ELECTROCHEMICAL PERFORMANCE OF SODIATED 1,4-BENZOQUINONE CONFORMERS

Abstract

The exploration on the redox properties of sodiated quinone molecules as organic cathode material in sodium-ion batteries has been comprehensively studied. As the electrochemical performance of the cathode material is known to depend on the intrinsic molecular properties such as conformations, the present work focuses on the redox properties of sodiated 1,4-benzoquinone (1,4-BQ) conformers employing the density functional theory. Such investigation on the sodiated structures might provide insight on the discharge state of the puckered conformers. The 38 conformers of 1,4-BQ (2 chairs, 6 boats, 6 skew-boats, 12 half-chairs, 12 envelopes) constructed from the torsion angles given by Berces et al. are optimized at B3LYP/6–311 + G(d,p) level of theory and their structural propensities during the reduction process are explored. The influence of puckering over the charge distribution of neutral, anionic and sodiated structures is analysed using the natural bond orbital method. The electrochemical performance of Na incorporated conformers is explored through the calculation of electron affinity, change in Gibbs free energies and redox potentials. The conductor-like polarizable continuum model (C-PCM) is used to include the solvation effects of the electrolyte such as ethylene carbonate. A good correlation between the conformers with more negative lowest unoccupied molecular orbital (LUMO) energies and their redox potentials and electron affinity is observed. Noticeable variation in the frontier energies and redox potentials of the sodiated quinone conformers emphasize the significance of intrinsic molecular level properties to play a major role in the overall electrochemical performance of quinone-like electrode materials in sodium-ion batteries.