Impact of cathode additives on the cycling performance of rechargeable alkaline manganese dioxide–zinc batteries for energy storage applications

Abstract

The impact of chemical additives [e.g., BaSO4, Sr(OH)2·8H2O, Ca(OH)2, and Bi2O3] on the cycling performance of rechargeable alkaline electrolytic manganese dioxide/Zn batteries has been studied. The additives were used in the cathode electrodes consisting of 5 wt% additive, γ-MnO2 (electrolytic manganese dioxide—EMD—80 wt%) and KS44 graphite (15 wt%) in prismatic-type electrode geometries. Powder X-ray diffraction analysis showed the formation of alkaline earth metal carbonates (BaCO3, SrCO3) when the electrodes come into contact with the highly alkaline (pH 15, 9 M KOH) electrolyte. The presence of dissolved carbonate in the electrolyte leads to a double replacement precipitation reaction leading to the formation of these carbonate species. These additives help with the cycle life of the electrolytic manganese dioxide cathode material. The overall energy efficiency of the cells is about 75%. Rate capability studies and equilibrium potential measurements by galvanostatic intermittent titration technique analysis indicate that ohmic polarization plays a significant role in the energy loss and should be improved for high power applications. Rechargeable alkaline batteries with electrolytic manganese dioxide/Zn chemistry provide a low-cost and an environmentally friendly solution for storage of energy. Improvement of this technology would be an important contribution in the area of energy storage applications. The impact of a number of chemical additives (e.g., BaSO4, Sr(OH)2·8H2O, Ca(OH)2 and Bi2O3) on the cycling performance of rechargeable alkaline EMD/Zn batteries has been studied. The additives were used in the cathode electrodes consisting of 5 wt% additive, γ-MnO2 (electrolytic manganese dioxide—EMD—80 wt%) and KS44 graphite (15 wt%) in prismatic-type electrode geometries. Powder X-ray diffraction analysis showed the formation of alkaline earth metal carbonates (BaCO3, SrCO3) when the electrodes come into contact with the highly alkaline (pH 15, 9 M KOH) electrolyte. The presence of dissolved carbonate in the electrolyte leads to a double replacement precipitation reaction leading to the formation of these carbonate species. These additives help with the cycle life of the EMD cathode material. The overall energy efficiency of the cells is about 75%. Rate capability studies and equilibrium potential measurements by galvanostatic intermittent titration technique analysis indicate that ohmic polarization plays a significant role in the energy loss and should be improved for high power applications. Rechargeable alkaline batteries with EMD/Zn chemistry provide a low-cost and an environmentally friendly solution for storage of energy. Improvement of this technology would be an important contribution in the area of energy storage applications.