Conjugated polymer electrodes fabricated using rylene-based acceptors toward high energy and power density symmetric supercapacitors operable in an organic electrolyte environment

Abstract

Conjugated polymers with acceptor–acceptor units enable precise tuning of the bandgap by controlling the electrochemical redox properties, making them potential candidates for energy storage applications. Electrodes fabricated by utilising rylene diimide conjugated polymers with multiple acceptor units can leverage their exceptional conductivity, redox activity, and remarkable specific capacitance, along with cycling durability. This study reports conjugated polymers with dual acceptor units using two distinct rylene diimides (NDI, naphthalene diimide, and PDI, perylene diimide) incorporated with a unit of benzothiadiazole (BT), that is, BT-NDI and BT-PDI. According to a comparison of the energy storage performances of the polymers, the BT-PDI polymeric electrode exhibited superior electrochemical performance with a specific capacitance of 196 F g⁻¹, attributed to its porous structure and low band gap resulting from its nonplanar molecular structure, with a capacitance retention of 76% over 5000 cycles at 5 A g⁻¹. Utilizing BT-PDI for the symmetric device in an organic electrolyte yields a high energy density of 52.9 W h kg⁻¹ with a maximum power density of 14.9 kW kg⁻¹ owing to its wide operational potential window. This study expands the field of advanced polymeric electrode materials by exploring the relatively unexplored domain of acceptor–acceptor polymers.