In Situ Anchoring Anion‐Rich and Multi‐Cavity NiS2 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 Mg2+ in the cathode material limit the development of practical Mg cathode materials. In this paper, an anion-rich electrode material, NiS2 , and its composite with Ni-based carbon nanotubes (NiS2 /NCNTs) are explored as the cathode materials for Mg-ion batteries. These NiS2 /NCNTs with excellent Mg2+ storage property is synthesized by a simple in situ growth of NiS2 nanoparticles on NCNTs. NiS2 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 Mg2+ . With the aid of 3D NCNTs skeleton as the transport channel of the electron, the NiS2 /NCNTs exhibit a high capacity of 244.5 mAh g-1 at 50 mA g-1 and an outstanding rate performance (94.7 mAh g-1 at 1000 mA g-1 ). It achieves capacitance retention of 58% after 2000 cycles at 200 mA g-1 . Through theoretical density functional theory (DFT) calculations and a series of systematic ex situ characterizations, the magnesiation/demagnesiation mechanisms of NiS2 and NiS2 /NCNTs and are elucidated for fundamental understanding.