Abstract: Oliver phase LiFePO₄ powder was successfully synthesized by solid-state reaction process and spherical processing.SEM observation confirmed that the resulatant product consisted of many spherical aggregates with diameters of 10—15 μm.The cyclic voltammetric profile of battery with cathode of LiFePO₄ shows the single and reversible mechanism for lithium ion extraction/insertion in cathode.The a.c.impedance spectra of the battery at different temperatures reveal that the electrochemical impedance of battery decreases with increasing ambient temperature.At the current density of 17 mA/cm²,the batteries show a flat working voltage,little electrode polarity effect and nearly theoretical capacity.Below the current density of 170 mA/cm²,the high capacity is kept.With the current density increasing further above 170 mA/cm²,the capacity decreases fast and the electrode polarity effect is observed obviously.After cycling at a high current density,the batteries still show the high capacity at the low current density.

Key words: Lithium ion batteries, LiFePO₄, Spherical processing, Electrochemical properties