Abstract: 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.

Key words: Rechargeable magnesium batteries, CTAB-VS₄, Sulfur vacancies, Expanded interlayer spacing, Stabilized Mg anode