Improved Reversibility of PF6– De/intercalate in Graphite by Building the Artificial PVDF-HFP Polymer Cathode Electrolyte Interphase

As a typical cathode for Li-dual ion batteries (Li-DIBs), though graphite can store anions, the high working voltage up to 4.5 V vs Li+/Li brings about low Coulombic efficiency (CE), unsatisfactory cyclability, and fast battery failure. Here, we demonstrate that the graphite with an artificial PVDF-HFP polymer cathode electrolyte interphase (CEI) layer can effectively suppress electrolyte decomposition, improve the CE, and stabilize the graphite structure in the progress of PF6– de/intercalation. Such a CEI-reinforced graphite cathode shows prolonged cyclability with a 76% capacity retention ratio after 1000 cycles at a cutoff potential of 5.2 V versus Li+/Li and more attractive rate performance. This work displays a feasible method for developing Li-DIBs with satisfactory cycle stability and high power performance.