Single-Ion-Conducting\nPolymer Electrolytes for Rechargeable\nAlkaline Ag–Zn Batteries

Recently, we reported on the synthesis and performance\nof a cross-linked\nsingle-anion-conducting solid-state electrolyte (SSE) based on quaternized\npoly(dimethylaminomethylstyrene) (pDMAMS<sup>+</sup>) via initiated\nchemical vapor deposition (iCVD). In the homopolymer pDMAMS<sup>+</sup>-based SSE, the cross-linking occurs at the positively charged ammonium\ncation sites, hindering ion transport and conductivity. To improve\nionic conductivity, we now report on a copolymer system, comprising\nDMAMS and divinylbenzene (DVB). Incorporating DVB moves the cross-links\nto the polymer backbone leaving the quaternary ammonium cation and\nits paired anion with maximal dynamic freedom. We evaluate the structure–transport\nrelationships of a series of p[DVB-DMAMS] copolymers with varying\nDVB content using electrochemical impedance spectroscopy, nuclear\nmagnetic resonance spectroscopy, and small- and wide-angle X-ray scattering.\nOur best composition containing 2.5 wt % DVB provides 1 mS cm<sup>–1</sup> single-ion OH<sup>–</sup> conductivity under\nhydrated conditions, a significant improvement over the 0.01 mS cm<sup>–1</sup> of the hydrated homopolymer pDMAMS<sup>+</sup> SSE.\nAll copolymer compositions support Zn–ZnO and Ag–Zn\nelectrochemical reduction–oxidation (redox) chemistry, which\ndemonstrates the feasibility of a Ag–Zn battery using an alkaline\nsingle-ion-conducting SSE. Galvanostatic cycling shows some transport\nof Ag through the polymer electrolyte, however the deleterious effects\nof Ag migration can be partially mitigated by transitioning from a\ntwo-dimensional (2D) planar electrode to a 3D sponge electrode. With\nthese promising results, the foundation is laid for using single-anion-conducting\nSSEs within alkaline Zn batteries.