Amorphous Phase Induced Lithium Dendrite Suppression in Glass-Ceramic Garnet-Type Solid Electrolytes

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Lithium metal-based solid-state batteries (SSBs) offer higher energy density and safety than lithium-ion batteries.
• Garnet-type Li7La3Zr2O12 (LLZO) is a promising solid electrolyte but faces challenges with lithium dendrite growth.
• Lithium dendrites form at voids and grain boundaries, compromising battery cycling stability and safety.

Purpose of the Study:

• To investigate a novel glass-ceramic tantalum-doped LLZO (Ta-LLZO) solid electrolyte prepared via a unique melting process.
• To evaluate the effectiveness of an intrinsically generated amorphous phase in suppressing lithium dendrite growth.
• To optimize sintering conditions for dense, highly conductive Ta-LLZO with improved dendrite suppression capabilities.

Main Methods:

• Preparation of glass-ceramic Ta-LLZO using a unique melting and cooling process.
• Characterization of the amorphous phase composition and distribution during sintering.
• Sintering optimization at reduced temperatures and times.
• Measurement of ionic conductivity and critical current density (CCD) in Li|LLZTO|Li symmetric cells.
• In situ scanning electron microscopy (SEM) for observing lithium plating and dendrite stability.

Main Results:

• The glass-ceramic process yielded an amorphous phase (approx. 4 wt%) containing Li2O and Li2O-SiO2, segregating to grain boundaries.
• Optimized sintering at 1130 °C for 0.5 h resulted in a dense structure with high ionic conductivity (0.64 mS cm⁻¹).
• The amorphous phase effectively hindered lithium dendrite growth, improving current density distribution.
• The Li|LLZTO|Li symmetric cell achieved a critical current density (CCD) of 1.15 mA cm⁻².
• In situ SEM confirmed superior dendrite stability properties of the developed solid electrolyte.

Conclusions:

• The developed glass-ceramic Ta-LLZO presents a promising strategy for fabricating dense solid electrolytes.
• The intrinsic amorphous phase effectively suppresses lithium dendrite growth, enhancing SSB safety and performance.
• This approach offers a viable route for the future implementation of lithium metal solid-state batteries.