Patent Publication Number: US-11652232-B2

Title: Secondary battery and method for manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a national phase entry under 35 U.S.C. § 371 of International Patent Application No. PCT/KR2018/004366, filed on Apr. 13, 2018, published in Korean, which claims priority from Korean Patent Application Nos. 10-2017-0048645, filed on Apr. 14, 2017, and 10-2018-0043191, filed on Apr. 13, 2018, the disclosures of which are hereby incorporated herein by reference in their entireties. 
     TECHNICAL FIELD 
     The present invention relates to a secondary battery and a method for manufacturing the same, and more particularly, to a secondary battery in which an electrode tab increases in mechanical strength and a method for manufacturing the same. 
     BACKGROUND ART 
     Batteries (cells) that generate electric energy through physical or chemical reaction to supply the generated electric energy to the outside are used when AC power to be supplied to the building is not obtained, or DC power is required according to the living environments surrounded by various electric and electronic devices. 
     Among such batteries, primary batteries and secondary batteries, which are chemical batteries using chemical reaction, are being generally used. The primary batteries are consumable batteries which are collectively referred to as dry batteries. Also, secondary batteries are rechargeable batteries that are manufactured by using a material in a redox process between current and a substance is repeatable several times. When the reduction reaction is performed on the material by the current, power is charged, and when the oxidation reaction is performed on the material, power is discharged. Such the charging-discharging is repeatedly performed to generate electricity. 
     A lithium ion battery of the secondary batteries is manufactured through the following processes. An active material is applied to each of a positive electrode conductive foil and a negative electrode conductive foil at a predetermined thickness, and a separator is disposed between the positive electrode conductive foil and the negative electrode conductive foil, and then, an electrode assembly, in which the positive electrode conductive foil, the separator, and the negative electrode conductive foil are wound several times in a jelly-roll or cylindrical shape, is accommodated into a cylindrical or prismatic can, a pouch, and the like to seal the resultant product, thereby manufacturing the lithium ion battery. 
     An electrode assembly and a secondary battery including the same according to the related art is disclosed in Korea Patent Publication No. 10-2012-0006389. 
     In the secondary battery according to the related art, it is necessary to apply a technology in which a metal having low resistance is applied to a negative electrode tab, or the number of electrode tabs increases in order to develop a low resistance cell. 
     A negative multi-tab structure developed by this necessity was a two-tab structure in which an electrode tab is attached to each of a core and an outer portion or a three-tab structure in which an electrode tab is applied to each of a core and an outer portion, and a middle tab is attached to an intermediate portion. 
     However, in order to attach the middle tab on the characteristics of the jelly roll, a non-coating portion has to be formed on a predetermined portion in the middle of the electrode. Thus, there is a problem that the battery capacity is lowered due to an increase of the non-coating portion. 
     DISCLOSURE OF THE INVENTION 
     Technical Problem 
     Therefore, the present invention has been made to solve the abovementioned problem, and an object of the prevent invention is to provide a secondary battery in which a multi-tab is formed while minimizing a non-coating portion and a method for manufacturing the same. 
     Also, an object of the present invention is to provide a secondary battery which is capable of increasing in mechanical strength while notching electrode foil to form an electrode tab and a method for manufacturing the same. 
     Technical Solution 
     A secondary battery according to an embodiment of the present invention includes: an electrode provided with a coating portion coated with an active material on an electrode collector and a non-coating portion on which the active material is not applied to the electrode collector in a longitudinal direction of the electrode collector; and a notching tab part extending from the coating portion in a width direction of the electrode collector perpendicular to the longitudinal direction and not coated with the active material, the notching tab part having a wound state including two or more overlapping layers when the electrode is in a wound state. 
     The notching tab part may continuously extend across ⅓ or more of a total length of the coating portion in the longitudinal direction. 
     When the electrode is in the wound state, the notching tab part may form a plurality of notching tabs. 
     The foil tab may have a width of 4 mm to 120 mm. 
     The electrode may be accommodated in a can member, and each of the plurality of notching tabs may be in a bent state and may be connected to the can member. 
     A bent part formed by bending each of the plurality of notching tabs may be bonded to the can member. 
     The secondary battery may further include an insulation member disposed between the bent parts and an end of the electrode. 
     The secondary battery may further include an electrode tab attached to the non-coating portion. 
     When the electrode is in the wound state, the notching tab part may form a plurality of notching tabs, and the electrode may be accommodated in a can member, and each of the plurality of notching tabs may be in a bent state and may overlap the electrode tab. 
