A zinc/air cell having thin walled cup shaped anode casing and cathode casing. The cell may be a button cell having an anode comprising zinc and a cathode, which may be catalytic, comprising manganese dioxide. The anode and cathode casings have small wall thicknesses, preferably between 2 and 5 mil (0.0508 and 0.127 mm), desirably between about 2 and 3 mil (0.0508 and 0.0762 mm). There is an insulating seal ring covering at least a portion of the anode casing side walls. During cell assembly the cathode casing side wall is pushed over at least a portion of the anode casing side wall with insulating sealing disk therebetween. A tight interference fit is achieved with the outside diameter of the anode casing plus insulating seal thereon being preferably between about 2 and 4.5 mil (0.0508 and 0.114 mm) greater than the inside diameter of the cathode casing. This reduces the tendency of the casing side walls to spring back after crimping.