LiCoO2 single crystal particles were obtained by super critical water synthesis (SCWS) under optimized preparation conditions. The particle size of the LiCoO2 was less than 1 μm, which was much smaller than that of LiCoO2 prepared by a standard method. However, some unknown crystalline and amorphous phases coexisted with the well defined LiCoO2 single crystal particles. The discharge and charge characteristics of the LiCoO2 prepared by the SCWS were examined by some electrochemical methods. In the first cycle, an irreversible behavior was observed, and then the gradual decrease of the discharge capacity with discharge and charge cycle was also detected. The stable discharge capacity was estimated to be 80 mA h g−1 after the 100th cycle. This result may be due to the existence of amorphous phases and some structural defects.