New Oxyhalide Solid Electrolytes with Enhanced Conductivity for All-Solid-State Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Conventional Li-M-X6 frameworks face conductivity limitations in solid electrolytes (SEs).
• Halide-based SEs are crucial for solid-state battery (ASSB) development but often suffer from poor ionic conductivity.
• Overcoming conductivity limitations is key to advancing high-performance ASSBs.

Purpose of the Study:

• To develop a novel Li-M-X5 oxyhalide chemistry to overcome the conductivity limitations of halide-based SEs.
• To investigate the structural and ionic transport properties of the new oxyhalide material.
• To evaluate the performance of the developed SE in all-solid-state batteries (ASSBs).

Main Methods:

• Synthesis of Li-M-X5 oxyhalide compounds (Li3xTaO3xCl5-3x).
• Comprehensive characterization using X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS).
• Ionic conductivity measurements at various temperatures and electrochemical performance testing in full ASSBs.

Main Results:

• Achieved record ionic conductivities of 9 mS cm⁻¹ at 30 °C and 0.59 mS cm⁻¹ at -35 °C, surpassing most reported halides.
• Confirmed that oxygen incorporation induces structural distortions and enhances ion migration pathways.
• Demonstrated excellent stable cycling in full ASSBs with 100% capacity retention after 3200 cycles at a 4 C rate.

Conclusions:

• The novel Li-M-X5 oxyhalide chemistry offers a promising alternative to conventional SEs.
• Oxygen incorporation is an effective strategy to enhance ionic conductivity in halide-based SEs.
• The developed material enables high-performance and stable operation of ASSBs.