High-loading Fe₂O₃/SWNT composite films for lithium-ion battery applications

Single-walled carbon nanotube (SWNT) films are a potential candidate as porous conductive electrodes for energy conversion and storage; tailoring the loading and distribution of active materials grafted on SWNTs is critical for achieving maximum performance. Here, we show that as-synthesized SWNT samples containing residual Fe catalyst can be directly converted to Fe₂O₃/SWNT composite films by thermal annealing in air. The mass loading of Fe₂O₃ nanoparticles is tunable from 63 wt% up to 96 wt%, depending on the annealing temperature (from 450 °C to 600 °C), while maintaining the porous network structure. Interconnected SWNT networks containing high-loading active oxides lead to synergistic effect as an anode material for lithium ion batteries. The performance is improved consistently with increasing Fe₂O₃ loading. As a result, our Fe₂O₃/SWNT composite films exhibit a high reversible capacity (1007.1 mA h g^-1 at a current density of 200 mA g^-1), excellent rate capability (384.9 mA h g^-1 at 5 A g^-1) and stable cycling performance with the discharge capacity up to 567.1 mA h g^-1 after 600 cycles at 2 A g^-1. The high-loading Fe₂O₃/SWNT composite films have potential applications as nanostructured electrodes for various energy devices such as supercapacitors and Li-ion batteries.