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.