Antimony Alloys and Intermetallic Compounds

Almost simultaneous to tin, the theoretical capacity of pure antimony based on the formation of Li3 b was known to be 660 mAh g [38,39]. However, similar to tin, enhanced volume changes are found during the formation of Li-Sb compounds, leading to an important capacity fading upon cycling. Both the presence of other elements in the active material and nanostructuring contribute to reduce this phenomenon. 

For CoSb3, an initial capacity close to 500 mAh g was experimentally observed [40], and then the capacity strongly decreased to 200 mAh g after 20 cycles. The use of a nanostructured material improved cycling stability, and values over 400 mAh g were reported after 20 cycles [41]. An additional improvement of the capacity retention upon cycling is obtained when multiwall carbon nanotubes (MWCTs) are added to CoSb3, especially after 20 cycles [42]. 

Concerning the application of Mossbauer effect to the study of CoSb3 electrodes, it should be noted that the Sb spectral shape is complicated by the / = 7/2h 5/2+ nuclear transition and its natural linewidth. Nevertheless, the 

Correlation between IS and the Li/Sb ratio. The percent numbers indicate the relative contributions of the different species. Reproduced from Ref. 47 with permission of Elsevier. 

Mossbauer spectroscopy has become an irreplaceable tool in the study of electrode materials for Li-ion batteries. Relevant information is gathered on the changes in oxidation state and chemical environment of elements such as iron and tin, which are commonly present in various electroactive species. 

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