     The electrode tab and the plurality of notching tabs may be bonded together to the can member. 
     A method for manufacturing a secondary battery according to an embodiment of the present invention includes: a preparation step of preparing an electrode provided with a coating portion coated with an active material on an electrode collector and a non-coating portion on which the active material is not applied to the electrode collector in a longitudinal direction of the electrode collector; a notching tab part formation step of notching the electrode to form a notching tab part not coated with the active material and extending from the coating portion in a width direction of the electrode collector perpendicular to the longitudinal direction, the notching tab part extending across ⅓ or more of a total length of the coating portion in the longitudinal direction; a winding step including stacking the electrode with a separator and with another electrode having a polarity different from that of the electrode and winding the electrode, the separator, and the another electrode to form an electrode assembly; a notching tab formation step of cutting the notching tab part of the electrode assembly to form a plurality of notching tabs; and an installation step of accommodating the electrode assembly into a can member and bonding each of the plurality of notching tabs to the can member. 
     The electrode may be a negative electrode. 
     During the preparation step, the coating portion coated with the active material on the electrode collector and the non-coating portion on which the active material is not applied may be arranged in parallel to each other in the width direction of the electrode collector. 
     during the notching tab part formation step, the notching tab part on which the active material is not applied may be notched in the width direction of the coating portion while cutting the coating portion and the non-coating portion in the longitudinal direction of the electrode collector. 
     During the notching tab part formation step, notching may be performed so that the notching tab part on which the active material is not applied is notched in the width direction of the coating portion while cutting the electrode. 
     During the notching tab formation step, the notching tab part may be cut using a laser. 
     During the installation step, the electrode assembly may be accommodated in the can member in a state in which the plurality of notching tabs are bent and bonded to the can member. 
     During the installation step, a bent portion of each of the plurality of notching tabs may be welded to the can member. 
     During the installation step, bent portions of each of the plurality of notching tabs may overlap each other and may be bonded to the can member together. 
     During the winding step, the notching tab part may be wound to form two or more overlapping layers. 
     Advantageous Effects 
     According to the present invention, the multi-tab may be formed while minimizing the formation of the non-coating portion. 
     According to the present invention, the multi-tab may be formed to minimize the electric resistance. 
     According to the present invention, the formation of the non-coating part may be minimized to secure the battery capacity. 
     According to the present invention, the notching tab may overlap each other to form two or more layers while forming the notching tab that is the foil tab from the electrode foil, whereby increasing in mechanical strength. 
     According to the present invention, the notching tab that is the foil tab may increase in mechanical strength to prevent the notching tab from being broken in the bent state, and thus, the notching tab may be boned to the can member in the bent state to secure the reliability in electrical connection and improve the bonding performance. 
     According to the present invention, the notching tab and the electrode tab may be bonded to the can member at the same to secure the welding processability. 
     According to the present invention, the plurality of notching tabs may be formed outside the electrode assembly to install the insulation member between the plurality of notching tabs and the end of the electrode assembly, and thereby to prevent the notching tabs and the electrode assembly from coming into contact with each other, thereby improving the safety. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a development view of an electrode according to an embodiment of the present invention. 
         FIG.  2    is a perspective view illustrating a state in which the electrode of  FIG.  1    is wound. 
         FIG.  3    is a perspective view illustrating a state in which a notching tab part is cut to form a notching tab in  FIG.  2   . 
         FIG.  4    is a projective perspective view when seeing through a can member in a state in which an electrode assembly is installed in the can member according to an embodiment of the present invention. 
         FIG.  5    is a bottom view of only the electrode assembly in  FIG.  4   . 
         FIG.  6    is a flowchart successively illustrating a method for manufacturing a secondary battery according to an embodiment of the present invention. 
         FIG.  7    is a plan view illustrating a state in which a coating portion and a non-coating portion, which are formed in a longitudinal direction of an electrode collector, are arranged in parallel to each other in a width direction of the electrode collector according to an embodiment of the present invention. 
         FIG.  8    is a bottom view illustrating a state in which a notching tab and an electrode tab are bonded to each other according to another embodiment of the present invention. 
         FIG.  9    is a side view of  FIG.  8   . 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, a secondary battery and a method for manufacturing the same according to exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
     Terms or words used in the specification and claims should not be construed as limited to a lexical meaning, and should be understood as appropriate notions by the inventor based on that he/she is able to define terms to describe his/her invention in the best way to be seen by others. Therefore, embodiments and drawings described herein are simply exemplary and not exhaustive, and it will be understood that various equivalents may be made to take the place of the embodiments. 
