NOVELTY - A cylindrical lithium secondary battery has an electrode assembly comprising strip-like anode and cathodes that are wound together with a porous heat-resistant layer with good electrolyte retention. The electrode assembly is housed in a cylindrical battery can. A mandrel (20) is inserted into a central cavity of the assembly, where the force of the mandrel which presses the assembly is correlated with the force of the assembly which presses a side wall of the battery can. A slit (20a) has a function of introducing a non-aqueous electrolyte that is held inside the mandrel into the assembly.    USE - Used as a power source in a portable electronic appliance, e.g. personal digital assistant, and small-sized power storage device that is utilized for home use, e.g. two-wheel motor vehicle, electric vehicle, and hybrid electric vehicle.    ADVANTAGE - The force of the mandrel which presses the electrode assembly is correlated with the force of the assembly which presses the side wall of the battery can, enabling the assembly to suitable extent even when the assembly has a porous heat-resistant layer, and hence providing excellent resistance to short-circuit, and thereby improving safety of the battery without causing a capacity loss upon impact such as dropping, and enabling the battery to have a good balance in battery characteristics. The thick porous heat-resistant layer has good electrolyte retention, thus maintaining good discharge characteristics of the battery even if the width of the slit is reduced.    DETAILED DESCRIPTION - A cylindrical lithium secondary battery comprises: a cylindrical battery can having 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 nonaqueous 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 electrode assembly has a central cavity into which a hollow mandrel is inserted, the hollow mandrel having a slit that extends along the entire length, where an outer diameter A of the hollow mandrel and a width B of the slit satisfy the relationship: 0.1 less than or equal to B/A less than or equal to 0.6.    DESCRIPTION OF DRAWING(S) - The figure shows a perspective view of a hollow mandrel.    Outer diameter (A)    Width (B)    Mandrel (20)    Slit (20a)