2D nanosheets-based composite materials for supercapacitors

Abstract

Efficient energy storage systems are the key to future higher operating demands in a variety of applications such as portable electronics devices and hybrid electric vehicles. Supercapacitor is one of the promising next-generation energy storage devices. Though supercapacitors possess high power capability, their energy densities are still far to be comparable with batteries. Intense research efforts have been attracted in the research of supercapacitors that can yield both high specific power and energy densities. Conducting polymers are one of the spotlight materials for supercapacitors owing to their low-cost, facile synthesis and high capacitance. However, one of the major drawbacks of conducting polymers that hampers its practical use in supercapacitors is poor stability during cycling caused by mechanical degradation of material during the doping/de-doping processes.

In this project, we designed and synthesized different polypyrrole (PPy)-nanosheets based composites for high-performance supercapacitors with enhanced cycle stability. Four kinds of two-dimensional nanosheets, MoS2, TiS2, GO and TaS2 were incorporated into PPy system on Indium Tin Oxide (ITO) and graphite substrates by electrochemical copolymerization method. Their electrochemical polymerization process, electrochemical properties and supercapacitor performance were studied with pure PPy film as reference.

We conclude that PPy/GO composite film on graphite showed the best performance among the four PPy based composite films with enhanced specific capacitance of 120.3 F g-1 compared to that of pure PPy with 97.6 F g-1 at 0.5 A g-1 current density in a three-electrode electrochemical system. Moreover, excellent device stability was obtained on all four systems with PPy/GO exceeded 10000 charge-discharge cycles without losing capacitance. Extensive studies are required to further understand the PPy/nanosheets composite system and to achieve a practical device performance.