Electro-Chemo-Mechanical Evolution of Sulfide Solid Electrolyte/ Li Metal Interfaces: Operando analysis and ALD Interlayer Effects

Sulfide solid electrolyte (SE) materials show promise for high-performance solid-state batteries because of their high ionic conductivity and ease of processing. However, several sulfide electrolytes have suffered from chemical and electrochemical instability against Li metal anodes. Herein, we use a suite of operando microscopy and spectroscopy techniques to study the impact of artificial solid electrolyte interphases (SEI) on the electro-chemo-mechanical degradation of Li₁₀GeP₂S₁₂ (LGPS) solid electrolytes. Al₂O₃ interlayers deposited using atomic layer deposition (ALD) are used as a model system to show that the application of artificial SEI interlayers can delay degradation at the Li/LGPS interface by modifying the solid electrolyte interphase chemistry and morphology. Optical and scanning electron microscopy are used to rationalize the electrochemical response of the system, which is attributed to a delayed onset of mechanical degradation at the interface when ALD interlayers are used. Operando X-ray photoelectron spectroscopy demonstrates that the dynamic evolution of SEI chemistry is impacted by the presence of the ALD interlayer. Auger electron spectroscopy and operando optical microscopy provide visual evidence of spatial heterogeneity of Li plating, which is attributed to the chemo-mechanical degradation of the ALD interphase. The implications of these observations provide valuable insights toward the development of robust interlayers for solid-state batteries.