Promotion of reversible Li+ storage in transition metal dichalcogenides by Ag nanoclusters

Abstract

After years of development, improvement in the electrochemical properties of MoS2 through structural modifications has reached its limit. Further improvements in the Li+ storage properties of MoS2 must be based on an understanding of the Li+ storage mechanism in MoS2. On this basis, we have developed a novel ternary composite of graphene, MoS2 nanosheets and a small amount (1 wt%) of silver nanoclusters (NCs; MoS2/G/Ag). The presence of the Ag NCs in the composite is, however, instrumental and serves several purposes: immobilization of sulfur, increased association with Li+ and increased spacing between graphene sheets. The presence of this small amount of Ag NCs was able to increase the Li+ storage capacity of MoS2 by 60% (with a discharge capacity of ~ 1300 mAh g-1 at 0.5 A g-1 compared with 800-850 mAh g-1 for a MoS2/graphene composite without the Ag NCs (MoS2/G)). The MoS2/G/Ag composite also exhibited a very impressive rate performance: discharge capacities of 1040 and 850 mAh g-1 at the very high current densities of 1 and 5 A g-1, respectively (the corresponding values from MoS2/G without the Ag NCs are 790 and 580 mAh g-1).