Materials Genomics Screens for Adaptive Ion Transport Behavior by Redox-Switchable Microporous Polymer Membranes in Lithium–Sulfur Batteries

Abstract

Selective ion transport across membranes is critical to the performance of many electrochemical energy storage devices. While design strategies enabling ion-selective transport are well-established, enhancements in membrane selectivity are made at the expense of ionic conductivity. To design membranes with both high selectivity and high ionic conductivity, there are cues to follow from biological systems, where regulated transport of ions across membranes is achieved by transmembrane proteins. The transport functions of these proteins are sensitive to their environment: physical or chemical perturbations to that environment are met with an adaptive response. Here we advance an analogous strategy for achieving adaptive ion transport in microporous polymer membranes. Along the polymer backbone are placed redox-active switches that are activated in situ, at a prescribed electrochemical potential, by the device’s active materials when they enter the membrane’s pore. This transformation has little influence on the membrane’s ionic conductivity; however, the active-material blocking ability of the membrane is enhanced. We show that when used in lithium–sulfur batteries, these membranes offer markedly improved capacity, efficiency, and cycle-life by sequestering polysulfides in the cathode. The origins and implications of this behavior are explored in detail and point to new opportunities for responsive membranes in battery technology development.

Design Rules for Membranes from Polymers of Intrinsic Microporosity for Crossover-free Aqueous Electrochemical Devices

“…and (2) persistent kinks along the main chain, in either 2D or 3D, depending on the nature of the site(s) of contortion embodied by the monomer(s). 2,[10][11][12]41,52,[54][55][56][57] By appending ionizable and high-pH-stable amidoximes onto microporous ladder polymer backbones, we arrive at a family of AquaPIMs that serve effectively as ion-selective membranes in aqueous electrochemical devices. In this work, we advance the AquaPIM platform, revealing their foundational stability-conductivityselectivity relationships for membranes that vary in the types and prevalence of both 2D and 3D contortion sites along the polymer backbone as well as the state of ionization of the amidoxime in aqueous electrolytes spanning pH 4.5-15, with the high-pH extreme consisting of 40% aqueous KOH (w/w).…”

Universal chemomechanical design rules for solid-ion conductors to prevent dendrite formation in lithium metal batteries

“…Coated separators were dried overnight at 50 ˚C in vacuo before coin cell assembly. 48 Materials characterization. SEM images were acquired using a Zeiss Gemini Ultra-55 analytical SEM at beam energy of 3 keV.…”

Design Principles of Functional Polymer Separators for High‐Energy, Metal‐Based Batteries

“…Inspired by biological systems, a class of novel redox‐switchable, microporous, polymer membranes (PIMs) were developed that can sequester polysulfides selectively in the cathode with negligible influence on the membrane's ionic conductivity . The phenazine subunits on the polymer backbone were reduced and lithiated by the dissolved lithium polysulfides, which then acted as redox‐active switches to block the transport of polysulfides through the membrane's pore voids.…”