Improving Electrolyte Sustainability for Sodium-Ion Capacitors by Combining a Bio-Based Solvent With a Low-Fluorine...

Area of Science:

• Materials Science
• Electrochemistry
• Green Chemistry

Background:

• Sodium-ion capacitors (SICs) are promising energy storage devices.
• Current SIC electrolytes often rely on non-sustainable components.
• There is a need for eco-friendly electrolyte alternatives.

Purpose of the Study:

• To develop and evaluate a sustainable electrolyte for SICs.
• To investigate the performance of a novel electrolyte based on sodium difluoro(oxalato)borate (NaDFOB) and γ-Valerolactone (GVL).
• To compare different presodiation strategies for the new electrolyte system.

Main Methods:

• Formulation of a novel electrolyte: 1 mol L^-1 NaDFOB in GVL.
• Fabrication and testing of SIC full-cells using the new electrolyte.
• Comparison with a conventional electrolyte (1 mol L^-1 NaPF₆ in EC:PC).
• Evaluation of in situ and ex situ presodiation strategies.
• Analysis of the solid-electrolyte interphase (SEI) using X-ray photoelectron spectroscopy (XPS).

Main Results:

• The NaDFOB/GVL electrolyte demonstrated performance comparable to the conventional NaPF₆/EC:PC system in SIC full-cells.
• Both in situ oxidation of sodium squarate and ex situ electrochemical presodiation yielded similar results.
• XPS analysis indicated significant variations in SEI composition based on the presodiation method.

Conclusions:

• A sustainable electrolyte formulation for SICs has been successfully developed.
• The novel electrolyte offers a viable, high-performance alternative to conventional systems.
• Presodiation strategy significantly influences the SEI formation, impacting device performance.