First-principle investigation on stability of Co-doped spinel λ-Mn_4−xCo_xO₈

Abstract

The mechanism of stability of Co-doped spinel λ-MnO₂ that is referred to as spinel Li_xMn₂O₄ (x=0) was studied by using the first-principle calculation method. The total energy and formation enthalpy can be decreased remarkably due to the Co substation, resulting in a more stable structure of λ-Mn_xCr_2−xO₄. The bond order and DOS analysis were given in detail to explain the nature of stability improvement. The calculated results show that as the content of Co dopant increases, the bond order of Mn—O becomes larger and the peak of density of states around Fermi level shifts toward lower energy. The charge density distribution illustrates that the Mn—O bonding is ionic and partially covalent, and the covalent Mn—O bonding becomes stronger with the increase of Co dopant content. The results confirm that the Co-doping will enhance the stability of λ-MnO₂ and hence improve the electrochemistry performance of Li_xMn₂O₄.

Keywords

first-principles / stability / electrochemical performance / Co-doped λ-MnO₂