated from the cap plate  151 . 
         [0046]    Second nuts  156   a  and  156   b  include a second upper nut  156   a  and a second lower nut  156   b , which are fastened along the screw thread formed on the second electrode terminal  155 A 1 , thereby fixing the second electrode terminal  155 A 1  to the cap plate  151 . 
         [0047]    The second gasket  157  may be formed of an insulating material and may be located between the second electrode terminal  155 A 1  and the cap plate  151  to seal a space between the second electrode terminal  155 A 1  and the cap plate  151 . The second gasket  157  may prevent the introduction of moisture into the first secondary battery  100 A 1  or the leakage of the electrolyte from the first secondary battery  100 A 1 . 
         [0048]    The safety vent  158  may be formed in a vent hole  158   c  of the cap plate  151  and may include a vent plate  158   a . The vent plate  158   a  may have a notch  158   b  configured to be opened when the internal pressure of the case  140  increases. In one embodiment, when the internal pressure of the case  140  exceeds a preset pressure, the vent plate  158   a  is ruptured along the notch  158   b , and the ruptured part of the vent plate  158   a  comes to face the top portion of the cap plate  151 . 
         [0049]    The insulator  159  may be installed between each of the first and second current collectors  120  and  130  and the cap plate  151  to prevent unnecessary short circuiting. 
         [0050]    In some embodiments, one side  160 A of the first connection member  160  faces the first to fifth short-circuit members  151   c   1 ,  151   c   2 ,  151   c   3 ,  151   c   4  and  151   c   5  of the first to fifth secondary batteries  100 A 1 ,  100 A 2 ,  100 A 3 ,  100 A 4  and  100 A 5 , and the other side  160 B of the first connection member  160  may be electrically connected to the second electrode terminal  155 B 5  of the tenth secondary battery  100 B 5  positioned in the last place in the second secondary battery unit  100 B. In one embodiment, first to fifth protrusions  161 ,  162 ,  163 ,  164  and  165  may be formed at the one side  160 A of the first connection member  160 , the first to fifth protrusions  161 ,  162 ,  163 ,  164  and  165  positioned on the first to fifth secondary batteries  100 A 1 ,  100 A 2 ,  100 A 3 ,  100 A 4  and  100 A 5 , facing the first to fifth short-circuit members  151   c   1 ,  151   c   2 ,  151   c   3 ,  151   c   4  and  151   c   5 , respectively, and protruding toward the first to fifth short-circuit members  151   c   1 ,  151   c   2 ,  151   c   3 ,  151   c   4  and  151   c   5 . A terminal hole  167  may be formed at the other side  160 B of the first connection member  160 . In one embodiment, a top portion of the second electrode terminal  155 B 5  of the tenth secondary battery  100 B 5  is inserted into the terminal hole  167 , and the second upper nut  156   a  is fastened with the terminal hole  167 , thereby electrically connecting the other side  160 B of the first connection member  160  to the second electrode terminal  155 B 5  of the tenth secondary battery  100 B 5 . 
         [0051]    The insulation film  180  may cover a top surface of each of the first to tenth secondary batteries  100 A 1 ,  100 A 2 ,  100 A 3 ,  100 A 4 ,  100 A 5 ,  100 B 9 ,  100 B 2 ,  100 B 3 ,  100 B 4  and  100 B 5 . For example, the insulation film  180  may cover the top surfaces of the first to tenth secondary batteries  100 A 1 ,  100 A 2 ,  100 A 3 ,  100 A 4 ,  100 A 5 ,  100 B 1 ,  100 B 2 ,  100 B 3 ,  100 B 4  and  100 B 5 , except for portions of the top surfaces where electrode terminals  152 A 1  to  152 A 5 ,  155 A 1  to  155 A 5 ,  152 B 1  to  151 B 5 , and  155 B 1  to  155 B 5  are respectively positioned. In some embodiments, the insulation film  180  may cover the first secondary battery  100 A 1  and a portion of the lateral surface of the tenth secondary battery  100 B 5  to be more firmly fixed to the top portion of the secondary battery module  100 . In addition, a plurality of opening holes  180 A facing the first to fifth short-circuit members  151   c   1 ,  151   c   2 ,  151   c   3 ,  151   c   4  and  151   c   5  may be formed in the insulation film  180 . A top portion of the first short-circuit member  151   c   1  may be aligned with the opening holes  180 A and may be opened by the opening holes  180 A. In one embodiment, the first connection member  160  is positioned on the insulation film  180 , thereby preventing unnecessary short circuiting between the first connection member  160  and the case  140 . The insulation film  180  is preferably formed with an appropriate thickness, enough to be able to tear when the safety vent  158  is ruptured, and is preferably made of a material having appropriate heat resistance to prevent the insulation film  180  from melting when the surface temperature of the battery rises. 
