Stereological Multi-Scale Modeling of Li-Ion Battery Particles: From 2D Cross-Sections to 3D Nano- and Micro-Structures
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Understanding the nano- and micro-structures of battery materials is essential for exploring their structure-property relationships, especially via simulations of electrochemical and mechanical behaviors. [1]. Lithium-nickel-manganese-cobalt-oxide (NMC811) particles represent an active material in battery cathodes with growing interest. The structure of NMC811 particles is investigated on two length scales: the micro-scale, encompassing particle shape and size (outer shell), and the nano-scale, addressing the inner crystallographic grain architecture. While the outer shell of particles can be measured at reasonable cost by X-ray computed tomography (3D nano-CT) the same is not feasible for the inner grain architecture utilizing e.g. 3D electron backscatter diffraction (EBSD) measurements. Therefore, grain architecture analysis often solely relies on imaging of 2D cross-sections. However, the results of these 2D measurements strongly vary by their location within the particle, due to the non-stationary grain architecture of NMC811. In this presentation, a stereological multi-scale model [2] is proposed that captures both the outer shell and non-stationary inner 3D grain architecture of NMC811 particles, see Figure 1. The model consists of two parts: first, the coarser scale of particles (outer shell) is modeled by random fields on the sphere [3]. Subsequently, the inner 3D grain architecture is modeled by a novel approach utilizing a generative adversarial network (GAN), which is used to fit a random 3D tessellation stereologically to 2D EBSD cross-sections. This approach overcomes the challenge of acquiring 3D EBSD data. Finally, both models are combined to generate synthetic, but realistic NMC811 particles, providing a valuable data basis for electrochemical and mechanical simulations [1]. By varying model parameters, this allows for the investigation of structure-property relationships for NMC particles that have not yet been measured or even produced [4].