Stable, Impermeable Hexacyanoferrate Anolyte for Nonaqueous Redox Flow Batteries

Yuyue Zhao, Sambasiva R. Bheemireddy, Diqing Yue, Zhou Yu, Mohammad Afsar Uddin, Haoyu Liu, Zhiguang Li, Xiaoting Fang, Xingyi Lyu, Garvit Agarwal, Zhangxing Shi, Lily A. Robertson, Lei Cheng, Tao Li, Rajeev S. Assary, Venkat Srinivasan, Susan J. Babinec, Zhengcheng Zhang, Jeffrey S. Moore, Ilya A. ShkrobXiaoliang Wei, Lu Zhang

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Redox-active molecules, or redoxmers, in nonaqueous redox flow batteries often suffer from membrane crossover and low electrochemical stability. Transforming inorganic polyionic redoxmers established for aqueous batteries into nonaqueous candidates is an attractive strategy to address these challenges. Here we demonstrate such tailoring for hexacyanoferrate (HCF) by pairing the anions with tetra-n-butylammonium cation (TBA+). TBA3HCF has good solubility in acetonitrile and >1 V lower redox potential vs the aqueous counterpart; thus, the familiar aqueous catholyte becomes a new nonaqueous anolyte. The lowering of redox potential correlates with replacement of water by acetonitrile in the solvation shell of HCF, which can be traced to H-bond formation between water and cyanide ligands. Symmetric flow cells indicate exceptional stability of HCF polyanions in nonaqueous electrolytes and Nafion membranes completely block HCF crossover in full cells. Ion pairing of metal complexes with organic counterions can be effective for developing promising redoxmers for nonaqueous flow batteries.

Original languageEnglish
Pages (from-to)4273-4279
Number of pages7
JournalACS Energy Letters
DOIs
StateAccepted/In press - 2024
Externally publishedYes

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