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

Abstract

The mixing of [V 10 O 28 ] 6À 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 V 2 O 5 (gem-V 2 O 5 ). In contrast, calcination of the amorphous tetrabutylammonium decavanadate allows isolation of a more agglomerated V 2 O 5 consisting of very small crystallites (TBA-V 2 O 5 ). 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-V 2 O 5 cathode deliver higher initial capacity and superior capacity retention than TBA-V 2 O 5 . The smaller crystallite size and higher surface area of TBA-V 2 O 5 allow faster lithium insertion and superior rate performance to gem-V 2 O 5 .

Self-Sulfuration and Carbonization of a Mixed-Metal Aryl Sulfonium Polyoxometalate Hybrid: A Path to Electrocatalytically Active Ternary Composite

“…Yield: 84%. 1 (20 mL, 80-l00 °C). To this solution, 13 mL of 6 M HCl was added dropwise with stirring.…”

“…The topography and nanostructure of the resulting oxide depend on the nature of the precursor. 1 Mixtures of appropriate POMs with organic molecules like dicyandiamide, melamine, thiourea, cysteine, dithioxamide, or polymers like urea formaldehyde resin, etc., are annealed at high temperatures to get the corresponding metal oxide/chalcogenide supported on conductive carbon matrices. 9−13 The organic molecules/polymers act as carbon or heteroatom sources here.…”

“…A few studies have been reported in the literature based on the thermal conversion of POM-hybrids into electrocatalytically active nanocomposites. 1,[10][11][12]26 However, studies concerned with the conversion mechanism of POM-hybrids into nanocomposites under thermal treatment are scarce. 26,27 In a recent review article, Cheng and co-workers have summarized the recent developments in POM-derived materials for electrocatalytic applications.…”

“…Among the various organic counterion motifs used in POM chemistry, the alkylammonium and phosphonium counterions are the most widely explored for preparing POM-based ionic liquids (POM-ILs). − On the other hand, rigid aromatic cations serve as structure-directing units, forming ordered organic–inorganic hybrid materials. − Such hybrids can be subjected to thermal treatment, where the neighboring POM clusters undergo condensation to produce nanostructured bulk metal oxides. The topography and nanostructure of the resulting oxide depend on the nature of the precursor . Mixtures of appropriate POMs with organic molecules like dicyandiamide, melamine, thiourea, cysteine, dithioxamide, or polymers like urea formaldehyde resin, etc., are annealed at high temperatures to get the corresponding metal oxide/chalcogenide supported on conductive carbon matrices. − The organic molecules/polymers act as carbon or heteroatom sources here.…”

“…Polyoxometalates (POMs), the nanosized (∼1 nm size) anionic metal oxide clusters of early transition metals (W, Mo, Nb, Ta, V), and soluble molecular fragments of bulk metal oxides can serve as viable precursors for fabricating metal oxides in nano dimensions. 1 The properties of a POM cluster, such as its solubility, stability, and redox behavior, can be modulated by the charge balancing counterions. 2 Among the various organic counterion motifs used in POM chemistry, the alkylammonium and phosphonium counterions are the most widely explored for preparing POM-based ionic liquids (POM-ILs).…”