Unique Reversible Conversion-Type Mechanism Enhanced Cathode Performance in Amorphous Molybdenum Polysulfide.

A unique reversible conversion-type mechanism is reported in the amorphous molybdenum polysulfide (a-MoS5.7) cathode material. The lithiation products of metallic Mo and Li2S2 rather than Mo and Li2S species have been detected. This process could yield a high discharge capacity of 746 mAh g-1. Characterizations of the recovered molybdenum polysulfide after the delithiaiton process manifests the high reversibility of the unique conversion reaction, in contrast with the general irreversibility of the conventional conversion-type mechanism. As a result, the a-MoS5.7 electrodes deliver high cycling stability with an energy-density retention of 1166 Wh kg-1 after 100 cycles. These results provide a novel model for the design of high-capacity and long-life electrode materials.