Solvation structure fine-tuning enables high stability sodium metal batteries

Abstract

Unstable solid electrolyte interface (SEI) films, disordered growth of sodium dendrites and relatively large volume expansion of metal sodium are huge bottlenecks for the safety and stability of sodium metal batteries (SMBs). Herein, 2-propyn-1-ol methanesulfonate (PMS) has been proposed as a preferential anode film-forming additive to stabilize Na‖Na₃V₂(PO₄)₃ (NVP) batteries. Molecular dynamics simulations indicate that PMS additive can actively induce the solvation behavior of fluoroethylene carbonate (FEC), effectively suppressing further decomposition of solvent molecules. Moreover, in situ optical experiments, scanning electron microscopy, and X-ray photoelectron spectroscopy indicate that PMS and FEC synergistically construct a SEI film rich in inorganic components such as NaF and Na₂S, significantly inhibiting the growth of sodium dendrites. Consequently, Na‖NVP full cells in 3 vol% PMS electrolyte exhibit ultra-high average coulombic efficiency of 99.9% and a capacity retention rate of 92% after 1000 cycles at 2C. This work offers an optimistic prospect for achieving safe and stable SMBs.