Ultrahigh volumetric performance of a freestanding compact N-doped holey graphene/PANI slice for supercapacitors

Volumetric capacitance, rate capability and cycling life performance are extremely important metrics for supercapacitors with limited space. Unfortunately, the volumetric performance is relatively inferior for most of the supercapacitors because of their low packing density. Herein, we developed a novel facile strategy to prepare a binder-free and free-standing N-doped holey graphene/PANI slice (HNHG-PANI), which not only possesses a high packing density (1.45 g cm(-3)) but also still maintains a highly interconnected pore connectivity channel for efficient ion transport without compromising electrochemical energy storage. In addition, the nanopores in N-doped holey graphene can immensely accelerate the ion transmission across the entire surface area. The HNHG-PANI material electrode can deliver ultrahigh volumetric capacitance (1058 F cm(-3) at 0.5 A g(-1)), excellent rate performance and long-term cycling stability. Meanwhile, the symmetrical supercapacitor can achieve a high volumetric energy density of 26.5 W h L-1 at an impressive volumetric power density of 175.3 W L-1. Such a densely packed free-standing N-doped holey graphene/PANI slice is an extraordinary promising candidate for compact and miniaturized energy storage equipment in the future. Furthermore, the novel simple strategy method of this paper could be used to synthesize other similar materials for different applications.