Patent Publication Number: US-2022223978-A1

Title: Secondary battery

Description:
TECHNICAL FIELD 
     The present invention relates to a secondary battery capable of suppressing deformation of an electrode assembly and a current collector. 
     BACKGROUND ART 
     Unlike a primary battery that cannot be charged, a rechargeable battery can be charged and discharged. A low capacity battery including a battery cell in the form of a pack is used in small portable electronic devices, such as cellular phones or camcorders, while a high capacity battery including tens of battery cells connected to one another is widely used as a power source for driving a motor, e.g., hybrid vehicles, or the like. 
     Such rechargeable secondary batteries are manufactured in various shapes, representative examples of the shapes may include a cylindrical shape and a prismatic shape. The secondary battery is configured by inserting, into a case, an electrolyte and an electrode assembly which is formed by interposing a separator as an insulator, between positive and negative electrode plates, and installing a cap assembly having electrode terminals in the case. 
     As the capacity of the secondary battery gradually increases, various efforts are required to promote user safety. 
     DESCRIPTION OF EMBODIMENTS 
     Technical Problem 
     Provided is a secondary battery in which retainers are coupled between a case and the uncoated portions of electrode assemblies so that the electrode assemblies and current collectors can be fixed and prevented from being separated. 
     Solution to Problem 
     A secondary battery according to the present invention comprises: a plurality of electrode assemblies of which each has a cathode plate and an anode plate arranged with a separator therebetween, and which includes the uncoated portions of the cathode plate and the anode plate; a case in which the electrode assemblies are embedded; a cap plate coupled to the case; current collectors respectively coupled to the uncoated portions of the plurality of electrode assemblies through a plurality of coupling portions; and retainers inserted and coupled to on one side of the current collectors, wherein the retainers are coupled to the current collectors through protrusion portions having a width greater than that between the coupling portions of the current collectors. 
     Here, the protrusion portions of the retainers may protrude from the plate-shaped body portion and be coupled between the coupling portions of the current collectors. 
     In addition, the protrusion portions may be formed between the coupling portions of the current collectors and may include may include a central portion contacting the electrode assembly, and a plurality of elastic portions formed on both sides with respect to the central portion and contacting the coupling portions. 
     In addition, the central portion may be formed to protrude from the body portion, and the end of a head may contact the electrode assembly. 
     In addition, the elastic portions may protrude from one side of the peripheral edge of a cut-out hole provided in the body portion, and may be formed to be spaced apart from the central portion. 
     In addition, the total width of the plurality of elastic portions may be larger than a distance between the coupling portions of the current collectors. 
     In addition, each of the plurality of elastic portions may have one end coupled to the central portion while cutting the other end thereof opposite to the one end. 
     In addition, the total width of the other ends of the plurality of elastic portions may be larger than the distance between the coupling portions of the current collectors. 
     In addition, each of the retainers may further include an additional protrusion portion which is formed between the coupling portions of the current collectors and is configured to have an empty interior. 
     In addition, the additional protrusion portion may have at least one partition wall formed therein. 
     In addition, the retainers may be formed of polypropylene (PP) or polyethylene (PE). 
     Advantageous Effects of Disclosure 
     The secondary battery according to the present invention may include an electrode assembly and a retainer coupled from one side of a current collector, and may reduce the weight and material of the retainer, and allow the retainer to be maintained at a stably coupled state. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a secondary battery according to an embodiment of the present invention. 
         FIG. 2  is a cross-sectional view taken along line A-A′ of  FIG. 1 . 
         FIG. 3  is an exploded perspective view illustrating the sequence in which an electrode assembly, current collectors, and retainers are coupled in a secondary battery according to an embodiment of the present invention. 
         FIG. 4  is a perspective view illustrating a state in which an electrode assembly, current collectors, and retainers are coupled in a secondary battery according to an embodiment of the present invention. 
         FIGS. 5A to 5C  are a perspective view, a front view, and a plan view illustrating the configuration of a retainer in a secondary battery according to an embodiment of the present invention. 
         FIG. 6  is a partial cross-sectional view illustrating a state in which a retainer is coupled to a current collector in a secondary battery according to an embodiment of the present invention. 
         FIG. 7  is a partial perspective view illustrating a state in which a retainer is coupled to a current collector in a secondary battery according to an embodiment of the present invention. 
         FIG. 8  is an enlarged plan view illustrating a coupling state of a second region of a retainer in a secondary battery according to an embodiment of the present invention. 
         FIGS. 9A to 9C  are a perspective view, a front view, and a plan view illustrating the configuration of a retainer in a secondary battery according to another embodiment of the present invention. 
         FIG. 10  is a partial cross-sectional view illustrating a state in which a retainer is coupled to a current collector in a secondary battery according to another embodiment of the present invention. 
     
