Electrochemical performance of interspace-expanded molybdenum disulfide few-layer

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.