Abstract:
A battery includes a battery case, an electrode assembly in the battery case, the electrode assembly including a first electrode, a first terminal exposed to an exterior of the battery case, the first terminal being electrically connected to the first electrode, a first fixing member mechanically coupling the first terminal to the battery, the first fixing member forming at least part of an electrical path from the first terminal to the first electrode, and a corrosion resistance member providing an electrical path from the first terminal to the first fixing member and being in direct contact with each of the first terminal and the first fixing member.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to pending U.S. Provisional Application No. 61/272,511, filed in the U.S. Patent and Trademark Office on Oct. 1, 2009, and entitled “RECHARGEABLE BATTERY AND BATTERY MODULE,” which is incorporated by reference herein in its entirety and for all purposes. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    Embodiments relate to a rechargeable battery and a battery module. 
         [0004]    2. Description of the Related Art 
         [0005]    A rechargeable battery differs from a primary battery in that it can be repeatedly charged and discharged, while the latter makes only the irreversible conversion of chemical to electrical energy. The low-capacity rechargeable battery is used as the power supply for small electronic devices, such as cellular phones, notebook computers and camcorders, while the high-capacity rechargeable battery is used as the power supply for driving motors in hybrid vehicles and the like. 
         [0006]    A high-power rechargeable battery using a non-aqueous electrolyte with a high energy density has been recently developed. For example, the high-power rechargeable battery is constructed with a high-capacity rechargeable battery having a plurality of rechargeable cells coupled to each other in series such that it can be used as the power supply for driving motors in electric vehicles requiring high power. 
         [0007]    The above information disclosed in this Background section is only for enhancement of understanding of the related art and may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
       SUMMARY 
       [0008]    Embodiments are therefore directed to a rechargeable battery and a battery module, which substantially overcome one or more of the problems due to the limitations and disadvantages of the related art. 
         [0009]    It is therefore a feature of an embodiment to provide a rechargeable battery with an improved terminal structure, and a battery module including the same. 
         [0010]    It is therefore another feature of an embodiment to provide a rechargeable battery that includes provisions for preventing galvanic corrosion, and a battery module including the same. 
         [0011]    At least one of the above and other features may be realized by providing a battery, including a battery case, an electrode assembly in the battery case, the electrode assembly including a first electrode, a first terminal exposed to an exterior of the battery case, the first terminal being electrically connected to the first electrode, a first fixing member mechanically coupling the first terminal to the battery, the first fixing member forming at least part of an electrical path from the first terminal to the first electrode, and a corrosion resistance member providing an electrical path from the first terminal to the first fixing member and being in direct contact with each of the first terminal and the first fixing member. 
         [0012]    The corrosion resistance member may prevent the first terminal from directly contacting the first fixing member. 
         [0013]    The first terminal may have a surface formed of a metal having a first ionization tendency, the first fixing member may have a surface formed of a metal having a second ionization tendency, and the corrosion resistance member may have a surface formed of a metal having a third ionization tendency that is between the first ionization tendency and the second ionization tendency. 
         [0014]    The first terminal may serve as the positive terminal. 
         [0015]    The first terminal may serve as the cathode terminal during discharge of the battery. 
         [0016]    The metal forming the surface of the first terminal may be copper, and the metal forming the surface of the first fixing member may be aluminum. 
         [0017]    The first electrode may include aluminum, and the first fixing member may electrically contact the first electrode. 
         [0018]    The metal forming the surface of the corrosion resistance member may be nickel, stainless steel, nickel-plated copper, or a clad metal of Al—Cu, Ni—Cu, or Al—Ni. 
         [0019]    The first terminal may serve as the negative terminal. 
         [0020]    The first terminal may serve as the anode terminal during discharge of the battery. 
         [0021]    The metal forming the surface of the first terminal may be aluminum, and the metal forming the surface of the first fixing member may be copper. 
         [0022]    The first electrode may include copper, and the first fixing member may electrically contact the first electrode. 
         [0023]    The metal forming the surface of the corrosion resistance member may be nickel, stainless steel, nickel-plated copper, or a clad metal of Al—Cu, Ni—Cu, or Al—Ni. 
         [0024]    The corrosion resistance member may be separate from the first terminal and the first fixing member. 
         [0025]    The corrosion resistance member may be integral with the first terminal. 
