Mechanochemical synthesis of cubic rocksalt Na₂TiS₃ as novel active materials for all-solid-state sodium secondary batteries

Abstract

Mechanochemical (MC) process is one of the most effective methods to produce amorphous and cation disordered electrode active materials. We individually synthesized amorphous and cation disordered cubic rocksalt Na₂TiS₃ by controlling the preparation conditions of the MC process. Cubic rocksalt Na₂TiS₃ and ordered monoclinic Na₂TiS₃ were also obtained via the heat treatment of amorphous Na₂TiS₃. The all-solid-state cell with cubic rocksalt Na₂TiS₃ showed a high reversible capacity of 270 mAh g⁻¹, which corresponds to the theoretical capacity of Na₂TiS₃. The cell maintained the capacity for more than 30 cycles, indicating that the active materials can endure long operation life. The MC methods for transition metal sulfides and the search for ordered monoclinic polymorphs are necessary for the pursuit of novel electrode materials.