Three dimensionals α-Fe₂O₃/polypyrrole (Ppy) nanoarray as anode for micro lithium ion batteries

Three dimensional, self-supported α-Fe₂O₃/Ppy composite electrode with enhanced specific areal capacity and rate performance was successfully fabricated by a simple, low-cost, two-steps process consisting of direct heating of iron foil in air and subsequent coating of conducting polymer Ppy on the α-Fe₂O₃ nanoflakes. By using α-Fe₂O₃/Ppy as the anode materials with iron foil as the current collector, the unique structure affords a highly conductive pathway for electron, a short diffusion length for ions, a fast mass transport channel for electrolyte, and sufficient void space for accommodating large volume variations during Li intercalation/diintercalation for Li-ion battery. A relatively high specific capacity of 0.42mAh/cm² can be achieved at 0.1mA/cm² even after 100 charge/discharge cycles, with a plateau potential of 1V and nearly 100% Coulombic efficiency, suggesting the feasibility to use this unique 3D nanostructured hybrid composite for microbattery in both small and large scale applications.