NOVELTY - The lithium secondary battery comprises an electrode group, a non-aqueous electrolyte, and a battery case for housing the electrode group and the non-aqueous electrolyte. The electrode group comprises a positive electrode (21) comprising a strip-shaped positive electrode current collector and a positive electrode material mixture layer carried on the positive electrode current collector, and a negative electrode (22) comprising a strip-shaped negative electrode current collector and a negative electrode material mixture layer carried on the negative electrode current collector.    USE - The lithium secondary battery is useful as a power source for portable devices such as personal digital assistants and mobile electronic devices and for two-wheeled vehicles, electric vehicles and hybrid electric vehicles, and in electrical energy storage system for home use.    ADVANTAGE - The lithium secondary battery is lightweight, has high energy density, stability and capacity and improved battery resistance and charge/discharge characteristics, and ensures high level of safety in an internal short-circuit and during nail penetration test.    DETAILED DESCRIPTION - The lithium secondary battery comprises an electrode group, a non-aqueous electrolyte, and a battery case for housing the electrode group and the non-aqueous electrolyte. The electrode group comprises a positive electrode (21) comprising a strip-shaped positive electrode current collector and a positive electrode material mixture layer carried on the positive electrode current collector, a negative electrode (22) comprising a strip-shaped negative electrode current collector and a negative electrode material mixture layer carried on the negative electrode current collector, a separator (23), and a porous heat resistant layer. The positive electrode and the negative electrode are spirally wound with the separator and the porous heat resistant layer interposed between the electrodes. The battery case comprises a first battery can (25) for housing the electrode group, and a second battery can (26) for housing the first battery can, and an insulating layer (27) disposed between the first battery can and the second battery can. The positive electrode and/or negative electrode are electrically connected to the first battery can, and the other electrode is electrically connected to the second battery can.    DESCRIPTION OF DRAWING(S) - The diagram shows a cross-sectional view of a lithium secondary battery.    Positive electrode (21)    Negative electrode (22)    Separator (23)    First battery can (25)    Second battery can (26)    Insulating layer. (27)