Scale up of fully eco-friendly zinc–O2(ads) batteries from the lab scale to the prototype level

Abstract

Due to their benefits of high specific energy, safety, environmental friendliness and low cost, zinc–air batteries (ZABs) are considered as promising candidates for the next generation of energy storage devices. In this article, we report on the scale-up of our previously developed laboratory cell operating with charcoal cathode and swollen cotton membrane immersed in alkaline electrolyte solution to obtain a multi-cell prototype battery with increased energy density, open-circuit voltage and working discharge current. Furthermore, we designed our battery using adsorbed oxygen (O₂(ads)), allowing the application of a closed system. As a proof of concept, a six-cell battery prototype is developed and built with a capacity of 150 mA h and 148 mW h per cell and an output voltage of 7.5 V. A single cell is tested using galvanostatic, galvanodynamic and electrochemical impedance spectroscopy (EIS) analyses. The invaluable use of distribution of relaxation times (DRT) for rechargeable zinc–air or zinc–O₂(ads) cells is also presented and demonstrated. The EIS Nyquist-plots are evaluated and discussed by means of equivalent circuit models (ECMs) and the DRT method. Further scale-up could aid the development of our zinc–O₂(ads) battery as a low-cost, safe and sustainable technology for deployed energy storage systems (ESS).