No abstract

A LiNi0.8Co0.15Al0.05O2 (LNCAO/C) active material composite cathode was coated with carbon. The conductive carbon coating was obtained by addition of surfactant during synthesis. The addition of surfactant led to the formation of an amorphous carbon coating layer on the pristine LNCAO surface. The layer of carbon coating was clearly detected by FE-TEM analysis. In electrochemical performance, although the LNCAO/C showed similar capacity at low C-rate conditions, the rate capability was improved by the form of the carbon coating at high current discharge state. After 40 cycles of charge-discharge processes, the capacity retention of LNCAO/C was better than that of LNCAO. The carbon coating is effectively protected the surface structure of the pristine LNCAO during Li insertion-extraction.

Silica-manganese oxides with a core-shell structure were synthesized via precipitation of manganese oxides on the SiO 2 core while varying the concentration of a precipitation agent. Elemental analysis, crystalline property investigation, and morphology observations using low-and high-resolution electron microscopes were applied to the synthesized silica-manganese oxides with the core-shell structure. As the concentration of the precipitating agent increased, the manganese oxide shells around the SiO 2 core sequentially appeared as Mn 3 O 4 particles, Mn 2 O 3 +Mn 3 O 4 thin layers, and α-MnO 2 urchin-like phases. The prepared samples were assembled as electrodes in a supercapacitor with 0.1 M Na 2 SO 4 electrolyte, and their electrochemical properties were examined using cyclic voltammetry and charge-discharge cycling. The maximum specific capacitance obtained was 197 F g −1 for the SiO 2 -MnO 2 electrode due to the higher electronic conductivity of the MnO 2 shell compared to those of the Mn 2 O 3 and Mn 3 O 4 phases.

The Mn0.720Ni0.175Co0.105(OH)2 precursor was co-precipitated by the Couette-Taylor reactor. The 0.3Li2MnO3 x 0.7LiMn0.60Ni0.25Co0.15O2 of the high capacity cathode material for a Li-ion battery was synthesized according to the amount of lithium excess (5-20 mol.%). X-ray diffraction (XRD) and field emission-scanning electron microscopy (FE-SEM) were used to characterize the 0.3Li2MnO3 x 0.7Li-Mn0.60Ni0.25Co0.15O2. Based on the XRD patterns and FE-SEM images, the 5 and 10 mol.% lithium excess samples were observed for spinel structure. The 15 and 20 mol.% lithium excess samples were not observed for the structure. We can conclude that the spinel structure was made in 0.3Li2MnO3 x 0.7LiMn0.60-Ni0.25Co0.15O2, due to a lack of lithium. The discharge specific capacity of 5, 10, 15, and 20 mol.% lithium excess were measured at 216, 246, 262, and 261 mA h g(-1), respectively. Cyclic voltammograms show that the Li2MnO3 has a lower lithium influence than a spinel or layered structure. Based on these experiment results, we can conclude that the best Li source amount of the 0.3Li2MnO3 x 0.7LiMn0.60-Ni0.25Co0.15O2 synthesis is a 15 mol.% excess.

No abstract