Molecular mobility and Li(+) conduction in polyester copolymer ionomers based on poly(ethylene oxide)

Area of Science:

• Materials Science
• Polymer Chemistry
• Electrochemistry

Background:

• Poly(ethylene oxide) (PEO) based electrolytes are promising for lithium-ion batteries.
• Understanding ion transport dynamics in these materials is crucial for optimizing performance.
• The relationship between polymer segmental motion and ion conductivity needs further elucidation.

Purpose of the Study:

• To investigate the influence of ion content on segmental dynamics and Li(+) transport in PEO-based single-ion conductors.
• To identify the key factors governing ionic conductivity.
• To develop a comprehensive model for ion conduction mechanisms.

Main Methods:

• Dielectric relaxation spectroscopy was employed to study segmental and local dynamics.
• Analysis of electrode polarization effects to differentiate mobile ion concentration and mobility.
• Development and application of a physical model for conduction mechanisms.

Main Results:

• Segmental dynamics slow down and glass transition temperature increases with critical ion content.
• An additional relaxation process attributed to ion pair rotation was observed.
• Ionic conductivity is strongly coupled to segmental relaxation.
• Molar conductivity increases with ion content at a fixed segmental relaxation frequency.

Conclusions:

• Ion transport in these single-ion conductors is intimately linked to polymer segmental dynamics.
• A model involving transient triple ions helps explain conductivity behavior as a function of ion content and dielectric constant.
• Optimizing ion content is key to balancing dynamics and conductivity for advanced battery applications.