Phase stability of cation-doped LiMnO{sub 2} within the GGA+U approximation.
First principles density functional theory calculations within the GGA+U approximation were performed for LiMn{sub 1-x}M{sub x}O{sub 2}, a candidate cathode material for lithium-ion batteries, with (x = 0.25, M = Ni, Fe, Co, Mg), to investigate the effect of doping on the destabilization of the monoclinic structure relative to the layered rhombohedral structure. A primary motivation of this work was to determine to what extent the predictions of the electronically more realistic GGA+U treatment would differ from those obtained within the GGA. Several significant qualitative changes are found. For the pristine system in the rhombohedral structure, Mn ions show a high-spin state within GGA+U, rather than the low-spin (metallic) state found in GGA. The doped rhombohedral structure is unstable within GGA+U, rather than metastable, as in GGA. In the monoclinic structure, the dopant oxidation states are the same (trivalent Fe, divalent Co, Ni) in GGA+U and GGA. Co and Ni ions show a higher spin state in GGA+U than in GGA. The divalent dopants destabilized the monoclinic structure to a greater extent than trivalent dopants within the GGA+U, as expected from previous GGA calculations. Overall, our results suggest that the relatively close agreement sometimes found between the properties calculated within the GGA and GGA+U may be misleading, because the underlying electronic behaviors may be profoundly different.
- Research Organization:
- Argonne National Laboratory (ANL)
- Sponsoring Organization:
- EE; NSF
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 935296
- Report Number(s):
- ANL/CSE/JA-62077
- Journal Information:
- Model. Simul. Mater. Sci. Eng., Journal Name: Model. Simul. Mater. Sci. Eng. Journal Issue: Jul. 2008 Vol. 16; ISSN 0965-0393
- Country of Publication:
- United States
- Language:
- ENGLISH
Similar Records
Doping effect on the structural properties of Cu{sub 1−x}(Ni, Zn, Al and Fe){sub x}O samples (0
Effects of Al-doping on the stabilization of monoclinic LiMnO{sub 2}