Abstract:
An electrode assembly according to an embodiment of the present invention comprises: at least one first electrode plate comprising a first electrode tab extending from the first electrode plate; at least one second electrode plate comprising a second electrode tab extending from the second electrode plate; at least one first intermediate electrode comprising a first intermediate electrode tab extending from the first intermediate electrode; at least one second intermediate electrode comprising a second intermediate electrode tab extending from the second intermediate electrode; and a separator disposed between the first electrode plate and the second electrode plate, and a separator disposed between the first intermediate electrode and the second intermediate electrode; wherein the first electrode plate is disposed at an outermost side in the electrode assembly with respect to the first intermediate electrode, and the second electrode plate is disposed at an outermost side in the electrode assembly with respect to the second intermediate electrode; and wherein the first electrode tab and the first intermediate electrode tab together constitute a first electrode lead, and the second electrode tab and the second intermediate electrode tab together constitute a second electrode lead.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/310,603, filed on Mar. 4, 2010, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     1. Field 
     An embodiment of the present invention relates to an electrode assembly and a secondary battery using the same, and more particularly, to an electrode assembly and a secondary battery using the same that are capable of simplifying a process and saving cost by modifying the form of an electrode tab of an outermost substrate among electrode plates. 
     2. Description of the Related Technology 
     As portable electronic apparatuses are being miniaturized and lightened, research has been conducted into secondary batteries in their use as driving power sources. As the decreasing weight and functionality of portable wireless device products, including cellular phones, notebook computers, personal digital assistants (PDAs), etc. progress, the importance of the secondary battery in its use as a driving power source for such products is remarkably emphasized. 
     Since the secondary battery can be repeatedly used through the repetition of charging and discharging, the secondary battery is more economical than a primary battery. Moreover, since the miniaturization and the high capacity of the secondary battery can be utilized, and the secondary battery has high operating voltage and high energy density per weight, the secondary battery is being widely used in high-tech electronic devices. 
     In particular, the lithium secondary battery, which typically has an operating voltage of 3.7V, is three times higher than the nickel-cadmium battery or the nickel-hydride battery which are primarily used as power sources for portable electronic equipments. 
     In general, the demand for certain secondary batteries, such as a can-type battery or a pouch-type battery having a small thickness that can be used with a cellular phone is high with respect to shape, and the demand for a secondary battery such as a lithium polymer battery having excellent energy density, discharge voltage, and safety is high with respect to material. 
     In the can-type or pouch-type battery, an electrode assembly, electrode tabs extending from the electrode assembly, and electrode leads welded to the electrode tabs are typically accommodated in a can or a pouch. The electrode assembly also typically has a structure in which an anode plate, a cathode plate, and a separator that is interposed therebetween and insulates them from each other are sequentially laminated or wound. 
     In addition, the electrode tabs typically are individually extended and fused from the anode plate and the cathode plate of the electrode assembly, and the electrode tabs typically are electrically connected with each of anode and cathode electrode leads and a part of each electrode tab is typically exposed outside the can or pouch. The exposed electrode lead is typically electrically connected with a protection circuit module in a subsequent process. 
     However, as such, the electrode tabs extending from each of the anode plate and the cathode plate of the electrode assembly are fused and thereafter, when each of the electrode tabs is connected with the electrode lead, the manufacturing process can become complicated and the electrode tab and the electrode lead may become separated from each other while the subsequent process is performed. 
     SUMMARY 
     According to an embodiment of the present invention, an electrode assembly comprises: at least one first electrode plate comprising a first electrode tab extending from the first electrode plate; at least one second electrode plate comprising a second electrode tab extending from the second electrode plate; at least one first intermediate electrode comprising a first intermediate electrode tab extending from the first intermediate electrode; at least one second intermediate electrode comprising a second intermediate electrode tab extending from the second intermediate electrode; and a separator disposed between the first electrode plate and the second electrode plate, and a separator disposed between the first intermediate electrode and the second intermediate electrode; wherein the first electrode plate is disposed at an outermost side in the electrode assembly with respect to the first intermediate electrode, and the second electrode plate is disposed at an outermost side in the electrode assembly with respect to the second intermediate electrode; and wherein the first electrode tab and the first intermediate electrode tab together constitute a first electrode lead, and the second electrode tab and the second intermediate electrode tab together constitute a second electrode lead. 
     According to an embodiment, the first electrode tab covers the first intermediate electrode tab, and the second electrode tab covers the second intermediate electrode tab. 
     According to an embodiment, the first electrode plate and the first electrode tab are thicker than the first intermediate electrode and the first intermediate electrode tab, respectively, and the second electrode plate and the second electrode tab are thicker than the second intermediate electrode and the second intermediate electrode tab, respectively. 
