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 NaClO 4 and trimethoxy(pentafluorophenyl)silane (TPFS) as dual additives (DA). The ClO 4 - 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 PF 6 - anion solvation sheath for reducing PF 6 -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||Na 3 V 2 (PO 4 ) 2 O 2 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.