Effect of Applying a Carbon Coating on the Crystal Structure and De-/Lithiation Mechanism of Mn-Doped ZnO Lithium-Ion Anodes

The introduction of transition metal dopants such as Fe and Co in zinc oxide enables substantially enhanced reversible capacities and greater reversibility of the de-/lithiation reactions occurring. Herein, we report a comprehensive analysis of the electrochemical processes taking place in Mn-doped ZnO (Zn$_{0.9}$Mn$_{0.1}$O) and carbon-coated Zn$_{0.9}$Mn$_{0.1}$O upon de-/lithiation. The results shed light on the impact of the dopant chemistry and, especially, its coordination in the crystal structure. When manganese does not replace zinc in the wurtzite structure, only a moderate improvement in electrochemical performance is observed. However, when applying the carbonaceous coating, a partial reduction of manganese and its reallocation in the crystal structure occur, leading to a substantial improvement in the material's specific capacity. These results provide important insights into the impact of the lattice position of transition metal dopants—a field that has received very little, essentially no attention, so far.