New Oxyhalide Solid Electrolytes with High Lithium Ionic Conductivity >10 mS cm^-1 for All-Solid-State Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• All-solid-state batteries (ASSBs) are crucial for next-generation energy storage.
• Halide solid electrolytes (SEs) offer oxidation stability but have limited ionic conductivity.
• Improving ionic conductivity in SEs is key for practical ASSB applications.

Purpose of the Study:

• To discover novel solid electrolyte materials for ASSBs.
• To enhance ionic conductivity beyond existing halide SEs.
• To evaluate the performance of new materials in ASSB devices.

Main Methods:

• Synthesis and characterization of new lithium-metal-oxy-halide materials (LiMOCl4, M=Nb, Ta).
• Measurement of ionic conductivity in cold-pressed powder forms at room temperature.
• Fabrication and testing of bulk-type ASSB cells utilizing the synthesized oxyhalides.

Main Results:

• Discovery of LiMOCl4 (M=Nb, Ta) with high ionic conductivities (10.4 mS/cm for Nb, 12.4 mS/cm for Ta).
• Ionic conductivities comparable to or exceeding organic liquid electrolytes.
• ASSB cells demonstrated excellent rate capability with 80% capacity retention at 5C.

Conclusions:

• The novel lithium-metal-oxy-halide materials are promising SE candidates for ASSBs.
• These materials offer a pathway to overcome the conductivity limitations of traditional halide SEs.
• The findings support the practical application of ASSBs with enhanced performance.