Previous info on this process suggest about 50% of the energy in the Aluminum is released as heat, 50% is H2. The fuel cell is about 50% efficient in converting H2 to power, and the reprocessing to create aluminum again is also about 50% efficient - this is the original energy source. All up power to power efficiency is therefore 12.5% - while a Li-Ion battery is about 90%. The battery may be more expensive (though all the reprocessing infrastructure will not be cheap) but batteries need no materials handling is required and a factor of 7 on efficiency is pretty persuasive.