Epitaxial growth of NiCo2S4/Co9S8@Graphene heterogenous nanocomposites with high-rate lithium storage performance.

Constructing heterogeneous nanocomposite has attracted much attention for energy storage devices due to the fact that heterogeneous structure can boost charge transfer owing to the built-in-charge transfer driving force. Herein, a unique architecture for hetero-NiCo 2 S 4 /Co 9 S 8 nanocompiste anchored on Graphene (NiCo 2 S 4 /Co 9 S 8 @G) has been prepared by an epitaxial mechanism. The as-synthesized NiCo 2 S 4 /Co 9 S 8 @G electrode exhibits 662 and 490 mAh g −1 capacity at the first discharge/charge cycle and can be maintained at 323 mAh g −1 after 4000 cycles (from 2nd cycle only 0.008% decay per cycle) at an ultrahigh current density of 10 A g −1 . Moreover, NiCo 2 S 4 /Co 9 S 8 @G electrode can be full charged within 11 s while still achieving a specific capacity of 133 mAh g −1  at a current density of 40 A g −1 . This fascinating high-rate capability is attributed to the pseudo-capacitance contribution which can be further verified by kinetics model. This pseudo-capacitance originating from hetero structure sheds new light on the development of high-rate performance anode materials. [ABSTRACT FROM AUTHOR]