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    Structure-performance relations for carbons in Zn-air battery cathodes with non-alkaline electrolytes

    Year: 2023

    Journal: Electrochimica Acta, Volume 456, 2023-07-10, page 142462

    Authors: Kapaev, Roman R.; Ohayon, Amit; Sonoo, Masato; Tzadikov, Jonathan; Shalom, Menny; Noked, Malachi

    Keywords: Carbon; Cathode materials; Energy storage; Oxygen evolution reaction; Oxygen reduction reaction; Zn-air batteries

    Rechargeable Zn-air batteries (RZABs) with non-alkaline electrolytes are a promising type of energy storage devices that potentially combine low cost, high energy density and safety. However, cathode materials for these devices remain poorly developed. We present a systematic study of how structure of carbons affects their performance as cathode scaffolds in non-alkaline RZABs. Ten commercially available types of carbon are characterized and tested in Zn-air battery cathodes with 1 M Zn(OAc)2 or ZnSO4 solutions in H2O as electrolytes. At a low current density (0.1 mA cm−2), there is a roughly linear dependence between the roundtrip energy efficiency and the logarithm of BET surface area, and this dependence is relevant across materials with different morphology and graphitization degree. Lower overpotentials at the initial cycles are observed for cathodes that are more hydrophilic. At higher currents (1 mA cm−2), morphology plays an important role for oxygen reduction kinetics, with nanosized carbons having a much better performance compared to microporous materials with micron-sized particles. Overall, the best performance in non-alkaline RZABs is achieved for nanosized carbons with high specific surface area (>450 m2 g − 1). Our findings help to formulate structural and morphological guidelines for choosing or synthesizing an optimal carbon scaffold for RZABs.
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