Additive-rejuvenated anions (De)intercalation into graphite cathode enables optimum dual-ion battery

Cathode-electrolyte interphase (CEI) has particular function in maintaining electrolyte and cathode stability. However, the CEI will also cause some negative effects on ion transport. It is crucial for optimizing the structure of CEI through additives in the electrolyte to improve the electrode reaction. In this study, we proposed using C3H3FO3 (FEC) as an additive to optimize an aqueous LiTFSI (bistrifluoromethanesulfonimide lithium salt) electrolyte. The incorporation of FEC modified the solvation structure of TFSI–, inhibit the formation of CEI with thicker size, thereby facilitating the intercalation of TFSI– into the selected graphite cathode. Consequently, the graphite's discharge capacity was doubled, reaching 47 mAh g−1. The influence of TFSI– solvation structure on CEI formation was further studied by the emerging correlative SEM, Raman imaging and TOF-SIMS techniques and theoretical calculation techniques. Using this optimization strategy, we successfully constructed an aqueous dual-ion battery using C24H10N2O4 and graphite as the anode and cathode with an impressive potential window of 2.55 V, which delivered the energy density of 66 Wh kg−1 at the power density of 128 W kg–1.