Electrolyte Solvation Structure Regulation for Low-Temperature Sodium-Ion Battery

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• High-performance sodium-ion batteries (SIBs) are crucial for grid-scale energy storage.
• Low-temperature performance of SIBs is hindered by sluggish Na+ desolvation kinetics, causing rapid capacity decay.
• Current electrolyte formulations struggle to maintain stability and efficiency in sub-zero environments.

Purpose of the Study:

• To develop a novel electrolyte system for SIBs that ensures effective operation at low temperatures.
• To address the challenge of Na+ desolvation and improve the electrochemical stability of SIBs in cold conditions.
• To enhance the capacity retention and cycling stability of SIBs at temperatures as low as -40 °C.

Main Methods:

• Formulation of a new electrolyte based on diethylene glycol dimethyl ether (DEGDME) with 1,3-dioxane (DOL) as a cosolvent and trimethylsilyl isocyanate (Si-NCO) as an additive.
• Optimization of the electrolyte's solvation structure to enhance the participation and stability of PF6- anions.
• Electrochemical testing of Na||HC half-cells and full cells (O3-type NFMN//HC) at -40 °C to evaluate capacity retention and cycling performance.

Main Results:

• The designed electrolyte significantly improved low-temperature performance, with the Na||HC half-cell retaining 88.57% of its room-temperature capacity at -40 °C.
• Excellent cycling stability was achieved, showing 94.50% capacity retention after 100 cycles in the half-cell at -40 °C.
• The full cell (NFMN//HC) demonstrated a capacity retention of 83.73% after 100 cycles at -40 °C, highlighting the electrolyte's practical applicability.

Conclusions:

• The developed electrolyte formulation effectively enhances the electrochemical stability of SIBs at low temperatures.
• The optimized solvation structure, involving increased PF6- anion participation, is key to overcoming low-temperature performance limitations.
• This research offers valuable insights for designing advanced electrolytes for next-generation SIBs operating in extreme cold environments.