Ultrafast Upgrading of Aniline-Based Redox-Active Organics via Electrolyte-Triggered In-Situ Polymerization for Advanced Magnesium-Ion Batteries

Abstract Organic electrodes are promising as next-generation energy storage materials owing to their diverse structures, low mass, and environmental friendliness. Nevertheless, the dissolution and degradation of organic active species in electrolytes are remaining obstacles to their authentic commercialization. Herein, we report an instantaneous in-situ upgrading strategy to convert aniline-based organic cathode materials, e.g., 1-aminoanthraquinone (1-AAQ) and 1,5-diaminoanthraquinone (1,5-DAAQ), into poly(1-aminoanthraquinone) (PAAQ) and poly(1,5-diaminoanthraquinone) (PDAAQ) in a magnesium-ion battery simply by dropping the electrolyte during battery assembly without extra operations. The marvelous chemistry is essentially a chemical polymerization process of aniline-based compounds featuring the dehydrogenation of -NH 2 , the aromatization of radical cations, and the rapid free radical reaction triggered by the electrolyte containing magnesium bis(hexamethyldisilazide) (Mg(HMDS) 2 ) as an initiator. Impressively, due to the π-conjugated polymer chain with inhibited dissolution, high conductivity, and improved stability, the as-obtained PDAAQ delivered a high specific capacity (254 mAh g − 1 at 100 mA g − 1 ), superior rate performance (83 mAh g − 1 at 2000 mA g − 1 ), and excellent cycling stability for over 8000 cycles accompanied by an average capacity decay of only 0.0026% per cycle. Detailed characterizations deeply investigate the kinetic behavior and confirm the reversible magnesiation/de-magnesiation mechanism of PDDAQ. This study demonstrates an intriguing in-situ chemical-polymerization synthetic approach for preparing aniline-based organic electrode materials that compromise structure optimization and synthetic efforts, offering great promise for high-performance and sustainable multivalent-ion secondary batteries.