An In Situ Study of the Electrochemical Reaction of Li with Amorphous∕Nanostructured Cu6Sn5 + C

The reaction of lithium with a nanostructured Cu 6 Sn 5 + C alloy having approximate composition Sn 27 Cu 31 C 42 was studied using in-situ x-ray diffraction (XRD) and 119 Sn Mössbauer effect spectroscopy. Lithiation of the Cu 6 Sn 5 + C was found to occur with the formation of an amorphous/nanostructured Li x CuSn-like phase where x increases with decreasing voltage. The formation of amorphous/nanostructured grains of Li 4.4 Sn and/or Li 2 CuSn-like phases contained in a disordered partially lithiated carbon matrix was found at the bottom of discharge. The expulsion of copper from the Li x CuSn-like phase(s) to form nanostructured Li 4.4 Sn is difficult to detect in the present measurements. No crystalline components were found during lithiation and delithiation of the electrode material. The smooth sloping discharge curve during the lithiation of Sn in the amorphous/nanostructured material has resemblance to those previously seen in amorphous Sn 30 Co 30 C 40 and amorphous Sn-Si mixtures. Hyperfine parameters found in the present work at given voltages closely resemble those found in the literature for bulk Cu 6 Sn 5.