Enhanced Electrochemical Performance of CNTs/α-Fe2O3/PPy Composite as Anode Material for Lithium Ion Batteries

A novel CNTs/alpha-Fe2O3/PPy composite with three-dimensional interconnected network structure is successfully synthesized through a solvothermal method and in-situ polymerization. The as-synthesized CNTs/alpha-Fe2O3/PPy composite is characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The results indicate that spherical alpha-Fe2O3 particles are densely anchored onto the three-dimensional CNTs conducting network, and the outer PPy layer deposits uniformly on the surface of alpha-Fe2O3 particles. As an anode material for lithium-ion battery, the CNTs/alpha-Fe2O3/PPy composite exhibits a high initial coulombic efficiency of 75.6%, a high specific capacity of 1095.4 mAh.g(-1) at a current rate of 100 mkg(-1) after 50 cycles, as well as a good rate capability at elevated current rates. Compared with pure alpha-Fe2O3, the improved Li storage property could be ascribed to the synergistic effects of alpha-Fe2O3, CNTs and PPy layer. This unique structure not only possesses excellent conductivity under the joint effect of inner randomly distributed CNTs and outer coated PPy layer, which effectively shortens the transfer paths of lithium ions and reduces the contact resistance, but also the outer PPy protective layer prevents agglomeration of alpha-Fe2O3 upon continuous charging/discharging, which withstands huge stresses caused by alpha-Fe2O3 expansion/extraction. The CNTs/alpha-Fe2O3/PPy composite has the potential for use as high-performance anode electrode for Li-ion batteries.