    
    
       
     
       
         
           
               
             
               
                   
               
               
                 [Explanation of reference numerals for major parts] 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                   
                 100: Secondary battery 
               
               
                   
                 110: Case 
               
               
                   
                 120: Electrode assembly 
               
               
                   
                 122: Uncoated portion 
               
               
                   
                 130: Current collector 
               
               
                   
                 133: Coupling portions 
               
               
                   
                 133a: First coupling portion 
               
               
                   
                 133b: Second coupling portion 
               
               
                   
                 133c: Third coupling portion 
               
               
                   
                 133d: Fourth coupling portion 
               
               
                   
                 140: Retainers 
               
               
                   
                 141: Body portion 
               
               
                   
                 142: First protrusion portion 
               
               
                   
                 142a: Partition wall 
               
               
                   
                 143, 243: Second protrusion portion 
               
               
                   
                 143a: Central portion 
               
               
                   
                 143b: Elastic portion 
               
               
                   
                 143c: Head 
               
               
                   
                 143d, 243d: Head 
               
               
                   
                 150: first insulation member 
               
               
                   
                 160: Cap plate 
               
               
                   
                 170: second insulation member 
               
               
                   
                 180: Nut 
               
               
                   
               
            
           
         
       
     
     BEST MODE 
     Hereinafter, example embodiments of the present invention will be described in detail. 
     Embodiments of the present invention are provided to more completely explain the present invention to one skilled in the art. However, the following example embodiments may be modified in various other forms, and the scope of the present invention is not limited to the following example embodiments set forth herein. Rather, these example embodiments are provided so that this disclosure will be thorough and complete and will convey the aspects and features of the present invention to a person skilled in the art. 
     In addition, in the accompanying drawings, sizes or thicknesses of various components are exaggerated for brevity and clarity. Like numbers refer to like elements throughout. 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 therebetween such that the element A and the element B are indirectly connected to each other. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. 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 that the terms “comprise” and/or “comprising,” when used in this specification, specify the presence of stated features, numbers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, elements, components, and/or groups thereof. 
     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 of the present invention. 
     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 element or feature in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “on” or “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. 
     Hereinafter, a configuration of a secondary battery according to an embodiment of the present invention will be described. 
       FIG. 1  is a perspective view of a secondary battery according to an embodiment of the present invention.  FIG. 2  is a cross-sectional view taken along line A-A′ of  FIG. 1 .  FIG. 3  is an exploded perspective view illustrating the sequence in which an electrode assembly, current collectors, and retainers are coupled in a secondary battery according to an embodiment of the present invention.  FIG. 4  is a perspective view illustrating a state in which an electrode assembly, current collectors, and retainers are coupled in a secondary battery according to an embodiment of the present invention. 
     Referring to  FIGS. 1 to 4 , the secondary battery  100  according to the present invention includes a case  110 , an electrode assembly  120  inserted into the case  110 , and current collectors  130  connected to the electrode assembly  120 , retainers  140  coupled from one side of each of the current collectors  120 , a first insulation member  150  formed on top of the current collector  130 , a cap plate  160  for sealing the case  110 , and a second insulating member  170  formed on the cap plate  160 , and a nut  180  formed on the second insulation member  170 . 
