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

Abstract

A series of branched sulfonated polyimide (bSPI)/sulfonated methylcellulose (s‐MC) composite membranes composed of a designed and synthesized bSPI polymer and functionalized s‐MC are prepared by using a facile solution casting method for vanadium redox flow batteries (VRFBs). Among all bSPI/s‐MC composite membranes, the optimized bSPI/s‐MC‐20 % composite membrane has the best proton selectivity of 2.45×105 S min cm−3, which is 14.4 times as high as the Nafion 115 membrane. The bSPI/s‐MC‐20 % composite membrane possesses superior proton conductivity compared to most reported SPI‐based composite membranes for VRFBs. The VRFB with a bSPI/s‐MC‐20 % composite membrane shows excellent battery efficiencies (CE=99.2–98.0 %, EE=66.3–77.6 %) and capacity retention (73.3–47.2 %). Moreover, the cost of the bSPI/s‐MC‐20 % composite membrane is only a quarter of that of a commercial Nafion 115 membrane. This work develops a new strategy to fabricate cheap bSPI‐based composite membranes by introducing a suitable functionalized biomass material.

Review—Recent Membranes for Vanadium Redox Flow Batteries

“…This is solved by using the branched structuring of SPI to prepare composite SPI membranes. Long et al 102 developed composite membranes of branched sulfonated polyimide (bSPI)/sulfonated methylcellulose (s-MC). For the part, Yang et al 103 developed fluorine-containing branched sulfonated polyimide membranes with ionic cross-linking (c-FbSPI) at different sulfonation degrees (40%-70%).…”

Oriented Proton-Conductive Nanochannels Boosting a Highly Conductive Proton-Exchange Membrane for a Vanadium Redox Flow Battery

“…(a) Discharge capacity retentions of VRFBs assembled with SPEEK, SPEEK/Him-pS-3, and Nafion 212 membranes at 250 mA cm –2 ; (b) cyclic efficiencies of VRFB assembled with the SPEEK/Him-pS-3 composite membrane varied with cycle numbers at 250 mA cm –2 and monitor images (inset in (b)) recorded at various cycles; and (c) energy efficiencies of various membranes for VRFB single cells reported in recent years. ,,,,,,− …”

Construction and Investigation of Novel Cross-Linked Fluorine-Containing Sulfonated Polyimide Membranes for VFB Application

“…10,11 Inevitably, the proton conductance and chemical stability of SPI membranes are unsatisfactory without reinforcement and structural regulation. 12,13 As is known to all, cross-linking is an efficacious method to improve the performance of membranes. However, the design of molecular chains containing cross-linking sites and the selection of cross-linking agents are critical issues for the improvement of membrane performance.…”