Diffusion-Optimized Long Lifespan 4.6 V LiCoO₂: Homogenizing Cycled Bulk-To-Surface Li Concentration with Reduced...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• High-voltage operation of lithium cobalt oxide (LCO) cathodes, driven by increased charging cut-off voltages (e.g., 4.6 V), aims to boost energy density.
• An ignored challenge is the inhomogeneous bulk-to-surface lithium distribution during cycling, which limits the lifespan of high-voltage LCO.

Purpose of the Study:

• To develop a strategy for achieving a homogeneous bulk-to-surface lithium distribution in LCO cathodes during cycling.
• To enhance the long-term stability and performance of high-voltage LCO cathodes.

Main Methods:

• Constructing an artificial solid-solid lithium diffusion environment on the LCO surface.
• Utilizing in situ X-ray diffraction measurements.
• Performing stress-evolution simulation analysis.

Main Results:

• The diffusion-optimized LCO demonstrated a reversible capacity of 212 mA h g⁻¹.
• Achieved ultrahigh capacity retention of 80% over 600 cycles at 4.6 V.
• Superior stability at 4.6 V is attributed to reduced structural stress resulting from homogeneous bulk-to-surface lithium diffusion.

Conclusions:

• The proposed surface modification strategy effectively creates a homogeneous bulk-to-surface lithium distribution.
• This approach significantly enhances the cycling stability and performance of high-voltage LCO cathodes.
• The findings offer new avenues for designing stable layered oxide cathodes with reduced ion-storage stress.