Designing Co-Free Medium-Ni Layered Oxide Cathodes via Additional Li Substitution

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• High-capacity cathode materials are essential for high-energy-density Lithium-ion batteries (Li-ion batteries).
• Ultra-Ni-rich layered oxides face structural instability challenges.
• Increasing cutoff voltage in medium-Ni oxides improves capacity but damages structure.

Purpose of the Study:

• To propose a strategy for enhancing Li-ion battery cathode performance without cobalt.
• To investigate the effect of Li-ion enrichment in medium-Ni layered oxides.
• To identify optimal compositions for improved capacity and cycling stability.

Main Methods:

• Synthesized and characterized a series of Li-rich, Co-free layered oxide compositions (Li_1+yNi_1-3yMn_2yO₂).
• Employed electrochemistry and spectroscopy to study anionic redox and structural stability.
• Evaluated Li/Ni mixing suppression and full-cell performance.

Main Results:

• Identified Li_1.12Ni_0.64Mn_0.24O₂ as a threshold composition for optimal performance.
• Demonstrated reversible anionic redox contributing to structural stability up to 4.5 V.
• Observed suppressed Li/Ni mixing due to excess Li ions.

Conclusions:

• Li-ion enrichment in medium-Ni oxides offers a viable route to high-capacity, stable, Co-free cathodes.
• The developed Li_1.12Ni_0.64Mn_0.24O₂ cathode achieves ≈200 mA h g^-1 with 100 cycles.
• This approach bypasses the need for cobalt in Ni-based cathodes for advanced Li-ion batteries.