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

Ruthenium oxide (RuO 2 ) 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). RuO 2 has a variety of crystal structures, however, no studies to show which RuO 2 structure has the best catalytic effect for LOBs. Here, we comparatively investigate the catalytic effect of amorphous RuO 2 (a-RuO 2 ) and crystalline RuO 2 (c-RuO 2 ) loading on titanium dioxide (TiO 2 ) nanosheets for LOBs. The electrochemical results demonstrate that the a-RuO 2 /TiO 2 catalyst has better electrochemical performances than the c-RuO 2 /TiO 2 catalyst. The a-RuO 2 /TiO 2 cathode displays a discharge capacity of 2.3 mAh cm –2 and operates stably for more than 160 cycles. By contrast, c-RuO 2 /TiO 2 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 Li 2 O 2 products formed on an a-RuO 2 /TiO 2 cathode are smaller than those of a c-RuO 2 /TiO 2 cathode, which however have a higher reversibility than those of a c-RuO 2 /TiO 2 cathode. Our work may provide some insights from the experimental side for the future cathode design of high-performance LOBs.