Flexible, safe, cost-effective, and highly reversible Zinc-Manganese dioxide alkaline battery

Abstract

Wearable electronics are one of the most rapidly growing industries, due to their extended use in everyday applications resulting in an increased demand for portable energy storage devices. Amongst all types, Lithium-ion batteries (LIBs) have been occupying the majority of the market as energy storage devices for decades now. Despite immense success in commercialization, conventional LIBs suffer from issues of cost and safety. The expanding need for cheaper, and safer energy storage devices led explorations towards alternatives. After careful considerations, Zinc (Zn)-Manganese dioxide (MnO2) based alkaline system was chosen to be investigated in this work due to its low cost, inherent safety, and high theoretical energy density. However, challenges associated with making the aforementioned system rechargeable and highly performing still remains. The work in this study is directed towards enhancing the overall performance of the Zn-MnO2 alkaline battery in addition to making it suitable for flexible and wearable applications. A highly ionically conducting polymer electrolyte with excellent physical and electrochemical stability primarily comprising biopolymer chitosan is prepared by using a time and energy-efficient technique. Incorporation of this polymer electrolyte with Zn anode and MnO2 cathode enabled the successful preparation of a physically flexible cell. To obtain high cyclability and performance of the system; issues of inactive phase formations, low active material availability, pronounced shape changes at the anode surface, and zincate ion transfer towards cathode were overcome by enhancing the electrochemically active layers in the system. The assembled cell comprising the enhanced fabricated layers; (i.e. a Zinc/Stainless steel mesh composite anode, a hierarchical binder-free bismuth and copper additives based MnO2 cathode, and a chitosan-based polymer electrolyte with calcium hydroxide additive) indicated excellent rate capabilities (278.9 mAh/g @ 2 A/g & 172.8 mAh/g @ 5 A/g), high capacity utilization (78% of the theoretical 2-electron capacity on MnO2) and long cycling stabilities (70% retention over 1000 cycles). Moreover, initial bending tests conducted on the fabricated cell also showed not much performance deterioration when bent to different radii indicating good performance stability. The successful working of the fabricated cell was validated by lighting up an LED. The successful findings presented in this thesis can chart new pathways to the development of safe, flexible, cost-effective, and more environmentally responsible alternative energy storage sources for wearables.