Rechargeable Al batteries (RAB) are promising candidates for safe and environmentally sustainable battery systems with low-cost investments. However, the currently used aluminum chloride-based electrolytes present a significant challenge to commercialization due to their corrosive nature. Here, we report for the first time, a novel electrolyte combination for RAB based on aluminum trifluoromethanesulfonate (Al(OTf)3) with tetrabutylammonium chloride (TBAC) additive in diglyme. The presence of a mere 0.1 M of TBAC in the Al(OTf)3 electrolyte generates the charge carrying electrochemical species, which forms the basis of reaction at the electrodes. TBAC reduces the charge transfer resistance and the surface activation energy at the anode surface and also augments the dissociation of Al(OTf)3 to generate the solid electrolyte interphase components. Our electrolyte's superiority directly translates into reduced anodic overpotential for cells that ran for 1300 cycles in Al plating/stripping tests, the longest cycling life reported to date. This unique combination of salt and additive is non-corrosive, exhibits a high flash point and is cheaper than traditionally reported RAB electrolyte combinations, which makes it commercially promising. Through this report, we address a major roadblock in the commercialization of RAB and inspire equivalent electrolyte fabrication approaches for other metal anode batteries.

The role of nanoparticle shape in the interaction and adsorption of organic molecules on the particle surface is an unexplored area. On the other hand, such knowledge is not only...

We use molecular dynamics simulations and the adaptive biasing force method to evaluate the potential of mean force between two carbon nanotubes (CNTs), with each surface modified by an adsorbed sodium-polystyrene sulfonate (Na-PSS) polyanion, in aqueous electrolyte media. Changes in the electrolyte concentration and counter-ion valence can lead to qualitative changes in the interactions between polyelectrolyte-modified CNTs. We show that in the presence of monovalent NaCl salt, a long-range screened electrostatic repulsion exists between CNTs. This repulsion can be described by a generalized Derjaguin− Landau−Verwey−Overbeek interaction that accounts for anisotropy of charged cylindrical colloids. In contrast, an attraction between CNTs is observed in the presence of divalent MgCl 2 salt. The attraction is attributed to ion-pair correlations between anionic SO 3 − groups, on different PSS chains, induced by Mg 2+ counter ions acting as bridges between the SO 3 − groups. However, in the salt-free case where divalent Mg 2+ counter ions are considered instead of the Na + counter ions, condensation of Mg 2+ counter ions on the adsorbed PSS chain results in the neutralization of surface charge and leads to a short-range steric repulsion between the CNTs. Thus, our simulations show that qualitatively different interactions, either short-range steric repulsion, long-range repulsion or attraction, can arise between PSS-modified CNTs based on counterion valence and electrolyte concentration.

The effect of curvature and relative orientation between two curved graphene sheets in aqueous media is quantified by calculating the potential of mean force using molecular dynamics simulations and thermodynamic perturbation. The potential of mean force between two curved graphene sheets is found to scale as U ∼ Rd, where R is the sheet radius of curvature and d is the inter-sheet distance. Further, a simple analytical calculation based on classical Hamaker theory and the Derjaguin approximation also arrives at the same scaling of interaction energy with respect to R and d. For the case where a misorientation, θ, exists between the two curved graphene sheets, the simulation results strongly suggest an inverse dependence of the potential of mean force on sin θ for θ > 30°. This result is very similar to the scaling predicted by the Derjaguin approximation for two cylinders crossed at an angle θ with respect to each other.

Molecular dynamics (MD) simulations were utilized to explore the energetics of formation of a graphene−carbon nanotube (CNT) hybrid in an aqueous environment, resulting from the intercalation of a single-walled CNT into a gallery defined by two parallel graphene sheets. It was found that the formation of a graphene− CNT hybrid can be divided into three processes involving (a) exfoliation of graphene sheets by repulsive interactions, (b) intercalation of a CNT into the graphene gallery associated with an activation energy barrier, and (c) spontaneous self-assembly/association of constituent CNT and graphene sheets driven by hydrophobic interactions or electrostatic attraction, leading to the formation of a three-dimensional hybrid. In contrast with pristine graphene sheets, ionic functionalization makes graphene sheets more hydrophilic and enhances their exfoliation in water, resulting in a significant lowering of the CNT intercalation barrier by nearly 150 kcal/mol. The simulations predict that the lowest intercalation barriers would arise for cases where both the energetic cost for graphene exfoliation and steric repulsions between the incoming CNT and graphene sheets are the lowest. Once the CNT moves past the barrier, its further incorporation into the graphene gallery is spontaneous and is assisted by strong hydrophobic interactions between the CNT and graphene surfaces. The most stable hybrid complex was observed when the CNT and graphenes are functionalized with oppositely charged ionic groups.