In addition to alternative modifications of carbon and organic composite materials, intermetallic alloys are promising candidates for new anode materials for lithium ion batteries (LIBs) because of the significantly increased theoretic capacities when compared to conventionally used graphite. However, the drastic volume changes during lithiation of pure metals such as Al or Sn lead to degradation of particle-to-particle contacts, resulting in very low cyclic stabilities. One of the various concepts to solve this problem is to use intermetallic alloys as new anode materials. For example, Cu₆Sn₅ and Cu₃Sn are promising anode materials because Cu does not form intermetallic compounds with Li. A (Cu)-alloy matrix would act to buffer the strain induced by volume changes and simultaneously ensure electrical contact between lithiated regions.

Advanced materials design by computational methods rely significantly on experimentally determined thermodynamic and phase diagram data of the material systems to be able to simulate the electrochemical behaviour of new lithium ion batteries. Therefore comprehensive experimental investigations applying various methods like PXRD and SC-XRD studies, thermal analysis, and drop calorimetry were performed to gain a full understanding of the Cu-Li-Sn alloy system. The outcome of our comprehensive experimental work includes 4 isothermal sections, 8 isopleths, a liquidus projection and a reaction scheme as well as mixing and formation enthalpies. In addition, six new ternary intermetallic compounds could be found and their structure was described. Based on these results, the equilibrium lithiation reactions of Cu-Sn alloys could be proposed for the first time.

In this presentation we would like to briefly report about the special features and designs of our experimental methods. Subsequently, selected experimental results on Cu-Li-Sn will be shown and discussed. Our comprehensive experimental data together with literature data will lead to a very well founded CALPHAD assessment as an input for computational materials design.

 

This work has been funded by the FWF under the project I559-N19 and by the DFG under the projects FL-730/1-2 and CU 203/ 1-2, all within the DFG priority project SPP 1473 “WeNDeLIB”.