An in Situ Formed Multifunctional Interphase with High Dendrite Tolerance for Long-Life Solid-State Sodium–Metal Batteries

The development of practical solid-state sodium–metal batteries calls for simple but efficient solutions to overcome poor anode||electrolyte compatibility. Here, we for the first time, design an interphase comprised of NaCl, Sn, and Na–Sn alloy formed in situ at room temperature to stabilize the Na||Na 3 Zr 2 Si 2 PO 12 interface. Equipped with the dynamically stable, low-impedance, and dendrite-free interface, the symmetric cells demonstrate a 31-fold reduction in interfacial resistance, a high critical current density to 0.8 mA cm –2, along with a 1000-h cyclability at 25 °C. The corresponding Na||Na 3 V 2 (PO 4 ) 3 full cells showcase a capacity retention rate of 93% after 1071 cycles at 0.5 C.