Solvent Effects on Kinetics and Electrochemical Performances of Rechargeable Aluminum Batteries

Abstract

The rechargeable aluminum batteries (RAB) have shown great potential for energy storage applications due to their low-cost and superior volumetric capacity. However, the battery performances are far from satisfactory owing to the poor kinetics of electrode reactions, including the solid-state ionic diffusion and interfacial charge transfer. The charge transfer reaction, typically the cation desolvation at the interface (Helmholtz plane), is crucial for determining the interfacial charge transfer, which induces the solvent effect in batteries but has not been explored in RABs. Herein, we provide a comprehensive understanding of solvent effects on interface kinetics and electrochemical performance of RAB by analyzing the desolvation process and charge transfer energy barrier. The pivotal role of solvent effects is confirmed by the successful application of Al(OTF)3-H2O electrolyte, which displays easy desolvation, low charge transfer resistance, and thus superior Al-ion storage performance over other electrolytes in our studies. In addition, based on the strong correlation between the calculated desolvation energy and charge transfer energy barrier, the calculation of dissociation energy of ion-solvent complex is demonstrated as an efficient index for designing electrolytes. The in-depth understanding of solvent effects provides rational guidance for new electrolyte and RAB design.