TY - JOUR
T1 - Crossover analysis in a commercial 6 kW/43kAh vanadium redox flow battery utilizing anion exchange membrane
AU - Oreiro, Sara Noriega
AU - Bentien, Anders
AU - Sloth, Jonas
AU - Rahimi, Mohammad
AU - Madsen, Morten Brun
AU - Drechsler, Terje
N1 - Publisher Copyright:
© 2024 The Author(s)
PY - 2024/6
Y1 - 2024/6
N2 - The volumetric and species transport is a significant source of capacity decay in vanadium redox flow batteries (VRFBs). However, even with the prevalent use of anion exchange membranes (AEMs) in commercial systems, the understanding of the crossover mechanisms in this context remains limited. The primary objective of this study was to gain a deeper comprehension of these mechanisms through experimental investigations conducted on a 6 kW/43kAh VRFB system using AEMs. It is concluded that protons serve as the primary charge carriers, owing to the high ionic concentrations of the electrolyte. During normal operation, there was a consistent pattern of volume transfer from the positive to the negative half-cell (∼0.5 % of the total electrolyte per cycle/day). Experimental assessments performed at different states-of-charge (SoCs) revealed that the volumetric transport towards the anolyte increases with SoC. The osmotic effects are concluded to be the main contributors to the volumetric transport. The osmotic pressure difference is hypothesized to arise from the asymmetric diffusion coefficients of the vanadium ions, changes in pH affecting sulfate and bisulfate equilibrium alongside their different diffusion coefficients, and a likely predominance of the bisulfate concentration gradient in the water transport through the membrane.
AB - The volumetric and species transport is a significant source of capacity decay in vanadium redox flow batteries (VRFBs). However, even with the prevalent use of anion exchange membranes (AEMs) in commercial systems, the understanding of the crossover mechanisms in this context remains limited. The primary objective of this study was to gain a deeper comprehension of these mechanisms through experimental investigations conducted on a 6 kW/43kAh VRFB system using AEMs. It is concluded that protons serve as the primary charge carriers, owing to the high ionic concentrations of the electrolyte. During normal operation, there was a consistent pattern of volume transfer from the positive to the negative half-cell (∼0.5 % of the total electrolyte per cycle/day). Experimental assessments performed at different states-of-charge (SoCs) revealed that the volumetric transport towards the anolyte increases with SoC. The osmotic effects are concluded to be the main contributors to the volumetric transport. The osmotic pressure difference is hypothesized to arise from the asymmetric diffusion coefficients of the vanadium ions, changes in pH affecting sulfate and bisulfate equilibrium alongside their different diffusion coefficients, and a likely predominance of the bisulfate concentration gradient in the water transport through the membrane.
KW - Anion exchange membrane
KW - Crossover
KW - Diffusion
KW - Migration
KW - Osmosis
KW - Vanadium redox flow battery
UR - http://www.scopus.com/inward/record.url?scp=85192237381&partnerID=8YFLogxK
U2 - 10.1016/j.cej.2024.151947
DO - 10.1016/j.cej.2024.151947
M3 - Journal article
AN - SCOPUS:85192237381
SN - 1385-8947
VL - 490
JO - Chemical Engineering Journal
JF - Chemical Engineering Journal
M1 - 151947
ER -