title: Morphology and electrochemical properties of perfluorosulfonic acid ionomers for vanadium flow battery applications: effect of side-chain length.
abstract: Perfluorosulfonic acid ionomers (PFSI) with different side-chain lengths have been investigated with respect to their morphology and electrochemical properties in vanadium flow batteries (VFB). The results indicated that the membrane with the shortest side chains (SSC-M2) displayed small ion clusters and a low degree of hydrophobic-hydrophilic separation, which is favourable to reduce the cross-over of vanadium ions in the VFB. SSC-M2 shows a similar proton conductivity to Nafion, which carries longer ionic side chains but with much lower ion permeability. As a result, the VFB assembled with SSC-M2 exhibited a superior coulombic efficiency and a voltage efficiency close to that of Nafion115. In situ mass transfer revealed that SSC-M2 had a remarkably low degree of vanadium and water transfer across the membrane, which resulted in lower capacity fading than in the case of Nafion115. These results indicate that a membrane with short side chains is an ideal option in the fabrication of high-performance VFBs with low capacity loss.
authors.affiliation: Division of Energy Storage, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, PR China.
authors.forename: Cong
authors.initials: C
authors.lastname: Ding
authors.forename: Huamin
authors.initials: H
authors.lastname: Zhang
authors.forename: Xianfeng
authors.initials: X
authors.lastname: Li
authors.forename: Hongzhang
authors.initials: H
authors.lastname: Zhang
authors.forename: Chuan
authors.initials: C
authors.lastname: Yao
authors.forename: Dingqin
authors.initials: D
authors.lastname: Shi
mesh_terms: D004553:Electric Conductivity; D011211:Electric Power Supplies; D004563:Electrochemistry; D005465:Fluorocarbon Polymers / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008567:Membranes, Artificial; D013696:Temperature; D014639:Vanadium / Q000737:chemistry*
chemical_list: D005465:Fluorocarbon Polymers; D008567:Membranes, Artificial; D014639:Vanadium; C040402:perfluorosulfonic acid
keywords: electrochemistry; ion channels; membranes; polymers; vanadium