Novel lithium iron pyrophosphate (LiFe1.5P2O7) as a positive electrode for li-ion batteries

Lithium iron pyrophosphate (LiFe1.5P2O7) 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 LiFe1.5P2O7 synthesized at 500 degrees 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 degrees (P2(1)/c space group). Electrochemical characterization of LiFe1.5P2O7 in lithium cells indicates a capacity of 95 mA center dot 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 LiFe1.5P2O7 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.