Lithium Batteries – Lithium Secondary Batteries – Li-ion Battery | Positive Electrode: Lithium Iron Phosphates

We present a review of the structural, physical, and chemical properties of both the bulk and the surface layer of lithium iron phosphate (LiFePO4) (LFP) as a positive electrode for Li-ion batteries. Depending on the mode of preparation, different impurities can poison this material. Several impurities are identified, and a quantitative estimate of their concentration is deduced from the combination of X-ray diffraction analysis, Fourier transform infrared spectroscopy, Raman spectroscopy, and magnetic measurements. The surface layer also plays an important role in case the size of the particles is reduced to few tenths of nanometers, and it is characterized by the same means. These properties are correlated with the electrochemical performance of the positive electrode materials. An optimized preparation provides samples with carbon-coated particles free of any impurity phase, insuring structural stability and electrochemical performance that justify the use of this material as a cathode element in new generation of lithium secondary batteries operating at temperatures from 23 up to 60 °C. The electrochemical performances cycle life of commercial batteries 26,650 and ultrarare cell shows over 10,000 cycles at 100% DOD and 100% SOC at 23 °C and 7700 cycles at 60 °C.