Organometallic Polymer Constructed by Active Fe−C12N8 Centers for Boosting Sodium‐Ion Storage

Abstract Organic‐metal coordination materials with rich structural diversity are considered as promising electrode materials for rechargeable sodium‐ion batteries. However, the electrochemical performance can be constrained by the limited number of active sites and structural instability under the discharge/charge process. Herein, organometallic polymer microspheres (Fe‐PDA‐220) with a unique d‐π conjugated structure was designed and successfully constructed through a simple synchronous polymerization and coordination reactions. Polymerization of phenylenediamine was initiated by Fe 3+ and Fe 2+ ions generated synchronously during the polymerization integrated with poly‐aminoquinone chains to form Fe−C 12 N 8 active centers. Used as electrode materials for sodium‐ion batteries, the distinctive Fe−C bond significantly boosts the structural stability, and the π‐d conjugation system could facilitate electron transfer. A high reversible capacity of 345 mAh g −1 was delivered at 0.1 A g −1 and a capacity of 106 mAh g −1 was maintained even after discharged/charged at 1.0 A g −1 for 5000 cycles, outperforming most reported coordination materials. Spectroscopic and electronic analyses revealed that a two‐electron reaction occurred per active unit, accompanied by the reversible redox evolution of the C=N groups and Fe ions during the sodiation/desodiation. This work provides a promising and efficient strategy for boosting the electrochemical performance of organic electrode materials by the design of organometallic polymers.