Estimation of Crack Formation By Digital-Twin Structure of a Single Secondary Particle

Abstract

Most of the recently commercialized active materials for lithium-ion batteries (LiB) adopt secondary particles, and most of them are designed by evaluating cell-level electrochemical properties. Therefore, the relationship between particle design and battery performance is not properly understood because it is not possible to grasp the intrinsic properties of the electrode active material. Therefore, a single particle measurement technique has been developed in which a gold or platinum filament having a diameter of several tens of microns is directly contacted with a single particle to evaluate the single particle electrochemical properties. However, since it is a non-sealed battery system, only less-volatile electrolytes can be applied. Also, the experiment is difficult because the contact between particle and filament can easily break down with small vibration. Additionally, there are a lot of particle design parameters such as particle shape, size, and size distribution. Moreover, with operating conditions, the particle design needs to be changed. So, it is challenging to cover all cases by experiment.In this study, digital-twin structure of a single secondary particle was formed using focused ion beam / scanning electron microscope. Using the digital-twin structure, digital-twin electrochemo-mechanical model was developed and more than 99% of accuracy was secured by comparing the voltage profiles with result of single particle measurement technique. Using the well-matched model. Operando analysis of electrochemical properties (State of Lithiation, overpotential, potential, and concentration) and mechanical properties (von Mises stress and strain energy density) were performed. The strain energy density can be the criteria to determine the crack formation by comparing with the fracture toughness which is the strain energy density when the fracture occurs.