Lewis Acid-Base Effects on Molecular Structure and Charge Density in Solid Polymer Electrolytes for Solid-State...

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• Solid polymer electrolytes (SPEs) are crucial for developing safer solid-state batteries (SSBs).
• Current SPEs face limitations in ionic conductivity, mechanical properties, and electrochemical stability.
• Lithium salt choice significantly impacts SPE performance.

Purpose of the Study:

• To investigate how different lithium salt formulations affect the properties of PVDF-HFP based SPEs.
• To analyze the influence of lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and their binary mixture on SPE characteristics.
• To correlate molecular structure and charge density with overall SPE performance.

Main Methods:

• Synthesis of PVDF-HFP based SPEs with varying lithium salt compositions (LiFSI, LiTFSI, binary mixture).
• Comprehensive characterization including crystallinity analysis, dehydrofluorination degree assessment, and ionic conductivity measurements.
• Evaluation of mechanical strength and electrochemical stability window.

Main Results:

• Lithium salt formulation significantly alters SPE crystallinity, dehydrofluorination, and ionic conductivity.
• The binary salt mixture demonstrated improved ionic conductivity (4.93 × 10^-4 S/cm at 20°C) and mechanical strength (127 MPa).
• The binary salt mixture also exhibited a broad electrochemical stability window.

Conclusions:

• Strategic selection of lithium salts, particularly binary mixtures, can substantially enhance SPE performance.
• Optimized SPEs using tailored salt formulations are promising for next-generation solid-state batteries.
• This research provides a pathway for designing high-performance SPEs for advanced energy storage applications.