Defects enriched cobalt molybdate induced by carbon dots for a high rate Li-ion battery anode

Abstract

A defects-enriched CoMoO4/carbon dot (CD) with CoMoO4 around 37 nm is achieved via hydrothermal reaction by introducing CDs to buffer large volume changes of CoMoO4 during lithiation–delithiation and enhance rate performance. The phase, morphology, microstructure, as well as the interface of the CoMoO4/CD composites were investigated by x-ray diffraction, scanning electron microscopy, transmission electron microscopy and x-ray photoelectron spectroscopy. When employed as Li-ion battery anode, the CoMoO4/CD exhibits a reversible capacity of ∼531 mAh g−1 after 400 cycles at a current density of 2.0 A g−1. Under the scan rate at 2 mV s−1, the CoMoO4/CD shows accounts for 81.1% pseudocapacitance. It may attribute to the CoMoO4 with surface defects given more reaction sites to facilitate electrons and lithium ions transfer at high current densities. Through galvanostatic intermittent titration technique, the average lithium ion diffusion coefficient calculated is an order of magnitude larger than that of bulk CoMoO4, indicating that the CoMoO4/CD possesses promising electrons and lithium ions transportation performance as anode material.