Advanced Asymmetrical Supercapacitors Based on Graphene Hybrid Materials

TL;DR

This paper develops high-performance asymmetrical supercapacitors using graphene hybrid materials with Ni(OH)2 and RuO2, achieving high energy and power densities in aqueous solutions.

Contribution

It introduces a novel pairing of Ni(OH)2/graphene and RuO2/graphene electrodes for supercapacitors, significantly improving energy density over existing symmetrical and hybrid designs.

Findings

Achieved ~48Wh/kg energy density at 0.23kW/kg power density.

Realized ~21kW/kg power density at ~14Wh/kg energy density.

Demonstrated superior performance of asymmetrical supercapacitors over symmetrical counterparts.

Abstract

Supercapacitors operating in aqueous solutions are low cost energy storage devices with high cycling stability and fast charging and discharging capabilities, but have suffered from low energy densities. Here, we grow Ni(OH)2 nanoplates and RuO2 nanoparticles on high quality graphene sheets to maximize the specific capacitances of these materials. We then pair up a Ni(OH)2/graphene electrode with a RuO2/graphene electrode to afford a high performance asymmetrical supercapacitor with high energy and power densities operating in aqueous solutions at a voltage of ~1.5V. The asymmetrical supercapacitor exhibits significantly higher energy densities than symmetrical RuO2-RuO2 supercapacitors and asymmetrical supercapacitors based on either RuO2-carbon or Ni(OH)2-carbon electrode pairs. A high energy density of ~48Wh/kg at a power density of ~0.23kW/kg, and a high power density of ~21kW/kg at an energy density of ~14Wh/kg have been achieved with our Ni(OH)2/graphene and RuO2/graphene asymmetrical supercapacitor. Thus, pairing up metal-oxide/graphene and metal-hydroxide/graphene hybrid materials for asymmetrical supercapacitors represents a new approach to high performance energy storage.