(Invited) Zn-MnO2 Rechargeable Batteries Chemistry with Naturally Occurring Polymer Electrolyte Infused with Additives
Authors: Madan Deepa 
Published: May 2020

Zinc based chemistries have attracted attention and revived research efforts due to their low cost, phenomenal inherent safety, and reliable electrochemical performance. Amongst various Zn-chemistries, Zn-MnO2 has received wide attention due to its cost-effectiveness, safety, eco-friendliness, high output voltage, and high capacity. Traditionally this chemistry has been developed and commercialized as primary batteries (Energizer, Duracell, etc.). Varied research efforts have been put toward making this chemistry rechargeable, however the majority utilize aqueous electrolytes. Zn based rechargeable batteries are notoriously known for failure due to dendrite generation and propagation. It is relatively easy for the propagation of dendrites to occur in secondary batteries that contain liquid electrolytes unless additional measures (suppressants, separators, etc.) are adopted. In an effort to overcome the latter issues, and to boost the overall performance of our Zn-MnO2 batteries, incorporation of polymer electrolytes (offers mechanical resistance to dendrite growth) have been implemented. However, issues such as the polymer itself acting as an insulator, high interfacial resistance from the small solubility of the zinc salts, poor adhesion between electrolytes and electrodes are frequently observed. Additionally, the majority of polymers used in battery application are synthetic, which are widely known for their very slow degradation rates that may cause environmental concerns unless adequately disposed of. Most synthetic polymers used as the base constituent for preparation of electrolytes are known to induce crystallinity (rigidity) and thus affecting flexibility, ionic conductivity, and overall performance of the complete cell.

These overall limitations propelled our research to look and explore better alternatives. Our research focusses on exploring and preparing a zinc-manganese dioxide (Zn-MnO2) rechargeable battery using a novel and naturally occurring polysaccharide-based polymer gel film as the electrolyte. The novelty of the research lies in exploring and preparing polysaccharide-based electrolytes (flexible, biodegradable, safe, etc.) with various additives (for enhancing stability and performance) using non-conventional, low time, and low energy-consuming methods to attain an efficient optimized process. In this talk, I will discuss details of the polysaccharides explored, their performance with various salts incorporated in them. Effect on swellability of the polymer on ionic conductivities, reversibility and reactivity of Zinc in the system due to various molar concentrations (pH –variation) used in electrolyte preparation were extensively studied and will be discussed. Additionally, preliminary results for diffusion coefficient measurement, Zincate ions movements, and transference number performed to check performance efficiency and robustness of our gel electrolyte for cyclability will be presented. Our focus of research also extends towards generating an optimized cell construction technique to incorporate the prepared electrolyte in the cell to reduce the interfacial contact resistance. Also, few interesting non-conventional methods are being worked on currently to generate cathodes for this complete cell to achieve better performance. Finally, the overall performance of the constructed battery and performed ex-situ studies will be shown.