Improved proton conductivity and structure stability of an SPEEK/SPPS blend membrane for vanadium redox flow batteries

Sulfonated polyphenylene sulfide (SPPS) containing a rigid main chain is introduced into a SPEEK-based proton exchange membrane to obtain high proton conductivity and dimensional stability. With varied contents of SPPS, the SPEEK/SPPS blend membranes present increased proton conductivity, and at 15 wt% SPPS, the SPEEK/SPPS-15% membrane shows higher proton conductivity (30.9 mS cm(-1)) and ion selectivity (10.5 x 10(3) S min cm(-3)) than Nafion 117 (26.8 mS cm(-1), 4 x 10(3) S min cm(-3)). Moreover, a cell assembled with the SPEEK/SPPS-15% membrane demonstrates better voltage efficiency (VE: 92.5-75.0%) and energy efficiency (EE: 90.0-74.2%) in the current density range of 60-150 mA cm(-2). During a 100-time charge-discharge cycle at 100 mA cm(-2), excellent cycling stability and high charge capacity retention are proved, and the SPEEK/SPPS-15% blend membrane proves its outstanding structural stability and durability after 300 cycles at 150 mA cm(-2). This shows that the structural similarity of the membrane matrix is beneficial to develop a high-performance SPEEK/SPPS blend membrane with desirable structural stability.

Automated summary

Introducing sulfonated polyphenylene sulfide with a rigid main chain into a SPEEK-based proton exchange membrane enhances proton conductivity and dimensional stability. The blend membrane at 15 wt% SPPS content shows superior proton conductivity, ion selectivity, voltage efficiency, energy efficiency, cycling stability, and charge capacity retention compared to Nafion 117, demonstrating exceptional structural stability and durability.