Time-dependent exfoliation study of MoS2 for its use as a cathode material in high-performance hybrid supercapacitors

Abstract

Quick and precise exfoliation of bulk molybdenum sulphide into few layers can bring a quantum leap in the electrochemical performance of this material. Such a cost-effective exfoliation route to obtain few layers of MoS₂ nanosheets with a high mass yield of ∼75% is presented in this study. The electrochemical behaviours of three types of samples, namely pristine MoS₂ and MoS₂ exfoliated for 3 h and 5 h, were compared and the reasons leading to their performance modulation are explained. The performance could be tuned by changing the nature of the electrolytes, as shown using three different electrolytes, i.e. H₂SO₄, Na₂SO₄, and KOH. The electrochemical performance of a supercapacitor device fabricated using the 5 h-exfoliated sample showed many fold improvement. The strategy of combining with a 2D material-based anode is an interesting way forward for such devices. In addition, the anode material has to be carefully chosen so that high performance can be ensured. The usefulness of 2D flake-like WO₃ as an anode was investigated first before establishing its worthiness in a hybrid device. The hybrid device was able to deliver an excellent energy density of 33.74 W h kg⁻¹ with long-term cycling stability and coulombic efficiency, thus proving its applicability for high-performance energy-storage devices.