Computational Study of the Enhancement of Graphene Electrodes for Use in Li-Ion Batteries via Forming Superlattices with Transition Metal Dichalcogenides.

In our study, we examined nine transition metal dichalcogenide (TMDC)-graphene superlattices as potential Li-ion intercalation electrodes. We determined their voltages, with ScS 2 -graphene in T- and R-phases showing the highest at around 3 V, while the others ranged from 0 to 1.5 V. Most superlattices exhibited minimal volumetric expansion (5 to 10%), similar to NMC (8%), except for SnS 2 -T and NiS 2 -T, which expanded up to nearly 20%. We evaluated their capacities using a stability metric, E IS , and found that ScS 2 -T, ScS 2 -R, and TiS 2 -T could be intercalated up to two Li ions per MX 2 unit without decomposing to Li 2 S, yielding capacities of 306.77 mA h/g for both ScS 2 phases and 310.84 mA h/g for TiS 2 -T, roughly equivalent to LiC 2 . MoS 2 -T could accept Li up to a limit of a = 15/16 in Li a MoS 2 C b , corresponding to a capacity of 121.29 mA h/g (equivalent to LiC 4 ). Examining the influence of graphene layers on MoS 2 -T, we observed a voltage decrease and an initial E IS decrease before effectively flat lining, which is due to charge donation to the middle graphene layer, reducing the electron concentration near the TMDC layer. As graphene layers increased, overall volume expansion decreased with Li intercalation, which is attributed to the in-plane expansion changing. Our results underscore the potential of TMDC-graphene superlattices as Li-ion intercalation electrodes, offering low volumetric expansions, high capacities, and a wide voltage range. These superlattices all show an increase in the capacity of the graphene.