Mechanistic understanding of intergranular cracking in NCM cathode material: Mesoscale simulation with three-dimensional microstructure

Abstract: Intergranular cracking in the agglomerated form of secondary particle has been regarded as a major cause for mechanical degradation in layered oxide cathode materials for Li-ion battery but its detailed mechanistic origin linked to their mechanical properties is still lack of understanding. In this study, mesoscale simulation based on describing interaction between primary particles with combined model of the shifted force Lennard-Jones potential and the granular Hertzian model is established to construct the microstructure for the secondary particle of the cathode materials. Optimized parameters for each model are developed to compute the mechanical properties based on the response from the nano-indentation and the uniaxial tensile test. Furthermore, adhesion between primary particles is modified to examine its sensitivity to the different mode of deformations and it shows that under tension, increase in adhesion can significantly strengthen the structure along with larger brittleness while the response from the localized compression (nano-indentation) is shown to be much less sensitive. In addition, structural change during repeated volume expansion/contraction induced from the electrochemical cycling is investigated, indicating that enhancing the particle adhesion can prevent the propagation of intergranular cracking.