Yosef Talyosef

Comparing the Behavior of Nano- and Microsized Particles of LiMn1.5Ni0.5O4 Spinel as Cathode Materials for Li-Ion Batteries

We report on a rigorous comparative study of nano- and microparticles of Limn 1.5 Ni 0.5 O 4 spinel as cathode materials for Li-ion batteries. The stability of these materials in LiPF 6 /alkyl carbonate solutions in temperatures up to 70°C was explored. Capacity, cycling, rate capabilities, and impedance behavior were also studied. The methods included X-ray diffraction, Raman, X-ray photelectron, Fourier transform infrared, and electron paramagnetic resonance spectroscopies, and electron microscopy, in conjunction with standard electrochemical techniques: voltammetry, chronopotentiometry, and impedance spectroscopy. These materials show an impressive stability in solutions at elevated temperature. The use of nanomaterials was advantageous for obtaining a better rate capability of LiMn 1.5 Ni 0.5 O 4 electrodes. LiMn 1.5 Ni 0.5 O 4 particles develop a unique surface chemistry in solutions that passivates and protects them from detrimental interactions with solution species at elevated temperatures.

Studies of nanosized LiNi0.5Mn0.5O2-layered compounds produced by self-combustion reaction as cathodes for lithium-ion batteries

We report here on the synthesis of layered nanosized LiNi 0.5 Mn 0.5 O 2 compound by a modified self-combustion reaction and the studies of its electrochemical behavior as a cathode material for Li cells. Capacities up to 180-200 mAh/g could be reached during cycling of these electrodes even at 60°C in LiPF 6 /alkyl-carbonate solutions. The nano-LiNi 0.5 Mn 0.5 O 2 material exhibits remarkable stability during prolonged aging and cycling at elevated temperatures. Surface films developed on the nano-LiNi 0.5 Mn 0.5 O 2 particles in the course of cycling/aging contain polycarbonates, LiF, nickel and manganese oxides, and fluorides, and lead to efficient passivation and stabilization of the electrodes.