Role of the solvent in the activation of Li2S as cathode material: a DFT study

JUAN J VELASCO; PATRICIO VÉLEZ; MARTIN E ZOLOFF MICHOFF; VISINTIN A.; DANIELE VERSACI; SILVIA BODOARDO; GUILLERMINA L LUQUE ; EZEQUIEL LEIVA

JOURNAL OF PHYSICS CONDENSED MATTER

IOP PUBLISHING LTD

Lugar: Londres; Año: 2021 vol. 33

0953-8984

Lithium-sulfur batteries are considered one of the possible next-generation energy-storagesolutions, but to be commercially available many drawbacks have yet to be solved. Onesolution with great potentiality is the use of lithium sulfide as cathode material since it can becoupled to Li-free anodes, such as graphite, Si or Sn. Nevertheless, Li2S, like sulfur, iselectronically and ionically insulating, with a high activation potential for its initial oxidationstep. To overcome this issue, different strategies have been explored, one of them being theuse of catalytic surfaces. In the present article, we study using first principles calculations theeffect of the dielectric constant of the solvent on the activation energy of the cleavagereaction of Li2S on different catalytic surfaces. To the best of our knowledge, this is the firsttime that such a study is undertaken. We find that the effect of the solvent should be twofold:On one side, it should decrease the interaction between the Li2S molecule and the surface.On the other side, since the species arising in the dissociation reaction are charged, thesolvent should decrease the activation barrier for the dissociation of the Li2S molecule, whencompared with the reaction in vacuum. These theoretical findings arediscussed in connectionwith experimental results from the literature, where the behaviour of the Li-S cathode isstudied in different solvents.