Bismuth‐Integrated Nitrogen‐Doped Carbon Nanostructures Enabling Broad Electrolyte Compatibility for Mg‐Ion Batteries

Bismuth has emerged as a promising alloying anode for magnesium‐ion batteries (MIBs), offering high theoretical capacity with a low electrode potential, and thus serving as a viable alternative to Mg metal. Herein, Bi nanoparticle (NP)‐integrated nitrogen‐doped carbon nanostructures (Bi@nCN) are synthesized via a scalable one‐step carbothermal reduction of BiOCl and Mg phthalocyanine. The resulting Bi@nCN features finely dispersed Bi NPs embedded in a nitrogen‐doped carbon matrix, forming a stress‐relieving architecture that accommodates the structural changes associated with the two‐phase reaction between Bi and Mg ₃ Bi ₂ . Bi@nCN demonstrates excellent electrochemical performance, with high capacity retention, superior rate capability, and minimal polarization growth. Furthermore, full cells employing Bi@nCN anodes exhibit stable operation in chloride‐free electrolytes, including ether‐ and nitrile‐based systems, in which Mg metal typically develops insulating passivation layers. These findings highlight the potential of Bi@nCN to enable stable Mg‐ion storage in chloride‐free electrolytes, overcoming the intrinsic limitations of Mg metal anodes and expanding the scope of MIB chemistry with new electrolyte and cathode combinations.