Gel Polymer Electrolytes for Zinc-Air Batteries Operating at Low Temperatures

Abstract

Zinc-air batteries (ZABs) have gained much attention from researchers in recent years, partly due to their high theoretical energy density as well as improved safety and the abundance of zinc relative to lithium in lithium-ion batteries (LIBs). Gel polymer electrolytes (GPEs) in ZABs can act as a separator and, therefore, can reduce the effect of dendrite formation at the zinc electrode. The temperature of many areas in Canada can be extremely low (less than -30oC) in the winter and many batteries do not work well at such low temperatures, mainly due to reduced rates for the electrochemical reactions in the battery. The objective of this work is to develop a GPE for ZABs using in-situ fabrication. The use of in-situ gelation can reduce the contact resistance between the GPE and the electrodes, thereby improving ion transport between the electrolyte and electrodes. The GPEs in this work are fabricated using poly(acrylic acid), crosslinked with KOH and a final immersion step in a mixture of additives. The additives are utilized to improve the performance of ZABs at low temperatures. As a redox mediator, KI can change the traditional oxygen evolution reaction in ZABs to a more thermodynamically favored reaction. ZnO is used to improve the cyclability of ZABs, whereas ethylene glycol is used to reduce the effect of hydrogel evolution at the zinc electrode.