Electrochemical Performance of Carbon Coated LiMnPO4 as Lithium-Ion Battery Cathodes

Abstract

Lithium ion batteries with high energy and power density are important for portable electronic devices, transportation and energy storage. In recent times, great interest has been focused toward the lithium metal phosphates as potential cathode materials for lithium-ion batteries due to their nontoxic, cost effectiveness and better chemical and thermal stability. Among the lithium metal phosphates, LiFePO4 has been successfully optimized for high-power applications. On the other hand, LiMnPO4 cathode materials possess higher operating voltage, but, their rate capability is significantly lower. The three-dimensional framework of an olivine is stabilized by the strong covalent bonds between oxygen ions and the P5+ resulting in PO4 3− tetrahedral polyanions. In general, LiMnPO4 possess a low intrinsic electronic and ionic conductivity, and for this reason a reduced discharge rate capability was attained. The electrochemical performance is particularly lower at high current densities, this was suggested to the slow lithium diffusion kinetics within the grains and the low intrinsic electronic conductivity. Therefore, ultrafine nanostructures coated with conductivity carbon can prevail over these problems. In the present study, a comparison was intended to draw by carbon coating LiMnPO4 nanostructures via in-situ diol process and carbon coating the diol process synthesized LiMnPO4 by mechanical milling. The synthesized LiMnPO4 nanostructures were characterized by an X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and studied the electrochemical performance.