Achieving Stable Alkaline Zinc–Iron Flow Batteries by Constructing a Dense Cu@Cu6Sn5 Nanoparticle Functional Layer

Aqueous alkaline zinc–iron flow batteries (AZIFBs) offer significant potential for large-scale energy storage. However, the uncontrollable Zn dendrite growth and hydrogen evolution reaction (HER) still hinder the stable operation of AZIFB. Herein, dense Cu@Cu6Sn5 core–shell nanoparticles are constructed on graphite felt (Cu@Cu6Sn5/GF) to induce zinc plating and inhibit the HER simultaneously. The charge transfer within the Cu6Sn5 alloy shell provides a negative charge to Cu, increasing its ability to attract Zn. The lack of electrons in Sn makes it difficult to undergo HER, which is confirmed by the total internal reflection imaging method. Meanwhile, the Cu core can increase the conductivity between the interface of the GF and Cu@Cu6Sn5. As a result, the Cu@Cu6Sn5/GF electrode demonstrates superior cycling performance in AZIFB with an average Coulombic efficiency of 99.3% in 700 cycles and achieves a maximum power density of 487.6 mW cm–2. This strategy can also be applied to other Zn-based flow batteries.