Template synthesis of SnO2/α-Fe2O3 nanotube array for 3D lithium ion battery anode with large areal capacity

Electrodes with three-dimensional (3D) nanostructure are expected to improve the energy and power densities per footprint area of lithium ion microbatteries. Herein, we report a large-scale synthesis of a SnO2/α-Fe2O3 composite nanotube array on a stainless steel substrate via a ZnO nanowire array as an in situ sacrificial template without using any strong acid or alkali. Importantly, both SnO2 and α-Fe2O3 contribute to the lithium storage, and the hybridization of SnO2 and α-Fe2O3 into an integrated nanotube structure provides them with an elegant synergistic effect when participating in electrochemical reactions. Large areal capacities and good rate capability are demonstrated for such a composite nanotube array. Particularly noteworthy is that the areal capacities (e.g. 1.289 mAh cm−2 at a current rate of 0.1 mA cm−2) are much larger than those of many previous thin-film/3D microbattery electrodes. Our work suggests the possibility of further improving the areal capacity/energy density of 3D microelectrodes by designing ordered hybrid nanostructure arrays.