Polyelectrolyte complex membranes as a selective zincate separator for secondary zinc-air battery

Abstract

Zinc-air batteries (ZABs) are being extensively studied as an alternative to lithium batteries due to their high energy density and overall safety benefit. While considerable attention has been given to the development of anodes and cathodes for ZABs, the separator membrane component has received relatively little focus. The separator is supposed to play a critical role in rechargeable ZABs by allowing hydroxide ions to permeate while blocking zincate ions. In this study, we investigated for the first time the potential use of polyelectrolyte complex (PEC) membranes as separators for rechargeable ZABs. These membranes were formed by mixing cationic poly(diallyldimethylammonium chloride) (PDADMAC) and anionic poly(sodium-4-styrenesulfonate) (PSS) at various molar ratios, followed by compression molding of the mixture precipitates after centrifugation. Among the different molar ratios tested, the non-stoichiometric PEC (2:1) membrane exhibited the highest ionic selectivity with a diffusion rate of 1.98 × 10−7 cm2 min−1 for Zn(OH)42−. Subsequently, the PEC membranes were integrated into homemade ZABs, and galvanostatic cycling tests were conducted. Overall, the PEC (2:1) membrane demonstrated superior separator ability for rechargeable ZABs compared to the other prepared molar ratios.