     In the drawings, the dimension of each of components or a specific portion constituting the component is exaggerated, omitted, or schematically illustrated for convenience in description and clarity. Thus, the dimension of each element does not entirely reflect an actual size. Moreover, detailed descriptions related to well-known functions or configurations will be ruled out in order not to unnecessarily obscure subject matters of the present invention. 
       FIG.  1    is a development view of an electrode according to an embodiment of the present invention, and  FIG.  2    is a perspective view illustrating a state in which the electrode of  FIG.  1    is wound. 
     As illustrated in  FIGS.  1  and  2   , a secondary battery according to an embodiment of the present invention includes an electrode on which a coating portion  110  coated with an active material a on an electrode collector and a non-coating portion  120 , on which the active material a is not applied on the electrode collector, are disposed in a longitudinal direction of the electrode collector and a notching tab part  111  extending from the coating portion  110  in a width direction of the electrode collector without being coated with the active material a and overlapping each other to form two or more layers when the electrode  100  is wound ( FIG.  2    illustrates a notching tab part  111  that overlap each other to form two or more layers). 
     The foil tab may overlap each other to form two or more layers while forming the notching tab part that is a foil tab from electrode foil of the electrode collector, thereby increasing in mechanical strength. 
     The electrode  100  may be one of a positive electrode coated with a positive electrode active material and a negative electrode coated with a negative electrode active material. The electrode assembly  1  may be manufactured by stacking the positive electrode, the negative electrode, and a separator several times so that the separator is disposed between the positive electrode and the negative electrode. 
     Also, the electrode assembly  1  may be manufactured by winding a stack, in which the positive electrode, the separator, and the negative electrode are stacked, in a jelly-roll shape. 
     The positive electrode may be an aluminum electrode collector and include a positive electrode coating portion coated with the positive electrode active material and a positive electrode non-coating portion which is not coated with the positive electrode active material. 
     The positive electrode active material may include a lithium-containing transition metal oxide such as LiCoO 2 , LiNiO 2 , LiMnO 2 , and LiMnO 4  or a lithium chalcogenide compound. 
     The positive electrode coating portion may be manufactured, for example, by applying the positive electrode active material to a portion of at least one surface of the aluminum electrode collector, and the remaining portion of the aluminum electrode collector, which is not coated with the positive electrode active material, may be the positive electrode non-coating portion. 
     The negative electrode may be a copper electrode collector and include a negative electrode coating portion coated with the negative electrode active material and a negative electrode non-coating portion which is not coated with the negative electrode active material. 
     The negative electrode active material may be a carbon material such as crystalline carbon, amorphous carbon, a carbon composite, and a carbon fiber, a lithium metal, or a lithium alloy. 
     The negative electrode coating portion may be manufactured, for example, by applying the negative electrode active material to a portion of at least one surface of the copper electrode collector, and the remaining portion of the copper electrode collector, which is not coated with the negative electrode active material, may be the negative electrode non-coating portion. 
     The separator may be manufactured by applying a polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP co-polymer) to one base material selected from the group consisting of, for example, polyethylene (PE), polystyrene (PS), polypropylene (PP), and a copolymer of polyethylene (PE) and polypropylene. 
     As described above, the electrode  100  according to the present invention may be one of the positive electrode and the negative electrode, which constitute the electrode assembly  1 . Particularly, the electrode  100  may be one, which requires further reduction in resistance, of the positive electrode and the negative electrode. 
     In the present invention, the negative electrode will be described as an example. 
     The electrode  100  has one end on which the non-coating portion  120  is formed. An electrode tab  121  may be attached to the non-coating portion  120  formed on the one end of the electrode  100 . 
     The notching tab part  111  may be formed by notching the electrode  100  to extend from the coating portion  110  of the electrode  100  in the width direction. Only the electrode collector may be formed to extend on an area corresponding to ⅓ or more of the total length of the coating portion  110  of the electrode  100 , and the active material a may not be applied. 
     Only the active material a may be removed from the coating portion  110  extending from the electrode  100  to form the notching tab part  111 . Alternatively, only the electrode foil may extend without applying the active material a on the area of the coating portion  110  of the electrode  100  to form the notching tab part  111 . 
     Thus, there may be an effect of forming the multi-tab while minimizing the formation of the non-coating portion, and the formation of the non-coating portion may be minimized to secure the battery capacity. 
       FIG.  3    is a perspective view illustrating a state in which the notching tab part is cut to form the notching tab in  FIG.  2   . 
