Alkaline-Earth Oxide Modified MnO2 Cathode: Enhanced Performance in an Aqueous Rechargeable Battery

The current work is reported on employing alkaline-earth oxide additives—i.e., barium oxide (BaO), calcium oxide (CaO), or magnesium oxide (MgO)—to the manganese dioxide (MnO2) cathode in an environmentally safe aqueous rechargeable battery. The influence of these additives on the electrochemical behavior of the MnO2 cathode in a Zn-MnO2 battery using lithium hydroxide (LiOH) as an electrolyte is investigated. These additives enhanced the discharge performance of the Zn-MnO2 battery and its rechargeability. Herein, the MnO2 was physically mixed with at least one of the alkaline-earth oxides (such as BaO, CaO, or MgO) in different proportions of 1, 2, and 5 wt % during the electrode preparation. The incorporation of BaO or MgO additives into MnO2 was found to result in significantly higher discharge capacity and longer cycle life, compared with the battery using CaO additive or additive-free MnO2. The role of these additives in the MnO2 cathode is found not to suppress the formation of nonrechargeable products, but rather to reduce the access of Zn ions to the MnO2; without these additives, a ZnO·Mn2O3 product may form at the cathode.