Ultra-fast rate capability of a symmetric supercapacitor with a hierarchical Co3O4 nanowire/nanoflower hybrid structure in non-aqueous electrolyte

Abstract

A free standing Co₃O₄ nanowire/nanoflower hybrid structure on flexible carbon fibre cloth (CFC) was designed via a facile hydrothermal approach followed by thermal treatment in air. The Co₃O₄ hybrid structure on CFC showed interesting electrochemical performance in both alkaline and organic electrolytes when used as electrodes for symmetric supercapacitors. Compared to conventional alkaline electrolytes, the fabricated symmetric cell in organic electrolyte has delivered a high rate and cyclic performance. A supercapacitor made from this hierarchical hybrid architecture showed a maximum specific capacitance of 4.8 mF cm⁻² at a constant density of 3 mA cm⁻² in organic electrolyte. In terms of energy and power, the symmetric supercapacitor conveyed an energy density of 4.2 mW h cm⁻³ with a power density of 1260 mW cm⁻³. Also, the device exhibited reasonable tolerance for mechanical deformation under bended conditions demonstrating the flexibility of the materials. The impressive electrochemical activity is mainly attributed to their high surface area (60.3 m² g⁻¹) resulting from their nano/mesoporous structure; reasonable electrical conductivity resulted from binder-free and intimate metal oxide/substrate integration and superior flexibility of the carbon fibre cloth. Thereby, it was concluded that the direct growth of the Co₃O₄ nanostructure on CFC is a promising electrode for the advanced flexible energy storage devices regardless of the electrolyte.