     As illustrated in  FIG.  3   , the notching tab part  111  may be cut in the wound state to form a plurality of notching tabs  111   a . When the number of notching tabs  111   a  increases, the electrode tab may decrease in resistance. 
     Here, one notching tab  111   a  may have a width of 4 mm to 5 mm. This is done for a reason in which, if the notching tab  111   a  has a width that is less than 4 mm, the mechanical strength may be weakened, and if the notching tab  111   a  has a width exceeding 5 mm, deformation in the process of bonding for the electrical connection with the can member may be difficult. 
     The notching tab  111   a  that is the foil tab may increase in mechanical strength to prevent the notching tab  111   a  from being broken in the bent state, and thus, the notching tab  111   a  may be bonded to the can member in the bent state to secure the reliability in electrical connection and improve the bonding performance. 
       FIG.  4    is a projective perspective view when seeing through the can member in a state in which the electrode assembly is installed in the can member according to an embodiment of the present invention, and  FIG.  5    is a bottom view of only the electrode assembly in  FIG.  4   . 
     As illustrated in  FIGS.  4  and  5   , in the electrode assembly  1  of the secondary battery according to the present invention, a bent part of the notching tab  111   a  may be welded to be coupled to the can member  10  so that the notching tab  111   a  is electrically connected to the can member  10  in a state in which the notching tab  111   a  is bent while being accommodated in the can member  10 . 
     The notching tab  111   a  may be bent to allow an end of the notching tab  111   a  to be coupled to a center of a bottom surface of the can member  10 . Thus, the plurality of notching tabs  111   a  may be electrically connected to each other while the electrical connection is smooth to minimize the electric resistance. 
       FIG.  8    is a bottom view illustrating a state in which a notching tab and an electrode tab are bonded to each other according to another embodiment of the present invention, and  FIG.  9    is a side view of  FIG.  8   . 
     As illustrated in  FIGS.  8  and  9   , in a secondary battery according to another embodiment of the present invention, a notching tab part  111  of an electrode assembly  1 , in which an electrode  100  is wound, may be cut to form a plurality of notching tabs  111   a . The plurality of notching tabs  111   a  may be bent and then be connected to overlap an electrode tab  121  formed on a central portion of an end of the electrode assembly  1 . 
     Also, the electrode assembly  1  may be accommodated in a can member  10 , and the plurality of notching tabs  111   a  connected to overlap the electrode tab  121  may be bonded to the can member  10  together with the electrode tab  121  through welding. 
     As described above, in the secondary battery according to another embodiment of the present invention, since the plurality of notching tabs  111   a  and the electrode tab  121  are welded together to the can member  10  in the state in which the notching tabs  111   a  and the electrode tab  121  are connected to overlap each other, welding processability may be easily secured. 
     In the secondary battery according to another embodiment of the present invention, when an end of the electrode assembly  1  has a length ranging of 16 mm to 21 mm, a notching length of each of the plurality of notching tabs  111   a  may range of 8 mm to 11 mm. When the notching length of the notching tab  111   a  is less than 8 mm, the length of the notching tab  111   a  may be shortened, and the notching tab  111   a  may be bent. Thus, it may be difficult to allow the notching tab  111   a  to overlap the electrode tab  121  formed on a central portion of an end of the electrode assembly  1 . Also, when the notching length of the notching tab  111   a  exceeds 11 mm, the length of the notching tab  111   a  may be unnecessarily lengthened to increase in cost due to waste of the material and in space occupied by the notching tab  111   a  within the can member  10 . Thus, an amount of electrolyte filled into the can member  10  may be reduced to deteriorate capacity. Preferably, the notching tab  111   a  may have a notching length of 9 mm to 10 mm. 
     In the secondary battery according to another embodiment of the present invention, an insulation member  130  may be formed between a bent part of the notching tab  111   a  and an end of the electrode assembly  1  in which the electrode  100  is wound. 
     The insulation member  130  may insulate the notching tab  111   a  from the end of the electrode assembly  1  to prevent the notching tab  111   a  from coming into contact with the electrode assembly  1 . 
     The plurality of notching tabs  111   a  may be formed on an outer portion of the end of the electrode assembly to prevent the insulation member  130  from interfering with the end of the electrode assembly  1 . 
     The plurality of notching tabs  111   a  may be formed on the outside of the electrode assembly so that the insulation member  130  is installed between the plurality of notching tabs  111   a  and the end of the electrode assembly  1 . Thus, the contact between the notching tab  111   a  and the electrode assembly  1  may be prevented to improve safety. 
