The electrochemical properties of materials derived from NaTi 3 O 6 (OH)$2H 2 O have been investigated for the first time. The parent compound has a corrugated layered structure consisting of {Ti 6 O 14 } 4À units with hydrated sodium cations and protons in the interlayer spaces. Upon heating to 600 C, water is removed irreversibly, the interlayer distances become smaller, and connecting bonds between the octahedral layers form. It was found that this material can reversibly intercalate both lithium and sodium. The initial specific discharge capacities, as measured in half-cells, varied with the state of hydration and the nature of the counter electrode (Na or Li). The electrochemical potential showed a non-linear sloping dependence with degree of intercalation, indicative of a solid-solution mechanism of intercalation. The process was centered at a low average potential of about 0.3 V vs. Na or Li, the lowest ever reported for titanatebased Li hosts. The higher density and potential for higher rate capability of this compound, in comparison to carbonaceous materials with similar voltage and reversible capacities, make a compelling case for its development as an anode material, for both lithium and sodium ion batteries. Broader contextDespite the technological success of lithium ion batteries in small electronics applications, efforts continue to be directed at enabling them to break through the existing barriers to widespread adoption in applications such as electric drive vehicles. Recent attention has been diverted to sodium ion systems due to the attractive cost and abundance features of the raw materials. Finding and designing materials capable of reversibly storing large amounts of electrochemical energy is at the core of technological breakthroughs. While systems based on alloy or conversion reactions lead to huge storage capacities, materials that react with an alkali metal through intercalation reactions are ultimately favored because they require smaller atomic scale rearrangements in comparison, resulting in more durable devices. At the negative electrode, emphasis has been placed on carbonaceous materials. Ti-containing oxides are denser and have higher rate capability than graphite or hard carbons, but they typically show lower capacities and higher voltages of operation, both of which lower energy density. Herein we present results on a new layered titanate that is capable of reversibly intercalating both Li and Na at very low voltages and shows the potential for large storage capacities. Its properties provide insight into the frontiers of electrochemical ion intercalation as it applies to energy storage technologies.

Conductivity measurements were performed on microcrystalline and nanocrystalline ceria (undoped and doped) in dry as well as wet atmosphere. Below 200-250 °C, the nanocrystalline samples exhibit an enhanced total conductivity under wet conditions, which increases with decreasing temperature. In addition, thermo-gravimetric analysis revealed a strong water uptake below 200 °C. DC-polarization measurements confirm the ionic character of conductivity in the nanocrystalline samples at low temperatures. The role of both grain boundaries and residual porosity on the enhanced conductivity below 200 °C is discussed.

Yttrium-doped barium zirconate (BZY) is the most promising candidate for proton-conducting ceramics and has been extensively studied in recent years. The detailed features of the crystal structure, both short-range and long-range, as well as the crystal chemistry driving the doping process, are largely unknown. We use very high resolution X-ray diffraction (HR-XRD) to resolve the crystal structure, which is very slightly tetragonally distorted in BZY, while the local environment around Zr4+ and Y3+ is probed with extended X-ray absorption fine structure (EXAFS), and the symmetry and vibrations are investigated by using Raman spectroscopy. It is found that barium zirconate shows some degree of local deviation from the cubic arystotype even if undoped, which upon substitution by the perceptibly larger Y3+, playing the role of a rigid inclusion, is further increased. This distortion is one limiting factor concerning the Y3+ solubility. The effects are correlated to the proton conduction properties of BZY

The electrical conductivity of ceria thin fi lms (epitaxial as well as dense and porous nanocrystalline) is investigated in dry and wet atmosphere at temperatures below 500 ° C. For the epitaxial and the fully dense nanocrystalline samples, no signifi cant differences can be observed between dry and wet conditions. In marked contrast, the nanocrystalline porous fi lms obtained via spin coating exhibit a considerable enhancement of the protonic conductivity below 300 ° C in wet atmosphere. This outcome reveals that the residual open mesoporosity plays the key role for the enhancement of the proton transport at low temperatures and not the high density of grain boundaries. The quantitative analysis of the various pathways, along which the proton transport can take place, indicates that the observed proton conduction can arise not only from bulk water adsorbed in the open pores but also from the space charge zones on the water side of the water/oxide interface.

In a humidified atmosphere, acceptor-doped BaZrO3 perovskites exhibit a high bulk proton conductivity, but the total conductivity is severely decreased by the blocking character of the grain boundaries. In our study, we compare rapidly densified Y- and Sc-doped BaZrO3 ceramics (Spark Plasma Sintering, 5 min at 1600 °C) with samples after extended annealing at high temperature (20 h at 1700 °C). Under these conditions, the dopants become mobile, resulting in a strong grain boundary conductivity enhancement, although no grain growth occurs. This increase is accompanied by a significant increase in dopant concentration in the grain boundary region, as evidenced by transmission electron microscopy. The correlation between the electrical properties of grain boundaries and their chemical composition is consistent with the interpretation in terms of the space charge model with a positive excess charge in the grain boundary core and adjacent proton depletion zones.