Molybdenum Disulfide/Carbon Composites for Lithium Ion Batteries

The rapid development of personalized, portable and wearable electronic devices calls for high performance lithium-ion batteries (LIBs). Molybdenum disulfide (MoS2), a representative two-dimensional (2D) transition metal dichalcogenides (TMDs) material, is a promising anode material with a high theoretical capacity of 670 mAh g-1. However, it suffers from low conductivity, restacking problem and volume changes that limit its commercial application. The goal of this thesis is to develop high-performance porous MoS2/carbon materials (MC) anodes for LIBs, by applying the strategies of creating a 3D porous structure and incorporating with carbon materials. A 3D porous structure with large surface area can not only facilitate electrolyte ions diffusion but also accommodate the volume changes of MoS2. The incorporated carbon materials are able to separate MoS2 layers thus suppressing their restacking problem as well as act as fast electrons pathways with an enhanced conductivity. The excellent mechanical properties of carbon materials also facilitate the realization of good flexibility in MC film electrodes for flexible batteries. In this thesis, two types of materials, MoS2/nitrogen-doped carbon nanotubes (MoS2/CNT) nanocomposites and freestanding flexible MoS2/reduced graphene oxide (MoS2/rGO) films, have been developed. Polypyrrole (PPy) and liquid crystalline graphene oxide (LCGO) are employed as the carbon sources to produce nitrogen-doped carbon and rGO for their incorporation with MoS2, respectively. Combined with the created 3D porous structures, these MC composites all demonstrate a greatly improved electrochemical performance. Most importantly, a facial LCGO-based self-assembly process is developed for fabricating freestanding, flexible and porous MoS2/rGO films.