Tackling Capacity Fading in Vanadium Redox Flow Batteries with Amphoteric Polybenzimidazole/Nafion Bilayer Membranes

Abstract

Vanadium flow batteries are among the most promising technologies for stationary energy storage applications if their cost of storage can be further decreased. Capacity fading resulting from imbalanced vanadium crossover is a key operating cost component. Herein, a new approach is reported to avoid this cost by balancing electrolyte transport with amphoteric bilayer Nafion/meta‐polybenzimidazole membranes. Within this system, the anion‐ and cation‐exchange capacity can be tuned in a straightforward manner by changing the thickness of the respective polymer layer to balance electrolyte transport for a given current density. At high current densities, a net migrative flux of vanadium directed towards the positive side is observed owing to the higher average charge of vanadium ions present at the negative side. The coulombic repulsion between the vanadium ions and the positive charges in the membrane counteracts this migrative transport and can reverse the direction of the net vanadium flux. For a technically relevant current density of 120 mA cm−2, a PBI thickness of 3–4 μm is required to balance the vanadium crossover and to minimize capacity fading.

Investigation of Nafion series membranes on the performance of iron‐chromium redox flow battery

“…5,6 The catholyte and anolyte of RFB are composed of dissolved electro-active species, which are circulated during the operation between the external storage tank and the electrochemical cell. [16][17][18][19] Nevertheless, complex production and high cost limit its practical application. 9 In the core of the RFB electrochemical cell is typically a proton-conducting membrane (PEM) or separator between two carbon electrodes, which not only physically separates the cathode and anode electrolytes, but also enables the proton transport in order to complete the circuit accompanied with the electron transfer during the passage of current.…”

“…[10][11][12][13] The ion conduction provided by the PEM is a critical element of RFB, as it mainly determines the capacity decay, efficiency, lifetime, and the expense of the whole RFB system. 18 For RFBs, the ideal membrane ought to own several merits, including low cost, outstanding chemical and mechanical stability, high ionic conductivity, and low active species crossover.…”

“…14,15 Nowadays, Nafion as an outstanding representative of perfluorinated sulfonic acid membranes is widely adopted in RFB application as a consequence of its superior chemical stability and extremely high ionic conduction. [16][17][18][19] Nevertheless, complex production and high cost limit its practical application. 20,21 The first developed iron-chromium redox flow battery (ICRFB) was on the basis of Fe 2+ /Fe 3+ halide electrolyte for the cathode and Cr 2+ /Cr 3+ halide electrolyte for the anode.…”

Ordered Honeycomb‐Pattern Membrane†

“…Amphoteric ion modification of membrane gives the main material a positive and negative charge, which decomposes upon contacting with proteins and other organic pollutants. [ 81,82 ] For example, Yue et al . [ 83 ] and Yu et al .…”

Facile Preparation of EVOH-Based Amphoteric Ion Exchange Membrane Using Radiation Grafting Technique: A Preliminary Investigation on Its Application for Vanadium Redox Flow Battery

“…Hence, there have been extensive research activities towards the modification of Nafion-based membrane to reduce its vanadium ion permeability. For instance, SiO 2 [7], polypyrrole [8], fluorocarbon surfactant [9], sulfonated graphene oxide [10], polybenzimidazole [11], phosphotungstic acid immobilized nanofibers [12] and sulfonated copper phthalocyanine [13] were used to modify Nafion membranes and the modified Nafion membranes show lower vanadium ion permeability than pristine Nafion membranes. However, the high price of Nafion membranes (500–700 dollar m −2 ) hinders their applications [14].…”