Effect of Pressure on Sulfide Based All Solid-State Batteries

All solid-state batteries (ASSBs) are predicted to be the next generation of lithium ion batteries with their wider operating temperature range, higher energy density, and improved safety compared to conventional liquid electrolyte-based batteries. For sulfide-based solid-state batteries, the most common form factor is the stacked pellet type cells consisting of the following layers: a cathode composite, a thick solid-electrolyte, and an anode, all of which are kept under pressure to ensure proper contact. Although this pressure is mandatory for battery operation, there have been no detailed studies of the actual effect of the stack pressure on battery performance nor any indication of an ideal applied load. In this work, we have studied in detail the effect of varying the applied pressure at two stages: during cell fabrication and cell testing. Our results explain discrepancies for ionic conductivity values found in literature for sulfide-based solid-state electrolytes. This study suggests that the pressure used to fabricate the cell is a critical factor for cell performance and also that controlling the stack pressure is necessary to ensure reliable operation of sulfide-based solid-state batteries.