Hydrothermal Synthesis Of Nano Fe₂O₃/CNT For Lithium Ion Storage

With the development of electric vehicles and microelectronic industry, lithium ion batteries (LIBs) with flexibility and high specific capacity have drawn more attention in recent years. However, the low specific capacity of traditional graphite anode (372 mAhg-1) can not satisfy the increasing demand of electronic devices. So transition metal oxides (SnO2, TiO2, SiO2) with high capacity have become the new research hotspots. Fe2O3 with a high theoretical capacity (1005 mAhg-1) is considered as a promising substitute for graphite. However, Fe2O3 as anode for lithium ion battery is restricted by its unsatisfied capacity retention, poor conductivity (1000 Ω.cm) and obvious volume expansion/extraction.Conductive Carbon nanotubes (CNTs) with a 0.55 flcm electrical resistivity can be used as conductive additives in LIBs. The adding of CNTs can reduce the LIBs’ internal resistance and increase the output power by physical mixing or chemical loading with electrode material. Moreover, CNT can be woven into a thin paper as a flexible electron collector in lithium-ion batteries.My thesis mainly involves the synthesis of Fe2O3 loaded CNTs as anode for LIBs by hydrothermal method. Then the proportion of Fe2O3:CNTs was optimized to improve the anode performance. Finally, the binder-free Fe2O3:CNT composite with optimized proportion was filtered into the carbon nanotubes paper under vacuum condition. After that, lithium ion button cell was assembled by using this free-standing composite film as anode, the lithium storage performance of which was evaluated.Micro-morphology of pure Fe2O3 product shows nanosphere with ～125nm. By adding CNT, Fe2O3 particles gradually grow on the wall of CNTs and transform into rhombus shape with ～25 nm. FT-IR indicates that CNT contains functional groups such as COOH and OH. Raman spectrum manifests that the defects on CNTs reduce obviously. By adding CNTs, binding energies of Fe2P and O1s in Fe2O3 increased to 711.8 eV and 530.4 eV, corresponding to the Fe-O-C bond.Lithium storage performance shows that traditional Fe2O3/CNT/Cu anode possesses a capacity of 835 mAh g-1 after 50 charge-discharge cycles and Fe2O3/CNT/carbon nanotube paper anode keeps a reversible capacity of 1178 mAhg-1 after 50 cycles.In this thesis, we successfully synthesized a flexible and light weighted Fe2O3/CNT/Carbon nanotubes paper with excellent conductivity and high capacity as anode for lithium storage. Our research opens a new direction for high capacity and flexible LIBs.