The electrochemical performance of high-voltage LiCoPO4 electrode synthesized by high-temperature solid-state reaction was investigated. It is found that the existence of the carbon and Co2P decreases the discharge capacity; the LiCoPO4 with pure olivine phase has a maximum discharge capacity and it can reach 135 mAh/g. The cyclic voltammetric measurements have shown that the impurity of carbon and Co2P can change the Li-deintercalation reaction mechanism. There are two oxidation peaks when the impurity content is relatively low; however, there is only on oxidation peak with the larger amount of impurities in the cyclic voltammetry. The interface capacitance between the LiCoPO4 electrode and the electrolyte is about 16.9 mF/cm2 and the apparent diffusion coefficient of the lithium ion in the solid phase is (2.0~3.4)′10-9 m2/s, based on the impedance measurements.