Space-Charge Layers in All-Solid-State Batteries; Important or Negligible?

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Ionics

Background:

• All-solid-state batteries offer enhanced safety over traditional Li-ion batteries.
• High Li-ion conductivity in solid electrolytes is critical for performance.
• Challenges in fast charging are often linked to electrode-solid electrolyte interface kinetics.

Purpose of the Study:

• To model and quantify the role of space-charge layers at the electrode-solid electrolyte interface.
• To assess the interface capacitance and resistance attributed to space-charge layers.
• To determine the impact of space-charge layers on all-solid-state battery performance.

Main Methods:

• Development of a simplified model to analyze space-charge layers.
• Application of the model to LiCoO2 and graphite electrodes with LLZO and LATP solid electrolytes.
• Voltage-dependent analysis of interface properties.

Main Results:

• Space-charge layers are typically around one nanometer thick for common electrode-electrolyte combinations.
• The resistance introduced by space-charge layers is generally negligible.
• An exception is observed when Li-ion depleted layers form within the solid electrolyte.

Conclusions:

• Space-charge layers are unlikely to be a limiting factor in the performance of most all-solid-state batteries.
• Focus should be placed on other factors contributing to interface kinetic limitations.
• Further research may be needed for specific cases involving Li-ion depleted layers.