Unveiling the Interplay of Structural and Electrochemical Degradation of LiNi$_{0.85}$Mn$_{0.05}$Co$_{0.05}$O$_{2}$ Cathode Material for Li-Ion Batteries

Nickel-rich layered oxides, crucial for high-energy-density Li-ion batteries, face challenges in cycle life due to intricate chemomechanical degradation. This study pioneers a comprehensive approach, integrating nano X-ray computed tomography and advanced electrochemical methods, to untangle the interplay of degradation mechanisms in complex composite electrodes. The evolution of cracking in Nickel-rich cathodes is meticulously quantified under diverse operating conditions. Surprisingly, our findings unveil that, contrary to conventional wisdom, crack formation is not the primary driver of capacity decay in Nickel-rich cathodes. Instead, the limiting factor emerges from the interplay between cycling-induced cracks and a progressively growing resistivity. Cracks, amplifying electrochemically active surfaces, foster side reactions, elevating resistance, and consequently diminishing capacity and current rate capability. This novel insight redirects attention to the dynamic resistivity growth, pinpointing operating conditions as a critical contributor. This work not only advances our understanding of Nickel-rich cathode degradation but also provides a framework for strategic mitigation strategies.