Abstract:
A secondary battery may include a fuse formed in an electrode terminal. In exemplary embodiments, the secondary battery may include an electrode assembly including a first electrode plate, a second electrode plate and a separator, a current collector plate electrically connected to the electrode assembly, a case accommodating the electrode assembly, the current collector plate and an electrolyte, and an electrode terminal electrically connected to the current collector plate and protruded to an outside of the case, wherein the electrode terminal portion includes a protrusion part electrically connected to the current collector plate in a normal condition and selectively electrically disconnectable therefrom.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    Korean Patent Application No. 10-2015-0171543, filed on Dec. 3, 2015, in the Korean Intellectual Property Office, and entitled: “Secondary Battery,” is incorporated by reference herein in its entirety. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    Exemplary embodiments relate to a secondary battery. 
         [0004]    2. Description of the Related Art 
         [0005]    In general, secondary batteries are repeatedly charged and discharged, unlike primary batteries which are not. A low capacity battery including a battery cell in the form of a pack may be used for small portable electronic devices, e.g., cellular phones and camcorders, and a high capacity battery including dozens of battery cells connected to one another may be used as a motor-driving power source for electric scooters, hybrid vehicles, or electric vehicles. 
         [0006]    Secondary batteries may be manufactured in various shapes, including prismatic, cylindrical and pouch shapes. Each of the unit batteries typically includes an electrode assembly having a positive electrode, a negative electrode, and a separator between the positive and negative electrodes. 
       SUMMARY 
       [0007]    Exemplary embodiments are directed to a secondary battery may include an electrode assembly including a first electrode plate, a second electrode plate and a separator, a current collector plate electrically connected to the electrode assembly, a case accommodating the electrode assembly, the current collector plate and an electrolyte, and an electrode terminal portion electrically connected to the current collector plate and protruded to an outside of the case, wherein the electrode terminal portion includes a protrusion part electrically connected to the current collector plate in a normal condition and selectively electrically disconnectable therefrom. 
         [0008]    The electrode terminal portion may further include an insulation member, and the protrusion part may pass through the insulation member to be electrically connected to the current collector plate. 
         [0009]    The electrode terminal portion may include a flange horizontally extending from a side portion of the electrode terminal portion and the insulation member may be installed between the flange and the current collector plate. 
         [0010]    An electrode tab may be electrically connected to one end of the current collector plate and the protrusion part of the electrode terminal portion may be electrically connected to another end of the current collector plate. 
         [0011]    The protrusion part may include a plurality of protrusions. 
         [0012]    The protrusions may be spaced equidistant from an electrode tab. 
         [0013]    The protrusions may be sequentially formed in a lengthwise direction of the current collector plate, such that one protrusion is closer to an electrode tab than another protrusion. 
         [0014]    The electrode terminal portion may include a first electrode terminal and a second electrode terminal, and the protrusion part may be on the first electrode terminal. 
         [0015]    The second electrode terminal may be electrically connected to a second current collector plate. 
         [0016]    The protrusions of the first electrode terminal may have a narrower current path between the first electrode terminal and the current collector plate than a current path between the second electrode terminal and the second current collector plate. 
         [0017]    The electrode terminal portion may further include a body part and a flange extending from a bottom side of the body part, the protrusion part may be under the body part and the flange. 
         [0018]    A diameter of the protrusion part may be less than a diameter of the body part. 
