Mössbauer effect studies of sputter-deposited tin–cobalt and tin–cobalt–carbon alloys

Abstract

Sn–Co–C alloys are now used as negative electrodes in the latest generation of Li-ion batteries, although not much is known about the phases present in the materials, their micro or nanostructure nor their physical properties. Here, sputtered combinatorial libraries of Sn 1− x Co x (0 < x < 0.6) and [Sn 0.63Co 0.37] 1− y C y (0.1 < y < 0.5) were studied by 119Sn Mössbauer effect spectroscopy and X-ray diffraction to learn their phase content and micro or nanostructure. The sputtered Sn 1− x Co x films showed the presence of crystalline β-Sn, a new metastable cubic Sn–Co phase, an amorphous Sn 1− x Co x (0.26 < x < 0.45) phase and Co 3Sn 2 as x, or the Co content, increased. The sputtered [Sn 0.63Co 0.37] 1− y C y (0.1 < y < 0.5) materials consist of amorphous grains of Sn 0.63Co 0.37 separated by a carbon matrix. The impact of this nanostructure on the utility of these materials as negative electrodes in Li-ion batteries is discussed.