Highly stable cathode materials for aqueous Zn ion batteries: Synergistic effect of pre-inserted bimetallic ions in vanadium oxide layer.

Aqueous Zn ion batteries with cost-effectiveness, high safety, and eco-friendliness have a great potential as an excellent substitute for non-aqueous cells for large-scale energy storage. However, the intercalation of Zn2+ ions in the cathode materials is challenging and complex due to the sluggish diffusion kinetics of Zn2+ ions. Herein, the highly reversible Zn ion battery based on vanadium oxide nanobelts has been developed by using pre-inserted bimetallic ions (Na+ and Ca2+ ions) within the vanadium oxide layer (NCVO) as the cathode and Zn(CF 3 SO 3) 2 solution as an electrolyte. Vanadium oxide nanobelts which were calcined at 350 °C (NCVO-350) deliver the superior cycle stability with a capacity retention rate close to 100% after 200 cycles at 0.5 A g−1, and 92% retention is also achieved after 3000 cycles at 10 A g−1. The ultrahigh capacity retentions at low/high current densities are attributed to the pre-inserted bimetallic ions within the layers to enhance the structural stability of the vanadium oxide nanobelts. Moreover, the low-cost electrode material preparation process will accelerate the industrialization of aqueous Zn ion batteries. [Display omitted] • A simple solution impregnation method at ambient conditions is proposed. • The conversion of vanadium-based materials from nanoparticles to nanobelts. • Amorphous structure of electrode also can enhance Zn-storage performances. • Bimetallic ions nanobelts exhibit promising electrochemical performance. [ABSTRACT FROM AUTHOR]