         [0019]    An electrical connection between the current collector plate and the electrode terminal portion may be broken, when an over-current flows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    Features will become apparent to those of ordinary skill in the art by describing in detail exemplary embodiments with reference to the attached drawings in which: 
           [0021]      FIG. 1  illustrates a perspective view of a secondary battery according to an exemplary embodiment; 
           [0022]      FIG. 2  illustrates a cross-sectional view illustrating an internal structure of a case in the secondary battery shown in  FIG. 1 ; 
           [0023]      FIG. 3  illustrates a perspective view of a first electrode terminal portion of the secondary battery shown in  FIG. 1 ; 
           [0024]      FIG. 4  illustrates a bottom view of the first electrode terminal portion shown in  FIG. 3 ; 
           [0025]      FIG. 5  illustrates a cross-sectional view of the first electrode terminal portion shown in  FIG. 3 ; 
           [0026]      FIG. 6  illustrates bottom view of a first electrode terminal portion of a secondary battery according to another exemplary embodiment; 
           [0027]      FIG. 7  illustrates a cross-sectional view of the first electrode terminal portion shown in  FIG. 6 ; 
           [0028]      FIG. 8  illustrates a bottom view of a first electrode terminal portion of a secondary battery according to still another exemplary embodiment; and 
           [0029]      FIG. 9  illustrates a cross-sectional view of the first electrode terminal portion shown in  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    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 exemplary implementations to those skilled in the art. 
         [0031]    In the drawing figures, the dimensions of layers and regions may be exaggerated for clarity of illustration. It will also be understood that when a layer or element is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. Further, it will be understood that when a layer is referred to as being “under” another layer, it can be directly under, and one or more intervening layers may also be present. In addition, it will also be understood that when a layer is referred to as being “between” two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present. Like reference numerals refer to like elements throughout. 
         [0032]    As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. In addition, it will be understood that when an element A is referred to as being “connected to” an element B, the element A can be directly connected to the element B, or an intervening element C may be present between the elements A and B so that the element A can be indirectly connected to the element B. It will also be understood that when an element is referred to as “bent,” this expression does not limit the configuration to an element formed or shaped by a bending process, but includes any such angled, curved, or similarly shaped configuration created by any suitable process. 
         [0033]    In addition, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting thereof. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” or “include” and/or “comprising” or “including,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
         [0034]    It will be understood that, although the terms first, second, etc. may be used herein to describe various members, elements, regions, layers and/or sections, these members, elements, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one member, element, region, layer, and/or section from another. Thus, for example, a first member, a first element, a first region, a first layer and/or a first section discussed below could be termed a second member, a second element, a second region, a second layer and/or a second section without departing from the teachings. 
         [0035]    Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper”, and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. 
         [0036]      FIG. 1  is a perspective view of a secondary battery according to an exemplary embodiment and  FIG. 2  is a cross-sectional view illustrating an internal structure of a case in the secondary battery shown in  FIG. 1 . 
         [0037]    Referring to  FIGS. 1 and 2 , the secondary battery  100  according to an exemplary embodiment may include a case  110 , an electrode assembly  120 , an electrode tab  130 , a current collector plate  140 , a first electrode terminal portion  150 , a second electrode terminal portion  160 , a cap plate  170 , a safety vent  180 , and an electrolyte injection unit  190 . 
         [0038]    The case  110  may have a substantially hexahedral shape having an opening through which the electrode assembly  120  may be inserted and arranged. The case  110  may have a space inside the opening to accommodate the electrode assembly  120  and an electrolyte. The case  110  may be made of a metal, such as aluminum or an aluminum alloy, for example. In addition, the electrolyte may include an organic solvent and a lithium salt, for example. The electrolyte may exist in a liquid phase, a solid phase, or a gel phase. Exemplary embodiments do not limit the material of the case  110  to those disclosed herein. 
         [0039]    The electrode assembly  120  may include a first electrode plate, a second electrode plate and a separator interposed between the first electrode plate and the second electrode plate, which may be formed as plates or layers. The electrode assembly  120  may be formed by, e.g., winding or laminating a stacked structure including the first electrode plate, the second electrode plate, and the separator. Here, the first electrode plate may be a positive electrode plate or a negative electrode plate and the second electrode plate may have an opposite polarity to the first electrode plate. The following description will be made assuming that the first electrode plate is a positive electrode plate the second electrode plate is a negative electrode plate. 
