Annealing-Assisted Dip-Coating Synthesis of Ultrafine Fe<sub>3</sub>O<sub>4</sub> Nanoparticles/Graphene on Carbon Cloth for Flexible Quasi-Solid-State Symmetric Supercapacitors
Siyu Su, Liuqin Lai, Rong Li, Yueming Lin, Huimin Dai, Xiaohong Zhu
Abstract
With the rapid development of science and technology, traditional supercapacitors have become increasingly difficult to support applications in various scenarios; therefore, the development of flexible solid-state supercapacitors is critical to meet future needs. In this work, we propose an efficient and controllable annealing-assisted dip-coating method to prepare ultrafine Fe3O4 nanoparticles/graphene on carbon cloth and use it directly as a supercapacitor electrode without any subsequent operations and extra additives. When tested in three-electrode systems, this electrode exhibits excellent electrochemical performance, such as considerable specific capacitance (406 F g–1 at 1 A g–1), high rate capability (retention of 56.9% when the current density is increased 20-fold from 1 to 20 A g–1), and prolonged cycle life (retention of 94.0% after 3200 consecutive cycles). Moreover, the assembled flexible quasi-solid-state symmetric supercapacitor has excellent flexibility (no obvious degradation in performance after being folded at 45, 90, 135, and 180°), high energy density of 19.2 W h kg–1 at 800.2 W kg–1, great power density of 8614.7 W kg–1 at 10.7 W h kg–1, and prominent cyclic stability (no decay after 4000 cycles at 1 A g–1). These results demonstrate the feasibility and superiority of this synthesis method, as well as its potential for practical applications.