First Principles Simulations of Phase Stability in Stoichiometric and Doped LiMnO 2
- PDF / 45,739 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 64 Downloads / 171 Views
First Principles Simulations of Phase Stability in Stoichiometric and Doped LiMnO2 Alexander I. Landa1, Chun-Chieh Chang1, Prashant N. Kumta1, Blanka Magyari-Köpe2, Levente Vitos3, Rajeev Ahuja4, and Igor A. Abrikosov4 1 Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890, U.S.A. 2 Theoretical Physics, Royal Institute of Technology, SE-10044, Stockholm, Sweden 3 Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, SE-10044, Stockholm, Sweden 4 Condensed Matter Theory Group, Department of Physics, Uppsala University, Box 530, SE75121, Uppsala, Sweden
ABSTRACT
The full charge density exact muffin-tin orbitals method has been used to study the stability of lithium-manganese oxides exhibiting different crystallographic allotropes. Calculations have been performed for ferromagnetic and antiferromagnetic phases of LiMnO2 as well as for the phase with local moment disorder. For the ordered LiMnO2 compound we reproduced the correct ground state, the antiferromagnetic orthorhombic structure. The effect of doping LiMnO2 by Co was considered with the aim to predict the stabilization of the layered structure.
INTRODUCTION
There has been significant interest in the synthesis, structure and electrochemical properties of lithiated transition metal oxides due to their use in lithium-ion batteries. At present, LiCoO2 and LiNiO2 doped with Co, LiNi1-xCoxO2, are widely used as cathode materials for rechargeable lithium-ion batteries. These compounds exhibit the layered α-NaFeO2-type structure with the rhombohedral symmetry in the space group R 3 m. The layered structure of the oxide provides a two-dimensional channel perfectly suited to provide an easy migration (diffusion) of lithium during the charge (extraction of Li) - discharge (insertion of Li) cycles. However, the high cost and the potential toxicity of cobalt make it imperative to search for alternative cathode materials. It is essential that these replacement materials exhibit the same or higher electrochemical capacity without exhibiting any undesired irreversible phase transformations or decomposition during electrochemical cycling. In this regard, LiMnO2 equivalent in chemical formula to LiCoO2, has drawn much attention because of the lower cost and the more environmentally benign nature of manganese as opposed to cobalt. However, the instability and the energetics of the transport reaction of lithium in LiMnO2 make its use still very tenuous. The thermodynamically stable phase of LiMnO2 exhibits the orthorhombic structure belonging to the space group Pmmn [1]. The layered metastable form of LiMnO2 (isostructural with LiCoO2) exhibits the monoclinic space group C2/m, which has been recently synthesized [2]. The layered structure of this compound provides AA4.16.1
easy lithium diffusion during intercalation. However, although most of the lithium can be removed from this layered structure during charging, the reinsertion of lithium, during discharge is not a reversi
Data Loading...
