First-Principles Studies on the Structural Stability of Spinel ZnCo2O4 as an Electrode Material for Lithium-ion Batteries

Systematic first principles calculations were performed for ZnCo2O4 to clarify its structural and electronic properties, and particularly the structural stability as an electrode material for lithium-ion batteries. For samples with low Li concentration, e.g., LinZnCo2O4 with n < 1, Li atoms take the center of oxygen octahedra and may diffuse rapidly. Structure distortions and volume expansions can be observed in LinZnCo2O4 with n > 1 and amorphous structures eventually prevail. The AIMD simulations for Li9ZnCo2O4 suggest the formation of Li2O, Co3O4 and LiZn local compounds or alloys. In particular, the formation of Zn-Co aggregations and the losing of ZnO pairs are identified as the possible reasons that are responsible to the Li capacity fading in ZnCo2O4 anodes.