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

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).