Bilateral Interfaces in In₂Se₃-CoIn₂-CoSe₂ Heterostructures for High-Rate Reversible Sodium Storage

Metal selenides are considered as a group of promising candidates as the anode material for sodium-ion batteries due to their high theoretical capacity. However, the intrinsically low electrical and ionic conductivities as well as huge volume change during the charge-discharge process give rise to an inferior sodium storage capability, which severely hinders their practical application. Herein, we fabricated In₂Se₃/CoSe₂ hollow nanorods composed of In₂Se₃/CoIn₂/CoSe₂ by growing cobalt-based zeolitic imidazolate framework ZIF-67 on the surface of indium-based metal-organic framework MIL-68, followed by in situ gaseous selenization. Because of the CoIn₂ alloy phase in between In₂Se₃ and CoSe₂, a heterostructure consisting of two alloy/selenide interfaces has been successfully constructed, offering synergistically enhanced electrical conductivity, Na diffusion process, and structural stability, in comparison to the single CoIn₂-free interface with only two metal selenides. As expected, this nanoconstruction delivers a high reversible capacity of 297.5 and 205.5 mAh g^-1 at 5 and 10 A g^-1 after 2000 cycles, respectively, and a superior rate performance of 371.6 mAh g^-1 at even 20 A g^-1.