Patent Publication Number: US-2013236771-A1

Title: Rechargeable battery and method of manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 61/608,281, filed on Mar. 8, 2012, and entitled: “Electrode, Fabricating Method Thereof, And Rechargeable Battery,” which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     1. Field 
     Embodiments relate to a rechargeable battery and a method of manufacturing the same. 
     2. Description of the Related Art 
     Unlike a primary battery that is incapable of being recharged, a rechargeable battery may be repeatedly charged and discharged. A low-capacity rechargeable battery may be used for a small portable electronic device, e.g., a mobile phone, a laptop computer, and/or a camcorder. A large-capacity battery may be used as a power supply for, e.g., driving a motor of a hybrid vehicle or the like. 
     A large-capacity and high power rechargeable battery using a non-aqueous electrolyte of high energy density has been considered. The high power rechargeable batteries may be connected to each other in series or in parallel to configure a high power and large capacity battery module. 
     The rechargeable battery may include an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. The positive electrode and the negative electrode may each have a structure in which an active material is coated on a current collector formed of metal, and on the current collector, a coated region coated with the active material and an uncoated region without the active material are formed. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it 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 
     Embodiments are directed to a rechargeable battery and a method of manufacturing the same. 
     The embodiments may be realized by providing a rechargeable battery including an electrode assembly, the electrode assembly including a first electrode, a second electrode, and a separator between the first electrode and the second electrode; and a case accommodating the electrode assembly, wherein each of the first and second electrodes includes a coated region having an active material layer on a current collector and an uncoated region free of the active material layer, and in at least one electrode of the first and second electrodes, the current collector is characterized by an x-ray diffraction pattern in which a ratio of an FWHM of a largest peak:an FWHM of a second largest peak of the current collector in the uncoated region is greater than a ratio of an FWHM of a largest peak:an FWHM of a second largest peak of the current collector in the coated region: 
     The ratio of the FWHM of the largest peak:the FWHM of the second largest peak of the current collector in the uncoated region may be about 1.3 to about 1.6 times the ratio of the FWHM of the largest peak:the FWHM of the second largest peak of the current collector in the coated region. 
     In the at least one electrode, the current collector may be characterized by an x-ray diffraction pattern in which a ratio of an FWHM of a largest peak:an FWHM of a second largest peak of the current collector in the uncoated region is about 1.4 to about 2.0. 
     The current collector of the at least one electrode may have an average thickness in the uncoated region smaller than an average thickness thereof in the coated region. 
     In the at least one electrode, the average thickness of the current collector in the uncoated region may be about 80 to about 95% of the average thickness of the current collector in the coated region. 
     The current collector of each of the first electrode and the second electrode may be characterized by an x-ray diffraction pattern in which a ratio of an FWHM of a largest peak:an FWHM of a second largest peak of the current collector in the uncoated region is greater than a ratio of an FWHM of a largest peak:an FWHM of a second largest peak of the current collector in the coated region. 
     The uncoated regions of each of the electrodes may extend along a side end of the respective current collectors. 
     The embodiments may also be realized by providing a method of manufacturing a rechargeable battery, the method comprising preparing an electrode such that preparing the electrode includes coating an active material on a portion of a current collector to form a coated region and a preliminary uncoated region, the preliminary uncoated region extending along one side end of the current collector and being free of the active material; and vibration hammering the current collector in the preliminary uncoated region to form an uncoated region such that the current collector is characterized by an x-ray diffraction pattern in which a ratio of an FWHM of a largest peak:an FWHM of a second largest peak of the current collector in the uncoated region is greater than a ratio of an FWHM of a largest peak:an FWHM of a second largest peak of the current collector in the coated region. 
