A facile and novel precursor conversion method is successfully developed to grow Ni-Co hydroxides with a phase structure. The method is robust and versatile enough to be employed to prepare a phase Ni-Co hydroxides with similar interconnected flower-like nanostructures even at different Ni and Co contents. When used as the electroactive materials for supercapacitors, the bimetallic Ni-Co hydroxides deliver much higher specific capacitance with improved rate capability and cycling stability than monometallic Ni hydroxide. Especially, the Ni0.5Co0.5 hydroxide exhibits the highest specific capacitance of 1600 F g(-1) at a current density of 1 Ag-1. Meanwhile, the mechanism for better cycling stability of the bimetallic Ni-Co hydroxides is studied by FT-IR measurement. It is found that the introduction of Co ions contributes to the stable existence of ethylene glycol molecules in the interlayer space of the a phase Ni-Co hydroxides, resulting in superior cycling stability of the bimetallic Ni-Co hydroxides. (C) 2015 Elsevier Ltd. All rights reserved.