PURPOSE: To connect a cell to a power supply circuit by soldering without causing the short-circuit between electrodes, by forming a metallic film in the lead terminal part by electroless plating after forming a hydrophobic film on the outside end part of the cell.

CONSTITUTION: As a hydrophobic maeterial, a silicone resin or a fluororesin is specifically best, and an organic matter or a high polymer having a low wetting property to water soluble in a solvent may be used. After alkali degreasing and washing with water, the cell is immersed in an electroless plating bath. A metallic film is formed only in the terminal part of the cell, and this film is plated with gold by electroless plating to improve the solder characteristics. The short- circuit between upper and lower electrodes is prevented because the deposition of plating is not generated in an outside end part 7, and the tensile strength, which is obtained when a copper wire is provided on a nickel electroless plating film by a solder, is 0.6kg/mm2 and sufficient.