Intermolecular Interaction‐Induced Polarity Modulation of Carbonate Electrolyte for Fast‐Kinetics Hard Carbon Anodes in Durable Sodium‐Ion Batteries

ABSTRACT Traditional carbonate‐based electrolytes are prevailing for high‐performance sodium ion batteries (SIBs), yet the resultant sluggish kinetics of Na + is undesirable when paired with hard carbon (HC) anode. Herein, we propose a solvent polarity modulating strategy via introducing intermolecular interactions and design a carbonated‐based electrolyte which can achieve rapid Na + storage in the HC anode. The introduced co‐solvent with electron‐withdrawing effect reduces the electron density of the carbonyl in cyclic carbonates. This attenuates the coordination ability of high‐polarity solvents and facilitates PF 6 − entering the solvation shell. The modulated solvation structure reduces the Na + de‐solvation energy barrier, enhancing the Na + storage kinetics of the HC anode. Moreover, the decreased polarity mitigates the continuous reduction of solvents triggered by Lewis acid catalyzation, rendering a stable cycle life of the HC anode over 400 cycles with capacity retention of 90.4%. Furthermore, a practical high voltage HC||Na 3 V 2 (PO 4 ) 2 O 2 F cell with a controlled negative/positive capacity ratio of 1.05 and a reversible capacity of 110.5 mAh g −1 further reveals the effectiveness of the designed electrolyte. This work offers a strategic approach to innovating carbonate‐based electrolytes for practical applications of SIBs.