     According to an embodiment, the at least one first electrode plate and the at least one first electrode tab and the at least one second electrode plate and the at least one second electrode tab has a thickness in the range of 50 to 100 μm. 
     According to an embodiment, the first electrode tab and the second electrode tab each has a width in the range of 5 to 40 mm. 
     According to an embodiment, the at least one first electrode tab and the at least one second electrode tab each has a length that is 150% to 200% of the length of the at least one first intermediate electrode tab and the at least one second intermediate electrode tab. 
     According to an embodiment, the pair of first electrode tabs and the at least one intermediate electrode tab is coupled to each other by welding, and the pair of second electrode tabs and the at least one second intermediate electrode tab is coupled to each other by welding. 
     According to an embodiment, an insulating tape is coupled to portions of the first electrode tab and the second electrode tab. 
     According to an embodiment, a secondary battery may be manufactured comprising the above-mentioned electrode assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, with the specification, illustrate certain embodiments of the present invention, and serve to explain the principles of embodiments of the present invention. 
         FIG. 1  is a perspective view showing a state in which an electrode assembly in a pouch case is disassembled according to an embodiment of the present invention. 
         FIG. 2  is a perspective view of a secondary battery according to an embodiment of the present invention. 
         FIG. 3  is a cross-sectional view taken along line A-A′ of  FIG. 2 . 
         FIG. 4  is a cross-sectional schematic view taken along line B-B′ of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In the following detailed description, only certain embodiments of the present invention have been shown and described, by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. In addition, when an element is referred to as being “on” another element, it can be directly on the another element or indirectly on the another element with one or more intervening elements interposed therebetween. Also, when an element is referred to as being “connected to” another element, it can be directly connected to another element or indirectly connected to another element with one or more intervening elements interposed therebetween. Hereinafter, like reference numerals refer to like elements. 
     An electrode assembly and a secondary battery using the same according to an embodiment of the present invention will now be described in detail with reference to the accompanying drawings illustrating embodiments of the present invention. 
       FIG. 1  is a perspective view showing a state in which an electrode assembly in a pouch case is disassembled according to an embodiment of the present invention. 
     Referring to  FIG. 1 , an electrode assembly  10  includes an anode plate  54  and a cathode plate  44  to which an active material is applied and a separator  60  interposed therebetween is laminated. Anode tabs  55  that extend from one side may be formed on the anode plate  54  and cathode tabs  45  that extend from the other side in the same direction as the anode tabs  55  may be formed on the cathode plate  44 . The anode plate  54  and the cathode plate  44  may include a pair of outermost anode plates  51  and a pair of outermost cathode plates  41  positioned at the outermost portion, and a plurality of intermediate anode plates  53  and a plurality of intermediate cathode plates  43  interposed therebetween. 
     In the embodiment illustrated in  FIG. 1 , the outermost anode plate  51  is an anode plate  51  positioned at the outermost portion among the laminated anode plates  54  and the outermost cathode plate  41  is a cathode plate  41  positioned at the outermost portion among the laminated cathode plates  44 . At this time, any one pair of outermost anode plates  51  or pair of outermost cathode plate  41  may actually be the outermost portion of the electrode assembly  10 , but in the present embodiment, a pair of outermost anode plates  51  is formed at the outermost portion of the electrode assembly  10 . 
     The outermost anode plate  51  may be thicker than the intermediate anode plate  53 , and the outermost anode tab  50  may be larger than the intermediate anode tab  52 . By this configuration, the outermost anode tab  50  can tie the intermediate anode tabs  52  of the intermediate anode plates  53  and in addition, the outermost anode tab  50  itself can serve as the electrode lead without additionally attaching an electrode lead electrically connected with a protection circuit module (not shown) at the time of forming a core pack. 
     In general, the thickness of the intermediate anode plate  53  may be in the range of 12 to 30 μm and in the embodiment of the present invention, the thickness of the outermost anode plate  51  covering the intermediate anode plate  53  may be in the range of 50 to 100 μm. That is, when the outermost anode tab  50  attached to the outermost anode plate  51  has a thickness less than 50 μm, the outermost anode tab  50  can have the thickness equal to or smaller than the intermediate anode tabs  52 , such that the strength of the outermost substrate can deteriorate. In addition, when the outermost anode tab  50  has a thickness more than 100 μm, the outermost substrate can become excessively thicker, such that inter-attachment is not easy and in addition, the secondary battery becomes thicker. 
     Further, the outermost cathode tab  40  may also like the outermost anode tab  50  be thicker than the intermediate cathode tabs  42 . In general, the thickness of the intermediate cathode plate  43  may be in the range of 8 to 20 μm and the thickness of the outermost cathode plate  41  covering the intermediate cathode plate  43  may be in the range of 50 to 100 μm. Herein, the outermost cathode tab  40  and the intermediate cathode tabs  42  may extend in the same direction as the outermost anode tab  50  and the intermediate anode tabs  52 , but to the other side so as to not overlap with the outermost anode tab  50  and the intermediate anode tabs  52  that extend to one side. 
