δ-MnO 2 with the doping of Ni and Bi was prepared through a simple chemical precipitation/oxidation method. Its structure was confirmed by the X-ray diffraction tests. The results of cyclic voltammetry and galvanostatic charge–discharge tests showed that both the doping of Bi and Ni benefited the electrochemical activity of the MnO 2 electrode. Compared to the un-doped electrode, the Bi-doped one showed larger discharge capacity and the Ni-doped one showed higher discharge potential and better cycleability. With the co-doping of 5wt% Bi and 10wt% Ni, the discharge capacity of the MnO 2 electrode reached 252mAhg −1 at a 0.2C rate and 116mAhg −1 at a 1C rate, respectively. Its capacity remained in 105mAhg −1 after 50 cycles at a 1C rate, but the capacity of a commercial electrolytic MnO 2 electrode was only 37mAhg −1 .