         [0040]    The first electrode plate may be formed by applying a first electrode active material, e.g., a lithium-based oxide, on both surfaces of the first electrode plate formed of a metal foil, e.g., an aluminum foil. The second electrode plate may be formed by applying a second electrode active material, e.g., a carbonaceous material, on both surfaces of the second electrode plate formed of a metal foil, e.g., a copper foil. Each of the first electrode plate and the second electrode plate may include an uncoated portion  120   a  that functions as a passage for current flowing between each of the first and second electrode plates and the outside of each of the first and second electrode plates. 
         [0041]    In addition, the separator may be disposed between the first electrode plate and the second electrode plate to prevent short circuiting and to allow the movement of lithium ions. The separator may be formed of, e.g., polyethylene, polypropylene, or a composite film of polypropylene and polyethylene. 
         [0042]    Exemplary embodiments do not limit materials of the first electrode plate, the second electrode plate, and the separator to those disclosed herein. 
         [0043]    The electrode tab  130  may include a first electrode tab  131  and a second electrode tab  132 . 
         [0044]    The first electrode tab  131  may be formed by stacking a tab extending from one side of the uncoated portion of the first electrode plate or by electrically connecting a separate tab to one side of the first electrode plate. The first electrode tab  131  may be formed of a metal, such as aluminum, for example. 
         [0045]    The second electrode tab  132  may also be formed by stacking a tab extending from one side of the uncoated portion of the second electrode plate or by electrically connecting a separate tab to one side of the second electrode plate. The second electrode tab  132  may be formed of a metal, such as copper, for example. Exemplary embodiments do not limit materials of the first electrode tab  131  and the second electrode tab  132  to those disclosed herein. 
         [0046]    The current collector plate  140  may be coupled to the electrode tab  130  and may establish an electrical path for the electrode tab  130 . The current collector plate  140  may include a first current collector plate  141  and a second current collector plate  142 . 
         [0047]    The first current collector plate  141  may include an electrode tab connecting part  141   a  and an electrode terminal connecting part  141   b , and an electrode terminal hole  141   c  may be formed in the electrode terminal connecting part  141   b.    
         [0048]    The electrode tab connecting part  141   a  may have an end electrically connected to the first electrode tab  131  and may be extended along the cap plate  170  to be connected to the electrode terminal connecting part  141   b . A protrusion part  151   c  of the first electrode terminal  151  may be fitted into and coupled to the electrode terminal hole  141   c , thereby electrically connecting the electrode terminal connecting part  141   b  to the first electrode terminal  151 . If a height at which the electrode tab connecting part  141   a  may be connected to the first electrode tab  131  is different from a height at which the electrode terminal connecting part  141   b  may be connected to the first electrode terminal  151 , a region between the electrode tab connecting part  141   a  and the electrode terminal connecting part  141   b  may be bent so that the electrode tab connecting part  141   a  and the electrode terminal connecting part  141   b  may be connected to each other. 
         [0049]    In addition, the first current collector plate  141  may not be formed at a cutout region  141   d  under the electrolyte injection unit  190 . The first current collector plate  141  may be made of a metal, such as aluminum or an aluminum alloy, for example. 
         [0050]    The second current collector plate  142  may also include an electrode tab connecting part and an electrode terminal connecting part, and an electrode terminal hole may be formed in the electrode terminal connecting part. 
         [0051]    The electrode tab connecting part may have an end electrically connected to the second electrode tab  132  and may be extended along the cap plate  170  to be connected to the electrode terminal connecting part. A bottom part of the second electrode terminal  161  may be fitted into and coupled to the electrode terminal connecting part, thereby electrically connecting the electrode terminal connecting part to the second electrode terminal  161 . In addition, if a height at which the electrode tab connecting part may be connected to the second electrode tab  132  is different from a height at which the electrode terminal connecting part may be connected to the second electrode terminal  161 , a region between the electrode tab connecting part and the electrode terminal connecting part may be bent so that the electrode tab connecting part and the electrode terminal connecting part may be connected to each other. 
         [0052]    In addition, the second current collector plate  142  may be made of a metal, such as copper or a copper alloy, for example. 
