Xu, Jianfeng; Zhao, Hao; Li, Wenhao; Li, Pan; Chen, Chi; Yue, Zhouying; Zou, Liangliang; Yang, Hui

CHEMICAL ENGINEERING JOURNAL

2022, 433, 1385-8947

Xu, Jianfeng; Zhao, Hao; Li, Wenhao; Li, Pan; Chen, Chi; Yue, Zhouying; Zou, Liangliang; Yang, Hui

Herein, to resolve issues regarding the long-term stability of cost-effective non-fluorinated membranes for Vanadium redox flow batteries (VRFBs), we design a facile strategy for fabricating a composite membrane based on long-side-chain Sulfonated poly(terphenylene) (SPTP) blended with Polybenzimidazole (PBI). The introduction of PBI in the ether-free SPTP matrix effectively mitigates the transportation of vanadium ions owing to the Donnan repelling effect and the low swelling ratio of the membranes caused by the acid-base interactions between the imidazolium and sulfonic groups. H-1 NMR and XPS spectra confirm the chemical structure of the prepared membranes. The optimized membrane achieves a lower area resistance, of 0.34 omega cm(2), as well as a low vanadium permeability, of 1.62 x 10-8 cm(2) min(-1), in comparison to that of Nafion117 (0.4 omega cm(2) and 4.2 x 10- 7 cm(2) min(-1)). Consequently, VRFBs that utilize such membranes exhibit superior coulombic and energy efficiencies-of 99.5% and 86.2% at 100 mA cm(-2), respectively-which are an improvement on those of Nafion117 (at 96.1% and 80.9%, respectively). It is important to note that the ether-free backbone, electrostatic repulsion, and reinforcement of PBI greatly improve the mechanical and chemical stability of the blend membranes. Therefore, the C8 membrane presents excellent cycling stability, of up to 1500 charge-discharge cycles, with no significant attenuation in the CE/EE under strong acidic and oxidizing conditions, demonstrating its high physicochemical stability. The results of this study indicate that the SPTP/PBI blend membranes exhibit promising prospects for application in VRFBs.