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Rechargeable magnesium batteries are of considerable interest due to their high theoretical capacity, and they are projected as good alternates for stationary energy storage and electric vehicles. Sluggish Mg2+ kinetics and scarce availability of suitable cathode materials are major issues hindering the progress of rechargeable magnesium batteries. Herein, a conjugated, off-planar, two-dimensional (2D) polymer is explored for reversible magnesium storage. The polymer cathode reveals high capacity and high cycling stability with high rate capability. Replacing the Mg metal anode with the Mg alloy, AZ31 further enhances the ion storage performance. At a high current density of 2 A g–1, stable capacity is shown for almost 5000 cycles with 99% Coulombic efficiency. A composite of carbon nanotube with the polymer delivers capacity values higher (>1.5 times) than that of a pristine polymer at a current density of 2 A g–1 and shows cycling up to 5 A g–1. Electrokinetic studies reveal a contribution of pseudocapacitive nature, and the mechanism is investigated by ex situ X-ray photoelectron spectroscopy and infrared spectroscopy. The use of 2D polymer electrodes opens up opportunities for developing high-rate, high-capacity, and stable rechargeable magnesium ion batteries.

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.

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A cost-effective quinone-pyrrole conjugated polymer is utilized as electrode for non-aqueous Al, Zn and Li-ion batteries. Reversible capacities of 120 mAh g-1 at 50 mA g-1 for Al-ion batteries and...