Co3O4 with three different crystal plane structures - cubes bounded by {001} planes, truncated octahedra enclosed by {111} and {001} planes, and octahedra with exposed {111} planes - is synthesized using a very simple one-step hydrothermal method. The three kinds of Co3O4 exhibit significantly different electrochemical performances and the effect of different exposed crystal planes on the electrochemical performance of Co3O4 is comprehensively studied.