Intermetallic anodes are promising candidates of new anode materials for lithium ion batteries. Therefore the knowledge of relevant alloy phase diagrams containing lithium is mandatory to understand the nature and mechanisms of charging and discharging intermetallic anodes, like e.g. Cu-Sn alloys. The Cu-Li-Sn phase diagram and the constituting binary systems Cu-Sn, Li-Sn and Cu-Li have been investigated extensively by experimental methods. Powder-XRD, SC-XRD studies and thermal analysis were applied to describe the alloy phase diagrams. Drop calorimetry was performed to provide supplementary data for the thermodynamic optimization. Based on the phase diagram a lithiation route for Cu-Sn alloys was suggested. The outcome of this work is fundamental for further application-oriented studies, e.g. the calculation of the open circuit voltage. This work has been funded by the FWF under the project I559-N19 within the DFG priority project SPP 1473 “WeNDeLIB”.