Ruthenium@mesoporous graphene-like carbon: a novel three-dimensional cathode catalyst for lithium–oxygen batteries

Abstract

Nonaqueous lithium–oxygen (Li–O₂) batteries are considered as the most promising energy storage systems, because of their very high energy densities, which are significantly greater than those of lithium-ion batteries. Recently, carbon materials have been widely used as cathode catalysts for Li–O₂ batteries due to their outstanding conductivity. However, side reactions are inevitable when the carbon materials are exposed to the Li₂O₂ product and the organic electrolytes, leading to degradation in their cycling performances. Herein, we propose a simplified strategy, which combines the template method and in situ growth approach in order to establish a three-dimensional (3D) mesoporous graphene-like carbon structure, and growth of a uniform layer of ruthenium particles on it. The as-prepared 3D ruthenium@mesoporous graphene-like carbon material delivers a reversible capacity of about 6433 mA h g⁻¹ (based on the total mass of the composite) at a current density of 200 mA g⁻¹, when it is used as a cathode catalyst for Li–O₂ batteries. Under a curtaining capacity of 500 mA h g⁻¹, it exhibits an extremely low charge voltage of 3.20 V (only 240 mV higher than the thermodynamic potential) and a high discharge voltage of 2.84 V at a current density of 100 mA g⁻¹.