Kirill Kovnir

Abstract:

The intensively growing Li-ion battery research area places high demands in the establishing of the long- and short-range structure of the electrodes after or during Li intercalation. The low crystallinity of the electrode materials and the weak scattering of the X-rays by Li atoms make these systems crystallographically challenging. To understand the processes occurring in tin pnictides electrodes, we have synthesized ternary Li-Sn-Pn (Pn = P, As) compounds. We hypothesize that the formation of Li1-xSn2+xPn2 is the first stage of Li intercalation into Sn4Pn3. To fully characterize the long-range and local structure, a combination of powder and single crystal X-ray diffraction, neutron and synchrotron X-ray PDF analysis, 7Li NMR and 119Sn Mossbauer spectroscopies, as well as high resolution TEM were applied. An observed local ordering of Sn and Li atoms was further probed by quantum-chemical calculations which indicate strong anisotropy of the properties of Li1-xSn2+xPn2. An investigation of the resistivity and thermal conductivity performed on the large single crystals confirmed anisotropic transport properties of Li1-xSn2+xPn2.