Ion-Replacement Strategy in Preparing Bi-Based MOF and Its Derived Bi/C Composite for Efficient Sodium Storage

To address large volumetric expansion and low conductivity of bismuth-based anodes, an ion-replacement technique is proposed to prepare Bi/C composites, using 1,3,5-benzenetricarboxylicacid (H3BTC) based metal–organic framework as precursors. The characterizations reveal that the Bi/C composite derived from Cu-H3BTC is a sheet structure with the size of 150 nm, and Bi nanoparticles are uniformly dispersed in carbon sheets. When assessed as anode material for sodium ion batteries (SIBs), a sheet-like Bi/C anode exhibits superior sodium storage performance. It delivers a reversible capacity of 254.6 mAh g−1 at 1.0 A g−1 after 100 cycles, and the capacity retention is high at 91%. Even at 2.0 A g−1, the reversible capacity still reaches 242.8 mAh g−1. The efficient sodium storage performance benefits from the uniform dispersion of Bi nanoparticles in the carbon matrix, which not only provides abundant active sites but also alleviates the volume expansion. Meanwhile, porous carbon sheets can increase the electrical conductivity and accelerate the electrochemical reaction kinetics.