Cycle Degradation Analysis by High Precision Coulometry for Sulfide-Based All-Solid-State Battery Cathode under Various Potentials

All-solid-state batteries (ASSBs) using sulfide-based solid electrolytes (SEs) are promising energy storage devices beyond the present liquid-type lithium-ion batteries (LIBs) using organic solvents, which are expected to realize the adaptation of new systems such as higher-voltage cathodes. However, in recent years, undesirable side reactions are being reported in the nanometer-order region at the interface of cathode active materials/SEs. Therefore, we evaluated the cycle durability of the all-solid-state cathode half-cells using an argyrodite-structured sulfide-based solid electrolyte at various potentials at 60 °C and then measured the coulombic behavior by high precision coulometry. Furthermore, the interfaces of the cathode active material/SE were observed using secondary electron microscopy (SEM), transmission electron spectroscopy (TEM), and electron diffraction (ED). In conclusion, a strong correlation was found between the coulombic behavior and material decomposition at the interface.