Direct conversion of multilayer molybdenum trioxide to nanorods as multifunctional electrodes in lithium-ion batteries

Abstract

In this study we prepared molybdenum trioxide (MoO3) nanorods having average lengths of 0.5-1.5 μm and widths of approximately 100-200 nm through a one-step mechanical break-down process involving favorable fracturing along the crystal direction. We controlled the dimensions of the as-prepared nanorods by applying various imposing times (15-90 min). The nanorods prepared over a reaction time of 90 min were, on average, much shorter and narrower relative to those obtained over 30 min. Evaluations of lithium-ion storage properties revealed that the electrochemical performance of these nanorods was much better than that of bulk materials. As cathodes, the nanorods could deliver a high specific capacity (>315 mA h g(-1)) with losses of less than 2% in the first cycle at a rate of 30 mA g(-1); as anodes, the specific capacity was 800 mA h g(-1) at a rate of 50 mA g(-1). Relative to α-MoO3 microparticles, these nanorods displayed significantly enhanced lithium-ion storage properties with higher reversible capacities and better rate performance, presumably because their much shorter diffusion lengths and higher specific surface areas allowed more-efficient insertion/deinsertion of lithium ions during the charge/discharge process. Accordingly, enhanced physical and/or chemical properties can be obtained through appropriate nanostructuring of materials.

Exfoliated MoO3 nanosheets for high-capacity lithium storage

“…2e). To the best of our knowledge, this specific capacity value is the highest among other MoO 3 electrodes reported to date (500-900 mAh g −1 ) [19,22,[27][28][29]. As cycle number increases from the 2nd to the 30th, the capacity is steadily increasing probably because more surfaces of the electrode materials are exposed to the electrolyte.…”

“…MoO 3 is a typical layer structured material [19], each layer is composed of two sub-layers which are formed by corner-sharing [MoO 6 ] octahedra along the [001] and [100] directions, and the other two sub-layers are stacked together by sharing the edges of octahedra along the [001] direction [20,21]. An alternate stacking of these layers along the [010] direction with van der Waals interaction leads to the formation of layered MoO 3 (α-MoO 3 ) which is able to act as a temporary host for Li + intercalation (theoretical capacity: 1116 mAh g −1 ) [22].…”

Self‐Assembly Approach for Synthesis of Nanotubular Molybdenum Trioxide/Titania Composite Anode for Lithium‐Ion Batteries

“…The band observed at 820 cm −1 is assigned to the symmetrical stretching vibration of the Mo 2 −O bond (A g /B 1g ), which relates to the corner‐sharing oxygen atom in the two MoO 6 octahedrons . The band at 993 cm −1 is ascribed to the asymmetric stretching vibration of the terminal Mo=O bond (A g /B 1g ) . For the control samples of MoO 3 flakes and MoO 3 powders, typical Raman spectroscopic features that correspond to orthorhombic molybdenum trioxide were observed (Figure S2 b in the Supporting Information); these agree well with the results in Figure b, which indicate the formation of the α‐MoO 3 phase in the nanotubular MoO 3 /TiO 2 composites fabricated by the LbL self‐assembly approach.…”

“…Figure b gives the Raman spectra of the nanotubular MoO 3 /TiO 2 composites, in which a series of bands below 400 cm −1 are indexed to the various vibration modes (e.g., bending, twisting, and fracturing) of the α‐MoO 3 crystal . The band located at 662 cm −1 is attributed to the asymmetrical stretching vibration of the Mo 3 −O bond (B 2g /B 3g ), which results from the edge‐sharing oxygen atom in the three MoO 6 octahedra .…”

“…To this end, metal oxides, especially those with nanoscale structures, have been studied as potential candidates for anode materials applied in LIBs . Among the various metal oxides, orthorhombic MoO 3 (α‐MoO 3 ) stands out, due to its high theoretical capacity (1117 mAh g −1 ), good chemical stability, and eco‐friendliness . More importantly, the unique two‐dimensional layered structure of α‐MoO 3 is suitable for Li‐ion accommodation.…”