Robust Artificial Interlayer with High Ionic Conductivity and Mechanical Strength toward Long-Life Na-Metal Batteries

Sodium metal, benefiting from its high theoretical capacity and natural abundance, is regarded as a promising anode for sodium-metal batteries (SMBs). Unfortunately, the uncontrollable sodium dendrites formation caused from the sluggish ion-transport kinetics and fragile solid electrolyte interphase (SEI) interlayer induces a low Coulombic efficiency and poor cycling stability. Constructing an artificial SEI interlayer with high ionic conductivity, stability, and mechanical toughness is an effective strategy for Na-metal anode, yet it still presents major challenge for high current density and long cycling life. Herein, an artificial SEI interlayer composed of Na-Sn alloy, Sn, and Na₂Te (denoted as NST) is designed via in-situ conversion/alloying reaction of tin telluride (SnTe) with Na. Such artificial interlayer possesses rapid Na⁺-transport kinetics and high Young's modulus (5.3 GPa), benefitting to even Na plating/stripping and suppressing Na dendrite growth. Owing to these merits, the symmetrical Na/NST cell presents an ultralong cycle life span over 1390 h with a small voltage hysteresis at 1 mA cm^-2 with 1 mAh cm^-2. And the Na₃V₂(PO₄)₃ (NVP)||Na/NST full cell exhibits a prolonged life of 1000 cycles with a high-capacity retention of 88% at 5C. Herein, a promising strategy is provided to construct a high-performance artificial interlayer for SMBs.