In Situ Anchoring Anion-Rich and Multi-Cavity NiS Nanoparticles on NCNTs for Advanced Magnesium-Ion Batteries.

Magnesium (Mg)-ion batteries with low cost and good safety characteristics has attracted a great deal of attention recently. However, the high polarity and the slow diffusion of Mg in the cathode material limit the development of practical Mg cathode materials. In this paper, an anion-rich electrode material, NiS , and its composite with Ni-based carbon nanotubes (NiS /NCNTs) are explored as the cathode materials for Mg-ion batteries. These NiS /NCNTs with excellent Mg storage property is synthesized by a simple in situ growth of NiS nanoparticles on NCNTs. NiS with both a large regular cavity structure and abundant sulfur-sulfur (SS) bonds with high electronegativity can provide a large number of active sites and unobstructed transport paths for the insertion-disinsertion of Mg . With the aid of 3D NCNTs skeleton as the transport channel of the electron, the NiS /NCNTs exhibit a high capacity of 244.5 mAh g at 50 mA g and an outstanding rate performance (94.7 mAh g at 1000 mA g ). It achieves capacitance retention of 58% after 2000 cycles at 200 mA g . Through theoretical density functional theory (DFT) calculations and a series of systematic ex situ characterizations, the magnesiation/demagnesiation mechanisms of NiS and NiS /NCNTs and are elucidated for fundamental understanding.