     The case  110  is formed in the shape of a substantially hexahedron having an accommodating space therein and an opening formed thereon. The case  110  accommodates the electrode assembly  120  and an electrolyte in the accommodation space. The case  110  is formed of a conductive metal such as aluminum, an aluminum alloy, or nickel-plated steel. Since  FIG. 1  shows a state in which the case  140  and the cap plate  160  are coupled to each other, In  FIG. 1 , the opening is not shown, but corresponds to a portion in which the peripheral portion of the cap plate  160  is substantially opened. In addition, the inner surface of the case  110  may be subjected to insulation treatment so as to be insulated from the electrode assembly  120 , the current collector  130 , and the cap plate  160 . 
     The electrode assembly  120  is formed by winding or overlapping a laminate of a first electrode plate, a second electrode plate, and a separator positioned therebetween, which are formed in a thin plate shape or a film shape. For example, the first electrode plate may act as an anode, and the second electrode plate may act as a cathode, and vice versa. 
     The first electrode plate is formed by coating an active material such as graphite or carbon on an electrode current collector formed of a metal foil such as copper or nickel, and an uncoated portion is formed in a region to which the active material is not applied. The second electrode plate is formed by coating an active material such as a transition metal oxide on an electrode current collector formed of a metal foil such as aluminum, and includes an uncoated portion that is a region to which the active material is not applied. The separator is positioned between the first electrode plate and the second electrode plate to prevent short circuit and allow lithium ions to move, and may be made of polyethylene, polypropylene, or a composite film of polyethylene and polypropylene. Meanwhile, the present invention does not limit the materials of the electrode plate and the separator to those listed herein. 
     The electrode assembly  120  may include a plurality of electrode assemblies and is substantially accommodated in the case  110  together with the electrolyte. Although four of the electrode assembly  120  are illustrated in the present invention, the number of the electrode assembly  120  is not limited thereto. The electrolyte may be formed of a lithium salt such as LiPF6 or LiBF4 in an organic solvent such as ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), or dimethyl carbonate (DMC). In addition, the electrolyte may be in a liquid, solid or gel phase. 
     The electrode assembly  120  which is formed by winding the electrode plates may be configured such that a cathode plate and an anode plate, each having a coating portion  121  that is a region to which an active material is applied, and an uncoated portion  122  to which an active material is not applied, are stacked or wound with a separator positioned therebetween. In particular, in the configuration of the electrode assembly  120 , a pair of uncoated portions  122  respectively connected to the cathode plate and the anode plate may protrude in opposite directions from both sides of the electrode assembly  120 . Accordingly, the uncoated portions  122  are compressed with each other to function as a cathode tab and an anode tab, respectively, on both sides of the electrode assembly  120 . 
     In addition, when the electrode assembly  120  includes a plurality of electrode assemblies, the electrode assembly  120  may be aligned such that the uncoated portions  122  of the same electrode are positioned in the same direction. In addition, electrodes of the secondary battery are formed through a pair of current collectors  130  connected to the uncoated portions  122 . 
     Here, the uncoated portion  122  may be coupled to the current collector  130  through welding. In a state in which a plurality of electrode assemblies  120  are arranged and a plurality of uncoated portions  122  are provided, the current collector  130  is parallel to the uncoated portion  122  in a vertical direction (the z-axis direction in the drawing). Accordingly, the uncoated portions  122  formed in the plurality of electrode assemblies  120  may be electrically connected to each other by the current collector  130 . 
     The current collector  130  is provided as a pair and is connected to the uncoated portions  122  each having one polarity. The current collector  130  is connected to the electrode assembly  120  through the uncoated portion  122 , and is exposed to the outside of the cap plate  160  to form an input/output path of an electrical signal. 
     The current collector  130  includes a body portion  131  that is formed parallel to the horizontal direction (the x-axis direction in  FIG. 1 ) of the electrode assembly  110 , a bent portion  132  that is bent from the body portion  131  in the substantially vertical direction (the z-axis direction of  FIG. 1 ), a coupling portion  133  that extends from the bent portion  132  and is coupled to the uncoated portion  122 , and a terminal portion  134  that protrudes in the vertical direction (the z-axis direction of  FIG. 1 ) and is exposed to the outside of the cap plate  160 . 
