Ultrathin MoS2 flakes embedded in nanoporous graphene films for a multi-functional electrode

Abstract

Molybdenum disulfide (MoS₂) is considered a promising material in energy storage systems, and is thus drawing considerable attention. However, the relatively low conductivity of bulk MoS₂ has been a threat for practical applications. This study developed a simple and scalable fabrication method of few-layer MoS₂ sheets embedded in a nanoporous graphene film (NGF) as a high capacitance active material. Transfer of MoS₂/NGF onto a flexible substrate followed by plotter cutting produced a highly efficient micro-supercapacitor with superior flexibility, mechanical stability, and great potential for applications in wearable electronics. Notably, MoS₂/NGF-based mSC revealed a high volumetric capacitance of 55 F cm⁻³ and 82.2% of capacitance retention after 20 000 cycles, which are superior to the reported data for solid-state micro-supercapacitors. With these performances, the flexible MoS₂/NGF mSC exhibited an ultrahigh energy density of 7.64 mW h cm⁻³ and power density of 9.96 W cm⁻³ in a H₃PO₄ gel polymer electrolyte. The high volumetric capacitance and energy/power densities of MoS₂/NGF as micro-supercapacitor electrodes are due to direct growth of ultra-thin MoS₂ onto the interconnected 3D nanoporous graphene film with extended active sites and good conductivity. The MoS₂/NGF mSC integrated on the skin efficiently powered a light emitting diode and strain sensors. This work suggests a meaningful way to realize film type MoS₂ active materials in flexible micro-supercapacitors for wearable applications.