The Partnership for a New Generation of Vehicles (PNGV) is a national initiative with three goals: First, to significantly improve national competitiveness in manufacturing; second, to implement commercially viable innovations from ongoing research on conventional vehicles, and third, to develop a vehicle to achieve up to three times the fuel efficiency of today's comparable vehicle (ie, the 1994 Chrysler Concorde, Ford Taurus, and Chevrolet Lumina). Note this vehicle will have the equivalent customer purchase price of today's vehicles adjusted for economics, while meeting the customers' needs for quality, performance, and utility. Eight federal agencies are currently contributing to these goals, as well as the three principal US automobile manufacturers, numerous automotive component suppliers, research laboratories, and universities.

Materials research and development is a significant effort within PNGV. The goals in this area include development of lightweight, recyclable materials for structural applications, high strength, long-life, high temperature materials for engine components, improved materials for alternative propulsion and energy storage systems, and cost-effective process technologies and component fabrication methods. Application of advanced materials to automobiles will involve consideration of diverse factors, including weight savings, affordability, recyclability, crashworthiness, repairability, and manufacturability.

Chemical and physical requirements limit the choice of fuel cell electrolytes to strong aqueous acids and alkalis, (pyro)phosphoric acid, carbonate melts, and solid oxides (O= conductors, with rare H+ conductors). The choice of electrolytes and operating temperatures is therefore limited, controlling the choice of other materials (anode catalysts, cathode catalysts, current collectors, and construction materials), which are determined by the properties of the electrolyte, the temperature, the electrode potentials, the gas atmospheres, and thermodynamic and kinetic considerations. The families of state-of-the art and new materials for each class of electrolyte are reviewed. The area of greatest activity is the solid oxide fuel cell (500°C-1000°C). In a review of this length, the extensive list of new solid oxide developments can only be given by way of introduction.

Unsupported different atomic ratios of platinum-ruthenium bulk alloys were prepared. The alloys were characterized by cyclic voltammetry, X-ray diffraction and energy dispersive X-ray spectroscopy. These alloys were also tested as anodes for methanol electro-oxidation in sulfuric acid over a range of temperatures. Ruthenium is inactive for methanol electro-oxidation at 25 °C, but becomes active at higher temperatures. When a comparison is made on the basis of “true” (hydrogen adsorption) surface area, a 30 atomic percent Ru electrocatalyst provides the highest activity for methanol electro-oxidation as measured at either 0.4 or 0.5V vs. RHE at both 25 and 60 °C.

Polycrystalline samples of BaCexGd1-x03 have been prepared with 0.10 < x < 0.20. X-ray powder diffraction indicates the samples contain only one crystalline phase for doping levels < 0.15. Transmission electron microscopy analyses on the 10% doped sample revealed no glassy phases in the intergranular regions. Single crystal fibers were prepared by Laser Heated Pedestal Growth (LHPG) from the polycrystalline samples. Fiber growth was non-conservative thus the single crystal quality was limited. Preliminary conductivity measurements on the polycrystalline samples using AC impedance spectroscopy are compared with literature data.

A study of the thermal stability of the oxygen ion conductor BICUVOX.10 was carried out on small pieces of the polycrystalline material by combined TGA and DTA measurements in air, nitrogen, oxygen and helium. The TGA measurements demonstrated that the weight change was less than 0.1% in the different gases. The DTA curves were practically the same. There is evidence for the occurence of a phase change. TGA curves were also taken on BICUVOX.10, the parent compound Bi4V2O11, and the oxides CuO, B2o2, V2O5. under hydrogen. The comparison of the reduction curves shows that BICUVOX.10 is stable up to about 550C with respect to a direct reduction by molecular hydrogen.

