Surface and Grain Boundary Coating for Stabilizing LiNi_0.8Mn_0.1Co_0.1O₂ Based Electrodes

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• High-capacity nickel-rich layered oxides like LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) are crucial for advanced lithium-ion batteries.
• Practical capacity loss and reduced working voltage during operation hinder the widespread adoption of NMC811.
• Particle degradation and structural instability during cycling lead to performance decline.

Purpose of the Study:

• To improve the cycle life and electrochemical performance of NMC811 electrodes.
• To investigate the protective effects of an amorphous lithium titanate (LTO) coating applied via atomic layer deposition (ALD).
• To understand the interplay between chemical and mechanical factors in battery aging through structural analysis.

Main Methods:

• Atomic layer deposition (ALD) for amorphous LTO coating.
• Electrochemical testing to evaluate cycle life and capacity retention.
• Operando X-ray diffraction (XRD) and dilatometry to monitor structural changes during cycling.

Main Results:

• The LTO coating effectively covers NMC811 surfaces, including cavities and grain boundaries.
• Operando XRD revealed significant structural evolution in uncoated NMC811 during delithiation, which was mitigated by the LTO coating.
• Coated NMC811 exhibited highly reversible phase changes, indicating enhanced bulk structure stability.
• Capacity retention improved from 86% to 93% after 140 cycles for coated NMC811 compared to uncoated.

Conclusions:

• Amorphous LTO coating via ALD is a viable strategy to enhance the structural stability and electrochemical performance of Ni-rich layered oxide cathodes.
• Grain boundary engineering is critical for improving the cycle life of high-capacity cathode materials.
• The study highlights the importance of addressing both chemical and mechanical degradation pathways in lithium-ion battery aging.