Fusion of Nitro Isomers of Naphthoquinone Enhances Capacity and Cyclability in Zn-ion Batteries

Abstract

Aqueous Zn-ion batteries (ZIBs) are promising alternatives to lithium-ion batteries because of their inherent safety, raw material abundance (10 million metric tons of zinc in India and Australia is the second largest zinc producer), and cost-effectiveness. This study focuses on utilising redox-active organic materials with quinone moiety, namely 5- and 6-nitro 2,3-dichloro 1,4-naphthoquinone (5-DCNNQ) and (6-DCNNQ), and their mixtures in a 3:1 ratio as cathode materials for aqueous ZIBs. While the introduction of the nitro group reduces the solubility of active material in the electrolyte, the isomer mixture DCNNQmix cathode, with the high voltage feature of 5-DCNNQ and the high capacity feature of 6-DCNNQ, exhibited a higher capacity and cyclability than either material on their own. The battery retained its capacity even after 9600 charge-discharge cycles.