Enhancement of catalytic centres by RuO2 addition to CuFe2O4 cathode catalyst for rechargeable lithium–air batteries: influence of CO2 on Li–O2 battery performances†

Abstract

Herein, the oxygen reduction reaction and oxygen evolution reaction (ORR/OER) kinetics of the inverse-spinel CuFe₂O₄ catalyst was enhanced via the addition of a very low quantity of RuO₂. It was found that minimal addition of RuO₂ resulted in an improvement in the limiting current density and onset potential, lower Tafel slope and good stability for the ORR/OER. Additionally, the CuFe₂O₄ cathode catalyst with the optimal RuO₂ content resulted in an outstanding Li–O₂ battery capacity of 14 250 mA h g⁻¹. Given that the presence of CO₂ poses a major challenge in achieving Li–air batteries at a practical level, the performance of the optimized catalyst under a strained Li–air condition and in pure CO₂ atmosphere (Li–CO₂ battery) was analyzed to understand its CO₂ tolerance and stability. It is crucial to understand the capability of the catalyst to decompose Li₂CO₃ formed as a stable discharge product from CO₂, which generally clogs the pores of the cathode catalyst. Thus, in situ impedance analysis and ex situ XRD technique were applied to decipher the fate of CO₂ in the reactions of Li–air/Li–CO₂ batteries. Moreover, stabilization to prevent the decomposition of the electrolyte was achieved in the presence of CO₂.