Water Vapor Induced Superionic Conductivity in ZnPS

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Next-generation batteries require sustainable multivalent ions (e.g., Mg2+, Ca2+, Zn2+) for enhanced performance and safety.
• Understanding solid-state multivalent ion transport is critical but remains a challenge.
• Previous work showed Zn2+ conduction in insulating ZnPS3, but with low conductivity.

Purpose of the Study:

• To investigate the effect of water vapor on the ionic conductivity of ZnPS3.
• To elucidate the mechanisms of ion transport in water-exposed ZnPS3.
• To assess the potential for enhancing multivalent ion battery materials.

Main Methods:

• Exposure of ZnPS3 to varying relative humidity levels.
• Impedance spectroscopy with ion-selective electrodes.
• Ionic transference number measurements and Zn metal deposition/stripping.

Main Results:

• Room-temperature conductivity increased by orders of magnitude (up to 1.44 mS cm-1) upon water vapor exposure.
• Both Zn2+ and H+ were identified as mobile charge carriers.
• Zn2+ contribution to conductivity was significant, indicating superionic conduction.

Conclusions:

• Water adsorption can dramatically enhance multivalent ion conduction in electronically insulating solids like ZnPS3.
• It is crucial to differentiate between H+ and multivalent ion contributions to conductivity in humid environments.
• This study opens pathways for developing advanced multivalent ion battery materials.