Starting from published charge/discharge curves and X-ray data on Pmmn-LiFeO2 and LiFe5O8 as cathode materials vs. Li anode, a scheme of electrochemical reactions is proposed to explain the unclear electrode functionality of the 'corrugated layer' LiFeO2 phase. The scheme was validated by quantum-mechanical calculations (CRYSTAL09 code, hybrid B3LYP Hamiltonian) on a number of structural models for Li 1-xFeO2, LiFe5O8, and Li 3Fe5O8. Magnetic interactions were taken into account, finding antiferromagnetic (Li1-xFeO2) and ferrimagnetic (LiFe5O8 and Li3Fe 5O8) orderings as stable states. At variance with spinel-like LiFe5O8, Li3Fe5O 8 displays a rocksalt-type superstructure. The computed energies for reactions (I) 4LiFeO2 → 4Li0.75FeO2 + Li, (II) 4Li0.75FeO2 + Li → 4/5LiFe5O 8 + 8/5Li2O, and (III) 1/2LiFe5O8 + Li ↔ 1/2Li3Fe5O8 are 4.44, -3.62, and -2.10 eV, respectively. Such values compare satisfactorily with the average charge/discharge voltages observed for positive electrodes made up of Pmmn-LiFeO2 and of LiFe5O8. © 2010 Elsevier B.V. All rights reserved.
Catti, M., Montero Campillo, M. (2011). First-principles modelling of lithium iron oxides as battery cathode materials. JOURNAL OF POWER SOURCES, 196(8), 3955-3961 [10.1016/j.jpowsour.2010.11.062].
First-principles modelling of lithium iron oxides as battery cathode materials
CATTI, MICHELE;
2011
Abstract
Starting from published charge/discharge curves and X-ray data on Pmmn-LiFeO2 and LiFe5O8 as cathode materials vs. Li anode, a scheme of electrochemical reactions is proposed to explain the unclear electrode functionality of the 'corrugated layer' LiFeO2 phase. The scheme was validated by quantum-mechanical calculations (CRYSTAL09 code, hybrid B3LYP Hamiltonian) on a number of structural models for Li 1-xFeO2, LiFe5O8, and Li 3Fe5O8. Magnetic interactions were taken into account, finding antiferromagnetic (Li1-xFeO2) and ferrimagnetic (LiFe5O8 and Li3Fe 5O8) orderings as stable states. At variance with spinel-like LiFe5O8, Li3Fe5O 8 displays a rocksalt-type superstructure. The computed energies for reactions (I) 4LiFeO2 → 4Li0.75FeO2 + Li, (II) 4Li0.75FeO2 + Li → 4/5LiFe5O 8 + 8/5Li2O, and (III) 1/2LiFe5O8 + Li ↔ 1/2Li3Fe5O8 are 4.44, -3.62, and -2.10 eV, respectively. Such values compare satisfactorily with the average charge/discharge voltages observed for positive electrodes made up of Pmmn-LiFeO2 and of LiFe5O8. © 2010 Elsevier B.V. All rights reserved.
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