The feasibility and limitation of urine as the electrolyte for primary Mg-air batteries

Abstract

This work investigates the discharge performance of Mg-air battery using simulated urine (SU) and 3.5 wt.% NaCl solution as the electrolyte. The discharge voltage in SU is much lower than in 3.5 wt. % NaCl solution because of the higher internal resistance. The surface film layer of urea and the high solution resistance due to the low conductivity of SU are the two major compositions of the internal resistance in SU. The Mg-air battery has almost the same best discharge capacity and anodic efficiency at 20 mA cm-2 in both two electrolytes; nevertheless, its energy output in SU is much lower than in 3.5 wt. % NaCl solution. Although the Mg-air battery has a poor performance in SU, it is feasible to use urine in some emergency conditions.