Electrochemical Study of Phase Transition Processes in Lithium Insertion in V[sub 2]O[sub 5] Electrodes

Abstract

The lithium intercalation into a V 2 O 5 substrate was studied by chronopotentiometry. The samples were prepared by atomic layer chemical vapor deposition which provides homogenous and coherent layers at the surface of titanium plates. During the chargedischarge process, various phase transitions occurred in the system Li-V 2 O 5 which induced a large change in the diffusion coefficient of lithium. To obtain an accurate analysis of the intercalation mechanism, the diffusion equation with a variable diffusion coefficient was solved by digital simulation. The thermodynamic and kinetic properties of the system are represented by an analytical model based on the complementary error function. This procedure was useful for study of the electrode behavior in a large concentration range or in a large potential domain. The influence of various parameters, such as the thickness of the sample or the thermodynamic enhancement factor, were examined.

Li diffusion and electrochromism in amorphous and crystalline vanadium oxide thin film electrodes

“…In the literature, 16,17,[24][25][26] measurements of DC as a function of the Li-inserted charge in crystalline Li x V 2 O 5 electrode films confirm our results of a dependence between the Li-diffusion coefficient and the crystalline phases of this compound. Figure 5 shows the electrochromic effect measured by the optical transmittance at 632.8 nm as a function of the charge, for one galvanostatic charge-discharge cycle and the concurrent electrode potential curves.…”

“…23 Figure 4 shows that the dependence of DC on the crystalline phases for sample E is very similar to that obtained for sample D, for which the DC increases with the inserted charge in the δ single-phase region and with the effective DC decreasing in the δ+γ two-phase region. The absence of the two peaks in the DC curve of sample E, one at the region comprising the ε single-phase and ε+δ two-phase, and the other at the middle of the δ phase, can be assigned to the low resolution in the experimental data of this sample, as it can be seen by the scarceness of points on its DC and potential curves, when compared to the experimental data points of sample D.On this supposition, we inquire also if the peak and the shoulder observed in the DC curve of the film treated at 300 o C (sample C), around 2.7 and 2.4 V in the corresponding V e curve, would not be due to the presence of micro or nanocrystallites phases in the film composition.In the literature, 16,17,[24][25][26] measurements of DC as a function of the Li-inserted charge in crystalline Li x V 2 O 5 electrode films confirm our results of a dependence between the Li-diffusion coefficient and the crystalline phases of this compound. Figure 5 shows the electrochromic effect measured by the optical transmittance at 632.8 nm as a function of the charge, for one galvanostatic charge-discharge cycle and the concurrent electrode potential curves.…”

Using an Atmospheric Pressure Chemical Vapor Deposition Process for the Development of V2O5 as an Electrochromic Material

“…Additionally, it is well known that the Li + intercalation/deintercalation response is dependent on the diffusion coefficient of the species; consequently, a large diffusion coefficient will result in a fast response [40]. The diffusion coefficient of APCVD V2O5 estimated in this work is higher than V2O5 grown by atomic layer CVD [41], solution process [42], spin-coating [43], and pulsed spray pyrolysis [44], strengthening the growth of large area electrodes by APCVD with good electrochemical performance. …”

Thin films of vanadium oxide grown on vanadium metal: oxidation conditions to produce V2O5 films for Li-intercalation applications and characterisation by XPS, AFM, RBS/NRA

“…12, the cyclic voltammogram performed in a potential window between 2.8 and 3.8 V shows two reversible peaks at about 3.4 and 3.2 V. This is in accordance with the reported lithium intercalation behaviour of crystalline V 2 O 5 films produced by various deposition techniques, including sol-gel and ALD. 1,7 Assuming that 1 Li per V 2 O 5 molecule can be inserted, the thickness of the inserted V 2 O 5 layer can be calculated from the charge of the CV peaks. For the oxide film formed by 5 min oxidation at 750 mbar O 2 at 500°C, a thickness of 134 nm is obtained.…”