Structure and Electrochemical Behavior of Lithium-Manganese Spinels Doped with Chromium and Nickel

A series of compounds with the general formula LiMn_{2 - x - y} Cr _x Ni _y O₄, where x + y = 0.05, 0.5, or 1.0, is synthesized. It is shown that all these compounds are pure-phase spinels with parameter aequal to 0.8193-0.8236 nm. Doping a stoichiometric lithium-manganese spinel simultaneously with chromium and nickel makes the spinel structure stable. The initial specific capacity of a spinel depends on its doping degree. Doping LiMn₂O₄ with chromium and nickel simultaneously at an Mn : Cr : Ni ratio of 195 : 3 : 2 raises the spinel's specific capacity and reduces the cycling degradation. The change in the discharge capacity of LiMn_1.95Cr_0.03Ni_0.02O₄ electrodes cycled at 20, 0, and -14°C is determined.     

Products of lithium interaction with nanostructured oxides SnO2-TiO2 and mechanism of charge-discharge of electrodes in a lithium-ion battery

Products of lithium interaction with thin-film nanostructured SnO₂-TiO₂ (ST) oxides are studied with the aid of x-ray diffraction analysis and Moessbauer spectroscopy on the ¹¹⁹Sn nuclei. Electrochemical properties of a series of the ST electrodes with different concentrations of TiO₂ varied from 0 to 20 mol % are also examined. It is concluded that the specific feature of the charge-discharge mechanism of the ST electrodes is a significant participation of oxygen in reversible reactions during insertion and extraction of lithium as compared with an alloying mechanism of operation of tin-containing anodes. The leading role in this is played by titanium oxide. Remaining stable towards reduction by lithium, it facilitates the holding of the neighboring layers of SnO₂ in a nanodisperse state and in an oxidized state. The effect of a decrease in the capacity degradation in modified TiO₂ electrodes, which is discovered in this work, is attributed to the hampering of the growth of nanocrystallites of β-Sn by interlayers of tin and titanium oxides mentioned above.     

Lithium Intercalation into Graphite during Direct Contact and Anodic Polarization

Values of the diffusion coefficient for lithium in thermoexpanded graphite (TEG) are measured during cathodic intercalation from an aprotic electrolyte and during the TEG plate in contact with metallic lithium without electrolyte. In the course of cathodic intercalation, the diffusion coefficient is measured by method of galvanostatic switching-on curves. During TEG contact with lithium, the variation of x-ray diffraction pattern of TEG with time is recorded. It is established that during TEG contact with lithium the lattice spacing decreases and the characteristic size of TEG particles increases with time until the lithiation is complete and intercalate LiC₆ forms. Values of the diffusion coefficient determined by either method coincide and amount to 10^–10 cm² s^–1.     

High-voltage materials for positive electrodes of lithium ion batteries (review)

The main publications of recent years devoted to functional materials for positive electrodes of rechargeable lithium-ion batteries destined to work at the potential more positive than that of conventional lithiated oxides of cobalt and manganese are considered. The problem of electrolytes stable at these potentials is discussed briefly.     

The Use of Phosphorus in Sodium-Ion Batteries (A Review)

Russian Journal of Electrochemistry - In the recent years, attention is focused on phosphorus as the active material for negative electrodes of sodium-ion rechargeable batteries because it...     

Na3V2(PO4)3/C/Ag nanocomposite materials for Na-ion batteries obtained by the modified Pechini method

Journal of Solid State Electrochemistry - Nanocomposite materials, Na3V2(PO4)3/C and Na3V2(PO4)3/C/Ag, were synthesized by a modified Pechini method. Their properties were characterized with the...     

Synthesis and structure of composite fibers based on silicon and carbon obtained by electrospinning

Composite polymer fibers with a composition of Si-C-O obtained by electrospinning of precursors solution containing polycarbosilane or phenol formaldehyde resins with an admix of organic-silicon compounds were synthesized in order to find efficient new electrode materials for lithium ion batteries. The composition and structure of pyrolized composite fibers were studied by means of X-ray dispersive analysis and X-ray diffraction, Raman spectroscopy, and by AFM and SEM. It was shown that the composite fibers (with a diameter of 0.5–1.5 μm) were nanostructured materials with carbon and silicon-oxy-carbide areas about 2–5 nm in size. A model of the nanostructure of a skeleton for composite fibers synthesized is proposed.     

Irreversible capacity of the amorphous silicon thin-film electrodes

Irreversible processes accompanying the lithium incorporation into amorphous thin-film silicon are investigated. It is shown that the irreversible processes occurred during the cathodic polarization result in the formation of passive film at the silicon surface. The passive film at silicon is close, in its composition, to the passive film at carbonaceous materials. However, unlike the carbonaceous electrodes, no effect of electrolyte composition on the irreversible capacity of the silicon electrodes is observed.     

Study of the Process of Reversible Insertion of Lithium into Nanostructured Materials Based on Germanium

Russian Journal of Electrochemistry - Nanostructured germanium samples prepared by electrochemical deposition from aqueous solution of 0.05 М germanium oxide onto titanium substrate are...