Crystal structures, microtopography, morphologies, elemental compositions, and ionic conductivity have been investigated for Li5-xLa3(Nb,Ta)O12-y using X-ray diffraction (XRD), field-emission analytical scanning and transmission electron microscopies (S/TEM), and electrochemical impedance spectroscopy. Using Rietveld refinements with powder XRD patterns, we determined that the number of Li atoms in the formula is less than 5 and that Li5-xLa3(NbTa)O12-y crystallizes in the cubic garnet structure with a space group Ia-3d. Sintering at varying temperatures (750–1000 °C) for 5 h in an ambient atmosphere produced distinct outcomes. Rietveld refinements disclosed that the sample sintered at 1000 °C (Li3.43(2)La3Nb1.07(2)Ta0.93(2)O12-y, a = 12.8361(7) Å, V = 2114.96(3) Å3) exhibited the highest ionic conductivity, while the 850 °C sample had the lowest conductivity, characterized by lower Li concentration and impurity phases (Li(Nb,Ta)3O88, Li2CO3). Analyses, including XRD and electron microscopy, confirmed the 1000 °C sample as a relatively phase pure with enhanced Li content (Li/La = 1.2), larger grains (15 μm), and uniform crystallinity. The 1000 °C sample introduced additional partially filled Li3 (96h) sites, promoting Li migration, and enhancing ionic conductivity. The resulting XRD pattern at 1000 °C has been submitted to the Powder Diffraction File as a reference.

In this study, poly(methyl methacrylate-maleic anhydride) (P(MMA-MAh)) was synthesized in toluene from methyl methacrylate (MMA) and maleic anhydride (MAh) monomers via free radical polymerization, in the presence of 2,2′-Azo-bis-isobutyronitrile (AIBN), as initiator at 80ºC for 8 h. The molar ratio of monomers was found to be 1 MAh:8 MMA using hydrolysis and titration. The molecular weight of co-polymer was determined to be of the order of 104 (g/mol) by gel permeation chromatography. The co-polymer was characterized using Fourier transform infrared and nuclear magnetic resonance spectroscopy. Thermogravimetric analysis indicated the initial decomposition temperature was ~270ºC. Differential scanning calorimetry indicated that the glass transition temperature was near 126ºC.

Rectorite modified with benzyldimethyldodecylammonium chloride (OREC) was used as an additive to modify gel polymer electrolytes (GPEs) which consisted of P(MMA-MAh) used as a polymer matrix, propylene carbonate (PC) as a plasticizer and LiClO4 as the lithium ion source. X-ray diffraction analysis indicates that OREC can exfoliate well in GPEs when the amount of clay is suitable. The temperature dependence of the ionic conductivity of the resulting GPEs agreed well with the VTF (Vogel-Tamman-Fulcher) relation. OREC doses of 5 phr resulted in the greatest ionic conductivity. This OREC addition considerably improved the plasticized retention levels. As a consequence of OREC occupying the free volume space in the polymer matrix of GPEs, the bulk resistance of the GPEs was reduced and the glass transition temperature (Tg) increased.

A grafted polymer (P(MMA-MAh)-PEGME)) was synthesized by reacting poly(ethylene glycol) monomethyl ether (PEGME) with copolymer of poly(methyl methacrylate-maleic anhydride) (P(MMA-MAh)and end-capping the residual carboxylic acid with methanol. Natural rectorite (REC) was made organophilic by modification with the surfactant dodecyl benzyl dimethyl ammonium chloride. The organoclay was termed OREC and was used as a filler additive to modify gel polymer electrolytes (GPEs) which consisted of the grafted polymer (used as a polymer matrix), propylene carbonate (PC) as a plasticizer and LiClO4 as a lithium ion producer.

The temperature dependence of the ionic conductivity of the GPEs agreed well with the VTF (Vogel-Tamman-Fulcher) relation. 5 phr doses of OREC resulted in the highest ionic conductivity. Using OREC also considerably improved the plasticizer retention levels. As a consequence of OREC occupation of the free volume space in the polymer matrix of GPEs, the bulk resistance of the GPEs was reduced and the glass transition temperature (Tg) increased. From the present research, it can be concluded that the incorporation of PEGME into the copolymer of P(MMA-MAh) produced a great improvement in ionic conductivity, plasticizer retention capability and movement of carrier charge of Li+.

In liquid-filled batteries, the liquid electrolytes may escape or present a fire hazard and an inert spacer is needed to separate the electrodes. Alternative polymer-based electrolytes are of current technological interest. Solid polymer electrolytes are non-volatile, non-corrosive materials, which can readily be processed into any shape or size. However, despite possessing the required mechanical properties, they have inherently lower conductivity. Gel-based systems are an attempt to strike a balance between the high conductivity of organic liquid electrolytes and the dimensional stability of a solid polymer.

