Study on foreign atom diffusion in electrolyte separators for solid-state batteries published on the cover of Advanced Functional Materials

Ceramic, garnet-based solid-state electrolytes such as lithium lanthanum zirconium oxide (Li7La3Zr2O12, LLZO) require a heating step at temperatures above ~1000 °C for their production into solid-state battery cells. In this heating step, known as sintering, the original powder material is densified, resulting in the respective dense final component of the battery cell (cathode or separator between the electrodes). Many previous studies have taken a closer look at this step, particularly in combination with cathode materials, as a number of undesirable effects can occur here.

A study has now been carried out at IEK-1 in which the LLZO separator was analyzed after the co-sintering step with the cathode. For the first time, extensive cobalt ion diffusion from the cathode into the separator was detected, which led to a discoloration of the material and adversely affected its electrochemical properties. This was accompanied by the formation of three different cobalt-containing crystal phases that accumulate in different regions of the separator. The cause of the formation of these secondary phases was elucidated using molecular dynamic simulations.

The knowledge gained from this study can now be used for future research to specifically analyze, reduce or suppress cobalt ion diffusion.

The work was carried out in an international collaboration with the Lawrence Livermore National Laboratory, the University of Michigan, the National Taiwan University of Science and Technology and the University of Maryland.

The related work was published in the journal "Advanced Functional Materials" and additionally the graphic illustration was selected for the cover of the journal issue (see figure).

Link to the publication: https://doi.org/10.1002/adfm.202302939

Source: Scheld, W. S., Kim, K., Schwab, C., Moy, A. C., Jiang, S.-K., Mann, M., Dellen, C., Sohn, Y. J., Lobe, S., Ihrig, M., Danner, M. G., Chang, C.-Y., Uhlenbruck, S., Wachsman, E. D., Hwang, B. J., Sakamoto, J., Wan, L. F., Wood, B. C., Finsterbusch, M., Fattakhova-Rohlfing, D., The Riddle of Dark LLZO: Cobalt Diffusion in Garnet Separators of Solid-State Lithium Batteries. Adv. Funct. Mater. 2023, 33, 2302939. https://doi.org/10.1002/adfm.202302939

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Last Modified: 14.11.2023