Synergistic O^2-/Li⁺ Dual Ion Transportation at Atomic Scale

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Physics

Background:

• Ion migration is crucial for electrochemical devices, typically involving one ion type (O^2- or Li⁺) due to differing energy barriers.
• Charge neutralization often relies on valence changes of immobile ions (e.g., Co²⁺/Co³⁺).

Purpose of the Study:

• To investigate the fundamental ion migration mechanisms in spinel Li₄Ti₅O₁₂ under electrical bias.
• To observe and understand synergistic ion transport at the atomic scale in an all-solid-state battery.

Main Methods:

• Construction of an all-solid-state battery using spinel Li₄Ti₅O₁₂ as an anode.
• In-situ observation using transmission electron microscopy (TEM) under electrical bias.
• Verification of ion migration paths using first-principles calculations.

Main Results:

• Direct atomic-scale observation of synergistic Li⁺ and O^2- ion migration.
• Oxygen anion extraction initiated at 2.2 V due to low vacancy formation energy.
• Formation of a Li- and O-deficient ordered phase at 2.7 V, with simultaneous Li⁺ and O^2- extraction.

Conclusions:

• Revealed a new synergistic ion migration mechanism involving both Li⁺ and O^2-.
• Proposed and verified migration paths for Li⁺ and O^2- ions.
• Provides novel insights into ion transport in lithium ion conductors and functional devices.