Metal-organic framework-based ion diffusion regulation layer for aqueous electrolyte zinc metal batteries

Abstract

Aqueous zinc metal batteries are suitable alternative for lithium-ion batteries due to the non-flammable nature of the aqueous electrolyte and a low negative standard redox potential, and a substantial theoretical capacity attributed to the zinc metal anode. In addition, the anodeless zinc metal battery system is a next-generation battery system thanks to its high energy density, simplified manufacturing, and low cost. However, dendrite formation and corrosion hinder the commercialization of aqueous zinc metal batteries. In this study, we employ a metal-organic framework-based layer on the copper current collector to mitigate the diffusion of water molecules and other ions toward the electrode, reducing the electrode corrosion and regulating the diffusion of zinc ions. Molecular dynamics and electrochemical analyses show that the protection layer increases the ratio of zinc ion transport relative to the overall ion transport in the zinc sulfate electrolyte but also change the solvation structure inside the porous protection layer. This enhancement is attributed to size exclusion/steric hindrance imposed by the nano-sized pores of metal-organic frameworks. As a result, MOF-5@Cu exhibited almost 5 times longer cycle life at Zn||Cu half-cell and higher Coulombic efficiency with higher specific capacity and cycle stability at NVO cathode full cell.