Dual-electrolyte lithium–air batteries: influence of catalyst, temperature, and solid-electrolyte conductivity on the efficiency and power density

Abstract

Two major issues limiting the conversion efficiency and power density of dual-electrolyte Li–air cells are the lack of efficient oxygen evolution catalysts and high internal resistance associated with the solid electrolyte. In this context, the charge voltage is lowered by 0.11 V at a charge current density of 2 mA cm⁻² by employing nanocrystalline IrO₂ synthesized by a modified Adams fusion method. Similarly, the overall internal resistance of the cell is reduced substantially by increasing the operating temperature of the cell from 20 to 40 °C, resulting in a nearly three-fold increase in the maximum power density. Overall, the conversion efficiency at 2 mA cm⁻² is improved from 61% to 74% at 40 °C with the nanocrystalline IrO₂. The internal resistance is further reduced by employing a more conductive solid electrolyte at 40 °C, resulting in a maximum power density and conversion efficiency at 2 mA cm⁻² of, respectively, 40 mW cm⁻² and 80%.