Sodium metal is a promising anode for high-energy-density
sodium
rechargeable batteries (RSBs). However, the low Coulombic efficiency
(CE) of the Na plating/stripping process and the problem of safety
hinder their practical application. Herein, we report a facile strategy
for employing the fluorinated phosphate solvents to realize highly
reversible Na plating/stripping and improve the safety performance.
The fluorinated phosphate molecules reduce the polarity of the solvent
and lower the coordination number to Na+, which makes it
possible to form the anion-induced ion–solvent-coordinated
(AI-ISC) structures with high reduction tolerance. Moreover, the fluorination
treatment enhances the oxidation resistance of the phosphate solvent,
enabling compatibility with the high-voltage Na3V2(PO4)2F3 (NVPF) cathode. As expected,
the Na@Al//NVPF full cell with the as-prepared 0.9 M NaFSI/tris(2,2,2-trifluoroethyl)
phosphate (TFEP) demonstrates a capacity retention of 83.4% after
200 cycles with an average CE of 99.6%. This work opens a new avenue
for designing high-energy-density RSBs with improved safety performance.
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