High power performance of nano-LiFePO4/C cathode material synthesized via lauric acid-assisted solid-state reaction

A nano-LiFePO4/C composite has been directly synthesized from micrometer-sized Li2CO3, NH4H2PO4, and FeC2O4.2H(2)O by the lauric acid-assisted solid-state reaction method. The SEM and TEM observations demonstrate that the synthesized nano-LiFePO4/C composite has well-dispersed particles with a size of about 100-200 nm and an in situ carbon layer with thickness of about 2 nm. The prepared nano-LiFePO4/C composite has superior rate capability, delivering a discharge capacity of 141.2 mAh g(-1) at 5 degrees C. 130.9 mAh g(-1) at 10 degrees C, 121.7 mAh g(-1) at 20 degrees C, and 112.4 mAh g(-1) at 30 degrees C. At 20 degrees C, this cathode material still exhibits good rate capability with a discharge capacity of 91.9 mAh g(-1) at 1 degrees C. The nanoLiFePO(4)/C composite also shows excellent cycling ability with good capacity retention, up to 100 cycles at a high current density of 30 degrees C. Furthermore, the effect of lauric acid in the preparation of nanoLiFePO(4)/C composite was investigated by comparing it with that of citric acid. The SEM images reveal that the morphology of the LiFePO4/C composite transformed from the porous structure to fine particles as the molar ratio of lauric acid/citric acid increased. (C) 2011 Elsevier Ltd. All rights reserved.