Challenges in synthesizing carbon-coated LiFePO_4 nanoparticles from hydrous FePO_4 and their electrochemical properties

摘要

Carbon-coated LiFePO_4 nanoparticles are obtained from a polymer-coated hydrous FePO_4 which is synthesized via the in situ polymerization of aniline. The difficulty in synthesizing a pure LiFePO_4 phase comes from achieving the exact stoichiometry between the added Li source and hydrous polyaniline-coated FePO_4. It is important to consider the amount of residual H_2O and polyaniline in FePO_4 to achieve the exact stoichiometry of Li vs. Fe. The phase impurities induced by inappropriate amount of Li severely deteriorate the electrochemical performance of C-coated LiFePO_4. On the other hand, the carbon-encapsulated LiFePO_4 nanoparticles with the exact amount of Li show a capacity of ~145 mAh g~(-1) at 5 C, and exhibit a capacity of 170 mAh g~(-1) for 250 cycles at 0.1 C which is nearly theoretical value.