Hydroquinone ethers are a key class of catholyte materials for non-aqueous redox flow batteries, showing high open-circuit potential, electrochemical reversibility and chemical tunability. However, the instability of many hydroquinone ethers, particular to electrochemical oxidation, limits their applicability. 2,5-dialkylation of the benzene core has been by far the only effective chemical approach to suppress the side reactions of the corresponding radical cations, restricting the chemical space of structures from which to choose. This talk will describe a bicyclo-alkyl substitution strategy that yields a hydroquinone ether with unprecedentedly high electrochemical stability. The influences of different substituents on the electrochemical properties are investigated. The electrochemical stability is determined via a full flow cell using a benzothiadiazole-based anolyte. In addition, the low impedance shown in the single electrolyte flow cell indicates its great promises as catholyte for high-performance non-aqueous redox flow batteries.