(63l) From Structure to Redox: Solid-State Anion-Conducting Polymer Electrolytes for 3D Ag-Zn Batteries Via Initiated Chemical Vapor Deposition

In order to combine the opposing metrics of high power density and energy density, battery cell design must transition away from the conventional two-dimensional (2D) layer design towards three-dimensional (3D) all solid-state configurations. Interpenetrating 3D electrodes enable the cell geometry to be expanded in all dimensions, improving energy density, while maintaining 1D ion-transport pathways throughout, thereby preserving power density.¹ The ideal battery chemistry is one that is amenable to the 3D configuration, aqueous (enhancing safety), solid-state (increasing energy density), and composed of sustainable, ethical, and non-strategic elements. Alkaline Zn redox couples, in particular Ag-Zn, can meet these criteria. With the development of an NRL patented 3D Zn electrode that alleviates shape change driven dendritic growth, the remaining challenge is the engineering of a thin solid-state electrolyte (SSE) that can conform to the 3D electrode architecture.²

Initiated chemical vapor deposition (iCVD) is an emerging non-line-of-sight method capable of growing thin polymer films on complicated and varied substrates. Here, we demonstrate the use of iCVD to generate a library of homo- and co-polymers based on the chemistry of dimethylaminomethylstyrene (DMAMS) and divinylbenzene (DVB), which are converted to single anion-conducting SSEs post polymerization. We establish fundamental relationships regarding the influence of polymer composition, structure, and transport properties on electrolyte performance with the use of characterization including electrochemical impedance spectroscopy, small- and wide-angle x-ray scattering, ATR-IR spectroscopy, X-ray photoelectron spectroscopy, and solid-state NMR spectroscopy. Optimized polymer compositions have an ionic conductivity of up to 10^-2 S cm^-1 when fully hydrated and 10^-5 S cm^-1 under low humidity conditions (33% RH). Furthermore, the best performing SSEs facilitate Ag-Zn redox as investigated in 2D and 3D cell configurations. The redox reactions are studied mechanistically from a perspective of transport phenomena and interfaces, while full cell performance is measured with extended cycling.

1] Long, J.W.; Dunn, B.; Rolison, D.R.; White, H.S. Chem. Rev. 2004, 104 (10), 4463–4492.

2] Parker, J.F.; Chervin, C.N.; Nelson, E.S.; Rolison, D.R.; Long, J.W. Energy Environ Sci. 2014, 7, 1117–1124.