Elasto-plastic properties. The anisotropic stiffness matrix of the NMC811 cathodes at the fully lithiated and delithiated state is obtained using environmental nanoindentation experiments and first-principles calculations . The observed anisotropic elastic behaviour in layered oxide materials is attributed to the week bonding along the c-axis compared to the a-axis . The slip strength along the basal plane of NMC811 cathode materials is assessed by an indentation-based test method . Isotropic elastic and elasto-plastic mechanical properties are assumed for solid electrolytes within the composite cathode .