Direct observation of lithium metal dendrites with ceramic solid electrolyte

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Lithium metal anodes are prone to dendrite formation, risking battery short circuits.
• Solid electrolytes with high shear modulus are investigated to suppress dendrite growth.
• Lithium lanthanum zirconium oxide (LLZO) is a promising solid electrolyte due to its mechanical strength and stability.

Purpose of the Study:

• To investigate the interface behavior between lithium metal and LLZO during battery cycling under pressure.
• To understand the mechanisms of dendrite formation and LLZO degradation.
• To evaluate LLZO as an ionic conductive separator for lithium metal batteries.

Main Methods:

• In situ scanning electron microscopy (SEM) to observe real-time interface evolution.
• Cyclic testing of symmetrical Li-Li cells with LLZO.
• Energy dispersive spectroscopy (EDS) for elemental analysis of dendrites and LLZO cross-sections.

Main Results:

• SEM videos showed inhomogeneous lithium dissolution and deposition, leading to dendrite growth.
• EDS analysis confirmed Li, C, and O in dendrites.
• LLZO cross-sections revealed inhomogeneous distribution of La, Zr, and C after cycling, indicating lithium loss and side reactions.

Conclusions:

• LLZO's mechanical properties are advantageous, but electrochemical stabilization at the lithium metal interface requires improvement.
• Inhomogeneous lithium behavior and side reactions at the interface are key challenges for LLZO in lithium metal batteries.
• Further research is needed to enhance the electrochemical stability of the garnet-lithium metal interface.