         [0053]    Exemplary embodiments do not limit materials of the first current collector plate  141  and the second current collector plate  142  to those disclosed herein. 
         [0054]      FIG. 3  is a perspective view of a first electrode terminal portion of the secondary battery shown in  FIG. 1 ,  FIG. 4  is a bottom view of the first electrode terminal portion shown in  FIG. 3 , and  FIG. 5  is a cross-sectional view of the first electrode terminal portion shown in  FIG. 3 . 
         [0055]    Referring to  FIGS. 3 to 5 , the first electrode terminal portion  150  may include a first electrode terminal  151 , an insulation member  152 , a gasket  153 , a first fastening plate  154 , and a first terminal plate  155 . 
         [0056]    The first electrode terminal  151  may include a body part  151   a , a flange  151   b , and a protrusion part  151   c.    
         [0057]    The body part  151   a  may be shaped as a cylinder and may pass through the cap plate  170  to be extended and protruded upwardly a predetermined length. 
         [0058]    The flange  151   b  may be formed to horizontally extend from a bottom side portion of the body part  151   a  and may prevent the first electrode terminal  151  from being dislodged from the cap plate  170 . 
         [0059]    The protrusion part  151   c  may be formed under the body part  151   a  and the flange  151   b . The protrusion part  151   c  may be inserted into the electrode terminal hole  141   c  of the first current collector plate  141  to be electrically connected and coupled to the electrode terminal hole  141   c  by riveting or welding. In addition, the protrusion part  151   c  may pass through the insulation member  152  to be electrically connected to the first current collector plate  141  to constitute a fuse. 
         [0060]    The first electrode terminal  151  may be made of a metal, such as aluminum or an aluminum alloy, for example. 
         [0061]    The insulation member  152  may be installed between the first current collector plate  141  and the flange  151   b  of the first electrode terminal  151 . An electrode terminal hole  152   a , through which the protrusion part  151   c  of the first electrode terminal  151  may pass, may be formed in the insulation member  152 . The insulation member  152  may insulate the flange  151   b  of the first electrode terminal  151  from the first current collector plate  141 . Therefore, the first electrode terminal  151  may be electrically connected to the first current collector plate  141  through the protrusion part  151   c.    
         [0062]    The gasket  153  may be formed between the first electrode terminal  151  and a cap plate terminal hole  170   a  of the cap plate  170  using an insulating material, thereby sealing a gap between the first electrode terminal  151  and the cap plate  170 . Therefore, the gasket  153  may prevent external moisture from permeating into the secondary battery  100  and may prevent the electrolyte accommodated within the secondary battery  100  from effusing to an outside. 
         [0063]    In addition, the gasket  153  may be formed between the first electrode terminal  151  and the first fastening plate  154 , thereby insulating the first electrode terminal  151  from the first fastening plate  154 . 
         [0064]    The first fastening plate  154  may include an electrode terminal hole  154   a  formed therein to allow the first electrode terminal  151  to pass therethrough. The first fastening plate  154  may be fitted onto the first electrode terminal  151  upwardly protruding from the cap plate  170  to be coupled to a top portion of the cap plate  170 . When the first fastening plate  154  is formed of a conductive material, the cap plate  170  may be electrically connected to the first terminal plate  155 . 
         [0065]    The first terminal plate  155  may include an electrode terminal hole  155   a  formed therein to allow the first electrode terminal  151  to pass therethrough. The first terminal plate  155  may be fitted onto the first electrode terminal  151  upwardly protruding from the cap plate  170  and coupled to a top portion of the first fastening plate  154 . In addition, the first terminal plate  155  may be coupled to the first electrode terminal  151  upwardly protruding from the cap plate  170  by riveting or welding. 
         [0066]    The first terminal plate  155  may be made of a metal, such as aluminum or an aluminum alloy, for example. 
         [0067]    The second electrode terminal portion  160  may include a second electrode terminal  161 , a gasket  163 , a second fastening plate  164 , and a second terminal plate  165 . 
         [0068]    The second electrode terminal  161  may include a body part  161   a  and a flange  161   b.    
