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Electrolyte Imbalance Determination of a Vanadium Redox Flow Battery by Potential‐Step Analysis of the Initial Charging
Author(s) -
Beyer Kirstin,
grosse Austing Jan,
Satola Barbara,
Di Nardo Timo,
Zobel Marco,
Agert Carsten
Publication year - 2020
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201903485
Subject(s) - vanadium , flow battery , electrolyte , redox , open circuit voltage , battery (electricity) , state of charge , chemistry , inorganic chemistry , oxidation state , analytical chemistry (journal) , voltage , materials science , thermodynamics , electrode , chromatography , metal , electrical engineering , organic chemistry , power (physics) , physics , engineering
Vanadium redox flow batteries (VRFB) suffer from capacity fades owing to side reactions and crossover effects through the membrane. These processes lead to a deviation of the optimal initial average oxidation state (AOS=+3.5) of vanadium species in both half‐cell electrolytes. To rebalance the electrolyte solutions, it is first necessary to determine the current AOS. In this study, a new method was developed that enables an accurate determination of the AOS. A potential‐step analysis was performed with mixed electrolyte solutions of both half‐cells during the initial charging. The potential was recorded with a simple open‐circuit voltage (OCV) cell, and the potential‐steps were analyzed. A correlation between the duration of the potential plateaus in the OCV and the amount of vanadium ions of a certain oxidation state in the half‐cell electrolytes was found and used to precisely determine the AOS with a maximum error of 3.6 %.