Hybridizing Tetraglyme to Aqueous Electrolyte with Concentrated Salts Promote Intercalation of Anions on Graphite Cathode in Dual-Ion Battery

The amount of support salt in electrolytes determines the capacity of a dual-ion battery (DIB), and highly concentrated electrolytes are required for developing the high energy density DIB. In this study, hybrid aqueous tetraglyme (G4) electrolyte is investigated to develop high energy density aqueous DIB that is composed of carbon and Mo₆S₈ for cathode and anode, respectively. Impedance measurement reveals that introduced G4 increases the activation energy of the anode; however, decreases the activation energy for anion intercalation into the carbon cathode. This decreases the activation energy resulted from the G4 molecule strongly solvated to Li⁺ resulting in weakening anion trapped in “contact ion pair” in concentrated aqueous electrolyte. So, hybrid G4-aqueous electrolyte is useful for better electrochemical intercalation of anion. In addition, this hybrid electrolyte is highly stable by formation of stable solid electrode–electrolyte interphase on Mo₆S₈ anode and discharge capacity of 37 mAh g⁻¹, and 72% retained capacity after 500 cycles with a high average coulombic efficiency of 93% is achieved.