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

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Sodium metal batteries offer high theoretical capacity but suffer from dendrite formation and low Coulombic efficiency due to uneven sodium plating/stripping.
• Developing stable sodium metal anodes is crucial for next-generation energy storage solutions.

Purpose of the Study:

• To investigate the efficacy of lithium tetrafluoroborate (LiBF4) as an electrolyte additive for improving sodium metal anode performance.
• To elucidate the mechanism by which LiBF4 addition influences sodium ion deposition and solid electrolyte interphase (SEI) formation.

Main Methods:

• Theoretical calculations were performed to understand ion interactions and deposition mechanisms.
• Experimental studies utilized Na||Na symmetric batteries with LiBF4-containing ether-based electrolytes.
• Electrochemical performance, including cycling stability and Coulombic efficiency, was evaluated.

Main Results:

• LiBF4 addition facilitated the formation of an electrostatic shielding effect by Li+, guiding uniform Na+ deposition.
• Decomposition of BF4- led to the formation of NaF, contributing to an ideal SEI layer.
• Na||Na symmetric batteries with LiBF4 additive achieved stable cycling for 3000 hours at 1.0 mA cm-2.

Conclusions:

• LiBF4 is an effective electrolyte additive for stabilizing sodium metal anodes in batteries.
• The combined effects of Li+ shielding and NaF-rich SEI formation are key to enhancing battery performance.
• This research provides valuable insights for developing high-performance sodium-based energy storage systems.