Electrochemical Properties of LiCo0.4Ni0.6O2 and its Performances in Rechargeable Lithium Batteries

Intercalation cathode materials belonging to the 4-volt class electrodes, lithiated cobalt oxide LiCoO2 and lithiated nickel cobalt oxide LiCo0.4Ni0.6O2, were synthesized by sol-gel technique. The structural characteristics of the compounds were studied using XRD, FTIR and DSC. The compounds were used as cathode materials for assembling rechargeable lithium-batteries and their electrochemical performances were studied. The potentiostat and galvanostat techniques were used to determine the electrochemical characteristics. The irreversible capacity loss of LiCoO2 during the first charge-discharge is about 20 % and for LiCo0.4Ni0.6O2 is about 90 % for two different current rates of 5 and 10 A kg-1. The overall electrochemical capacity of LiCo0.4Ni0.6O2 has been drastically reduced due to the s-block or p-block metal substitution. Also the un-reacted materials remained as impurities gave a very poor cycleability. However more stable charge-discharge performances have been observed for LiCoO2 at different current rates. Differences and similarities between these two cathode materials in batteries are also discussed. The Li-ion batteries were assembled using the sol-gel synthesized cathode materials, natural untreated vein graphite of Sri Lanka as the anode material and 1 M LiPF6 in EC/DMC as liquid electrolyte, and their performances were tested. 1

Surface modification of natural vein graphite for the anode application in Li-ion rechargeable batteries

Natural vein graphite with high purity and crystallinity is seldom used as anode material in lithium-ion rechargeable batteries (LIB) due to impurities and inherent surface structure. This study focuses on improving the surface properties of purified natural vein graphite surface by employing mild chemical oxidation. Needle-platy graphite sample with initial average carbon percentage of 99.83% was improved to 99.98% after treatment with 5 vol.% HCl. Surface modification of purified graphite was done by chemical oxidation with (NH4)(2)S2O8 and HNO3. Fourier-transform infrared spectra of graphite after chemical indicating surface oxidation of graphite surface. X-ray diffraction and scanning electron microscopic studies show the improvement of graphite structure without modification of crystalline structure. Electrochemical performance of lithium-ion cell assembled with developed anode material shows noticeable improvement of the reversible capacity and coulombic efficiency in the first cycle and cycling behavior after surface modification

Progressive censoring methodology: an appraisal

Progressive censoring, Order statistics, Life-testing experiment, Bounds, Generalized order statistics, Characterizations, Markov property, Likelihood inference, Reliability sampling plans, Goodness-of-fit tests, Prediction, Competing risks, Step-stress test, Hybrid censoring, Permanents, Outliers, Robustness, 62G30, 62E99, 62F10, 62N01, 62N05,