Ion Conduction / Self-Diffusion / Model / Materials ScienceUnderstanding the mechanisms of translational and localised ionic movements in disordered materials has seen intense activity spanning several decades. This article attempts to convey a concise overview of our contribution to this field over the period from 2005 to 2010 and to place it in its broad context.

Different nearly constant loss phenomena are investigated in borate glasses with compositions xNa(2)O.(1-x)B(2)O(3), for 0 < or =x< or = 0.3. The ionic conductivities caused by these effects are studied in wide ranges of temperature and frequency, spanning 4.3 K to 573 K and 100 mHz to 1 MHz, respectively. In a first step, we show how to identify the nearly constant loss (NCL) in 0.3Na(2)O.0.7B(2)O(3) glass. In the procedure, the scaling property of the conductivity caused by ordinary hopping is used to remove this component from the total conductivity as measured as a function of temperature at fixed frequency. The resulting NCL component is seen to be proportional to frequency and to display no temperature dependence. In a second step, a broad-band relaxation process is shown to exist in amorphous boron oxide and in sodium borate glasses with x< or = 0.1. It is most probably due to the presence of traces of water, with hydrogen ions behaving as reorienting and interacting local dipoles. In a third step, we propose a simple formal treatment of the NCL phenomenon, tracing it back to a large number of interacting ions, each of them moving locally. The key aspect is a "see-saw-type" time dependence of their individual single-particle double-well potentials, which is due to their Coulomb interactions. The individual ion does, therefore, not require thermal activation and is thus kept in motion even at cryogenic temperatures.

At sufficiently low temperatures, disordered ionic materials display the well-known Nearly Constant Loss (NCL) effect, with ionic conductivities becoming approximately proportional to frequency and virtually independent of temperature. There is a broad consensus that the effect is a collective phenomenon, with many interacting ions participating, each of them performing some non-vibrational motion that remains strictly localised. The underlying many-particle dynamics have been analysed in Monte Carlo simulations and also by straightforward modelling. Both kinds of treatment predict that, with decreasing frequency, a frequency squared behaviour should become visible. Here, we report on the experimental detection of the squared to linear crossover in an NCL component of conductivity spectra of sodium borate glasses, xNa(2)O·(1 -x) B(2)O(3) with x = 0.05 and x = 0.1, at temperatures below 100 K. From the composition dependence of the effect it is obvious that it is caused by the sodium ions. We demonstrate that this behaviour corresponds to an almost trivial property of the mean square displacement of the confined, but locally mobile ions, which approaches a temperature-independent long-time value, reflecting the finite size of the accessible volume. In the log-log plot of measured conductivity versus frequency, the transition from slope two to slope one is rather gradual, reflecting the existence of different local neighbourhoods of the sodium ions.

The ever-increasing interest in sustainable mobility is driving the development of innovative batteries with increased energy densities relative to currently commercialized lithium-ion batteries. All-solid-state batteries using 5 V-class positive electrodes are one of those batteries due to their larger volumetric energy density and their superior durability. However, their power density tends to be limited by the large charge transfer resistance at their electrolyte/5 V-electrode interfaces; one explanation for this is the development of significant Li + deficient layers at the interface. Here we propose a new interlayer material that would effectively resolve the Li + deficient layers. The partially-crystallized Li 56 Nb 22 Ta 22 oxide was identified using the molecular beam epitaxy (MBE) based high-throughput physical vapor deposition (HT-PVD) approach. Its higher ionic conductivity of 4.2 μS cm −1 and higher permittivity of 165 when measured at 254 kHz, relative to those of conventional LiNbO 3 interlayer (1.8 μS cm −1 and 95, respectively) will be effective for fast charge transfer reactions at the electrolyte /cathode interfaces in 5 V-class all-solid-state batteries. Rapid economic growth and associated worldwide motorization have accelerated the consumption of fossil fuels. In order to tackle the issue, automobile industries are attempting to reduce CO 2 emissions by developing environmentally-friendly vehicles such as hybrid vehicles (HVs), plug-in hybrid vehicles (PHVs), electric vehicles (EVs) and fuel-cell hybrid vehicles (FCHVs).Since EVs driving ranges are mainly restricted by the energy density of rechargeable batteries loaded on them, it is critical for future EVs to incorporate innovative batteries with higher energy densities than state-of-the-art lithium-ion batteries. Figure 1 illustrates a Ragone plot presented by Iba and Yada at the 17 th International Meeting on Lithium Batteries (IMLB 2014), 1 where innovative batteries are compared with traditional batteries in terms of energy and power densities. The Ragone plot indicates that Toyota has been developing all-solidstate batteries and lithium-air batteries aiming for their practical use in the 2020s and 2030s respectively. Toyota has so far manufactured small prototype cells of all-solid-state batteries and Li-air batteries with energy densities of 400 Wh/L and 1000 Wh/L, respectively, and also produced a prototype electric kickboard that can carry a person using power provided by all-solid-state batteries. One of the issues in 5 V-class all-solid-state batteries is associated with large charge transfer resistances at their electrolyte/5 V-electrode interfaces. The large resistance derives from a number of factors such as small geometric interfacial area, impurity phase formation, 8 distortion of metal-oxygen bonding in the vicinity of the interface, 9 and so on. The large resistance may also be explained by Li + deficient * Electrochemical Society Active Member. z E-mail: Chihiro.Yada@toyota-europe.com layers, or space charge layers, 10 ...