Significant role of “burned” graphene in determining the morphology of LiNiO2 prepared under the air conditions

A novel finding, that the “burned” graphene has a significant role in determining the morphology of the resultant LiNiO2 nanoparticles prepared under the air conditions, was reported in this work. Briefly, prior to the calcination-preparation of LiNiO2, a series of graphene with various weight contents (0.5 wt %, 1 wt %, 1.5 wt % and 2 wt %) were added in the starting materials of LiNiO2, and then followed by a subsection calcination method under the air conditions. The obtained samples were thoroughly characterized by using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscope (TEM) and Fourier transform infrared spectroscopy (FTIR). It was found that when the “burned” content of graphene is below 2 wt %, LiNiO2 particles with an average size ranging from about 100 to 500 nm were demonstrated to have regular crystal structures. Results obtained from the electrochemical measurements effectively indicated that the largest value of initial discharge capacity and the highest cycling stability were exhibited by the 1.5 wt % graphene-burned LiNiO2 cathode material as compared to other graphene-burned samples. Interestingly, when employing graphite other than graphene as the carbon source, LiNiO2 particles with well defined octahedron structure were prepared by the same process, which is beneficial to the development of micro-devices. A novel concept, that burned graphene has a significant role in determining the morphology as well as the electrochemical properties of resulting samples, is presented in this work.