Synthesis of Lithium Iron Phosphate/Carbon Microspheres by Using Polyacrylic Acid Coated Iron Phosphate Nanoparticles Derived from Iron(III) Acrylate

摘要

Lithium iron phosphate/carbon (LiFePO4/C) microspheres with high rate and cycling performance are synthesized from iron phosphate/polyacrylic acid (FePO4/PAA) nanoparticles. Iron(III) acrylate is used as a precursor for both the iron and carbon sources. FePO4 nanoparticles are first produced by a coprecipitation reaction. The byproduct, acrylic acid ions, is polymerized insitu to form a uniform PAA layer on the surface of the FePO4 nanoparticles. The as-prepared LiFePO4/C microspheres are composed of primary nanoparticles with sizes of 40-50nm. The nanoparticles are fully coated with a thin, uniform carbon layer derived from the decomposition of the PAA layer. The uniform carbon-coating layer cooperates with interstitial and boundary carbon derived from sucrose successfully to construct an excellent interconnecting conductive network in the microspheres. As a result of the unique structure, the as-prepared LiFePO4/C microspheres display both high electronic and ionic conductivities, which contribute to their high rate performance (162.9mAhg(-1) at 0.1C and 126.1mAhg(-1) at 5C) and excellent cycling stability (97.1% of capacity retention after 500cycles at 5C/5C).