Construction of molybdenum vanadium oxide/nitride hybrid nanoplate arrays for aqueous zinc-ion batteries and reliable insights into the reaction mechanism

Abstract

Vanadium(V)-based cathode materials hold great potential for rechargeable aqueous zinc-ion batteries (AZIBs). However, the shortcomings of poor electrical conductivity, large volume changes, serious V dissolution and the complicated electrochemical reaction mechanism seriously restrict their practical applications. Herein, we demonstrate the synthesis of unique amorphous Mo–V–O and Mo–V–N hybrid nanoplate arrays directly grown on a carbon cloth substrate (CC@a-MVO/MVN HNPAs) as an additive- and binder-free cathode for AZIBs. This electrode design offers multiple advantages including high electrical conductivity, abundant active sites, favorable ion diffusion kinetics and robust mechanical stability. As expected, the CC@a-MVO/MVN cathode exhibits outstanding performance in terms of high discharge capacity (1.06 mA h cm⁻² at a current density of 0.5 mA cm⁻²), good rate capability (0.67 mA h cm⁻² at 10 mA cm⁻²) and exceptional long-term cycle stability (94% capacity retention at 6 mA cm⁻² for 2000 cycles). Furthermore, flexible soft-packaged AZIBs are successfully assembled to demonstrate their ability for practical applications. More importantly, various ex situ characterization studies reliably demonstrate the reversible formation/decomposition of two different kinds of zinc-containing byproducts, which could correspond to the H⁺/Zn²⁺ co-insertion mechanism. This study might contribute to the rational development of V-based cathode materials for high-performance AZIBs and provide reliable insights into the reaction mechanism.