A serious concern with present designs of solid oxide fuel cells is the requirement that “triple-point junctions” exist, sites at which the cathode, electrolyte and oxidizing gas are in simultaneous contact. Only at these junctions can the cathode catalyze the reduction of oxygen into 0= ions and initiate their subsequent transport through the electrolyte. Enhanced ionic conductivity in the cathode material may increase the surface area over which reduction can take place and relax the triple-point constraint. To this end, we have examined the electrical and structural properties of LaCo1-xMgx03-δ materials under various atmospheres. Oxygen ion transport in this and related ABO3 perovskites takes place via oxygen vacancy migration. We have opted to investigate the effect of Mg doping on the transition metal site in an effort to maintain a significant oxygen vacancy concentration in oxidizing atmospheres (as would be encountered during fuel cell operation) and to isolate the effects of A- and B-site doping.

Oxides in the Sr-Fe-Co-O system exhibit both electronic and ionic conductivities. Recently, the Sr-Fe-Co-O system attracted great attention because of its potential to be used for oxygen-permeable membranes that can operate without electrodes or external electrical circuitry. Electronic and ionic conductivities of two compositions of the Sr-Fe-Co-O system, named SFC-1 and SFC-2, have been measured at various temperatures. The electronic transference number is much greater than the ionic transference number in SFC-1, whereas the electronic and ionic transference numbers are very similar in SFC-2. At 800°C, the electronic and ionic conductivities are ≈76 and ≈4 S•cm−1, respectively, for SFC-1; whereas, for SFC-2, the electronic and ionic conductivities are ≈10 and ∼1 S•cm−1, respectively. By performing a local fitting to the equation σ • T = Aexp(-Ea / kT), we found that the oxide ion activation energies are 0.92 and 0.37 eV, respectively, for SFC-1 and SFC-2. The oxygen diffusion coefficient of SFC-2 is ≈ 9 x 10−7cm2/sec at 900°C.

Rare-earth, yttrium, and calcium doped zirconates are the materials of choice for electrolytes in solid oxide fuel cells. The dopant in these materials serves not only to stabilized the cubic phase of zirconia, but also to introduce anion defects that presumably increase the ionic conductivity. In order to understand the relationships between anion defect distribution, thermal history and ionic conductivity, the structural properties of gadolinium zirconate, Gd2Zr207, have been examined via high-temperature x-ray powder diffraction. Gadolinium zirconate is an ideal material for such a structure-property-processing study: it shows ordering of defects at low temperatures, taking on a pyrochlore structure, and disordering at elevated temperature, taking on a defect fluorite structure. Diffraction experiments, performed as functions of time and temperature, confirmed the transition temperature to lie between 1500 and 1550 °C. They also revealed that the transformation takes place most rapidly just below the transition temperature, indicating that the ordering process is kinetically constrained at low temperatures. Moreover, x-ray data collected at room temperature from quenched samples were found to be as useful, if not more so, than those collected in situ at high temperature. The latter are affected by thermal scattering, severely compromising data quality.

The beta alumina structures are known for their high ionic mobility within the lattice. This lead to the development of the Na-β”-alumina polycrystal as solid electolyte in Na/S and Na/NiCl2 batteries. The K-β”-alumina compound is a suitable precursor material to establish proton conducting materials by ion exchange. Tests with single crystal and polycrystalline samples showed the possible application in fuel cells operating between 150 - 250 °C.

One of the main problems to be solved is the correlation between composition and phase evolution of either β- or β”-phase, another problem occuring during sintering is the high vapor pressure of the alkaline oxide. This leads to the decomposition of the highly conductive β”-alumina phase into β-alumina or corundum phases and lowers significantly the ionic conductivity.

We investigated the beta alumina phase evolution using alumina raw materials with different crystallographic structure and grain size. The influence of initial alkaline content and dopant concentration on phase formation and phase stability under sintering conditions has been investigated. A refined phase diagram for Na- and K-beta aluminas will be presented.

In a series of fundamental studies on the cathode active materials for a lithium secondary cell using geometrically well-defined sample electrodes, thin films of spinel LiMn204 on a platinum plate were investigated in this work in an LiCl04/propylene carbonate solution. These pyrolytically prepared films exihibit reversible extraction/insertion behavior for lithium under galvanostatic charge/discharge cycling between 4.3-3.5 V. The chemical diffusion coefficient of lithium in LixMn204 determined by the galvanostatic intermittent titration technique (GITT) was in the order of 10−7-10−10 cm2- s−1 within a spinel single-phase region of 0.6<x<1.0 and increased with increasing x.

