Uniform Na Metal Plating/Stripping Design for Highly Reversible Solid‐State Na Metal Batteries at Room Temperature

Solid-state alkaline metal batteries are highly sought out for their improved energy density and security over the current lithium-ion batteries. However, their practical application is heavily hindered by the interfacial issues originating from the solid electrolyte/electrode mismatch. This work demonstrates that a CuO coating layer as an active interphase can thoroughly promote the intimate contact between a Na3 Zr2 Si2 PO12 solid electrolyte and a Na metal anode through an in situ conversion reaction. The resultant Cu/Na2 O matrix forms a mixed electron/ion conducting scaffold, which facilitates stable and homogeneous Na metal plating without dendrite formation. Moreover, the symmetric Na metal cell realizes impressively steady plating/stripping cycles for 5000 h even under a high current density of 0.3 mA cm-2 . The novelty is further manifested as a room-temperature solid-state Na metal full battery of Na3 V1.5 Al0.5 (PO4 )3 |CuO@NZSPO|Na is assembled and exhibits a highly reversible cyclability (99.85% coulombic efficiency and 99.0% capacity retention) under a charge/discharge rate of 5 C for 2250 cycles. This work effectively solves the interfacial issues at the Na metal/solid electrolyte interface and provides a convenient way toward high-performance solid-state Na metal batteries operated at room temperature.