The lithium-ion battery cathode materials spinel LiMn 2 O 4 and LiMg 0.05 Mn 1.95 O 3.9 Cl 0.1 samples are synthesised by solid state reaction route, the effects of magnesium and chlorine co-doping on the structure, morphology and electrochemical performance of material LiMn 2 O 4 are studied by X-ray diffraction, scanning electron microscope, electron diffraction spectroscope and galvanostatic charge-discharge, respectively. The results indicate that appropriate amount doping of magnesium and chlorine does not change the spinel structure of LiMn 2 O 4 , and the results reveal that the LiMg 0.05 Mn 1.95 O 3.9 Cl 0.1 has an initial discharge capacity of 125.2 mAh/g at 0.2C, and the capacity retention is still as high as 89.3% even after 100 cycles, which is significantly higher than 79.6% of LiMn 2 O 4. Especially, the LiMg 0.05 Mn 1.95 O 3.9 Cl 0.1 shows the discharge capacity of 91.2 mAh/g at 10C, which higher than that of LiMn 2 O 4 (64.3 mAh/g). The LiMg 0.05 Mn 1.95 O 3.9 Cl 0.1 exhibits excellent cycling performance and rate capability than that of LiMn 2 O 4. Thus, this is a very effective way for comprehensive improving LiMn 2 O 4 electrochemical performance.

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Hydrosilylation or amination products? It depends on water amount and nucleophiles like excess water or produced/added amines.

Abstract:The The mechanism of reaction between 3-hydroxy-3-methyl-2-butanone and malononitrile for the synthesis of 2-dicyanomethylene-4, 5, 5-trimethyl-2,5-dihydrofuran-3-carbonitrile catalyzed by lithium ethoxide was investigated by density functional theory (DFT). The geometries and the frequencies of reactants, intermediates, transition states and products were calculated at the B3LYP/6-31G(d) level. The vibration analysis and the IRC analysis verified the authenticity of transition states. The reaction processes were confirmed by the changes of charge density at the bond-forming critical point. The results indicated that lithium ethoxide is an effective catalyst in the synthesis of 2-dicyanomethylene-4, 5, 5-trimethyl-2, 5-dihydrofuran-3-carbonitrile from malononi-trile and 3-hydroxy-3-methyl-2-butanone. The activation energy of the reaction with lithium ethoxide was 115.86 kJ·mol -1 less than the uncatalyzed reaction. The mechanism of the lithium ethoxide catalyzed reaction differed from the mechanism of the uncatalyzed reaction. Warsaw and Springer-Verlag Berlin Heidelberg. © Versita