Phase Morphology Dependence of Ionic Conductivity and Oxidative Stability in Fluorinated Ether Solid-State...

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Solid-state polymer electrolytes are crucial for safe, high-energy lithium metal batteries.
• Current fluorinated ether polymer electrolytes, like perfluoropolyethers (PFPEs), suffer from low ionic conductivity and poor lithium-ion coordination.
• Addressing these limitations is key for advancing battery technology.

Purpose of the Study:

• To enhance the ionic conductivity and electrochemical stability of fluorinated polymer electrolytes.
• To investigate the effects of incorporating cross-linked poly(ethylene glycol) (PEG) into a PFPE matrix.
• To understand the relationship between morphology, ion solvation, and ion transport in polymer blend electrolytes.

Main Methods:

• Synthesis of polymer blend electrolytes combining cross-linked PEG and PFPE.
• Electrochemical characterization, including ionic conductivity measurements at 60 °C.
• Spectroscopic analysis (e.g., NMR, FTIR) and molecular simulations to study ion-polymer interactions and dynamics.
• Electrochemical testing of lithium metal batteries, including cycling performance and high-voltage stability.

Main Results:

• Ionic conductivity of the PEG-PFPE blend increased by six orders of magnitude compared to pure PFPE (from 1.55 × 10^-11 S/cm to 2.26 × 10^-5 S/cm at 60 °C).
• Microscale phase separation was observed in the blend, influencing ion solvation and transport, with ions preferentially residing and moving within the PEG domains.
• The polymer electrolytes demonstrated high-voltage stability (> 6 V vs. Li/Li⁺) and improved Li|Li cycling performance.

Conclusions:

• Incorporating PEG into PFPE significantly boosts ionic conductivity and electrochemical stability in polymer electrolytes.
• The observed phase separation and weak ion-PFPE interactions are critical for enhanced ion transport.
• These novel polymer electrolytes hold significant promise for next-generation high-voltage lithium metal batteries.