Alkaline Zinc-Manganese Oxide Batteries

Alkaline zinc manganese oxide (Zn-Mn­O­₂) batteries are being developed as a cost-effective electrochemical energy storage technology for the energy grid. This battery chemistry is especially desirable because it utilizes low-cost materials that are environmentally friendly, water compatible, and (potentially) relatively energy dense. Recent work has shown that by overloading the cathode and anode with more MnO­₂ and Zn, respectively, several thousand cycles can be achieved, providing for an energy storage cost of less than $100 per kWh delivered. This concept of reduced depth of discharge (DOD) relies on the idea that reversibility can be maintained when the cathode is only partially discharged through the first electron reduction step to MnOOH. Similarly, less than ~10% Zn utilization allows for cycling with minimal deleterious Zn dendrite formation, passivation, and/or shape changes.

Continued improvement of the Zn-MnO­₂ system can be achieved by increasing materials utilization and cycle stability. Cell failure after long cycling periods typically results from the formation of irreversible phases of manganese oxides such as Mn₃O₄ and ZnMn₂O₄. The formation of these phases is substantially heightened at an increased DOD, leading to even earlier cell failure. Previous work suggests that inactive phases arise from soluble and reactive Mn(III) ions that are formed during discharge. These issues could be mitigated by stabilizing reduced manganese species with cathode or electrolyte additives, thereby allowing for higher DOD and increased accessible capacity. Herein, we report on the development of a laboratory scale battery fabrication method and a testing protocol to investigate the effects of reduced DOD cycling on the reversibility, cell impedance, and cycle life of alkaline Zn-MnO­₂ batteries.

Dr. Imre Gyuk, Energy Storage Program Manager, Office of Electricity Delivery and Energy Reliability and the SNL-LDRD Program are thanked for their financial support of this project.

Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.