Review and Perspectives of Sulfonated Poly(ether ether ketone) Proton Exchange Membrane for Vanadium Flow Batteries

Abstract

The vanadium flow battery (VFB) has been implemented as an alternative energy storage technology for wind and solar energy systems due to its advantages of high energy conversion efficiency, facile design and fabrication, extended battery lifespan, high power, and low cost. The proton exchange membrane (PEM), as one of the key VFB components, is critical in determining the application value and practical efficiency of battery systems. Among various PEMs, sulfonated poly(ether ether ketone) (SPEEK) membranes have received widespread attention due to their simple structure, facile preparation, superior thermal and mechanical stability, low cost, and easy modification. However, their large-scale application is still plagued, where membrane performance heavily depends upon the sulfonation degree and the higher sulfonation leads to worse ion permeation and an excessive swelling behavior, decreasing the membrane stability and battery performance. Therefore, structural regulation, functionalization modification, and filler enhancement strategies of SPEEK have been applied to improve its comprehensive performance. Here, the fundamental research and practical development status of SPEEK in the VFB are comprehensively reviewed, including recent advances in various modification strategies. Potential interactions among the structure−activity relationship, modification methods, and chemical stability protection of the SPEEK membrane are established. Finally, the challenges and potential future research directions for the development of SPEEK membranes are critically appraised.

2023 Pioneers in Energy Research: Shizhang Qiao

“…Vanadium flow batteries (VFBs) have been implemented as an alternative energy storage technology for wind and solar energy systems. Qian et al present an extensive review of sulfonated poly­(ether ether ketone) (SPEEK) membranes. The fundamental research and practical development status of SPEEK in the VFB are comprehensively reviewed, including recent advances in various modification strategies.…”

Enhancing Proton Conductivity and Dimensional Stability of Nanofiber Proton Exchange Membranes through In Situ Growth of MOF-Modified PVDF Nanofibers

“…Fuel cells, a promising green energy source, are not constrained by the limitations of the Carnot cycle and hold significant potential for further development. , The proton exchange membrane (PEM) is crucial in fuel cells, as it dramatically impacts the internal resistance and conversion efficiency of energy. Nanofiber proton exchange membrane (NFPEM), a novel composite membrane, leverages the large surface area of nanofibers to create proton transport channels at the interface with the polymer matrix, establishing a three-dimensional network that boosts proton conduction. , However, most polymer fibers naturally lack proton conduction and require special treatment to gain this feature.…”

A Critical Review of the Advancement Approach and Strategy in SPEEK-Based Polymer Electrolyte Membrane for Hydrogen Fuel Cell Application

“…On the other hand, sulfonated poly­(ether ether ketone) (SPEEK), a hydrocarbon-based polymer, has higher thermo-mechanical and chemical stability and a lower cost than the available Nafion membrane. − However, its proton conductivity is lower than the Nafion membrane . Besides that, SPEEK tends to deteriorate in mechanical strength at temperatures above 100 °C and low humidity levels, which lowers the resulting membrane’s performance and long-term stability.…”