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

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 .