Operando chemo-mechanical evolution in LiNi_0.8Co_0.1Mn_0.1O₂ cathodes

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Nickel-rich Lithium Nickel Cobalt Manganese Oxide (NCM) materials are crucial for high-energy-density lithium-ion batteries.
• Polycrystalline NCM materials suffer from cracking during cycling, leading to capacity fade and reduced battery lifespan.
• Understanding the chemo-mechanical stresses during battery operation is vital for improving NCM performance.

Purpose of the Study:

• To investigate the stress evolution in polycrystalline LiNi_0.8Co_0.1Mn_0.1O₂ (P-NCM811) cathodes during battery cycling.
• To correlate chemo-mechanical behavior with microcrack formation and capacity decay.
• To guide the design of NCM materials with enhanced electrochemical performance and cycle life.

Main Methods:

• Development and implementation of an optical fiber sensor with micrometer resolution for *in operando* stress detection.
• Integration of the sensor within the P-NCM811 cathode to capture stress variations during (de)lithiation.
• Analysis of the relationship between particle anisotropy, structural stress, microcrack generation, and electrochemical performance.

Main Results:

• Anisotropy in primary particles of P-NCM811 induces structural stress, leading to microcracks and capacity decay.
• Isotropy in primary particles effectively reduces structural stress, preventing microcrack formation.
• An ordered arrangement structure in P-NCM811 resulted in high electrochemical performance, retaining 82% capacity over 500 cycles.

Conclusions:

• The study provides novel *in operando* insights into the chemo-mechanical evolution of NCM materials during battery operation.
• Particle isotropy is identified as a key factor in mitigating stress-induced cracking and improving cycle life.
• The findings offer a new strategy for designing advanced cathode materials for high-performance rechargeable batteries.