Free-Standing Layer-By-Layer Hybrid Thin Film of Graphene-MnO2 Nanotube as Anode for Lithium Ion Batteries

Free-standing layer-by-layer assembled hybrid graphene-MnO2 nanotube (NT) thin films were prepared by an ultrafiltration technique and studied as anodes for lithium ion batteries. Each thin layer of graphene provides not only conductive pathways accelerating a conversion reaction of MnO2 but also buffer layers to maintain electrical contact with MnO2 NT during lithium insertion/extraction. In addition, the unique structures of the thin film provide porous structures that enhance Li ion diffusion into the structure. The graphene-MnO2 NT films as anode present excellent cycle and rate capabilities with a reversible specific capacity based on electrode composite mass of 495 mAh/g at 100 mA/g after 40 cycles with various current rates from 100 to 1600 mA/g. On the contrary, graphene-free MnO2 NT electrodes demonstrate only 140 mAh/g at 80 mA/g after 10 cycles. Furthermore, at a high current rate of 1600 mA/g, the charge capacity of graphene-MnO2 NT film reached 208 mAh/g.