Temperature-Dependent Discharge of Li-O2 and Na-O2 Batteries

Abstract

Li-O2 and Na-O2 batteries offer the promise of increased energy densities compared to Li-ion batteries but suffer from poor power and cycle life. Despite considerable research on the oxygen reduction reaction (ORR) in these cells at room temperature, limited work has been performed to understand the influence of temperature on the discharge characteristics. In this Letter, we show that the discharge capacity of Li-O2 cells increases with increasing temperature while the discharge capacity of Na-O2 cells decreases over the same temperature range. We show that the discharge behavior of Na-O2 cells is dominated by increasing superoxide solubility with decreasing temperature. On the other hand, increasing Li+-O2– coupling strength with decreasing temperature promotes the formation of insoluble Li2O2 through either disproportionation or a 2e– reduction mechanism, leading to reduced discharge capacity in Li-O2 cells. Such findings highlight the complex and important effect that temperature has on ORR in Li-O2 and Na-O2 batteries.