Effect of MgO NPs doping on the optoelectronic and electrochemical behavior of polyethylene oxide (PEO) nanocomposite polymer electrolyte

Nanocomposite polymer electrolytes provide new alternatives for rechargeable magnesium ion batteries. Magnesium is a divalent charge carrier with several advantages over other metals, such as Li or Na ions for battery applications. Magnesium batteries have gained increasing attention because of their low-cost and reliable technology. In this study, nanocomposite polymer electrolytes based on polyethylene oxide (PEO)₈ and magnesium oxide (MgO) nanoparticles doped ${\left(\text{PEO}\right)}_8$-MgO-${\left(\text{PEO}\right)}_8$ were investigated using Gaussian 09 software with Gauss View 6.0 to explore the system's structural, electronic, and electrochemical properties. The density functional approach has been utilized with the B3LYP method and 6-31G basis set to optimize the structures and obtain their properties such as XRD, UV–vis-nir, IR, Raman, NMR, Mulliken charge analysis, and Molecular electrostatic potential. The band gap of pure PEO, calculated using the HOMO-LUMO energy gap, was found to be 6.28 eV, indicating insulating properties. Upon the addition of MgO nanoparticles, the band gap of ${\left(\text{PEO}\right)}_8$-MgO-${\left(\text{PEO}\right)}_8$ decreased to 4.96 eV, suggesting slightly high electronic conductivity. Molecular electrostatic potential (MEP) mapping demonstrated a uniform charge density distribution in ${\left(\text{PEO}\right)}_8$-MgO-${\left(\text{PEO}\right)}_8$, highlighting favorable sites for ionic interactions. Mulliken population analysis showed an increase in electron density on the polymer backbone, confirming the Lewis base behavior of PEO in the nanocomposite polymer electrolytes system. The results from DFT calculations, combined with insights into structural and electrochemical behavior, explore the potential of ${\left(\text{PEO}\right)}_8$-MgO-${\left(\text{PEO}\right)}_8$ nanocomposites as efficient solid-state polymer electrolytes. This study provides a theoretical foundation for designing advanced polymer-based materials for next-generation energy storage devices.