An alkaline cell having a flat housing, preferably of cuboid shape. The cell can have an anode comprising zinc and a cathode comprising MnO₂. The housing can have a relatively small overall thickness, typically between about 5 and 10 mm. Cell contents can be supplied through an open end in the housing and an end cap assembly inserted therein to seal the cell. The end cap assembly includes an insulating sealing member having a circumferential skirt which surrounds wide portions of the anode current collector. This provides a barrier between said wide portions of the current collector and the cell housing. The end cap assembly includes a vent mechanism which can activate, when gas pressure within the cell reaches a level typically between about 100 and 300 psig (6.8910⁵ and 20.6910⁵ pascal gage). The cathode can be formed of a plurality of stacked slabs having aligned hollow centers forming a central core with anode material placed therein. A separator is between anode and cathode. The housing can be of steel having a wall thickness desirably between about 0.30 and 0.45 mm.