Suppression of side reactions on Zn metal anode by Bi-coated zincophilic three-dimensional Cu host for aqueous Zn-ion batteries

Abstract

Rechargeable aqueous Zn-ion batteries have garnered significant interest due to their inherent safety and high power density. However, the long-term cycling performance of the Zn metal anode is impeded by several challenges, including the formation of Zn dendrites, undesirable side-reactions such as the hydrogen evolution reaction (HER), and corrosion. Herein, a three-dimensional (3D) host with a surface coating was employed for the Zn metal anode. A 3D Cu foam was formed using an H₂ bubble template, followed by a galvanic displacement reaction with a [BiCl₆]^3- complex to exploit the chemical properties of Bi, such as its strong affinity for Zn and inertness toward the HER. The resulting 3D Bi-Cu foam synthesized through this method effectively alleviates dendrite growth and inhibits side-reactions, enhancing the lifespan of the battery. In half cell, the 3D Bi-Cu foam exhibited an ultralow nucleation overpotential of 4 mV (vs. Zn²⁺/Zn) at 1 mA cm⁻². In addition, it showed stable cycling for 1000 cycles with an average Coulombic efficiency of 99.5 % at 10 mA cm⁻², indicating that a highly reversible redox reaction occurs during cycling. Moreover, the enhanced performance in symmetric cell and full cell with δ-MnO₂ cathode further highlights the advantages of the 3D Bi-Cu foam.