Enhanced Magnesium Ion Diffusion Kinetics by In Situ Formed Dual‐Redox Centers From Layered Bismuth‐Tellurium Framework

Abstract Rechargeable magnesium batteries (RMBs) are always limited by slow diffusion kinetics of Mg ²⁺ and instability of electrodes or interfaces, depending on the inherent high charge density of Mg ²⁺ and the unsuitability of electrolyte. Herein, a conversion‐alloying dual‐redox storage mechanism governing Mg ²⁺ diffusion in a bismuth/tellurium heterostructure in situ formed form layered Bi ₂ Te ₃ , is proposed to address the dynamic issue. In conjunction with fluorine‐containing electrolyte, the Bi/Te electrodes delivere fast kinetics of Mg ²⁺ , reduces interfacial impedance and stable MgF ₂ /AlF ₃ ‐containing interface layer, achieving remarkable performance in terms of specific capacity and durability. As characterized by time‐of‐flight secondary‐ion mass spectrometry (TOF‐SIMS), a robust solid electrolyte interphase (SEI) capable of conducting Mg ²⁺ is in situ constructed. More, the stepwise redox transitions occurring during electrochemical processes are revealed, involving initial conversion from Bi ₂ Te ₃ to Bi, alloying/dealloying between Bi and Mg ₃ Bi ₂ and reversible conversion between Te and MgTe. These results may contribute to a clear understanding of Bi‐Te based anodes, and even p‐block metal compound anodes, thereby promoting the development and practical application of RMBs.