Engineering layer structure of MoS2-graphene composites with robust and fast lithium storage for high-performance Li-ion capacitors

Abstract

Two dimensional layered MoS2 has demonstrated great promise as an ideal alternative to graphite-based anodes for hybrid Li-ion capacitors and Li-ion batteries. Research effort on this material has focused mainly on synthesizing highly nanostructured MoS2 that allows reducing the dimensions into nanoscale to cross over the sluggish kinetics of Li-ion charge storage. Herein, we engineer the layer structure of MoS2 to preferentially expand the interlayer distance to increase atomic interface contact/interaction by successfully inserting amorphous carbon layer into adjacent MoS2 monolayers. This interlayer modified MoS2 is demonstrated to have the predominantly pseudocapacitive characteristics and can get further gains in Li-ion storage properties through incorporating reduced graphene oxide (RGO). Thus, a novel hybrid Li-ion capacitor is fabricated by employing this MoS2-RGO composite as the anode and activated carbon as the cathode, which exhibits an ultrahigh specific energy density of 188Whkg-1 at 200Wkg-1 and remains 45.3Whkg-1 even at a high specific power density of 40,000Wkg-1 as well as long cycle life. This work shows that engineering interlayer structure and introducing conductive graphene can significantly impact the Li-ion storage properties, enabling new opportunities for designing newly advanced MoS2 anodes for next-generation energy storage devices.