Closed cycle aluminum/oxygen fuel cell with increased mission duration

To fully realize the high energy density of the Al/O₂ system, the cell stack must be integrated with an electrolyte management system that includes a filter/precipitator and a hydrogen removal unit. The filter/precipitator increases mission duration by continuously regenerating potassium hydroxide and storing cell discharge products compactly as a crystalline hydroxide species, Al(OH)₃. By maintaining a high and nearly constant electrolyte conductivity, stack voltage remains steady throughout the discharge cycle. Operation of the filter/precipitator system integrated with an Al/O₂ cell stack and the effects of important process variables such as temperature, electrolyte flux, and anode dissolution rate are discussed. The closed cycle requirement demands a hydrogen removal unit capable of continuously removing the hydrogen generated by corrosion of the anode in a safe manner. Hydrogen destruction by catalytic recombination is especially attractive for electric propulsion applications where space and energy efficiency are highly valued