Effect of different carbon precursors on properties of LiFePO₄/C

Abstract

The anoxic decomposition and influence of carbon precursors on the properties of LiFePO₄/C prepared by using Fe₂O₃ were investigated. X-ray powder diffractometry, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and carbon content and charge–discharge tests were applied to the characterization of the as-synthesized cathodes. Partial carbon is lost in the anaerobic decomposition of organic precursors and a high hydrogen content leads to a high residual carbon rate. Pyromellitic anhydride and citric acid participate in reactions before and in ball-milling. All the chosen carbon precursors are capable of producing LiFePO₄ with high degree of crystallinity and purity. The carbon derived from α-D-glucose, pyromellitic anhydride, soluble starch, citric acid and polyacrylamide has a loose and porous texture in LiFePO₄/C which forms conduction on and between LiFePO₄ particles. LiFePO₄/C prepared by using α-D-glucose, pyromellitic anhydride, citric acid and sucrose exhibits appreciable electrochemical performance. Graphite alone is able to enhance the electrochemical performance of LiFePO₄ to a limited extent but incapable of preparing practical cathode.

Keywords

LiFePO₄ / lithium ion cell / carbon precursor / decomposition / charge–discharge test / graphite

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