Bridging particle-scale lithiation mechanisms and macroscopic performance in high-energy density Si anodes via time-resolved full 3D visualisation

Abstract

Anodes with high silicon (Si) content paired with nickel–manganese–cobalt (NMC) cathodes enable interesting prospects for Li-ion batteries well beyond the state of the art. However, when Si alloys with lithium (Li), it undergoes significant volume changes, raising the critical question of how exactly the electrode and individual particles respond to the lithiation dynamics and thus impact the battery performance. Here, we provide enhanced insights into the chemo-mechanical processes for cells with an 89 wt% Si anode paired with an NMC cathode. Electrode-scale deformation is linked with particle-scale mechanics by incorporating correlative multiscale 3D in situ investigations. Indeed, the combination of a sophisticated in situ cell setup with synchrotron X-ray computed nano-tomography together with AI-driven segmentation and 4D strain mapping allows us to detect pronounced spatial deformation and strain heterogeneities from the electrode to the single particle level. We observe complex lithiation behaviours beyond the core–shell mechanism, anisotropic strain evolution and mechanically distinct transformation modes across hundreds of particles. These 4D multiscale observations demonstrate that the failure risk in electrodes with high silicon content is determined primarily by localized stress accumulation and microstructural conditions rather than by volume expansion alone, underscoring the need for a mechanistic understanding of chemo-mechanical degradation in Si-based anodes.