Increasing lithium content is shown to be a successful strategy for designing new cathode materials. In layered Li$_x$Ni$_{2–4x/3}$Sb$_{x/3}$O$_2$ (x = 1.00–1.15), lithium excess improves both discharge capacity and capacity retention at 1C. Structural studies reveal a complex nanostructure pattern of Li–Sb and Ni–Sb ordering where the interface between these domains forms the correct local configuration for good lithium mobility. The <1 nm Li–Sb stripe domains and their interfaces thereby effectively act as nanohighways for lithium diffusion.