Electrochemical properties of C/SiO2 prepared from rice husks with LiPF6 and LiClO4 salts as electrolytes

Abstract

The C/SiO2 materials were prepared from rice husks used as anode electrodes for Lithium-ion batteries. The XRD results show that the diffraction peak had a large half-width and the material existed in an amorphous form. The first peak at the position 20o - 27o (2θ), was characterized by amorphous silica and amorphous carbon and the second peak at the position 43o - 44o was characterized by amorphous carbon. The C/SiO2 material contained 28.1 wt% SiO2. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images observed on the surface of the material showed many holes with sizes of 100 - 400 nm, the porosity was also formed inside the material structure with a size of a few nm. The C/SiO2 materials were investigated for their electrochemical properties in some types of the electrolyte of LiPF6 and LiClO4 salts and in some mixture the solvents used were EC:DMC (1:1), EC:DEC(1:1) and EC :DMC:DEC (1:1:1). The electrochemical results showed that the LiClO4 EC:DMC (1:1) electrolyte had the highest capacity, about 1,700 mAh.g-1 at 0.1 Ag-1 rate in the potential range of 0.01 - 2V. In addition, the material maintained a good capacity while increasing to higher current rates and the coulombic efficiency were more stable compared to other electrolytes. The results of the Electrochemical Impedance Spectroscopy (EIS) also showed that the impedance of this electrolyte system was about 20 Ω, therefor the processes of interlocking and releasing Li+ ions were more favorable than the other studied electrolyte.