In order to develop an air cathode of metal-air batteries, oxygen reduction behavior of gas diffusion-type carbon electrodes loaded with perovskite-type oxides, Lai-xA'xFe03 (A'=Ca, Sr, Ba, 0<x<1.0), was examined in 8 M KOH at 60 °C. Among the oxide catalysts tested, La0.5Sr0.5Fe03 (specific surface area : 21.5 m2.g−1) gave the highest electrode performance. On the basis of electrode reaction kinetics, H2O2 decomposition rates, and temperature programed desorption of oxygen, it was concluded that such a performance was attributable to the active sites of the oxide for the direct 4-electron reduction of oxygen. Moreover, the electrode using Lao.5Sro.5FeO3 was found to be rather stable in a short-term operation for 90 h at 300 mA-cm−2.

Pulsed laser deposition has been used to prepare thin films of several complex metal oxides of significance in secondary batteries from a single stoichiometric target with a substrate temperature of 600°C in the presence of 200 mtorr O2. Films of the candidate bifunctional air electrocatalysts, for metal air batteries, Lao.6Cao.4CoO3, Lao.6Sr0.4CoO3, Lao.6Cao.4MnO3 and Lao.6Sro.4MnO3 were prepared on glassy carbon substrates. Glassy carbon was found to either erode during the ablation process (with the cobaltates) or cause film cracking after deposition because of its extremely low coefficient of thermal expansion.. The use of stainless steel substrates yielded 0.3μm-thick dense films of Lao.6Cao.4CoO3 and Lao.6Cao.4MnO3 which were suitable for electrochemical measurements in concentrated alkaline electrolytes. LiMn2O4 and LiCoO2 films were prepared at thickness' of 0.3μm and 1 5μm The 0.3μm-thick films delivered 176 mC/cm2-μm and 323 mC/cm2-μm for LiMn2O4 and LiCoO2, respectively, in 1M LiClO4/PC.

The formation process of the spinel phase by the melt-impregnation method was extensively investigated by the pore volume distribution measurement. Two kinds of the spinel structure compounds Li1+xMn2O4 optimized in this method were examined as a 4V cathode in a lithium nonaqueous cell. The first one has an initial charge capacity of 135-147 mAh/g and an unstable rechargeability with the characteristic two-step process, and another one delivers a slightly lower capacity of 105-120 mAh/g and ideal rechargeability with the quasi-one step process. These compounds preserve a capacity of more than 110 mAh/g for the first 100 cycles. The capacity fading on cycling of the former spinel only occurs at the second charge plateau in the rage of x<0.4 in LixMn2O4, and is due to the unstable two-phase structure for lithium intercalation coexisting in this region. The excellent rechargeability for the later spinel results from a homogeneous reaction occurring over the entire intercalated region.

A nonaqueous coprecipitation process has been developed to prepare controlled stoichiometry lithium manganese oxalate precipitates. The process involved mixing a methanolic Li-Mn nitrate solution with a methanolic solution containing tetramethylammonium oxalate as the precipitating agent. The resulting oxalates were readily converted to a variety of phase pure lithium manganese oxides at moderate temperatures (≤600°C), where the phase formed was determined by the initial Li/Mn ratio in the starting solution. Metal cation dopants have been incorporated into the oxalate precipitate by dissolving the appropriate metal nitrate in the Li-Mn precursor solution The various starting solutions, oxalate precipitates, and calcined oxides have been extensively characterized using a variety of techniques, including 7Li NMR, TGA/DTA, SEM, and XRD. Results indicate that a strong interaction occurs between Li and Mn in the nitrate solution which carries over into the oxalate phase during precipitation. The morphology and the crystallite size of the oxide powders were shown to be controlled by the morphology of the oxalate precursor and the oxalate calcination temperature, respectively. The results of initial cathode performance tests with respect to dopant type (Al, Ni, Co) and concentration for LiMn2O4 are also reported.

