| Autor: |
Palomares, V., Goñi, A., de Muro, I. Gil, de Meatza, I., Bengoechea, M., Cantero, I., Rojo, T. |
| Předmět: |
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| Zdroj: |
Journal of The Electrochemical Society; 2009, Vol. 156 Issue 10, pA817-A821, 5p |
| Abstrakt: |
The influence of the carbon content in LiFePO4/C composites synthesized by the freeze-drying method was studied by varying the citric acid (chelating agent): Fe ratio. Diminishing this ratio from 1:1 to 0.33:1 led to a gradual reduction of the carbon content from 16.1 to 7.2% wt and different morphologies. Transmission electron microscopy micrographs of the composite with the greatest carbon percentage (16%) show mainly 30 nm LiFePO4 particles homogeneously embedded in a carbon network. Samples containing less carbon exhibit only one type of morphology, 200-700 nm aggregates made up of an intimate mixture of LiFePO4 particles and carbon. Galvanostatic cycling from 2 to 4 V vs Li/Lit evidences the typical LiFePO4 redox behavior at 3.4 V, and a second contribution at 2.65 V probably related to the carbon content. At a high rate, a good specific capacity value is observed for the nanoparticulate sample (16% wt C), whereas poorer performance is observed for low carbon content samples (11 and 7.2 wt % C). Heterogeneous and insufficient carbon covering together with phosphate particle aggregation in these latter samples can account for this behavior. Two carbon distribution models are proposed to explain different electrochemical responses. In all cases, a good capacity retention is observed after prolonged cycling. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Supplemental Index |
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