Nano-Crystalline LiFePO₄

Abstract

In the previous chapter it was shown that amorphous FePO₄ was obtained by following a solution-based approach (Prosini et al., J. Electrochem. Soc. 149:A886–A890, 2002). Crystallization of the amorphous material at 650°C leads to the formation of hexagonal FePO₄. The phase resulted was not isostructural with FePO₄ (heterosite) formed on lithium extraction from LiFePO₄ (triphylite) with ordered olivine-type structure. The amorphous FePO₄ was chemically lithiated using lithium iodide as the reducing agent. In such a way it was possible to obtain a new phase, amorphous LiFePO₄ , which was not previously accessible. In this chapter nano-crystalline LiFePO₄ with ordered olivine-type structure was obtained by heating the amorphous nano-sized LiFePO₄ precursor. The so-obtained material was characterized by chemical analysis, TG, DTA, X-ray powder diffraction, SEM, and BET. The material was tested as a cathode for lithium-ion batteries (Prosini, J. Electrochem. Soc. 149:A886–A890, 2002). Nano-crystalline LiFePO₄ showed very good electrochemical performance delivering the full theoretical capacity (170 Ah kg^?1) when cycled at 17 A kg^?1 at room temperature. A capacity fade of about 0.25 % per cycle affected the material upon cycling.