Self-Assembled Surfactant-Polyoxovanadate Soft Materials as Tuneable Vanadium Oxide Cathode Precursors for...

The mixing of [V₁₀ O₂₈ ]^6- decavanadate anions with a dicationic gemini surfactant (gem) leads to the spontaneous self-assembly of surfactant-templated nanostructured arrays of decavanadate clusters. Calcination of the material under air yields highly crystalline, sponge-like V₂ O₅ (gem-V₂ O₅ ). In contrast, calcination of the amorphous tetrabutylammonium decavanadate allows isolation of a more agglomerated V₂ O₅ consisting of very small crystallites (TBA-V₂ O₅ ). Electrochemical analysis of the materials' performance as lithium-ion intercalation electrodes highlights the role of morphology in cathode performance. The large crystallites and long-range microstructure of the gem-V₂ O₅ cathode deliver higher initial capacity and superior capacity retention than TBA-V₂ O₅ . The smaller crystallite size and higher surface area of TBA-V₂ O₅ allow faster lithium insertion and superior rate performance to gem-V₂ O₅ .