In Situ Phosphoester Polymer Layer Locking Oxygen Migration in Ni-Rich Cathodes Under Ultra-High Voltage

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Increasing energy density in lithium batteries requires higher cutoff voltages for nickel-rich cathodes.
• High voltages cause lattice oxygen instability, leading to structural degradation and gas evolution.
• Oxygen-induced failure initiates preferentially in separator-adjacent electrode regions under diffusion limitations.

Purpose of the Study:

• To develop an in situ interlayer that suppresses oxygen-related degradation in nickel-rich cathodes.
• To enhance the structural stability and electrochemical performance of LiNi0.8Co0.1Mn0.1O2 electrodes at ultra-high voltages.

Main Methods:

• An in situ formed phosphoester-derived polymer interlayer was applied to LiNi0.8Co0.1Mn0.1O2 electrodes.
• The interlayer's chemical stabilization involved metal-oxygen-phosphorus coordination to increase oxygen vacancy formation energy.
• Physical stabilization utilized a crosslinked polymer network to regulate oxygen transport and capture evolved oxygen species.

Main Results:

• The interlayer increased oxygen vacancy formation energy by 0.61 eV.
• Gas evolution and strain accumulation were significantly suppressed.
• The modified cathode achieved 81.5% capacity retention after 100 cycles at 4.6 V, a 25.3% improvement over the pristine electrode.
• Stable cycling of a 3.2 Ah pouch full cell was demonstrated.

Conclusions:

• The dual-function interlayer effectively mitigates oxygen-related degradation in Ni-rich cathodes through a synergistic chemical-physical mechanism.
• This scalable interfacial strategy advances the development of safer, higher-energy lithium batteries.
• The in situ polymer interlayer approach offers a promising solution for ultra-high-voltage cathode stabilization.