A Composite Membrane Based on Sulfonated Polystyrene Implanted in a Stretched PTFE Film for Vanadium Flow Batteries

Abstract

The quality of ion-selective membranes determines the efficiency of Vanadium Flow Batteries (VFBs), and alternatives to expensive Nafion™ materials are actively being searched for. One of the membrane architecture approaches is to imitate the Nafion™ structure with two separate phases: a conductive sulfonated polymer and an inner matrix. We introduce a new composite material based on sulfonated styrene polymerized inside the pores of a stretched PTFE matrix. Variation of polystyrene content and a sulfonation degree allowed to obtain membranes with IEC from to 0.96 to 1.84 mmol/g. Balanced vanadium permeability (ca. 5.5 • 10 À 6 cm 2 /min) and proton conductivity (ca. 50 mS/cm) were achieved for the material with 21-23 % polystyrene content and a sulfonation degree up to 94 %. Membranes showed stable cycling with 81 % energy efficiency in a single-cell VFB. This work contributes to the existing knowledge of Nafion alternatives by providing a cheap and scalable method of membrane production.

Advancements of Polyvinylpyrrolidone‐Based Polymer Electrolyte Membranes for Electrochemical Energy Conversion and Storage Devices

“…ChemSusChem through the membrane. [69] Therefore, an ion exchange membrane with good conductivity and preferable selective permeability must be selected. [70] Taking the Nafion membrane as an example of the cation exchange membrane, [71] although it has high proton conductivity, there are a lot of negative charges in the membrane, which adversely affects the barrier of vanadium ions (Figure 11a).…”

Synthesis and Characterization of Lithium-Conducting Composite Polymer–Ceramic Membranes for Use in Nonaqueous Redox Flow Batteries

“…Ideally, a RFB membrane should simultaneously block the undesired transport of redox-active species and solvent between the positive and negative electrolytes, promote the rapid and selective transport of supporting ions, possess high mechanical and chemical stability, and be conducive to low-cost and scalable production . Implementing these properties in practice is more challenging, and while there have been considerable efforts dedicated to advancing redox chemistries for NAqRFBs, fewer attempts have focused on developing membranes to support leading chemistries, frustrating full cell performance and durability. − Most prior research on NAqRFBs incorporates commercially available ion-exchange membranes, , which are not specifically engineered for nonaqueous electrochemical environments and thus typically display unfavorable combinations of ionic conductivity and species selectivity. − Therefore, new separation approaches must be considered, with particular emphasis on materials developed for energy storage technologies that operate in similar (electro)­chemical environments.…”