Zincophilic and hydrophobic group grafting vanadyl phosphate cathode for high performance zinc ion batteries

Abstract

VOPO₄, as one of the most potential cathodes for AZIBs, suffered from the heavy decomposition and dissolution in aqueous electrolytes during cycling, thus sabotaging the merits of its cyclability and high working potential. Free water in internal Helmholtz layer seems to be one of the main causes to this problem. Thereby, this paper intends to regulate the structure of internal Helmholtz layer by introducing small organic molecule on VOPO₄ (VPS), which might restrain the erosion of free water and change the storage mode of Zn²⁺. Specifically, hydrophobic groups from the small organic molecule effectively hinder the approach of H₂O, while zincophilic groups from the small organic molecule enhance diffusion kinetics of Zn²⁺. Benefitting from this strategy, VPS exhibits a high discharge capacity of 145 mAh g⁻¹ at 0.2 A g⁻¹ and advanced cycling durability for over 1000 cycles at 1 A g⁻¹. This study provides new insights into the modification direction for improving the development of VOPO₄.