Effect of Mesoporous Structured Cathode Materials on Charging Potentials and Rate Capability of Lithium-Oxygen Batteries

Solid and nonconductive discharge products that form on the cathode of Li-O-2 batteries are difficult to decompose efficiently into Li+ and O-2 during charging, which induces a high overcharge potential, low energy efficiency, and poor cyclability. In this paper, we investigated the effects of the mesoporous structure on the morphology of the discharge products, the capacities of the cells, and the discharging/charging potentials. To isolate the effect of the mesostructures, mesoporous carbons, CMK-3 and MSU-F-C, were used without the addition of other electrocatalysts. The discharge products were confined within the pores. Consequently, the charging potentials were decreased owing to small and amorphous lithium oxides. The large, 3D interconnected pores of MSU-F-C lowered the charging potentials at a high current density and increased the rate capabilities relative to the parameters found for the small pores of CMK-3. These results demonstrate that control of the porous structure is necessary to enhance the performance of Li-O-2 batteries.