Effect of Various Organic Precursors on the Performance of LiFePO[sub 4]∕C Composite Cathode by Coprecipitation Method

The goal of this research was to study the effect of organic precursors with functionalized aromatic anhydrides or aromatic diketones on the performance of the Li Fe P O 4 ∕ C composite. A coprecipitation method was applied to prepare a series of Li Fe P O 4 ∕ C materials by calcinating amorphous Li Fe P O 4 with 5 wt % organic precursors at 750 ° C . The materials were characterized by X-ray diffraction, scanning electron microscopy, particle size analysis, thermal analysis, Brunauer-Emmett-Teller specific surface area and electrochemical methods. The obtained Li Fe P O 4 ∕ C composites showed a well-ordered olivine-type Li Fe P O 4 structure with a minor Fe 2 P impurity. The occurrence of the Fe 2 P phase can be attributed to the relatively high temperature of 750 ° C . The Li Fe P O 4 ∕ C composites produced by pyrolysis of an aromatic diketone with a longer alkoxy branch exhibited a better capacity compared to other types of organic compounds. The longer alkoxy aromatic diketone showed a better performance because its decomposition temperature was close to the temperature of the Li Fe P O 4 phase transformation resulting in a fine particle size and uniform carbon distribution on the composite surface. The performance of different organic precursors showed a strong relationship with its decomposition temperature, but was not in correlation with its weight loss. According to Raman spectral analysis, longer alkoxy aromatic diketones have a larger ( D + G ) ∕ P O 4 peak ratio indicating higher uniform and carbon content coating on Li Fe P O 4 ∕ C particles.