Viscoplasticity Driven Approach to Increase Critical Current Density in Sulfide Electrolytes

All-solid-state batteries (ASSBs) show a high practical potential to achieve safe battery design with high energy densities when using Li metal as an anode. Sulfide electrolytes due to their high ionic conductivity (0.1 mS/cm to &gt;10 mS/cm) are among the most promising candidates. However, Li dendrite growth results in shorting at critical current densities (CCD) that are well below values that are needed for practical applications. This currently limits the development of sulfide-based ASSBs, and therefore, it is very important to stabilize sulfide-electrolyte/Li-metal interfaces to enable high current densities without shorting.<br/><br/>Extensive efforts have been devoted to increasing the interfacial stability with methods that emphasize chemical and electrochemical modifications. However, methodologies that increase the CCD in sulfide electrolytes based on mechanics have not been reported. Herein we report a viscoplasticity based approach to increase the CCD of sulfide electrolytes. Previous studies have demonstrated that some sulfide SEs deform in a viscous manner^1,2. Considerations of this effect offer a new perspective on how to suppress Li dendrite growth. To investigate the viscoplastic properties of sulfide electrolytes, Li₆PS₅Cl (LPSC) was selected as an important candidate due to its high ionic conductivity and high stability against Li metal compared with other sulfide electrolytes. Viscoplasticity in this material was investigated and characterized by integrating nanoindentation experiments and finite element simulations, and improved CCD was observed by employing cycling conditions that take advantage of this inelastic deformation. Such improvement is attributed to the interaction between the specially designed charging-discharging cycles and the viscous deformation of the electrolyte. We have also performed finite element simulations to further validate our argument. This type of approach can provide major improvements in the performance of ASSBs and can also be combined with chemical/electrochemical methods to further enhance cell performance using sulfide electrolytes.<br/><br/><br/>References:<br/>1. C. E. Athanasiou, X. Liu, M. Y. Jin, E. Nimon, S. Visco, C. Lee, M. Park, J. Yun, N. P. Padture, H. Gao, B. W. Sheldon, <i>Cell Reports Phys. Sci.</i> <b>3</b>, 100845 (2022).<br/>2. M. Papakyriakou, M. Lu, Y. Liu, Z. Liu, H. Chen, M. T. McDowell, S. Xia, <i>J. Power Sources</i>. <b>516</b> (2021), doi:10.1016/j.jpowsour.2021.230672.