     The ratio of the FWHM of the largest peak:the FWHM of the second largest peak of the current collector in the uncoated region may be about 1.3 to about 1.6 times the ratio of the FWHM of the largest peak:the FWHM of the second largest peak of the current collector in the coated region. 
     The current collector may be characterized by an x-ray diffraction pattern in which a ratio of an FWHM of a largest peak:an FWHM of a second largest peak of the current collector in the uncoated region is about 1.4 to about 2.0. 
     The current collector may have an average thickness in the uncoated region smaller than an average thickness thereof in the coated region. The average thickness of the current collector in the uncoated region may be about 80 to about 95% of the average thickness of the current collector in the coated region. 
     The vibration hammering may include ultrasonic vibration hammering. The ultrasonic vibration hammering may include passing the preliminary uncoated region along an anvil, generating ultrasonic vibrations with an ultrasonic vibration generator, and striking the preliminary uncoated region with a horn that vibrates in response to the ultrasonic vibrations of the ultrasonic vibration generator. The anvil may have a cylindrical roller structure, and passing the preliminary uncoated region along the anvil may include rolling the preliminary uncoated region along the cylindrical roller. 
     The ultrasonic vibrations may have a frequency of about 8 to about 12 kHz, the horn may strike the preliminary uncoated region with a pressure of about 0.4 to about 0.8 MPa, and the preliminary uncoated region may be passed along the anvil at a speed of about 3 m/min to about 7 m/min. 
     The method may further include pressing the coated region between pressing rollers. Vibration hammering the current collector in the preliminary uncoated region may occur prior to pressing the coated region. Pressing the coated region may occur prior to vibration hammering the current collector in the preliminary uncoated region. The method may further include drying the active material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1  illustrates a perspective view of a rechargeable battery according to an embodiment. 
         FIG. 2  illustrates a cross-sectional view taken along line II-II of  FIG. 1 . 
         FIG. 3  illustrates a perspective view of a negative electrode according to an embodiment. 
         FIG. 4  illustrates a graph showing thicknesses of a negative coated region and a negative uncoated region according to an embodiment. 
         FIG. 5  illustrates a graph showing stretching ratios of a negative coated region and a negative uncoated region according to an embodiment. 
         FIG. 6A  illustrates a graph showing an X-ray diffraction profile of a negative uncoated region according to an embodiment. 
         FIG. 6B  illustrates a graph showing an X-ray diffraction profile of a negative coated region according to an embodiment. 
         FIG. 7  illustrates a perspective view of a positive electrode according to an embodiment. 
         FIG. 8  illustrates a diagram showing a fabricating method of an electrode according to an embodiment. 
         FIG. 9  illustrates a diagram showing a fabricating method of an electrode according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     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. 
     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 element, it can be directly on the other element, or intervening elements may also be present. In addition, 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. 
     An embodiment provides an electrode applied to a positive electrode or a negative electrode of a rechargeable battery, the electrode including: a sheet type current collector and an active material layer coated on the current collector, in which the current collector includes a coated region (where the active material layer is formed) and an uncoated region (adjacent to the coated region and free of active material). The current collector in the uncoated region may have a thickness smaller than the current collector in the coated region. 
     Another embodiment provides a fabricating method of an electrode, including: vibration-hammering a preliminary uncoated region of a current collector (that includes a coated region where an active material layer is formed and the uncoated region free of active material). 
