Hexafluorophosphate-Bis(trifluoromethanesulfonyl)imide anion co-intercalation for increased performance of dual-carbon battery using mixed salt electrolyte

Abstract Co-intercalation of Hexafluorophosphate(PF6ˉ) and Bis(trifluoromethane sulfonyl)imide (TFSIˉ) anions as a result of the use of a mixed salt of LiPF6 and LiTFSI is studied for the increased performance of a dual-carbon battery (DCB). Unlike the fluorine- or the imide-based anions (e.g., PF6ˉ and TFSIˉ), the cluster formation between co-intercalated PF6ˉ and TFSIˉ in the positive electrode of a DCB results in achieving high discharge capacities with significantly increased cycle properties. A reversible discharge capacity of 85 mAh/g-cathode over 350 cycles with no significant degradation is presented. The Coulombic efficiency of almost 100% is reached after the initial 10 cycles and suitable rate property is also observed. F NMR analysis on graphitic carbon intercalated with PF6ˉ and TFSIˉ suggests the interaction between two anions and ratio of intercalated PF6− and TFSI− was changed by applied voltage, resulting in the increased stability of the intercalated structure which is also supported by the first principles calculations.