Ant-nest-like Cu2-xSe@C with biomimetic channels boosts the cycling performance for lithium storage.

Controlling the microstructure and composition of electrodes is crucial to enhance their rate capability and cycling stability for lithium storage. Inspired by the highly interconnected network and good mechanical integrity of an ant-nest architecture, herein, a biomimetic strategy is proposed to enhance the electrochemical performance of Cu2-xSe. After facile carbonization and selenization treatments, the 3D Cu-MOF is successfully transformed into the final ant-nest-like Cu2-xSe@C (AN-Cu2-xSe@C). The AN-Cu2-xSe@C is composed of interconnected Cu2-xSe channels with amorphous carbon coated on the outer surface. The 3D interconnected channels within the AN-Cu2-xSe@C provide fast charge transport pathways and enhanced structural integrity to tolerate the large volume fluctuations of Cu2-xSe during cycling. When applied as the anode for lithium storage, the AN-Cu2-xSe@C shows remarkable electrochemical performance with a high capacity of 1452 mA h g-1 after 1200 cycles at 1.0 A g-1 and 879 mA h g-1 after 2500 cycles at 10.0 A g-1, respectively. Mechanism investigations demonstrate that the AN-Cu2-xSe@C experiences complicated conversion-intercalation co-existence reactions upon cycling. The existence of capacitive behaviour (74%) also contributes to the extended cycling performance. Our work offers a new avenue for designing a high performance electrode using the biomimetic concept.

A hierarchical structure of a Co0.85Se@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 Co0.85Se@N-doped carbon as the yolk and the first shell and nanosized Co0.85Se@N-doped carbon and ZnSe@N-doped carbon hetero-components as the second shell (marked as Co0.85Se@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, Co0.85Se@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.