CTAB-induced VS4 yolk-shelled microspheres with sulfur vacancies for enhanced magnesium storage

To address the challenges of rapid capacity decay and limited cycle life in rechargeable magnesium batteries (RMBs), which are primarily caused by slow Mg²⁺ diffusion kinetics and structural collapse of the cathode material, we propose a strategy integrating cationic surfactant with metal compounds. A sulfur vacancy-rich CTAB-VS₄ composite with yolk-shell structure is successfully synthesized by in-situ introduction of cationic surfactant cetyltrimethylammonium bromide (CTAB). The CTAB modification achieves a multifunctional “one stone, three birds” effect: (1) Expanding the interlayer spacing and inducing rich sulfur vacancies, the diffusion rate of Mg²⁺ and the magnesium storage sites are increased. (2) Constructing a yolk-shell structure with a high specific surface area, providing ample active sites for accommodating Mg²⁺. (3) Reducing the interface impedance, optimizing the electronic structure, and stabilizing the Mg anode. Consequently, the CTAB-VS₄ cathode exhibits exceptional electrochemical performances in RMBs, delivering high discharge specific capacities of 258 and 173 mAh g⁻¹ at 0.5 and 3 A g⁻¹ after 180 and 700 cycles, respectively. Systematic characterizations confirm the reversible Mg²⁺ intercalation mechanism. This synergistic modulation through cationic surfactant provides a promising pathway toward high-performance RMBs.