Safe and Flexible Chitosan Gel Electrolyte Based Zn-MnO2 Alkaline Batteries

Abstract

This work examines the use of naturally occurring chitosan with additives in a gel electrolyte and its efficient incorporation in safe, cost-effective, and rechargeable Zinc-EMD batteries. This study demonstrates (1) an energy and time efficient, scalable stage-wise preparation technique for achieving highly conducting (457mS/cm), flexible, electrochemically & thermally stable chitosan polymer electrolyte with PVA and KOH additives, along with their morphological and structural studies. This work also demonstrates (2) a robust and unique assembly technique employed to achieve good electrode/electrolyte interfacial contact when constructing a complete battery with the devised electrolyte to test its performance. (3) Employing a selective, limited potential window during galvanostatic charge-discharge tests; this work also achieved high specific capacity (310mAh/g) with good reversibility (170cycles) for Zn-EMD alkaline batteries using no cathode additives. The selective potential window approach helped utilize the available high capacity of EMD (γ-MnO2) through the two-step reduction process in addition to hindering the irreversible δ-MnO2 formations which usually hampers rechargeability in Zn-EMD alkaline batteries. The overall performance (70% capacity retention w.r.t initial, 97% and 110Wh/kg avg. energy density w.r.t cathode mass) recorded for the constructed battery with the devised gel electrolyte is comparable to the reported performances of Zn-EMD batteries with gel/liquid alkaline polymers in the literature. Culminating the electrochemical studies done on the assembled cell, it is possible to claim the successful rechargeability of our secondary batteries, which utilize novel alternative gel electrolyte fabrication methods that accommodate reversible zinc-reactions and novel cell assembly techniques.