Fe^II/Fe^III mixed-valence state induced by Li-insertion into the metal-organic-framework Mil53(Fe): A DFT+U study

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• 作者：C. Combelles^a ; M. Ben Yahia^a ; L. Pedesseau^a ; M.-L. Doublet ; ^a ; ^{doublet@univ-montp2.fr}
• 关键词：Lithium-ion batteries ; First-principles DFT calculations ; Redox mechanisms ; Mixedvalence ; State
• 刊名：Journal of Power Sources
• 出版年：2011
• 出版时间：1 April 2011
• 年：2011
• 卷：196
• 期：7
• 页码：3426-3432
• 全文大小：801 K

文摘

The iron-based metal-organic-framework MIL53(Fe) has recently been tested as a cathode materials for Li-Ion batteries, leading to promising cycling life and rate capability. Despite a poor capacity of 70 mAh g⁻¹ associated with the exchange of almost 0.5Li/Fe, this result is the first evidence of a reversible lithium insertion never observed in a MOF system. In the present study, the MIL53(Fe) redox mechanism is investigated through first-principles DFT+U calculations. The results show that MIL53(Fe) is a weak antiferromagnetic charge transfer insulator at T = 0 K, with iron ions in the high-spin S = 5/2 state. Its reactivity vs elemental lithium is then investigated as a function of lithium composition and distribution over the most probable Li-sites of the MOF structure. The redox mechanism is fully interpreted as a two-step insertion/conversion mechanism, associated with the stabilization of the Fe³⁺/Fe²⁺ mixed-valence state prior to the complete decomposition of the inorganic–organic interactions within the porous MOF architecture.