A 3D MoOx/carbon composite array as a binder-free anode in lithium-ion batteries

Abstract

Molybdenum(VI) oxide (MoO₃) nanorod arrays were synthesized employing a template-assisted method. A polycarbonate membrane as a template was vacuum infiltrated with an aqueous solution of ammonium heptamolybdate. Template removal by oxygen plasma etching and calcination leads to the formation of highly crystalline 3D MoO₃ nanorod arrays as a negative replica of the template. By applying sucrose as the carbon precursor, the mantling of the MoO₃ nanorods with a thin carbon coating is obtained. Simultaneously, the direct and binder-free contact between the 3D MoO_x nanorod arrays and the current collector resulting from the carbon coating could be achieved and leads to high capacities of up to 1376, 783, 856, 804 and 324 mA h g⁻¹ for cycles 1, 2, 20, 50 and 200 as well as a coulombic efficiency of 99% for such 3D MoO_x/C composite electrodes. The cycling performance of this 3D MoO_x/C composite material is even more impressive, when comparing the determined experimental capacities with the theoretical capacities of graphite (372 mA h g⁻¹) and MoO₂ (838 mA h g⁻¹). Additionally, MoO₃ nanorod array electrodes without such an encapsulating carbon coating show an average capacity of only 175 mA h g⁻¹ between cycles 20 and 200. Thus, the carbon coating of the MoO₃ nanorod array can increase the electrochemical performance of a lithium-ion cell compared to conventional carbon additives when using MoO₃ as the active anode material. This emphasizes the positive effects of the intimate and efficient electron transport and large surface area of the electrode material based on a minimal footprint architecture in Li-ion cells.