Structural phase stability and homogeneity enhancement of electrochemically synthesized Mn2V2O7 by nanocarbon networks

Effect of Carbon Nanotubes on the Na+ Intercalation Capacity of Binder Free Mn2V2O7-CNTs Electrode: A Structural Investigation

“…Raman scattering revealed the presence of Mn 2 O 3 rich β-Mn 2 V 2 O 7 phase in pristine MVO-CNTs electrode sample. The investigations on the various samples it has been found that the MVO structural phase of pristine MVO-CNTs composite was independent from CNTs wt.% and confirmed always as Mn 2 O 3 rich β-Mn 2 V 2 O 7 phase [26].…”

“…After the electrochemical deposition V 2 O 5 .nH 2 O-CNTs-CF sample was washed in deionized water and dried for over night at 80 • C in vacuum oven. To follow the electro-insertion of Mn 2+ cations into V 2 O 5 .nH 2 O structure, the V 2 O 5 .nH 2 O-CNTs-CF were subjected to anodic polarization (+0.15 mA for one hour) in electrolyte prepared with 0.25 mol/liter of Mn(CH 3 COOH) 2 in DI-water (pH = 6) to achieve the final product of MVO on CNTs coated CF substrates [26]. MVO-CNTs-CF electrodes were ready for further electrochemical characterization.…”

“…The MVO-CNTs/CF electrode investigated in the present work was submitted to 20 discharge/charge cycles between 1.0 and 3.5 V vs. Na/Na + at gravimetric density shown in Figure 1. However, as in the reference [26], two voltammetric cycles were applied in the same potential window scan-rate of 0.5 mV.s (MVO-CNTs as pseudo-capacitive behavior). The electrodes were thermally treated at 100 • C temperature under reduced pressure for 12 h before the cells were assembled in an argon filled glove box.…”

“…These alterations in the MVO-CNTs Raman bands with discharge/charge cycles suggest a possible small alteration in the crystallinity associated with the stacking of graphene layers present in the CNTs walls. The CNTs used in the present study have walls that contain cup-stacked structures [26]. We believe that in the potential range where the MVO-CNTs was polarized, Na intercalation is very difficult to occur.…”

“…The probing depth of incident laser light source (λ = 532 nm) was approximately in the range of 0.5-1.0 µm. Figure 3a shows the Raman spectra in the range of MVO Raman shift, where the peak centered in pristine MVO-CNTs sample spectra at ∼830 cm −1 (full width at half maximum (fwhm) = ∼60 cm −1 ) is assigned to O-Mn-O-V-O bonds stretching vibrational modes which is associated to β-Mn 2 V 2 O 7 phase in monoclinic (c2m) symmetry [24,26]. Furthermore the lower Raman shift values at 146 and 470 cm −1 are assigned to [VO 5 -VO 5 ] atomic layers sliding motion in x-y axis plane and O-V-O bending vibrational modes, respectively, in layered α-V 2 O 5 phase [30].…”