Effects of Thermal Annealing on the Li⁺ Intercalation Properties of V₂O₅·nH₂O Xerogel Films

Abstract

V(2)O(5) x nH(2)O xerogel films with n = 1.6, 0.6, and 0.3 have been prepared from the sol-gel route by reacting V(2)O(5) with H(2)O(2) followed by drying under ambient conditions and thermal annealing at 110 and 250 degrees C, respectively. After dehydration, V(2)O(5) crystallizes at 300-330 degrees C, as revealed by thermal gravimetric analysis and X-ray diffraction. Electrochemical characterization demonstrated that V(2)O(5) x 0.3H(2)O film exhibits the best Li(+) intercalation performance, with an initial capacity of 275 mAh/g and a stabilized capacity of 185 mAh/g under a high current density of 100 microA/cm(2) after 50 cycles. Under a low current density of 10 microA/cm(2), the capacity of this film can reach 390 mAh/g. Such an enhanced electrochemical property by thermal treatment is ascribed to the reduced water content, the retained interlayer spacing, and the dominant amorphous phase in the film.

Reduced Surfactant Uptake in Three Dimensional Assemblies of VOx Nanotubes Improves Reversible Li+ Intercalation and Charge Capacity

“…It is apparent that the hydration state and surfactant packing density of the precursors have measurable effects on the overall structure and morphological properties of the nanotubes [41,42] , as evidenced by XRD and TEM data. Since the choice of precursor can determine the long-range structural order and the potential for 3-D assembly formation during HT, we used HRTEM to determine the effect of hydration state and amine uptake/adsorption during HT to determine why a 3-D array of nanotubes formed using the VOTPP precursor (resulting in nano-urchin) would have less ordered nanotubes.…”

Electrochemical Behaviour of V2O5Xerogel and V2O5Xerogel/C Composite in an Aqueous LiNO3and Mg(NO3)2Solutions

“…The amorphous, hydrated form of vanadium pentoxide (V 2 O 5 nH 2 O), has a higher intercalation capacity than its crystalline form, and this was explained by the fact that water molecules expend the interlayer distance of this compound [13]. Under cathodic polarization, the V 2 O 5 nH 2 O xerogel can insert up to three Li atoms, while orthorhom- * corresponding author; e-mail: ivana@ffh.bg.ac.rs bic V 2 O 5 can insert only one Li ion [13]. Xerogel V 2 O 5 nH 2 O can be prepared by the dissolution of V 2 O 5 in an aqueous hydrogen peroxide solution [14,15] following by solvent evaporation.…”

Vanadium-oxide-based electrode materials for Li-ion batteries

“…The content of water in the V2O5·nH2O xerogel directly determines the distance between two adjacent bilayers, as shown in Figure 2.8c. [116] The xerogel samples with n values from 1.6 to 0.3 show reduced interlayer spacing from 11.74 to 11.15 Å. The interlayer spacing of V2O5·nH2O is dramatically lowered to 8.43 Å for n = 0.1.…”

“…[114,116] Thermal treatment has a great influence on the water content of the V2O5·nH2O (Figure 2.8b). [115,116] 1.6 mole of water exists in one mole of the V2O5·nH2O xerogel at room temperature. The 24 V2O5·0.6H2O can be obtained at 110 °C by removing reversibly absorbed water.…”

“…The specific capacities of the V2O5·nH2O xerogel increase, when the content of residual water decreases from 1.6 to 0.3, shown in Figure 2.8d. [116] Among them, V2O5·0.3H2O has the highest capacity, due to the optimal composition that keeps the large interlayer spacing with the least amount of water. However, the V2O5·nH2O suffers from poor cycling stability, due to the reactions of lithium and residual water to form Li2O.…”