Le Wei,Yong Ma,Yuting Gu,Xuzhou Yuan,Ying He,Xinjian Li,Liang Zhao,Yang Peng,Zhao Deng
Rechargeable lithium–oxygen batteries (LOBs) have attracted increasing attention due to their high energy density but highly rely on the development of efficient oxygen catalysts for reversible Li2O2 deposition/decomposition. Herein, highly porous carbon nanocubes with a specific surface area up to 1600 m2 g–1 are synthesized and utilized to tightly anchor Ru nanoparticles for using as the oxygen-cathode catalyst in LOBs, achieving a low charge/discharge potential gap of only 0.75 V, a high total discharge capacity of 17,632 mA h g–1, and a superb cycling performance of 550 cycles at 1000 mA g–1. Comprehensive ex situ and operando characterizations unravel that the outstanding LOB performance is ascribed to the highly porous catalyst structure embedding rich active sites that synergistically function in reducing overpotentials, suppressing parasitic reactions, accommodating reaction products, and promoting mass and charge transportation.
Photo-assisted charge/discharge has witnessed marked success in Li-O 2 batteries (LOBs) to overcome the sluggish kinetics of triphasic reactions at the cathode, but challenges remain to develop high-efficiency but low-cost photocathode catalysts. Herein, a photoactive electron mediator is applied, for the first time, as bifunctional photocathode catalyst in solar-assisted LOBs. The facilely synthesized tris(2,2-bipyridine) cobalt(II) complex (Co-bpy) manifests good electrocatalytic activity in dark and high photoactivity under illumination, concertedly affording an superior charge/discharge voltage gap of 0.12 V and round-trip efficiency of 97%. Moreover, a significantly enhanced charge/discharge reversibility was attained under illumination and attributed to the light-induced amorphization of Li 2 O 2 that further extends the cycle life. A two-circuit model is proposed to rationalize the better reduction of charge/discharge polarization at lower operating current density. This work not only extends the family of photocathode catalysts to small-molecule complexes, but also offers new insights into the mechanism of photoenergy storage in LOBs.
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