     The body portion  131  is formed in a substantially flat plate shape and is formed on the upper portion of the electrode assembly  110  in the horizontal direction along the length of the electrode assembly  110 . 
     The bent portion  132  is bent in the vertical direction from the body portion  131  and extends in parallel toward the uncoated portion  122 . The bent portion  132  has a width enough to cover the uncoated portion  122 . 
     When a plurality of coupling portions  133  are provided to correspond to the number of electrode assemblies  120 , for example, when the number of electrode assemblies  120  is four, the coupling portion  133  may include first to fourth coupling portions  133   a - 133   d . The coupling portion  133  is formed to extend from the bent portion  132  in the vertical direction (the −z-axis direction of  FIG. 1 ). The coupling portion  133  is provided in the same number as the uncoated portion  122 , and each of the coupling portions  133  extends in parallel while making contact with the uncoated portion  122 . That is, the side surface of the coupling portion  133  and the side surface of the uncoated portion  122  extend in parallel with each other while contacting each other in the vertical direction (the −z-axis direction). In addition, the coupling portion  133  forms two pairs  133   a  and  133   b , and  133   c  and  133   d , and one pair of coupling portions, for example, a first coupling portion  133   a  and a second coupling portion  133   b , may be located to contact the interior sides of the pair of uncoated portions  122 . That is, the pair of coupling portions  133   a  and  133   b  may be located in a state in which the pair of coupling portions  133   a  and  133   b  are in contact with the opposite inner surfaces of the pair of uncoated portions  122 . 
     The terminal portion  134  is formed to protrude from the body portion  131  in the vertical direction (the z-axis direction of  FIG. 1 ). Here, the terminal portion  134  may be integrally formed with the current collector  130  or may be separately provided and coupled by, for example, bolting. The terminal portion  134  further protrudes above the cap plate  160  to form an electrode terminal. In addition, the terminal portion  134  has a screw thread formed on the outer circumferential surface thereof, and thus may be coupled with the nut  180  coupled from above. 
     Hereinafter, the configuration of the retainer  140  will be described with reference to  FIGS. 5A to 8 . 
       FIGS. 5A to 5C  are a perspective view, a front view, and a plan view illustrating the configuration of a retainer in a secondary battery according to an embodiment of the present invention.  FIG. 6  is a partial cross-sectional view illustrating a state in which a retainer is coupled to a current collector in a secondary battery according to an embodiment of the present invention.  FIG. 7  is a partial perspective view illustrating a state in which a retainer is coupled to a current collector in a secondary battery according to an embodiment of the present invention.  FIG. 8  is an enlarged plan view illustrating a coupling state of a second region of a retainer in a secondary battery according to an embodiment of the present invention. 
     Referring to the drawings, the retainer  140  may include a pair of retainers, which are respectively coupled to the current collectors  130  from both sides of the electrode assembly  120 . The retainer  140  may be made of a plastic material such as polypropylene (PP) or polyethylene (PE) having elasticity. The retainer  140  may be coupled to the coupling portion  133  of each of the current collectors  130 , and may be stably coupled between the first to fourth coupling portions  133   a - 133   d  constituting the coupling portion  133  through an elastic restoring force. 
     Specifically, the retainer  140  basically includes a substantially flat body portion  141  and may include a first protrusion portion  142  that protrudes in one direction from the surface thereof, and a plurality of second protrusion portions  143  formed on both sides of the first protrusion portion  142  with respect to. 
     The body portion  141  is provided in the flat plate shape, and thus, when coupled to the current collector  130 , the retainer  140  may be formed in close contact with the current collector  130  in the longitudinal direction. 
     In addition, the body portion  141  may have a first cutout portion  141   a  at the center thereof, and the first protrusion portion  142  may protrude along the peripheral edge of the first cutout portion  141   a . Accordingly, the first protrusion portion  142  may have an empty shape, thereby reducing the weight and material of the retainer  140 . 
