Nanostructured Molybdenum-Oxide Anodes for Lithium-Ion Batteries: An Outstanding Increase in Capacity

This work aimed at synthesizing MoO₃ and MoO₂ by a facile and cost-effective method using extract of orange peel as a biological chelating and reducing agent for ammonium molybdate. Calcination of the precursor in air at 450 °C yielded the stochiometric MoO₃ phase, while calcination in vacuum produced the reduced form MoO₂ as evidenced by X-ray powder diffraction, Raman scattering spectroscopy, and X-ray photoelectron spectroscopy results. Scanning and transmission electron microscopy images showed different morphologies and sizes of MoO_x particles. MoO₃ formed platelet particles that were larger than those observed for MoO₂. MoO₃ showed stable thermal behavior until approximately 800 °C, whereas MoO₂ showed weight gain at approximately 400 °C due to the fact of re-oxidation and oxygen uptake and, hence, conversion to stoichiometric MoO₃. Electrochemically, traditional performance was observed for MoO₃, which exhibited a high initial capacity with steady and continuous capacity fading upon cycling. On the contrary, MoO₂ showed completely different electrochemical behavior with less initial capacity but an outstanding increase in capacity upon cycling, which reached 1600 mAh g^-1 after 800 cycles. This outstanding electrochemical performance of MoO₂ may be attributed to its higher surface area and better electrical conductivity as observed in surface area and impedance investigations.