Thermal-Induced Reversible Spinel-to-Layered Phase Transition in LiCoO₂ Cathodes

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Lithium cobalt oxide (LiCoO2) cathode materials degrade during lithium-ion battery cycling.
• An irreversible phase transition from layered phase (LP) to spinel phase (SP) causes performance loss.
• Regenerating the SP phase back to LP is critical for battery longevity.

Purpose of the Study:

• To investigate the feasibility of thermal-induced relithiation and reverse phase transition in LiCoO2.
• To elucidate the mechanism of the spinel-to-layered phase transition.
• To provide insights for advanced synthesis and regeneration strategies for layered oxide cathodes.

Main Methods:

• Thermal analysis to determine transition temperature.
• In situ and ex situ characterization techniques to observe phase transformation.
• Microscopy and spectroscopy to study the transition mechanism.

Main Results:

• The spinel-to-layered phase transition occurs at a mild temperature (around 300 °C).
• The transition follows a "nucleation-oscillation-aggregation" mechanism.
• The phase propagation exhibits strong anisotropic characteristics from particle surface to bulk.

Conclusions:

• Thermal treatment can effectively induce relithiation and reverse phase transition in degraded LiCoO2.
• Understanding the "nucleation-oscillation-aggregation" mechanism is key to controlling the regeneration process.
• These findings support the development of strategies for regenerating and synthesizing advanced layered oxide cathodes for improved lithium-ion batteries.