NOVELTY - A lithium secondary battery (10) comprises an electrode group (20), including a first electrode (cathode) (22), a second electrode (anode) (24), and a separator (26) disposed between the first electrode and the second electrode; a first electrode tab (32) connected to the first electrode; and a second electrode tab (34) connected to the second electrode, where the first electrode tab includes a first portion connected to the first electrode and a second portion, which is not the first portion, and a width of the first portion is less than a width of the second portion.    USE - As a lithium secondary battery useful as a power source in electronic communication devices and for high-power hybrid vehicles.    ADVANTAGE - The lithium secondary battery has excellent electrical properties and safety and a long lifetime. The lithium secondary battery has one electrode having two portions with different widths from each other, thus simultaneously improving different properties. Because a first portion connected to the electrode is formed to have a relatively small width, warping or wrinkling of the electrode may be effectively prevented. Thus, in an electrode group, electrodes are uniformly brought into close contact with each other, effectively preventing the distortion of the electrode group and the deposition of lithium and ensuring a uniform battery reaction. Consequently, the safety and lifetime of the lithium secondary battery may be increased, and the electrical properties of the battery may be improved. The second portion, which is not connected to the electrode, is formed to have a relatively large width, thus efficiently transferring electrical energy from the electrode group and improving heating properties, ultimately ensuring stable operation of the lithium secondary battery.    DETAILED DESCRIPTION - A lithium secondary battery (10) comprises an electrode group (20), including a first electrode (cathode) (21), a second electrode (anode) (24), and a separator (26) disposed between the first electrode and the second electrode; a first electrode tab (32) connected to the first electrode; and a second electrode tab (34) connected to the second electrode, where the first electrode tab includes a first portion connected to the first electrode and a second portion, which is not the first portion, and a width of the first portion is less than a width of the second portion. The first electrode has a tab junction which is protruding therefrom in order to be connected to the first portion. The second portion has a protruding shape that extends laterally in one direction with respect to the first portion. The second electrode tab comprises a third portion connected to the second electrode and a fourth portion, which is not the third portion, and a width of the third portion is less than a width of the fourth portion. The lithium secondary battery further comprises a battery case for enclosing and sealing the electrode group while exposing ends of the first electrode tab and the second electrode tab, where an adhesion portion of the battery case is located on the second portion.    DESCRIPTION OF DRAWING(S) - The figure shows a perspective view of lithium secondary battery.    Lithium secondary battery (10)    Electrode group (20)    First electrode (22)    Second electrode (24)    Separator (26)    First electrode tab (32)    Second electrode tab (34)    Battery case. (40)