Sulfur vacancy-carbon modification synergy boosts the electrochemical performance of self-standing VS2 cathodes in aqueous zinc-ion batteries

Abstract

Vanadium disulfide, featuring a layered structure with large interlayer spacing, emerges as a promising cathode material for aqueous zinc-ion batteries. However, its practical application is still constrained by sluggish Zn²⁺ diffusion kinetics, structural instability, and severe side reactions during repeated cycling in aqueous electrolytes. Herein, a self-supported carbon-modified VS₂ composite (C–VS₂@SS) is in situ synthesized on stainless steel mesh via a hydrothermal method. The C–VS₂ nanosheets show oriented growth and a uniform flower-like morphology, whose open structure boosts electrolyte contact and electron/ion transport. Aberration-corrected electron microscopy reveals a uniform amorphous carbon layer on its surface and abundant in-plane sulfur vacancies; the carbon layer constructs a conductive network while sulfur vacancies optimize charge distribution and lower the ion migration barrier, and their synergy reduces the electron-ion transport resistance effectively. Density functional theory (DFT) calculations confirm that sulfur vacancies enhance the electronic conductivity of C–VS₂@SS, optimize the Zn²⁺ migration pathways, and improve the Zn²⁺ diffusion kinetics. With a mass loading of 1.29 mg cm⁻², C–VS₂@SS delivers a high capacity of 225 mAh g⁻¹ at 100 mA g⁻¹, retains 171.2 mAh g⁻¹ at 2 A g⁻¹, and maintains 85.9% of the initial capacity after 650 cycles. Notably, even at an elevated loading of 9.75 mg cm⁻², it exhibits excellent rate performance, demonstrating its great practical application potential.