WEB Mechanical Degradation of Ni-rich Cathodes for High-Energy-Density Lithium-Ion Batteries: Experimental and Modeling ApproachTuesday (22.09.2020) 10:25 - 10:40 M: Modelling and Simulation 1 Part of:
Driven by the increasing demand for more environmental friendly transportation and efficient integration of renewable energy sources, Ni-rich metal layer oxides have received great attention as promising candidates for cathode materials of the next generation of lithium-ion batteries. A higher specific capacity, improved cost efficiency, and a reduction in the difficult to source cobalt content, are among the advantages of a higher Ni content in the cathode material. However, Ni‐rich cathodes face noticeable degradation during cycling due to the phase transition near charge-end, causing an abrupt anisotropic lattice shrinkage. The residual stress caused by the change in volume, induces a stress of secondary particles, which leads to crack propagation between primary particles. This can result in the detachment of primary particles from the secondary particle matrix and cause additional surface degradation at the cathode-electrolyte interface that is accompanied by a loss of capacity and an increase in the impedance.
New and aged Ni-rich Li[NixCoyMn1−x−y]O2 cathodes with varying number of cycles were electrochemically tested in order to characterize the discharge capacity and impedance at different states of aging. X-ray computer tomographic (CT) images with sub-micrometer resolution were used to analyze the microstructure of the electrodes and allow the quantification of the morphological changes of the materials.
A theoretical concept and a modeling approach are presented that take into account the aging effects and the associated evolution of the microstructure, as observed in the experimental results. Building on this, the performance of the battery cell in various aging states is simulated using an electrochemical cell model.