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Phase transitions in the LiNi0.5Mn0.5O2 system with temperature
Cited 152 time in
Web of Science
Cited 152 time in Scopus
- Authors
- Issue Date
- 2007-04
- Publisher
- American Chemical Society
- Citation
- Chemistry of Materials, Vol.19 No.7, pp.1790-1800
- Abstract
- We investigate the phase transformations of layered LiNi0.5Mn0.5O2 at finite temperature with a combined computational and experimental approach. The detailed changes in the ionic configurations with temperature are investigated by Monte Carlo simulations on the basis of a coupled cluster expansion that describes the dependence of the energy on the arrangement of Li+, Ni2+, and Mn4+ in the lithium layer and transition metal layer. First-principles energies in the GGA+U approximation were used to fit the Hamiltonian, as we find that GGA+U better represents magnetic interactions than standard GGA. The simulation results suggest two phase-transition temperatures at approximately 550 and 620 degrees C. Below the first phase-transition temperature, a structure with almost no Li/Ni disorder in the Li layer is energetically favorable. Between the two temperatures, a partially disordered flower structure with about 8-11% Li/Ni disorder is found. Above the second phase transition, a structure that is more disordered but still consistent with a root 3 x root 3 honeycomb model with 8-11% Li/Ni disorder is stable. The results from these simulations are corroborated with DSC, TEM, and XRD measurements on a recently synthesized LiNi0.5Mn0.5O2 with negligible Li/Ni disorder.
- ISSN
- 0897-4756
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