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

Abstract Lithium iron phosphate/carbon (LiFePO 4 /C) microspheres with high rate and cycling performance are synthesized from iron phosphate/polyacrylic acid (FePO 4 /PAA) nanoparticles. Iron(III) acrylate is used as a precursor for both the iron and carbon sources. FePO 4 nanoparticles are first produced by a coprecipitation reaction. The byproduct, acrylic acid ions, is polymerized in situ to form a uniform PAA layer on the surface of the FePO 4 nanoparticles. The as‐prepared LiFePO 4 /C microspheres are composed of primary nanoparticles with sizes of 40–50 nm. 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 LiFePO 4 /C microspheres display both high electronic and ionic conductivities, which contribute to their high rate performance (162.9 mAh g −1 at 0.1C and 126.1 mAh g −1 at 5C) and excellent cycling stability (97.1 % of capacity retention after 500 cycles at 5C/5C).