Electrochemical Features of Li-Ni-Mn-Co Oxides
- PDF / 582,801 Bytes
- 6 Pages / 595 x 842 pts (A4) Page_size
- 85 Downloads / 200 Views
0973-BB04-05
Electrochemical Features of Li-Ni-Mn-Co Oxides Ashraf Abdel-Ghany1, Karim Zaghib2, Alain Mauger3, François Gendron1, A.E. Eid4, H. Abbas4, Ahmed M. Hashem4, Chintalapalle V. Ramana5, and Christian M. Julien1 1 INSP, University Paris 6, 140 rue de Lourmel, Paris, 75015, France 2 IREQ, 1800 boulevard Lionel-Boulet, Varennes, J3X 1S1, Canada 3 MPPU, CNRS, 140 rue de Lourmel, Paris, 75015, France 4 Inorganic Chemistry Dept, National Research Center, El Behoos Street, Giza, Cairo, 1000, Egypt 5 Nanoscience and Surface Chemistry Laboratory, University of Michigan, Ann Arbor, MI, 48109 ABSTRACT We report the electrochemical behavior of various layered oxides in Li cells. A series of LiNiyMnyCozO2 materials (with z=1-2y) was synthesized by “chimie douce” and investigated as positive electrodes in rechargeable lithium batteries. Electrochemical performances of LiNiyMnyCozO2 oxides are tested in a cell using non-aqueous 1M LiPF6 dissolved in EC-DEC. Charge discharge profiles are investigated as a function of the rate capability, the voltage window and the synthesis parameters of the cathode. A relation is found between the gravimetric capacity and the cation disorder of materials as indicated by magnetometry analysis. INTRODUCTION Lithium-ion batteries are emerging as the prime power sources for portable electronics due to their high energy density. These cells currently use the layered LiCoO2 electrode material which delivers only 50% of the theoretical capacity (273 mAh/g) in the 4-volt range [1-3]. The limitation in utilization has been mostly attributed to chemical instabilities which can be suppressed on going from LiCoO2 to LiNixMnyCozO2 [4-5]. Among the mixed-cation oxides, LiCo0.2Ni0.8O2, LiNi0.5Mn0.5O2, and LiCo0.33Ni0.33Mn0.33O2 have been identified to have better chemical stability, better cyclability and rate capability. The LiNiyMnyCo2-yO2 compounds must satisfy three rules. First, the sum of the cation occupations on the 3b sites of space group R-3m in the transition-metal layers equals one. Second, the sum of the cation oxidation state times the cation occupation must equal three. Third, the concentration of Mn and Ni ions should be identical for the complete electronic transfer as Mn4+, Ni2+ [4]. In this work, we report the electrochemical behavior of LiNiyMnyCo2-yO2 layered materials in Li cells using non-aqueous electrolyte 1M LiPF6 dissolved in EC-DEC. A series of materials with different cobalt amounts, z=1-2y, have been synthesized by “chimie douce”. Structural properties have been investigated using various analytical methods, especially magnetic measurements, which, in conjunction with XRD refinements, accurately allow the determination the cationic disorder in the interlayer space of the oxide lattices. Electrochemical performances of LiNiyMnyCozO2 oxides are tested and charge discharge profiles are investigated as a function of the rate capability and the voltage window. EXPERIMENT LiNiyMnyCozO2 cathode materials were prepared by sol-gel method assisted by carboxylic acid solution. Stoic
