Understanding Polymerized Ionic Liquids as Solid Polymer Electrolytes for Sodium Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• Solid polymer electrolytes (SPEs) offer a flexible and cost-effective alternative for sodium-based batteries.
• Challenges in SPEs include achieving high ionic conductivity and robust mechanical properties.

Purpose of the Study:

• To investigate an AB diblock copolymer, PS-PEA(BuImTFSI), as a solid polymer electrolyte for sodium batteries.
• To explore binary and ternary electrolyte systems incorporating salt and ionic liquid for enhanced performance.

Main Methods:

• Differential scanning calorimetry (DSC) to analyze thermal properties and phase separation.
• Electrochemical analysis of ionic conductivity and Na/Na symmetrical cells.
• Spectroscopic analysis to understand ion-polymer interactions.

Main Results:

• The addition of salt and ionic liquid enhanced ionic conductivity through plasticization and weakened anion-polymer interactions.
• Stable sodium plating/stripping was observed in Na/Na symmetrical cells at 70 °C and high current densities.
• A Na|NaFePO4 cell demonstrated excellent capacity retention and Coulombic efficiency at elevated temperatures and varying rates.

Conclusions:

• Solvent-free diblock copolymer electrolytes show significant potential for high-performance sodium-based energy storage.
• Tailoring electrolyte composition can optimize ionic conductivity and electrochemical stability.
• This work contributes to the development of advanced materials for next-generation batteries.