         [0026]    The corrosion resistance member may be a layer deposited on the first terminal. 
         [0027]    The corrosion resistance member may be a plating layer on the first terminal. 
         [0028]    The electrode assembly may further include a second electrode and a separator, the separator separating the first electrode from the second electrode. 
         [0029]    The first fixing member may be a rivet. 
         [0030]    At least one of the above and other features may also be realized by providing a battery module, including a first battery, and a second battery electrically connected to the first battery, each of the first and second batteries including a battery case, an electrode assembly in the battery case, the electrode assembly including a first electrode, a first terminal exposed to an exterior of the battery case, the first terminal being electrically connected to the first electrode, a first fixing member mechanically coupling the first terminal to the battery, the first fixing member forming at least part of an electrical path from the first terminal to the first electrode, and a corrosion resistance member providing an electrical path from the first terminal to the first fixing member and being in direct contact with each of the first terminal and the first fixing member. 
         [0031]    The corrosion resistance member may prevent the first terminal from directly contacting the first fixing member. 
         [0032]    The first battery and the second battery may be electrically connected to one another in series, the first terminals of the respective first and second batteries serving as positive terminals, and the positive terminal of the first battery may be electrically connected to a negative terminal of the second battery by a connection member that is welded to each of the positive terminal of the first battery and the negative terminal of the second battery. 
         [0033]    Outer surfaces of the positive terminal of the first battery, the negative terminal of the second battery, and the connection member may each be formed of a same metal. 
         [0034]    The first fixing member may be a rivet, the rivet having an outer surface formed of a metal different from an outer surface of the positive terminal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]    The above and other features and advantages will become more apparent to those of ordinary skill in the art by describing in detail example embodiments with reference to the attached drawings, in which: 
           [0036]      FIG. 1  illustrates a perspective view of a rechargeable battery according to a first example embodiment, 
           [0037]      FIG. 2  illustrates a cross-sectional view of the rechargeable battery taken along the II-II line of  FIG. 1 , 
           [0038]      FIG. 3  illustrates an exploded perspective view of the rechargeable battery according to the first example embodiment, illustrating the process of installing a fixture at a first terminal, 
           [0039]      FIG. 4  illustrates an exploded perspective view of a battery module according to a second example embodiment, 
           [0040]      FIG. 5  illustrates a cross-sectional view of the battery module taken along the V-V line of  FIG. 4 , and 
           [0041]      FIG. 6  illustrates a partial sectional view of a battery module according to a third example embodiment. 
       
    
    
     DESCRIPTION OF REFERENCE NUMERALS INDICATING ELEMENTS IN THE DRAWINGS 
       [0000]    
       
         
           
               100 : rechargeable battery, 
               110 : electrode assembly, 
               111 : positive electrode, 
               111   a : positive electrode uncoated region, 
               112 : negative electrode, 
               112   a : negative electrode uncoated region, 
               113 : separator, 
               115 : first lead member, 
               115   a : first lead member upper plate, 
               115   b : first lead member attachment plate, 
               116 : second lead member, 
               120 : cap plate, 
               121 : first fixture (rivet), 
               121   a : first fixture pillar portion, 
               121   b : first fixture top head portion, 
               121   c : first fixture bottom head portion, 
               122 : second fixture (rivet), 
               122   a : second fixture pillar portion, 
               122   b : second fixture top head portion, 
               122   c : second fixture bottom head portion, 
               123 : terminal insulating member, 
               124 : case, 
               125 : electrolyte injection hole plug (cork), 
               126 : vent, 
               127 : lower gasket, 
               130 : first terminal (positive terminal), 
               140 : second terminal (negative terminal), 
               131 : protrusion, 
               132 : first hole, 
               134 : second hole, 
               141 : protrusion, 
               150 : corrosion resistance member, 
               151 : corrosion resistance member tube portion, 
               153 : corrosion resistance member head portion, 
               156 : corrosion resistance member hole, 
               160 : connection member, 
               162 : connection member groove, 
               165 : welded portion, 
               175 : welded portion, 
               180 : first terminal (positive terminal), 
               181 : first terminal protrusions, and 
               185 : corrosion resistance layer. 
