Kaykan L. Physical and chemical properties and processes of lithium intercalation of magnesium-doped lithium-iron spinels

The dissertation for the Candidate Degree in Physics and Mathematics. Specialty 01.04.24 is physics of the colloid systems - Prekarpathion national university of the name of Vasiliy Stefanik, Ivano-Francovsk, 2008. In dissertation on the basis of complex research, executed with the use of x-ray diffractometry, Mossbauer spectroscopy, impedance spectroscopy and mathematical design the analysis of influencing of nonstochiometry, caused a heterovalent substitution is conducted, on processes electrochemical intercalation /deintercalation ions of lithium in a spinels structure. It is shown that a heterovalent substitution magnesium at the different modes of heat treatment causes destruction of super organization in octahedral sub lattice with the simultaneous increase of imperfectness of structure. Electro-neutrality of the system is provided the origin of cation vacancies, that is instrumental in included of lithium in a structure. The conducted complex researches of conductivity and dielectric propertiesshowed the presence of two types of conductivity: electronic and ion. Electronic conductivity will be realized on the basis of hopping mechanism, bivalent iron caused a presence, and takes place mainly on the volumes of corns in octahedral sub lattice of spinels. Diffusive transfer of ions of lithium take place on intergranular scopes and defects (to the vacancies) of points, the amount of which is multiplied with deviation of the system from stochiometry. It is shown that at multiplying the amount of ions of the inculcated magnesium for the systems, exposed to the slow cooling, the value of conductivity on a direct current practically does not change because of participating in the hopping mechanism of stable complexes which appear at substitution. Material which at the use of him as a cathode-active matter of lithium source of current possesses the high values of specific capacity and energy is got. Connection is set between structural, elektrophysikal and power descriptions of cathode material, that enables purposeful modification of structure for the receipt of matter with the properties set in advance.