Abstract :
[en] Li-ion batteries (LIBs) have become the power sources of choice for portable applications, such as, cellular phones, laptop computers … More recently, LIBs have been also selected to power the first-generation of electric vehicles (EVs). Especially for the former application, new LIBs with higher energy and power, safer and cheaper are needed. To achieve this goal, the search and development of new electrode materials is one of the most powerful ways [1-2]. Refer to positive electrode (cathode), layered LiCoO2 is widely used in the LIB for portable applications. Nevertheless, its elevated price and toxicity are serious drawback for to use this material in larger-size LIBs needed for EVs. One of the alternatives to improve the performances of layered LiCoO2-based cathodes is to substitute Co for other transition metal cations as Ni, Mn … Layered LiCo1-2yNi1yMnyO2 has high capacity, high working voltage, improved structural and thermal stability and lower cost compared with LiCoO2. In the present poster we will show several of the most remarkable results attained for preparation and study of layered LiCo2/3Ni1/6Co1/6O2 oxide [3]. Refer to negative electrode (anode), it should be indicated that the lithium titanate Li4Ti5O12 (hereafter named as LTO) is one of the most promising materials to replace the graphite at the negative electrode. LTO is of the most promising materials to replace the graphite as negative electrode (anode). It has a constant operating voltage at approximately 1.5V vs. Li+/Li, which is above the potential range where most electrolytes are reduced [2]. LTO can work under high current loads without risk of internal short circuits as is the case of graphite. This feature notably improves the safety of LIBs.
The spinel-type Li4Ti5O12 anodic material and the layered LiCo2/3Ni1/6Co1/6O2 cathodic material were prepared by a self-combustion method assisted by sucrose. The advantages of this procedure are that it is rapid and cheap. In the case LiMn2O4-based cathodes, it has permitted to prepare single-phase spinel, with different dopant cations in a broad compositional range with high particles size homogeneity [4]
In this work, the structural and morphological characterization of the electrodes materials will be present. The study by X-ray diffraction (XRD) shows that the sample has high purity. The particles size determined from the micrographics obtained by field emission scanning electron microscopy (FE-SEM) were 0.8 micrometre for LTO and 0.3micrometre for LiCo2/3Ni1/6Co1/6O2. The materials are characterized by a high homogeneity and faceted shape. The electrochemical properties of Li4Ti5O12 and LiCo2/3Ni1/6Co1/6O2 had been determined in Li half cell by galvanostatic cycling. Results concerning the studies of cyclability and rate capability will be done. A new design of lithium-ion cell has been assembled using spinel Li4Ti5O12 as anode and high voltage layered LiCo2/3Ni1/6Co1/6O2 as cathode. In Fig. 1a. a selection of charge/discharge curves registered during the cycling is shown. The average voltage of the LIB cell is ca. 2.1V, being high the capacity drained during the first discharge Q=158.74 mAh g-1. The evolution of the discharge capacity vs. cycle number recorded at 0.5C rate is presented in Fig. 1b.
Acknowledgements: Financial support through the projects MAT 2011-22969 (MEC), MATERYENER Ref. P2009/PPQ-1626 (CAM) and the joint project CSIC/CNRST de Morocco Ref. 2009MA0007 is thankfully recognized. The authors would like to thank AECID and CNRST. References :
[1] M. Armand and J.-M. Tarascon, Nature, 451 (2008) 652.
[2] Ting-Feng Yi, Li-JuanJiang, J.Shu , Cai-BoYue , Rong-SunZhu , Hong-BinQiao, Journal of Physics and Chemistry of Solids 71 (2010) 1236–1242.
[3] A. Mahmoud, Ismael Saadoune, José Manuel Amarilla , Rachid Hakkou. Electrochimica Acta 56 (2011) 4081–408
[4] J.M. Amarilla, R.M. Rojas, F. Pico, L. Pascual, K. Petrov, D. Kovachevav, M.G. Lazarraga, I. Ledjona, J.M. Rojo. J. Power Sources, 174(2) (2007) 1212.
