A Modified Electrolyte for a Rechargeable Manganese-Zinc Alkaline Cell

There is a need for reliable, low-cost energy storage for electric vehicle applications. While advanced Li-ion batteries may possess sufficient power and energy density to be useful for electric vehicles, their high manufacturing and materials costs make them unsuitable outside of a relatively small market niche. Alkaline batteries, one of the most common modern forms of primary battery, are potentially ideal for electric vehicles. These cells depend on a reaction between zinc (Zn) and manganese dioxide (MnO2) to generate energy. This reaction gives alkaline batteries a relatively high energy density and a low cost per kilowatt-hour, but phase transformations occurring during deep discharge, particularly the formation of the electrochemically inactive ZnMn2O4 phase, prevent recharge. In a typical alkaline battery, useful rechargeability with minimal capacity losses can only be achieved if no more than 10% of the cathode’s capacity is used. [1]

We have developed a new, low-cost electrolyte which prevents the formation of electrochemically inactive phases, even during deep discharge. A capacity of 360 mAh/g on a cathode basis has been achieved cycling against zinc for more than 60 stable cycles, without evidence of ZnMn2O4 formation. We have also characterized the effects of this electrolyte as well as more conventional alkaline battery electrolytes using both conventional and in-operando synchrotron XRD techniques. We will discuss the impact of electrolyte formulation, charging and discharging protocols, and conductive additives on the performance of the system, and hypothesize on the mechanism by which this electrolyte prevents formation of electrochemically inactive phases.

References:

1. Shen, Yuwei, and Karl Kordesch. "The mechanism of capacity fade of rechargeable alkaline manganese dioxide zinc cells." Journal of power sources 87.1 (2000): 162-166