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

Abstract

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 PF 6 À in the Na + solvation sheath to facilitate PF 6 À 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 j j Na cells show excellent cycling performance over 360 h at 1.0 mA cm À 2 . Meanwhile, excellent stability is also achieved for Na j j Na 3 V 2 -(PO 4 ) 2 O 2 F full cells with high Coulombic efficiency (97 %) and capacity retention (91 %) after 200 cycles.

Bimetallic Borate Ni2FeBO5 as a High-Performance Anode for Sodium-Ion Batteries

“…First, a part of the active material is unavailable because a part of the active material leaves the conductive network (Figure g). Second, the electrolyte is constantly consumed due to the continuous formation of an SEI film on the newly exposed surface generated by the rupture of the active material . Therefore, the capacity of the Ni 2 FeBO 5 electrode decays due to severe volume expansion.…”

“…To explore the reasons for capacity fading, the morphological evolution of the Ni 2 FeBO 5 electrode during different active material. 51 Therefore, the capacity of the Ni 2 FeBO 5 electrode decays due to severe volume expansion.…”

Recent advances of structural/interfacial engineering for Na metal anode protection in liquid/solid-state electrolytes

“…With the 1.0 wt% addition of 4-APD, the Na/Na symmetric battery delivered a long cycling life for over 360 h at 1.0 mA cm −1 . 107 Besides, Cui et al proved that NaF can protect the Na anode by adding NaPF 6 into the ether-based electrolyte, forming an SEI film composited of Na 2 O and NaF on the surface (Fig. 6a).…”

Towards stable electrode–electrolyte interphases: Regulating solvation structures in electrolytes for rechargeable batteries

“…[94,95] Besides, it was recently reported that additives could increase the concentration of electrolyte anions in the solvation sheath, and indirectly promote the decomposition of anion at the anode for forming an inorganic-rich SEI, rather than a direct film-formation process on the anode. [98,99] For example, the additive of 4-acetylpyridine (4-APD) with an electron-withdrawing acetyl group can induce the formation of an anion-rich solvation structure of Na + , thereby the 4-APD facilitates the formation of a NaFenrich SEI and effectively suppresses the growth of Na dendrites [96] (Figure 7C,D). Additionally, introducing a superior anion additive into the solvation sheath is also a viable strategy.…”