Magnetic and spectroscopic characterization of C-LiFePO$_{4}$ nanoparticles for cathode material for Li ion batteries

We synthesized pure and carbon coated LiFePO$_{4}$ nanoparticles (size $\sim $25 nm) by sol-gel technique. All the samples were~characterized~by X-ray diffraction, XPS, SQUID, and Mossbauer spectroscopy measurements. The elemental chemical states for Li 1s, Fe 2p, P 2p, O 1s and C 1s were examined by using XPS for LiFePO$_{4}$ and compared with those of C-LiFePO$_{4}$ material. Temperature dependent magnetic measurements suggest an antiferromagnetic transition $\sim $50 K in both LiFePO$_{4}$ and C-LiFePO$_{4}$ samples. The role of various phases, such as LiFePO$_{4}$ Fe$_{x}$P, $\alpha $-Fe and Fe$_{3}$O$_{4}$ identified by Fe$^{57}$ Mossbauer spectroscopy, will be discussed in relationship with the electrochemical properties of the cathode materials.