     In addition, the body portion  141  includes a plurality of second cutout portions  141   b  around the first cutout portion  141   a , and some portions of the second protrusion portions  143  may protrude from one-side edges of the second cutout portions  141   b . Accordingly, although the second protrusion portions  143  are coupled from the body portion  141  but are still movable, the elastic force of the second protrusion portions  143  may be increased. 
     The first protrusion portion  142  may be formed to elongate in the vertical direction along the surface of the body portion  141 . In addition, since the first protrusion portion  142  is formed along the circumference of the first cutout portion  141   a  of the body portion  141 , the inside thereof is empty, thereby reducing the weight. However, one or more partition walls  142   a  for maintaining the strength may be formed inside the first protrusion portion  142 . The partition walls  142   a  may be disposed at regular intervals along the vertical direction. Accordingly, when the first protrusion portion  142  touches the electrode assembly  120  by passing through the current collector  130 , for example, between the second coupling portion  133   b  and the third coupling portions  133   c , the partition wall  142   a  supports the first protrusion portion  142  to maintain the shape thereof. In addition, by the partition wall  142 , the first protrusion portion  142  can be maintained at a stably coupled state with respect to the electrode assembly  120 . 
     Meanwhile, an air hole  142   c  may be further formed in the approximately center of the first protrusion portion  142 . When the protrusion portion  142  is finally fixed to the electrode assembly  120 , the air hole  142   c  is designed to allow the internal air to escape, thereby enabling closely contacting. 
     The second protrusion portion  143  may be positioned along the surface of the body portion  141  and around the first protrusion portion  142 . The second protrusion portion  143  may include a central portion  143   a  that protrudes in one direction from the second cutout portion  141   b  of the body portion  141 , and elastic portions  142   b  that are formed to be horizontally symmetrical with each other around the central portion  143   a  and protrude from one side of the circumference of the second cutout portion  141   b.    
     Here, the central portion  143   a  may include a head  143   c  that protrudes perpendicular to the body portion  141 . Here, when the retainer  140  is coupled to the current collector  130 , the head  143   c  of the central portion  143   a  may pass between the first coupling portion  133   a  and the second coupling portion  133   b  and between the third coupling portion  133   c  and the fourth coupling portion  133   d  in the current collector  130  to then come into contact with the electrode assembly  120 . Therefore, the central portion  143   a  may allow the second protrusion portion  143  to be maintained at a fixed position with respect to the current collector  130  and the electrode assembly  120 . 
     Meanwhile, the elastic portions  143   b  may be disposed on both sides of the central portion  143   a  and may protrude from the edge of one side of the circumference the second cutout portion  141   b . The elastic portions  143   b  may be formed such that the width of opposing heads  143   d  is larger than that of the head  143   c  of the central portion  143   a . Specifically, the elastic portions  143   b  are formed such that the width (b) of the opposing heads  143   d  is larger than a distance (a) between the first coupling portion  133   a  and the second coupling portion  133   b  and between the third coupling portion  133   c  and the fourth coupling portion  133   d  in the current collector  130 . Accordingly, the heads  143   d  of the elastic portions  143   b  may be pressed between the first coupling portion  133   a  and the second coupling portion  133   b  of the current collector  130  and between the third coupling portions  133   c  and the fourth coupling portions  133   d , and the retainer  140  may be stably coupled to the current collector  130  through the elastic restoring force of the heads  143   d.    
     The first insulation member  150  is formed on the body portion  131  of the current collector  130 . The first insulation member  150  is formed between the current collector  130  and the cap plate  160 . The first insulation member  150  electrically insulates the current collector  130  and the cap plate  160  from each other. However, the first insulation member  150  may have a terminal hole formed therein to allow the terminal portion  134  of the current collector  130  to pass through the first insulation member  150  to then be upwardly exposed from the cap plate  160 . 
