Anion Intercalation into Graphite Electrode from Ethylene Carbonate Solutions Dissolving both Lithium Hexafluorophosphate and Lithium Bis(trifluoromethanesulfonyl)imide

The diluted solutions of lithium bis(trifluoromethanesulfonimide) (LiTFSI) dissolving in organic solvents (ca. ethylene carbonate (EC)) are not compatible with dual-ion batteries (DIBs) mainly by virtue of the drastic decomposition of electrolyte solutions before the reversible storage of TFSI – in graphite positive electrodes. In this work, lithium hexafluorophosphate (LiPF 6 ) is introduced into 1 M LiTFSI-EC solution to strengthen the oxidative endurance. The EC solutions with mixed salts demonstrate a synergistic effect in terms of anion storage in graphite electrode. The anion storage behavior of graphite electrode in the solutions of 1 M LiTFSI+LiPF 6 -EC is systematically investigated by conventional electrochemical tests of Li/graphite cells, in combination with ex situ / in situ X–ray diffraction measurements of graphite positive electrode and energy-dispersive spectroscopic analyses of the surface of graphite electrodes.