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Uncovering the Shuttle Effect in Organic Batteries and Counter‐Strategies Thereof: A Case Study of the N , N′ ‐Dimethylphenazine Cathode
Author(s) -
Lau Vincent Winghei,
Moudrakovski Igor,
Yang Junghoon,
Zhang Jiliang,
Kang YongMook
Publication year - 2020
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201912587
Subject(s) - cathode , faraday efficiency , electrolyte , anode , solubility , chemistry , electrochemistry , battery (electricity) , electrode , inorganic chemistry , chemical engineering , organic chemistry , thermodynamics , power (physics) , physics , engineering
The main drawback of organic electrode materials is their solubility in the electrolyte, leading to the shuttle effect. Using N,N′‐dimethylphenazine (DMPZ) as a highly soluble cathode material, and its PF 6 − and triflimide salts as models for its first oxidation state, a poor correlation was found between solubility and battery operability. Extensive electrochemical experiments suggest that the shuttle effect is unlikely to be mediated by molecular diffusion as commonly understood, but rather by electron‐hopping via the electron self‐exchange reaction based on spectroscopic results. These findings led to two counter‐strategies to prevent the hopping process: the pre‐treatment of the anode to form a solid–electrolyte interface and using DMPZ salt rather than neutral DMPZ as the active material. These strategies improved coulombic efficiency and capacity retention, demonstrating that solubility of organic materials does not necessarily exclude their applications in batteries.