Designing Solid Electrolyte Interfaces towards Homogeneous Na Deposition: Theoretical Guidelines for Electrolyte...

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Metallic sodium anodes are promising for large-scale energy storage but suffer from unstable solid electrolyte interphase (SEI) and dendrite growth, causing short circuits and poor cycle life.
• Developing a stable SEI is crucial for safe and efficient sodium metal batteries.

Purpose of the Study:

• To identify an ideal SEI composition for suppressing sodium dendrite growth.
• To engineer a stable, sodium bromide-rich SEI layer using an electrolyte additive.
• To improve the cycling performance and stability of sodium metal anodes.

Main Methods:

• Phase field and ab initio molecular dynamics simulations were used to predict the ideal SEI composition.
• 1,2-dibromobenzene (1,2-DBB) was introduced as an additive to a fluoroethylene carbonate-based electrolyte.
• Electrochemical performance of Na||Na3V2(PO4)3 cells with the modified electrolyte was evaluated.

Main Results:

• Sodium bromide (NaBr) was identified as the SEI component with the lowest Na ion diffusion energy barrier, promoting spherical Na deposition.
• The 1,2-DBB additive successfully constructed a NaBr-rich, mechanically stable SEI layer.
• The modified electrolyte enabled an extraordinary capacity retention of 94% after 2000 cycles at 10 C in Na||Na3V2(PO4)3 cells.

Conclusions:

• The study presents a design philosophy for achieving dendrite-free sodium metal anodes through SEI engineering.
• The use of 1,2-DBB as an electrolyte additive is a viable strategy for enhancing the stability and cycle life of sodium metal batteries.
• This approach holds potential for application in other metal anode systems for energy storage.