Advanced hybrid membrane for vanadium redox flow battery created by polytetrafluoroethylene layer and functionalized silicon carbide nanowires

Abstract As a key component of vanadium redox flow battery (VRFB), ion exchange membrane determines the performance of VRFB, wherein commercial membrane (such as Nafion) exacerbate problems including high permeability of vanadium ions and poor cyclic stability. In this study, a low vanadium ion permeation hybrid membrane is developed by dispersing functionalized silicon carbide nanowires in perfluorinated sulfonic acid (PFSA) matrix and sandwiching an ultrathin porous polytetrafluoroethylene (PTFE) layer. This hybrid membrane greatly improves the performance of VRFB cell exhibiting good Coulombic efficiency (up to 96.2%) and high energy efficiency (up to 87.1%) at 120 mA cm−2, contrasted with the Nafion 212 membrane (91.3% and 79.8%). Furthermore, a single cell with the hybrid membrane possesses ultra-stable cyclicity (1000 cycles, over 233.4 h). This can be assigned to the unique structure of the membrane in which the functionalized nanowires are uniformly dispersed in PFSA matrix to sandwich an ultra-thin PTFE layer to block or lengthen the diffusion paths of vanadium ions, while the functionalized groups on the surface of the rigid nanowires facilitate protons transportation. This strategy of reshaping membrane may serve in relative fields including proton exchange membrane fuel cells and water treatment.