Abstract: A dry cell comprising an anode made of zinc and cathode mixture which includes manganese dioxide acting as active agent and conductor such that acetylene black having a specific surface area of 100 to 150 m.sup.2 /g measured by a BET type nitrogen gas adsorption method is used as the conductor by setting a mixing ratio in weight of the manganese dioxide to the acetylene black at 7/1 to 12/1.

Abstract: An outer metal jacket for a dry cell, prepared by butting a rectangular metal plate at both side edges and joining the butted part by welding or bonding to make a cylindrical body, characterized in that a part having smaller mechanical strength is integrally provided on at least one of the upper and lower rims of the cylindrical body as a safety mechanism. When the inner pressure is increased by any reason originated from an electrochemical cell system accommodated therein, the safety mechanism is opened outwardly and the increased pressure is reduced therethrough.

Abstract: A dry cell which is so arranged that, with a bottom plate being disposed at the lower portion of a raw cell sealed at its opening by a sealing member, an insulative seal packing is applied onto the peripheral portion of the bottom plate, while the raw cell and the peripheral portion of the bottom plate are surrounded by a metal jacket welded by laser at its butted opposite ends. At the peripheral portion of the bottom plate, a gas discharge mechanism is formed which is arranged to be normally closed by the seal packing, and to be released from the closing by the seal packing due to deformation of the bottom plate upon increase of internal pressure of the dry cell for discharging the gas within the dry cell outside, and thus, a safe dry cell free from a danger of rupture maybe provided.