Impact of Lithium-Ion Ordering on Surface Electronic States of LixCoO2

LixCoO2 exhibits intriguing electronic properties due to a strong electron correlation and complex interplay between Co and Li ions. However, fundamental understanding of the nanoscale distribution of Li ions and its effect on the electronic properties remains unclear. We use scanning tunneling microscopy and density functional theory to elucidate the degree of LixCoO2 surface electronic state modification that can be achieved by Li ordering. The surface Li ions are highly mobile and preferentially form a (1 x 1) hexagonal lattice, whereas the surface CoO2 layer shows metallic and insulating phases, indicating the coexistence of ordered and disordered Li ions in the subsurface layer. These results provide evidence of novel electronic properties produced by spatially inhomogeneous Li-ordering patterns.