Abstract
Cobalt oxide is a promosing electrode material for lithium ion battery because of the high theoretical capacity of 715 mAh/g. In addition, cobalt oxide can proceed another electrolyte catalyzation to provide additional capacity. However, the lithium ions and electrons can not be easily moved through the CoO particles and lithium oxide byproducts when the cobalt oxide particle is large, resulting in the decrease in capacity as the current density increases. Addition of dispersing agents and the decrease in particle size of CoO can improve the transportation of lithium ions and electrons. .However, the decrease in total amounts of CoO also decrease the overall capacity of the CoO nanocomposite. In this study, a novel fabrication method has been developed to synthesize ultrafine CoO nanopaticles and then deposited onto the surface of reduced graphene oxide (CoO/rGO) to maintain the CoO amount as well as to increase the electrochemical reaction efficiency simultaneously. We used a simple and facile aqueous system to produce CoO after the heat treatment of Co3(BO3)2. Since the oxy group on the graphene surface can bond to the metal and boron element, resulting in the separation of CoO particle during the heat treatment. After optimizing the heat treatment time 1 hour in N2 gas and cobalt oxide amount 80 wt% in rGO composite, XRD showed the nano grain size lower than 10 nm, and TEM images showed that particle sizes of CoO was lower than 10 nm and can well disperse in the rGO.Because of the small particle size, The EIS showed the SEI impedance and charge transfer resistance are only 56.2 Ω.After the charge/discharge test, CoO/rGO capacity was up to 500 mAh/g when current rate was 2400 mA/g. In addition, a 60% of retention was obtaiend when the current was 150 mA/g. In the future, It can produce high loading amount and small particle of other metal or metal oxide through the metal borate decomposition. It can improve zero valent metal or metal oxide application through this method