Converting a low-cost industrial polymer into organic cathodes for high mass-loading aqueous zinc-ion batteries

Abstract

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, 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 a high 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.