In order to understand and evaluate materials for use in lithium ion rechargeable battery electrodes, we have modeled the crystal structures of various manganese oxide and lithium manganese oxide compounds. We have modeled the MnO2 polymorphs and several spinels with intermediate compositions based on the amount of lithium inserted into the tetrahedral site. Three-dimensional representations of the structures provide a basis for identifying site occupancies, coordinations, manganese valence, order-disorder, and potentially new dopants for enhanced cathode behavior. X-ray diffraction simulations of the crystal structures provide good agreement with observed patterns for synthesized samples. Ionic modeling of these materials consists of an energy minimization approach using Coulombic, repulsive, and van der Waals interactions. Modeling using electronic polarizabilities (shell model) allows a systematic analysis of changes in lattice energy, cell volume, and the relative stability of doped structures using ions such as aluminum, titanium, nickel, and cobalt.

The crystal structures of the undischarged, heat-treated electrolytic manganese dioxide (HEMD) and discharge products are characterized by high spatial resolution convergent beam electron diffraction (CBED). The results are compared with the x-ray diffraction (XRD) patterns characterized by broad, diffuse peaks. The CBED results for HEMD show that the starting cathodic material has the pyrolusite space group, but with a range of c/a ratios. The variability of the lattice parameter from grain to grain is found to coincide with the broadening on the low angle side of the XRD peaks. The CBED patterns of discharge products suggest a reduction range in c/a ratios and the formation of another phase.

Composite powder of spinel LiMn2O4 and polypyrrole has been successfully prepared by injecting pyrrole into an HClO4 aqueous solution containing suspended LiMn2O4 powder which was used as an oxidizing agent for polymerization of pyrrole. The amount of LiMn2O4 in the composite increased with increasing the amount of the suspended oxide powder in the bath, whereas decrease in the amount of ClO4− dopant was observed. Charge-discharge tests of the resulting composite taken in a mixed solvent of propylene carbonate and 1,2-dimethoxyethane (1:1) containing 1 mol dm−3 LiClO4 revealed that polypyrrole of the composite worked well as an active material as well as a conducting network for the incorporated LiMn2O4 powder. Elemental analyses of the charged and discharged composites showed that Li+ cation alone was involved in the charge-discharge reactions of the LiMn2O4/PPy composite.

Recently, there has been considerable interest in advanced materials and processing techniques for practical applications. V2O5 xerogels have generated much attention because they are layered materials that undergo reversible redox intercalation with lithium. The sol-gel process has been used to intercalate V2O5 xerogels with the polymer electrolyte, oxymethylene linked poly(ethylene oxide) - lithium triflate [(a-PEO)n(LiCF3SO3)]. The resulting nanocomposite is a mixed ionic-electronic conductor in which the ionic charge carriers in the polymer electrolyte are in intimate contact with the electronic charge carriers in the V205 xerogel. Variable-temperature electronic conductivity and thermoelectric power measurements have been performed to examine the charge transport properties.

Self-consistent Density Functional calculations have been performed on a variety of planar conjugated Ni-centered macrocycles with a basic tetraazaporphyrinic core and dithiolene groups (PZ) or fused-benzo groups (PC). Theoretical energy diagrams, charge and spin distributions and densities of states have been obtained in order to understand the electronic structure modifications due to peripheral ligand substitution. The substituents role in altering electronic properties and charge distribution of the porphyrazine macrocycles has been used to interpret the observed variations in optical absorption profiles. In the Q-band (∼ 680 nm) region, a single peak is seen for high symmetry (D4h) macrocycles and a double peak for lower symmetry (D2h and C2v) systems. Calculated intensities and band splittings are compared in detail with qualitative molecular orbital models and experiment in the visible and UV regions. Predictions are made for the infrared absorption and semiconducting band gap.