Improving the Long-Term Cycling Stability of Sodium Metal Anodes with LiBF₄ Additives

The lower redox potential and higher theoretical specific capacity of the sodium metal anode make sodium metal batteries highly promising. However, the uneven plating/stripping behavior of sodium resulted in the growth of sodium dendrites and the decrease in Coulombic efficiency (CE). In this study, LiBF₄ was used as an additive in an ether-based electrolyte. Theoretical calculations and experimental results demonstrate that the introduction of Li⁺ facilitates the formation of an electrostatic shielding effect and induces Na⁺ deposition, while the decomposition of BF₄^- forms inorganic salts such as NaF, which contribute to the formation of an ideal solid electrolyte interphase (SEI). The Na||Na symmetric battery with the addition of LiBF₄ achieved stable cycling for 3000 h at a current density of 1.0 mA cm^-2. This study demonstrates the efficacy of LiBF₄ as an electrolyte additive for sodium metal batteries, providing new insights into the advancement of sodium-based energy storage systems.