Density Functional Theory is applied to understand the large difference in surface reactivity of LiCoO 2 due to Al/Co substitution which is experimentally observed. In this way, we explore the SO 2 and CO 2 adsorption modes on the (110) surface of LiCoO 2 and α-LiAlO 2. For SO 2 adsorption, chemisorption produces sulfite species (for LiCoO 2 and α-LiAlO 2) and sulfate species (in the case of LiCoO 2). We demonstrate that the modification of the surface reactivity when Co 3+ ions are substituted by Al 3+ ions is due to a change from an adsorption mode controlled by redox properties for LiCoO 2 to a less energetically favorable adsorption mode controlled by acid-base properties for α-LiAlO 2. For CO 2 adsorption, the formation of carbonate species is observed for both compounds, illustrating the fundamental difference in the factors controlling SO 2 adsorption compared to CO 2 adsorption.