Reversible Phase Transition in Ruddlesden-Popper-type Oxysulfide Y2Ti2O5S2 for Lithium-Ion Battery Anodes (Supporting Information)

Oxysulfides have the potential for battery electrodes to have durability and rate capability due to their rigid structures and electronic conductivity. Herein, we focus on the Ruddlesden-Popper phase oxysulfide Y2Ti2O5S2 and investigate the phase evolution of Y2Ti2O5S2 during electrochemical Li+ intercalation and deintercalation. The tetragonal structure is maintained down to 0.35 V during the lithiation process. A two-phase reaction between the tetragonal phase and the orthorhombic phase was observed at a voltage plateau region between 0.35 and 0.3 V. Subsequently, the tetragonal phase recovers for further lithiation process. The relatively low lattice volume change of 5 % compared with graphite anode leads to stable cycling performances.