Rectorite was modified with dodecyl benzyl dimethyl ammonium chloride to form organic-modified rectorite (OREC). OREC was used as a filler additive to modify gel polymer electrolytes (GPEs) and prepare composite gel polymer electrolytes (CPEs) which consisted of polymethyl methacrylate (PMMA) used as a polymer matrix, propylene carbonate (PC), used as a plasticizer, and LiClO4, used as a lithium ion producer. A variety of physical and chemical techniques was used to characterize the CPEs. The interlayer d spacing of OREC was much larger than that of the initial rectorite (2.22 nm). OREC also possesses a fine microscopic structure, and has a hydrophobic surface. Molau and XRD analysis of CPEs indicate that OREC has good compatibility with the components of CPEs and can be dispersed well. The effects of temperature and OREC dose on properties were studied. The temperature dependence of ionic conductivity of CPEs is well fitted by the VTF (Vogel-Tamman-Fulcher) relation. OREC doses of 5 phr gave the greatest ionic conductivity. This amount also greatly increased the plasticizer maintenance levels. Due to the occupancy of free volume space in the polymer matrix of CPEs by OREC, the bulk resistance of the CPEs was lowered and the glass transition temperature (Tg) increased. The sheet structure of OREC is thought to improve the decomposition temperature of CPEs.

The crystal structure of a Te-rich polybasite has been refined by means of X-ray diffraction data collected at room temperature (space group Pm1; R = 0.0505 for 964 observed reflections and 94 parameters; refined formula Ag14.46Cu1.54Sb1.58As0.42S9.67Te1.33). The structure comprises stacking of [(Ag, Cu)6(Sb, As)2(S, Te)7]2–A and [Ag9Cu(S, Te)2(S, Te)2]2+B layer modules in which Sb forms isolated SbS3 pyramids, as occurs typically in sulfosalts, Cu links two S atoms in a linear coordination and Ag occupies sites with coordination ranging from quasi linear to almost tetrahedral. The silver d10 ions are found in the B layer module along two-dimensional diffusion paths and their electron densities evidenced by means of a combination of a Gram-Charlier development of the atomic displacement factors and a split model. The Te-for-S substitution occurs at the same structural sites that Se substitutes for S in selenopolybasite and the Te occupancy at one of these sites is 0.49, thus suggesting the possibility that 'telluropolybasite' could be found in nature.

The concept of using an ion-exchange membrane as an electrolyte separator for polymer electrolyte membrane (PEM) fuel cells was first reported by General Electric in 1955. However, a real breakthrough in PEM fuel cell technology occurred in the mid-1960s after DuPont introduced Nafion®, a perfluorosulfonic acid membrane. Due to their inherent chemical, thermal, and oxidative stability, perfluorosulfonic acid membranes displaced unstable polystyrene sulfonic acid membranes.Today, Nafion® and other related perfluorosulfonic acid membranes are considered to be the state of the art for PEM fuel cell technology. Although perfluorosulfonic acid membrane structures are preferred today, structural improvements are still needed to accommodate the increasing demands of fuel cell systems for specific applications. Higher performance, lower cost, greater durability, better water management, the ability to perform at higher temperatures, and flexibility in operating with a wide range of fuels are some of the challenges that need to be overcome before widespread commercial adoption of the technology can be realized. The present article will highlight the membrane properties relevant to PEM fuel cell systems, the development history of perfluorosulfonic acid membranes, and the current status of R&D activities in PEM technology.

A series of doped Ruddlesden-Popper phases, of general formula Sr3Ti2−xMxO7−δ (M=Al, Ga, Co), were synthesized and their electrical conductivity characterized as a function of temperature and oxygen partial pressure. For fixed-valent dopants, p-type conductivity predominates at p(O2)>10−5 atm, followed by a p(O2)-independent electrolytic regime, and n-type electronic conductivity at very low p(O2). The electrolytic regime exhibits activation energies in the range 1.7-1.8 eV. Doping with transition metals such as Co results in a very significant increase in total conductivity with a p-type conductivity at high p(O2). Furthermore, an apparent ionic regime at intermediate p(O2) is observed, characterized by high conductivity (>10−2 S/cm at 700 °C) and low activation energy (0.7 eV). This interpretation is consistent with iodometric measurements as interpreted by a defect chemical model. Other measurements are in progress to confirm this conclusion.