Rapid design of a core–shell-like metal hydroxide/oxide composite and activated carbon from biomass for high-performance supercapattery applications

Abstract

Designing multifunctional and core–shell-like architectures has attracted significant research interest for the enhancement of energy density in supercapatteries owing to their synergistic features of an efficient accessibility of ions and high electrochemical activity. In the present work, we facilely synthesized a nickel hydroxide nanolayer-decorated cuprous oxide custard apple-like structure (Ni(OH)₂ NL@Cu₂O CAS) to form a core–shell-like nanoarchitecture for use as an effective positive electrode in supercapatteries. The as-formed core–shell-like Ni(OH)₂ NL@Cu₂O CAS composite demonstrated a high areal capacity of 59.8 μA h cm⁻² at a current density of 2 mA cm⁻² compared to the bare Cu₂O CAS material (43 μA h cm⁻²), which was mainly due to the versatile oxidation states, high electroactive surface area, improved electrochemical conductivity, and rapid charge transportation of these materials. Utilizing wisteria pod shells as a biomass source, we derived highly porous activated carbon comprising a porous structure for use as a negative electrode material in supercapatteries. The as-obtained biomass-derived activated carbon (BDAC) with numerous pores exhibited good charge-storage performance. Considering the obtained results, a pouch-type supercapattery device was fabricated with a core–shell-like Ni(OH)₂ NL@Cu₂O CAS composite and highly porous BDAC materials as the positive and negative electrodes, respectively in 1 M KOH electrolyte. The as-fabricated device delivered a maximum areal capacitance of 175 mF cm⁻² at a current density of 1 mA cm⁻² with good capacitance retention of 71.7%. Additionally, the device exhibited maximum areal energy and power densities of 0.0538 mW h cm⁻² and 19.665 mW cm⁻², respectively. The feasibility of the fabricated pouch-type supercapattery in real-time applications was also demonstrated by operating a toy motor fan and light-emitting diodes.