Gas Evolution in All-Solid-State Battery Cells

The formation of gaseous side products in liquid electrolyte-based lithium-ion batteries has been intensively studied in recent years and identified as being one of the sources of degradation (an indication of electrolyte and electrode instabilities). Herein, we demonstrate, to our knowledge for the first time, that gassing can also arise in all-solid-state battery cells made of Ni-rich layered oxide cathode materials and thiophosphate-based solid electrolytes. Combining isotopic labeling, titration for quantitative carbonate determination, and operando gas analysis, our findings reveal the evolution of CO2 stemming from carbonate species on the cathode surface as well as O2 from the bulk of the oxide cathode at potentials above 4.5 V with respect to Li+/Li, among others.