Binder-free, self-standing films of iron oxide nanoparticles deposited on ionic liquid functionalized carbon nanotubes for lithium-ion battery anodes

We report in-situ synthesis and direct deposition of Fe₂O ₃ nanoparticles (NPs) on the ionic liquid (IL)-functionalized carbon nanotubes (fCNT). As shown in transmission electron microscope (TEM) and scanning TEM (STEM) images, Fe₂O₃ NPs with the diameter of 3-5 nm are randomly distributed on the sidewall of fCNT, revealing the nanocrystalline structure. The chemical identity and interaction of the fCNT/Fe₂O₃ composite are investigated by FT-IR, Raman and XPS analyses. In particular, the fCNT/Fe₂O₃ composite is solution-processable in a form of binder free and self-standing film. Such a free-standing electrode film based on the fCNT/Fe₂O₃ composite achieve the discharge capacity of 413 mAh g^-1 which is much greater than 34 mAh g^-1 of the CNT and 191 mAh g^-1 of the fCNT due to the redox reaction of Fe₂O₃ NPs. Moreover, the fCNT/Fe₂O₃ composite show the coulombic efficiency of 98% and the capacity fading from 272 mAh g^-1 to 182 mAh g ^-1 after 50 cycles of charge/discharge.