On the rising extra storage capacity of ultra-small Fe3O4 particles functionalized with HCS and their potential as high-…

We report a nanocomposite material exhibiting ultra-small Fe3O4 nanoparticles uniformly decorated on hollow carbon spheres (Fe3O4@HCS). The unique hierarchically-structured material displays excellent electrochemical cycling performance that exceeds the theoretical bulk capacity of Fe3O4 when used as an anode in lithium-ion batteries. In particular, it features increasing reversible capacity upon cycling yielding 1050 mAh g−1at 0.1 A g−1 in cycle 250. Comprehensive scanning and transmission electron microscopy images combined with detailed electrochemical analysis demonstrate that the outstanding electrochemical performance can be traced back to the formation and decomposition of a capacitative surface layer during dis/charging.