Snx[BPO4]1−x composites as negative electrodes for lithium ion cells: Comparison with amorphous SnB0.6P0.4O2.9 and effect of composition |
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Authors: | Donato Ercole Conte Abdelmaula Aboulaich Josette Olivier-Fourcade Christian Jordy |
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Institution: | a Institut Charles Gerhardt—Equipe Agrégats, Interfaces et Matériaux pour l’Energie, UMR 5253-CNRS, Université Montpellier II, Place E. Bataillon, 34095 Montpellier, France b SAFT, 111-113 Bd. A. Daney, 33074 Bordeaux Cedex, France c CNES, Centre Spatial de Toulouse, 18 Avenue Edouard Belin, 31401 Toulouse, France |
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Abstract: | A comparative study of two Sn-based composite materials as negative electrode for Li-ion accumulators is presented. The former SnB0.6P0.4O2.9 obtained by in-situ dispersion of SnO in an oxide matrix is shown to be an amorphous tin composite oxide (ATCO). The latter Sn0.72BPO4]0.28 obtained by ex-situ dispersion of Sn in a borophosphate matrix consists of Sn particles embedded in a crystalline BPO4 matrix. The electrochemical responses of ATCO and Sn0.72BPO4]0.28 composite in galvanostatic mode show reversible capacities of about 450 and 530 mAh g−1, respectively, with different irreversible capacities (60% and 29%). Analysis of these composite materials by 119Sn Mössbauer spectroscopy in transmission (TMS) and emission (CEMS) modes confirms that ATCO is an amorphous SnII composite oxide and shows that in the case of Sn0.72BPO4]0.28, the surface of the tin clusters is mainly formed by SnII in an amorphous interface whereas the bulk of the clusters is mainly formed by Sn0. The determination of the recoilless free fractions f (Lamb-Mössbauer factors) leads to the effective fraction of both Sn0 and SnII species in such composites. The influence of chemical composition and especially of the surface-to-bulk tin species ratio on the electrochemical behaviour has been analysed for several SnxBPO4]1−x composite materials (0.17<x<0.91). The cell using the compound Sn0.72BPO4]0.28 as active material exhibits interesting electrochemical performances (reversible capacity of 500 mAh g−1 at C/5 rate). |
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Keywords: | Sn-based composites Lithium-ion batteries Negative electrodes Mö ssbauer spectroscopy LixSn alloys |
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