Vat Orange 11—Based Organic Cathode Material for High Rate Rechargeable Magnesium Battery

Abstract

Mg-ion batteries are of immense interest owing to their dendrite free chemistry, low cost and high energy density and often comparable to the existing Li-ion batteries. Organic molecules as electrodes, are well-explored in alkali metal ion batteries as they are less expensive, environment friendly and amenable to redox potential-tuning. But these molecules are rarely used for secondary Mg-ion batteries and they continue to attract attention. In the present studies, an organic dye, vat orange 11, is explored as a cathode material for non-aqueous secondary Mg-ion battery in different electrolytes. The electrolyte with salt-controlled dissolution approach turns out to be very good in terms of capacity recovery with long cycle life. It shows an excellent rate performance up to a discharge current of 4000 mA g−1 with high cycling stability (1000 cycles at 500 mA g−1 current density). Further, high capacity and high rate performance are observed using a non-nucleophilic electrolyte based on an ionic liquid. The possible mechanism of Mg2+ uptake is studied using ex situ FTIR spectroscopy that shows a transformation between carbonyl (–C=O) and enolate (–C=O−) functional groups during charge-discharge cycles. The present studies initiate the use of vat-based dye molecules in rechargeable Mg-ion batteries.