         [0069]    The body part  161   a  may be shaped as a cylinder, and the flange  161   b  may be extended and protruded horizontally a predetermined length from a side portion of the body part  161   a  and may prevent the second electrode terminal  161  from being dislodged from the cap plate  170 . 
         [0070]    A region of the body part  161   a , which may be formed above the flange  161   b , may pass through the cap plate  170  to be extended and protruded upwardly a predetermined length. In addition, a region of the body part  161   a , which may be formed under the flange  161   b , may be inserted into the electrode terminal hole of the second current collector plate  142  to be electrically connected and coupled to the electrode terminal hole by riveting or welding. In addition, since the flange  161   b  may be brought into contact with the second current collector plate  142 , the flange  161   b  may be electrically connected to the second current collector plate  142 . 
         [0071]    The second electrode terminal  161  may be made of a metal, such as copper or a copper alloy, for example. 
         [0072]    The gasket  163  may be formed between the second electrode terminal  161  and the cap plate  170  using an insulating material, thereby sealing a gap between the second electrode terminal  161  and the cap plate  170 . Therefore, the gasket  163  may prevent external moisture from permeating into the secondary battery  100  and may prevent the electrolyte accommodated within the secondary battery  100  from effusing to an outside. 
         [0073]    In addition, the gasket  163  may be formed between the second electrode terminal  161  and the second fastening plate  164 , thereby insulating the second electrode terminal  161  from the second fastening plate  164 . 
         [0074]    The second fastening plate  164  may include an electrode terminal hole formed therein to allow the second electrode terminal  161  to pass therethrough. The second fastening plate  164  may be fitted into the second electrode terminal  161  upwardly protruding from the cap plate  170  to be coupled to a top portion of the cap plate  170 . The second fastening plate  164  may be made of an insulating material to insulate the second terminal plate  165  from the cap plate  170 . 
         [0075]    The second terminal plate  165  may include an electrode terminal hole formed therein to allow the second electrode terminal  161  to pass therethrough. The second terminal plate  165  may be fitted onto the second electrode terminal  161  upwardly protruding from the cap plate  170  to be coupled to a top portion of the second fastening plate  164 . In addition, the second terminal plate  165  may be coupled to the second electrode terminal  161  upwardly protruding from the cap plate  170  by riveting or welding. 
         [0076]    The second terminal plate  165  may be made of a different metal from the second electrode terminal  151 , such as aluminum or an aluminum alloy, for example. 
         [0077]    The protrusions may be formed only on the first electrode terminal  151 , and only the protrusion part  151   c  of the first electrode terminal  151  may be electrically connected to the first current collector plate  141 . The flange  151   b  may be insulated from the first current collector plate  141  by the insulation member  152 . By contrast, the flange  161   b  of the second electrode terminal  161  may be electrically connected to the second current collector plate  142 . Therefore, since the protrusion part  151   c  of the first electrode terminal  151  forms a narrower current path than the second electrode terminal  161 , the protrusion part  151   c  may function as a fuse. For example, when an over-current flows, the protrusion part  151   c  may be melted due to an increase in the temperature. In such a case, an electrical connection between the first current collector plate  141  and the first electrode terminal  151  may be broken. 
         [0078]    The cap plate  170  may be coupled to a top portion of the case  110  and may seal the opening of the case  110 . In addition, when the cap plate  170  may be coupled to the top portion of the case  110 , the cap plate  170  may be electrically connected to the case  110 . The cap plate  170  may include electrode terminal holes formed therein to allow the first electrode terminal  151  and the second electrode terminal  161  to pass therethrough and protrude. The cap plate  170  may further include a safety vent  180  and an electrolyte injection unit  190 . 
         [0079]    The cap plate  170  may be made of a same material as the case  110 . However, exemplary embodiments do not limit the material of the cap plate  170  to those disclosed herein. 
