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

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.