In situ X-ray absorption spectro-electrochemical study of amorphous tin-based composite oxide material

摘要

We have measured the XAFS spectra of a sample of tin-based composite oxide (TCO) material with a nominal composition of Sn{sub}1.0B{sub}0.56P{sub}0.40Al{sub}0.42O{sub}3.47 during the discharge and charge cycles in an "in situ" configuration. Ourresults confirm the amorphous nature of TCO material and show that Sn-O bond length in TCO is 2.12 A. Upon discharging, initially Li interacts with the electrochemically active Sn-O center forming metallic Sn in amorphous form and/or highly dispersedclusters containing just a few atoms. Upon further discharge, Li alloys with Sn forming initially amorphous and/or highly dispersed forms of Li{sub}2Sn{sub}5 and/or LiSn and then Li{sub}7Sn{sub}3, Li{sub}5Sn{sub}2, Li{sub}13Sn{sub}5, or Li{sub}7Sn{sub}2.The true nature of the highly dispersed alloys differs from that of the corresponding crystalline phases. Upon charging, metallic Sn is produced with a Sn-Sn distance intermediate to those of gray and white Sn.