         [0080]    The safety vent  180  may be centrally positioned on the cap plate  170 . The safety vent  180  may be installed as a separate member in a vent hole that passes through the cap plate  170 , or may be integrally formed with the cap plate  170 . When the internal pressure of the secondary battery  100  increases due to, for example, overcharging, the safety vent  180  may be ruptured, thereby preventing the secondary battery  100  from exploding. 
         [0081]    The electrolyte injection unit  190  may include an electrolyte injection hole and a plug. The electrolyte injection hole may allow an electrolyte to be injected into the secondary battery  100  and the plug may close the electrolyte injection hole to prevent the electrolyte accommodated therein from effusing to the outside of the secondary battery  100 . 
         [0082]    The secondary battery  100  according to exemplary embodiments may include the insulation member  152  between the first electrode terminal  151  and the first current collector plate  141 , and the protrusion part  151   c  formed on the first electrode terminal  151  may pass through the insulation member  152  to be electrically connected to the first current collector plate  141  to constitute a fuse. Therefore, with only the configuration of the electrode terminal portion  150  and without installing a separate member in the secondary battery  100 , the flow of current may be cut off when over-current flows due to overcharging or abnormality, thereby preventing the secondary battery  100  from exploding. 
         [0083]      FIG. 6  is a bottom view of a first electrode terminal portion of a secondary battery according to another exemplary embodiment and  FIG. 7  is a cross-sectional view of the first electrode terminal portion shown in  FIG. 6 . 
         [0084]    Referring to  FIGS. 6 and 7 , the secondary battery  200  according to another exemplary embodiment may include a case  110 , an electrode assembly  120 , an electrode tab  130  including the first electrode tab  131 , a current collector plate  240 , a first electrode terminal portion  250 , a second electrode terminal portion  160 , a cap plate  170 , a safety vent  180 , and an electrolyte injection unit  190 . In the present exemplary embodiment, the same functional component is denoted by the same reference numeral as in the previous exemplary embodiment, and the following description will focus on differences between the present and previous exemplary embodiments. 
         [0085]    The current collector plate  240  may include a first current collector plate  241  and a second current collector plate  142 . The first current collector plate  241  may be coupled to the first electrode tab  131  and may establish an electrical path for the electrode tab  130 . 
         [0086]    The first current collector plate  241  may include an electrode tab connecting part  241   a  and an electrode terminal connecting part  241   b , and a first electrode terminal hole  241   c  and a second electrode terminal hole  241   d  may be formed in the electrode terminal connecting part  241   b.    
         [0087]    A first protrusion part  251   c  and a second protrusion part  251   d  of the first electrode terminal  251  may be inserted into the first electrode terminal hole  241   c  and the second electrode terminal hole  241   d , respectively, such that the electrode terminal connecting part  241   b  may be electrically connected to a first electrode terminal  251  of the first electrode terminal portion  250 . 
         [0088]    The first electrode terminal portion  250  may include a first electrode terminal  251 , an insulation member  252 , a gasket  153 , a first fastening plate  154 , and a first terminal plate  155 . 
         [0089]    The first electrode terminal  251  may include a body part  251   a , a flange  251   b , and the first protrusion part  251   c  and the second protrusion part  251   d.    
         [0090]    The first protrusion part  251   c  and the second protrusion part  251   d  may be formed under the body part  251   a  and the flange  251   b . The first protrusion part  251   c  and the second protrusion part  251   d  may be formed at a region where a line A-A passing through both of the first protrusion part  251   c  and the second protrusion part  251   d  may be perpendicular to a lengthwise direction of the first current collector plate  241 . For example, the first protrusion part  251   c  and the second protrusion part  251   d  may be equidistantly spaced apart from the first electrode tab  131 . In addition, the first protrusion part  251   c  and the second protrusion part  251   d  may be inserted into the first electrode terminal hole  241   c  and the second electrode terminal hole  241   d  of the first current collector plate  241 , respectively, to be electrically connected and coupled to the first and second electrode terminal holes  241   c  and  241   d  by riveting or welding. In addition, the first protrusion part  251   c  and the second protrusion part  251   d  may pass through the insulation member  252  to be electrically connected to the first current collector plate  241  to constitute a fuse. 
