Engineered nitrogen doping on VO2(B) enables fast and reversible zinc-ion storage capability for aqueous zinc-ion batteries

Abstract

Vanadium-based compounds with high theoretical capacities and relatively stable crystal structures are potential cathodes for aqueous zinc-ion batteries (AZIBs). Nevertheless, their low electronic conductivity and sluggish zinc-ion diffusion kinetics in the crystal lattice are greatly obstructing their practical application. Herein, a general and simple nitrogen doping strategy is proposed to construct nitrogen-doped VO2(B) nanobelts (denoted as VO2-N) by the ammonia heat treatment. Compared with pure VO2(B), VO2-N shows an expanded lattice, reduced grain size, and disordered structure, which facilitates ion transport, provides additional ion storage sites, and improves structural durability, thus presenting much-enhanced zinc-ion storage performance. Density functional theory calculations demonstrate that nitrogen doping in VO2(B) improves its electronic properties and reduces the zinc-ion diffusion barrier. The optimal VO2-N400 electrode exhibits a high specific capacity of 373.7 mA h g−1 after 100 cycles at 0.1 A g−1 and stable cycling performance after 2000 cycles at 5 A g−1. The zinc-ion storage mechanism of VO2-N is identified as a typical intercalation/de-intercalation process.