Thermodynamics of New LIB-electrode materials

The present proposal concerns basic research for the development of new anode and cathode materials for Lithium Ion Batteries within the framework of SPP 1473 "WeNDeLIB". The goal is the generation of valuable and concise experimental thermodynamic and phase equilibria data as a basis for the modelling of material systems relevant for electrode materials in lithium ion batteries. A starting point will be a comprehensive compilation of literature data and a check of the experimental. The systems under investigation will be the ternary systems (Co,Cu,Ni)-Li-Sn as feasible anode materials and LiTEO2 (TE = Co, Mn, Ni) as cathode materials. This includes at one hand the experimental evaluation of phase relations by means of XRD, thermal analysis and metallography. At the other hand thermochemical investigations like i) calorimetric measurement of the enthalpy of formation and enthalpy of mixing in solid and liquid systems, ii) KEMS and isopiestic vapor pressure measurements concerning mainly the Li-activities in the respective ternary systems, iii) EMF measurements of the partial Gibbs energy of lithium in the respective ternary systems.

It is a special challenge to develop high power energy storage devices for electro mobility and renewable power sources like solar- or wind energy. Electrochemical storage devices, essentially accumulators and fuel cells are potential candidates. Especially for electro mobility it is important to carry high amounts of energy at low weight and volume for large ranges.Li-ion batteries as we know them in notebooks, cell phones and cameras are light, compact and relatively small. However, based on the currently used materials their capacity is much too low for high power applications. For essential progress new materials for electrodes, electrolyte and separator have to be found. Particularly the carbon anode which has a small Li-ion storage capacity is a weak point. Their substitution by metallic anodes could be a possible solution which was the topic of this project. Modern materials design is based on a systematic computational description of materials systems based on experimental data. These data are provided by basic research on such systems. Mixing behavior, composition and structure as well as thermochemical and physical properties need to be investigated. Intermetallic systems which have several pure metals as constituents have been investigated within this project. The mixing behavior of the metallic anodes with lithium is of course a basic question. Thus we decided to experimentally characterize the materials systems Li-Sn, Cu-Li and Cu-Li-Sn Literature information on these systems is scarce and partially contradicting. Various experimental methods like X-ray structure analysis, thermal analysis, metallography and calorimetry have been performed. In a close co-operation with partners from the Karlsruher Institute of Technology and the research center in Jülich the above mentioned intermetallic systems could be characterized and calculated in a large extend. This project was embedded in the DFG priority program SPP 1473 WeNDeLIB, "Materials with new design for improved Lithium-Ion-Batteries".