PF<sub>6</sub><sup>–</sup> Intercalation into Graphite Electrode from Propylene Carbonate
Dandan Zhu, Huiqing Fan, Hongyu Wang
Abstract
LiPF6-propylene carbonate (PC) solutions show some compatibility with the graphite positive electrode in dual-ion batteries. The relationship between the anion storage capacity and LiPF6 concentration is investigated by galvanostatic charge–discharge tests. Ex situ X-ray diffraction (XRD) measurements are carried out on graphite electrode recovered from Li/graphite cells at the end of charge to probe the storage situation of PC-solvated PF6– inside graphite electrode. In situ XRD measurements on Li/graphite cells are performed to trace the crystal structural changes of anion–graphite intercalation compounds. Electrochemical quartz crystal microbalance (EQCM) measurement is conducted on graphite electrode to evaluate the transport of solvent during the anion storage. Nuclear magnetic resonance (NMR) and infrared (IR) spectroscopic studies on the solutions reveal the interactions between ions and PC solvent. The electrochemical performance of graphite is correlated with solvation state of LiPF6-PC solution.