         [0052]    As illustrated in  FIG. 1 , the second connection members  171  and  173  may include a second-first connection member  171  and a second-second connection member  173 , and the third connection members  172  and  174  may include a third-first connection member  172  and a third-second connection member  174 . However, number of the second and third connection members  171 ,  172 ,  173  and  174  may vary according to the number of secondary battery units to be installed. 
         [0053]    The second-first connection member  171  may electrically connect the first electrode terminals  152 A 1 ,  152 A 2 ,  152 A 3 ,  152 A 4  and  152 A 5  of the first to fifth secondary batteries  100 A 1 ,  100 A 2 ,  100 A 3 ,  100 A 4  and  100 A 5  to each other. The third-first connection member  172  may electrically connect the second electrode terminals  155 A 1 ,  155 A 2 ,  155 A 3 ,  155 A 4  and  155 A 5  of the first to fifth secondary batteries  100 A 1 ,  100 A 2 ,  100 A 3 ,  100 A 4  and  100 A 5  to each other. Accordingly, the second-first and third-first connection members  171  and  172  may connect the first to fifth secondary batteries  100 A 1 ,  100 A 2 ,  100 A 3 ,  100 A 4  and  100 A 5  to each other in parallel. 
         [0054]    In some embodiments, the second-second connection member  173  may electrically connect the first electrode terminals  152 B 1 ,  152 B 2 ,  152 B 3 ,  152 B 4  and  152 B 5  of the sixth to tenth secondary batteries  100 B 1 ,  100 B 2 ,  100 B 3 ,  100 B 4  and  100 B 5  to each other. The third-second connection member  174  may electrically connect the second electrode terminals  155 B 1 ,  155 B 2 ,  155 B 3 ,  155 B 4  and  155 B 5  of the sixth to tenth secondary batteries  100 B 1 ,  100 B 2 ,  100 B 3 ,  100 B 4  and  100 B 5  to each other. Accordingly, the second-second and third-second connection members  173  and  174  may connect the sixth to tenth secondary batteries  100 B 1 ,  100 B 2 ,  100 B 3 ,  100 B 4  and  100 B 5  to each other in parallel. 
         [0055]    The fuse  170  may electrically connect the third-first connection member  172  of the first secondary battery unit  100 A to the second-second connection member  173  of the second secondary battery unit  100 B. The fuse  170  has a smaller sectional area than the third-first connection member  172  or the second-second connection member  173 , and may be made of a material having a lower melting point than the first to fifth short-circuit members  151   c   1 ,  151   c   2 ,  151   c   3 ,  151   c   4  and  151   c   5 . 
         [0056]      FIG. 3  is a circuit view illustrating the flow of current during a normal charge operation of the secondary battery module shown in  FIG. 1 . 
         [0057]    As illustrated in  FIG. 3 , a charge current of the secondary battery module  100  is applied to the second-first connection member  171  of the first secondary battery unit  100 A. Then, the charge current passes through the first electrode terminals  152 A 1 ,  152 A 2 ,  152 A 3 ,  152 A 4  and  152 A 5  of the first to fifth secondary batteries  100 A 1 ,  100 A 2 ,  100 A 3 ,  100 A 4  and  100 A 5 , the electrode assembly  110 , the second electrode terminals  155 A 1 ,  155 A 2 ,  155 A 3 ,  155 A 4  and  155 A 5 , and flows to the second secondary battery unit  100 B through the third-first connection member  172 . In one embodiment, the charge current output from the third-first connection member  172  of the first secondary battery unit  100 A may be applied to the second-second connection member  173  of the second secondary battery unit  100 B through the fuse  170 . The charge current applied to the second-second connection member  173  of the second secondary battery unit  100 B may pass through the first electrode terminals  152 B 1 ,  152 B 2 ,  152 B 3 ,  152 B 4 ,  152 B 5  of the sixth to tenth secondary batteries  100 B 1 ,  100 B 2 ,  100 B 3 ,  100 B 4  and  100 B 5 , the electrode assembly  110 , and the second electrode terminals  155 B 1 ,  155 B 2 ,  155 B 3 ,  155 B 4  and  155 B 5  and may then be output through the third-second connection member  174 . 
