Lithium electrochemical systems

A study on LiMnyFe1-yPO4 as a cathode material for lithium-ion batteries

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. 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 LiMn0.05Fe0.95PO4.

Lithium-ion battery capacity estimation at the real-time

At this paper algorithms of accessible and full capacity estimation are presented. The model discrete parameter interpolation, based on spline function is shown. Presented algorithms are analyzed for use in real-time applications.

Nanostructured TiO2–TiOF2 composite as anode material for Li-ion battery

TiO2–TiOF2 composite has been synthesized in plasma by the unique method of pulsed high-voltage discharge due to the destruction of Ti electrodes and polytetrafluoroethylene wire. TiO2–TiOF2 features have been investigated by scanning electron microscopy, X-ray diffraction, infrared spectroscopy, energy-dispersive X-ray analysis, Raman spectroscopy, and X-ray photoelectron spectroscopy. It has been shown that composite with a porous surface morphology includes the nanocrystallites of sizes ranging from 40 to 200 nm. The average diameter of the pore is 3–5 nm. Electrochemical characterization of the nanostructured porous TiO2–TiOF2 composite was carried out in view of its application as an anode-active material for Li-ion battery. The initial high specific capacity of the composite is equal up to 1370 mA·h g–1 at a rate of 20 mA g–1. It is higher (due to the TiO2 presence) in comparison with up-to-date TiOF2 anode materials. Galvanostatic charge–discharge cycling of the Li/TiO2–TiOF2 cell in the range of 3.0–0.005 V yields 205 mA·h g–1 after 20 cycles.

Modern power sources for cardioelectronics

Cell with electrochemical system «lithium – fluorinated carbon» intended for electrical pacemakers have been developed. Their significant advantages over traditional lithium – iodine cells for pacemakers are shown. Discharges characteristics, a shelf-life, and reliability, as well as an effect of various additives in fluorinated carbon cathode on discharge characteristics have been studied.

Effect of feedstock on the characteristics of cathodes fluorinated carbon

The electrode behavior of various fluorinated graphite materials and different conductive additives in various electrolytes are studied. Fluorocarbon materials based on graphite fibers are shown to have the best discharge characteristics. The advantage of thin cathodes based on fluorinated nanomaterials with a solid polymer electrolyte in comparison with the similar electrodes with traditional fluorocarbon active material is demonstrated. The use of fluorinated nanomaterials results in increased discharge characteristics of the cells.

The kinetic of lithium ions intercalation in the anatase synthesized by sol-gel methods

Possibility of ultradispersed TiO22 (anatase modification) using as the base of the lithium power sources cathode material obtained by chloride-acid hydrolysis of titanium tetrachloride has been studied. The researches of Li+ ions electrochemical intercalation kinetics and phasic model of the process was suggested. The cathode material phase composition changes during discharge were fixed and interpreted.

Electrodes of lithium-ion batteries: some simple method for diagnostics of degradation at cycling

It is shown that an examination of reduced galvanostatic charge-discharge curves allows making preliminary conclusion on degradation mechanism upon cycling. If such degradation is due to loss of active material all normalized curves coincide. In the case of insulating films building up normalized curves are shifted along potential axis. Various structure changes result in qualitative change of curves shape.

Improvement of electrochemical behavior of amorphous silicon via preliminary heat treatment

Thin-film amorphous silicon electrodes, subjected to various pretreatment have been tested in galvanostatic and potenciodynamic modes. Preliminary heat treatment of silicon electrodes in nitrogen atmosphere was established to lead to some decrease in discharge capacity and insignificant decrease in degradation upon cycling. Preliminary annealing of silicon electrodes in vacuum at 480°C results in increase of discharge capacity and some decrease of degradation upon cycling. Silicon electrodes with thickness about 1 micron annealed in vacuum have discharge capacity about 1200 mA·h/g.

Development of high-capacity lithium-ion battery asstmblies

This paper describes the state-of-the-art and areas of application for lithium-ion batteries. Their competitiveness in comparison with conventional alkaline and acid based batteries is shown. System approaches and circuit configurations used for designing high-capacity energy storage batteries with microprocessor battery managemmt systems (BMS) are considered, including the main functions of BMS. Based on the given examples, the modular design approach of batteries with 2-3 levels of control has been proved. A comparative analysis of different hardware schemes for voltage leveling in storage batteries is carried out.

The earth rare metall nature influence on electrochemical processes on MnO2-electrode in aprotic organic solutions

The influence of rare earth elements nature on Mn02 electrode electrochemical modification process in solutions of their salts in aprolic organic solvents was investigated. It was proved that periodicity of properties inherent in the lanthanides lakes place in the products of their interactions with MnO, and it is connected with characteristics of their structure. It was shown that the choice of metal as a modifying agent may be decisive in choosing the conditions of synthesis of cathode materials.