In Situ Formation of a Bi/Mg‐Based Hybrid Interphase for Highly Reversible Magnesium Metal Anodes
Jingxuan Bi, Junhui Li, Zhenkai Zhou, Boxin Li, Ke Wang, Guowei Gao, Zhuzhu Du, Wei Ai, Wei Huang
Abstract
Abstract Magnesium (Mg) is a promising anode material for magnesium metal batteries (MMBs) owing to its high specific capacity, excellent safety profile, and abundant availability. However, pristine Mg anodes suffer from uneven plating/stripping and surface passivation/corrosion, limiting the safety and cycling stability of MMBs. This study introduces a Bi/Mg‐based hybrid interphase protective layer on Mg foil (denoted Bi‐Mg@Mg) through an in situ quasi‐solid–solid redox reaction by immersing the foil in a bismuth oxybromide suspension. The resulting interphase layer consists of magnesiophilic components (Bi metal and Bi 2 Mg 3 alloy) and magnesiophobic species (MgO, MgBr 2 , and BiBr 3 ). These components synergistically enhance the desolvation, nucleation, and deposition kinetics, mitigate side reactions, and promote uniform electric field and ion flux distributions. As a result, the Bi‐Mg@Mg electrodes exhibit superior Mg plating/stripping reversibility, maintaining stable performance for over 4100 h in the all‐phenyl complex electrolyte and 2900 h in the Mg(TFSI) 2 electrolyte, significantly outperforming pristine Mg electrodes. Furthermore, full cells paired with Mo 6 S 8 and S cathodes demonstrate excellent capacities, rate capabilities, and long lifespans, highlighting the exceptional electrochemical performance of the Bi‐Mg@Mg anode. This study offers a promising strategy for developing highly reversible Mg anodes, paving the way for practical long‐cycle MMBs.