Glass Transition Temperature and Ion Binding Determine Conductivity and Lithium-Ion Transport in Polymer Electrolytes

Nicole S Schauser; Andrei Nikolaev; Peter M Richardson; Shuyi Xie; Keith Johnson; Ethan M Susca; Hengbin Wang; Ram Seshadri; Raphaële J Clément; Javier Read de Alaniz; Rachel A Segalman

doi:10.1021/acsmacrolett.0c00788

Glass Transition Temperature and Ion Binding Determine Conductivity and Lithium-Ion Transport in Polymer Electrolytes

ACS Macro Lett. 2021 Jan 19;10(1):104-109. doi: 10.1021/acsmacrolett.0c00788. Epub 2020 Dec 22.

Authors

Nicole S Schauser^{1

2

3}, Andrei Nikolaev^{3

4}, Peter M Richardson^{2

3}, Shuyi Xie^{2

3}, Keith Johnson^{1

2}, Ethan M Susca², Hengbin Wang³, Ram Seshadri^{1

2

4}, Raphaële J Clément^{1

2

3}, Javier Read de Alaniz⁴, Rachel A Segalman^{1

2

3

5}

Affiliations

¹ Materials Department, University of California, Santa Barbara, California 93106, United States.
² Materials Research Laboratory, University of California, Santa Barbara, California 93106, United States.
³ Mitsubishi Chemical Center for Advanced Materials, University of California, Santa Barbara, California 93106, United States.
⁴ Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, United States.
⁵ Department of Chemical Engineering, University of California, Santa Barbara, California 93106, United States.

PMID: 35548991
DOI: 10.1021/acsmacrolett.0c00788

Abstract

Polymer electrolytes with high Li⁺-ion conductivity provide a route toward improved safety and performance of Li⁺-ion batteries. However, most polymer electrolytes suffer from low ionic conduction and an even lower Li⁺-ion contribution to the conductivity (the transport number, t₊), with the anion typically transporting over 80% of the charge. Here, we show that subtle and potentially undetected associations within a polymer electrolyte can entrain both the anion and the cation. When removed, the conductivity performance of the electrolyte can be improved by almost 2 orders of magnitude. Importantly, while some of this improvement can be attributed to a decreased glass transition temperature, T_g, the removal of the amide functional group reduces interactions between the polymer and the Li⁺ cations, doubling the Li⁺ t₊ to 0.43, as measured using pulsed-field-gradient NMR. This work highlights the importance of strategic synthetic design and emphasizes the dual role of T_g and ion binding for the development of polymer electrolytes with increased total ionic conductivity and the Li⁺ ion contribution to it.