         [0091]    The insulation member  252  may be installed between the first current collector plate  241  and the flange  251   b  of the first electrode terminal  251 . A first electrode terminal hole  252   a  and a second electrode terminal hole  252   b , through which the first protrusion part  251   c  and the second protrusion part  251   d  of the first electrode terminal  251 , respectively, may pass, may be formed in the insulation member  252 . The insulation member  252  may insulate the flange  251   b  of the first electrode terminal  251  from the first current collector plate  241 . Therefore, the first electrode terminal  251  may be electrically connected to the first current collector plate  241  through the first protrusion part  251   c  and the second protrusion part  251   d.    
         [0092]    The first protrusion part  251   c  and the second protrusion part  251   d  of the first electrode terminal  251  may be electrically connected to the first current collector plate  241 , and the flange  251   b  may be insulated from the first current collector plate  241  by the insulation member  252 . Therefore, since the first protrusion part  251   c  and the second protrusion part  251   d  of the first electrode terminal  251  may each function as fuses of the first protrusion part  251   c  and the second protrusion part  251   d  of the first electrode terminal  251 , the first electrode terminal portion  250  may be provided with two fuses. 
         [0093]    Additionally, the first protrusion part  251   c  and the second protrusion part  251   d  may prevent the first electrode terminal  251  from being rotated in a state in which the first electrode terminal  251  passes through the first fastening plate  154  and the first terminal plate  155 . 
         [0094]    When an over-current flows in the secondary battery  200  due to overcharging or abnormality, the secondary battery  200  including two fuses may more stably cut off the flow of current, compared to the secondary battery  200  including a single fuse, thereby preventing the secondary battery  200  from exploding. 
         [0095]      FIG. 8  is a bottom view of a first electrode terminal portion of a secondary battery according to still another exemplary embodiment, and  FIG. 9  is a cross-sectional view of the first electrode terminal portion shown in  FIG. 8 . 
         [0096]    Referring to  FIGS. 8 and 9 , the secondary battery  300  according to still another exemplary embodiment may include a case  110 , an electrode assembly  120 , an electrode tab  130  including the first electrode tab  131 , a current collector plate  340 , a first electrode terminal portion  350 , a second electrode terminal portion  160 , a cap plate  170 , a safety vent  180 , and an electrolyte injection unit  190 . In the present exemplary embodiment, the same functional component is denoted by the same reference numeral as in the previous exemplary embodiment, and the following description will focus on differences between the present and previous exemplary embodiments. 
         [0097]    The current collector plate  340  may include a first current collector plate  341  and a second current collector plate  142 . The first current collector plate  341  may be coupled to the first electrode tab  131  and may establish an electrical path for the electrode tab  130 . 
         [0098]    The first current collector plate  341  may include an electrode tab connecting part  341   a  and an electrode terminal connecting part  341   b , and a first electrode terminal hole  341   c  and a second electrode terminal hole  341   d  may be formed in the electrode terminal connecting part  341   b.    
         [0099]    A first protrusion  351   c  and a second protrusion  351   d  of the first electrode terminal  351  may be inserted into the first electrode terminal hole  341   c  and the second electrode terminal hole  341   d , respectively, such that the electrode terminal connecting part  341   b  may be electrically connected to the first electrode terminal  351 . 
         [0100]    The first electrode terminal portion  350  may include a first electrode terminal  351 , an insulating member  352 , a gasket  153 , a first fastening plate  154 , and a first terminal plate  155 . 
         [0101]    The first electrode terminal  351  may include a body part  351   a , a flange  351   b , a first protrusion  351   c , and the second protrusion  351   d.    
