Microwave-induced defect-rich vanadium sulfide cathodes for highly reversible electrochemical magnesium storage

Vanadium sulfide (VS₄) demonstrates the most prospect as the cathode materials for rechargeable magnesium battery due to its special one-dimensional linear crystal structure. However, VS₄ cathode still suffers from sluggish kinetics, irreversible structural change, short cycle life, and low capacity. Herein, a microwave-induced synthesis method is presented to fabricate VS₄ nanosheets with rich sulfur vacancies and high V³⁺/V⁴⁺ ratio. When serviced as the cathode material for rechargeable magnesium battery, the VS₄ nanosheets display excellent electrochemical performances with large specific capacity of 701 mAh/g at 200 mA g⁻¹ current density. In addition, the VS₄ nanosheets cathodes also show long-term operating stability over 600 cycles at 1.0 A/g current density with only 0.3 % capacity decay per cycle. Our experimental results show that the improved electrochemical reaction kinetics is ascribed to the defect-rich structure and the reversible anionic redox reactions between S²⁻/S₂²⁻ of the VS₄ nanosheets. This work offers a meaningful way to design high-performance Mg²⁺ ion storage cathode materials with favorable diffusion kinetics.