Amorphous Niobium Sulfides as Novel Positive-Electrode Materials

Novel high-capacity electrode materials are required to increase the energy density of lithium-ion batteries. Metal polysulfides, MSx (x > 2), are plausible candidates for such materials, whose high capacities are owed to multielectron processes. Hence, we mechanochemically synthesized novel amorphous niobium sulfides (NbS3, NbS4, and NbS5) at room temperature. The cells fabricated using amorphous NbS3, NbS4, and NbS5 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. (C) 2014 The Electrochemical Society. All rights reserved.