In Situ Anchoring Anion‐Rich and Multi‐Cavity NiS(2) 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(2+) in the cathode material limit the development of practical Mg cathode materials. In this paper, an anion‐rich electrode material, NiS(2), and its composite with Ni‐based carbon nanotubes (NiS(2)/NCNTs) are explored as the cathode materials for Mg‐ion batteries. These NiS(2)/NCNTs with excellent Mg(2+) storage property is synthesized by a simple in situ growth of NiS(2) nanoparticles on NCNTs. NiS(2) 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(2+). With the aid of 3D NCNTs skeleton as the transport channel of the electron, the NiS(2)/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 NiS(2) and NiS(2)/NCNTs and are elucidated for fundamental understanding.