           
         
       
     
       DETAILED DESCRIPTION 
       [0084]    Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings, however, they may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
         [0085]    In the drawing figures, dimensions may be exaggerated for clarity of illustration. It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element, or one or more intervening elements may also be present. It will also be understood that when an element is referred to as being “under” another element, it can be directly under, or one or more intervening elements may also be present. It will also be understood that when an element is referred to as being “between” two elements, it can be the only element between the two elements, or one or more intervening elements may also be present. Like reference numerals refer to like elements throughout. 
         [0086]    As used herein, the term “anode” refers to the electrode at which oxidation occurs. As used herein, the term “cathode” refers to the electrode at which reduction occurs. The terminal that is coupled to the anode (“anode terminal”) is the negative terminal (−) of the electrochemical cell (or unit battery) while the electrochemical cell is discharging. The anode terminal provides electrons to the load circuit during discharge of the electrochemical cell. The terminal that is coupled to the cathode is the positive terminal (+) of the electrochemical cell while the electrochemical cell is discharging. The cathode terminal receives electrons from the load circuit during discharge of the electrochemical cell. While the battery is being charged, energy is input to the battery to regenerate the electrochemical potential of the battery. Thus, the oxidation and reduction locations interchange (or swap), such that the positive terminal of the electrochemical cell is the anode while the battery is being charged and the negative terminal of the electrochemical cell is the cathode while the battery is being charged. 
         [0087]      FIG. 1  illustrates a perspective view of a rechargeable battery according to a first example embodiment, and  FIG. 2  illustrates a cross-sectional view of the rechargeable battery taken along the II-II line of  FIG. 1 . 
         [0088]    Referring to  FIG. 1  and  FIG. 2 , the rechargeable battery  100  may be a prismatic battery. The rechargeable battery  100  may include an electrode assembly  110 . The electrode assembly  110  may include positive and negative electrodes  111  and  112  wound together with a separator  113  interposed therebetween as an insulator. The rechargeable battery  100  may also include a case  124  having the electrode assembly  110  therein, first and second terminals  130  and  140  electrically connected to the electrode assembly  110 , and a cap plate  120  fitted to an opening  124   a  of the case  124 . As described in greater detail below, terminals may be electrically connected to the electrode assembly  110  and protruded to the outside of the case  124 . 
         [0089]    The positive electrode  111  may include a current collector, e.g., a thin metal foil plate, and a positive active material. The positive electrode  111  may include a coated region, where the positive active material is coated, and an uncoated region  111   a , where active material is not coated. The thin metal foil plate of the positive electrode  111  may be aluminum or may include aluminum. The negative electrode  112  may include a current collector, e.g., a thin metal foil plate, and a negative active material. The negative electrode  112  may include a coated region, where the negative active material is coated, and an uncoated region  112   a , where active material is not coated. The uncoated regions  111   a  and  112   a  may be formed at the lateral ends of the positive and the negative electrodes  111  and  112  in the longitudinal direction of the positive and the negative electrodes  111  and  112 . The positive and the negative electrodes  111  and  112  may be spiral-wound by interposing the separator  113  therebetween as an insulator so as to form a jellyroll-shaped electrode assembly  110 . 
         [0090]    In another implementation, the electrode assembly  110  may be structured such that a plurality of positive and negative electrodes  111  and  112  are alternately deposited while interposing the separator  113  therebetween. 
         [0091]    A first terminal  130  may be electrically connected to the positive uncoated region  111   a  of the electrode assembly  110  via a first lead member  115 , and a second terminal  140  may be electrically connected to the negative uncoated region  112   a  via a second lead member  116 . 
         [0092]    The first terminal  130  may function as a positive terminal, and the second terminal  140  may function as a negative terminal. In another implementation, the first terminal  130  may become a negative terminal, while the second terminal  140  becomes a positive terminal. 
         [0093]    The case  124  may be formed to have a hexahedral-shaped prismatic case having an inner space and the top opening  124   a . In another implementation, the case may be formed with various shapes such as a cylinder, a pouch, etc. 
         [0094]    The cap plate  120  may be formed with a thin plate, and may be provided with a vent  126  having a notch capable of opening at a predetermined inner pressure. A plug  125  may be provided for sealing an electrolyte injection hole. 