     Yet another embodiment provides a rechargeable battery, including: an electrode assembly including a first electrode and a second electrode; a case having a space housing the electrode assembly; and a cap plate covering an opening in the case. The first electrode may include a sheet type current collector and an active material layer coated on the current collector, the current collector including a coated region where the active material layer is formed and an uncoated region adjacent to the coated region and free of the active material layer. The current collector in the uncoated region may have a thickness smaller than the current collector in the coated region. 
       FIG. 1  illustrates a perspective view of a rechargeable battery according to an embodiment.  FIG. 2  illustrates a cross-sectional view taken along line II-II of  FIG. 1 . 
     Referring to  FIGS. 1 and 2 , a rechargeable battery  101  according to an embodiment may include an electrode assembly  10  wound with a separator  13  interposed between a positive electrode (first electrode)  11  and a negative electrode (second electrode)  12 , a case  30  (in which the electrode assembly  10  is embedded or accommodated), and a cap plate  25  coupled with an opening of the case  30 . 
     The rechargeable battery  101  according to the present embodiment will be described using a lithium ion rechargeable battery having a square or hexahedral shape as an example. However, the embodiments are not limited thereto, and may be applied to various types of batteries, e.g., a lithium polymer battery, a cylindrical battery, or the like. 
       FIG. 3  illustrates a perspective view of a negative electrode according to an embodiment.  FIG. 7  illustrates a perspective view of a positive electrode according to an embodiment. 
     As shown in  FIGS. 3 and 7 , the positive electrode  11  may include a positive current collector  112  (formed of, e.g., a thin metal foil) and a positive active material layer  113  (formed on the positive current collector  112 ). The negative electrode  12  may include a negative current collector  121  and a negative active material layer  122  formed on the negative current collector  121 . 
     The positive current collector  112  may be formed in an elongated band shape and may include a positive coated region  11   b  (where the active material layer  113  is coated) and a positive uncoated region  11   a  (adjacent to the positive coated region  11   b  and free of active material). The negative current collector  121  may be formed in an elongated band shape and may include a negative coated region  12   b  (where the negative active material layer  122  is coated) and a negative uncoated region  12   a  (free of active material). 
     The positive uncoated region  11   a  may be formed on one side end of the positive current collector  112  along a lengthwise direction of the positive current collector  112 . The negative uncoated region  12   a  may be formed on another side end of the negative current collector  121  along a lengthwise direction of the negative current collector  121 . 
     The positive electrode  11  and the negative electrode  12  may be wound after a separator  13 , e.g., an insulator, is interposed therebetween. 
     However, the embodiments are not limited thereto, and the electrode assembly may have a structure in which the positive electrode and the negative electrode (formed of a plurality of sheets) are stacked with the separator interposed therebetween. 
     The case  30  may have a substantially cuboid or hexahedral shape, and an opening may be formed at one surface or side thereof. The cap assembly  20  may include a cap plate  25  (covering the opening of the case  30 ), a positive terminal  21  (protruding outside the cap plate  25  and electrically connected to the positive electrode  11 ), a negative terminal  22  (protruding outside the cap plate  25  and electrically connected to the negative electrode  12 ), and a vent member  27  (having a notch  39   a  so as to be broken in response to a predetermined internal pressure). 
     The cap plate  25  may be formed of a thin metal plate and may be fixed to the case  30  at the opening thereof by, e.g., welding. An electrolyte injection opening (for injecting an electrolyte) may be formed at one side of the cap plate  25 , and a sealing stopper  38  (that seals the electrolyte injection opening) may be fixed to the cap plate  25 . 
     The positive terminal  21  may penetrate through the cap plate  25 , and a first gasket  24  (disposed above) and a second gasket  26  (disposed below) may be installed between the cap plate  25  and the positive terminal  21  to insulate the cap plate  25  and the positive terminal  21 . 
     The positive terminal  21  may have a cylindrical shape. A nut  29  (that supports the positive terminal  21  at an upper portion thereof) may be installed in the positive terminal  21 , and a screw thread for coupling the nut  29  may be formed on an outer circumference of the positive terminal  21 . 
