M1/3Ni1/3Mn2/3O2 (M = Mg or Zn) is sucessfully synthesize from Na2/3Ni1/3Mn2/3O2 via a electrochemical conversion method. The structure and morphology of the as-prepared material are systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and X-ray photoelectron spectroscopy (XPS), respectively. The nano-sized morphology of M1/3Ni1/3Mn2/3O2 is beneficial for the reduction of diffusion length and transfer acceleration of cations from the surface into the bulk interiors. XRD patterns reveal that crystal structure is maintained after the reversible Mg2+ or Zn2+ intercalation/deintercalation. Its performance for Mg2+ and Zn2+ intercalation/deintercalation in aquesous electrolytes is evaluated by cyclic voltammetry, galvanostatic cycling and electrochemical impedance spectroscopy. Mg1/3Ni1/3Mn2/3O2 exhibits an initial capacity of 170.5 mAh g(-1) in 1 mol L-1 Mg (NO3)(2), Zn1/3Ni1/3Mn2/3O2 displays capacity of 113.7 mAh g(-1) in 1 mol L-1 ZnSO4. Mg1/3Ni1/3Mn2/3O2 shows a good cycling performance and maintains 52.7 mAh g(-1) at 1.0C after 200 cycles in 1.0 mol L-1 MgSO4. (C) 2015 Elsevier Ltd. All rights reserved.