Synthesis of pomegranate-like Bi₂Se₃@C composite for high volume specific capacity lithium storage

Lithium-ion batteries (LIBs) with high volume specific capacity have promising applications in small/microelectronics. However, the contradiction between Li⁺ diffusion kinetics and material compaction density severely restricts its development. The layered bismuth selenide (Bi₂Se₃) with high conductivity and compaction density is a candidate material for LIBs with high volume specific capacity. In this work, Bi₂Se₃@C was synthesized by solvothermal and selenization methods, and the final product exhibits a high specific capacity (468 mAh g⁻¹ at 0.1 A g⁻¹, corresponding to 1862 mAh cm⁻³) and good cycling stability (358 mAh g⁻¹ after 500 cycles at 0.5 A g⁻¹, corresponding to 1445 mAh cm⁻³). The excellent electrochemical performance results from the special morphology of the carbon layer-coated Bi₂Se₃ nanospheres, and the carbon layer not only regulates the volume expansion of Bi₂Se₃ during cycling but also improves the electronic conductivity, which is also confirmed by density functional theory calculation. Ex-situ X-ray diffraction spectrum reveals that the crystal phase of Bi₂Se₃ changed from hexagon to orthogonal after the initial cycle.