A Multifunctional Interphase Layer Enabling Superior Sodium‐Metal Batteries under Ambient Temperature and −40 °C

The sodium (Na)-metal anode with high theoretical capacity and low cost is promising for construction of high-energy-density metal batteries. However, the unsatisfactory interface between Na and the liquid electrolyte induces tardy ion transfer kinetics and dendritic Na growth, especially at ultralow temperature (-40 °C). Herein, an artificial heterogeneous interphase consisting of disodium selenide (Na2 Se) and metal vanadium (V) is produced on the surface of Na (Na@Na2 Se/V) via an in situ spontaneous chemical reaction. Such interphase layer possesses high sodiophilicity, excellent ionic conductivity, and high Young's modulus, which can promote Na-ion adsorption and transport, realizing homogenous Na deposition without dendrites. The symmetric Na@Na2 Se/V cell exhibits outstanding cycling life span of over 1790 h (0.5 mA cm-2 /1 mAh cm-2 ) in carbonate-based electrolyte. More remarkably, ab initio molecular dynamics simulations reveal that the artificial Na2 Se/V hybrid interphase can accelerate the desolvation of solvated Na+ at -40 °C. The Na@Na2 Se/V electrode thus exhibits exceptional electrochemical performance in symmetric cell (over 1500 h at 0.5 mA cm-2 /0.5 mAh cm-2 ) and full cell (over 700 cycles at 0.5 C) at -40 °C. This work provides an avenue to design artificial heterogeneous interphase layers for superior high-energy-density metal batteries at ambient and ultralow temperatures.