Optimizing Interface Chemistry with Novel Covalent Molecule for Highly Sustainable and Kinetics-Enhanced Sodium Metal Batteries

Abstract

Metallic sodium has attracted increasing attention as an ideal anode material for next-generation high energy density and low-cost secondary batteries. However, it is highly desired yet remains challenging to improve their cycling stability and safety due to unstable solid electrolyte interphase and dendrite growth. Herein, a hybrid interface layer composed of Na₂Se and Na₃P is constructed on the surface of Na (Na@NPS) via in situ spontaneous reaction. The hybrid interface layer with merits of high sodiophilicity and high Na-ion conductivity can effectively induce homogeneous Na-ion flux distribution, accelerate the reaction kinetics and suppress decomposition of electrolyte components. Benefitting from the above advantages, the Na@NPS symmetric cell delivers a long cycle life (1000 h at 1 mA cm^–2 and 1 mAh cm^–2). Furthermore, the full cell coupling with Na₃V₂(PO₄)₃-based cathode provides an exceptionally long lifespan (1500 cycles) at 20 C with a capacity retention of 98.2% and high energy density (226 Wh kg^–1). Therefore, the enhanced electrochemical performance illustrates the feasibility of the covalent molecule derived hybrid multifunctional interfaces in solving the irregular deposition of Na-ion and expediting reaction kinetics in Na metal batteries.