Porous 3D Architecture of Carbon-Encapsulated Fe3O4 Nanospheres Anchored on Networks of Carbon Nanotubes as Anodes for Advanced Lithium-Ion Batteries

Graphical Carbon-encapsulated Fe 3 O 4 nanospheres anchored on carbon nanotubes (Fe 3 O 4 /CNTs@C) have been rationally designed and fabricated. The material shows promising cycle-life and capacity properties for lithium-ion-battery applications. The application of Fe 3 O 4 as anode material for lithium-ion batteries is hindered by the capacity fade owing to its enormous volume expansion and the inherent low conductivity. Herein, carbon-encapsulated Fe 3 O 4 nanospheres anchored on carbon nanotubes (Fe 3 O 4 /CNTs@C) have been successfully fabricated. The obtained Fe 3 O 4 /CNTs@C composites show that numerous Fe 3 O 4 nanospheres are held and connected by the CNT network, forming a composite of porous three-dimensional structure. The unique structure improves the conductivity and structural stability of the Fe 3 O 4 /CNTs@C composite. The encapsulation with carbon enhances the contact between Fe 3 O 4 nanospheres and carbon nanotubes and shortens the ion-transport path. As a result, the Fe 3 O 4 /CNTs@C delivers a high capacity of 612 mA h g −1 at 1 A g −1 , even after 200 cycles, and shows a superior rate performance of 523 mA h g −1 at 5 A g −1 . This work provides a preparation strategy that could be easily applied to other functional materials for energy storage and/or catalysis.