Defect effects on the physical and electrochemical properties of nanoscale LiFe_(0.92)PO4 and LiFe_(0.92)PO4/C/ graphene composites

摘要

Nanoscale LiFe_(0.92)PO4 and LiFe_(0.92)PO4/C/graphene composites including defects as performance-improved cathode materials for lithium-ion batteries were prepared by a carbothermal reduction method. The physical and electrochemical properties of samples were characterized by means of X-ray diffraction, inductively coupled plasma optical emission spectrometry, X-ray photoelectron spectroscopy, Mossbauer spectroscopy, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and electrochemical testing techniques. The results confirmed that defects existed within the nanoscaleLiFe_(0.92)PO4 lattice and had significant effects on improving the electrochemical properties of samples. The excellent graphene sheets covered on nanoparticles and formed a three-dimensional conductive network in nanoscale LiFe_(0.92)PO4/C/graphene composites. The composites exhibited a discharge capacity of 90 mA h g~(-1) at 10 C and capacity retention ratios of 98% after 100 cycles at various rates, implying outstanding high-rate capability and cycling stability.