Early View 2500719
Research Article

Ion Migration-Induced Capacity Evolution in Iron–Chromium Redox Flow Batteries during Cycling

Ying Liu

Corresponding Author

Ying Liu

State Power Investment Corporation Beijing HE Energy Storage Technology Co., Ltd., Beijing Future Science Park, Beijing, 102209 China

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Jinxiu Cao

Jinxiu Cao

State Power Investment Corporation Co., Ltd., Beijing Future Science Park, Beijing, 102209 China

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Lilong Zhang

Lilong Zhang

State Power Investment Corporation Beijing HE Energy Storage Technology Co., Ltd., Beijing Future Science Park, Beijing, 102209 China

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Rong Zhang

Rong Zhang

State Power Investment Corporation Beijing HE Energy Storage Technology Co., Ltd., Beijing Future Science Park, Beijing, 102209 China

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Jinghao Li

Jinghao Li

State Power Investment Corporation Beijing HE Energy Storage Technology Co., Ltd., Beijing Future Science Park, Beijing, 102209 China

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Jing Li

Jing Li

State Power Investment Corporation Beijing HE Energy Storage Technology Co., Ltd., Beijing Future Science Park, Beijing, 102209 China

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Xiaomeng Li

Xiaomeng Li

State Power Investment Corporation Beijing HE Energy Storage Technology Co., Ltd., Beijing Future Science Park, Beijing, 102209 China

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Jinyi Zhang

Jinyi Zhang

State Power Investment Corporation Beijing HE Energy Storage Technology Co., Ltd., Beijing Future Science Park, Beijing, 102209 China

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Lin Yang

Lin Yang

State Power Investment Corporation Beijing HE Energy Storage Technology Co., Ltd., Beijing Future Science Park, Beijing, 102209 China

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Wei Yu

Wei Yu

State Power Investment Corporation Beijing HE Energy Storage Technology Co., Ltd., Beijing Future Science Park, Beijing, 102209 China

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Feng Shen

Feng Shen

State Power Investment Corporation Beijing HE Energy Storage Technology Co., Ltd., Beijing Future Science Park, Beijing, 102209 China

State Power Investment Corporation Co., Ltd., Beijing Future Science Park, Beijing, 102209 China

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First published: 18 July 2025

Abstract

This article focuses on the iron–chromium redox flow batteries (ICRFBs), systematically investigating the effects of different states of charge (SOCs) on electrolytes, the correlation between detection conditions and capacity, ion migration mechanisms, joint estimation of component migration and capacity loss, as well as the significance of ion migration for system operation. The results reveal that during charging, the volume and ion concentration of positive/negative electrolytes exhibit regular changes, with chromium ion and hydrated hydrogen ion migration being the key factors affecting the charging process. Under detection conditions, SOCs calculated by concentration and voltage show deviations from theoretical values, highlighting the need for precise control of electrolyte charging depth in practical applications. Ion migration is driven by combined effects of potential difference, concentration gradient, and osmotic pressure. In the initial stage, ion diffusion delays capacity decay, while water molecule migration leads to normal capacity decline in the later stage. Utilizing a capacity recovery system combined with ion enrichment can enhance battery capacity beyond the design value. These findings provide critical theoretical support for the practical application and optimized design of ICRFBs.

Conflict of Interest

The authors declare no conflict of interest.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

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