Submicron-Thick Single-Ion-Conducting Polymer Electrolytes via Initiated Chemical Vapor Deposition

Three-dimensional (3D) electrodes and architectures are becoming more prevalent in next generation batteries leading to enhanced performance. For instance, in the case of Zn-based batteries, a 3D Zn electrode alleviates current hotspots mitigating shape change¹, while in the case of Li–S batteries a 3D porous carbon nanofoam helps to prevent dissolution and diffusion of active material.² Additional functionality and flexibility can be unlocked via modification of the extensive surface area of the 3D components, such as incorporating coatings to enhance electrolyte wettability, serve as an artificial solid-electrolyte interphase, or as a solid-state electrolyte. Conformally and homogeneously coating the interior and exterior surfaces of a complex, macroscopically thick 3D structure necessitates the use of non-line-of-sight deposition techniques.<br/>Initiated chemical vapor deposition (<i>i</i>CVD) is a non-line-of-sight method that has demonstrated utility to generate conformal polymer coatings with tunable thickness on both 2D and 3D substrates. Recently, we have reported on the post-deposition modification of <i>i</i>CVD-derived polymer films to produce a submicron-thick anion-conducting polymer electrolyte.^3,4 To build off of these results, we move to generate cross-linked co-polymer systems via <i>i</i>CVD, based off of divinylbenzene and 4-dimethylaminomethylstyrene (DVB-co-DMAMS), and use post-processing protocols to impart specific performance functionalities. The co-polymer can be rendered as a single-anion conducting solid-state electrolyte (SSE) and we show that the ionic conductivity of the SSE depends upon the DVB/DMAMS ratio, the mobile ion identity, and network plasticization, with anion conductivity nearing 1 x 10^-4 S cm^–1 under optimal conditions. Molecular dynamic simulations are further used to probe ion transport, which coupled with mechanical property analysis enables structure-chemistry-property relationships to be determined. The <i>i</i>CVD generated SSEs facilitate anionic redox chemistry (Zn/ZnO, Ag/ZnO) without the use of an additional separator or free salt, a major advancement for improving specific cell capacity. Coupling iCVD with mass-scalable post-processing protocols to impart specific performance functionality of submicron-thick SSEs opens the door to advanced 3D electrodes and components to enable next-generation energy storage systems with high performance metrics.<br/>(1) Parker, J. F.; Chervin, C. N.; Nelson, E. S.; Rolison, D. R.; Long, J. W. Wiring zinc in three dimensions re-writes battery performance—dendrite-free cycling. Energy Environ. Sci. 2014, 7 (3), 1117-1124.<br/>(2) Neale, Z. G.; Lefler, M. J.; Long, J. W.; Rolison, D. R.; Sassin, M. B.; Carter, R. Freestanding carbon nanofoam papers with tunable porosity as lithium-sulfur battery cathodes. Nanoscale 2023.<br/>(3) Ford, H. O.; Chaloux, B. L.; Swift, M. W.; Klug, C. A.; Miller, J. B.; Kim, Y.; Jugdersuren, B.; Zuo, X.; Long, J. W.; Liu, X.; et al. Non–Line-of-Sight Synthesis and Characterization of a Submicron Isomerically Pure Cationic Polymer. RSC Appl. Interfaces 2023, in review.<br/>(4) Ford, H. O.; Chaloux, B. L.; Kim, Y.; Long, J. W.; Rolison, D. R.; Sassin, M. B. Submicron-Thick Single-Anion Conducting Polymer Electrolytes RSC Appl. Interfaces 2023, in review.