Stabilized Solid–Solid Interface for Solid-State Sodium Batteries Using Gradient Ion-Electron Conductive Phases Modified Sodium Metal Anode

The application of sodium anodes is essential for developing high-energy density, low-cost, and high-security solid-state sodium–metal batteries (SSSMBs) to replace commercial lithium ion batteries. However, poor interface contact, high resistance, and dendrite growth between the sodium anode and solid-state electrolyte (SSE) have hampered the application of SSSMBs. Herein, an ultrastable composite sodium anode with gradient ion-electron conductive phases was constructed through the in situ conversion and alloying reaction between SbF 3 and sodium. The tightly contacted solid–solid interface between the composite anode and sodium superionic conductor oxide SSE is enriched with NaF and inside the anode is enriched with Na 3 Sb, which can inhibit the growth of sodium dendrites and accelerate the transport of bulk-phase sodium to the interface. Benefiting from these advantages, both symmetric and full cells assembled with such composite electrodes display excellent electrochemical performance. These results offer a novel composite anode design for the practical application of SSSMBs.