Sol-Gel Synthesis and Electrochemical Characterization of Polycrystalline Powders and Thin Films of Li_1+xV₃O₈

Abstract

Transition metal oxides are extensively investigated due to their ability for intercalating some ions or molecules. This property makes it possible to use these phases as active materials for batteries or electrochromic devices. One of the most interesting cathode materials for lithium secondary batteries is the lithium vanadium oxide, Li_1+xV₃O₈ or Li_2+2xV⁺⁵ _6-2xV⁺⁴ _2xO₁₆ in accordance with the unit cell composition. A new synthesis route shown that this phase can be obtained in the gel state by precipitation from aqueous and methanol solutions containing lithium hydroxide (LiOH) and vanadium pentoxide (V₂O₅) [1], These materials exhibit more homogeneous distances between vanadium and oxygen atoms and fester diflusion of Li⁺ ions in the amorphous form than in the crystalline one. There is also a significant improvement of electrochemical performance for such materials, but the composition control of samples is difficult for this synthetic route because of uncompleted precipitation of lithium and vanadium compounds from aqueous (or methanol) solutions. To avoid this inaccuracy we use the alcoxotechnology technique, the kind of sol-gel processes, for preparation of Li_1+xV₃O₈ from lithium alcoxides (LiOR, R=C₂H₅, i-C₃H₉, i-C₄H₉) and vanadium alcoxides (VO(OR)₃, VO(OR)₂, R= C₂H₅, i-C₃H₉, i-C₄H₉). Polycrystalline powder and films obtained by this route. Structural characteristics and electrochemical properties of the synthesized materials have been also investigated in this work.