Three-dimensional nanoporous Fe₂O₃/Fe ₃C-graphene heterogeneous thin films for lithium-ion batteries

Three-dimensional self-organized nanoporous thin films integrated into a heterogeneous Fe₂O₃/Fe₃C-graphene structure were fabricated using chemical vapor deposition. Few-layer graphene coated on the nanoporous thin film was used as a conductive passivation layer, and Fe ₃C was introduced to improve capacity retention and stability of the nanoporous layer. A possible interfacial lithium storage effect was anticipated to provide additional charge storage in the electrode. These nanoporous layers, when used as an anode in lithium-ion batteries, deliver greatly enhanced cyclability and rate capacity compared with pristine Fe₂O ₃: a specific capacity of 356 μAh cm^-2 μm ^-1 (3560 mAh cm^-3 or ∼1118 mAh g^-1) obtained at a discharge current density of 50 μA cm^-2 (∼0.17 C) with 88% retention after 100 cycles and 165 μAh cm^-2 μm ^-1 (1650 mAh cm^-3 or ∼518 mAh g^-1) obtained at a discharge current density of 1000 μA cm^-2 (∼6.6 C) for 1000 cycles were achieved. Meanwhile an energy density of 294 μWh cm ^-2 μm^-1 (2.94 Wh cm^-3 or ∼924 Wh kg ^-1) and power density of 584 μW cm^-2 μm^-1 (5.84 W cm^-3 or ∼1834 W kg^-1) were also obtained, which may make these thin film anodes promising as a power supply for micro- or even nanosized portable electronic devices.