Assembled manganese and its nanostructured manganese dioxide rich electrodes for a new primary battery

Abstract: In this work, manganese metal and its nanostructured dioxide (MnO2) were applied as electrodes for the development of a new Mn/MnO2 battery. The MnO2 was deposited onto platinum substrate using electrodeposition technique and collected as powder cathode in the new battery. The influences of temperature and precursor pH on the MnO2 film properties were investigated. Scanning electron microscopy, X-ray diffraction (XRD), energy dispersive X-ray analysis and transmission electron microscopy (TEM) were used to characterize the MnO2 deposit. The XRD and TEM demonstrate that the MnO2 was deposited in its γ-MnO2 phase with a particle size less than15 nanometer. In addition, the pH solution plays a key role in the electrochemical performance of the MnO2 as a cathode. Indeed, the γ-MnO2 deposited at pH=2 provides a high discharge performance in KOH and NH4Cl aqueous electrolytes. This led to a new Mn/MnO2 cell with better performance compared to the classical Zn/MnO2 cell in terms of discharge in NH4Cl electrolyte. During the discharge process, co-insertion of Mn2+ and H+ promotes the transformation of MnO2 into MnxMnO4, MnOOH, and Mn2O3. In addition, the Mn/MnO2 cells exhibits a high output voltage > 2 V in NH4Cl. It reach a high voltage at around 1.89 V after 3 h of continuous discharge. The cells can achieve a discharge capacity of 1000 mAh.g-1 at a current density of 330 mA.g-1 with the highest specific energy of 1890 mWh.g-1. Moreover, Mn/MnO2 cells are more stable in NH4Cl electrolyte which exhibits a voltage drop of 6% after 3 h of continuous discharge. Such results demonstrate that the assembled Mn/MnO2 battery can occupy an important place in the energy storage field as a low cost and high performance device.