Effect of lithium borate coating on the electrochemical properties of LiCoO2 electrode for lithium-ion batteries

The effect of a protective coating of fused lithium borate, Li3BO3, on the physicochemical and electrochemical characteristics of LiCoO2 has been studied. A cathode material produced by the SCS method using binary organic fuel, glycine and citric acid. The influence of the experiment conditions on the morphology, crystal structure and specific surface of lithium cobaltite was studied. Electrochemical testing of LiCoO2∙nLi3BO3 samples, n = 5 and 7 mass %, has been performed in the cathode Li|Li+-electrolyte|LiCoO2∙nLi3BO3 half-cell using 1M LiPF6 in EC/DMC mixture (1:1) as electrolyte in the 2.7-4.3 V range at normalized discharge current С/10, С/5, С/2. The maximal initial discharge capacity of 185 mAh/g was detected for the samples with 5 mass % Li3BO3. The coulomb efficiency of optimal materials in the 40th cycle was 99.1%.

SYNTHESIS AND ELECTRICAL PROPERTIES OF (Li, Ca)-SUBSTITUTED LANTHANUM COBALTATES

(Li, Ca)-substitute lanthanum cobaltates with composition La1-3xLixCа2xCoO3-δ (0≤x≤0.33) was synthesized by co-precipitation method of hydroxycarbonates. It is determined that the homogeneity region for the system La1-3xLixCа2xCoO3-δ is limited to the composition of x = 0.1. As in the case of Sr- and Ba-containing cobaltates, at x> 0.1, peaks on the diffractograms of the compounds correspond to the phase of lithium cobaltite Li1-yCoO2 with a layered structure. It turned out that the crystallographic parameters of orthorhombic Ca-containing cobaltates increases in comparison with the parameters of the unsubstituted LaCoO3. It is found that with an increase in the mean ion radius of the substituent in the region of homogeneity there is an increase in the average oxidation state of cobalt. The morphological characteristics of complex oxides were studied by using scanning electron microscopy. The grain sizes are in the range from 1 to 2 microns. In the photo along with the small grains you can notice enough large sintered particles in the size of 3 – 4 microns. Also, in SEM-photos, it is possible to detect the impurity phase of lithium cobaltate in the form of grains of the correct hexagonal form, which confirms the results of the X-Ray phase analysis. The 3d-hole (Co4+) formed by the adding of a small amount of Ca2+ and Li+ remains bound to adjacent closely spaced cobalt ions and acts as deep acceptor levels. With increasing substitution degree x, the acceptor complexes interact, forming an σ * conduction band. Due to this, at x≥0.3, the conductivity section of the semiconductor type disappears at the temperature dependence of the electric resistance and the conductivity begins to take a metallic character. On the other hand, contributing to the overall resistance of the system may introduce impurity phases, which is more likely, taking into account the results of the X-Ray phase analysis. It should also be noted that when the concentration of additives increases, the steepness of the curves ρ(Т) decreases.

Pressure-induced abnormal insulating state in triangular layered cobaltite LixCoO2 (x = 0.9)

Lithium cobaltite oxides (LixCoO2) have been serving as an important rechargeable battery material with reversible extraction and insertion of lithium ions.

Impact of Lithium Composition on Structural, Electronic and Optical Properties of Lithium Cobaltite Prepared by Solid-state Reaction

The lithium-cobalt oxide LixCoO2 is a promising candidate as highly active cathode material of lithium ion rechargeable batteries. The crystalline-layered lithium cobaltite has attracted increased attention due to recent discoveries of some extraordinary properties such as unconventional transport and magnetic properties. Due to layered crystal structure, Li contents (x) in LixCoO2 might play an important role on its interesting properties. LiCoO2 crystalline cathode material was prepared by using solid-state reaction synthesis, and then LixCoO2 (x<1) has been synthesized by deintercalation of produced single-phase powders. Structure and morphology of the synthesized powders were investigated by X-ray diffraction (XRD), Infrared spectroscopy, Impedance analyzer etc. The influence of lithium composition (x) on structural, electronic and optical properties of lithium cobaltite was studied. Temperature dependent electrical resistivity was measured using four-probe technique. While LixCoO2 with x = 0.9 is a semiconductor, the highly Li-deficient phase (0.75 ? x ? 0.5) exhibits metallic conductivity. The ionic conductivity of LixCoO2 (x = 0.5 – 1.15) was measured using impedance spectroscopy and maximum conductivity of Li0.5CoO2 was found to be 6.5×10-6 S/cm at 273 K. The properties that are important for applications, such as ionic conductivity, charge capacity, and optical absorption are observed to increase with Li deficiency. Keywords: Calcination; Characterization; Inorganic compounds; Solid-State reaction; X-ray diffraction. © 2014 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.doi: http://dx.doi.org/10.3329/jsr.v6i2.17900 J. Sci. Res. 6 (2), 217-231 (2014)

Performance Study of Nickel Covered by Lithium Cobaltite Cathode for Molten Carbonate Fuel Cells: A Comparison in Li/K and Li/Na Carbonate Melts

The slow dissolution of the lithiated NiO cathode represents one of the main causes of performance degradation in molten carbonate fuel cells. Two main approaches are usually investigated to overcome this problem: modifying the electrolyte composition and studying innovative cathode. In this work, the production of an alternative material as well as a study in different carbonate melt mixtures (62/38 mol % Li/K and 52/48 mol % Li/Na) of this innovative cathode have been taken into account. The issue of cathode surface protection was attained covering a nickel substrate with a thin layer of lithium cobaltite doped with magnesium (LiMg0.05Co0.95O2); a sol impregnation technique was used to deposit gel precursors on the porous surface of the substrate. Chemical analysis, electrical conductivity measurements and scanning electron microscopy were used to characterize the cathodes before and after in-cell tests. The cathodic performance was tested in two 3 cm2 area cells assembled with the following electrolyte compositions: Li/K=62/38 mol % and Li/Na=52/48 mol % in order to investigate the cathode behavior in different carbonate melt environments. Polarization curves and electrochemical impedance spectroscopy measurements were carried out during cell lifetime (about 850 h). Finally, different compositions of the cathodic gas were used to study the influence of oxygen and carbon dioxide on the electrode kinetics.

Synthesis of Lithium Cobaltite (LiCoO2) Prepared by Solid State and Sol-gel Acryl Amide Polymerization Reaction.

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009