Reconstructed Perovskite Layers Regulate Surface-Oxygen Dimerization States Enabling Reversible Anionic Redox in...

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Li-rich layered oxides offer high capacity due to oxygen redox but suffer from poor cycling stability caused by oxygen loss and structural degradation.
• Irreversible oxygen redox leads to significant voltage decay and capacity fade in these promising cathode materials.

Purpose of the Study:

• To enhance the stability and cycling performance of Li-rich layered oxide cathodes.
• To suppress irreversible oxygen redox and mitigate structural degradation using a surface modification strategy.

Main Methods:

• Coating Li-rich layered oxides (Li1.2Ni0.2Mn0.6O2) with a perovskite-type PrMO3-x layer.
• Investigating the modulation of oxygen redox from O2 to O2- via oxygen vacancies and Mn cation interactions.
• Analyzing the formation of a stable cathode-electrolyte interphase (CEI) and suppression of phase transitions.

Main Results:

• The PrMO3-x layer effectively traps migrating oxygen dimers and promotes electron donation, converting O2 release to O2-.
• This surface modification significantly improves the reversibility and kinetics of oxygen redox reactions.
• Modified cathodes (PrMO@LRNM) exhibit 93% capacity retention and minimal voltage decay (1.4 mV/cycle).

Conclusions:

• Perovskite surface coating is an effective strategy to stabilize Li-rich layered oxides by controlling oxygen redox.
• The PrMO3-x interphase prevents structural degradation and promotes a robust CEI, enhancing long-term cycling performance.
• This approach is applicable to other high-voltage, cobalt-lean/free cathodes for advanced battery applications.