An ultra-thin composite magnesium anode with controlled (002) facet orientation by heterogeneous epitaxial electrodeposition for highly stable lean-magnesium metal batteries

Abstract

The composite magnesium anode is essential for constructing sustainable and high-energy-density lean-magnesium metal batteries, as it addresses magnesium overload on anode, low coulombic efficiency and unsatisfied lifespan triggered by inhomogeneous Mg deposition behavior. Herein, a strategy is developed to regulate epitaxial growth orientation of magnesium crystal grain via an artificial interfacial fluorine-doped inorganic carbon (CF) layer on commercial Cu-foil substrate, enabling the fabrication of highly stable ultra-thin composite magnesium anodes with preferred Mg (002) orientation. The CF-Cu exhibits a high lattice match and strong adsorption with the Mg (002) facet, promoting (002)-oriented nucleation and grain-refined growth parallel to substrate plane for only a 13 µm thick magnesium layer, ultimately enhancing Mg plating/stripping reversibility. Additionally, incorporating F-ion facilitates the in-situ formation of magnesiophilic inorganic component MgF₂, accelerating Mg²⁺ transport kinetics for rapid crystal nucleation. The resulting anode achieves a high coulombic efficiency of 99.7% over 1400 cycles at 1 mA cm⁻², with a polarization of 0.2 V and a lifetime exceeding 3000 h in symmetric cells. Furthermore, the full cell exhibit improved capacity, superior dynamics and enhanced cycle performance. This work highlights the designed multifunctional ultra-thin composite magnesium anodes based on commercially available substrate for high-stability lean-magnesium metal batteries.