Mechanical fracture is commonly regarded as one of key ingredients affecting the reliability of Li-ion battery electrode. In order to avoid the rapid mechanical collapse of electrode, attempts have been made to work on obtaining the accurate critical fracture condition for electrode particle with initial cracks under diffusion-induced stress produced in Li-ion intercalation and deintercalation process. However, considering the integrated fracture process on pristine particle, it is crucial to assess crack initiation phase in fracture analysis so as to obtain the comprehensive failure margins of three-dimensional primary particle. This paper evaluates the diffusion induced stress for NCM primary particle morphology under lithiation-delithiation condition, where the coevolving process of diffusion and stress generation is implemented with both diffusion driven approach and chemical potential driven approach by developing finite element subroutines. Based on the coupled diffusion-stress analyses, crack onset and growth of ternary cathode particle are studied by using ABAQUS extended finite element method (XFEM) with appropriate mesh density and verified by experimental observation. The integrated crack initiation and fracture margins with various current densities and particle dimensions are plotted. The innovative equations to acquire critical particle dimension for crack initiation and fracture under applied electrochemical load are established, which are significant for evaluating particle status. Associating the critical failure diagram with the size distribution of particles in NCM electrode samples, the failure proportion is presented for electrode in microscale. The impact of diffusion on active material property is also investigated comprehensively in stress evolution and fracture analysis.
|Journal||International Journal of Mechanical Sciences|
|Publication status||Accepted/In press - 9 Mar 2020|
- li-ion battery electrode
- diffusion induced stress
- crack initiation
- crack propagation
- critical margins