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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 PF6− 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. [ABSTRACT FROM AUTHOR]

A disadvantage of organic battery electrode materials is their solubility in battery electrolytes, leading to the shuttle effect. One solution is to use an additional separator, the interlayer, to inhibit charge shuttling of the solubilized species. The work here aims to identify the interlayer material's properties critical to reducing the shuttle effect so as to provide some guidance on interlayer material selection. Using various alumina as interlayer materials in batteries with N,N′ -dimethylphenazine (DMPZ) as cathode material, surface charge can be identified as the critical descriptor to inhibiting DMPZ shuttling, more so than morphological properties. Specifically, the interlayer material can be selected for shuttling prevention in the same way as how one chooses chromatography stationary phase for analyte retention. Based on further characterizations, short- and long-term shuttling inhibition can be attributed to the interlayer and the solid-electrolyte interface formed in situ, respectively. Inorganic separators are known to alleviate the deleterious shuttle effect in batteries using molecular electrode materials, including the redox-active organic compounds. We identified here the properties of the interlayer material crucial to inhibiting the shuttle effect and elucidated some mechanistic insights, both useful for rational material selection for improving battery performance. [Display omitted] • Al 2 O 3 interlayer significantly inhibited the shuttle effect of organic batteries. • Efficacy of the Al 2 O 3 interlayer was determined by its Lewis acidity/basicity. • Shuttle effect was prevented by Al 2 O 3 interlayer for both short and long time. • The shuttling protection was realized through dynamic protection mechanism. [ABSTRACT FROM AUTHOR]