In Situ Self‐Nanostructuring Enables Fast‐Recharging of an Aqueous‐Processed Organic Small Molecule Cathode

ABSTRACT Redox‐active organic materials (ROMs) for batteries are emerging as sustainable alternatives to inorganic cathode materials. However, the development of high‐performance organic cathodes faces challenges of a trade‐off between insolubilizing ROMs for high stability and maintaining their processability. This balance is essential to fabricate uniformly blended electrodes without the formation of large agglomerates, which is crucial for high capacity utilization and rate capability. Herein, we present a small‐molecule organic cathode material, 1,3,5‐tris(3‐vinyl‐10H‐phenoxazin‐10‐yl)benzene (V3PXZ), that overcomes this limitation by forming insoluble network polymers through in situ electrochemical crosslinking in the cell after electrode fabrication from a soluble active material. To this end, V3PXZ is delicately designed to undergo a novel electrochemical coupling reaction, forming nonconjugated polymeric structures without generating any by‐products. Notably, the in situ electrochemical coupling during the cell operation not only yields insoluble crosslinked polymers of V3PXZ but also unexpectedly forms nanostructures with high surface area in the electrode. This self‐nanostructuring behavior of V3PXZ enables us to prepare aqueous‐processed V3PXZ cathodes, achieving exceptionally high cycling stability and rate capability (charging 56% of capacity in 36 s) even with high active content (>70 wt.%).