Regulating Solvent Molecule Coordination with KPF6 for Superstable Graphite Potassium Anodes.

Abstract

Graphite is one of the most attractive anode materials due to its low cost, environmental friendliness, and high energy density for potassium ion batteries (PIBs). However, the severe capacity fade of graphite anodes in traditional KPF6-based electrolyte hinders its practical applications. Here, we demonstrate that the cycling stability of graphite anodes can be significantly improved by regulating the coordination of solvent molecules with KPF6 via a high-temperature precycling step. In addition to the solvents being electrochemically stable against reduction, a stable and uniform organic-rich passivation layer also forms on the graphite anodes after high-temperature precycling. Consequently, the PIBs with graphite anodes could operate for more than 500 cycles at 50 mA g-1 with a reversible capacity of about 220 mAh g-1 and an average Coulombic efficiency greater than 99%. Furthermore, full batteries based on Prussian blue cathodes and high-temperature precycled graphite anodes also exhibit excellent performance. Molecular dynamics simulations were performed to explore the solvation chemistry of the electrolytes used in this study.