Rechargeable Solid-State Na-Metal Battery Operating at −20 °C

Achieving satisfactory performance for a solid-state Na-metal battery (SSNMB) with an inorganic solid electrolyte (SE), especially under freezing temperatures, poses a challenge for stabilizing a Na-metal anode. Herein, this challenge is addressed by utilizing a Natrium super ionic conductor (NASICON) NASICON-type solid electrolyte, enabling the operation of a rechargeable SSNMB over a wide temperature range from −20 to 45 °C. The interfacial resistance at the Na metal/SE interface is only 0.4 Ω cm² at 45 °C and remains below 110 Ω cm² even at −20 °C. Remarkably, long-term Na-metal plating/stripping cycles lasting over 2000 h at −20 °C are achieved with minimal polarization voltages at 0.1 mA cm⁻². Further analysis reveals the formation of a uniform Na_3−xCa_xPO₄ interphase layer at the interface, which significantly contributes to the exceptional interfacial performance observed. By employing a Na₃V_1.5Al_0.5(PO₄)₃ cathode, the full battery system demonstrates excellent adaptability to low temperatures, exhibiting a capacity of 80 mA h g⁻¹ at −20 °C over 50 cycles and retaining a capacity of 108 mAh g⁻¹ (88.5% of the capacity at 45 °C) at 0 °C over 275 cycles. This research significantly reduces the temperature threshold for SSNMB operation and paves the way toward solid-state batteries suitable for all-season applications.