     The positive terminal  21  may be electrically connected to the positive uncoated region  11   a  through a current collecting member  51  and a terminal flange (that supports the positive terminal  21  and the current collecting member  51 ) may be formed at a lower end of the positive terminal  21 . Below the positive terminal  21 , a lower insulating member  41  may insulate the positive terminal  21  and the cap plate  25 . 
     The negative terminal  22  may penetrate through the cap plate  25 , and a first gasket  24  (disposed above) and a second gasket  26  (disposed below) may be installed between the cap plate  25  and the negative terminal  22  to insulate the cap plate  25  and the negative terminal  21 . 
     The negative terminal  22  may have a cylindrical shape. A nut  29  (that supports the negative terminal  22  at an upper portion thereof) may be installed in the negative terminal  22 , and a screw thread for coupling the nut  29  may be formed on an outer circumference of the negative terminal  22 . 
     The negative terminal  22  is electrically connected to the negative uncoated region  12   a  through a current collecting member  52  and a terminal flange (that supports the negative terminal  22  and the current collecting member  52 ) may be formed at a lower end of the negative terminal  22 . 
     Below the negative terminal  22 , a lower insulating member  42  may insulate the negative terminal  22  and the cap plate  25 . 
     As shown in  FIG. 3 , the negative electrode  12  may include the negative current collector  121  and the negative active material layers  122  on surfaces of the negative current collector  121 . For example, the negative current collector  121  may include a negative coated region  12   b  where active material is coated and a negative uncoated region  12   a  free of active material. 
     The negative current collector  121  may be formed of, e.g., copper or aluminum. 
     The negative current collector  121  may have a plate shape that is elongated in one direction. The negative active material layer  122  may include, e.g., Li 4 Ti 5 O 12  or a carbon-based active material, a conductive agent, a binder, or the like. The negative active material layer  122  may be coated on the negative current collector  121  and attached by a lamination method. 
     The negative uncoated region  12   a  may be stretched by hammering using vibrations. In an implementation, the negative uncoated region  12   a  may be stretched by hammering, e.g., using ultrasonic vibrations. As a result, as shown in  FIG. 4 , an average thickness of the negative current collector  121  in the negative uncoated region  12   a  may be smaller than that of the negative current collector  121  in the negative coated region  12   b . For example, the average thickness of the negative current collector  121  in the negative uncoated region  12   a  may be about 80% to about 95% of that of the negative current collector  121  in the negative coated region  12   b.    
     As shown in  FIG. 5 , when the average thickness of the negative current collector  121  in the negative uncoated region  12   a  is smaller than that of the negative current collector  121  in the negative coated region  12   b , a stretching ratio of the negative current collector  121  in the negative uncoated region  12   a  may be increased to be stretched more by a small force. Therefore, in the process of pressing the negative current collector  121  in the negative coated region  12   b , the negative current collector  121  in the negative uncoated region  12   a  may also be naturally stretched, thereby preventing the negative electrode  12  from being curved. 
       FIG. 6A  illustrates a graph showing an X-ray diffraction profile or pattern of a negative uncoated region according to an embodiment.  FIG. 6B  illustrates a graph showing an X-ray diffraction profile or pattern of a negative coated region according to an embodiment. 
       FIGS. 6A and 6B  show results of analyzing crystals of the negative current collector  121  in the negative uncoated region  12   a  and the negative coated region  12   b  by using X-ray diffraction after hammering the copper negative current collector  121  in the negative uncoated region  12   a  by using ultrasonic vibrations. 
     In the present embodiment, the negative current collector  121  made of copper is described as an example, and each FWHM (full width at half maximum) of peaks of directions  111  and  002  is exemplified. However, the embodiments are not limited thereto, and the FWHM of the peak of direction  111  may correspond to the FWHM of the maximum peak of an electrode substrate and the FWHM of the peak of direction  002  may correspond to the FWHM of the second largest peak of the electrode substrate. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 I 111/I 002 
                 Coated region 
                 Hammering-processed uncoated region 
               
