Influence of Binders and Solvents on Stability of Ru/RuO x Nanoparticles on ITO Nanocrystals as Li–O 2 Battery Cathodes

Fundamental research on Li–O 2 batteries remains critical, and the nature of the reactions and stability are paramount for realising the promise of the Li–O 2 system. We report that indium tin oxide (ITO) nanocrystals with supported 1–2 nm oxygen evolution reaction (OER) catalyst Ru/RuO x nanoparticles (NPs) demonstrate efficient OER processes, reduce the recharge overpotential of the cell significantly and maintain catalytic activity to promote a consistent cycling discharge potential in Li–O 2 cells even when the ITO support nanocrystals deteriorate from the very first cycle. The Ru/RuO x nanoparticles lower the charge overpotential compared with those for ITO and carbon‐only cathodes and have the greatest effect in DMSO electrolytes with a solution‐processable F‐free carboxymethyl cellulose (CMC) binder (<3.5 V) instead of polyvinylidene fluoride (PVDF). The Ru/RuO x /ITO nanocrystalline materials in DMSO provide efficient Li 2 O 2 decomposition from within the cathode during cycling. We demonstrate that the ITO is actually unstable from the first cycle and is modified by chemical etching, but the Ru/RuO x NPs remain effective OER catalysts for Li 2 O 2 during cycling. The CMC binders avoid PVDF‐based side‐reactions and improve the cyclability. The deterioration of the ITO nanocrystals is mitigated significantly in cathodes with a CMC binder, and the cells show good cycle life. In mixed DMSO–EMITFSI [EMITFSI=1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide] ionic liquid electrolytes, the Ru/RuO x /ITO materials in Li–O 2 cells cycle very well and maintain a consistently very low charge overpotential of 0.5–0.8 V.