LiFePO4/Carbon/Reduced Graphene Oxide Nanostructured Composite as a High Capacity and Fast Rate Cathode Material for Rechargeable Lithium Ion Battery

Abstract

In this study, LiFePO4-carbon (LFP-C) and LFP-C/reduced graphene oxide (rGO) nanocomposites were prepared by ultrasonic spray pyrolysis technique in different calcination conditions to be used as the cathode-active materials for lithium ion battery (LIB). The structure, morphology and composition of the obtained materials were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscopy (HR-TEM) and energy-dispersive X-ray spectroscopy (EDX). The XRD results reveal that the olivine pure phase was obtained after calcination of the LFP-C. The SEM images of the prepared materials exhibit the spherical morphology with nanometer size and also change in the morphology by applying the calcination step. The electrochemical performances of cathode-active materials were investigated by charge–discharge test, electrochemical impedance spectroscopy and cyclic voltammetry. The obtained results for LFP-C show that the electrochemical performance was improved by adding carbon precursor and calcining step; in the optimum calcination conditions; 700 °C for 3 h, the LFP-C shows good results in terms of electrochemical performance in comparison with LFP alone. The LFP-C/rGO nanocomposite exhibits the best electrochemical performance however: highest rechargeable capacity and cycle stability; discharge capacity (168 mAh/g at 0.1 C and 123.5 mAh/g at 10 C) and capacity retention of 100% after 50 cycles with maximum reversibility and lithium ion (Li+) diffusion coefficient. Schematic representation of preparation of the cathode-active materials.