In dual-ion batteries (DIBs) utilizing organic electrolyte solutions, the combinations of electrolyte salt and solvent serve as a determiner of the electrochemical performance of graphite electrode partially because solvent participates in the anion intercalation procedure. In this case, every solvated–anion@graphite intercalation compound possesses the characteristic intercalated gallery height. However, in Li/graphite DIBs with concentrated LiTFSI (lithium bis(trifluoromethanesulfonimide))–alkyl phosphates (ca. trimethyl, triethyl, tripropyl, tributyl phosphate) solutions, solvated–TFSI–@graphite intercalation compounds have the nearly identical intercalated gallery height of about 0.803 nm, which may be mainly attributed to both the big size of TFSI– anion and the rigid PO4 framework of these alkyl phosphate solvents.
Graphical The height of intercalation : Lithium difluoro(oxalato)borate is introduced to LiBF 4 -sulfolane (SL) solutions for dual-ion batteries, and the graphite electrodes’ storage behavior of anions is studied. Each anion can intercalate into graphite with SL, and different intercalation gallery heights are formed. Intermediate height is not observed, and species inside graphite are determined. Some previous studies have found the synergistic effect of mixed anions in dual-ion batteries (DIBs). In this work, both lithium tetrafluoroborate (LiBF 4 ) and lithium difluoro(oxalato)borate (LiDFOB) were dissolved in sulfolane (SL) solvent, and the resultant solutions were applied for DIBs. The storage behavior of mixed anions in natural graphite positive electrodes was investigated. In-situ X-ray diffraction measurements revealed both anions could participate in the formation of graphite intercalation compounds. Their evolution followed with the decreasing tendency of discharge capacities as the content of LiDFOB increased in solutions. The exchange of anions was discussed.
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