         [0058]      FIGS. 4 and 5  are circuit views illustrating operation mechanism during an overcharge of a secondary battery module  100  according to an embodiment of the present invention. 
         [0059]    In one embodiment, when the internal pressure inside the case  140  of each of the first to tenth secondary batteries  100 A 1  to  100 B 5  exceeds a preset pressure due to overcharge of the secondary battery module  100 , at least one of the first to fifth short-circuit members  151   c   1  to  151   c   5  of the first secondary battery unit  100 A may be inverted to upwardly protrude. When this occurs, at least one of the first to fifth protrusions  161 ,  162 ,  163 ,  164  and  165  may electrically contact the upwardly protruding short-circuit member. In the embodiment illustrated in  FIGS. 4 and 5 , it is assumed that when the secondary battery module  100  is overcharged, the third short-circuit member  151   c   3  of the third secondary battery  100 A 3  protrudes to contact the third protrusion  163  of the first connection member  160 . 
         [0060]    In the illustrated embodiment, the third short-circuit member  151   c   3  is electrically connected to the case  140 , which in turn is electrically connected to a positive electrode, and the first connection member  160  is connected to the second electrode terminal  155 B 5  of a negative electrode. Thus, when the third short-circuit member  151   c   3  and the third protrusion  163  on the first connection member  160  contact each other, the secondary battery module  100  may be short circuited. 
         [0061]    As illustrated in  FIG. 4 , an overcharge current of the secondary battery module  100  is applied to the second-first connection member  171  of the first secondary battery unit  100 A, passes through the first electrode terminal  152 A 3  of the third secondary battery  100 A 3 , the case  140 , the third short-circuit member  151   c   3 , the first connection member  160 , the second electrode terminal  155 B 5  of the tenth secondary battery  100 B 5 , the electrode assembly  110 , the first electrode terminal  152 B 5 , the second-second connection member  173 , the fuse  170  and the third-first connection member  172 , the second electrode terminal  155 A 3  of the third secondary battery  100 A 3 , the electrode assembly  110  and the first electrode terminal  152 A 3  of the third secondary battery  100 A 3 , and then flows to the outside through the second-first connection member  171 . In some embodiments, when the overcharge current flows across a circuit constituted by the secondary battery module  100 , the fuse  170  installed on the circuit may be melted by the heat generated due to the overcharge current and may cut off the current. Accordingly, as illustrated in  FIG. 5 , an electrical connection of the secondary battery module  100  may be blocked. 
         [0062]    In the secondary battery module according to the embodiment of the present invention, a plurality of secondary battery units each including a plurality of secondary batteries connected to each other in parallel are connected to each other in series. The secondary battery unit positioned in the first place among the plurality of secondary battery units includes a positive electrode short-circuit member and a connection member facing the short-circuit member. The connection member is electrically connected to a negative electrode terminal of the last secondary battery in the secondary battery unit positioned in the last place among the plurality of secondary battery units, and fuses are provided between each of the respective secondary battery units. During overcharge, the overcharge current is bypassed from the first secondary battery unit to the last secondary battery unit, thereby preventing the overcharge current from flowing through the secondary battery and minimizing damages of the secondary battery. 
         [0063]    In some embodiments, a safety operation against overcharge can be successfully performed by installing the fuse only at a connection part between each of the secondary battery units. In other words, it is not necessary to install the fuse for each secondary battery unit. In addition, during overcharge, even when the short-circuit member is installed only at the secondary battery unit arranged in the first place, an overcharge preventing operation can be successfully performed by making an overcharge current bypass through the first connection member. Accordingly, the number of components of the secondary battery module can be minimized, thereby reducing the manufacturing cost of the secondary battery module. In addition, since the number of components, such as the short-circuit member, the fuse, or the like, is reduced, a probability of malfunction of an overcharge preventing safety device due to malfunctioning of each of the individual components can be reduced. 
         [0064]    Although the secondary battery module according to an exemplary embodiment of the present invention has been described in detail hereinabove, it should be understood that many variations and modifications of the basic inventive concept herein described, which may appear to those skilled in the art, will still fall within the spirit and scope of the exemplary embodiments of the present invention as defined by the appended claims and equivalents thereof.