Balancing Defects and Microcrystals in Carbon Anodes by Molecular Chemistry Method for Sodium‐Ion Batteries

Carbon materials with large capacity and low potential serve as promising anode materials for sodium‐ion batteries (SIBs). Carbon defects offer active sites for sodium storage but sacrifice reversibility, whereas carbon microcrystals improve conductivity but may suffer from low capacity. Herein, the balance between defects and microcrystals is realized by the molecular chemistry method of cross‐linking and defect repairing. Real‐time spectroscopic analyses reveal that the decomposition of tetrabromophthalic anhydride (TBPA) molecule induces the dehydrogenation of pitch to release small gas molecules to form pseudo‐closed pores, followed by the cross‐linking of C═O bonds in TBPA with the dehydrogenated pitch to form C─O─C bonds and thus suppress the excessive microcrystal growth. Meanwhile, the decomposition products of TBPA can also react with the dehydrogenated pitch to repair carbon defects. Thanks to the microstructure balance, the as‐synthesized carbon material exhibits a smoother ion mass transfer channel (d(002) = 0.386 nm, La = 4.56 nm) and a larger storage space (Vpseudo‐closed pore = 0.086 cm3 g−1) than the pitch carbon (PC, d(002) = 0.349 nm, La = 5.90 nm, Vpseudo‐closed pore = 0.041 cm3 g−1), increasing the capacity from 162.5 to 336.5 mAh g−1. This work sheds a chemical light on regulating carbon material microstructure for advanced SIBs. A defect and microcrystal balanced strategy is proposed to regulate carbon microstructure for improving the sodium‐ion battery performance. Tetrabromophthalic anhydride (TBPA) promotes the dehydrogenation of pitch, which exhibits an electron‐rich state and can react with the positively charged TBPA derivatives to repair carbon defects. Meanwhile, the crosslinking of C═O in TBPA with pitch to form C─O─C can suppress the excessive microcrystal growth.