Amorphous Niobium Sulfides as Novel Positive-Electrode Materials

摘要

Novel high-capacity electrode materials are required to increase the energy density of lithium-ion batteries. Metal polysulfides, MS_x (x > 2), are plausible candidates for such materials, whose high capacities are owed to multielectron processes. Hence, we mechanochemically synthesized novel amorphous niobium sulfides (NbS_3, NbS_4, and NbS_5) at room temperature. The cells fabricated using amorphous NbS_3, NbS_4, and NbS_5 showed high initial discharge capacities of 281, 446, and 596 mAh g~(-1), corresponding to 2.0, 3.7, and 5.6 electron processes per formula unit, respectively. Remarkably, the cells using a carbonate-based electrolyte showed reversible high-capacity charging and discharging.