Relaxation in polymer electrolytes on the nanosecond timescale

Area of Science:

• Condensed-matter physics
• Materials science
• Polymer science

Background:

• Polymer/lithium-salt complexes are promising battery electrolytes.
• Their biphasic nature (amorphous and crystalline regions) affects ionic conduction.
• Understanding relaxation mechanisms is key to optimizing performance.

Purpose of the Study:

• To investigate the mechanical and electrical relaxation processes in polymer/lithium-salt complexes.
• To elucidate the relationship between ion transport and polymer dynamics.
• To identify relaxation mechanisms relevant to lithium battery electrolytes.

Main Methods:

• Quasielastic neutron scattering (QENS) was employed.
• Nanosecond timescale dynamics were probed.
• Analysis focused on distinguishing translational and rotational relaxation processes.

Main Results:

• At least two distinct relaxation processes were identified: a slow translational and one or two fast rotational processes.
• The slow process resembles relaxation in polymer melts like polyethylene oxide.
• The fast rotational processes appear unique to polymer electrolytes and are linked to lithium ion coordination.

Conclusions:

• Lithium cations act as crosslinkers, significantly modifying polymer network dynamics.
• These crosslinking effects profoundly alter both translational and rotational relaxation.
• The findings provide critical insights into the mechanism of ionic conduction in polymer electrolytes for advanced lithium batteries.