Constructing MXene@ZIF-67 Core-shell Heterostructures on Mg Anodes for a High-performance Aqueous Mg Battery

Abstract

The magnesium (Mg) metal anodes of magnesium batteries have attracted significant attention because of their high theoretical capacity, high safety, and low cost. Their development is hindered by the passivation characteristics of magnesium, especially the serious voltage lag and corrosion polarization in aqueous solutions. This study demonstrates a novel approach involving the electrophoresis deposition on the surface of a magnesium electrode with MXene@ZIF-67. MXene@ZIF-67 is a heterojunction material with a core-shell structure obtained from MXene and ZIF-67 by the in-situ growth method. The addition of ZIF-67 not only solves the problem of MXene layer-to-layer instability, but also improves the corrosion resistance of magnesium metal by utilizing the properties of ZIF-67 material topology. The core-shell structure design of the modified film layer enables MXene and ZIF-67 to achieve efficient synergy. On the one hand, the unique lamellar structure of MXene is utilized to achieve uniform Mg²⁺ flux and reduce the interfacial resistance of the magnesium anode, and on the other hand, the unique ionic conductor performance of ZIF-67 enables precise separation of solvent molecules and simultaneous selective Mg²⁺ transport. So, the film is beneficial for interfacial stability and reaction kinetics. The modified Mg battery exhibits a reduction in voltage lag time from 7.2 seconds to 1.3 seconds. A notable reduction in polarity and enhanced stability in plating and stripping was observed in magnesium metal battery for 300 cycles. The DFT calculations show that there is a high adsorption energy between the MXene@ZIF-67 film and the magnesium alloy.