In situ X-ray diffraction was performed to study the formation of the α-Sn structure in nanocrystalline Sn-based electrodes.

The formation of the α-Sn phase in Sn/SnOx core/shell nanoparticles after lithium insertion and extraction was investigated for the first time and a critical size for the transformation was determined.

Tin is able to lithiate and delithiate reversibly with a high theoretical specific capacity, which makes it a promising candidate to supersede graphite as the state-of-the-art negative electrode material in lithium ion battery technology. Nevertheless, it still suffers from poor cycling stability and high irreversible capacities. In this contribution, we show the synthesis of three different nano-sized core/shell-type particles with crystalline tin cores and different amorphous surface shells consisting of SnOx and organic polymers. The spherical size and the surface shell can be tailored by adjusting the synthesis temperature and the polymer reagents in the synthesis, respectively. We determine the influence of the surface modifications with respect to the electrochemical performance and characterize the morphology, structure, and thermal properties of the nano-sized tin particles by means of high-resolution transmission electron microscopy, x-ray diffraction, and thermogravimetric analysis. The electrochemical performance is investigated by constant current charge/discharge cycling as well as cyclic voltammetry.

The lattice constants of metallic nanoparticles shrink with respect to that of a bulk material. This behavior affects the properties of nanoscaled crystallites and can influence their application potential. In this work, we investigate the size-dependent lattice parameters of core/ shell Sn/SnO x nanoparticles, synthesized via a simple chemical reduction method. Therein, the use of appropriate surface ligands, reaction temperature, and reaction time allows us to tune the mean particle size from 6 to 104 nm. X-ray powder diffraction revealed that the ß-Sn reflections shift toward higher angles for smaller particles, showing a size-dependence of the lattice constants. The change in the lattice constants varies, depending on the direction, and can be described as an inverse function of the diameter of the crystallites. The different degree of deformation can be explained by the direction dependency of the bulk modulus K and the interface energy γ of the monocrystalline tin nanoparticles.