A combined approach for high-performance Li-O₂ batteries: A binder-free carbon electrode and atomic layer deposition of RuO₂ as an inhibitor-promoter

A rechargeable lithium-oxygen (Li-O₂) battery is considered as a promising technology for electrochemical energy storage systems because its theoretical energy density is much higher than those of state-of-the-art Li-ion batteries. The cathode (positive electrode) for Li-O₂ batteries is made of carbon and polymeric binders; however, these constituents undergo parasitic decomposition reactions during battery operation, which in turn causes considerable performance degradation. Therefore, the rational design of the cathode is necessary for building robust and high-performance Li-O₂ batteries. Here, a binder-free carbon nanotube (CNT) electrode surface-modified by atomic layer deposition (ALD) of dual acting RuO₂ as an inhibitor-promoter is proposed for rechargeable Li-O₂ batteries. RuO₂ nanoparticles formed directly on the binder-free CNT electrode by ALD play a dual role to inhibit carbon decomposition and to promote Li₂O₂ decomposition. The binder-free RuO₂/CNT cathode with the unique architecture shows outstanding electrochemical performance as characterized by small voltage gaps (∼0.9 V) as well as excellent cyclability without any signs of capacity decay over 80 cycles.