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Two better than one: cobalt–copper bimetallic yolk–shell nanoparticles supported on graphene as excellent cathode catalysts for Li–O2 batteries

Despite the extremely high energy density of Li–O2 batteries, the sluggish kinetics severely hinder their practical applications. Here, we report the preparation and electrochemical performance of cost-effective cobalt–copper bimetallic nanoparticles supported on graphene (CoCu/graphene) as the cathode material for Li–O2 batteries. The batteries delivered a high initial discharge capacity of 14 821 mA h g−1 and a low average charge voltage of ∼4.0 V at 200 mA g−1. In addition, the batteries exhibited superior rate capability (7955 mA h g−1 at 800 mA g−1), long cyclability (122 cycles at 200 mA g−1 with a cutoff capacity of 1000 mA h g−1), and outstanding coulombic efficiency (92% at 200 mA g−1). These superior performances resulted from the synergistic effect of non-noble metal Co and Cu supported on graphene, which could simultaneously enhance the oxygen reduction and evolution reaction kinetics. The favorable composite ensures uniform coverage of nanowall-shaped Li2O2 on CoCu/graphene instead of typical toroidal Li2O2 aggregation, thus promoting the reversible formation and decomposition of discharge product Li2O2. The excellent catalytic performance is expected to provide new insights into designing low-cost and high-efficiency cathode materials for Li–O2 batteries and promote their practical applications.