An electrode assembly for a lithium ion secondary battery and a lithium ion secondary battery using the same are provided. In a sealing tape attached to the outer circumference of the electrode assembly in order to prevent the wound electrode assembly from being unwound, the sealing tape is formed of the material having an affinity for the electrolyte to absorb the electrolyte and to swell or the external or internal surface of the conventional sealing tape is coated with such a material so that, when the sealing tape is impregnated with the electrolyte, the sealing tape swells to attach the electrode assembly and the can to each other and to thus prevent the welding parts of the electrode tabs from being disconnected due to the rotation or floating of the electrode assembly.