Synthesis of new compounds, investigation of the structure, physical and chemical characteristics of intermetallics is the main task for scientists who work in the field of inorganic chemistry and materials science. The main tasks of the dissertation are synthesis, investigation of the structure and electrochemical properties of intermetallic compounds during electrochemical hydrogenation, electrochemical intercalation of Li and Mg and study of the influence of doping components on these processes. Motivation for selection of the intermetallics in the studied systems (two-component, three-component, multi-component) is sufficient volumes of voids and channels for the intercalation of H-, Li-and Mg-atoms into their structure. The interaction of the components in the La–Mg–Sn, Ti–Mg–Sn, Ti–Mg–Sb systems was investigated at 400 ºC for the first time, the isothermal sections of their phase diagrams were constructed in full concentration range, the crystal structures of ternary compounds and solid solutions were determined and refined from X-ray powder and single crystal diffraction data, the homogeneity ranges of the compounds and solid solutions were determined using X-ray diffraction and energy-dispersive X-ray spectroscopy. In most cases the statistical mixture (Mg, Sn) or (Mg, Sb) is formed in limited solid solutions of substitution on the basis of binary compounds that can be described by similar values of the atomic radii of the components.
It was established that binary intermetallisc β-La5Sn3, Y5Sn3, Gd5Sn3, Ti5Sn3, Zr5Sn3 with Mn5Si3-type of structure form solid solutions of inclusion of Mg-atoms into octaherdral voids 2b with the formation of Hf5CuSn3-superstructure at the boundary compositions of the solid solutions.
Y5Sn3 and Gd5Sn3 binary compounds form solid solutions of inclusion and Y5Sn3Mg0.8 and Gd5Sn3Mg0.8 superstructures at their boundary compositions.
The extension of the solid solutions of inclusion Y5Sn3Lix, Gd5Sn3Lix synthesized by the electrochemical method reaches 0.9 Li / f.u., by thermal method reaches 1.0 Li / f.u. The electrode material based on Zr5Sn3 shows a capacity of 160-140 mA•h / g in the Li-ion prototype of the battery and 110-90 mA•h / g in the Mg-ion prototype of battery.
The greatest influence on the corrosion resistance and Coulomb efficiency of the electrochemical processes have doping components s- (Li,Mg) or p- (Sb,Bi) metals. The Tb2Ni15.6Li0.6Mg0.8 alloy exhibits 95.0 % of Coulomb efficiency after 50 cycles and Tb2Ni15.2Li0.6Mg0.6Sb0.6 alloy exhibits ~83 % of Coulomb efficiency after 100 charge-discharge cycles.
The results of the calculation of the electron localization function for 5 phases are used to interpret the chemical bonding in them, e.g. LaMgSn (structure type TiNiSi), LaMgSn2 (own structure type), Zr5Sn3 (structure type Mn5Si3) and Zr5Sn3M, where M = Li, Mg (structure type Hf5CuSn3). The formation of polycation layers based on [La]δ+ and polyanionic layers [Mg,Sn]δ- is observed for the LaMgSn compound as a result of displacement of electronic density to Mg- and Sn-atoms. The density of states at the Fermi level indicates metallic type of conductivity as dominant. Partially covalent bonding was detected in the LaMgSn2 compound and was confirmed by the reducing of interatomic distances between Sn1–Sn1 atoms, d = 2.948 Å (-iCOHP = 1.918 eV). The density of the states at the Fermi level indicates that metallic type of bonding is dominant but covalent interactions are also possible in the structure. The calculation of the electron localization function of the solid solutions Zr5Sn3Mx, M = Li, Mg demonstrates the interaction between atoms of Zr and Li, Mg. The value of the energy of interaction between the lithium and zirconium atoms is
-iCOHP = 0.414 eV, between magnesium and zirconium -iCOHP = 1.62 eV. The higher value of the energy of interaction leads to a slower diffusion of Mg in the electrode material that affects on its electrochemical characteristics.
