A hierarchical structure of a CoSe@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 CoSe@N-doped carbon as the yolk and the first shell and nanosized CoSe@N-doped carbon and ZnSe@N-doped carbon hetero-components as the second shell (marked as CoSe@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, CoSe@NC/ZnSe@NC-YDS exhibits high reversible capacity (1047 mA h g) and good rate capability for lithium storage. More importantly, even after 3000 cycles at 5.0 A g, an impressive reversible capacity of 468 mA h g 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.