               
                   
               
             
            
               
                 Sample 1 
                 1.28 
                 1.90 
               
               
                 Sample 2 
                 1.32 
                 1.87 
               
               
                 Sample 3 
                 1.23 
                 1.79 
               
               
                 Average 
                 1.28 
                 1.85 
               
               
                   
               
            
           
         
       
     
     Table 1 shows a comparison between the FWHM of the peaks of direction  111  and the FWHM of the peaks of direction  002 , shown in  FIGS. 6A and 6B  of the negative current collector  121  in the negative uncoated region  12   a  and the negative coated region  12   b.    
     In Table 1, the hammering (using ultrasonic vibrations) was performed with a frequency of 10 kHz at a pressure of 0.6 MPa and a moving speed of the negative current collector  121  was 5 m/min. 
     As shown in Table 1, an average ratio of the FWHM of the peak of direction  111  to the FWHM of the peak of direction  002  of the negative current collector  121  in the negative uncoated region  12   a  according to the present embodiment was 1.85. An average ratio of the FWHM of the peak of direction  111  to the FWHM of the peak of direction  002  of the negative current collector  121  in the negative coated region  12   b  was 1.28. 
     For example, both the FWHM&#39;s of the peaks of direction  111  and direction  002  were reduced due to the hammering using ultrasonic vibrations, but the FWHM of the peak of direction  002  was reduced to a greater degree. 
     A ratio of I  111 /I  002  (i.e., a ratio of the FWHM of the peak of direction  111  to the FWHM of the peak of direction  002  of the negative current collector  121  in the negative uncoated region  12   a ) may be about 1.4 to about 2.0. Maintaining the ratio of I  111 /I  002  at about 1.4 or greater may help ensure that the change in crystal orientation is sufficient, thereby preventing curving of the stretched negative uncoated region. Maintaining the ratio of I  111 /I  002  at about 2.0 or less may help ensure that the change in crystal orientation is not too large, thereby preventing tearing of the negative uncoated region. 
     Further, in comparing the FWHM ratios of the peaks of the negative current collector  121  in the negative uncoated region  12   a  and the negative coated region  12   b , the ratio of I  111 /I  002  of the negative current collector  121  in the negative uncoated region  12   a  may be lager than the ratio of I  111 /I  002  in the negative coated region  12   b . When the ratio of the FWHM of the maximum peak:the FWHM of the second largest peak of the negative current collector  121  in the negative uncoated region  12   a  is increased (e.g., due to a change in crystal orientation), a length of the negative current collector  121  in the negative uncoated region  12   a  may be increased, and the stretching ratio is increased in a lengthwise direction of the negative current collector  121  in the negative uncoated region  12   a , thereby preventing the negative electrode from being curved. 
     The ratio of I  111 /I  002  of the negative current collector  121  in the negative uncoated region  12   a  may be about 1.3 to about 1.6 times the ratio of I  111 /I  002  of the negative current collector  121  in the negative coated region  12   b.    
     One method of increasing the stretching ratio of the negative current collector in the uncoated region is to perform an annealing process. If the annealing is performed to increase the stretching ratio, an oxide film may be formed on a surface of the negative current collector in the uncoated region during heat treatment, leading to an undesirable increase in resistance. For example, in the case of copper, an oxide film may be easily formed due to some moisture or a rise in temperature under a general atmospheric condition. Thus, the oxide film formed as above may be eluted inside the rechargeable battery and thus may serve as a by-product during charging and discharging, which may adversely affect a cycle-life, safety, and the like. Further, in the annealing, when a substrate, e.g., an electrolytic copper foil with little internal stress, is used, a physical property thereof may not be changed and thus it may be difficult to prevent an electrode from being curved. 
     Another method of stretching the negative current collector in the uncoated region is to roll using a roller. However, when rolling with the roller, a crack may be generated due to a stretching deviation on a boundary surface between a rolled portion and a non-rolled portion. As a result, a current path may be disconnected. Furthermore, when rolling even the coated region, a mixture density may be changed and thus the active material may be eliminated. In addition, an ultra high pressure hydraulic cylinder may be required for rolling, and it may be difficult to control a pressure of the hydraulic cylinder. 
     According to the embodiments, when the hammering using ultrasonic vibrations is applied, the negative current collector in the uncoated region may be intermittently stretched by minute impact, thereby preventing the undesirable generation of a crack. In addition, the negative current collector in the uncoated region may be stretched and simultaneously, a stretching ratio of the negative current collector in the uncoated region may be increased, thereby preventing the electrode from being curved. 
