This proposal aims to investigate the evolution of the structures of layered oxysulfide materials which show promise as lithium ion battery electrodes. The lithiation of Sr2MnO2Cu3.5S3 results in complete copper extrusion and replacement by lithium. This is highly reversible when the material is used as a cathode in a lithium ion battery. The voltage profile shows some complexity however and the structures of the cathode materials will be probed using neutron powder diffraction on materials obtained from dismantled batteries which have been cycled to particular points on the first two charge/discharge cycles. These results will provide information on the mechanism of the lithium insertion/copper extrusion process (discharge) and the reverse process (charge) which will be coupled with Li-NMR and other measurements.