Poly(ethylene oxide)- and Polyzwitterion-Based Thermoplastic Elastomers for Solid Electrolytes

Area of Science:

• Polymer Science
• Materials Science
• Electrochemistry

Background:

• Solid polymer electrolytes (SPEs) are crucial for developing safer and more efficient lithium-ion batteries.
• Triblock copolymers offer tunable properties for advanced material applications.
• Poly(ethylene oxide) (PEO) based electrolytes face challenges in ionic conductivity and mechanical strength.

Purpose of the Study:

• To synthesize and characterize novel ABA triblock copolymers (tri-BCPs) with a PEO middle block and PVPS outer blocks.
• To investigate the effect of PVPS content and LiTFSI doping on the microphase separation and thermal properties of the tri-BCP/LiTFSI hybrids.
• To evaluate the potential of these PVPS-b-PEO-b-PVPS/LiTFSI hybrids as solid electrolytes for lithium-ion batteries.

Main Methods:

• Synthesis of PVPS-b-PEO-b-PVPS triblock copolymers.
• Doping of tri-BCPs with lithium bis-(trifluoromethane-sulfonyl) imide (LiTFSI).
• Characterization using small-angle X-ray scattering (SAXS) to study microphase separation.
• Thermal analysis (melting temperature, glass transition temperature) and mechanical property assessment.
• Ionic conductivity measurements.

Main Results:

• All tri-BCPs formed asymmetric lamellar structures with PVPS volume fractions between 12.9% and 26.1%.
• Microphase separation strength increased with PVPS fraction but decreased with doping ratio, impacting thermal properties.
• PVPS-b-PEO-b-PVPS/LiTFSI hybrids exhibited higher modulus and ionic conductivity compared to PEO/LiTFSI hybrids.
• Enhanced ionic conductivity was attributed to PVPS blocks aiding Li+ ion dissociation.

Conclusions:

• PVPS-b-PEO-b-PVPS triblock copolymers doped with LiTFSI show promising properties as solid electrolytes.
• The polyzwitterionic outer blocks contribute to improved mechanical strength and ionic conductivity.
• These materials hold potential for use in next-generation lithium-ion batteries.