Partial self-sacrificing templates synthesis of sandwich-like mesoporous CN@Fe3O4@CN hollow spheres for high-performance Li-ion batteries

Integrating carbonaceous materials onto nano-scaled porous metal oxides to form shell-core-shell hollow structure has good prospects in the development of high-performance electrode materials for Li-ion battery, but it still remains challenging. Herein, with Fe3O4 hollow nanospheres as partial self-templates, we construct sandwich-like double nitrogen-doped C-shelled porous Fe3O4 hollow spheres by pyrolyzing polypyrrole (PPY) which is in situ polymerized on the interior and the exterior shells of Fe3O4 hollow spheres. And the polymerization time of PPY have important influence on thickness of carbon layer in the composites and further change their electrochemical performance. The shell-core-shell hollow structure offers highly contact between carbon and porous Fe3O4 and provides amount of volume stress buffer nanospaces during electrochemical processes, which promotes electron transport effectively and keeps good structural stability. The obtained sandwich-like double N-doped C-shelled porous Fe3O4 hollow spheres (CN@Fe3O4@CN HSs) are prepared as Li-ion battery anode and show an ultrahigh reversible specific capacity, high rate capability, remarkable cycle stability, excellent capacity retention (high capacity of 1048 mA h g−1 after 300 cycles at 0.1 A g−1, which is about 99.1% of the capacity in the 2nd cycle) and high coulombic efficiency (about 99% over 300 cycles). This research shows great potential of the sandwich-like shell-core-shell hollow structure in Li-ion batteries.