Reversible extraction and insertion of lithium from and into olivine LiCoPO4 at 4.8 V vs. lithium have shown that this material is a good candidate for a high-voltage lithium-ion battery. Electrochemical extraction was limited to 0.42 lithium per formula unit, with a charge capacity of 86 mAh/g and a discharge capacity of 70 mAh/g. In this case, the material retains its structural integrity with a slight contraction of the unit cell upon cycling. The crystallinity of the electrode during charge and discharge processes was not affected, as deduced from the sharpness of the X-ray diffraction peaks of the cycled cathode material.