Xiaojun Zhao , Xinwei Niu , Xinyuan Liu , Chongchong Wu , Xinyu Duan , Zhiqi Ma , Yan Xu , Hao Li , Weijie Yang
{"title":"Unraveling the coordination behavior and transformation mechanism of Cr3+ in Fe–Cr redox flow battery electrolytes","authors":"Xiaojun Zhao , Xinwei Niu , Xinyuan Liu , Chongchong Wu , Xinyu Duan , Zhiqi Ma , Yan Xu , Hao Li , Weijie Yang","doi":"10.1016/j.matre.2024.100271","DOIUrl":null,"url":null,"abstract":"<div><p>Currently, the iron chromium redox flow battery (ICRFB) has become a research hotspot in the energy storage field owing to its low cost and easily-scaled-up. However, the activity of electrolyte is still ambiguous due to its complicated solution environment. Herein, we performed a pioneering investigation on the coordination behavior and transformation mechanism of Cr<sup>3+</sup> in electrolyte and prediction of impurity ions impact through quantum chemistry computations. Based on the structure and symmetry of electrostatic potential distribution, the activity of different Cr<sup>3+</sup> complex ions is confirmed as [Cr(H<sub>2</sub>O)<sub>5</sub>Cl]<sup>2+</sup> > [Cr(H<sub>2</sub>O)<sub>4</sub>Cl<sub>2</sub>]<sup>+</sup> > [Cr(H<sub>2</sub>O)<sub>6</sub>]<sup>3+</sup>. The transformation mechanism between [Cr(H<sub>2</sub>O)<sub>6</sub>]<sup>3+</sup> and [Cr(H<sub>2</sub>O)<sub>5</sub>Cl]<sup>2+</sup> is revealed. We find the metal impurity ions (especially Mg<sup>2+</sup>) can exacerbate the electrolyte deactivation by reducing the transformation energy barrier from [Cr(H<sub>2</sub>O)<sub>5</sub>Cl]<sup>2+</sup> (24.38 kcal mol<sup>−1</sup>) to [Cr(H<sub>2</sub>O)<sub>6</sub>]<sup>3+</sup> (16.23 kcal mol<sup>−1</sup>). The solvent radial distribution and mean square displacement in different solvent environments are discussed and we conclude that the coordination configuration limits the diffusivity of Cr<sup>3+</sup>. This work provides new insights into the activity of electrolyte, laying a fundamental sense for the electrolyte in ICRFB.</p></div>","PeriodicalId":61638,"journal":{"name":"材料导报:能源(英文)","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666935824000351/pdfft?md5=9104e846422c7f7b37e3e254dfdfe55a&pid=1-s2.0-S2666935824000351-main.pdf","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"材料导报:能源(英文)","FirstCategoryId":"1087","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S2666935824000351","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
Currently, the iron chromium redox flow battery (ICRFB) has become a research hotspot in the energy storage field owing to its low cost and easily-scaled-up. However, the activity of electrolyte is still ambiguous due to its complicated solution environment. Herein, we performed a pioneering investigation on the coordination behavior and transformation mechanism of Cr3+ in electrolyte and prediction of impurity ions impact through quantum chemistry computations. Based on the structure and symmetry of electrostatic potential distribution, the activity of different Cr3+ complex ions is confirmed as [Cr(H2O)5Cl]2+ > [Cr(H2O)4Cl2]+ > [Cr(H2O)6]3+. The transformation mechanism between [Cr(H2O)6]3+ and [Cr(H2O)5Cl]2+ is revealed. We find the metal impurity ions (especially Mg2+) can exacerbate the electrolyte deactivation by reducing the transformation energy barrier from [Cr(H2O)5Cl]2+ (24.38 kcal mol−1) to [Cr(H2O)6]3+ (16.23 kcal mol−1). The solvent radial distribution and mean square displacement in different solvent environments are discussed and we conclude that the coordination configuration limits the diffusivity of Cr3+. This work provides new insights into the activity of electrolyte, laying a fundamental sense for the electrolyte in ICRFB.