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Capacity Decay Mitigation by Asymmetric Positive/Negative Electrolyte Volumes in Vanadium Redox Flow Batteries
Author(s) -
Park Jong Ho,
Park Jung Jin,
Park O Ok,
Yang Jung Hoon
Publication year - 2016
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.201601110
Subject(s) - flow battery , vanadium , electrolyte , redox , battery (electricity) , chemistry , state of charge , capacity loss , energy storage , drop (telecommunication) , volume (thermodynamics) , materials science , electrode , thermodynamics , inorganic chemistry , electrical engineering , power (physics) , physics , engineering
Abstract Capacity decay in vanadium redox flow batteries during charge–discharge cycling has become an important issue because it lowers the practical energy density of the battery. The battery capacity tends to drop rapidly within the first tens of cycles and then drops more gradually over subsequent cycles during long‐term operation. This paper analyzes and discusses the reasons for this early capacity decay. The imbalanced crossover rate of vanadium species was found to remain high until the total difference in vanadium concentration between the positive and negative electrolytes reached almost 1 mol dm −3 . To minimize the initial crossover imbalance, we introduced an asymmetric volume ratio between the positive and negative electrolytes during cell operation. Changing this ratio significantly reduced the capacity fading rate of the battery during the early cycles and improved its capacity retention at steady state. As an example, the practical energy density of the battery increased from 15.5 to 25.2 Wh L −1 simply after reduction of the positive volume by 25 %.