Carbon coated LiFePO4 cathode material obtained by freeze-drying method

Abstract

One of the most perspective cathode materials for the application in the Li-ion batteries is LiFePO4. It has high theoretical specific capacity, good cycle life and technically suitable flat voltage of 3.45 V versus Li. However, its main disadvantages are low electronic and ionic conductivities which can be overcome by particle size minimization and/or carbon coating. Here is presented the freeze-drying method for the preparation of carbon coated LiFePO4 particles. It involves freezing of a precursor solution, vacuum drying and final calcination of as-dried powder under slightly reductive atmosphere. The main advantage of this preparation process is mixing at the atomic level which provides more homogeneous precursor. Water solutions containing Li+,PO4 3- and Fe2+ ions with the addition of various organic compounds as a carbon source were used as the precursor solutions. The as-prepared powders were fully characterized by means of X-ray powder diffraction, scanning electron microscopy, particle size analyzer and galvanostatic cycling.