FestBatt2 - Solid State Battery Cluster: Harmonization of cell tests and electrochemical characterization

The aim of the project is the harmonization of testing procedures for all solid state batteries as well as the detailed electrochemical characterization of the four different FestBatt cell types. The focus lies on the adaption and further development of highly resolving characterization methods as well as the standardization of electrical testing procedures. The harmonization of the testing procedures and the transferability as well as the reproducibility is assured in Round-Robin tests. For the electrochemical characterization, established techniques in the field of conventional lithium ion batteries are transferred to all solid state batteries and specific questions are examined. Here the focus especially is on the development of testing procedures and the realization of measurements with respect to the dendrite stability. The required HF impedance measuring technique (1 MHz – 3 GHz) is therefore, in a practical way combined with the  impedance measuring technique for the deconvolution of electrochemical processes (charge-transfer, diffusion: mHz – MHz).

In this project, electrical test procedures are harmonized and high-resolution characterization methods for solid-state batteries are developed. A solid-state internal standard will be defined and validated in round-robin tests, which will be used both in performance tests and for measuring dendrite stability. The evaluation of the harmonized test procedures is performed in close cooperation with the cell platforms. Electrical measurements to analyze performance, cycling stability and dendrite stability will be performed. Analogous to FestBatt I, transferability and reproducibility are to be achieved. Impedance spectroscopic methods will be developed for detailed analysis of the various FestBatt cells. The focus will be on SSB-specific issues such as grain boundary effects in the solid electrolyte, dendrite stability, charge transport across solid electrolyte/solid electrolyte interfaces in hybrid cells (RF impedance spectroscopy (100 kHz - 1 GHz)) and the coupling of electronic and ionic conduction via charge transfer reactions in composite electrodes (taking into account the influence of CAM coatings). Successfully established characterization methods will be transferred to the cell platforms for direct use in further material and cell development.