Dramatically enhanced reversibility of Li2O in SnO2-based electrodes: the effect of nanostructure on high initial reversible capacity

Abstract

The formation of irreversible Li₂O during discharge is believed to be the main cause of large capacity loss and low Coulombic efficiency of oxide negative electrodes for Li batteries. This assumption may have misguided the development of high-capacity SnO₂-based anodes in recent years. Here we demonstrated that contrary to this perception, Li₂O can indeed be highly reversible in a SnO₂ electrode with controlled nanostructure and achieved an initial Coulombic efficiency of ∼95.5%, much higher than that previously believed to be possible (52.4%). In situ spectroscopic and diffraction analyses corroborate highly reversible electrochemical cycling, suggesting that the interfaces and grain boundaries of nano-sized SnO₂ may suppress the coarsening of Sn and enable the conversion between Li₂O and Sn to amorphous SnO₂ when de-lithiated. These results provide important insight into the rational design of high-performance oxide electrodes for Li-ion batteries.