Improving the Rate Performance of Manganese Dioxide by Doping with Cu2+, Co2+ and Ni2+ ions

Metal-doped MnO2 has been successfully synthesized via chemical precipitation method. Interestingly, doping can increase not only ion conductivity but also intrinsic electron conductivity. By doping, the particle size of MnO2 decreases, relatively appropriate pore size distribution is obtained, and physically and chemically bound water content increases, all of which contribute to ion conductivity. Meanwhile, doping has induced some defects in MnO2 crystal, increasing the hole concentration and then intrinsic electron conductivity. As the result, metal-doped MnO2 displays better rate performance than the undoped. Especially, nickel-doped MnO2 exhibits the best rate behavior. Even at 8 A g(-1), nickel-doped MnO2 still has a specific capacitance as high as 234.0 F g(-1), larger than that of the un-doped obtained at 1 A g(-1) (only 173.6 F g(-1)). In conclusion, doping is a useful way for improving the rate performance of MnO2.