SPPO pore-filled composite membranes with electrically aligned ion channels via a lab-scale continuous caster for fuel cells: An optimal DC electric field strength-IEC relationship

In this paper, novel composite membranes with electrically aligned ion channels in the thickness direction are presented for fuel cell applications; a fabrication method in the scale-up system and continuous mode is also suggested. The sulfonated poly(2,6-dimethyl-1,4-phenlyene oxide) (SPPO) polymer filled porous polyethylene (ρPE) films were prepared using a lab-scale continuous caster and simultaneously a direct-current (DC) electric field was applied for the alignment of ion channels in SPPO. Importantly, the proton conductivity of aligned-composite membranes with various ion exchange capacities was enhanced by three to five times than the non-aligned SPPO composite membranes. Finally, the optimized aligned composite membranes with the highest transport number were only applied for the fuel cell test. The optimized aligned composite membrane revealed the highest maximum power density than other fabricated composite membranes and Nafion® 115. Especially, the normalized maximum power density for unit conductivity value was introduced to confirm the effects of alignment of ion channels in a practical electrochemical system. The normalized maximum power density for unit conductivity value for the optimized aligned composite membrane was also stood 43% higher than that of Nafion® 212. According to all properties in this study, understanding the technique of alignment the ion channel in composite membranes offers a great possibility for improving the performance of the ion exchange membrane.