摘要: In this chapter, the modeling techniques of the thermodynamic and diffusion properties based on density functional theory in ionic materials, specifically oxide ceramic materials or ionic conductor materials are reviewed. Section 1 is the introduction of this book chapter. Section 2 is devoted to introduce the modeling methods of first-principles finite temperature thermodynamics, including quasi-harmonic phonon calculations and the Debye model. In the phonon model, the frozen phonon method, the linear response method, and the newly developed mixed-space method to model ionic polar materials are discussed. Section 3 introduces the general atomic diffusion theory, first-principles transition state calculations (double-well approach), and ab initio molecular dynamics simulations of the diffusion coefficients in ionic materials. Section 4 discusses some of the recent works of first-principles prediction of the thermodynamic and diffusion properties of ionic materials from our group and in the literature, with a focus on oxides for energy applications. Section 5 summarizes this book chapter.
摘要: Oxides dissolve protons that become mobile at high temperatures resulting in proton conduction. Materials possessing this functional property find applications in environmentally friendly energy technologies and will as such become essential components in future sustainable energy production. This contribution presents the fundamentals and functionalities of oxides showing high temperature proton conduction. The working principles are addressed with basis in the thermodynamics of proton dissolution and the mechanisms for proton mobility. Effects of grain boundaries and trapping on proton transport are outlined. Several oxide families possessing proton conduction at high temperatures are reviewed. Finally some of the potential applications for these materials and the status of the technologies are briefly discussed with bases in the benchmark oxides and assemblies.
摘要: Aluminium is a key element in geological and man-made materials which has only one stable isotope and no radionuclides with half-life times suitable for standard experimental diffusion studies. Here we report on our method using the radioisotope 26Al (t1/2 = 7.4×105 a) as a quasi-stable tracer for aluminium in combination with SIMS depth profiling. First, our data for the aluminium bulk diffusivity in a-alumina are discussed jointly with published oxygen bulk diffusion coefficients. They clearly show that the relation DAl>>D0 is valid in the temperature range 1200 °C ≤ T ≤ 1800 °C. In an analogous manner, the two rare stable isotopes 18O and 30Si are used together with 26Al in diffusion studies of generic examples of materials which either consist of aluminium, silicon and oxygen only, or where these three elements are key constituents of the structure. For the crystalline aluminium silicate mullite our diffusivity data for aluminium, oxygen and silicon are used to explain the kinetics of the solid state formation reaction of mullite and the segregation kinetics of alumina from mullite. Finally, the diffusivities of oxygen and aluminium in model aluminosilicate glasses are presented as a function of temperature for different Al3+/Na+ ratios. For the aluminium silicate mullite and for the aluminosilicate glasses the relation D0>DAl>DSi is valid regardless of the exact composition. For the glass system the activation enthalpies of aluminium and oxygen diffusion decrease with decreasing Al3+/Na+ ratio.
摘要: This article presents a review on Li diffusion in lithium containing metal oxide compounds. The focus is on the investigation of solid state diffusion by tracer methods. In contrast to experiments with Nuclear Magnetic Resonance Spectroscopy and Impedance Spectroscopy, only a limited number of tracer based experiments can be found in the literature. Possible reasons are discussed. Measurements on the system Li-Nb-O are given in detail, while additional results on other Li-M-O (M = Al, Si, Mn, Ti) systems are also presented. The review is completed by a brief survey of the experimental methods in use.
摘要: Replacing traditional liquid electrolytes by polymers will significantly improve electrical energy storage technologies. However, the ion transport mechanism in polymers has been one of the main barriers to further improvement in Li-ion batteries and is still not completely clarified. In an effort to gain a better understanding of the conduction phenomena in electrolytes, a comprehensive survey of all transport mechanism including solvation, segmental motion and hopping, is presented here. Included are a survey of the fundamentals of diffusion and conductivity in polymer electrolytes; recent developments in Li salts; and a detailed discussion about ion transport mechanism with representative references.