Colloquium

Monday 24 October 2022

Speaker

Xi (Chelsea) Chen

Affiliation

Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA

Title

Ion Transport and Segmental Dynamics of Polymer Electrolytes at Interfaces

Location

online.

Time

17:00

Language

English

Abstract

Polymer electrolytes are one of the major classes of solid electrolytes to enable high energy Li metal batteries. A polymer electrolyte encounters many interfaces in a solid-state battery. In order to overcome the low room temperature ionic conductivity of common polymer electrolytes, they may be combined with highly ionically conductive ceramic electrolytes to form composite solid electrolytes for improved ionic conductivity and multifunctionality. A polymer electrolyte may also be used in the solid-state cathode to facilitate Li ion transport in and out of the cathode active material. This presentation focuses on elucidating ion transport and segmental dynamics of polymer electrolytes interfacing ceramic particles in both the polymer-ceramic composite solid electrolytes and polymer electrolyte based solid cathodes.

We show that by incorporating highly conductive model ceramic particles into a model polymer electrolyte matrix, the ionic conductivity of composite electrolytes is not improved in most compositions. A large interfacial resistance for ion transport across the polymer-ceramic electrolyte interface is quantified by comparing the resistance of a polymer-ceramic-polymer trilayer cell with that of single layers using impedance spectroscopy. The origin of the ion transport barrier is elucidated by investigating the segmental dynamics and ion mobilities of polymer chains and the solvated ions in a model composite electrolyte using a combined quasi-elastic neutron scattering/solid-state nuclear magnetic resonance methodology. In a second case, the polymer chain structure and segmental mobility of a polymer electrolyte based solid cathode is studied by small angle neutron scattering and quasi-elastic neutron scattering. Strategies to achieve optimum interfacial structures in polymer based solid state batteries will be discussed.