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 Mn 3 O 4 on heating at 450 and 550 °C and the cubic structure of Mn 2 O 3 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 Mn 2 O 3 and Mn 3 O 4 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 Mn 2 O 3 and Mn 3 O 4 is predicted. The findings indicated that 10 lithium atoms adsorb on Mn 2 O 3 , whereas 5 lithium atoms adsorb on Mn 3 O 4 when saturation is taken into account. The storage capacities of Mn 2 O 3 and Mn 3 O 4 are estimated to be 1697 and 585 mAh g -1 , respectively. The maximum value of lithium insertion voltage per Li in Mn 2 O 3 is 0.93 and 0.22 V in Mn 3 O 4 . Further, the diffusion coefficient values are found as 2.69 × 10 -9 and 2.65 × 10 -10 m 2 s -1 for Mn 2 O 3 and Mn 3 O 4 , 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 Mn 2 O 3 and Mn 3 O 4 , respectively. The findings of the work revealed high specific capacity, low Li diffusion energy barrier, and low open circuit voltage for the Mn 2 O 3 -based anode for use in LIBs.