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Iron Oxides as Anodic Materials in Li Rechargeable Batteries
Published online by Cambridge University Press: 10 February 2011
Abstract
The open framework material, CaFe204 and the isostructural solid solution phases, LiyCa1−(x+y)/2SnxFe2−xO4, where 0<y<x and O<x<0.6 have been evaluated as promising anodic materials in Li-ion batteries. These materials can be discharged to low potential, the end member CaFe2O4 attaining a discharge capacity of 800 mAh/g at a cutoff voltage of 50 mV. The capacity is enhanced on substitution of Fe3+, for Sn4+ in the framework (920 mAh/g for the composition, Li0.6Ca0.4Sn0.6Fe1.404). On introducing Sn into the structure the reversible capacity is also substantially increased compared with the parent material. Although there is a large irreversible component to the redox process during first discharge-charge, the materials can sustain a stable reversible capacity of >600 mAh/g within the voltage window of 3.0-0.005 V. The profile of the electronic density plots suggest there is no phase separation to Li/Sn alloy phases on reduction, but rather a lithium-rich, oxygen deficient Sn/Fe/oxide matrix is formed.
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- Copyright © Materials Research Society 1999
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