Oriented-Redox Induced Uniform MnO2 Coating on Ni3S2 Nanorod Arrays as a Stable Anode for Enhanced Performances of Lithium Ion Battery.

Cost-effective transition metal chalcogenides have aroused wide consideration as alternative anode materials in lithium ion batteries (LIBs) on account of their elevated lithium activity and considerable theoretical capacity. However, the significant challenge caused by the large volume change and shuttle effect of polysulfides during Li ion insertion/extraction severely restricts their practical application. In this work, the uniform MnO2 coating layer with a tunable thickness on Ni3S2 nanorod arrays has been achieved through a mild oriented-redox reaction by taking advantage of the mixing valence of Ni in Ni3S2 [(Ni2+)2(Ni0)(S2-)2]. The core/shell structured nanorod arrays directly used as anode materials of LIBs demonstrate remarkably improved lithium storage performance including high rate capacity and long cycle life, which deliver a discharge capacity of 662 mA h g-1 for 150 cycles at 0.5 C, corresponding to an elevated capacity retention of 90.7%. The improved electrochemical performances can be assigned to the generation of stable solid electrolyte interface films and suppression of the shuttle behavior with the protection of the MnO2 coating layer on Ni3S2 nanorod arrays.