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 PF₆ ^- 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||Na₃V₂(PO₄)₂O₂F 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.