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

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 by preserving 29 times of the capacity retention rate after standing for 24 hours, compared to the battery with a commonly used carbonate solvent. 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.