         [0095]    The first and the second terminals  130  and  140  may be plate-shaped, and may be disposed parallel to the cap plate  120 . The first terminal  130  may be fixed to the cap plate  120  by way of a first fixture  121 , and the second terminal  140  may be fixed to the cap plate  120  by way of a second fixture  122 . In an implementation, the fixtures  121  and  122  may be formed with rivets. By using the fixtures  121  and  122 , the first and second terminals  130 ,  140  may be secured against vibration and loosening, which may increase contact resistance. In contrast, where terminals are fixed to a cap plate by way of nuts, the nuts may be liable to release due to continuous external vibration or impact. If the nuts are released, the contact resistance between the electrode assembly and the terminals may increase so that the output of the rechargeable battery is deteriorated, and the cycle life of a battery module is reduced. 
         [0096]    The fixtures  121  and  122  may have pillar portions  121   a  and  122   a  inserted into the cap plate  120 , top head portions  121   b  and  122   b  laterally protruding from the top ends of the pillar portions  121   a  and  122   a , and bottom head portions  121   c  and  122   c  laterally protruding from the bottom ends of the pillar portions  121   a  and  122   a.    
         [0097]    A first lead member  115  may be attached, e.g., by welding, to the bottom side of the bottom head portion  121   c  positioned at the bottom end of the first fixture  121 . The first lead member  115  may be, or may include, aluminum. Similarly, the first fixture  121  may be, or may include, aluminum. The first lead member  115  may have an upper plate  115   a  welded to the first fixture  121 , and an attachment plate  115   b  protruding downward from the upper plate  115   a  and fixed to the positive uncoated region  111   a.    
         [0098]    A second lead member  116  may be attached, e.g., by welding, to the bottom side of the bottom head portion  122   c  positioned at the bottom end of the second fixture  122 . The second lead member  116  may be, or may include, copper. Similarly, the second fixture  122  may be, or may include, copper. The second lead member  116  may include an upper plate  116   a  welded to the second fixture  122 , and an attachment plate  116   b  protruding downward from the upper plate  116   a  and fixed to the negative uncoated region  112   a.    
         [0099]    In another implementation, the lead members  115  and  116  may be fixed to the cap plate  120 , together with the terminals  130  and  140 , by way of the fixtures  121  and  122 , rather than being welded to the fixtures. 
         [0100]    Respective terminal insulating members  123  may be installed between the cap plate  120  and the terminals  130  and  140  so as to insulate the cap plate  120  from the terminals  130 ,  140 . Respective lower gaskets  127  may be disposed between the cap plate  120  and the fixtures  121  and  122  so as to insulate the cap plate  120  from the fixtures  121  and  122 . 
         [0101]    The terminal insulating member  123  may be wider than the terminals  130  and  140 , and may be tightly adhered to the top surface of the cap plate  120 . The terminal insulating members  123  may have central through-holes for receiving the fixtures  121  and  122 . 
         [0102]    The terminals  130  and  140  of the rechargeable battery  100  according to the present example embodiment may be fixed to the cap plate  120  by way of the rivet-shaped fixtures  121  and  122 , which may endure under vibration better than a nut-coupled structure. 
         [0103]      FIG. 3  illustrates an exploded perspective view of the rechargeable battery according to the first example embodiment, illustrating the process of installing a fixture at a first terminal. 
         [0104]    An example of installation of the first fixture  121  (and the second fixture  122 , which may be installed in substantially the same manner) will now be described with reference to  FIG. 2  and  FIG. 3 . As shown in  FIG. 3 , the pillar-shaped fixture  121  ( 122 ) may be inserted into the terminal  130  ( 140 ) and the cap plate  120 . In this state, the fixture  121  ( 122 ) may be pressed from the top and the bottom ends so that top head portion  121   b  ( 122   b ) and bottom head portion  121   c  ( 122   c ) are formed by deforming the pillar shaped fixture  121  ( 122 ). In another implementation, a fixture with a pre-formed bottom head portion may be inserted into a terminal and cap plate, and the top end of the fixture may be pressed from the top end so as to form a top head portion at the top end of the rivet. 
         [0105]    The terminals  130  and  140  may be tightly adhered to the cap plate  120  during the process of pressing the fixtures  121  and  122  so that the terminals  130  and  140  can be prevented from being released due to vibration. 
