Novel Lithium Iron Pyrophosphate(LiFe_(1.5)P2O7)as a Positive Electrode for Li-Ion Batteries

摘要

Lithium iron pyrophosphate(LiFe_(1.5)P2O7)has been synthesized by a wet-chemical method for application in lithium-ion batteries.Structural analysis using X-ray diffraction and high-resolution electron microscopy indicate that LiFe_(1.5)P2O7 synthesized at 500 °C,using metal acetates,is crystallized in the monoclinic structure with lattice parameters a = 0.698 76 nm,b = 0.812 36 nm,c = 0.964 22 nm,and beta=111.83°(P2_1/c space group).Electrochemical characterization of LiFe_(1.5)P2O7 in lithium cells indicates a capacity of 95 mA·h/g obtained in the voltage range 2.5-4.2 V.The resulting incremental capacity indicates a stable structure for the first cycle with the redox peaks at 3.33 and 3.22 V versus Li~0/Li~+.The capacity of LiFe_(1.5)P2O7 decreased with cycling number at the rate of 0.22 per cycle while the capacity falls off rapidly in the case of material prepared at higher temperatures.