Effect of in-plane size of MoS2 nanoparticles grown over multilayer graphene on the electrochemical performance of anodes in Li-ion batteries

Electrochemical performance of MoS2/graphene materials in Li-ion batteries is strongly dependent on the structure of individual components and their coupling in the hybrid. We present a comparative study of the materials produced by annealing of amorphous MoS3 deposited on the surface of multilayer graphene flakes at 500 degrees C, 800 degrees C, and 1000 degrees C in vacuum. X-ray photoelectron spectroscopy confirmed a transformation of MoS3 to MoS2 at these conditions. High-resolution transmission electron microscopy and Raman scattering showed a growth of in-plane size of MoS2 nanocrystals with a raise of annealing temperature. Electrochemical tests detected a gradual decrease of the specific capacity of the MoS2/graphene materials prepared at 500 and 800 degrees C and a stable performance for the material synthesized at 1000 degrees C even at high current densities. Based on the initial discharge-charge profiles, we associate this effect with in-plane size of MoS2 nanocrystals, which should decompose more easily when the size is small, due to the interaction of lithium with edge sulfur atoms. (C) 2018 Elsevier Ltd. All rights reserved.