An improved pressure vessel for a rechargeable metal oxide-hydrogen battery. The pressure vessel, which contains a plurality of cell modules, is composed of an inner liner of a material which is impervious to the passage of hydrogen gas and an outer layer of fiber reinforced thermosetting resin. The fibrous reinforcement is preferably in the form of substantially continuous, helically wound filaments. Dispersed within the resin matrix of the outer layer are a plurality of finely divided particles of a material having a high coefficient of thermal conductivity. The finely divided material can be in the form of powder or fibers, and can be composed of a metal or graphite. By incorporating the finely divided heat conductive particles in the resin, the heat dissipation through the pressure vessel is increased to thereby improve the performance of the battery.