Anionic TeO₃^2- doped CoS nanomaterials for high-performance magnesium-ion battery cathode materials

Rechargeable magnesium-ion batteries (RMBs) exhibit distinct advantages, such as superior theoretical capacity, economic viability, and enhanced safety features, making them a promising alternative to traditional energy storage systems. Nevertheless, the current research of high-performance RMBs is still fraught with many shortcomings of the unexpected actual capacity, poor cycling stability rapid energy decay, and a relatively short lifespan. Herein, Grape-bunch CoS/Te materials are prepared by one-step metal sulfide template-free anion-doped solvent-thermal synthesis. The as-prepared material displays a well-defined skeletal structure, which maximizes electrolyte-electrode interaction and shortens Mg²⁺ migration pathways. Besides, the CoS/Te composites exhibit lattice expansion because of anionic TeO₃^2- doping manifested as widening of the lattice spacing, which significantly reduces the resistance to the interlayer movement of Mg²⁺, thus contributing to improvement of the reaction kinetics of magnesium storage in RMBs. The anion-doped CoS-based composites not only weaken Mg²⁺-cathode electrostatic interactions but also provide numerous active sites, accelerating magnesium storage kinetics. The conversion reaction energy barrier is significantly reduced through Te incorporation in CoS, with reaction kinetics being simultaneously optimized, which contributes to enhanced capacity retention, superior rate performance, and prolonged cycling stability. The electrochemical storage mechanism of converted Mg²⁺ was revealed by characterization. Therefore, this study offers a practical and viable approach for elevating the Mg²⁺ storage performance of modified CoS nanomaterials, which is expected to be applicable and generalizable to other electrode materials.