A High-Power Rechargeable Sodium-Ion Full Battery Operating at −40 °C

High-power-density rechargeable batteries are highly indispensable for power-intensive application scenarios, such as vehicle start-stop system and grid-level frequency regulation. However, realizing high-power-density alkali-ion batteries is challenging especially at low temperatures, as undesirable alkali metal plating tends to occur more easily on the anode surface due to the increased electrochemical impedance and polarization. Herein, a low-temperature, high-power-density rechargeable Na₃V₂(PO₄)₃ ||hard carbon (HC) sodium-ion full battery without Na plating is realized by electrolyte regulation. The designed high-solvation-entropy electrolyte enables a high ionic conductivity of 13.87 mS cm⁻¹ at −40 °C. More importantly, the enhanced contact-ion pairs solvation structure induces an anion-derived, thin, NaF-rich solid electrolyte interface (SEI) on HC anodes with low interfacial resistance to ensure facile Na⁺ diffusion through the SEI. Consequently, the assembled sodium-ion full battery demonstrates a record-high power density of 1132.31 W kg⁻¹ (with an energy density of 61.94 Wh kg⁻¹) at −40 °C and 13372.56 W kg⁻¹ (132.83 Wh kg⁻¹) at 25 °C (based on total mass of the active materials on anode and cathode). This work will expedite the development of sodium-ion batteries for power-intensive applications in extreme environments.