Al─N Co-Doped LLZO Solid Electrolytes via One-Step Sintering: Toward High Ionic Conductivity.

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Garnet-type lithium lanthanum zirconium oxide (LLZO) is a leading solid electrolyte candidate for solid-state lithium batteries.
• Its practical application is hindered by insufficient ionic conductivity.
• Enhancing ionic conductivity is crucial for developing high-performance solid-state batteries.

Purpose of the Study:

• To investigate the efficacy of cation-anion co-doping for improving LLZO ionic conductivity.
• To synthesize Al-N co-doped LLZO using a facile one-step sintering process.
• To evaluate the electrochemical performance of the co-doped LLZO in solid-state battery applications.

Main Methods:

• One-step sintering process for synthesizing Al-N co-doped LLZO.
• Ionic conductivity measurements.
• Nudged elastic band (NEB) calculations to study Li+ migration barriers.
• Fabrication and testing of symmetric Li cells and full cells (LiFePO4|LLZO-Al0.50N0.50|Li).

Main Results:

• Achieved a high ionic conductivity of 2.19 × 10^-3 S cm^-1 in Al-N co-doped LLZO.
• NEB calculations confirmed reduced energy barriers for Li+ migration due to Al-N co-doping.
• Stable lithium plating/stripping cycling over 600 hours in symmetric cells.
• Full cells retained 82.6% capacity after 200 cycles.

Conclusions:

• Al-N co-doping is an effective strategy to significantly enhance the ionic conductivity of LLZO.
• The enhanced ionic transport facilitates stable cycling in solid-state lithium batteries.
• This approach offers a promising route for developing high-performance garnet-type solid electrolytes.