期刊
COMPUTATIONAL MATERIALS SCIENCE
卷 44, 期 4, 页码 1243-1251出版社
ELSEVIER
DOI: 10.1016/j.commatsci.2008.08.014
关键词
Li2MSiO4; Dilithium-orthosilicate; Cathode material; Lithium ion battery; Structural stability; Electronic structure
资金
- National 973 Program of China [2007CB209702]
- National Natural Science Foundation of China [20433060, 10774124]
Dilithium-orthosilicate oxides Li2MSiO4 (M denotes transition metals) have been one of the focuses in the field of new cathode materials for Li-ion batteries recently, due to their possible high capacities and probabilities achieving by experiment. Using the density functional theory within both the generalized gradient approximation (GGA) and GGA + U frameworks, the structural stabilities, electronic structures and delithiation process for the dilithium-orthosilicate oxides Li2MSiO4 (M = Mn, Fe, Co, Ni) are systematically investigated. Within the GGA + U approach, LiMSiO4 is shown to be a stable non-stoichiometric structure, while the compound Li1.5MSiO4 are unstable relative to a two-phase form containing UNSA and UMO4, which is consistent with the experimental voltage profiles. For Li0.5MSiO4, though the formation energies are negative for Mn-system and Ni-system, the absolute values are so small that they would be likely to also undergo phase separation at room temperature. The average deintercalation voltages calculated by the GGA + U scheme are in good agreement with the available experimental data. Furthermore, the possibility of the exchange of two electrons per M in Li2MSiO4 is also discussed based on the calculated results. (C) 2008 Elsevier B.V. All rights reserved.
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