Mixed molybdenum and vanadium oxide nanoparticles with excellent high-power performance as Li-ion battery negative electrodes

Abstract

a b s t r a c tSeveral nano-sized mixed molybdenum/vanadium oxide monoclinic solid solutions were synthesised using a continuous hydrothermal flow process and studied with a wide range of physical characterization techniques including X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy and X-ray absorption spectroscopy. The nanomaterials were tested as anodes for Li-ion batteries in the potential range 0.05e3.00 V vs. Li/Li þ . Samples with nominal formulas of Mo 0.5 V 0.5 O 2 and Mo 0.33 V 0.67 O 2 showed excellent performance, especially at high current rates, due to their highly pseudocapacitive charge storage mechanism. At a specific current of 10 A g À1 , Mo 0.5 V 0.5 O 2 and Mo 0.33 V 0.67 O 2 showed specific capacities of ca. 200 and 170 mAh g À1 , respectively. Mo 0.5 V 0.5 O 2 also showed good cyclability, with a specific capacity of 480 mAh g À1 after 150 cycles at a specific current of 0.5 A g À1 . For cyclic voltammetries conducted at high scan rates, pseudocapacitive charge storage contributed more than 90% to the total charge storage for both samples. The scalability of the synthesis technique and excellent electrochemical performance at high power, make these materials promising as negative electrode active materials for Li-ion batteries.

Incorporating MoO3 Patches into a Ni Oxyhydroxide Nanosheet Boosts the Electrocatalytic Oxygen Evolution Reaction

“…This further indicates that parts of Mo 6+ are reduced to Mo 5+ on NiMoNS. − On the in situ Mo K-edge XANES spectra of NiMoNS (Figure f), the absorption edge shifts to lower energies with increasing potentials. This reveals that more Mo 5+ are formed on NiMoNS at higher potentials. − The result from the Mo K-edge XANES and EXAFS spectra agrees well with that obtained in XPS observation (Figure ), i.e. , part of Mo 6+ sites are reduced to Mo 5+ sites on NiMoNS.…”

“…As shown in Figure d, the absorption edges of the Mo K-edge XANES spectra for MoO 2 , MoO 3 , and NiMoNS locate at higher energies than that of Mo-foil. This is understandable, considering that the Mo in MoO 2 , MoO 3 , and NiMoNS are in oxidation states. − A pre-peak at 19 995 eV appears on the Mo K-edge XANES spectrum for MoO 3 , and is caused by the mixing of the 2p orbital of O atom with the 5p and 4d orbitals of Mo atom in MoO 3 . − The pre-peak at 19 995 eV is not observed for MoO 2 . On the Mo K-edge XANES spectrum of NiMoNS, the pre-peak at 19 995 eV is present but becomes smaller than that of MoO 3 , implying that parts of Mo 6+ are reduced to Mo 5+ on NiMoNS. − In EXAFS spectra (Figure e), the peaks of NiMoNS locate between MoO 2 and MoO 3 .…”

“…This is understandable, considering that the Mo in MoO 2 , MoO 3 , and NiMoNS are in oxidation states. − A pre-peak at 19 995 eV appears on the Mo K-edge XANES spectrum for MoO 3 , and is caused by the mixing of the 2p orbital of O atom with the 5p and 4d orbitals of Mo atom in MoO 3 . − The pre-peak at 19 995 eV is not observed for MoO 2 . On the Mo K-edge XANES spectrum of NiMoNS, the pre-peak at 19 995 eV is present but becomes smaller than that of MoO 3 , implying that parts of Mo 6+ are reduced to Mo 5+ on NiMoNS. − In EXAFS spectra (Figure e), the peaks of NiMoNS locate between MoO 2 and MoO 3 . This further indicates that parts of Mo 6+ are reduced to Mo 5+ on NiMoNS. − On the in situ Mo K-edge XANES spectra of NiMoNS (Figure f), the absorption edge shifts to lower energies with increasing potentials.…”

“…On the Mo K-edge XANES spectrum of NiMoNS, the pre-peak at 19 995 eV is present but becomes smaller than that of MoO 3 , implying that parts of Mo 6+ are reduced to Mo 5+ on NiMoNS. − In EXAFS spectra (Figure e), the peaks of NiMoNS locate between MoO 2 and MoO 3 . This further indicates that parts of Mo 6+ are reduced to Mo 5+ on NiMoNS. − On the in situ Mo K-edge XANES spectra of NiMoNS (Figure f), the absorption edge shifts to lower energies with increasing potentials. This reveals that more Mo 5+ are formed on NiMoNS at higher potentials. − The result from the Mo K-edge XANES and EXAFS spectra agrees well with that obtained in XPS observation (Figure ), i.e.…”

Enhanced charge storage of nanometric ζ-V2O5 in Mg electrolytes

“…The use of CHFS enabled the production of nano-sized crystallites via highly supersaturating conditions and a short reaction time (residence time on the order of a few seconds), 25,26 and the process has previously produced a wide variety of high-performance nanosized electrode materials for Mg batteries, Liion batteries and supercapacitors. 17,[27][28][29][30][31] Experimental section…”