NOVELTY - A lithium secondary battery has an electrode group provided with a positive electrode (66) and a negative electrode. The positive electrode is equipped with a positive electrode layer (64) containing a positive-electrode active material (67) on a positive electrode collector (62). The negative electrode is equipped with a negative electrode layer on a negative electrode collector. At least one of positive electrode layer and negative electrode layer contains a thermal absorption material (69) comprising a substance which shows phase change from solid to liquid.    USE - Lithium secondary battery is used for vehicle (claimed) e.g. hybrid vehicle, electric vehicle and fuel-cell electric vehicle.    ADVANTAGE - The lithium secondary battery is safe, and has excellent reliability and heavy-current output characteristics. The thermal decomposition of positive-electrode active material in the lithium secondary battery is prevented.    DETAILED DESCRIPTION - A lithium secondary battery has an electrode group provided with a positive electrode and a negative electrode, and a case where electrode group and an electrolyte are accommodated. The positive electrode is equipped with a positive electrode layer containing a positive-electrode active material formed on a positive electrode collector. The negative electrode is equipped with a negative electrode layer comprising negative-electrode active material formed on a negative electrode collector. At least one of positive electrode layer and negative electrode layer contains a thermal absorption material comprising a substance which shows phase change from solid to liquid at predetermined temperature. The thermal absorption material has double structure coated with an oxide film containing oxide of substance comprising thermal absorption material on surface. When the temperature of electrode layer reaches predetermined temperature, the thermal absorption material optionally carry out phase change from solid to liquid and flows out to inner region of electrode layer.    DESCRIPTION OF DRAWING(S) - The drawing shows the positive electrode layer on positive electrode collector.    Positive electrode collector (62)    Positive electrode layer (64)    Positive electrode (66)    Positive-electrode active material (67)    Thermal absorption material (69)