Sulfonated poly(imide-siloxane) membrane as a low vanadium ion permeable separator for a vanadium redox flow battery

Abstract

A sulfonated poly(imide-siloxane) (SPI-PDMS) membrane was prepared and evaluated for its performance in a vanadium redox flow battery (VRFB). Fourier transform infrared spectroscopy analysis verified the successful synthesis of SPI-PDMS, and scanning electron microscopy images and energy-dispersive spectroscopy results illustrated the homogeneity of the membrane. The chemical stability of the SPI-PDMS membrane was superior to that of the pristine sulfonated polyimide membrane. The as-prepared SPI-PDMS membrane showed an order-of-magnitude lower permeability of VO 2+ ion (1.92 × 10 − 7 cm 2 min − 1 ) in contrast to Nafion 117 (17.1 × 10 − 7 cm 2 min − 1 ) and it possessed a much longer self-discharge time (550 h above 1.3 V) than Nafion 117 (65 h above 1.3 V). The SPI-PDMS-containing VRFB exhibited higher coulombic efficiency (98.50%-99.10%) at current densities ranging from 20 to 80 mA cm − 2 than that of Nafion 117 (80.6%-94.8%). At current densities lower than 70 mA cm − 2 , the energy efficiency of the SPI-PDMS-containing VRFB was higher than that of Nafion 117. Cyclic chargedischarge testing demonstrated that the VRFB containing the SPI-PDMS membrane had good operational stability. Overall, this low-cost SPI-PDMS membrane exhibits excellent battery performance and has considerable potential for applications in VRFBs. INTRODUCTIONThe vanadium redox flow battery (VRFB) has been attracting increasing attention as a promising candidate for large-scale energy storage systems because of its advantageous features, including long life, high reliability, non-pollution, low cost and high efficiency. 1-3 The proton-conductive membrane is an important component of VRFBs. The membrane must separate the catholyte and the anolyte, while allowing the passage of protons to form a circuit. The ideal protonconductive membrane should have a low permeability to vanadium ions, high proton conductivity, good chemical stability, strong mechanical integrity and low cost. 4 To date, the perfluorinated sulfonic acid membranes such as Nafion membranes (Dupont Co., Wilmington, DE, USA) have been widely used in VRFB systems, owing to their high proton conductivity and excellent chemical stability. However, Nafion membranes also possess disadvantages such as high vanadium ion permeability and cost, which limit their largescale commercial application in VRFB systems. 5 Consequently, a series of novel proton-conductive membranes with lower vanadium ion permeability and cost have been developed for VRFB applications such as sulfonated poly(phenylsulfone), 6 sulfonated poly(ether ether ketone) 7 and sulfonated polysulfone 8 membranes.Sulfonated polyimide (SPI) is one of the most promising potential candidates for VRFB membranes, because the polyimide can form a compact microstructure to control vanadium ion permeability, and

Synthesis and properties of branched sulfonated polyimides for membranes in vanadium redox flow battery application

“…The mechanical properties of membranes were evaluated by an electronic universal testing machine (QJ-210A, Shanghai Instrument Co., Ltd., China) under a tensile speed of 10 mm min À1 at ambient temperature [34]. The samples were cut into dumbbell shapes with a width of 4 mm in the narrow region.…”

Branched Sulfonated Polyimide/Sulfonated Methylcellulose Composite Membranes with Remarkable Proton Conductivity and Selectivity for Vanadium Redox Flow Batteries

“…This is mainly because that 3.0 mol L −1 H 2 SO 4 solution contains more freely moveable H + compared to DI water. The comparison of the proton conductivities of SPI‐based composite membranes is presented in Table S3 . The proton conductivity of bSPI/s‐MC‐20 % composite membrane is superior to those of most of reported SPI‐based composite membranes for VRFBs, which is very close to that of Nafion 115 membrane.…”

“…The comparison of the proton conductivities of SPI-based composite membranes is presented in Table S3. [19][20][21][22][33][34][35][36][37][38][39] The proton conductivity of bSPI/s-MC-20 % composite membrane is superior to those of most of reported SPI-based composite membranes for VRFBs, which is very close to that of Nafion 115 membrane.…”

Highly Skin-Conformal Laser-Induced Graphene-Based Human Motion Monitoring Sensor

“…The C-H stretching vibration peak of the methyl group associated with PDMS and graphene-based materials is observed at 2929 cm −1 [ 71 ]. However, this signal overlaps with the absorption resulting from the sulfonic acid group, which is in the same region [ 72 ]. It can be seen that LIG is partially formed on the skin color-like substrate.…”