SP3 Hybridized Carbon Atom Dependent Redox Activity and Charge Storage of Quinonoid Main Chain Polymers

Abstract

Uncontrolled stereochemical flipping of the substituents indirectly affects the redox chemistry of benzoquinone. With this assumption, herein we prepared three different polymers, quinone rings directly bonded (DHBP), quinone rings boned through a methylene bridge (DHB), and phenyl rings substituted methylene bridge (DADC). The substitution of phenyl ring generates the stereo-centered sp3 hybridized carbon center which inhibits ring flipping and uncontrolled stereochemistry. It also affects the electrochemical properties and charge storage ability of the polymer. The polymer with a stereo-centered carbon center (DADC) exhibited 245.4 mAhg−1 specific capacity at 100 mAg−1 current density in an aqueous zinc ion battery. It is far better than the polymers without the stereo-centered polymer, even it is better than the reported quinone cathodes. The outperformance in the charge storage ability was explained in detail based on the stabilization of quinonoid radicals and/or quinonoid anions by the stereochemically restricted carbon center with a bulky phenyl group. The cycling stability was evaluated in galvanostatic charging/discharging over 3000 cycles at 100 mAg−1 current density. The specific capacity was found to be 250.1 mAhg−1 with 91.2% capacity retention and 89.6% coulombic efficiency suggesting the importance of stereo-centered carbon in designing new redox-active organic molecules for energy storage applications.