Transference Numbers and Ion Coordination Strength for Mg 2+ , Na + , and K + in Solid Polymer Electrolytes
Year: 2024
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide In solid polymer electrolytes, the transference number ( T i ) is fundamental for performance as it defines the transport efficiency of the electrochemically active species. For systems “beyond Li”, a lack of suitable methods to determine the T i is limiting the understanding of the ion transport in such systems. In this study, a method based on electrophoretic NMR (eNMR) and electrochemical impedance spectroscopy (EIS) is used to determine the T + for Na +, K +, and Mg 2+ in poly(ε-caprolactone) (PCL), comparing this to previous results in poly(ethylene oxide). In common for all cations, a distinct correlation between strong coordination and a low T + is observed. Paradoxically, however, the divalent Mg 2+ in PCL displayed a T + of 0.86 compared to ∼0.5 for the monovalent cations. Persistent clustering in this system suggests that it is better treated as a monovalent [MgTFSI] + + TFSI – system, resulting in a T + of the [MgTFSI] + cation of 0.43. These results serve as a door opener for the wide applicability of the eNMR/EIS method in order to provide an understanding of charge transport in multivalent systems.
Institutions: Uppsala University, University of Münster
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,500
OpenAlex ID: W4402723031