Bismuth Nanoparticle-Embedded Carbon Microrod for High-Rate Electrochemical Magnesium Storage

Bismuth metal is regarded as a promising magnesium storage anode material for magnesium-ion batteries due to its high theoretical volumetric capacity and a low alloying potential versus magnesium metal. However, the design of highly dispersed bismuth-based composite nanoparticles is always used to achieve efficient magnesium storage, which is adverse to the development of high-density storage. Herein, a bismuth nanoparticle-embedded carbon microrod (Bi⊂CM), which is prepared via annealing of the bismuth metal-organic framework (Bi-MOF), is developed for high-rate magnesium storage. The use of the Bi-MOF precursor synthesized at an optimized solvothermal temperature of 120 °C benefits the formation of the Bi⊂CM-120 composite with a robust structure and a high carbon content. As a result, the as-prepared Bi⊂CM-120 anode compared to pure Bi and other Bi⊂CM anodes exhibits the best rate performance of magnesium storage at various current densities from 0.05 to 3 A g^-1. For example, the reversible capacity of the Bi⊂CM-120 anode at 3 A g^-1 is ∼17 times higher than that of the pure Bi anode. This performance is also competitive among those of the previously reported Bi-based anodes. Importantly, the microrod structure of the Bi⊂CM-120 anode material remained upon cycling, indicative of good cycling stability.