Mechanical Reinforcement of Layered Oxide Cathodes for Continuous High-Power Rate Delivery throughout Cycling

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Increasing demand for high-energy-density cathodes with high power and stable cycling.
• Ni-rich layered cathodes (e.g., Li[Ni0.9Co0.05Mn0.05]O2, NCM90) offer high capacity but face structural instability and capacity loss due to volume expansion and phase transitions under high current densities.

Purpose of the Study:

• To develop a novel cathode architecture that enhances structural integrity and electrochemical performance.
• To address the limitations of Ni-rich cathodes by improving Li+ transport and mechanical stability.

Main Methods:

• Fabrication of a core-shell gradient plus shell (CSGPS90) architecture with a Ni-rich core, Mn-rich shell, and gradient nanorod microstructure.
• Electrochemical cycling tests under regular (0.8 C/1 C) and variable (4N3F) conditions.
• Post-mortem analysis to investigate structural changes and Li+ behavior.

Main Results:

• CSGPS90 demonstrated significantly improved capacity retention (89.0% vs. 61.9% for NCM90 after 1000 cycles at 0.8 C/1 C).
• Under the 4N3F protocol, CSGPS90 maintained 83.0% capacity retention compared to 33.9% for NCM90 after 1000 cycles.
• Post-mortem analysis revealed uniform Li+ extraction in CSGPS90, contrasting with Li+ trapping and NiO-like phase formation in NCM90.

Conclusions:

• The CSGPS90 architecture enhances structural durability, leading to improved Li+ kinetics and sustained power delivery.
• Microstructural gradient engineering is crucial for reinforcing mechanical stability and achieving stable power output in high-power battery applications.