NOVELTY - A cylindrical lithium secondary battery has a side wall, and an electrode assembly that includes an anode (13) and a cathode which are wound together with a porous heat-resistant layer (18). A separator is interposed between the electrodes, where the electrodes have anode and cathode core units and anode and cathode active material layers carried on each side of the anode and cathode core units, respectively. The porous heat-resistant layer including a specific thickness and the sidewall including a specific thickness satisfies a specific relation.    USE - Used as a power source for a portable electronic appliance, e.g. personal digital assistant, and home application, electric vehicle, two-wheel motor vehicle and hybrid electric vehicle.    ADVANTAGE - The porous heat-resistant layer including the specific thickness and the sidewall including the specific thickness satisfies the specific relation, thus effectively controlling force of the side wall of the battery which pushes back the porous heat-resistant layer in an appropriate range depending on the thickness of the porous heat-resistant layer, and hence preventing the porous heat-resistant layer from breaking. The battery thus ensures a high level of safety in an event of internal short-circuits, thereby providing the battery with high rate of discharge characteristics.    DETAILED DESCRIPTION - A cylindrical lithium secondary battery comprises: a battery can with a base, a side wall, and an open top; an electrode assembly; a non-aqueous electrolyte; and a sealing plate covering the open top of the battery can that accommodates the electrode assembly and electrolyte. The electrode assembly comprises a strip-like anode and a strip-like cathode that are wound together with a porous heat-resistant layer and a separator between the anode and cathode. The anode comprises an anode core member and an anode active material layer carried on each side of the anode core member. The cathode comprises a cathode core member and a cathode active material layer carried on each side of the cathode core member. The thickness A of the porous heat-resistant layer and a thickness B of the side wall of the battery satisfies the relationship: 0.005 less than or equal to A/B less than or equal to 0.1.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional schematic view of a part of a cylindrical lithium secondary battery.    Anode core unit (11)    Anode active material layer (12)    Anode (13)    Cathode active material layer (15)    Porous heat-resistant layer (18)