Inhibition of phase transition from δ-MnO 2 to α-MnO 2 by Mo-doping and the application of Mo-doped MnO 2 in aqueous zinc-ion batteries.

MnO 2 is an oxide with many crystalline phases and is often used as a cathode material for aqueous zinc-ion batteries. However, its poor electrical conductivity and structural instability limit its further application. In the present work, Mo-doped MnO 2 microflowers are successfully prepared by a facile hydrothermal method. Interestingly, it is found that the doping of Mo inhibits the phase transition from δ-MnO 2 to α-MnO 2 , which may be related to the low crystallinity of Mo doped MnO 2 . Compared with undoped MnO 2 , Mo-doped MnO 2 maintains two-dimensional morphology with a large specific surface area and mesoporous structure. In addition, the electronic conductivity and reversibility of Zn 2+ insertion/extraction are improved in Mo doped MnO 2 . Therefore, Mo-doped MnO 2 exhibits high reversible capacity and long cycling stability. For example, a high reversible capacity of 72.6 mA h g -1 can be achieved at a current density of 2000 mA g -1 after 2500 cycles.