A Metastable Oxygen Redox Cathode for Lithium-Ion Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Simultaneously utilizing cation and anion redox in cathodes is key for high energy-density lithium-ion batteries.
• Challenges include anisotropic volume changes, cation migration, and oxygen loss, hindering long-term stability.

Purpose of the Study:

• To demonstrate stable cation and anion redox behavior in a novel, cobalt-free layered oxide cathode material.
• To investigate the structural attributes responsible for enhanced electrochemical performance and stability.

Main Methods:

• Synthesis and characterization of a metastable, cobalt-free layered oxide, Li _0.693[Li _0.153Ni _0.190Mn _0.657]O ₂ (LLNMO).
• Electrochemical testing, including cycling performance and capacity retention analysis at a specific current density.
• Structural analysis to correlate material properties with electrochemical stability.

Main Results:

• LLNMO cathode retained 97.4% of its initial capacity (222.4 mAh/g) after 50 cycles.
• Negligible voltage decay was observed, indicating remarkable electrochemical stability.
• The metastable O6-type structure (R-3m symmetry) with specific local geometry suppressed cation migration and volume changes (<2.3% along c-axis).

Conclusions:

• Metastable layered oxides with unique structural features offer a promising pathway for stable, high-energy lithium-ion battery cathodes.
• The demonstrated material overcomes key stability challenges associated with combined cation and anion redox.
• This research contributes to the development of next-generation ultra-high-energy lithium-ion batteries.