Revealing the Magnesium‐Storage Mechanism in Mesoporous Bismuth via Spectroscopy and Ab‐Initio Simulations
Xin Xu, Dongliang Chao, Biao Chen, Pei Liang, Huan Li, Fangxi Xie, Kenneth Davey, Shi‐Zhang Qiao
Abstract
Abstract We present mesoporous bismuth nanosheets as a model to study the charge‐storage mechanism of Mg/Bi systems in magnesium‐ion batteries (MIBs). Using a systematic spectroscopy investigation of combined synchrotron‐based operando X‐ray diffraction, near‐edge X‐ray absorption fine structure and Raman, we demonstrate a reversible two‐step alloying reaction mechanism Bi↔MgBi↔Mg 3 Bi 2 . Ab‐initio simulation methods disclose the formation of a MgBi intermediate and confirm its high electronic conductivity. This intermediate serves as a buffer for the significant volume expansion (204 %) and acts to regulate Mg storage kinetics. The mesoporous bismuth nanosheets, as an ideal material for the investigation of the Mg charge‐storage mechanism, effectively alleviate volume expansion and enable significant electrochemical performance in a lithium‐free electrolyte. These findings will benefit mechanistic understandings and advance material designs for MIBs.