Asymmetric electrolytes govern tetrahydroxozincate dynamics for stable alkaline zinc batteries

Abstract

Green electrochemical energy storage is essential for carbon neutrality, and alkaline zinc batteries offer a compelling solution due to their inherent safety, low cost, and high energy density. However, their performance is limited by parasitic reactions, including corrosion, gas evolution, and slow Zn/ZnO conversion kinetics stemming from inefficient dissociation of the tetrahydroxozincate [Zn(OH)42−] intermediate. We address this by designing a series of cobalt porphyrins (Co-4N, Co-3N-O, Co-3N-S) that modulate the metal center's charge density for accelerating Zn(OH)42− decomposition, and control Zn2+ transport through the carboxyl-functionalized peripheries. The Co-3N-O-modified electrolyte achieves exceptional stability, maintaining stable cycle for over 80,000 s at 5 mA cm−2, which is more than four times longer than the <20,000 s achieved by the conventional KOH + ZnO electrolyte. In Zn Ni batteries, this molecularly engineered electrolyte enables 110 stable cycles at 1 mA cm−2, significantly outperforming the unmodified system, which sustained only 20 cycles. These findings elucidate a structure-kinetics relationship for zincate regulation and demonstrate how customized molecular asymmetry can overcome persistent challenges in aqueous battery chemistry, offering a pathway to high-performance, durable energy storage systems.