Energy storage behavior of side chain-engineered Si-bridged redox-active donor–acceptor conjugated polymers operated in organic electrolytes

Abstract

Structurally modulated donor–acceptor (D–A) moieties are key constituents in designing redox-active conjugated polymers (RACPs), which serve as promising pseudocapacitive electrode materials due to their broad potential windows, superior redox behavior, and tunable electronic properties. Herein, we introduce silylethynyl-functionalized benzodithiophene (Si-BDT), a planar donor moiety developed by lateral side-chain engineering, copolymerized with rylene diimide acceptors, naphthalene diimide (NDI) and perylene diimide (PDI), synthesized by the Stille cross-coupling polymerization reaction. The supercapacitor performance of these polymers was assessed in two organic-salt electrolytes, tetrabutylammonium hexafluorophosphate (TBAPF₆) and tetraethylammonium tetrafluoroborate (TEABF₄). The computational analysis explored non-covalent interaction (NCI) between the electrode and electrolyte and confirmed that both electrodes exhibited a stronger interaction with TBAPF₆, thereby facilitating improved charge transfer and electrochemical performance. Both electrodes were operated within a wide potential window of −1.7 to 0.7 V. Si-BDT-PDI outperformed Si-BDT-NDI, achieving a higher specific capacity of 267 C g⁻¹ at 1 A g⁻¹ due to electrode–electrolyte interactions enhanced by several topographic pores. Furthermore, a hybrid supercapacitor integrating a Si-BDT-PDI anode and a porous activated carbon cathode achieved an outstanding energy density of 55 W h kg⁻¹ and a power density of 13 380 W kg⁻¹ across a 2.7 V potential window.