Meaning
Glassy or crystalline materials composed of sulfur compounds offer high room-temperature ionic conductivity for use in all-solid-state batteries. These sulfide solid electrolytes typically exhibit better mechanical deformability than oxide-based alternatives, allowing for better contact with electrode particles. They serve as the ionic bridge between the positive and negative terminals.
Ionic Transport
Lithium ions move through the sulfide lattice via a vacancy-hopping mechanism or by moving through interstitial sites. The large, polarizable sulfide ions create a wide pathway that minimizes the energy barrier for ion migration.
Atmospheric Sensitivity
Exposure to moisture in the air causes a chemical reaction that releases hydrogen sulfide gas and degrades the ionic conductivity of the material. Consequently, processing and assembly must occur in a dry room or an inert atmosphere to maintain the purity and safety of the electrolyte. Handling protocols often specify dew points below minus forty degrees to prevent any measurable degradation during the manufacturing stages.
Contact Resistance
Under pressure, the particles deform to fill the gaps at the electrode interface, which reduces the electrical resistance and improves the power density of the battery. The soft nature of these materials allows them to be processed at lower temperatures compared to ceramics.
