Regulating SEI Components of Sodium Anode via Capturing Organic-Molecule Intermediates in Ester-Based Electrolyte

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Sodium metal anodes are crucial for high-energy-density batteries but face challenges with dendrite growth and unstable solid electrolyte interphase (SEI) in ester-based electrolytes.
• Controlling SEI composition is key to achieving stable sodium metal anodes, yet actively tuning these components remains difficult.

Purpose of the Study:

• To introduce a functional electrolyte additive, 2-chloro-1,3-dimethylimidazoline hexafluorophosphate (CDIH), to regulate SEI components in ester-based electrolytes.
• To improve the stability and reversibility of sodium metal anodes for enhanced battery performance.

Main Methods:

• Incorporation of CDIH additive into a fluoroethylene carbonate (FEC)/propylene carbonate (PC) electrolyte.
• Utilizing molecular dynamic simulations and experimental analysis to investigate SEI formation and composition.
• Testing Na||Na symmetrical cells and Na||PB full cells to evaluate electrochemical performance.

Main Results:

• CDIH additive promotes the formation of a NaF/NaCl-rich SEI layer by reacting chloride with FEC decomposition products.
• CDIH effectively captures organic intermediates, reducing unstable organic components within the SEI.
• Na||Na symmetrical cells demonstrated excellent long-term cycling (>800 h) and rate performance (0.5-4 mA cm⁻²).
• Na||PB full cells exhibited outstanding electrochemical performance with minimal polarization.

Conclusions:

• The CDIH additive successfully regulates SEI composition, leading to highly reversible sodium deposition.
• This strategy significantly enhances the cycling stability and rate capability of sodium metal anodes in ester-based electrolytes.
• The developed approach offers a promising pathway for advancing sodium-ion battery technology.