Fe₃O₄/PPy composite nanospheres as anode for lithium-ion batteries with superior cycling performance

Uniform Fe₃O₄/PPy composite nanospheres (FPCNs) with Fe₃O₄ nanoparticles embedded in PPy nanospheres (∼200 nm) were prepared by a hydrothermal process followed by an ultrasonication assisted polymerization. For the first time, FPCNs were used as anode for lithium ion batteries, demonstrating enhanced electrochemical performance with high reversible capacity (544 mA h g^-1 after 300 cycles), remarkable capacity retention (98% of the initial capacity after 300 cycles), as well as good rate capability (332 mAh g^-1 at 2000 mA g^-1). The spherical PPy matrix in FPCNs possesses three functions: 1) buffering the structural variation of Fe₃O₄ nanoparticles during charging/discharging process; 2) preventing the aggregation of Fe ₃O₄ nanoparticles; 3) avoiding the direct contact between Fe₃O₄ nanoparticles and the electrolyte. The results observed in this study may shed some light on the investigation of MO _x/polymer composite electrode materials.