Micro-selection and Macro-orientation Strategy Enables High-Areal-Capacity Magnesium Metal Anode

Developing magnesium (Mg) metal electrodes for extended cycling at practical areal capacities is crucial for the commercialization of Mg battery commercialization. However, a higher areal-capacity operation requires greater Mg nucleation ability, which is further complicated by the fact that Mg faces a higher desolvation barrier than Li. This study investigates the correlation between the operated areal capacity and a short circuit. Accelerated lifespan degradation (670 to 15 h) occurs with increased areal capacity due to a short circuit from uneven Mg plating. Using insights, a micro-selection and macro-orientation strategy inspired by glass fiber-MXene (GF-MXene) substrate is developed for controlling Mg plating/stripping at high areal capacity. Synchronous morphological analysis reveals selective Mg plating on microscale MXene sheets and oriented plating/stripping in the macroscopic substrate greatly mitigates short circuiting, delivering high Coulombic efficiency (∼99.4%) for 700 h under 2.5 mAh cm–2 and extended cycle life (340 h) at 5 mAh cm–2, providing practical possibilities for Mg metal anodes applications.