New Organic−Inorganic Nanocomposite Materials for Energy Storage Applications

Abstract

A method is described by which the disulfide dimer of 2,5-dimercapto-1,3,4-thiadiazole (diDMcT, see Scheme 1) can be oxidatively intercalated into the layered structure of a V2O5 xerogel. This intercalation reaction produces a new organic−inorganic composite material with a layer spacing of 13.5 Å, in contrast to the 11.55 Å spacing for the parent V2O5 xerogel. During this oxidative intercalation, the diDMcT is polymerized to produce a polymer with thiadiazole rings linked by disulfides in the polymer main chain (PDTT, see Scheme 1). The composite material is characterized by UV−visible spectroelectrochemistry, X-ray diffraction, FTIR, and electrochemistry. The electrochemical experiments comprised charging (oxidation) and discharging (reduction) of the material, with the bulk of the redox reaction occurring over a broad potential range of 0.5 to −0.6 V versus saturated calomel electrode. The cyclic voltammogram of the composite material shows features that can be attributed to the DMcT−PDTT redox response. However, during or after reduction of the composite, the monomeric DMcT dithiolate appears to be expelled from the V2O5 interlayer region, leading to an evolution of the electrochemical response back to that of the original V2O5 material. Evidence is presented suggesting that the V2O5 host material facilitates the redox reactions of the thiol−disulfide redox couple while it is within the interlayer region.

Electrochemical behavior and structural changes of V2O5 xerogel

“…The film was cycled until curves became invariant, after which the voltammogram was recorded. The current profile is similar to that previously reported for V 2 O 5 , 30 where the current peaks are associated to the redox process V 4+ /V 5+ . The presence of more than one cathodic or anodic current peaks in the voltammogram can be associated to modifications in the structure (modifying the electronic states of the conduction band), which allow the intercalation/ deintercalation of more lithium ions in different sites to compensate the charge injected/ejected in the film.…”

Hybrid Intercalative Nanocomposites

“…In addition to the aforementioned catalytic formation of polyethylene-polystyrene composites, mention should be made of the preparation of such materials by mixing a methanolic solution of 2,5-dimercapto-1,3,4-thiadiazole and aniline with V 2 O 5 · nH 2 O gel in the molar ratio 1 : 2 : 2 [92].…”

Materiais para cátodos de baterias secundárias de lítio

“…Contudo, depois de vários ciclos, o perfil do voltamograma se assemelha ao V 2 O 5 , sugerindo que as moléculas de DMcT produzidas durante a redução dos oligômeros difundem para fora da matriz hospedeira. Este fato foi atribuído à interação repulsiva entre a rede do óxido e as espécies monotiolado e ditiolado do DMcT, carregadas negativamente em potenciais catódicos 199 . Na Figura 14 são mostrados o primeiro e segundo ciclos do nanocompósito PDTT/ V 2 O 5 , indicando a tendên-cia na diminuição da carga atribuída a deintercalação de DMcT/PDTT.…”

“…[199] mostrando um aumento superior a 40% na capacidade específica em relação ao aerogel V 2 O 5 202 . Outro exemplo da classe dos materiais híbridos é o que abrange os cátodos formados entre PCEs e os polioxometalatos como o fósforomolibdato, por exemplo 203 .…”