Converting a Low-Cost Industrial Polymer into Organic Cathodes for Practical Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) using organic cathodes have emerged as a sustainable energy storage technology benefitting from high safety, low cost and abundant feedstocks. However, most organic cathodes are n-type polyaromatic compounds and conjugated polymers, which require sophisticated synthesis and provide a low operational voltage and slow Zn2+ diffusion kinetics. Herein, we report access to p-type radical polymer cathodes from a commercially available poly(methyl vinyl ether-alt-maleic anhydride) (poly(MVE-alt-MA)) polymer. The modification of poly(MVE-alt-MA) with 4-amino-TEMPO produces radical polymers (PTEMPO) that are easily scalable to tens of grams. The corresponding polymer AZIBs deliver a capacity of 92 mAh g-1 at 10 C with 95% capacity retention over 1000 cycles. Importantly, the electrode composites and battery assembly procedure are optimised so that no fluoro-containing electrolytes and binders are needed, and cheap carbon additives can be used. We assemble the Swagelok batteries, small pouch and large pouch batteries with mass loading of 7.8 to 50 mg cm-2, demonstrating nearly 100% coulombic efficiency. The pouch battery with 0.8-0.9 g of active polymer displayed a 60-mAh capacity with 1.5 V operational voltage. This work paves the way for simple and practical implementation of polymer AZIBs for real-world applications.