Ultrafine CoO Embedded Reduced Graphene Oxide Nanocomposites: A High Rate Anode for Li-Ion Battery

Abstract

A novel and simple strategy for the synthesis of cobalt oxide decorated reduced graphene oxide (CoO-rGO) nanocomposites was developed as a high performance anode for lithium ion battery (LIB). The CoO-rGO nanocomposites were prepared by simultaneous reduction of GO and Co2+ in the presence of NaBH4. Addition of 15 wt% rGO produced a narrow size distribution of ultra-fine CoO nanoparticles with nano-dimensional contact between CoO and rGO leading to an excellent electrochemical performance. The reversible capacity of CoO-rGO nanocomposites is between 1140 and 1260 mAh/g at the current density of 150 mA/g and sustained at 473 mAh/g at high current density of 2400 mA/g. In addition to the excellent rate capability of 15 wt% CoO-rGO, a reversible capacity of 690 mAh/g is achieved at 600 mA/g after 60 cycles. In addition, XPS spectra and XRD patterns of CoO-rGO after cycling clearly indicate the involvement of electrolyte into CoO nanoparticles during intercalation-deintercalation cycling, and lead to the transformation of Co species from Co2+ to Co3+ for the enhanced electrochemical performance at high current density.