Preparation of Positive and Negative Composite Electrode Materials for High-Performance Aqueous Asymmetric Supercapacitor by a Sequential Two-Step Reaction

Aqueous asymmetric supercapacitors with high energy density and long cycle life prepared by simple methods have significant value for applications. Composite electrode materials compounded of redox-active organic materials and graphene composites can combine the advantages of high specific capacity and good conductivity, making them ideal candidates for high-performance aqueous supercapacitors. In this work, positive and negative materials for aqueous asymmetric supercapacitors were prepared by a simple sequential two-step reaction. First, p-phenylene­diamine grafted graphene (PRG), as the positive electrode material, is synthesized by graphene oxide and p-phenylene­diamine through the amidation reaction. Next, graphene/poly(naphthylimide) (PRG@NDI) is prepared by in-situ polymerization of naphthalimide on the PRG surface, which plays the role of the negative electrode material. The PRG undergoes an oxidation reaction during charging, and the PRG@NDI undergoes a reduction reaction simultaneously, which increases the specific capacity of the aqueous asymmetric supercapacitor. Moreover, the interface contact between poly(naphthylimide) and graphene is promoted by covalent bonding, which facilitates charge transport and then imparts high specific capacity and cycling stability. This device can deliver a high energy density of 27.3 Wh kg^–1 at 750 W kg^–1 and remarkable cycling stability with a capacity retention rate of 84.5% after 15,000 cycles.