PURPOSE: To make it possible to obtain favorable discharge performance by providing the case side surface of a lithium to be press-applied to the inner surface of a cylindrical can with a vertical groove and partially cut portions.

CONSTITUTION: A press-fit lithium 2 has such a structure that a groove portion in the same direction with the axial direction of a cylindrical can 1 side surface or part of it is cut off. By providing the negative electrode lithium 2 with a cut-off portion 11 for example, electrolyte 3 of free condition can be made present in the portion 11, or movement of the electrolyte 3 in a central hollow space to an interface between an positive electrode collector body 6, lithium 2 and separator 4 becomes easier. As a result, favorable discharge performance is obtained without shortening discharge continuation time.