Abstract
Using a thick NMC811 (LiNi0.8Mn0.1Co0.1O2) electrode as an example, we present a macro-to nanoscale 2D and 3D imaging analysis approach coupled with 4D (space + time) computational modeling to probe its degradation mechanism in a lithium-ion bat-tery cell. Particle cracking increases and contact loss between parti-cles and carbon-binder domain are observed to correlate with the cell degradation. This study unravels that the reaction heterogene-ity within the thick cathode caused by the unbalanced electron con-duction is the main cause of the battery degradation over cycling. The increased heterogeneity in the system will entail more cathode regions where the degree of active material utilization is uneven, leading to higher probabilities of particle cracking. These findings shed light on the crucial role of the electronic and ionic transporta-tion networks in the performance deterioration of the thick cathode. They also provide guidance for cathode architecture optimization and performance improvement.