High-voltage asymmetric metal–air batteries based on polymeric single-Zn2+-ion conductor

Abstract

<h2>Summary</h2> Asymmetric-electrolyte metal–air batteries (AMABs) deliver high operating voltage and energy density. However, the demand for ion-selective transport separator and precious metal electrocatalysts hampers their applications. To address this issue, we develop a polyacrylonitrile (PAN) separator that can selectively transport Zn²⁺ ions and an atomically dispersed Co electrocatalyst that can catalyze oxygen evolution reactions (OERs) and oxygen reduction reactions (ORRs) in the challenging acidic medium. The selective ion transport behavior was associated with the Zn²⁺ ions' bonded ladder structure of PAN, which raises the ion migration energy barrier for the crossover of H⁺ and OH⁻. In terms of electrocatalysts, extensive <i>ex situ</i> and <i>in situ</i> characterizations suggest that Co single-atom sites stably catalyze the OER and ORR. Several types of AMABs (metals Zn, Si, Sn) were tested. The assembled asymmetric metal–air Zn-, Si-, and Sn-air batteries delivered enhanced battery performance that surpassed those of recently reported Zn-, Si-, and Sn-air batteries, respectively.