Formation of NaF-Rich Solid Electrolyte Interphase on Na Anode through Additive-Induced Anion-Enriched Structure of Na+ Solvation

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)(2)O2F full cells with high Coulombic efficiency (97 %) and capacity retention (91 %) after 200 cycles.

Automated summary

By employing an additive strategy, the decomposition of PF6- and the formation of a stable NaF-rich solid electrolyte interphase (SEI) were achieved, resulting in the inhibition of dendrite growth on high-capacity sodium (Na) anodes. The use of electrolytes containing 4-acetylpyridine (4-APD) enabled excellent cycling performance and stability.