A hierarchical structure of a Co_0.85Se@NC/ZnSe@NC yolk-double-shell polyhedron for long-term lithium storage

Constructing nanostructures with multi-components and delicate architecture exhibits huge potential to improve the lithium storage performance of electrodes. Herein, we report a novel yolk-double-shell structure with complex chemical compositions. Starting with a core-shell structured Co-ZIF@ZnCo-ZIF as a precursor via a simple selenization process, yolk-double-shell polyhedra that assembled by nanosized Co_0.85Se@N-doped carbon as the yolk and the first shell and nanosized Co_0.85Se@N-doped carbon and ZnSe@N-doped carbon hetero-components as the second shell (marked as Co_0.85Se@NC/ZnSe@NC-YDS) are synthesized. Benefiting from their multiple structural advantages, such as high surface area, large pore volume, uniform carbon coating, and intimate heterostructures, Co_0.85Se@NC/ZnSe@NC-YDS exhibits high reversible capacity (1047 mA h g^-1) and good rate capability for lithium storage. More importantly, even after 3000 cycles at 5.0 A g^-1, an impressive reversible capacity of 468 mA h g^-1 is retained with no capacity decay. After repeated discharge/charge processes, the integrated yolk-double-shell structure is still reserved, due to its structural and compositional advantages, which contribute to the enhanced rate and cycling performance.