Solvent‐derived Fluorinated Secondary Interphase for Reversible Zn‐graphite Dual‐ion Batteries

Abstract

Abstract The irreversibility of anion intercalation‐deintercalation is a fundamental issue in determining the cycling stability of a dual‐ion battery (DIB). In this work, we demonstrate that using a partially fluorinated carbonate solvent can drive a beneficial fluorinated secondary interphase layer formation. Such layer facilitates reversible anion (de−)intercalation processes by impeding solvent molecule co‐intercalation and the associated graphite exfoliation. The enhanced reversibility of anion transport contributes to the overall cycling stability for a Zn‐graphite DIB—a high Coulombic efficiency of 98.5 % after 800 cycles, with an attractive discharge capacity of 156 mAh g −1 and a mid‐point discharge voltage of ≈1.7 V (at 0.1 A g −1 ). In addition, the formed fluorinated secondary interphase suppresses the self‐discharge behavior, preserving 29 times of the capacity retention rate compared to the battery with a commonly used carbonate solvent, after standing for 24 hours. This work provides a simple and effective strategy for addressing the critical challenges in graphite‐based DIBs and contributes to fundamental understanding to help accelerate their practical application.