         [0106]    It is most important with the rechargeable battery  100  to reduce the contact resistance. Excessively high contact resistance may degrade the output of the rechargeable battery  100 , and may generate resistance heating from high current flow so that the temperature of the rechargeable battery  100  is elevated. When the temperature of the rechargeable battery  100  is elevated, an abnormal reaction may occur internally, and, accordingly, the cycle life of the rechargeable battery  100  may be reduced. However, with the present example embodiment, the fixtures  121  and  122  may be less susceptible to being loosened by vibration, and, hence, the contact resistance may be minimized. 
         [0107]    As shown in  FIG. 1 , the first and the second terminals  130  and  140  may be generally formed in the shape of a rectangular plate, which has a short side with a relatively small length, and a long side with a length greater than the short sides. 
         [0108]    Upward protrusions  131  and  141  may be formed at both ends of the long side, respectively, and a connection member  160  (described in detail below) may be fitted between the protrusions  131  and  141 . 
         [0109]    The first and the second terminals  130  and  140  may be formed with the same material. The first and second terminals  130 ,  140  may be, or may include, copper. The rechargeable battery  100  may be a lithium battery, a lithium ion battery, etc. In an embodiment, the positive current collector, the first lead member  115 , and the first fixture  121  may be, or may include, aluminum. The negative current collector, the second lead member  116  and the second fixture  122  may be, or may include, copper. 
         [0110]    As described in detail below, the rechargeable battery  100  according to an embodiment may reduce or eliminate galvanic corrosion. In this regard, where the first and the second terminals  130  and  140  are formed with copper, galvanic corrosion may be generated between the copper first terminal  130  and the first fixture  121 , which may be, or may include, aluminum. Meanwhile, if the first and the second terminals  130  and  140  are formed with aluminum, galvanic corrosion may be made between the second terminal  140  and the second fixture  122 , which may be, or may include, copper. Moreover, the galvanic corrosion between dissimilar metals may be further worsened when the potential difference is large, and the copper metal having a low ionization tendency is used as the negative electrode  112 , while the aluminum metal having a high ionization tendency is used as the positive electrode  111 . As copper and aluminum are largely differentiated in ionization tendency from each other, the possibility of galvanic corrosion is increased at the aluminum metal. 
         [0111]    If galvanic corrosion is made between the terminals  130  and  140  and the fixtures  121  and  122 , the contact resistance between the terminals  130  and  140  and the fixtures  121  and  122  may increase. Accordingly, the output of the rechargeable battery  100  may be deteriorated. 
         [0112]    In accordance with the present example embodiment, the case where the first and the second terminals  130  and  140  are formed with copper will now be described with reference to  FIG. 2  and  FIG. 3 . 
         [0113]    A corrosion resistance member  150  may be installed between the first terminal  130  and the first fixture  121  in order to prevent galvanic corrosion. In an implementation, the corrosion resistance member  150  may be omitted from the second terminal  140 , as the materials connected at the second terminal  140  may all be the same, e.g., copper or including copper. The corrosion resistance member  150  may have a tube portion  151 , and a head portion  153  formed at the top end of the tube portion  151  and having a cross section larger than the tube portion  151 . The first terminal  130  may have a first hole  132  at a central region for receiving the tube portion  151 , and a second hole  134  communicating with the first hole  132  with a diameter greater than the first hole  132  to receive the head portion  153 . 
         [0114]    The corrosion resistance member  150  may have a hole  156 , for receiving the first fixture  121 , that is formed along the whole of the tube portion  151  and the head portion  153 . 
         [0115]    The pillar-shaped first fixture  121  may be inserted into the hole  156  and the cap plate  120 , and pressed so as to form the top head  121   b  and the bottom head  121   c.    
         [0116]    The corrosion resistance member  150  may be formed of a material having an ionization tendency that is between that of the material for the first terminal  130  and that of the material for the first fixture  121 . With a difference in ionization tendency between the first terminal  130  and the corrosion resistance member  150 , as well as between the first fixture  121  and the corrosion resistance member  150 , each being smaller than the difference in ionization tendency between the corrosion resistance member  150  and the first terminal  130 , the galvanic corrosion occurring at the first terminal  130  and the corrosion resistance member  150  may be reduced. 
