Premium
Designing Redox‐Stable Cobalt–Polypyridyl Complexes for Redox Flow Batteries: Spin‐Crossover Delocalizes Excess Charge
Author(s) -
Yang Chunzhen,
Nikiforidis Georgios,
Park Ji Young,
Choi Jonghoon,
Luo Yong,
Zhang Liang,
Wang ShiCheng,
Chan YiTsu,
Lim Jihun,
Hou Zhaomin,
Baik MuHyun,
Lee Yunho,
Byon Hye Ryung
Publication year - 2018
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201702897
Subject(s) - redox , rational design , materials science , chemical physics , spin crossover , cobalt , combinatorial chemistry , molecule , electrolyte , denticity , nanotechnology , computational chemistry , chemistry , inorganic chemistry , electrode , organic chemistry , metal , metallurgy
Redox‐active organometallic molecules offer a promising avenue for increasing the energy density and cycling stability of redox flow batteries. The molecular properties change dramatically as the ligands are functionalized and these variations allow for improving the solubility and controlling the redox potentials to optimize their performance when used as electrolytes. Unfortunately, it has been difficult to predict and design the stability of redox‐active molecules to enhance cyclability in a rational manner, in part because the relationship between electronic structure and redox behavior has been neither fully understood nor systematically explored. In this work, rational strategies for exploiting two common principles in organometallic chemistry for enhancing the robustness of pseudo‐octahedral cobalt–polypyridyl complexes are developed. Namely, the spin‐crossover between low and high‐spin states and the chelation effect emerging from replacing three bidentate ligands with two tridentate analogues. Quantum chemical models are used to conceptualize the approach and make predictions that are tested against experiments by preparing prototype Co‐complexes and profiling them as catholytes and anolytes. In good agreement with the conceptual predictions, very stable cycling performance over 600 cycles is found.