Cation desolvation on a model electrode surface: a story of commitment and breakup
H. Rasheev*, R. Stoyanova* and A. Tadjer*
The ever-growing usage of rechargeable batteries in the endless assortment of portable devices demands better and safer batteries. At the moment, the broadest application in smart electronics and transport vehicles find Li-ion batteries, but their cost and environmental impact encourage fervent on-going development of new electrode and electrolyte materials . One attractive approach is the partial substitution of Li+ as charge carrier with ions of more abundant elements like Na and Mg, resulting in the so-called hybrid cells. The efficiency of such hybrid batteries depends, among others, on the processes taking place at the electrode-electrolyte interface. Such process is the desolvation of the metal ions, occurring simultaneously with adsorption on the electrode surface. Molecular modelling is a suitable tool for investigating these processes at atomic-level resolution. In our study, we employ periodic Density Functional Theory calculations to assess the interactions of a model (111) surface of lithium titanate (Li4Ti5O12) with single-ion or dual-ion clusters of Li+, Na+ and Mg2+ with ethylene carbonate using PF6¯ as counterion. The PBE approximation for the exchange and correlation functional and the PAW method for the initial electronic wave functions were applied as implemented in VASP. Preferred adsorption sites on the surface were identified. The desolvation energies of the cations were evaluated and comparison with free-standing ion-solvent clusters was made and discussed . The on-surface behaviour of the counterion and the effect of its presence on the desolvation of scantily solvated single/dual-cation complexes were also modelled and the proceeding decomposition reactions were described.
The authors from CARiM’s Research Team are noted with *