A free-standing CeO2/Co3O4 nanowires electrode featuring a controllable discharge/charge product evolution route with enhanced catalytic performance for Li-O2 batteries

Abstract

Although transition metal oxides are important potential catalytic cathode materials for Li-O2 batteries (LOBs), their poor cycle durability at high current density, high overpotentials and side reaction are still the challenges to solve. Herein, CeO2/Co3O4 nanowire arrays grown on Ni foam were fabricated as a free standing cathode of LOBs, featuring a controllable discharge/charge products evolution route. CeO2 served as active sites for nucleation, initial growth and decomposition of Li2O2. The embedded CeO2 nanocrystalline on Co3O4 substrate dominated the initial discharge/charge product evolution with multi-formation kinetics of crystal Li2O2 and Li2-xO2 at high current densities which leading to low overpotentials and efficient decomposition of discharge products. Owing to the stable structure, the CeO2/Co3O4 nanowires were found to energetically favor the mass transport between the electrode/electrolyte interface during long cycle testing. As a consequence, excellent cyclability of 500 cycles at high current density (500 mA g−1) under a fixed capacity of 500 mA h g−1 with low overpotentials of 0.2 V and 1.0 V for discharge/charge process (after 500 cycles) were achieved. The present work provides a new strategy and intrinsic insight in designing high-performance metal oxides electrocatalysts with a fine-tuned structure for LOBs.