LiNi0.8Co0.2O2 as the cathode material for a lithium ion battery was prepared by two different methods, sol–gel method and the solid-state reaction process. The samples were characterized and tested by means of XRD, SEM, particle size analysis, BET, and electrochemical methods. The results of XRD show that both the LiNi0.8Co0.2O2 samples prepared by two different methods are isostructural with α-NaFeO2 with a space group R-3m. The results of electrochemical studies show that the sample prepared by the solid-state reaction process is superior to that by the sol–gel method in electrochemical performance.