Fabrication of Nitrogen-Doped Carbon-Coated NiS_1.97 Quantum Dots for Advanced Magnesium-Ion Batteries

Magnesium (Mg) batteries have garnered considerable interest because of their safety characteristics and low costs. However, the practical application of Mg batteries is hindered by the slow diffusion of Mg ions in the cathode materials. In this study, we prepared NiS 1.97 quantum dot composites with nitrogen doping and carbon coating (NiS 1.97 QDs@NC) using a one-step sulfurization process with NiO QDs/Ni@NC as the precursor. We applied the prepared NiS 1.97 QDs/Ni@NC-based cathodes to Mg batteries because of the large surface area of the quantum dot composite, which provided abundant intercalation sites. This design ensured efficient deintercalation of magnesium ions during charge–discharge processes. The fabricated NiS 1.97 QDs@NC displayed a high reversible Mg storage capacity of 259.1 mAh g –1 at 100 mA g –1 and a good rate performance of 96.0 mAh g –1 at 1000 mA g –1 . Quantum dot composites with large surface areas provide numerous embedded sites, which ensure effective deintercalation of Mg ions during cycling. Thus, the proposed cathode synthesis strategy is promising for Mg-ion-based energy storage systems.