Solvent-Guided Morphology Optimization Strategy in the VS₄@(NH₄)₂V₆O₁₆ Cathode for High-Performance Zn-Ion Batteries

Rechargeable aqueous zinc-ion batteries (RAZIBs) are considered to be one of the most promising options for future grid energy storage devices because of their high theoretical/volumetric capacity, inherent safety, and cost-effectiveness. However, due to a lack of appropriate cathode materials with suitable electrolytes and the sluggish intercalation kinetics associated with Zn 2+, the RAZIB’s performance is impeded. The layered VS 4 @(NH 4 ) 2 V 6 O 16 cathode is constructed through a facile hydrothermal process by adding ethylene glycol in different ratios without a surfactant. The optimized VS 4 @(NH 4 ) 2 V 6 O 16 is used as the cathode material, and 2 M Zn(OTf) 2 in a water/acetonitrile mixture is used as the electrolyte for better cycling performance in RAZIBs. The assembled RAZIB showed a high specific capacity of ∼354 mA h g –1 and a high energy density of ∼244.3 W h kg –1 at a current density of 0.3 A g –1, considering the weight of the cathode material. It has retained ∼51% capacity after 30,000 cycles when cycled with a specific current of 20 A g –1 . The conversion and insertion/extraction mechanism of Zn 2+ in the VS 4 @(NH 4 ) 2 V 6 O 16 cathode was investigated using various physicochemical techniques. This work paves the way for choosing the appropriate cathode material and electrolyte composition for high-performance RAZIBs.