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General Design Methodology for Organic Eutectic Electrolytes toward High‐Energy‐Density Redox Flow Batteries
Author(s) -
Zhang Changkun,
Chen Hui,
Qian Yumin,
Dai Gaole,
Zhao Yu,
Yu Guihua
Publication year - 2021
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.202008560
Subject(s) - eutectic system , redox , materials science , electrolyte , solubility , density functional theory , energy storage , ferrocene , chemical engineering , electrochemistry , inorganic chemistry , organic chemistry , computational chemistry , thermodynamics , chemistry , electrode , alloy , physics , engineering , metallurgy , composite material , power (physics)
By virtue of strong molecular interactions, eutectic electrolytes provide highly concentrated redox‐active materials without other auxiliary solvents, hence achieving high volumetric capacities and energy density for redox flow batteries (RFBs). However, it is critical to unveil the underlying mechanism in this system, which will be undoubtedly beneficial for their future research on high‐energy storage systems. Herein, a general formation mechanism of organic eutectic electrolytes (OEEs) is developed, and it is found that molecules with specific functional groups such as carbonyl (CO), nitroxyl radical (NO•), and methoxy (OCH 3 ) groups can coordinate with alkali metal fluorinated sulfonylimide salts (especially for bis(trifluoromethanesulfonyl)imide, TFSI), thereby forming OEEs. Molecular designs further demonstrate that the redox‐inactive methoxy group functionalized ferrocene derivative maintains the liquid OEE at both reduced and oxidized states. Over threefold increase in solubility is obtained (2.8 m for ferrocene derivative OEE) and high actual discharge energy density of 188 Wh L ‐1 (75% of the theoretical value) is achieved in the Li hybrid cell. The established mechanism presents new ways of designing desirable electrolytes through molecular interactions for the development of high‐energy‐density organic RFBs.