Highly Efficient Carbon-Array-Supported MnO2/RuO2 Cathodes for Lithium–Oxygen Batteries with Spatial and Induction Effects

Abstract

Through a facile, stepwise approach that includes electropolymerization, calcination, a hydrothermal method and low-temperature adsorption, a carbon array was coated with RuO2/MnO2 to form a highly efficient composite catalyst (RuO2/MnO2@carbon array) for Li–O2 batteries. The unique, hierarchical, three-dimensional array-type structure facilitates electrode wetting and oxygen transport as well as providing a large volume for Li2O2 loading. The growth of MnO2 nanosheets on the carbon array surface alters the surface roughness and provides attachment sites for the subsequent loading of catalyst nanoparticles. In addition, the introduction of RuO2 induces the formation of Mn3+ on the surface of MnO2, which not only improves the electrode conductivity but also the catalytic activity for ORR/OER. As a result, conformal growth of thin layers of Li2O2 on the surface of the RuO2/MnO2@carbon array and reversible decomposition of Li2O2 during cycling were achieved. In comparison with cathodes without a carbon array or catalyst, the Li–O2 cell with a RuO2/MnO2@carbon array cathode exhibits an markedly improved performance with high discharge capacity (10 000 mAh g−1 at 100 mA g−1) and long cycling life (252 cycles at 200 mA g−1 with a limited capacity of 500 mAh g−1).