Porous bismuth nanocrystals with advanced sodium ion storage property

Bismuth-based materials are ideal electrodes for sodium-ion batteries (SIBs) due to their high capacity and low cost. However, conventional solid bismuth materials still suffer from severe volume expansion during the reaction process, which hinders its application. Herein, single-crystal bismuth nanospheres with diameters in the range of 200-400 nm were successfully prepared with the Na-Bi alloying mechanism studied using in-situ XRD, which confirms a stepwise process of Bi-*NaBi-*Na3Bi with large volume variation. To address the volume change issue, we introduce a porous structure into the bulk of Bi crystals, which alleviated its volume expansion and suppressed its cyclic failure. An in-situ TEM experiment is further carried out to verify this effective structure-modification strategy, demonstrating its applicable feature for electrode design and performance enhancement.

Automated summary

This study successfully synthesized single-crystal bismuth nanospheres and investigated the alloying mechanism with sodium. By introducing a porous structure, the volume expansion issue was addressed and cyclic failure was suppressed. In-situ TEM further confirmed the effectiveness of this structure-modification strategy for electrode design and performance enhancement.