Formation Cycle Control for Enhanced Structural Stability of Ni-Rich LiNiCoMn_1-x-yO₂ Cathodes

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Nickel-rich NCM cathode materials offer high energy density for lithium-ion batteries.
• Increased nickel content leads to phase transformations and side reactions, causing capacity fading.

Purpose of the Study:

• To investigate methods for improving the cycling stability of nickel-rich NCM cathode materials.
• To understand the relationship between initial formation cycles and long-term battery performance.

Main Methods:

• Utilizing a higher cutoff voltage (≥4.35 V) during the initial formation cycle at 0.1 C.
• Analyzing Ni-rich NCM (LiNi0.88Co0.08Mn0.04O2) particles after cycling at 1 C.
• Investigating the formation and evolution of intragranular nanovoids and phase transformations.

Main Results:

• A higher cutoff voltage during the initial formation cycle significantly enhances particle stability.
• Lower cutoff voltages lead to oxygen vacancies and irreversible electrolyte decomposition, forming intragranular nanovoids.
• Nanovoid evolution results in NiO-like rock salt phase, intragranular cracks, and structural instability.

Conclusions:

• Controlling the surface chemistry of Ni-rich NCM during the initial formation cycle is critical for improving cycling stability.
• Optimizing the formation cycle voltage prevents detrimental side reactions and structural degradation.
• This strategy is essential for developing durable, high-energy-density lithium-ion batteries.