Owing to the anion-enriched effect induced by 4-acetylpyridine (4-APD) additive, more PF6
− could enter the inner Na+ solvation sheath to be decomposed into NaF on the Na anode surface, which could effectively repress the Na dendrite growth and boost the cycling performance of Na-metal batteries.
High-capacity sodium (Na) anodes suffer from dendrite growth due to the high reactivity, which can be overcome through inducing a stable NaF-rich solid electrolyte interphase (SEI). Herein, we propose an additive strategy for realizing the anion-enriched structure of Na+ solvation to obtain a NaF-rich SEI. The electron-withdrawing acetyl group in 4-acetylpyridine (4-APD) increases the coordination number of PF6
− in the Na+ solvation sheath to facilitate PF6
− to decompose into NaF. Thus, the NaF-rich SEI with high mechanical stability and interfacial energy is formed to repress the growth of Na dendrites. With the 4-APD-contained electrolyte, the symmetric Na||Na cells show excellent cycling performance over 360 h at 1.0 mA cm−2. Meanwhile, excellent stability is also achieved for Na||Na3V2(PO4)2O2F full cells with high Coulombic efficiency (97 %) and capacity retention (91 %) after 200 cycles.Zum Volltext