(71b) The Renaissance of Zinc|Manganese Dioxide Batteries: Revolutionizing the Landscape of Energy Storage Enabled Through Material Science Breakthroughs

The current landscape of energy storage batteries is dominated by lithium (Li) – ion batteries. However, these batteries are expensive, flammable and contain toxic elements that make it unsustainable and dangerous battery. Cobalt which is one of Li-ion batteries main ingredients is limited in supply and also mined with less regulations, which has affected the health of the miners in Africa.¹ There is a clear need for a safe, non-toxic, non-flammable and energy dense battery that can be a better alternative to Li-ion and lead acid batteries in the areas of grid energy storage, consumer electronics, electric bikes and electric vehicle applications. This talk will concentrate and present evidence of a safe, non-toxic and non-flammable battery which contains zinc (Zn) and manganese dioxide (MnO₂) as the active materials. These are commonly used in household appliances as primary (non-rechargeable) batteries. We focus on fundamentally altering the crystal structure and electrode framework through materials science of the cathode and anode materials to access the theoretical capacity of MnO₂ (617mAh/g) and Zn(820mAh/g) for >3000 times.² The MnO₂ cathode in traditional alkaline batteries is electrochemically synthesized and contain tunnelled structures which breakdown due to volume expansion during charge and discharge. These structures are also prone to Zn poisoning as dissolved Zn ions create a spinel structure with MnO₂ that is electrochemically inactive. We synthesized a MnO₂ cathode that contained layered structures of the birnessite-type (d-MnO₂) instead of the tunnel-type. These structures were intercalated with copper and bismuth ions that substantially reduced the charge transfer resistance and allowed for a complete regenerable cathode structure that accessed its theoretical capacity >6000 times.³ Similarly, Zn anodes suffer from passivation and loss of active material because of zinc oxide formation on its surface and eventual dissolution in alkaline electrolyte. We fabricated a carbon nested Zn anode framework to address this issue, where the carbon structure prevented passivation of the Zn surface and the conductive framework allowed for rapid dissolution and deposition during charge-discharge reactions that prevented loss of active materials.⁴ Finally, corrosive liquid alkaline electrolytes affect Zn dissolution and the robustness of the cellulose separator during long-term operation. Also, for batteries to be classified as “Non-Hazardous” they need to be non-spillable according to the Department of Transportation (DOT). Highly ionically conductive hydrogels were synthesized, that address these issues, where they are crosslinked to increase the rigidity and non-spillable properties that meet DOT regulations. The crosslinked network of the hydrogels also reduces zinc ion diffusion which considerably reduces the poisoning of the cathode. The properties of these hydrogels were also altered, where an acid and alkaline gel can be paired which do not neutralize and this results in increasing the voltage of a traditional Zn|MnO₂ battery from 1.5V to 2.8V, which is tremendously important for increasing the energy density.⁵ These material advancements have allowed us to commercialize advanced Zn|MnO₂ batteries for grid storage and now test it for electric vehicular applications.

Acknowledgements

This work was supported by the U.S. Department of Energy, Office of Electricity, Energy Storage program and the Advanced Manufacturing Initiative through a contract from Sandia National Laboratories. The author would like to thank Dr. Imre Gyuk, Manager of the DOE Energy Storage program for funding this work. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy National Nuclear Security Administration under contract DE-NA-0003525.

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