Metallic Phase MoS2-Graphene Composite for High Performance Coin Cells Supercapacitors

Tuesday, 30 May 2017
Grand Ballroom (Hilton New Orleans Riverside)
A. E. Aynalem (University of Manchester), R. A. Dryfe (School of Chemistry, University of Manchester), and I. A. Kinloch (School of Materials, University of Manchester)
Molybdenum disulphide exhibits two possible crystal states, the naturally occurring semiconducting phase (2H-MoS2), and the non-naturally occurring metallic state (1T-MoS2) which can be prepared by intercalation chemistry.1 The metallic 1T phase has a conductivity up to 107 times higher than the 2H phase.2 Consequently, metallic phase MoS2 nanosheets are very attractive for a number of electrochemical applications including supercapacitor electrodes and catalysts for hydrogen evolution.2, 3 For example, Acerce et al. recently demonstrated that the gravimetric capacitance of chemically exfoliated 1T-MoS2 was 20 times higher than the gravimetric capacitance of the 2H-MoS2.2

In this work, we compare the capacitive behaviour of 1T-MoS2, 2H-MoS2, graphene and 1T-MoS2/graphene composite using symmetrical coin cell architecture. The electrodes were prepared by filtering a known volume of the respective dispersion over pre-weighed polyvinylidene fluoride membrane using syringe pump dispenser. The gravimetric capacitance of 1T-MoS2 was over 100 F g-1 in aqueous solution which is higher than the gravimetric capacitance obtained using 2H-MoS2 or graphene electrodes. The capacitance performance of 1T-MoS2 was further enhanced by making a composite electrode with highly conducting graphene. A volumetric capacitance of over 560 F cm-3 in an aqueous solution and 250 F cm-3 in a non-aqueous solution were achieved using these composite electrodes. The composite electrode displayed capacity retention of over 90 % after 5,000 cycles. The enhanced capacitance in the composite material was probably due to a synergistic effect between 1T-MoS2 and graphene where graphene enhances the overall conductivity of the composite whilst also reducing the re-aggregation of the sheets.

1. M. A. Py and R. R. Haering, Can. J. Phys., 1983, 61, 76-84.

2. M. Acerce, D. Voiry and M. Chhowalla, Nat. Nanotechnol., 2015, 10, 313-318.

3. M. A. Lukowski, A. S. Daniel, F. Meng, A. Forticaux, L. S. Li and S. Jin, J. Am. Chem. Soc., 2013, 135, 10274-10277.