Tunable Free-Standing Core-Shell CNT@MoSe2 Anode for Lithium Storage.

Abstract

Heterogeneous nanostructuring of MoSe2 over a carbon nanotube (CNT) sponge as a free-standing electrode not only brings higher performance but also eliminates the need for dead elements such as a binder, conductive carbon, and supportive current collectors. Further, the porous CNT sponge can be easily compacted via an intense densification of the active material MoSe2 to produce an electrode with a high mass loading for a significantly improved areal capacity. In this work, we present a tunable coating of MoSe2 on a CNT sponge to fabricate a core-shell MoSe2@CNT anode. The three-dimensional nanotubular sponge is synthesized via a solvothermal process, followed by thermal annealing to improve crystallization. Structural and morphological studies revealed that MoSe2 grew as a layered structure ( d = 0.66 nm), where numbers of layers can be controlled to yield optimized results for Li+ storage. We showed that the 10-layer core-shell CNT@MoSe2 hybrid sponge delivered a discharge capacity of 820.5 mAh g-1 after 100 cycles at 100 mA g-1 with a high cyclic stability and rate capability. Further, an ex situ structural and morphological analysis revealed that ionic storage causes a phase change in MoSe2 from a crystalline to a partial amorphous state for a continuous increase in the capacity with extended cycling. We believe that the strategy developed here will assist users to tune the electrode materials for future energy-storage devices, especially how the materials are changing with the passage of time and their effects on the device performance.