A photo-assisted electrocatalyst coupled with superoxide suppression for high performance Li-O2 batteries

Highlights: • CeVO₄ serves as an unique bifunctional catalyst, facilitating conversion of superoxide intermediates during discharge and achieving charge overpotential reduction under photo-assisted condition. • Theoretical calculation and in-situ Raman spectra confirm the improved kinetics of oxygen reduction reaction on the surface CeVO₄ catalyst and the large suppression of side reactions. • The photo-assisted Li-O₂ batteries with CeVO₄ catalysts realize the discharge capacity increase by 1.6 times and high cycling stability at large current densities. Li-O₂ batteries are one of the most promising next generation batteries due to their high energy density. However, they suffer from high charge overpotentials and severe side reactions. Here we report a bifunctional CeVO₄ catalyst that not only lowers the charge potential by a photo-assisted mechanism, more importantly, promotes the efficient conversion of highly reactive oxidative intermediates to Li₂O₂, thus avoiding the oxidative decomposition of the electrolyte/cathode during discharge. Benefiting from its efficient electrocatalysis and the improved charging ability, 1.6x higher discharge capacity up to 6.14 mAh cm^-2, low charge potential of 3.48 V and stable cycling performance are simultaneously achieved. Theoretical calculation and in-situ Raman spectra confirm the superior adsorptive and conversion ability of superoxide species by electrochemical reduction and chemical disproportionation reactions on the CeVO₄ catalyst. These results indicate an effective strategy to break through the reported limitations of photo-assisted cathodes that are of a low electrocatalysis ability and limited discharge capacity. The significance of retaining a high energy density in photo-assisted Li-O₂ batteries is highlighted.