Structure design enables stable anionic and cationic redox chemistry in a T2-type Li-excess layered oxide cathode.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Li-rich/excess cathode materials offer high energy density for next-generation Li-ion batteries.
• Irreversible oxygen loss and transition metal migration cause voltage decay and capacity fade in these materials.

Purpose of the Study:

• To develop a novel Li-excess cathode material with enhanced structural stability and electrochemical performance.
• To elucidate the charge compensation mechanism and redox activities in the new material.

Main Methods:

• Synthesis of a metastable layered T2-type Li-excess cathode material (Li _0.72[Li _0.12Ni _0.36Mn _0.52]O ₂).
• Electrochemical cycling and performance evaluation.
• In/ex-situ spectroscopic techniques for analyzing redox activities and structural evolution.

Main Results:

• The T2-type structure exhibits distinct oxygen stacking and Li coordination compared to O3-type structures.
• Effective restraint of voltage decay and excellent capacity retention achieved through reversible Li migration.
• Quantification of irreversible/reversible anionic and cationic redox activities, clarifying charge compensation.

Conclusions:

• The novel T2 structure demonstrates enhanced anionic redox stability, mitigating key degradation pathways.
• This work provides a new avenue for developing high-energy-density Li-rich cathode materials.
• The findings offer insights into the fundamental mechanisms governing the performance of Li-rich cathodes.