Sulfonated poly(ether ether ketone)/mesoporous silica hybrid membrane for high performance vanadium redox flow battery

Hybrid membranes of sulfonated poly(ether ether ketone) (SPEEK) and mesoporous silica SBA-15 are prepared with various mass ratios for vanadium redox flow battery (VRB) application and investigated in detail. The hybrid membranes are dense and homogeneous with no visible hole as the SEM and EDX images shown. With the increasing of SBA-15 mass ratio, the physicochemical property, VO2+ permeability, mechanical property and thermal stability of hybrid membranes exhibit good trends, which can be attributed to the interaction between SPEEK and SBA-15. The hybrid membrane with 20 wt.% SBA-15 (termed as S/SBA-15 20) shows the VRB single cell performance of CE 96.3% and EE 88.1% at 60 mA cm−2 due to its good balance of proton conductivity and VO2+ permeability, while Nafion 117 membrane shows the cell performance of CE 92.2% and EE 81.0%. Besides, the S/SBA-15 20 membrane shows stable cell performance of highly stable efficiency and slower discharge capacity decline during 120 cycles at 60 mA cm−2. Therefore, the SPEEK/SBA-15 hybrid membranes with optimized mass ratio and excellent VRB performance can be achieved, exhibiting good potential usage in VRB systems. The left side of graphical abstract image is the combination of SPEEK/SBA-15 hybrid membrane photograph and stable efficiency in cycle life test. The right side of graphical abstract image is the schematic of the interaction between SPEEK and SBA-15. [Display omitted] •SPEEK/SBA-15 (S/SBA-15) hybrid membranes are used in vanadium redox flow battery.•S/SBA-15 hybrid membranes are dense and homogeneous with no visible hole.•Membranes show good property trends for the interaction between SPEEK and SBA-15.•S/SBA-15 20 membrane shows highest efficiency and highly stable cycle performance.