Correlation between Ionic Conductivity and Mechanical Properties of Solid-like PEO-based Polymer Electrolyte

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Poly(ethylene glycol) methyl ether methacrylate polymer networks (PEO-based networks) are promising electrolytes for Li-metal all solid-state batteries.
• Enhancing the understanding of their physicochemical characteristics is crucial for meeting Li battery electrolyte requirements.

Purpose of the Study:

• Investigate the impact of cross-linking density and ethylene oxide/lithium ratio on mechanical properties and ionic conductivity of PEO-based networks.
• Correlate ionic conductivity with mechanical properties for optimized solid polymer electrolytes (SPEs) and single-ion SPEs (si-SPEs).

Main Methods:

• Synthesized cross-linked PEO-based polymers (si-SPEs and SPEs) using solvent-free radical copolymerization.
• Utilized lithium 3-[(trifluoromethane)sulfonamidosulfonyl]propyl methacrylate (LiMTFSI), poly(ethylene glycol)methyl ether methacrylate (PEGM), and poly(ethylene glycol) dimethacrylate (PEGDM).
• Incorporated LiTFSI as the ionic species in SPEs.

Main Results:

• Most synthesized polymer films were amorphous, self-standing, flexible, homogeneous, and thermally stable.
• A strong correlation was observed between ionic conductivity and mechanical properties in both SPE and si-SPE series.
• Ionic conductivity increased with decreasing glass transition temperature, α relaxation temperature, and storage modulus.

Conclusions:

• Li+ transport is significantly influenced by polymer chain flexibility and Li+/EO interaction.
• Reduced mechanical rigidity and increased chain mobility in PEO-based networks enhance ionic conductivity.
• These findings provide insights for designing advanced solid polymer electrolytes for Li-metal batteries.