Mechanism of capacity fading in the LiNi_0.8Co_0.1Mn_0.1O₂ cathode material for lithium-ion batteries

Understanding the capacity fading mechanism of the LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode materials is crucial for achieving long-lasting lithium-ion batteries with high energy densities. In this study, we investigated the factors affecting the capacity fading of NCM811 during repeated cycling at high temperatures. We found that the change in the c-axis length during charging and discharging is the main cause of the formation and propagation of microcracks in the primary particles of NCM811. In addition, the electrolyte is decomposed on the microcrack surfaces and, consequently, by-products are formed on the particle surface, increasing the impedance and resulting in poor electronic and ionic connectivity between the primary particles of NCM811. In addition, the transition metals in the NCM811 cathode material are dissolved in the electrolyte from the newly formed microcrack surface between primary particles. Therefore, the electrolyte decomposition and transition metal dissolution on the newly formed surface are the major deteriorative effects behind the capacity fading in NCM811.