Structural and electronic properties of β-MnO2 employing DFTB technique

Abstract

MnO2 is presently under massive review for its capacitance properties. MnO2 recrystallizes into several crystallographic structures such as α, β, γ, δ, and λ structure. These structures vary in the way MnO6 octahedra are connected, they possess tunnels or interlayers with gaps of different magnitudes. However, upon lithium intercalation in β-MnO2, LiMnO2 suffers from capacity loss due to undesirable structural phase transformation into spinel like LixMn2O4. One of the major demands is to modify and strengthen the structural stability of MnO2 to prevent phase transformation during lithium intercalation and rapid capacity fading during cycling. DMol3 is a density functional theory-based program used to calculate the lattice parameter of ferromagnetic MnO2. After successfully parameterized MnO2, the lattice parameters were compared with the results from experiments. Density functional tight-binding (DFTB) was employed to investigate the electronic properties of MnO2 such as density of states (DOS) and band structures. The DOS was calculated to check the conductivity of MnO2. The electronic band structures calculated indicate the absence of a gap at the Fermi level, thus MnO2 is metallic. These findings are important in preserving the crystal structure of LiMnO2 and the maintenance of capacity during cycling.