Single-Ion-Conducting Polymer Electrolytes for Rechargeable Alkaline Ag-Zn Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Quaternized poly(dimethylaminomethylstyrene) (pDMAMS+) based solid-state electrolytes (SSEs) exhibit limited ion transport due to cross-linking at ion-conducting sites.
• Improving ionic conductivity in SSEs is crucial for advancing battery technology.

Purpose of the Study:

• To enhance ionic conductivity in SSEs by synthesizing and evaluating a copolymer system of DMAMS and divinylbenzene (DVB).
• To investigate the structure-transport relationships in p[DVB-DMAMS] copolymers with varying DVB content.
• To demonstrate the feasibility of these SSEs in alkaline batteries, specifically Ag-Zn systems.

Main Methods:

• Synthesis of p[DVB-DMAMS] copolymers via initiated chemical vapor deposition (iCVD).
• Electrochemical impedance spectroscopy (EIS) to measure ionic conductivity.
• Nuclear magnetic resonance (NMR) spectroscopy and small- and wide-angle X-ray scattering (SAXS/WAXS) to analyze polymer structure.
• Electrochemical reduction-oxidation (redox) studies and galvanostatic cycling to evaluate battery performance.

Main Results:

• The best performing copolymer composition with 2.5 wt % DVB achieved a hydroxide ion (OH-) conductivity of 1 mS cm-1 under hydrated conditions, a 100-fold improvement over the homopolymer.
• All copolymer compositions supported Zn-ZnO and Ag-Zn redox chemistry.
• Galvanostatic cycling indicated Ag+ transport, with mitigation strategies explored using 3D sponge electrodes.

Conclusions:

• Copolymerization of DMAMS with DVB effectively enhances ionic conductivity by relocating cross-links away from charge-carrying sites.
• The developed SSEs demonstrate significant potential for application in alkaline Ag-Zn batteries.
• Further optimization, including electrode design, can address challenges like ion migration for practical battery implementation.