Electrical Properties, Defect Structures, and Ionic Conducting Mechanisms in Alkali Tungstate Li₂W₂O₇

Area of Science:

• Solid-state ionics
• Materials science
• Electrochemistry

Background:

• High-conductivity solid-state ionic conductors are crucial for solid-state electrochemical devices.
• Discovering new materials with efficient ionic transport remains a significant challenge in the field.

Purpose of the Study:

• To investigate mixed oxide-ion and lithium-ion conduction in Li₂W₂O₇.
• To elucidate the underlying ionic conducting mechanisms in this triclinic material.
• To provide fundamental insights into ionic transport in low-symmetry materials.

Main Methods:

• Electrochemical impedance spectroscopy
• DC polarization
• Oxygen concentration cell measurements
• Theoretical analysis of neutron diffraction data
• Bond-valence-based energy landscape calculations

Main Results:

• Demonstrated predominant oxide-ion conduction and minor lithium-ion conduction in Li₂W₂O₇ at high temperatures.
• Revealed multidimensional ionic migration pathways for both oxide-ions and lithium-ions via energy landscape calculations.
• Provided strong evidence for mixed ionic conductivity through combined experimental and theoretical analyses.

Conclusions:

• Li₂W₂O₇ exhibits mixed oxide-ion and lithium-ion conduction with distinct conducting mechanisms.
• The study offers fundamental insights into ionic transport in low-symmetry materials.
• Findings pave the way for the discovery of novel ionic conductors for advanced electrochemical applications.