Boosting the kinetics of PF6− into graphitic layers for the optimal cathode of dual-ion batteries: The rehearsal of pre-intercalating Li+

Abstract

Large anions exhibit slow diffusion kinetics in graphite cathode of dual-ion batteries (DIBs); particularly at high current density, it suffers severely from the largely-reduced interlayer utilization of graphite cathode, which as a bottleneck limits the fast charge application of DIBs. To maximize interlayer utilization and achieve faster anion diffusion kinetics, a fast and uncrowded anion transport channel must be established. Herein, Li+ was pre-intercalated into the graphite paper (GP) cathode to increase the interlayer spacing, and then hosted for the PF6- anion storage. Combined with theoretical calculation, it shows that the local interlayer spacing enlargement and the residual Li+ reduce the anion intercalation energy and diffusion barrier, leading to better rate stability. The obtained GP with Li+ pre-intercalation (GP-Li) electrode exhibits a discharge capacity of 23.1 mAh g−1 at a high current of 1300 mA g−1. This work provides a facile method to efficiently improve the interlayer utilization of graphite cathode at large currents.