Lithium-Metal Anode Instability of the Superionic Halide Solid Electrolytes and the Implications for Solid-State...

Area of Science:

• Materials Science
• Electrochemistry
• Solid-state Chemistry

Background:

• Halide-based solid electrolytes offer high ionic conductivity and oxidation stability, making them attractive for solid-state batteries.
• While their cathode interface stability is established, their compatibility with lithium metal anodes remains unexplored.

Purpose of the Study:

• To investigate the interfacial stability between halide solid electrolytes, specifically Li3InCl6, and lithium metal anodes.
• To evaluate the potential of halide solid electrolytes as cathode electrolytes in combination with other solid electrolytes.

Main Methods:

• Sputter deposition of lithium metal onto Li3InCl6.
• In-situ X-ray photoelectron spectroscopy (XPS) for interfacial analysis.
• Impedance spectroscopy to measure interphase resistance and assess combined electrolyte performance.

Main Results:

• A thermodynamically unstable interface forms between Li3InCl6 and lithium metal.
• This instability leads to the continuous growth of interphase resistance.
• Combined use of Li3InCl6 with Li6PS5Cl as cathode and separator electrolytes, respectively, did not enable stable, low-impedance operation.

Conclusions:

• Oxidation-stable halide-based lithium superionic conductors are unsuitable for direct use against lithium metal anodes due to interfacial instability.
• Halide solid electrolytes may still be viable as cathode electrolytes in specific solid-state battery configurations.