Preparation And Properties Of Graphene Li-ion Battery Cathode Materials Research

Lithium-ion battery has been widely used in portable electronic devices, and it has great potential applications in electric bicycles and electric vehicles. As a typical commercial anode material for lithium-ion battery, graphite has a theoretical specific capacity of372mAh/g. Compared to the conventional graphite anode material, graphene or reduced graphene oxide (RGO) has larger specific surface area, better electrical conductivity, more excellent lithium-ion insertion and extraction, and larger specific capacity, which make it as a good candidate anode material for lithium-ion battery.For RGO as anode material of lithium-ion battery, the structure and properties of the graphite oxide (GO) by a modified Hummers method and RGO under various oxidation and reduction conditions were investigated in this thesis. Then the electrochemical properties of the graphene anode material was evaluated. The main content and conclusions of this thesis are summarized as follows.(1) The morphology, structure and composition of GO and RGO under various oxidation conditions were investigated. The results show that the regular structure of graphite was replaced by a random, aggregating, thin and wrinkling structure of GO, which is suitable for the subsequent reduction. The optimized oxidation process is as follows. The low temperature oxidation reaction is kept at ice bath for half an hour, then the medium temperature oxidation reaction is held at35℃℃water bach for two hours, finally the high temperature oxidation reaction is held at90℃water bath for one hour. The XRD results show that the obtained GO shows a strong (001) peak and the oxygen content is as high as21.5%. The corresponding RGO has a higher degree of reduction with a carbon/oxygen atomic ratio of5.24and a large specific surface area of423.2m2/g.(2) The structure and properties of GO and RGO by NaBH4wet reduction and microwave dry reduction were studied. The results show that the contents of carbon and oxygen of the RGO reduced by NaBH4were81.76%and18.24%, respectively, while corresponding values reduced by microwave were83.97%, and16.03%, respectively, which indicates higher RGO quality can be obtained by microwave dry reduction.(3) The electrochemical properties of lithium-ion battery with RGO anode and metallic lithium as the cathode were investigated. The results show that RGO anode demonstrates good electrochemical properties. The specific discharge and charge capacities of RGO at the first cycle were as high as1555.5mAh/g and1024.6mAh/g, and the discharge specific capacity was still kept as high as600mAh/g after30cycles.