By simulating Li -/0/+ vacancies at the LCO interface (Scheme 1A), we find that, under OCV, neutral Li vacancies are preferentially formed (i.e., Li + +e -leaves simultaneously) for all considered SOC (Figure ). In addition, the relative chemical potential of Li (Li + +e -), 𝜇 Li + +e -= 𝜇 Li , at the interface compared to bulk LCO is 0.10, 0.11 and 0.22 eV for x = 0.50, 0.75, and 1.00, respectively, meaning that surface vacancies are preferred over bulk (Figure ). In brief, the Li vacancy results showcase that a lower concentration of Li + is expected at the interface compared to the bulk at OCV, but also that desorption/adsorption of Li + from/to the LCO surface is accompanied by oxidation/reduction of interface Co 3+/4+ , corroborating the hypothesis of a coupled electron-ion mechanism of Li + transfer.