Electrochemical performance of interspace-expanded molybdenum disulfide few-layer

Abstract

Interspace-expanded molybdenum disulfide (IE-MoS2) has been designed as a supercapacitor electrode material to improve the cycling stability. IE-MoS2 was formed through the ultrasound exfoliation of the interspace-compacted molybdenum disulfide (IC-MoS2), which was initially prepared through hydrothermal synthesis using Na2MoO4 as molybdenum source and CH4N2S as sulfur source. As-formed IE-MoS2 shows a few-layer structure with approximate 8–16 monolayer packing and monolayer distance of 0.83 nm. The MoS2 few-layer distance increased from 12 nm of IC-MoS2 to 20 nm for IE-MoS2. The specific capacitance was determined to be 108 F g−1 for IC-MoS2 to 192 F g−1 for IE-MoS2 at 0.5 A g−1. The improved specific capacitance was ascribed to more active sulfur atom exposed at the edges of IE-MoS2 few-layer to conduct the promoted proton attachment reaction. IE-MoS2 showed the capacity retention of 42% when the current density increased from 0.5 to 10 A g−1, presenting the high-rate capability. IE-MoS2 achieved the capacity retention of 116% at 10 A g−1 after 5000 charge-discharge cycles, which was ascribed to the electro-activation of the few-layer expanded MoS2 in proton acid electrolyte solution. IE-MoS2 exhibited the obviously improved cycling stability in comparison with IC-MoS2. All solid-state IE-MoS2 supercapacitor based on two symmetric IE-MoS2 electrodes and H2SO4-PVA gel electrolyte exhibited the energy density of 18.75 Wh kg−1 and power density of 375 W kg−1 at 0.5 A g−1 and high voltage window of 1.5 V. IE-MoS2 supercapacitor also exhibited the improved capacity retention of 110% after 1000 charge-discharge cycles. Such well-designed IE-MoS2 few-layer with highly improved cycling stability performance presented the promising energy storage application.