Catalytic Performance of Amorphous and Crystalline RuO2 Loading on TiO2 Nanosheets in Lithium-Oxygen Batteries

Ruthenium oxide (RuO2) is considered as the ideal cathode catalyst for lithium-oxygen batteries (LOBs) because of its good electronic conductivity and electrocatalytic activity for the oxygen evolution reaction (OER). RuO2 has a variety of crystal structures, however, no studies to show which RuO2 structure has the best catalytic effect for LOBs. Here, we comparatively investigate the catalytic effect of amorphous RuO2 (a-RuO2) and crystalline RuO2 (c-RuO2) loading on titanium dioxide (TiO2) nanosheets for LOBs. The electrochemical results demonstrate that the a-RuO2/TiO2 catalyst has better electrochemical performances than the c-RuO2/TiO2 catalyst. The a-RuO2/TiO2 cathode displays a discharge capacity of 2.3 mAh cm(-2) and operates stably for more than 160 cycles. By contrast, c-RuO2/TiO2 provides a discharge capacity of 1.4 mAh cm(-2) and is cycled only 100 cycles. Structural characterization and electrochemical impedance spectroscopy show that the Li2O2 products formed on an a-RuO2/TiO2 cathode are smaller than those of a c-RuO2/TiO2 cathode, which however have a higher reversibility than those of a c-RuO2/TiO2 cathode. Our work may provide some insights from the experimental side for the future cathode design of high-performance LOBs.