Low-Frequency Phonon Dispersion Relation Enabling Stable Cathode from Spent Lithium-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Sustainable Energy

Background:

• Direct recycling of spent lithium-ion batteries addresses environmental pollution and resource waste.
• Regenerated LiNi_0.5Co_0.2Mn_0.3O₂ (NCM) cathodes exhibit poor cycle life due to transition metal (TM) migration and defect formation.

Purpose of the Study:

• To enhance the structural stability and electrochemical performance of directly recycled NCM cathode materials.
• To inhibit transition metal migration and defect formation in regenerated NCM through lattice stress engineering.

Main Methods:

• Introduction of local lattice stress into the regenerated NCM cathode during the repair process.
• Analysis of phonon mode localization and changes in phonon dispersion relations.
• Evaluation of TM atom migration and defect structure formation under stress.

Main Results:

• The introduced stress gradient localized phonon modes and altered the phonon dispersion relation.
• Lowered vibration frequencies of TM-O bonds inhibited TM atom migration and defect formation.
• Regenerated NCM demonstrated significantly improved structural stability and electrochemical performance during cycling.

Conclusions:

• Lattice stress engineering, by modifying phonon dispersion, effectively suppresses TM migration and defective structures in regenerated cathodes.
• This approach offers a pathway for developing durable, high-performance regenerated cathode materials for sustainable lithium-ion batteries.