Rechargeable Sodium Solid-State Battery Enabled by In Situ Formed Na–K Interphase

Solid-state metal batteries have displayed great advantages in the domain of electrochemical energy storage owing to their remarkably improved energy density and safety. However, the practical application of solid-state batteries (SSBs) is still greatly impeded by unfavorable interface stability and terrible low temperature performance. In this work, a local targeting anchor strategy is developed to realize an impressively long cycling life for a NASICON-based solid-state sodium metal battery at 0 °C. With the electrochemical migration of K⁺ from the cathode side to the anode side, a spontaneous generated liquid Na–K interphase can stabilize the ceramic electrolyte/metallic Na anode interface, and address the issues of sluggish kinetics at the interface together with metal dendrite deposition. In addition, the capability of K⁺ conduction in NASICON is also theoretically and experimentally validated. Of particular note, a K₂MnFe(CN)₆ cathode paired with a Na₃Zr₂Si₂PO₁₂ ceramic electrolyte and metallic Na anode, enable the long-term cycling and excellent rate capability of all-solid-state sodium batteries at 0 °C. Without the purposely designed matrix host for a liquid Na–K interphase, this work opens up a new route for the design of high energy density SSBs.