A Zinc–Bromine Flow Battery with Improved Design of Cell Structure and Electrodes

Abstract

The zinc–bromine flow battery (ZBFB) is regarded as one of the most promising candidates for large‐scale energy storage owing to its high energy density and low cost. However, because of the large internal resistance and poor electrocatalytic activity of graphite‐ or carbon‐felt electrodes, conventional ZBFBs usually can only be operated at a relatively low current density, which limits their widespread application. Herein, we propose an asymmetrical cell by replacing the conventional thick felt electrode with a thin and electrocatalytically active carbon‐paper (CP) electrode interfacing with a flow‐field structure. With the enhanced electrocatalytic activity of CP for the Br2/Br− redox reaction and the reduced internal resistance of the thinner electrode, the ZBFB with this newly proposed structure exhibits an energy efficiency of up to 83.5 % at a current density of 40 mA cm−2, much higher than that with a graphite‐felt electrode of only 73.0 %. Remarkably, the battery can even be operated at a high current density up to 100 mA cm−2 while maintaining an energy efficiency of more than 70 %, demonstrating an excellent rate capability.

Micro‐Tubular Flow Cell Design Utilizing Commercial Hollow Fiber Dialysis Membranes for Size‐Exclusion Based Flow Batteries

“…Therefore, it is more reasonable to compare this μTFC to other zinc‐based flow cells rather than zero‐gap vanadium redox flow batteries. Compared to zinc‐bromine cFFCs, the lowest resistance reported to the best of our knowledge, so far, is approximately 0.6 Ω,, which corresponds to a volumetric resistance of more than 0.8 Ω cm 3 . This resistance is more than two times higher than the one achieved with the μTFC presented in the study at hand.…”

“…In conclusion, this first μTFC prototype obtained an ohmic resistance that was ten‐fold lower than the resistance of the reference cFFC, two‐fold lower than the lowest resistance value reported for tubular flow cells so far, and more than two times lower than the lowest resistance reported for zinc‐bromine cFFCs ,. The reduced ohmic losses of this μTFC prototype can be attributed mainly to the increased membrane area to volume ratio, shorter charge carrier pathways, and the lower area resistance of the micro‐tubular dialysis membrane.…”

An updated review of energy storage systems: Classification and applications in distributed generation power systems incorporating renewable energy resources

“…Zinc‐bromine (ZnBr) batteries are hybrid flow class of batteries wherein two aqueous solutions, based on zinc and bromine placed in two different tanks, are used which, during charging and discharging phases, flow through the electrolytic cells where the reversible electrochemical reactions take place . When the electrochemical reaction takes place, zinc and bromine ions move towards opposite electrolyte direction through the porous separator . During charging, deposition of zinc takes place on the negative electrode and that of bromine on the positive electrode, while in discharging mode, reverse electrochemical reactions takes place and zinc deposited on the negative electrode gets dissolved into the electrolyte so as to be available for the next charging cycle .…”

“…121,131 When the electrochemical reaction takes place, zinc and bromine ions move towards opposite electrolyte direction through the porous separator. 92,132 During charging, deposition of zinc takes place on the negative electrode and that of bromine on the positive electrode, while in discharging mode, reverse electrochemical reactions takes place and zinc deposited on the negative electrode gets dissolved into the electrolyte so as to be available for the next charging cycle 133 .…”

Aligned Electrospun Carbon Nanofibers as Electrodes for Vanadium Redox Flow Batteries

“…In recent decades, energy storage technologies have got rapid development and widespread deployment for load leveling while coupled with the intermittent renewable energies, such as solar and wind power . Among the available energy storage systems, redox flow batteries (RFBs) have been the focus of interest, of which the energy and power supply can be designed independently through adjusting the volume of the electrolyte and the scale of cell stack . In particular, the all‐vanadium redox flow battery (VRFB), which adopts the same element in both positive and negative electrolytes, has been widely adopted in large‐scale energy storage systems due to its advantages of long cycle life, high stability, fast response, and no cross contamination of the active species …”