The reaction of lithium with a nanostructured Cu6Sn5 + C alloy having approximate composition Sn27Cu31C42 was studied using in-situ x-ray diffraction (XRD) and Sn-119 Mossbauer effect spectroscopy. Lithiation of the Cu6Sn5 + C was found to occur with the formation of an amorphous/nanostructured LixCuSn-like phase where x increases with decreasing voltage. The formation of amorphous/nanostructured grains of Li4.4Sn and/or Li2CuSn-like phases contained in a disordered partially lithiated carbon matrix was found at the bottom of discharge. The expulsion of copper from the LixCuSn-like phase(s) to form nanostructured Li4.4Sn 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 Sn30Co30C40 and amorphous Sn-Si mixtures. Hyperfine parameters found in the present work at given voltages closely resemble those found in the literature for bulk Cu6Sn5. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.040112jes] All rights reserved.