     The anode plate  54  and the cathode plate  44  are generally formed by applying and filling the active material to and into a metallic substrate, and drying, roll-pressing, and cutting, but may be differently formed depending on the type of secondary battery. The anode plate  54  and the cathode plate  44  may be fabricated by coating an aluminum metal foil and a copper metal foil with slurries and subsequent drying. The slurries may include the active materials of the anode plate  54  and the cathode plate  44 , and a fixing agent that allows the active materials to adhere to the metal foils. For a lithium secondary battery, an oxide containing lithium may be primarily used as an anode active material and any one of hard carbon, soft carbon, graphite, and a carbon substance may primarily be used as a cathode active material, but the present invention is not limited to the lithium secondary battery. 
     The separator  60  may be interposed between the anode plate  54  and the cathode plate  44 . An insulating thin film having high ion permeability and high mechanical strength may be used. Diameters of pores of the separator  60  may generally be in the range of 0.01 to 10 μm and thicknesses thereof may generally be in the range of 5 to 300 μm. A sheet or a non-woven fabric made of an olefinic polymer, such as chemical-resistant and hydrophobic polypropylene, a glass fiber, or polyethylene, may be used as the separator  60 , for example. According to embodiments, a solid electrolyte, such as polymers, etc., may also serve as the separator  60 . 
     In addition, a pouch case  20  may have a receiving space that can house the electrode assembly  10 . The pouch case  20  may generally be formed on the top and on the bottom of an aluminum thin film to form a laminate structure. An inner surface of the pouch case  20  may be made of a heat adhesive resin. 
       FIG. 2  is a perspective view of a secondary battery according to an embodiment of the present invention. 
     Referring to  FIG. 2 , when the electrode assembly  10  is received in the receiving space of the pouch case  20 , a pair of outermost anode tabs  50  and a pair of outermost cathode tabs  40  may be partially exposed outside the pouch case  20 . An insulating tape  70  that insures electrical insulation while increasing the airtight seal within the pouch case  20  may be attached to the outermost electrode tabs  40  and  50  that are in contact with the pouch case  20 . 
     As described above, the pouch case  20  may be generally fanned on the top and on the bottom of the aluminum thin film to form a laminate structure covered with nylon, or a synthetic resin such as polypropylene or polyethylene, etc. The inner surface of the pouch case  20  may be made of the heat adhesive resin to provide an airtight seal. As a result, the heat adhesive resin coated on the inner surface of the pouch case  20  may be inter-fused by heating and pressing to make the pouch case  20  airtight. 
     Since a pair of outermost anode tabs  50  and a pair of outermost cathode tabs  40  may be partially exposed outside the pouch case  20  while tying the intermediate anode tabs  52  and the intermediate cathode tabs  42  positioned therein to serve as the electrode lead, they would have a size that is large enough to cover the intermediate anode tabs  52  and the intermediate cathode tabs  42 . 
     Preferably, the widths of the outermost anode tab  50  and the outermost cathode tab  40  are in the range of 5 to 40 mm. Since the widths of the intermediate anode tab  52  and cathode tabs  42  are in the range of 4 to 7 mm according to embodiments, the widths of the outermost anode tab  50  and the outermost cathode tab  40  are preferably in the range of 5 to 40 mm to be large enough to cover the intermediate anode and cathode tabs. Further, the lengths of the outermost anode tab  50  and the outermost cathode tab  40  should be 150% to 200% of the lengths of the intermediate anode tab  52  and the intermediate cathode tab  42 , respectively. 
     When the lengths of the outermost anode tab  50  and the outermost cathode tab  40  are formed to be less than 150% to 200% of the lengths of the intermediate anode tab  52  and the intermediate cathode tab  42 , respectively, they may not be large enough to sufficiently cover the intermediate anode tab  52  and the intermediate cathode tab  42 . In addition, when the lengths of the outermost anode tab  50  and the outermost cathode tab  40  are more than 200% of the lengths of the intermediate anode tab  52  and the intermediate cathode tab  42 , respectively, unnecessary portions of the outermost anode tab  50  and cathode tab  40  positioned inside or outside the pouch case may occupy additional space. 
     According to an embodiment, a pair of outermost anode tabs  50  and a pair of outermost cathode tabs  40  may be attached by laser welding. By this configuration, since the outermost anode tab  50  and the outermost cathode tab  40  can cover the intermediate anode tabs  52  and the intermediate cathode tabs  42  interposed therebetween and be partially exposed outside the pouch case  20 , the outermost anode tab  50  and the outermost cathode tab  40  may serve as the electrode lead. 
