In this work, nickel sulfides were prepared via a facile hydrothermal method. The particle size and phase composition were tuned by the reaction temperature. Phase-property relationship of NiS/Ni3S4 was established through combining characterization analysis with electrochemical tests. With the favorable particle size and composition, the NiS/Ni3S4 composite delivered preferable gravimetric capacity (194.4mAhg−1 at 2Ag−1, and 133.1mAhg−1 at 10Ag−1) and impressive circling stability (89.5mAhg−1 at 10Ag−1 after 5000 cycles).