Improving Performance of LiFePO4 by addition of Carbon Nano Tube for Lithium Ion Battery

Abstract

LiFePO4 (LFP) cathode material has been synthesized with hydrothermal method. The reaction was done by reacting a mixture of FeSO4.7H2O, H3PO4, LiOH and CNT. In order to improve performance of LFP, the carbon nano tube (CNT) was added with the variation of 5, 10 and 15 mmol, before hydrothermal process. The material was stirred using a magnetic stirrer for 30 minutes, and then autoclave was heated at 180°C for 6 hours then sintered at 700°C for 6 hours. The results were characterized by X-ray diffraction (XRD), and Scanning Electron Microscope (SEM), and Impedance Spectroscopy (EIS). The X-ray data shows that the crystal structure of synthesized LiFePO4 has a group of Pmn with a space (olivine structure) which is in agreement with the LFP standard material. The addition of CNT does not change the crystal structure. This shows in SEM images that the crystallite size of LiFePO4 particles does not have much effect on the composite. The battery cell performance was measured by Impedance Spectroscopy and charge/discharge Battery Analyzer BST-8. The EIS data, showed the decreasing of battery impedance total from LiFePO4 material without CNT to addition of 5, 10 and 15 mmol CNT namely 214; 128.1; 88.6 and 70.1 Ω, and the specific capacity 0.1C are 38.78; 51.53; 106.84; 92.79 mAh/g, respectively. It is shown that the maximum specific capacity was obtained for LFP composite with the addition of 10mmol CNT. It can be concluded that the addition of CNT increases the conductivity and specific capacity, thus improving performance of lithium ion battery.