Durable and Efficient PTFE Sandwiched SPEEK Membrane for Vanadium Flow Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Sulfonated poly(ether ether ketone) (SPEEK) membranes suffer from poor cycling stability in vanadium flow batteries (VFBs).
• This instability limits the practical application and lifespan of VFB energy storage systems.

Purpose of the Study:

• To enhance the cycling stability and longevity of SPEEK membranes in VFBs.
• To develop a facile and effective protective layer for SPEEK membranes.

Main Methods:

• A sandwich membrane design was created using hydrophilic porous poly(tetrafluoroethylene) (PTFE) films.
• PTFE films served as stress-protective and electrolyte buffer layers for the SPEEK membrane.
• The performance of the PTFE/SPEEK/PTFE membrane was evaluated in a VFB with a 2.0 M vanadium electrolyte.

Main Results:

• The novel sandwich membrane demonstrated super long-life properties in VFBs.
• The VFB operated steadily for over 1000 cycles with high Coulombic efficiency (98.5%) and energy efficiency (85.0% @ 80 mA cm(-2)).

Conclusions:

• The sandwich PTFE/SPEEK/PTFE membrane design significantly improves VFB cycling stability and lifespan.
• This simple and effective strategy offers a promising approach for other non-fluoride membranes in energy storage applications.