         [0117]    In an implementation, taking as an example a case where the first terminal  130  is formed with copper and the first fixture  121  is formed with aluminum, the corrosion resistance member  150  may be formed with, e.g., nickel, stainless steel, nickel-plated copper, or a clad metal of Al—Cu, Ni—Cu, or Al—Ni, etc., having ionization tendencies between the copper and the aluminum metals. As particular examples, nickel and stainless steel are higher in ionization tendency than copper but lower than aluminum, and have excellent corrosion resistance. 
         [0118]    As described above, with the present example embodiment, even in case the first terminal  130  and the first fixture  121  are formed with different materials, the galvanic corrosion occurring between the first terminal  130  and the first fixture  121  can be reduced. Furthermore, by forming the first terminal  130  and the first fixture  121  with different materials, it is possible to form the first terminal  130  and the second terminal  140  with the same material. This may substantially simplify the electrical connection of multiple batteries in a battery module. 
         [0119]      FIG. 3  illustrates an enlarged view of the first terminal  130 . It will be appreciated that the second terminal  140  can be formed using the same structures for preventing galvanic corrosion, if necessary or desired as a result of the materials used for the second terminal  140  and corresponding fixing member and electrode. Accordingly, a detailed description of such galvanic corrosion preventing structures will not be repeated for the second terminal  140 . 
         [0120]      FIG. 4  illustrates an exploded perspective view of a battery module according to a second example embodiment, and  FIG. 5  illustrates a cross-sectional view of the battery module taken along the V-V line of  FIG. 4 . 
         [0121]    Referring to  FIG. 5 , the battery module  200  according to the present example embodiment may include a plurality of rechargeable batteries  100 . Respective connection members  160  may be used to electrically interconnect the rechargeable batteries  100 . The rechargeable batteries  100  may be arranged in parallel as a stack of batteries. The rechargeable batteries  100  may be electrically coupled to each other in series by way of the connection members  160 . In another implementation, the rechargeable batteries  100  may be electrically coupled to each other in parallel. 
         [0122]    A high-capacity rechargeable battery module may be formed using a plurality of rechargeable batteries  100  electrically coupled to each other in series and/or parallel. The rechargeable batteries  100  may have a cylindrical shape, a prismatic shape, etc. 
         [0123]    In the battery module, the connection members  160  may be attached to the positive and the negative terminals by way of resistance welding. Preferably, the positive and negative terminals are formed of a same material. For example, terminals  130  and  140  may each be, or may each include, copper. This may allow for a simple resistance welding process to be used, as it may be hard otherwise to weld dissimilar metals to each other where the positive and the negative terminals are formed with different materials. In this regard, if the connection member is formed with a material different from the positive and/or negative terminals, the melting points of the connection member and the positive and/or negative terminals may be different from each other so that it becomes hard to attach the connection member and the terminals to each other through welding. Further, if dissimilar metals contact each other, galvanic corrosion is more likely to occur between the dissimilar metals, and accordingly, the contact resistance between the dissimilar metals may increase. 
         [0124]    In the battery module  200  according to the present example embodiment, the first and the second terminals  130  and  140  of the adjacent rechargeable batteries  100  may be disposed next to one another. Thus, the connection member  160  may be welded to the first terminal  130  of one rechargeable battery  100  and the second terminal  140  of the other rechargeable battery  100 . 
         [0125]    The connection member  160  may be generally plate-shaped. In an implementation, grooves  162  are formed at both ends of the connection member  160  in order to pass the top head portions  121   b  and  122   b  of the fixtures  121  and  122 . The connection member  160  may be fitted between the protrusions  131  and  141  of the terminals  130  and  140 . The protrusions  131  and  141  of the respective terminals  130 ,  140  and the connection member  160  may be welded to each other such that welded portions  165  are formed at the contact regions between the connection member  160  and the terminals  130  and  140 . The connection member  160  may be formed with the same material as the terminals  130  and  140 . For example, the connection member  160 , the first terminal  130  of one battery and the second terminal  140  of the adjacent battery may each be, or may each include, copper. In an implementation, the terminals  130  and  140  may be copper, and the connection member  160  may also be copper. In another implementation, the terminals  130  and  140  may be aluminum, and the connection member  160  may also be aluminum. 