     The cap plate  160  is formed at the upper portion of the case  110  and is coupled to the case  110 . The cap plate  160  seals the case  110  to prevent leakage of the electrolyte inside the case  110 . The cap plate  160  may have a terminal hole formed therein to allow the terminal portion  134  of the current collector  130  to pass through the terminal hole to then upwardly protrude from the cap plate  160 . The cap plate  160  may include an injection hole for injecting an electrolyte into one region thereof, and an injection plug  161  that fills the injection hole after the electrolyte is injected. In addition, the cap plate  160  includes a safety vent  162  approximately at the center. In the safety vent  162 , when gas is generated inside the case  110  due to, for example, overcharging, and the pressure inside the case  110  is higher than a reference pressure, the cap plate  160  is opened earlier than other parts of the cap plate  160  to release the gas, thereby reducing the risk of explosion due to an increase in internal pressure. 
     The second insulation member  170  is formed on the upper surface of the cap plate  160 , specifically around the terminal portion  134  of the current collector  130 . The second insulation member  170  electrically separates the cap plate  160  and the terminal portion  134  from each other. In addition, the second insulation member  171  allows the nut  180  coupled to the terminal portion  134  on the upper portion of the cap plate  160  to be electrically independent from the cap plate  160 . 
     The nut  180  is coupled to the terminal portion  134  from above. The nut  180  is engaged with a screw thread of the terminal portion  134  through a screw thread formed therein. The nut  180  is fastened to each of the terminal portions  134  and thus fixes the terminal portion  134  to the cap plate  160 . Accordingly, the position of the electrode assembly  120  that is coupled to the electrode terminal  134  is also fixed inside the case  110 . 
     As described above, the secondary battery  100  according to an embodiment of the present invention includes the retainers  140  coupled from the side portions of the electrode assembly  120  and the current collector  130 , and allows the retainers  140  to be maintained at a stably coupled state while reducing the weight and material of the retainers  140 . 
     Hereinafter, a configuration of a secondary battery according to another embodiment of the present invention will be described. 
       FIGS. 9A to 9C  are a perspective view, a front view, and a plan view illustrating the configuration of a retainer in a secondary battery according to another embodiment of the present invention.  FIG. 10  is a partial cross-sectional view illustrating a state in which a retainer is coupled to a current collector in a secondary battery according to another embodiment of the present invention. 
     Referring to  FIGS. 9A to 9C , the secondary battery according to another embodiment of the present invention may include a retainer  240 . Of course, the secondary battery according to another embodiment of the present invention may also further include a case  110 , an electrode assembly  120 , a current collector  130 , a first insulation member  150 , a cap plate  160 , a second insulation member  170 , and a nut  180 , which are the same as those of the previous embodiment, except for the retainer  140 , and a detailed description will not be given. 
     The retainer  240  may include a body portion  241 , a first protrusion portion  142 , and a plurality of second protrusion portions  243  formed on both sides of the first protrusion portion  142 . 
     Here, the body portion  241  is mostly the same as that of the previous embodiment, but slightly differs from that of the previous embodiment with respect to the configuration of second cutout portions  241   c . In detail, as will later be described, elastic portions  243   b  and heads  243   d  of the second protrusion portions  243  do not protrude from the second cutout portions  241   c , but are connected to central portions  243   a  of the protrusion portions  243   b . Accordingly, the second cutout portions  241   c  are configured to be separated from the elastic portions  243   b  and the heads  243   d.    
     Meanwhile, the second protrusion portions  243  may have the heads  243   d  coupled to both sides from the central portions of the elastic portions  243   b . The width of the heads  243   d  is larger than a distance between the first coupling portion  133   a  and the second coupling portion  133   b  and between the third coupling portion  133   c  and the fourth coupling portion  133   d  in the current collector  130 . Accordingly, the heads  243   d  are inwardly pressed and coupled between the first coupling portion  133   a  and the second coupling portion  133   b  and between the third coupling portions  133   c  and the fourth coupling portions  133   d , respectively, in the current collector  130 , thereby maintaining a stably coupled state through an elastic restoring force. 
     While the foregoing embodiment has been described to practice the secondary battery of the present disclosure, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the following claims. 
     INDUSTRIAL APPLICABILITY 
     The present invention provides a secondary battery in which retainers are coupled between a case and the uncoated portions of electrode assemblies so that the electrode assemblies and current collectors can be fixed and prevented from being separated.