Improved electrochemical properties of a coin cell using LiMn1.5Ni0.5O4 as cathode in the 5 V range

Phase pure LiMn1.5Ni0.5O4 powders were synthesized by a chemical synthesis route and were subsequently characterized as cathode materials in a Li-ion coin cell comprising a Li anode and lithium hexafluorophosphate (LiPF6), dissolved in dimethyl carbonate (DMC) + ethylene carbonate (EC) [1:1, v/v ratio] as electrolyte. The spinel structure and phase purity of the powders were characterized using X-ray diffraction and micro-Raman spectroscopy. The presence of both oxidation and reduction peaks in the cyclic voltammogram revealed Li+ extraction and insertion from the spinel structure. The charge-discharge characteristics of the coin cell were performed in the 3.0-4.8 V range. An initial discharge capacity of similar to 140 mAh g(-1) was obtained with 94% initial discharge capacity retention after 50 repeated cycles. The microstructures and compositions of the cathode before and after electrochemistry were investigated using scanning electron microscopy and energy-dispersive analysis by X-ray analysis, respectively. Using X-ray diffraction, Raman spectroscopy and electrochemical analysis, we correlated the structural stability and the electrochemical performance of this cathode. (c) 2006 Elsevier B.V. All rights reserved.