Reversible Mg-Metal Batteries Enabled by a Ga-Rich Protective Layer through One-Step Interface Engineering

Regulating the Interfacial Solvation Environment by a Pyran-Based Polymer for High-Areal-Capacity and Low-Temperature-Endurable Magnesium Metal Batteries

Regulating the artificial solid electrolyte interphase (SEI) and interfacial solvation structure of the electrolyte is crucial for developing rechargeable magnesium batteries (RMBs) with long cycling life, high current density tolerance, and fast ion transport capability operated under extreme environments, such as low temperatures. Herein, an effective strategy using oligomeric poly(3,4-dihydro-2H-pyran) (polyDHP) is proposed to modulate the interfacial solvation structure of RMBs, with the construction of an artificial SEI with rapid Mg-ion conductivity. The steric hindrance of polyDHP and its electrostatic interaction with Mg2+ reduce the solvent molecules in the first solvation shell, allowing polyDHP molecules to participate in coordination, thus lowering the desolvation energy barrier of Mg2+ and facilitating their deposition and stripping. Furthermore, due to the glass transition behavior, oligomeric polyDHP exhibits a more ordered structure with more continuous internal ion transport channels at -20 °C, therefore enabling stable RMB operation at lower temperatures for the first time. The corresponding Mg symmetric cells display a much lower overpotential (400 mV) and excellent cycling stability at both room temperature (over 5000 h at 5 mA cm-2 and 10 mA h cm-2) and a low temperature of -20 °C (over 1300 h at 3 mA cm-2 and 3 mA h cm-2). This strategy supports the stable cycling of CuS∥Mg full cells for over 200 cycles at -20 °C. This work reveals the importance of regulating the interfacial solvation structure, promoting the realistic applications of RMBs under extreme conditions.

Large-Scale Integration of the Ion-Reinforced Phytic Acid Layer Stabilizing Magnesium Metal Anode

Rechargeable magnesium batteries (RMBs) have garnered significant attention for their potential in large-scale energy storage applications. However, the commercial development of RMBs has been severely hampered by the rapid failure of large-sized Mg metal anodes, especially under fast and deep cycling conditions. Herein, a concept proof involving a large-scale ion-reinforced phytic acid (PA) layer (100 cm × 7.5 cm) with an excellent water-oxygen tolerance, high Mg2+ conductivity, and favorable electrochemical stability is proposed to enable rapid and uniform plating/stripping of Mg metal anode. Guided by even distributions of Mg2+ flux and electric field, the as-prepared large-sized PA-Al@Mg electrode (5.8 cm × 4.5 cm) exhibits no perforation and uniform Mg plating/stripping after cycling. Consequently, an ultralong lifespan (2400 h at 3 mA cm-2 with 1 mAh cm-2) and high current tolerance (300 h at 9 mA cm-2 with 1 mAh cm-2) of the symmetric cell using the PA-Al@Mg anode could be achieved. Notably, the PA-Al@Mg//Mo6S8 full cell demonstrates exceptional stability, operating for 8000 cycles at 5 C with a capacity retention of 99.8%, surpassing that of bare Mg (3000 cycles, 74.7%). Moreover, a large-sized PA-Al@Mg anode successfully contributes to the stable pouch cell (200 and 750 cycles at 0.1 and 1 C), further confirming its significant potential for practical utilization. This work provides valuable theoretical insights and technological support for the practical implementation of RMBs.