Boichuk T. Mechanism of charge accumulation in hybrid electrochemical systems nanoporous carbon / spinel containing system Li-Mn-Fe-O

In this work the connection between synthesis conditions, structure, morphology and conductivity of Li-Mn-Fe-O systems with different phase composition and their electrochemical characteristics with using as a Faraday hybrid electrode the electrochemical systems are investigated. The effect of temperature activation on the surface state and nanoporous carbon adsorption capacity are established. The main attention is focused on establishing the synthesis conditions and concentrations of the component of iron containing complicated lithium manganese oxide in which formed the structure that can provide the maximum diffusion intensity of lithium in the discharge of the capacitor. It is shown that raising of the pH level of the reaction environment from 4 till 8 leads to the formation of materials with more phases. Electrochemical test of three-electrode cell with the working electrode on the basis of the phase-morphological configurations of Li-Mn-Fe-O are carried and their specific intercalation characteristics are calculated. It is shown that the maximum capacity of specific samples have the highest content of spinel phase in which iron occupies octahedral positions in the crystal lattice. On the base of obtained Faraday electrode active material and activated carbon are formed models of hybrid supercapacitors and carried their testing under different charge/discharge current (0.5C-20C) in sulfate, nitrate and lithium carbonate. Calculated values of the diffusion coefficient of lithium in these conditions are equal to the value of order 10-10-10-9 сm/s and lightly change depending on the discharge speed and electrolyte.