Curtailing the Overpotential of Li-CO Batteries with Shape-Controlled Cu O as Cathode: Effect of Illuminating the Cathode.

Li-air batteries are limited to lab-scale research owing to the uninterrupted formation of discharge products. In the case of Li-CO batteries, the increase in overpotential caused by Li CO formation results in cell death. In this study, Cu O crystals having three different types of shapes (i.e., cubic, octahedral, and rhombic) were synthesized to compare their catalytic activity toward CO reactions. The full-cycle and long-term stability test revealed that rhombohedral Cu O facilitates Li CO decomposition more efficiently than that of cubic and octahedral Cu O. The cycle was extended to investigate the photocatalytic activity of the rhombic Cu O by illuminating the cell. The repeated cycles to 1 h showed a maximum overpotential of 1.5 V, which is 0.5 V lower than that of the cell without illumination. A postmortem analysis of the cell after dividing the cycles into segments demonstrated interesting results concerning the role of light and Cu O during the cell cycle.