Amorphous nickel hydroxide powder codoped with Fe3+ and PO43- was synthesized by micro-emulsion precipitation method combined with rapid freezing technique. The microstructures of the prepared samples were characterized by XRD, SEM, EDS, and Raman spectra. The electrochemical performance of the prepared samples was analyzed by cyclic voltammetry, electrochemical impedance spectroscopy, and charge-discharge tests. The results showed that this amorphous nickel hydroxide codoped with Fe3+ and PO43- resulted in more structural defects within the nickel hydroxide. The Fe3+ and PO43- codoping could increase the specific discharge capacity and improve the electrochemical reversibility of the amorphous nickel hydroxide.