Pore-Size-Tuned Graphene Oxide Frameworks as Ion-Selective and Protective Layers on Hydrocarbon Membranes for Vanadium Redox-Flow Batteries

• Published in: Nano letters 2018-06, Vol.18 (6), p.3962-3968
• Main Authors: Kim, Soohyun, Choi, Junghoon, Choi, Chanyong, Heo, Jiyun, Kim, Dae Woo, Lee, Jang Yong, Hong, Young Taik, Jung, Hee-Tae, Kim, Hee-Tak
• Format: Article
• Language: English
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/acs.nanolett.8b01429

The laminated structure of graphene oxide (GO) membranes provides exceptional ion-separation properties due to the regular interlayer spacing (d) between laminate layers. However, a larger effective pore size of the laminate immersed in water (∼11.1 Å) than the hydrated diameter of vanadium ions (>6.0 Å) prevents its use in vanadium redox-flow batteries (VRFB). In this work, we report an ion-selective graphene oxide framework (GOF) with a d tuned by cross-linking the GO nanosheets. Its effective pore size (∼5.9 Å) excludes vanadium ions by size but allows proton conduction. The GOF membrane is employed as a protective layer to address the poor chemical stability of sulfonated poly­(arylene ether sulfone) (SPAES) membranes against VO2 + in VRFB. By effectively blocking vanadium ions, the GOF/SPAES membrane exhibits vanadium-ion permeability 4.2 times lower and a durability 5 times longer than that of the pristine SPAES membrane. Moreover, the VRFB with the GOF/SPAES membrane achieves an energy efficiency of 89% at 80 mA cm–2 and a capacity retention of 88% even after 400 cycles, far exceeding results for Nafion 115 and demonstrating its practical applicability for VRFB.