NOVELTY - The battery has a negative electrode mixture layer that is formed on a surface of a negative electrode current collector and contains a negative electrode active material comprising a metal element alloyed with lithium. A foil substrate and a surface layer are provided on surfaces of the substrate on which the negative electrode mixture layer is formed. The Vickers hardness of the surface layer is 120 or less and less than that of the substrate. The proof stress of the negative electrode current collector is greater than 300 MPa.    USE - Lithium secondary battery used in mobile telephone, notebook computer and personal digital assistant. Can also be used in hybrid electric vehicle and power tools.    ADVANTAGE - The surface shape of the negative electrode current collector easily deforms into the shape of the negative electrode active material particles when the Vickers hardness is 120 or less. Hence the surface of the negative electrode current collector deforms along the shape of the negative electrode active material when pressing the negative electrode current collector after coating the negative electrode active material. Thus the contact area between the negative electrode current collector and the negative electrode active material is increased and the negative electrode active material can be prevented from peeling from the negative electrode current collector even when stress occurs due to the volume change of the negative electrode active material in association with charging and discharging. The negative electrode current collector can be fabricated according to the type of the negative electrode active material and the pressure during the pressure-rolling in preparing the negative electrode when the proof stress and the Vickers hardness can be set freely. Hence the peeling of the negative electrode active material is prevented and deformation of the negative electrode can be inhibited.    DESCRIPTION OF DRAWING(S) - The drawing shows a graph illustrating the relationship between the Vickers hardness of the surface layer and proof stress of the negative electrode current collector.    Line in which proof stress and Vickers hardness of negative electrode current collector cannot be selected freely (A)    Region in which proof stress and the Vickers hardness can be set freely within range (B)