Designing electrolyte with multi-ether solvation structure enabling low-temperature sodium Ion capacitor

Abstract Sodium-ion hybrid capacitors (SICs) combine the high energy density of batteries with the high power density and long cycle life of capacitors, are considered promising next-generation energy storage devices. To adapt to the demands of high-altitude cold regions, the performance of SICs in low-temperature environments is crucial. The desolvation process of Na + and the transport process in the solid electrolytr interphase (SEI) are determinant for the low-temperature performance of SICs. In this paper, we proposed a multi-ether modulation strategy to construct a solvation sheath with multi-ether participation by modulating the coordination of Na + and solvents. This unique solvation sheath not only reduces the desolvation energy barrier of Na + , but more importantly forms a Na 2 O-rich inorganic SEI and enhances the ionic dynamics of Na + . Benefiting from the excellent solvation structure design, SICs prepared with this electrolyte can achieve energy density of up to 178 Wh/kg and ultra-high power density of 42 390 W/kg at room temperature. More importantly, SIC deliver a record-high energy densities of 149 Wh/kg and 119 Wh/kg as well as power densities of up to 25 200 W/kg and 24 591 W/kg at -20 °C and -40 °C, respectively. This work provides new ideas for the development of high-performance SICs for low-temperature operating environments.