Li_1.6AlCl_3.4S_0.6: a low-cost and high-performance solid electrolyte for solid-state batteries

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Solid electrolytes (SEs) are critical for advanced rechargeable batteries but face limitations in cost, scalability, and ionic conductivity.
• Lithium tetrahaloaluminates are cost-effective but suffer from low Li+ conductivity and high activation energy.
• Developing high-performance, economical SEs is essential for commercializing all-solid-state batteries (ASSBs).

Purpose of the Study:

• To synthesize a novel lithium aluminum chalcohalide solid electrolyte with improved ionic conductivity.
• To investigate the structural and transport properties of the new material.
• To evaluate the performance of the developed SE in all-solid-state battery applications.

Main Methods:

• One-step mechanochemical milling synthesis of lithium aluminum chalcohalide (Li1.6AlCl3.4S0.6) from inexpensive precursors.
• Characterization using high-resolution X-ray diffraction (XRD) and 6Li magic-angle-spinning (MAS) NMR spectroscopy.
• Computational analysis using ab initio molecular dynamics (AIMD) simulations.

Main Results:

• Achieved a significant increase in ionic conductivity from 0.008 mS cm-1 for LiAlCl4 to 0.18 mS cm-1 for Li1.6AlCl3.4S0.6 at 25 °C.
• Structural analysis revealed tetrahedrally-coordinated LiCl-S octahedra facilitating 3D Li+ transport.
• AIMD simulations confirmed an enhanced 3D Li+ migration network with increased diffusivity.
• All-solid-state battery half-cells demonstrated high-rate and stable cycling performance.

Conclusions:

• The synthesized Li1.6AlCl3.4S0.6 solid electrolyte offers a cost-effective solution with enhanced ionic conductivity.
• The mixed Cl-S anion sublattice and resulting structural features promote efficient 3D Li+ transport.
• This material shows significant potential for high-performance and stable all-solid-state batteries.