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.