Oxygen Doping Enhanced Lithiation in MgCl2 for Battery Applications

Li‐ion batteries are key electric energy storage devices due to high energy density and long cycling lifetime, being widely used in portable electronic devices and large scale systems. In spite of stable cycling performance, the graphite electrode suffers from a low capacity. It is demonstrated in this context that oxygen doping makes MgCl2 electrochemically active. Importantly, the doped structure delivers a high capacity of 941 mAh g−1 for the bulk and 1098 mAh g−1 for the monolayer. The diffusion barrier is calculated to be lower than 0.6 eV. Hexagons and octahedrons composed of Li and Cl atoms are gradually formed with increasing Li coverage, breaking the Mg–Cl bonds. Oxygen doping makes MgCl2 electrochemically active because of strong interaction with Li. The bulk and monolayer deliver high Li specific capacities of 941 and 1098 mAh g−1, respectively. The diffusion barrier for the bulk is calculated to be 0.6 eV. O doping may be achieved by O annealing because of a low reaction enthalpy.