Production of heteroatom-doped graphen based electrodes and investigation of the anode performance in lithium-ion batteries

The increasing need for energy and mobility, resulted several environmental problems, have revealed the need for efficient use of energy and caused the demand for rechargeable batteries with an rapid increasing manner. Li-ion batteries are the most preferred batteries among rechargeable batteries due to their high capacity and cycle life. Graphene is promising as an electroactive material in electrochemical energy storage devices due to its extraordinary properties. In this study, nitrogen-doped graphene (N-GN) and silicon-nitrogen-doped graphene (Si-N-GN) were synthesized by a solvothermal method and their anode performances were tested in Li-ion batteries. The morphological structures of the products were characterized by energy dispersive scanning electron microscopy (SEM-EDX) and N2 adsorption method, crystal structures by X-ray diffraction (XRD) and Raman spectrometry, and the elemental composition and bonding configurations of the elements were characterized by X-ray photoelectron spectrometry (XPS). Accordingly, it has been observed that N-GN consists of circular-shaped regular micro- and meso pores in which dense stacked graphene layers are interconnected, while Si-N-GN has a structure consisting of multiple graphene plates in dispersed form. Specific surface areas (SBET) for N-GN and Si-N-GN were calculated as 1350 m2/g and 680 m2/g, respectively. According to the XPS results, it was determined that N-GN contains 5.4% (at.) N, Si-N-GN contains 2.5% (at.) N and 5.5% (at.) Si. Within the scope of the studies for the usability of the products as anode in Li-ion batteries, the development of the coating method and the electrolyte and the determination of the appropriate separator were carried out. In the determined optimum parameter and cell components, anode discharge capacities of 980 mAh/g for N-GN and 815 mAh/g for Si-N-GN were reached in which above the theoretical value of graphene.