Interface Stable Kinetics Triggered by Interfacial Built-In Electric Field in Solid-State Sodium-Metal Battery

Solid-state sodium-metal batteries (SSSBs) have emerged as a potential next-generation energy storage technology due to their abundant resource, high energy density, and safety. However, the uncontrolled Na dendrite growth and low charging/discharging rate pose a severe constraint on their practical applications. Herein, high interfacial sodium-ion diffusion performance and interface stability of Na anode are achieved in SSSBs by designing an interfacial built-in electric field (IBEF) driven by a laminated hybrid solid electrolyte with a mixed-ion/electron-conducting layer. The electrochemical characterizations and density functional theory (DFT) calculations reveal that IBEF effectively improves interfacial sodium-ion diffusion by reinforcing electron delocalization and decreasing Na + transfer energy barrier. Furthermore, finite element simulation and experiments indicate that the IBEF endows a uniform interfacial charge distribution and Na deposition during plating/stripping. The IBEF boosts the cyclability of solid-state symmetric cells, enabling ultralong cycle life over 26 400 cycles at 0.1 mA cm −2 , the Na/Na 3 V 2 (PO 4 ) 3 (NVP) full cells display a remarkable capacity retention of 97.4% after 1500 cycles at 2.0 C and stable charging/discharging even at −20 °C. Na/NVP pouch cells exhibit a capacity of 65.7 mAh g −1 after 50 cycles under 0.19 mA g −1 .