Phase-Dependent Properties of Manganese Oxides and Applications in Electrovoltaics.

This study reports first-principles predictions as well as experimental synthesis of manganese oxide nanoparticles under different conditions. The theoretical part of the work comprised density functional theory (DFT)-based calculations and first-principles molecular dynamics (MD) simulations. The extensive research efforts and the current challenges in enhancing the performance of the lithium-ion battery (LIB) provided motivation to explore the potential of these materials for use as an anode in the battery. The structural analysis of the synthesized samples carried out using X-ray diffraction (XRD) confirmed the tetragonal structure of MnO on heating at 450 and 550 °C and the cubic structure of MnO on heating at 650 °C. The structures are found in the form of nanoparticles at 450 and 550 °C, but at 650 °C, the material appeared in the form of a nanoporous structure. Further, we investigated the electrochemical functionality of MnO and MnO as anode materials for utilization in LIBs via MD simulations. Based on the investigations of their electrical, structural, diffusion, and storage behavior, the anodic character of MnO and MnO is predicted. The findings indicated that 10 lithium atoms adsorb on MnO, whereas 5 lithium atoms adsorb on MnO when saturation is taken into account. The storage capacities of MnO and MnO are estimated to be 1697 and 585 mAh g, respectively. The maximum value of lithium insertion voltage per Li in MnO is 0.93 and 0.22 V in MnO. Further, the diffusion coefficient values are found as 2.69 × 10 and 2.65 × 10 m s for MnO and MnO, respectively, at 300 K. The climbing image nudged elastic band method (Cl-NEB) was implemented, which revealed activation energy barriers of Li as 0.30 and 0.75 eV for MnO and MnO, respectively. The findings of the work revealed high specific capacity, low Li diffusion energy barrier, and low open circuit voltage for the MnO-based anode for use in LIBs.