Hierarchical\nIntercalation of Solvated Tetrafluoroborate\nAnions into Graphite Electrodes: The Case Studies of Methyl Acetate\nand γ‑Butyrolactone Solutions

Intercalation\nof anions unlocks graphite as a positive material\nin energy storage devices, and the performance could be affected by\nsolvents in solutions. In this context, it is vital to investigate\nthe role of solvents in anion intercalation. Herein, a hierarchical\nintercalation phenomenon, in which different graphite intercalation\ncompounds are generated in the same solution, is studied in lithium\ntetrafluoroborate (LiBF<sub>4</sub>) solutions of carboxylate ester\nsolvents γ-butyrolactone (GBL) and methyl acetate (MA). The\nevolution modes of the graphite cathode structure during electrochemical\nintercalation and deintercalation are discussed via in situ X-ray\ndiffraction (XRD) measurements. Based on this, the relationship between\nGICs and potentials, together with concentrations, is compared in\ndetail. Furthermore, various graphite materials with different surface\nproperties are applied to adjust the anions’ solvation status\ninside graphite sheets.