Performance of Coconut Shell Activated Carbon in LiMn0.7Fe0.3PO4/CNT/C Composite for Lithium Ion Battery Cathode

Abstract

Synthesis and characterization of LiMn0.7Fe0.3PO4/CNT/C composite used as lithium ion battery cathode has been carried out. The active materials of LiMn0.7Fe0.3PO4 was synthesized via hydrothermal method from the precursors of LiOH, NH4H2PO4, FeSO4.7H2O and MnSO4.7H2O. The activated carbon was pyrolyzed from coconut shell whereas the carbon nanotube (CNT) was commercially available in the market. The composite was prepared using a ball-mill to mix the components homogeneously. Simultaneous thermal analysis STA was used to determine the formation temperature of LiMn0.7Fe0.3PO4 to which the sintering process was conducted at 700 °C. After sintering, the materials in powder forms were characterized using scanning electron microscope (SEM) to examine the morphology, whereas X-ray diffraction (XRD) was used to identify the phases formed. The performance of the composite as lithium ion battery cathode was characterized using electrochemical impedance spectroscopy (EIS) and battery analyzer. Secondary electron image from SEM showed that the samples have homogeneous particle distribution. Examination result from X-ray diffraction indicated that LiMn0.7Fe0.3PO4 phase has been successfully synthesized with small impurities from a secondary phase. Performance analysis showed that the presence of activated carbon and CNTs in LiMn0.7Fe0.3PO4 to form LiMn0.7Fe0.3PO4/CNTs/C gives significant improvement in the conductivity; however, some more improvement is still needed for the capacity.