     Referring to  FIG. 7 , the positive electrode  11  according to an embodiment may include the positive current collector  112  and the positive active material layer  113  on surfaces of the positive current collector  112 . For example, the positive current collector  112  may include the positive coated region  11   b  (where an active material is coated) and the positive uncoated region  11   a  (free of active material). 
     The positive current collector  112  may be formed of, e.g., aluminum, and may have a plate shape that is elongated in one direction. The positive active material layer may include, e.g., LiCoO 2 , LiMnO 2 , LiNiO 2 , or the like, a conductive agent, a binder, or the like. The positive active material layer  113  may be coated on the positive current collector  112  or may be attached by a lamination method. 
     The positive current collector  112  in the positive uncoated region  11   a  may be stretched by hammering using ultrasonic vibrations. As a result, an average thickness of the positive current collector  112  in the positive uncoated region  11   a  may be smaller than an average thickness of the positive current collector  112  in the positive coated region  11   b.    
     A thickness of the positive current collector  112  in the positive uncoated region  11   a  may be about 80% to about 95% of the thickness of the positive current collector  112  in the positive electrode coating ratio  11   b.    
     As the crystal orientation of the positive uncoated region  11   a  is changed by the hammering using ultrasonic vibration, an FWHM of a maximum peak and an FWHM of a second largest peak (according to X-ray diffraction analysis) of the positive current collector  112  in the positive uncoated region  11   a  may be smaller than an FWHM of a maximum peak and an FWHM of a second largest peak (according to the X-ray diffraction analysis) of the positive current collector  112  in the positive coated region  11   b.    
     For example, a ratio of (FWHM of maximum peak)/(FWHM of second largest peak) of the positive current collector  112  in the positive uncoated region  11   a  may be larger than a ratio of (FWHM of maximum peak):(FWHM of second largest peak) of the positive current collector  112  in the positive coated region  11   b . The ratio of (FWHM of maximum peak)/(FWHM of second largest peak) of the positive current collector  112  in the positive uncoated region  11   a  may be about 1.3 to about 1.6 times the ratio of (FWHM of maximum peak):(FWHM of second largest peak) of the positive current collector  112  in the positive coated region  11   b  due to hammering using ultrasonic vibrations. 
     When the ratio of the FWHM of the maximum peak and the FWHM of the second largest peak of the positive current collector  112  in the positive uncoated region  11   a  is increased (e.g., due to a change in crystal orientation), a length of the positive uncoated region  11   a  may be increased, and a stretching ratio may be increased in a lengthwise direction of the positive uncoated region  11   a , thereby helping to prevent the negative electrode from being curved. 
     In an implementation, in the positive current collector  112  in the positive uncoated region  11   a , the ratio of (FWHM of maximum peak)/(FWHM of second largest peak), e.g., a ratio of the FWHM of the maximum peak and the FWHM of the second largest peak of the positive current collector  112  in the positive uncoated region  11   a , may be about 1.4 to about 2.0. 
     As described above, when the positive current collector  112  in the positive uncoated region is hammered using ultrasonic vibrations, the crystal orientation of the positive current collector  112  in the positive uncoated region may be changed, thereby helping to prevent the positive electrode from being curved in the process of rolling or pressing the positive coated region. 
       FIG. 8  illustrates a diagram showing a fabricating method of an electrode according to an embodiment. 
     In  FIG. 8 , a positive electrode is described as an example, but the embodiments are not limited thereto, and a negative electrode may fabricated by the same method. 
     A fabrication method of a positive electrode according to an embodiment may include a step of forming a positive active material layer  113  on a positive current collector  112 , a step of vibration-hammering a preliminary positive uncoated region (free of the positive active material layer  113 ) to form a positive uncoated region  11   a , and a step of pressing a coated region (where the positive active material layer  113  is coated). 
     In the step of forming the positive active material layer  113 , the positive active material layer  113  may be formed on a part of the positive current collector  112  by using a coater  71  discharging an active material. The positive active material layer  113  may be simultaneously formed on both surfaces of the positive current collector  112 . Or as shown in  FIG. 8 , after the positive active material layer  113  is formed on one surface of the positive current collector  112 , the positive active material layer  113  may be sequentially formed on the other surface. 
     In the vibration-hammering step, the preliminary positive uncoated region may be hammered by using an ultrasonic vibration hammering device  60  to form the positive uncoated region  11   a . The ultrasonic vibration hammering device  60  may include an anvil  61  having a cylindrical roller structure, a horn  62  hammering the preliminary positive uncoated region, that moves on the anvil  61 , using ultrasonic vibrations, and an ultrasonic vibration generator  63  applying ultrasonic vibrations to the horn  62 . 
