NOVELTY - The battery has positive and negative electrode sheets (10,20) which are equipped with positive and negative electrode compound material layers (14,24) formed on positive and negative electrode collectors (12,22) respectively. A positive electrode assist layer (16) with electrically conductive material is formed on positive electrode collector and is adjacent to positive electrode active material layer. An overcharge inhibiting agent contained in the electrolyte generates gas, when the electrolyte exceeds predetermined battery voltage.    USE - Enclosed lithium secondary battery used as power source for motor mounted in vehicle e.g. motor vehicle such as plug-in hybrid motor vehicle e.g. car (from drawings). Can also be used in hybrid vehicle, electric vehicle, fuel cell electric vehicle, personal computer and portable terminal.    ADVANTAGE - The electric current breaker structure can be operated rapidly and promptly at the time of an overcharge. The reaction zone of an overcharge inhibiting agent can be increased remarkably, thus the lot of gas can be generated rapidly at the time of an overcharge. The width of positive electrode compound material layer is made narrower than width of negative electrode compound material layer which opposes, in order to prevent generation of internal short circuit by precipitation of lithium. The enclosed lithium secondary battery has excellent battery performance and high tolerance. The reliability and the energy density of the lithium secondary battery can be improved effectively. The weight of the lithium secondary battery can be reduced effectively.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross sectional view of the enclosed lithium secondary battery.    Positive electrode sheet (10)    Positive electrode collector (12)    Positive electrode compound material layer (14)    Positive electrode assist layer (16)    Negative electrode sheet (20)    Negative electrode collector (22)    Negative electrode compound material layer (24)