Molecular engineering of interplanar spacing: From extended π‐conjugated system to excellent sodium dual‐ion battery

Abstract Sodium dual‐ion batteries (SDIBs) based on organic active materials have attracted extensive attention due to their low cost, environmental friendliness, high safety, and superior stability. However, limitations such as poor conductivity, high solubility in electrolytes, kinetics constraints, and low active site utilization caused by dense layer stacking impede further advancement. Herein, a sawtooth polyimide anode with wide layer spacing, abundant active sites, and an extended π‐conjugated system on nonplanar surfaces was designed through interlayer molecular engineering. The material exhibits a stable structure, fast transport and reaction kinetics, and high active‐site utilization. Proof‐of‐concept SDIBs delivered a high discharge capacity of 162.4 mAh g −1 with 200 stable cycles without degradation, robust fast‐charging capability, and a low self‐discharge rate of 0.11% h −1 . Excellent electrochemical performance with a reversible capacity of 107.6 mAh g −1 , outstanding rate capability, low polarization, and 2000 stable cycles without attenuation were achieved even at high active mass loading. Mechanistic studies reveal a dual‐storage mechanism involving diffusion and pseudocapacitance, expanding the diversity of redox‐active polymers. These findings provide new insights and theoretical guidance to designing high‐performance organic materials for Na + storage. image