Highly Oxidation-Resistant Electrolyte for 4.7 V Sodium Metal Batteries Enabled by Anion/Cation Solvation Engineering

Sodium metal batteries (SMBs) are considered as promising battery system due to abundant Na sources. However, poor compatibility between electrolyte and cathode severely impedes its development. Herein, we proposed an anion/cation solvation strategy for realizing 4.7 V resistant SMBs electrolyte with NaClO₄ and trimethoxy(pentafluorophenyl)silane (TPFS) as dual additives (DA). The ClO₄ ^- can rapidly transfer to the cathode surface and strongly coordinate with Na⁺ to form stable polymer-like chains with solvents. Meanwhile, TPFS can preferentially enter into the PF₆ ^- anion solvation sheath for reducing PF₆ -solvent interaction and effectively scavenge adverse electrolyte species for protecting electrode electrolyte interphases. Thus, such electrolyte elevates the oxidative stability of carbonate electrolytes from 3.77 to 4.75 V, and enables Na||Na₃ V₂ (PO₄ )₂ O₂ F (NVPF) battery with a capacity retention of 93 % and an average Coulombic efficiency (CE) of 99.6 % after 500 cycles at 4.7 V.