     Hereinafter, a method of manufacturing a secondary battery according an embodiment of the present invention will be described in detail with reference to the accompanying drawings. 
       FIG.  6    is a flowchart successively illustrating a method for manufacturing a secondary battery according to an embodiment of the present invention. 
     As illustrated in  FIG.  6   , a method for manufacturing a secondary battery according to an embodiment of the present invention includes a preparation step (S 1 ), a notching tab part formation step (S 2 ), a winding step (s 3 ), a notching tab formation step (S 4 ), and an installation step (S 5 ). 
     The preparation step (S 1 ) is a step of preparing an electrode  100  in which a coating portion  110  coated with an active material a on an electrode collector and a non-coating portion  120  on which the active material a is not applied are provided in a longitudinal direction of the electrode collector. 
     Here, the electrode  100  may be a negative electrode. 
       FIG.  7    is a plan view illustrating a state in which the coating portion and the non-coating portion, which are formed in the longitudinal direction of the electrode collector, are arranged in parallel to each other in a width direction of the electrode collector according to an embodiment of the present invention. 
     As illustrated in  FIG.  7   , in the preparation step (S 1 ), the coating portion  110  and the non-coating portion  120 , which are formed in a longitudinal direction L of the electrode collector may be arranged in parallel to each other in the width direction W of the electrode collector. 
     In the notching tab part formation step (S 2 ) is a step of notching the electrode  10  to form a notching tab part  111  extending in a state in which the active material is not formed in the width direction W of the coating portion  111  on an area of the electrode  100  corresponding to ⅓ or more of a length of the coating portion  110 . 
     As described above, the notching of the notching tab part  111  in the electrode  100  may a step of notching a portion of the non-coating portion on which the active material a is not applied and which is formed in the width direction W of the coating portion  11  while cutting the electrode  100  in the electrode collector to form a notch tab part  11 . 
     Also, when the coating portion  100  and the non-coating portion  120 , which are formed in the longitudinal direction L of the electrode collector, are arranged in parallel to each other in the width direction W of the electrode collector, the non-coating portion on which the active material is not applied and which is formed between one coating portion  110  and the other coating portion  110   a , which are arranged in parallel to each other in the width direction W may be notched while cutting the coating portion  110  and the non-coating portion  120 , which are arranged in parallel to each other to form the notching tab part  111  in the width direction W of the coating portion  110 . 
     The winding step (S 3 ) may be a step of stacking the electrode  100 , on which the notching tab part  111  is formed, on the separator and the other electrode having a polarity different from that of the electrode  100  and winding the stack to form the electrode assembly  1 . 
     While the electrode  100  is wound, the notching tab part  111  may overlap each other to form two or more layers. 
     The notching tab formation step (S 4 ) may be a step of cutting the notching tab part  111  to form a plurality of notching tabs  111   a.    
     The notching tabs  111   a  formed by cutting the notching tab part  111  may overlap each other to two or more layers like the notching tab part  111 . 
     Here, the cutting of the notching tab part  111  may be maximized in work efficiency by using laser. 
     The insulation step (S 5 ) may be a step of accommodating the electrode assembly  1  into the can member  10  to bond the notching tabs  111   a  to the can member  10 . 
     In the installation step (S 5 ), each of the notching tab  111   a  may be bent so that the welding is easily performed while the notching tab  111   a  is electrically connected to the can member  10  to allow the electrode assembly  1  to be accommodated in the can member  10  in the state in which the notching tab  111   a  is bent. 
     Here, since the notching tab  111   a  has the two or more layers, even though the notching tab  111   a  is bent, mechanical strength may be maintained, and thus, the notching tab may not be easily broken. 
     The bent notching tab  111   a  may have an end that faces a center of a bottom surface of the can member  10 . 
     The coupling between the bottom surface of the can member  10  and the notching tab  111   a  may be performed by welding the bent part of the notching tab  111   a  to the bottom surface of the can member  10 . 
     In addition, according to another embodiment of the present invention, the bent portions of the plurality of notching tabs  111   a  may overlap the central portion of the end of the electrode assembly  1  so as to be welded and bonded to the can member  10  together with the electrode tab  121  formed on the central portion of the end of the electrode  1  at the same time. 
     Although the secondary battery and the method for manufacturing the same according to the present invention has been described above with reference to the exemplary drawings, various changes and modifications may be made thereto by one skilled in the art without departing from the scope and spirit of the invention as set forth in the appended claims.