Sol Gel Synthesis of Li₁₊αV₃O₈. 1. From Precursors to Xerogel

The nature of Li 1+ α V 3 O 8 · n H 2 O gel-like precipitate and corresponding xerogels has been studied. Unlike V 2 O 5 gel, the Li 1+ α V 3 O 8 gels are diphasic materials made of intimately mixed solid and liquid phases having very close Li/V stoichiometry. At room temperature, the solid component contains presumably an hewettite type structure, whereas the liquid part crystallizes into lithiated decavanadic acids. Upon drying at 90 °C, both components lead to hydrated Li 1+ α V 3 O 8 · n H 2 O hewettite-like compounds with different interlayer spacing but with the same water content. By coupling pH measurements, X-ray diffraction, and liquid and magic-angle spinning 51 V NMR, a new mechanism of formation of the Li 1+ α V 3 O 8 gel-like precipitate via solubilized vanadic species is proposed.