Flexible Films Derived from Electrospun Carbon Nanofibers Incorporated with Co3O4 Hollow Nanoparticles as Self-Supported Electrodes for Electrochemical Capacitors

Flexible porous films are prepared from electrospun carbon nanofibers (CNFs) embedded with Co3O4 hollow nanoparticles (NPs) and are directly applied as self-supported electrodes for high-performance electrochemical capacitors. Uniform Co3O4 hollow NPs are well dispersed and/or embedded into each CNF with desirable electrical conductivity. These Co3O4-CNFs intercross each other and form 3D hierarchical porous hybrid films. Benefiting from intriguing structural features, the unique binder-free Co3O4 hollow NPs/CNF hybrid film electrodes exhibit high specific capacitance (SC), excellent rate capability and cycling stability. As an example, the flexible hybrid film with loading of 35.9 wt% Co3O4 delivers a SC of 556 F g(-1) at a current density of 1 A g(-1), and 403 F g(-1) even at a very high current density of 12 A g(-1). Remarkably, almost no decay in SC is found after continuous charge/discharge cycling for 2000 cycles at 4 A g(-1). This exceptional electrochemical performance makes such novel self-supported Co3O4-CNFs hybrid films attractive for high-performance electrochemical capacitors.