Mn₃O₄ nanowires with diameter of ∼15 nm and a length of up to several micrometres have been hydrothermally synthesized at 200 °C for 15 h without any surfactants. It was investigated that during the formation process of Mn₃O₄ nanowires the length of the nanowires increased while the diameter did not obviously change. The coercivity of the Mn₃O₄ nanowires is up to 5600 Oe at 5 K. As these Mn₃O₄ nanowires were treated with LiOH by solid state reaction at 750 °C for 6 h, interconnected LiMn₂O₄ polyhedrons were obtained. The achieved discharge capacity of the LiMn₂O₄ polyhedrons was 115 mAh g⁻¹ and they retained 98.3% of this capacity after 60 cycles at 0.1 C.