Radical Oligomer-Grafted Cellulose as Cathodes for Sustainable Aqueous Zinc-Ion Batteries

Organic electroactive materials are widely used in aqueous zinc-ion batteries (AZIBs) due to their versatility in chemical modification for enhanced electrochemical performance. Redox-active polymers (RAPs) are particularly appealing because of their low solubility, which reduces capacity fading, and their amorphous structures enable easier processing and faster ion diffusion compared to crystalline electrode materials. Current RAPs employed in AZIBs are primarily conjugated aromatic polymers or aliphatic polymers with CC bonds, which can potentially contribute to microplastic pollution at the end of the battery's life. In this work, natural cellulose is selected as the parent polymer and, through chemical grafting, introduced radical oligomers to afford cellulose-g-oligo(TEMPO) as electroactive materials for AZIBs. Chemical characterizations confirm the successful synthesis of targeted polymer electrode materials with a theoretical capacity of 100 mAh g^-1. The electrochemical performance of the AZIBs demonstrates that the cell can deliver a voltage of 1.55 V, an initial capacity of 73 mAh g^-1, and retains 88% of its capacity after 1000 cycles. This work showcases the potential use of natural polymers as electroactive materials for more sustainable AZIBs.