Lithium-containing thiophosphates represent promising ceramic electrolytes for all-solid-state batteries. The underlying principles that cause high Li + diffusivity are, however, still incompletely understood. Here, β-Li 3 PS 4 served as a model compound to test the recently presented hypothesis that a channel-like Li + diffusion pathway influences ionic transport in its 3D network of the LiS 4 , LiS 6 , and PS 4 polyhedra. We looked at the temperature dependence of diffusion-induced 7 Li nuclear spin−lattice relaxation rates to check whether they reveal any diagnostic differences as compared to the nuclear spin response frequently found for isotropic (3D) diffusion. Indeed, distinct anomalies show up that can be understood if we consider the influence of lowdimensional diffusion. Hence, even for isotropic materials without clearly recognizable 1D or 2D diffusion pathways, such as layered or channel-structured materials, structurally hidden dimensionality effects might help explain high ionic conductivities and refine the design principles currently discussed. In the present case, such rapid pathways assist the ions to move through the crystal structure.
Ceramics with nm-sized dimensions are widely used in various applications such as batteries, fuel cells or sensors. Their oftentimes superior electrochemical properties as well as their capabilities to easily conduct ions are, however, not completely understood. Depending on the method chosen to prepare the materials, nanostructured ceramics may be equipped with a large area fraction of interfacial regions that exhibit structural disorder. Elucidating the relationship between microscopic disorder and ion dynamics as well as electrochemical performance is necessary to develop new functionalized materials. Here, we highlight some of the very recent studies on ion transport and electrochemical properties of nanostructured ceramics. Emphasis is put on TiO
The monoclinic polymorph of Li 2 TiO 3 (β-form) is known to be a relatively poor Li ion conductor. Up to now, no information is available on how the ion transport properties change when going from well-ordered crystalline Li 2 TiO 3 to a structurally disordered form with the same chemical composition. Here, we used high-energy ball milling to prepare nanocrystalline, defect-rich Li 2 TiO 3 ; ion dynamics have been studied via impedance spectroscopy. It turned out that ball milling offers the possibility to enhance long-range ion transport in the oxide by approximately 3 orders of magnitude. Its effect on the oxide ceramic is two-fold: besides the introduction of a large number of defects, the originally μm-sized crystallites are decreased to crystallites with a mean diameter of less than 50 nm. This process is accompanied by a mechanically induced phase transformation towards the α-form of Li 2 TiO 3 ; besides that, a significant amount of amorphous materials is produced during milling. Structural disorder in nanocrystalline as well as amorphous Li 2 TiO 3 is anticipated to play the capital role in governing Li ion dynamics of the sample finally obtained.
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