твёрдофазный синтез

The paper presents the results of the study of phase composition and electrochemical performance of lithium-manganese oxide spinel with excess lithium of nominal composition of Li_1 + xMn₂O₄ obtained by solid-phase method. It was established that samples with x = 0.1 and 0.2 were composite materials with LiMn₂O₄ being the basic phase and Li₂MnO₃ being the impurity (3 and 7 mas.%, respectively) also comprising trace amounts of MnO₂.

The methods for the synthesis of lithium iron phosphate LiFePO₄ with olivine structure have been developed. New materials based on lithium iron phosphate, including doped with metals, the «LiFePO₄ + carbon» composites obtained by pyrolysis of organic compounds have been synthesized. Crystallographic characterization of the synthesized materials was carried out; their electrochemical characteristics of the extraction and intercalation of lithium have been identified. A correlation between the crystallographic and electrochemical characteristics of the materials was found. It was confirmed that an effective way to improve the electrical conductivity of LiFePO₄ is to create a carbon shell of the products of pyrolysis of organic compounds on the material's particles surface. A correlation of electrical conductivity and temperature of synthesis of the material was determined. The sequence of chemical interaction between precursors for the synthesis of LiFePO₄ is defined; the mechanism of solid-phase interaction is described.

A series of solid phases (mixed lithium-iron-manganese phosphates) of the common formula LiMn_yFe_1-yPO₄ (0 ≤ y ≤ 1) with a carbon coating on the particle surface was synthesized by mechanochemical activation with carbothermal reduction. The synthesized mixed phosphates were examined as promising cathode materials for lithium-ion batteries. The positive effect of replacement of a rather small fraction of iron by manganese is shown, which improves the electrochemical performance at the rates C/10–10C. The highest discharging capacity (above 160 mA·h/g at the C/10 rate, about 100 mA·h/g at the 10C rate) and cycling stability (the capacity decrease rate less than 0.05 mA·h/g per cycle at the 10 C rate) were established for the weakly doped cathode material LiMn_0.05Fe_0.95PO₄.