My money is on it being an air battery, in the paper they commented: "The charge and discharge voltages show a good coulombic efficiency over 1000 h; the cyclin

My money is on it being an air battery, in the paper they commented: "The charge and discharge voltages show a good coulombic efficiency over 1000 h; the cycling was continued beyond 46 cycles despite an imperfect seal of the cell. " A rather simple test to determine if it is in fact behaving as an air battery would be to weigh the battery before and after discharge. Air batteries get heavier as they discharge.