How Surface Reconstruction Drives Heterogeneous Bulk Delithiation in Single-Crystalline Ni-Rich Layered Oxide...

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Single-crystalline (SC) Ni-rich layered oxide cathodes are crucial for high-energy batteries.
• Their performance is limited by bulk lithium-ion (Li+) diffusion and surface reconstruction during high-voltage cycling.
• Oxygen loss during cycling can transform the layered cathode surface into spinel/rock-salt structures, impeding Li+ transport.

Purpose of the Study:

• To investigate the correlation between surface reconstruction and bulk delithiation in SC Ni-rich cathodes.
• To understand how anisotropic structural evolution of cathode particles affects electrochemical degradation.
• To establish a mechanistic link between surface degradation and bulk delithiation kinetics.

Main Methods:

• Utilized multi-rate operando X-ray diffraction (XRD) studies.
• Investigated SC Ni-rich layered oxide cathodes aged under different voltage windows.
• Employed single-layer pouch full cells for operando analysis.

Main Results:

• Quantified the impact of surface reconstruction on bulk delithiation heterogeneity.
• Demonstrated that increased surface reconstruction exacerbates electrochemical capacity fade.
• Observed promotion of phase separation due to heterogeneous bulk delithiation.

Conclusions:

• Established a direct mechanistic link between surface degradation and bulk delithiation in SC Ni-rich cathodes.
• Provided a framework for non-destructively probing kinetics-dependent degradation.
• Aimed to guide strategies for enhancing cycling stability in next-generation batteries.