     The preliminary positive uncoated region may move on the rotating anvil  61  and the horn  62  may vibration-hammer the preliminary positive uncoated region vertically while vibrating at an ultrasonic wave frequency. When the positive current collector  112  moves while being hammered, hammering using ultrasonic vibrations may be continuously performed and in this process, the positive uncoated region  11   a  may be formed and stretched. 
     In an implementation, the ultrasonic vibrations may have a frequency of about 8 to about 12 kHz. In an implementation, the horn  62  may strike the preliminary uncoated region with a pressure of about 0.4 to about 0.8 MPa. In an implementation, the preliminary uncoated region may be passed along the anvil  61  at a speed of about 3 m/min to about 7 m/min. 
     In the pressing step, the positive coated region  11   b  may be pressed using pressing rollers  73  and  74  and during the pressing process, the positive coated region  11   b  may be stretched. As the positive coated region  11   b  is stretched, the positive uncoated region  11   a  may be stretched together therewith. The ultrasonic vibration hammering processed positive uncoated region  11   a  may be easily stretched even by a small force. Thus, the positive electrode may be prevented from being curved. 
       FIG. 9  illustrates a diagram showing a fabricating method of an electrode according to an embodiment. 
     Referring to  FIG. 9 , a fabricating method of an electrode according to an embodiment will be described. In the present embodiment, an electrode  15  may refer to a positive electrode or a negative electrode that are applied to a rechargeable battery. 
     The fabricating method of the electrode  15  according to the present embodiment may include a step of forming an active material layer  152  on a current collector  151 , a step of drying an electrode where the active material layer  152  is formed, a step of pressing a coated region (where the active material layer  152  is coated), and a step of vibration-hammering a preliminary uncoated region (free of the active material layer  152 ) to form the uncoated region. 
     In the step of forming the active material layer  152 , the active material layer  152  may be formed on a part of the current collector  151  by using a coater discharging an active material. The active material layer  152  may be simultaneously formed on both surfaces of the current collector  151 . Or as shown in  FIG. 9 , after the active material layer  152  is formed on one surface of the current collector  151 , the active material layer  152  may be sequentially formed on the other surface. 
     In the drying step, the electrode  15  may be moved into a drying path  75  to dry a volatile liquid remaining inside the active material layer. 
     In the pressing step, the coated region may be pressed using pressing rollers  73  and  74  and during the pressing process, the coated region may be stretched. As the coated region is stretched, tensile stress may be applied to the preliminary uncoated region. 
     In the vibration-hammering step, after the pressing step, the preliminary uncoated region may be hammered using an ultrasonic vibration hammering device  60 . The ultrasonic vibration hammering device  60  may include an anvil  61  having a cylindrical roller structure, a horn  62  hammering the preliminary uncoated region, that moves on the anvil  61 , using ultrasonic vibrations, and an ultrasonic vibration generator  63  applying ultrasonic vibrations to the horn  62 . 
     The preliminary uncoated region may move on the rotating anvil  61 , and the horn  62  may vibration-hammer the preliminary uncoated region vertically while vibrating at an ultrasonic wave frequency. When the current collector  112  moves while being hammered, hammering using ultrasonic vibrations may be continuously performed. In this process, the preliminary uncoated region may be stretched to form the uncoated region and thus tensile stress applied to the uncoated region may be removed. 
     In an implementation, the ultrasonic vibrations may have a frequency of about 8 to about 12 kHz. In an implementation, the horn  62  may strike the preliminary uncoated region with a pressure of about 0.4 to about 0.8 MPa. In an implementation, the preliminary uncoated region may be passed along the anvil  61  at a speed of about 3 m/min to about 7 m/min. 
     In the present embodiment, the vibration-hammering step may be performed after the pressing step, but the embodiments are not limited thereto. For example, the vibration-hammering step may be performed together with the pressing step. 
     By way of summation and review, after being coated with the active material, the positive electrode and the negative electrode may be pressed flatly by a press or the like. The coated region may be pressed by the press to be stretched, but the uncoated region may hardly receive any pressing force and thus may not be stretched. As described above, when stretching ratios of the coated region and the uncoated region are different from each other, the electrode may warp. If the electrode warps, an error may occur in the process of winding the electrode (that is elongated in one direction), leading to a reduction in productivity and charging and discharging efficiency. 
     The embodiments provide a rechargeable battery including an electrode in which undesirable curvature thereof is reduced and/or prevented. 
     According to an embodiment, the current collector in the uncoated region may be vibration-hammered to be stretched, and a stretching ratio of the current collector in the uncoated region may be increased, thereby preventing the electrode from warping. 
     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.