катодные материалы

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 complex oxides Li_{1 + x}Ni_{1 / 3}Co_{1 / 3}Mn_{1 / 3}O₂ were obtained by solid state method. The conclusion about influence of lithium concentration on Ni²⁺ and Ni³⁺ ions ratio in Li_{1 + x}Ni_{1 / 3}Co_{1 / 3}Mn_{1 / 3}O₂ is made. Monotonous decrease of g-factor value identified by EPR method testifies the intensification of local exchange interactions with temperature descent.

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).

Review of literature for 25 years on cathode materials for lithium batterias is presented. Activation methods of electrodes are considered; interconnection and interdependence of kinetic, thermodynamic charecteristics and structural transformations in processes of lithium intercalation-deintercalation into electrodes are analysed.

The review generalizes the literary data on physical-chemical and electrochemical properties of lithium-iron phosphate connected with perspectives of LiFePO₄ use as a cathode material for lithium-ion batteries and published up to 2009 inclusive.

The methods of increasing performances of cathode materials based on lithium-manganese spinel are discussed in this review. Next questions are examined: the reasons of LiMn₂O₄ degradation and the basic variants of problem solving including the doping of spinel matrix by metal cations; the substitution of oxygen in system Li–Mn–O by another anions; the creation of protective shell on the surface of particles; the preparation of different composites.

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.