         [0102]    The first protrusion  351   c  and the second protrusion  351   d  may be formed under the body part  351   a  and the flange  351   b . The first protrusion  351   c  and the second protrusion  351   d  may be formed at a region where a line B-B passing through both of the first protrusion part  351   c  and the second protrusion part  351   d  may be parallel to a lengthwise direction of the first current collector plate  341 . For example, the first protrusion  351   c  and the second protrusion  351   d  may be sequentially formed in a lengthwise direction of the first current collector plate  341 . The lengthwise direction being in a direction of the first electrode tab  131 . In addition, the first protrusion  351   c  and the second protrusion  351   d  may be inserted into the first electrode terminal hole  341   c  and the second electrode terminal hole  341   d  of the first current collector plate  341 , respectively, to be electrically connected and coupled to the first and second electrode terminal holes  341   c  and  341   d  by riveting or welding. In addition, the first protrusion part  351   c  and the second protrusion part  351   d  may pass through the insulation member  352  to be electrically connected to the first current collector plate  341  to constitute a fuse. 
         [0103]    The insulating member  352  may be installed between the first current collector plate  341  and the flange  351   b  of the first electrode terminal  351 . A first electrode terminal hole  352   a  and a second electrode terminal hole  352   b , through which the first protrusion  351   c  and the second protrusion  351   d  of the first electrode terminal  351  may pass, may be formed in the insulating member  352 . The insulating member  352  may insulate the flange  351   b  of the first electrode terminal  351  from the first current collector plate  341 . Therefore, the insulating member  352  may insulate the flange  351   b  of the first electrode terminal  351  from the first current collector plate  341 . Therefore, the first electrode terminal  351  may be electrically connected to the first current collector plate  341  through the first protrusion  351   c  and the second protrusion  351   d.    
         [0104]    Since the first protrusion  351   c  and the second protrusion  351   d  of the first electrode terminal  351  may each function as fuses, the first electrode terminal portion  350  may be provided with two fuses. In addition, since the first protrusion  351   c  and the second protrusion  351   d  may be sequentially formed along a path of current flowing through the first electrode plate of the electrode assembly  120 , the first electrode tab  131 , the first current collector plate  341 , and the first electrode terminal  351 , the first protrusion  351   c  closer to the first electrode tab  131  may operate earlier than the second protrusion  351   d  when an over-current flows. In such a manner, an operating sequence of the respective fuses may be determined. 
         [0105]    In the secondary battery  300  according to still another exemplary embodiment, the order of priority is given to two fuses, and when an over-current flows in the secondary battery  300  due to overcharging or abnormality, the flow of current may be more stably cut off by the two fuses formed in the secondary battery  300 , compared to a case when the secondary battery  300  includes two fuses equidistantly spaced apart from the first current collector plate  341 , thereby preventing the secondary battery  300  from exploding. 
         [0106]    Therefore, the secondary battery according to exemplary embodiments may further include a protrusion formed in the first electrode terminal portion depending on the purpose. For example, three or more fuses may be formed in the first electrode terminal portion. In addition, the order of priority for the respective fuses may be determined by adjusting distances between each of the respective fuses and the first electrode tab. 
         [0107]    By way of summation and review, a secondary battery may include a case for housing the electrode assembly together with an electrolyte and a cap assembly installed to seal the case. In addition, electrode tabs and electrode terminals may be connected to the electrode assembly and exposed or protruded through the cap plate. When an over-current flows in the secondary battery due to overcharging or abnormality, explosion of the secondary battery may result. Accordingly, there is a need for a secondary battery having improved safety. 
         [0108]    Exemplary embodiments may provide a secondary battery including a fuse in an electrode terminal. As described above, the secondary battery according to exemplary embodiments may include a protrusion formed in an electrode terminal portion to function as a fuse, thereby preventing the secondary battery from exploding by cutting off the flow of current when an over-current flows due to overcharging or abnormality. 
         [0109]    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. In some instances, as would be apparent to one of ordinary skill in the art as of the filing of the present application, features, characteristics, and/or elements described in connection with a particular embodiment may be used singly or in combination with features, characteristics, and/or elements described in connection with other embodiments unless otherwise specifically indicated. Accordingly, it will be understood by those of 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.