苏氨酸提升铁铬液流电池循环稳定性与抑制析氢的研究OA

Iron-chromium flow batteries,as a low-cost,long-duration,large-scale energy storage technology,suffer from capacity decay primarily owing to the poor reversibility of the chromium electrode in the electrolyte.This study proposes the introduction of threonine(Thr)into the electrolyte to regulate the solvation structure of chromium species through its chelating interaction with chromium ions,thereby enhancing the overall electrochemical performance of the battery.Density functional theory calculations reveal that Thr preferentially coordinates with chromium ions,altering its native solvation shell and leading to the formation of a stable chromium-Thr complex.This structural modification is crucial for enhancing the kinetics and reversibility of the chromium redox reaction.Concurrently,Thr molecules exhibit a competitive adsorption effect toward hydrogen ions on the electrode surface.This behavior effectively suppresses the hydrogen evolution reaction(HER),a predominant side reaction at the negative electrode during charging and a major contributor to Coulombic efficiency loss and capacity fade.The suppression of the HER directly contributes to improved capacity retention over extended cycling.The formation and stability of the chromium-Thr complex were further validated experimentally.Ultraviolet-visible spectroscopy and long-term cycling tests further confirm that the generated complex maintains structural stability during cycling,playing a crucial role in sustaining electrochemical stability.Under identical conditions,the battery employing the pristine electrolyte(without the Thr additive)suffered rapid performance degradation.Its discharge capacity dropped to merely 39%of its initial value after only 100 cycles,and its average capacity decreased to 6.4 mAh per cycle.By contrast,the battery with an electrolyte containing 0.03 mol/L Thr demonstrated remarkably enhanced cycling stability.It sustained stable operation for 200 cycles,with a discharge capacity retention of 43.7%at the end of this period,and its average capacity decreased to 2.9 mAh per cycle.This performance is notably superior to that of the pristine electrolyte,not only in terms of absolute capacity retention but also in terms of doubled cycle life under identical testing conditions.In conclusion,this study demonstrates that the introduction of Thr as a complexing and surface-modifying additive is an effective and promising strategy to enhance the reversibility of the chromium electrode and suppress detrimental side reactions in iron-chromium flow batteries.The resulting reaction system exhibits excellent cycling stability and improved capacity retention.The insights gained from combined theoretical calculations and experimental characterizations provide a solid theoretical foundation and a novel design for developing high-stability,high-performance electrolyte systems for iron-chromium and potentially other chromium-based redox flow batteries.This study provides a reference approach for designing electrolyte systems with high stability and low capacity decay in iron-chromium flow batteries.