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.

We investigate the structural stability of metal oxides β-MnO2, TiO2 and VO2 (MO2) which are used as catalyst in metal air batteries, using the density functional theory (DFT) within the generalized gradient approximation (GGA). Their mechanical property was determined to show the stability trend of the metal oxides catalyst. Cell parameters of the bulk structures of the MO2 are in reasonable agreement with the experimental values (deviations of approximately 0.8% and -3.1% for a and c, respectively, and of 1.6 % in the cell volume). Phonon dispersion curves show that rutile (R) TiO2 is the most stable structure since it does not have vibrations in the negative frequencies.

Lithium manganese oxide (LiMn2O4) is one of the promising cathode material for lithium-ion batteries (LIBs), however, it suffers from capacity fading mainly due to surface manganese (Mn2+) ion dissolution during Charge/discharge processes. Although many studies focused on reducing Mn-dissolution, surface modification has proven to be an ideal method of reducing Mn2+ ion dissolution in secondary Li-ion batteries. In this study, the density functional theory calculations were carried out to study the bulk properties and investigate the effect of Nb surface doping on major LiMn2O4 spinel surfaces. Upon surface Nb doping, we observed a decrease in surface free energy as compared to the surface energies of pure surfaces, indicating that the surface stabilizes upon doping. However, the (001) surface remained the most stable facet, with a similar trend of increasing energies and decreasing stability, i.e. (001) < (011) < (111). Due to the stronger binding energy of Nb-O as compared to Mn-O, doping with Nb can suppress the Mn dissolution during intercalation and hence improve the electrochemical performance.