Synthesis and properties of nanoparticles based on С/Fe3O4, С/Fe3-xCrxO4, С/Li0.5Fe1.5CrO4 – anode materials for lithium-ion batteries

Abstract

High charging potential of Fe₃O₄ (1.75 V), its low conductivity and significant changes of volume during charging/discharging are main disadvantages that prevent commercialization of this material as an active constituent of anode for lithium-ion batteries. Various ways for minimization of these drawbacks are discussed. It is suggested that the necessary functional properties of the anode material can be formed directly during the synthesis process. A number of composites, such as С/Fe₃O₄,C/Fe_3-xCr_xO₄, C/Li_0.5Fe_1.5CrO₄, have been obtained using the Pechini method. Modification of the synthesis technique has been developed. Phase composition and morphology of powders were studied by XRD, SEM and EDX analysis. It has been found that the products of synthesis of Fe₃O₄, Fe₂CrO₄, Li_0.5Fe_1.5CrO₄  are characterized by good crystallinity, the average size of powder crystals is 29 (Fe₃O₄), 12 (Fe₂CrO₄) and 18 nm (Li_0.5Fe_1.5CrO₄). Cyclic voltammograms (CV) and galvanostatic charging/discharging curves were obtained within the potential region from 0.05 to 2.0 V (Li⁺/Li), the scan rate was 0.1 mV/s. The C/Fe₃O₄ composite has been found to show high reversible capacitance for the first cycle (~1000 mAh/g) at high C/10 current. At C/10, the C/Fe₂CrO₄ anode shows the capacitance of ~900 mAh/g for the 1st cycle. At the same time, the charging capacitance decreases from 1.8 to 1.1 V. Doping with chromium and lithium leads to decrease of charging potential from ~1.8 V (С/Fe₃O₄) down to 0.9 V (С/Li_0.5Fe_1.5CrO₄). Decrease of grain size down to 10–30 nm and conducting carbon on the grain surface provide better kinetics of the charging/discharging processes. This approach allows us to reach reversible capacitance of ~800 mAh/g for the best material (С/LiFeCrO₄). This characteristic is achieved in the first cycle of charging/discharging at С/10.