Interface engineering of Cu2-xSe/Bi2Se3 heterostructure in situ encapsulated into porous carbon for superior lithium/sodium ion storage

The integration of heterostructure engineering with carbon materials exhibits significant advantages in enhancing ion transport efficiency and stability, buffering volume changes, and improving electrochemical lithium/sodium storage performance of transition metal selenide electrodes. In this study, we employ binary metal-organic frameworks as the precursors to successfully prepare rod-shaped composites assembled by carbon-coated bimetallic heterostructure nanoparticles (Cu 2-x Se/Bi 2 Se 3 @C) through a controlled selenization process at varying temperatures. The optimized Cu 2-x Se/Bi 2 Se 3 @C-600 composite demonstrate exceptional lithium storage capabilities, achieving high reversible capacities of 1102.3 mAh g −1 at 0.2 A g −1 after 100 cycles and 640.6 mAh g −1 at 1.0 A g −1 after 500 cycles. Ex-situ XRD analysis and theoretical calculations are utilized to elucidate the electrochemical reaction mechanisms and the benefits of the heterointerface in enhancing performance. The density functional theory calculation results indicate that the heterointerface in Cu 2-x Se/Bi 2 Se 3 reduces diffusion energy barrier of surface Li  +  ions and enhances electronic conductivity. The unique structure and composition advantages also grant the optimal composite superior sodium storage performance with high specific capacity (442.7 mAh g −1 at 0.2 A g −1 after 100 cycles), exceptional rate capability (297.3 mAh g −1 at 10.0 A g −1 ), and long-term cyclability (254.7 mAh g −1 at 5.0 A g −1 after 500 cycles).