         [0126]    In the present example embodiment, in case that the terminals  130  and  140  and the connection member  160  are formed with the same material, the connection member  160  may be easily attached to those terminals by way of laser welding or resistance welding. Furthermore, when the connection member  160  is formed with copper, having a high electrical conductivity and a low resistivity, the resistance may be reduced so that the total output of the battery module  200  is enhanced. When the connection member  160  and the terminals  130  and  140  are attached to each other by way of welding, the contact resistance between the terminals  130  and  140  and the connection member  160  may be prevented from increasing from impact or external vibration. 
         [0127]      FIG. 6  illustrates a partial sectional view of a battery module according to a third example embodiment. 
         [0128]    The battery module  400  according to the present example embodiment may include a plurality of rechargeable batteries  300 , and respective connection members  170  electrically interconnecting the rechargeable batteries  300 . 
         [0129]    The battery module  400  according to the present example embodiment may have the same structure as the battery module  200  according to the first example embodiment except for the structure of a first terminal  180  and the connection member  170 . Descriptions of same elements as the battery module  200  will not be repeated. 
         [0130]    The first terminal  180  may be electrically connected to an electrode assembly  110  by way of the first fixture  121 , e.g., a rivet, and fixed to the cap plate  120 . The first fixture  121  may be electrically connected to the electrode assembly  110  via a first lead member  115 . 
         [0131]    As with the first example embodiment, the first terminal  180  of one rechargeable battery  300  and an adjacent second terminal  140  of the rechargeable battery  300  neighboring thereto may be electrically connected to each other by way of the connection member  170 . The first terminal  180  and the second terminal  140  may be formed with the same material. For example, the first and second terminals  180 ,  140  may each be, or may each include, copper. The connection member  170  may be formed of the same material as the first and second terminals  180 ,  140 . The connection member  170  may be fitted between protrusions  181  of the first terminal  180  and protrusions  141  of the terminals  180  and  140 , and welded to the protrusions  181  and  141  of the second terminal and  140 . Welded portions  175  may be formed at the contact regions between the terminals  180  and  140  and the connection member  170 . A groove  172 , e.g., a recess, may be formed at the bottom side of the connection member  170  in order to receive the top head  121   b  of the first fixture  121 . The top surface of the groove  172  may cover the top head  121   b.    
         [0132]    The first terminal  180  may be plate-shaped, and protrusions  181  may be formed at both lateral ends of the first terminal  180 . A corrosion resistance layer  185  may be formed, e.g., by a deposition process such as plating, at the contact area between the first terminal  180  and the first fixture  121 . The deposition process may be, e.g., vapor deposition, sputtering, electroplating, electroless plating, etc. The corrosion resistance layer  185  may be formed with a material having an ionization tendency between that of the material for the first terminal  180  and the material for the first fixture  121 . 
         [0133]    With a difference in ionization tendency between the corrosion resistance layer  185  and the first terminal  180 , and the difference in ionization tendency between the corrosion resistance layer  185  and the first fixture  121 , each being smaller than the difference in ionization tendency between the first terminal  180  and the first fixture  121 , the galvanic corrosion made at the first terminal  180  and the corrosion resistance plating layer  185  may be reduced. 
         [0134]    In an implementation, the corrosion resistance layer  185  may be formed on the first terminal  180  by way of plating. Thus, a gap may be avoided between the first terminal  180  and the corrosion resistance layer  185 , and, hence, galvanic corrosion made at the first terminal  180  may be further reduced. In an implementation, the corrosion resistance layer  185  may not be formed at the contact area between the connection member  170  and the first terminal  180 . Accordingly, the connection member  170  and the first terminal  180  may contact each other directly, such that the resistance between the connection member  170  and the first terminal  180  may not be increased due to the corrosion resistance layer  185 . 
         [0135]    In a specific example according to the present embodiment, the first terminal  180  is formed with copper, the first fixture  121  is formed with aluminum, and the corrosion resistance layer  185  is formed with nickel, nickel having an ionization tendency between copper and aluminum. As nickel is greater in ionization tendency than copper but smaller than aluminum and has excellent corrosion resistance, it may reduce the occurrences of corrosion in a stable manner. 
         [0136]    Example embodiments have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. For example, features have been described herein as being formed of a particular material relative to a material of an adjacent contacting feature. However, such particular materials may be a surface coating. For example, a connection member may have a coating of copper or a copper-containing alloy, rather than being formed of copper of the copper-containing alloy. Accordingly, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.