Enhancing the lifetime of Li-ion batteries (LIBs) is essential to support renewable energy deployment and electric mobility. One promising approach is the functionalization of the separator—typically inert—to trap degradation products and extend battery lifespan. However, such modifications may also affect Li-ion transport, with potential consequences for cell performance. To assess these effects, we propose a multiscale structural investigation of both pristine and functionalized hybrid electrospun separators (HES), composed of micrometre-scale fibrous mats. Using ptychographic X-ray computed tomography on ID16A, we will reconstruct high-resolution 3D volumes of individual HES fibres (~500 nm thick). These datasets will serve as input for flux-based simulations to quantify local tortuosity and evaluate how it is modified by functionalization. This will provide key insights into structure–transport relationships in next-generation separators and inform future material design.