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Stable SiOC/Sn Nanocomposite Anodes for Lithium‐Ion Batteries with Outstanding Cycling Stability
Author(s) -
Kaspar Jan,
Terzioglu Caglar,
Ionescu Emanuel,
GraczykZajac Magdalena,
Hapis Stefania,
Kleebe HansJoachim,
Riedel Ralf
Publication year - 2014
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201303828
Subject(s) - materials science , nanocomposite , tin , alloy , lithium (medication) , chemical engineering , phase (matter) , anode , amorphous solid , carbon fibers , composite material , metallurgy , electrode , composite number , chemistry , crystallography , organic chemistry , medicine , engineering , endocrinology
Silicon oxycarbide/tin nanocomposites (SiOC/Sn) are prepared by chemical modification of polysilsesquioxane Wacker‐Belsil PMS MK (SiOC MK ) and polysiloxane Polyramic RD‐684a (SiOC RD ) with tin(II)acetate and subsequent pyrolysis at 1000 °C. The obtained samples consist of an amorphous SiOC matrix and in‐situ formed metallic Sn precipitates. Galvanostatic cycling of both composites demonstrate a first cycle reversible capacity of 566 mAhg −1 for SiOC MK /Sn and 651 mAhg −1 for SiOC RD /Sn. The superior cycling stability and rate capability of SiOC RD /Sn as compared to SiOC MK /Sn is attributed to the soft, carbon‐rich SiOC matrix derived from the RD‐684a polymer, which accommodates the Sn‐related volume changes during Li‐uptake and release. The poor cycling stability found for SiOC MK /Sn relates to mechanical failure of the rather stiff and fragile, carbon‐poor matrix produced from PMS MK. Incremental capacity measurements outline different final Li–Sn alloy stages, depending on the matrix. For SiOC RD /Sn, alloying up to Li 7 Sn 2 is registered, whereas for SiOC MK /Sn Li 22 Sn 5 stoichiometry is reached. The suppression of Li 22 Sn 5 phase in SiOC RD /Sn is rationalized by an expansion restriction of the matrix and thus prevention of a higher Li content in the alloy. For SiOC MK /Sn on the contrary, the matrix severely ruptures, providing an unlimited free volume for expansion and thus formation of Li 22 Sn 5 phase.