Performance of a thermally regenerative ammonia-based battery using gradient-porous copper foam electrodes

Abstract

Gradient-porous copper foam electrodes were applied to alleviate the adverse effects of the uneven current distribution of electrodes along the electrolyte flow direction in thermally regenerative ammonia-based batteries (TRABs). The results indicated that gradient-porous copper foam with a decreasing pore size (TRAB-LMS) provided the most uniform current distribution and generated the highest power density (15.5 W/m2), total charge (1800 C) and energy density (1224 W h/m3). With the increase in flow rate, the power density of the TRAB-LMS increased considerably within a certain range and then decreased slightly, with the optimal flowrate at 15 mL/min. Under the optimal flow rate, the performance of TRAB-LMS increased when the ammonia concentration rose from 0.5 to 2 M (1 M=1 mol L−1); however, it decreased slightly when the ammonia concentration further increased to 3 M. The slight decrease in the cathode potential suggested that the flow and ammonia concentration beyond the optional values facilitated not only the transfer of ammonia into the porous anode, but also the crossover of ammonia from the anode to the cathode.