Wet Chemistry Route to Li₃InCl₆: Microstructural Control Render High Ionic Conductivity and Enhanced All-Solid-State...

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Halide solid electrolytes (SEs) are promising for all-solid-state lithium batteries (ASSLBs) due to their superionic conductivity and compatibility with high-voltage cathodes.
• Current halide SEs often exhibit Li+ conductivity below theoretical predictions and that of sulfide-based electrolytes.
• Microstructural features like grain boundaries and microstrain critically influence ionic conductivity but are seldom optimized.

Purpose of the Study:

• To develop a scalable and facile wet chemical synthesis for highly conductive Li3InCl6.
• To investigate the impact of aprotic solvents on microstructural characteristics and ionic conductivity.
• To evaluate the performance of the optimized Li3InCl6 in ASSLB full cells.

Main Methods:

• A wet chemical approach was employed to synthesize Li3InCl6.
• Aprotic solvents were utilized to control grain boundary formation and reduce microstrain.
• Electrochemical impedance spectroscopy was used to measure ionic conductivity.
• Full cells utilizing LiNi0.6Mn0.2Co0.2O2 cathodes were assembled and tested.

Main Results:

• The wet chemical method yielded highly conductive Li3InCl6 (>2 mS cm-1).
• Aprotic solvent treatment reduced grain boundaries and microstrain, achieving ionic conductivity >4 mS cm-1 at 22 °C.
• Minimized grain boundaries improved moisture stability and solid-solid interfacial contact.
• Full cells demonstrated stable cycling at room temperature (155 mAh g-1 at 0.2 C) and excellent long-term stability at 60 °C (85% retention after 1000 cycles, 99.75% Coulombic efficiency).

Conclusions:

• Aprotic solvent-mediated synthesis is a viable route for producing high-quality Li3InCl6 with enhanced ionic conductivity.
• Optimized microstructural control is crucial for improving the performance of halide solid electrolytes in ASSLBs.
• The developed Li3InCl6 shows significant potential for practical application in high-performance all-solid-state lithium batteries.