cathode materials

The review summarizes literature data on the thermal decomposition of ferrous oxalate with the formation of Fe, FeO, Fe2O3, Fe3O4, Fe3C, and other products. Historical evolution of views on the ways and mechanisms of oxalate thermolysis is traced. The current state of the art is analyzed from the perspective of FeC2O4·2H2O compound for the synthesis of lithium iron phosphate LiFePO4, which is a promising cathode material for lithium-ion batteries.

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 series of solid phases (mixed lithium-iron-manganese phosphates) of the common formula LiMnyFe1−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.

Doped with tantalum cations a new prospective cathode material for solid oxide fuel cells of lanthanum strontium cobaltite was synthesized. High-temperature oxygen desorption was studied using the quasi-equilibrium oxygen release method, the ranges of oxygen nonstoichiometry were determined, and the values of thermodynamic functions of the system were obtained in the temperature ranges (600–850°C) and oxygen partial pressures (∼10−5– 0.2 atm).

The protective properties of the coating applied to the surface of lithium-manganese spinel (LiMn2O4), using the eutectic composition of Li2O : B2O3 = 47 : 53 (wt.) with the melting point of 650°C, were studied. The content of the eutectic lithium borate varied from 1% to 10%. The electrochemical behavior of the obtained materials in the cathode half-cells of lithium-ion battery was studied at room temperature.

Behavior of PH/P1 lithiated iron phosphate (Phostech Lithium Inc, Canada) used as positive electrode material for Li-ion battery with LiPF₆-based electrolyte was investigated. Specific capacity of the material reached 130 mA·h/g at a rate of 0.5С and 20°C, 105 mA·h/g (1С) and 95 mA·h/g (2.1C). Cell capacity increased by 20% during first 50 cycles and minor capacity fade at a rate of 0.04% per cycle is observed after 300 cycle when cycled at 2C rate versus carbon negative electrode (CMS, PRC).

Various strategies for the synthesis of promising electrode materials for lithium-ion battery (LIB) based on iron(II)-lithium orthosilicate (Li₂FeSiO₄) using widely distributed, environmentally friendly and inexpensive starting materials are considered.

Synthesis of electrode material based on Li₂MnSiO₄/С using widely used, environmentally safe and inexpensive Li, Si and Mn-containing precursors was considered. Mechanochemical activation was used for improving the flow of thesolid-state synthetic process and providing the necessary reactivity to obtain the target product with a high content of the main lithium-accumulating compound.Structural and morphological features of the composite were investigated by X-ray diffraction, laser diffraction granulometry.