Ion exchange membranes (IEMs) blending porous materials have shown great potential for the large-scale energy storage technologies, such as flow battery . However, it remains challenging to overcome the compatibility issue between polymer and porous fillers. In this work, the polymer of intrinsic microporosity (PIM) was successfully introduced into sulfonated polyether ether ketone with high degree of sulfonation (HDS-SPEEK) membrane. PIM exhibited desirable compatibility with HDS-SPEEK due to the natural polymer property . Meanwhile, the rigid skeleton structure of PIM effectively solved the problems of HDS-SPEEK involving poor mechanical property and low vanadium resistance. With increasing the doping of carboxyl grafting modified PIM, the tensile strength increased from 15.22 to 29.94 MPa and the vanadium permeability declined from 4.4 × 10 −6 to 1.6 × 10 −7 cm 2 min −1 . As a result, the vanadium flow battery equipped with the optimized blend membrane showed significantly enhanced coulombic efficiency from 55% to 99% at the current density of 20 mA cm −2 , and had good long-term stability. This work presents a new route to prepare high-performance IEMs based on porous PIM materials for flow battery.
Xiao-Bing Yang,Lei Zhao,Xu-Lei Sui,Ling-Hui Meng,Zhen-Bo Wang
A novel composite vanadium-blocking proton exchange membrane for vanadium redox flow battery (VRB) was designed and constructed by immobilizing phosphotungstic acid (PWA) on Nano Kevlar Fibers (NKFs) via a solution-casting method. The proton/vanadium selectivity of the composite membrane is greatly improved by incorporating the complex formed by NKFs and PWA into the Nafion matrix. Simple tuning of the complex doping quantity results in different composite membranes with superior vanadium barrier properties (namely, a minimum vanadium permeability of 2.46 × 10 -7 cm 2 min −1 ). This coupled with proton conductivities reaching 0.061 S cm −1 at room temperature indicates a proton/vanadium selectivity of 2.48 × 10 5 S min cm −3 , which is 6.3 times higher than that of recast Nafion (0.34 × 10 5 S min cm −3 ). When tested in a VRB, the performance of the single cell assembled with the composite membrane greatly outperforms that with recast Nafion at current densities ranging from 40 to 100 mA cm −2 .
High-molecular-weight bulky-block poly(fluorenyl ether thioether ketone)s were successfully synthesized by a two steps one-pot protocol using N,N′ -dimethy- S -carbamate masked dithiols for vanadium redox flow battery (VRB) application. The followed sulfonation procedure gave birth to novel sulfonated block poly(fluorenyl ether thioether ketone)s (SPFETKs) with controlled ionic exchange capacities (IEC). Membranes with proton conductivities higher than (IEC > 1.66 mequiv. g −1 ) or comparable to (IEC < 1.66 mequiv. g −1 ) that of Nafion117 membrane were achieved. The VO 2+ permeabilities of SPFETKs membranes were much lower than that of Nafion117 membrane. The thermal properties, mechanical properties, oxidative stability , water uptake, proton conductivity, VO 2+ permeability and cell performance were investigated in detail.
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