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1.
Polymers (Basel) ; 13(7)2021 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-33916722

RESUMO

The use of dipolar aprotic solvents to swell lithiated Nafion ionomer membranes simultaneously serving as electrolyte and separator is of great interest for lithium battery applications. This work attempts to gain an insight into the physicochemical nature of a Li-Nafion ionomer material whose phase-separated nanostructure has been enhanced with a binary plasticiser comprising non-volatile high-boiling ethylene carbonate (EC) and sulfolane (SL). Gravimetric studies evaluating the influence both of mixing temperature (25 to 80 °C) and plasticiser composition (EC/SL ratio) on the solvent uptake of Li-Nafion revealed a hysteresis between heating and cooling modes. Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) revealed that the saturation of a Nafion membrane with such a plasticiser led to a re-organisation of its amorphous structure, with crystalline regions remaining practically unchanged. Regardless of mixing temperature, the preservation of crystallites upon swelling is critical due to ionomer crosslinking provided by crystalline regions, which ensures membrane integrity even at very high solvent uptake (≈200% at a mixing temperature of 80 °C). The physicochemical properties of a swollen membrane have much in common with those of a chemically crosslinked polymer gel. The conductivity of ≈10-4 S cm-1 demonstrated by Li-Nafion membranes saturated with EC/SL at room temperature is promising for various practical applications.

2.
Chempluschem ; 85(12): 2580-2585, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-33155772

RESUMO

The quality of ion-selective membranes determines the efficiency of Vanadium Flow Batteries (VFBs), and alternatives to expensive Nafion™ materials are actively being searched for. One of the membrane architecture approaches is to imitate the Nafion™ structure with two separate phases: a conductive sulfonated polymer and an inner matrix. We introduce a new composite material based on sulfonated styrene polymerized inside the pores of a stretched PTFE matrix. Variation of polystyrene content and a sulfonation degree allowed to obtain membranes with IEC from to 0.96 to 1.84 mmol/g. Balanced vanadium permeability (ca. 5.5 ⋅ 10-6  cm2 /min) and proton conductivity (ca. 50 mS/cm) were achieved for the material with 21-23 % polystyrene content and a sulfonation degree up to 94 %. Membranes showed stable cycling with 81 % energy efficiency in a single-cell VFB. This work contributes to the existing knowledge of Nafion alternatives by providing a cheap and scalable method of membrane production.

3.
Molecules ; 24(21)2019 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-31731434

RESUMO

A series of carbon aerogels (C-AGs) were prepared by the pyrolysis of resorcinol-formaldehyde aerogels at 700-1100 °C as potential supercapacitor electrodes, and their texture and electrochemical properties were determined. The specific surface area of all C-AGs was in the range of 700-760 m2/g, their electron conductivity increased linearly from 0.4 to 4.46 S/cm with an increase of the pyrolysis temperature. The specific capacitance of electrode material based on C-AGs reached 100 F/g in sulfuric acid and could be realized at a 2 A/g charge-discharge current, which makes it possible to use carbon aerogels as electrode materials.


Assuntos
Carbono/química , Formaldeído/química , Géis/química , Resorcinóis/química , Capacitância Elétrica , Condutividade Elétrica , Eletroquímica , Eletrodos , Géis/síntese química , Nitrogênio/química , Temperatura
4.
Dalton Trans ; (14): 2170-9, 2004 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-15249954

RESUMO

Density functional B3LYP calculations have been performed to investigate proton transport in orthoperiodic and orthotellurium acids, their salts MIO(6)H(4)(M = Li, Rb, Cs) and CsH(5)TeO(6), dimers of the salt*acid type MIO(6)H(4)*H(5)IO(6)(M = Rb, Cs), CsIO(6)H(4)*H(6)TeO(6), CsHSO(4)*H(6)TeO(6), Cs(2)SO(4)*H(6)TeO(6), and also in double-substituted and binary salts Rb(2)H(3)IO(6) and Rb(4)H(2)I(2)O(10). It has been shown that the energy of salt dimerization is 33-35 kcal mol(-1) and the activation barrier for proton migration between the neighboring octahedrons of the salt*acid --> acid*salt type is calculated to be 3-13 kcal mol(-1). The activation energy of the proton migration along the octahedron, 20-30 kcal mol(-1), is comparable with the barrier for water molecule separation. Quantum-chemical calculations correlate with the results of X-ray and electrochemical studies.

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