Lithium transition metal (Ti, Nb, V) oxide mesoporous thin films: Contrasting results when attempting direct synthesis by evaporation-induced self assembly

This work investigates the possibility to prepare mesoporous thin films of Li–Ti, Li–Nb, Li–Nb–V and Li–V oxides through a direct sol–gel EISA route by dissolving a lithium salt in the precursor solution. Experimental conditions involve a hydrolysis molar ratio H2O/TM ∼ 10 (TM = Ti, Nb, V) and the common Pluronic structuring agent P123 (EO20–PO70–EO20). Systematic formation of lithium-containing oxides as first-crystallizing phases points to a significant intermixture of lithium and transition metal ions in the inorganic network. In the case of Ti-based and Nb-based oxide films, addition of lithium to the precursor solution is compatible with the formation of amorphous mesoporous films at 350 °C. On the contrary, addition of lithium has a detrimental effect on the notoriously difficult formation of vanadium-based mesostructured films: even when replacing half of the vanadium by niobium as a stabilizer, formation of mesostructured films has not been possible in the investigated range of experimental conditions.

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► A lithium salt was dissolved in the precursor solutions for EISA.
► Wormlike amorphous Li–Ti–O and Li–Nb–O films can be prepared.
► Li–V–O films are not mesoporous.
► Lithium-containing oxides are detected as first-crystallizing phases.
► The P123 decomposition temperature depends on the film composition.