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

Abstract 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 Fe 3 O 4 hollow nanospheres as partial self-templates, we construct sandwich-like double nitrogen-doped C-shelled porous Fe 3 O 4 hollow spheres by pyrolyzing polypyrrole (PPY) which is in situ polymerized on the interior and the exterior shells of Fe 3 O 4 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 Fe 3 O 4 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 Fe 3 O 4 hollow spheres (C N@Fe 3 O 4 @C N 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.