Preparation of carbon coated LiMnPO4 powders by a combination of spray pyrolysis with dry ball-milling followed by heat treatment

摘要

Nanostructured LiMnPO4 particles could be successfully synthesized by an ultrasonic spray pyrolysis method from the precursor solution; LiNO3, Mn(NO3)2·6H2O and H3PO4 were stoichiometrically dissolved into distilled water. The X-ray diffraction analysis showed that the as-prepared powders which had the desired olivine structure without any impurity phase could be obtained in the reactor temperatures ranging from 500 to 800 °C. Carbon coated LiMnPO4 could be prepared from the as-prepared powders by a dry ball-milling followed by heat treatment for 4 h in a N2 + 3% H2 atmosphere. Transmission Electron Microscopy observation confirmed that a carbon layer was formed on the surface of LiMnPO4 particles, which aimed to enhance the electronic conductivity of the material as well as inhibit the agglomeration during annealing. The carbon coated LiMnPO4 was used as cathode active materials for lithium-ion batteries, and electrochemical performance was investigated using the Li|l M LiClO4 in EC:DEC = 1:1 |LiM-nPO4 cells at room temperature and 55 °C. At a charge/discharge rate of 0.05 C, the cell exhibited first discharge capacities of 70 mAh g~(-1) at room temperature and 140 mAh g~(-1) at 55 °C. Moreover, it showed excellent cycleability even at elevated temperature and a high charge/discharge rate of 2 C.