Electrostatically Charged MoS/Graphene Oxide Hybrid Composites for Excellent Electrochemical Energy Storage Devices.

We demonstrate, for the first time, a new method of fabricating hybrid MoS/poly(ethyleneimine)-modified graphene oxide (PEI-GO) composites assembled through electrostatically charged interaction between the negatively charged MoS nanosheets and positively charged PEI-GO in an aqueous solution. The GO can not only improve the electronic conductivity of the MoS/PEI-GO composites, leading to an excellent charge-transfer network, but also hamper the restacking of MoS nanosheets. The composition ratios between MoS and PEI-GO were also optimized with the highest specific capacitance of 153.9 F g where 96.0% of the initial specific capacitance remains after 6800 cycles. The specific capacitance of only 117.5 F g was observed for the pure MoS nanosheets, and 68.2% of the initial specific capacitance was achieved after 5000 cycles. The excellent electrochemical performance of the hybrid MoS/PEI-GO composites was demonstrated by establishing an asymmetric supercapacitor with a MoS/PEI-GO-based negative electrode and an activated-carbon positive electrode. The asymmetric supercapacitor provided a maximum capacitance of 42.9 F g, and 93.1% of the initial capacitance was maintained after 8000 cycles. Furthermore, a MoS/PEI-GO//activated-carbon asymmetric supercapacitor delivered an energy density of 19.3 W h kg and a power density of 4500 W kg, indicating the potential of the hybrid MoS/PEI-GO composites in electrochemical energy storage applications.