       FIG. 3  is a cross-sectional view taken along line A-A′ of  FIG. 2 . 
     Referring to  FIG. 3 , in the electrode assembly  10  positioned in the pouch case  20 , the anode plate  54 , the separator  60 , and the cathode plate  44  may be sequentially laminated. The cathode plate  44  may be slightly larger than the anode plate  54  and the separator  60  may be slightly larger than the cathode plate  44  and interposed between the anode plate  54  and the cathode plate  44 . That is, the anode plate  54 , the cathode plate  44 , and the separator  60  may be formed according to size. In general, the separator  60  of the laminate-type electrode assembly  10  may be fabricated larger than the anode plate  54  and the cathode plate  44  in order to prevent a short-circuit that may be caused by contact between the anode plate  54  and the cathode plate  44 . Further, the anode plate  54  may be fabricated to be slightly smaller than the cathode plate  44  in consideration of a lithium ion precipitation phenomenon that is intermittently generated in the cathode plate  44  at the time of charging. 
     The lamination form of the electrode assembly  10  will now be described in more detail. The anode plate  56  may be positioned at the center of the electrode assembly  10 . The anode plates  51  may be positioned evenly at both outermost portions of the electrode assembly  10  and may be vertically symmetric to each other with respect to the central anode plate  56 . That is, the electrode assembly  10  may have a structure in which the separator  60  is laminated at both sides of the central anode plate  56 , the intermediate cathode plates  43  are laminated at both sides of the separator  60 , and the intermediate anode plates  53  are positioned at both sides of the intermediate cathode plate  43 , and such a configuration is repeated. 
     In addition, an active material (not shown) may be applied to the anode plate  56  positioned at the center of the electrode assembly  10 , and both surfaces of the internal intermediate anode plates  53  and the internal intermediate cathode plates  43  and the active material may be applied to only the inner surface of the outermost anode plate  51 . 
     In the electrode assembly  10  having the above-mentioned lamination structure, a pair of outermost anode plate  51  can be thicker than the intermediate anode electrodes  53 , and the outermost anode tab  50  can have a larger width and a larger length. Therefore, the outermost plate may serves as the electrode lead while covering and tying the intermediate anode tabs  52 . 
     According to an embodiment, the insulating tape  70  is attached to a portion where the outermost anode tab  50  is exposed outside and in contact with an airtight pouch case  20 . That is, when the pouch case  20  is airtight, the insulating tape  70  that insulates the pouch case  20  and the outermost anode tab  50  from each other may be included. When the heat adhesive resin is fused onto the inner surface of the pouch case  20 , the insulating tape  70  can prevent a short-circuit of the outermost electrode tabs  40  and  50  and the aluminum thin film. Meanwhile, the insulating tape  70  should not hinder the airtight state of the pouch case  20  and should not serve as a route for permeation of moisture or outflow of electrolytes. 
       FIG. 4  is a cross-sectional schematic view taken along line B-B′ of  FIG. 2 . 
     Referring to  FIG. 4 , in the same structure as  FIG. 3 , the intermediate cathode tabs  42  are covered by a pair of outermost cathode tabs  40 . Herein, the outermost cathode plate  41  is positioned in the outermost anode plate  51  with the separator  60  interposed therebetween. The intermediate cathode tabs  42  and the outermost cathode tab  40  may be formed at a location where they are not overlapped with an area where the intermediate anode tabs  52  and the outermost anode tab  50  are positioned. 
     While the insulating tape  70  is attached to a portion of a pair of outermost cathode tab  40  that are in contact with the pouch case  20 , a pair of outermost cathode tabs  40  can cover the intermediate cathode tabs  42  positioned therein. By this configuration, as processes of manufacturing the electrode assembly  10  are made simpler, productivity may be improved so that it becomes possible to save costs associated with providing for an additional electrode lead substrate. 
     In the above-mentioned embodiment, the anode plate is positioned at the center and at both outermost sides of the electrode assembly, but the cathode plate is positioned at the center and at both outermost sides of the electrode assembly. 
     Further, in the above-mentioned embodiment, although the pouch-type secondary battery has been described, embodiments of the present invention are not limited thereto. In addition, of course, the present invention can be applied to jelly-roll, cylindrical, and zigzag types of electrode assemblies having structures in which a long sheet-type of anode plate and a long sheet-type of cathode plate are wound with a separator interposed therebetween. 
     As described above, according to an embodiment of the present invention, a process of attaching an additional electrode lead can be omitted by increasing the thickness of an outermost substrate among electrode plates and the size of an electrode tab to tie electrode tabs of internal substrates and use them as an electrode lead. Therefore, as the process is made simpler, productivity can be improved to make it possible to save costs associated with providing for an additional electrode lead substrate. 
     While the present invention has been described in connection with certain embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, and equivalents thereof.