Anodic Dissolution of Aluminum in Sodium-Ion Batteries: A Comparison of Electrolyte and Solvent Composition

Abstract

The anodic dissolution behavior of aluminum was studied in various sodium-based electrolyte solutions using cyclic voltammetry and chronoamperometry. The aim was to investigate how different electrolyte and solvent compositions affect the dissolution process. The electrolyte solutions tested included 0.284 m NaBOB in TEP, 1.00 m NaPF6 in TEP, 1.00 m NaPF6 in EC:DEC, 1.00 m NaPF6 in diglyme, 1.00 m NaFSI in PC, and 1.00 m NaFSI in TEP. SEM imaging was also performed to analyze the morphological changes of the aluminum surface during the dissolution process.To emphasize any dissolution process, relatively large volumes (3-5 ml) of electrolyte solution was used in polytetrafluoroethylene beaker cells. A three-electrode configuration was used to obtain the desired accuracy in the electrochemical tests.Severe anodic aluminum dissolution was not observed below 5.3 V vs. Na+/Na in electrolyte solutions containing NaBOB in TEP, NaPF6 in TEP, NaPF6 in EC:DEC, or NaPF6 in diglyme. Anodic dissolution was, however, detected in electrolyte solutions containing NaFSI in PC and NaFSI in TEP, affirming that caution should be exercised when using FSI-anions with aluminum current collectors.1,2 Yet, the choice of solvent used with NaFSI appeared to influenced the anodic dissolution behavior of aluminum. Here, TEP seemed to suppress the initial dissolution, compared to PC.In summary, this study provides insights into the anodic dissolution behavior of aluminum in sodium-ion batteries, and highlights the significance of selecting appropriate solution compositions to mitigate potential anodic dissolution issues. The findings contribute to the understanding of the electrochemical behavior of aluminum in the context of sodium-ion batteries, and provides a foundation for further studies.The authors acknowledge The Swedish Energy Agency via project no. 50177-1, VINNOVA via projects no. 2022-01465 and 2019-00064 (Batteries Sweden), and H2020 research and innovation programme under Grant agreements No 958174 and 963542 for financial support.1. L. Otaegui, E. Goikolea, F. Aguesse, M. Armand, T. Rojo and G. Singh, J. Power Sources, 2015, 297, 168–173.2. A. Bitner-Michalska, A. Krztoń-Maziopa, G. Żukowska, T. Trzeciak, W. Wieczorek and M. Marcinek, Electrochim. Acta, 2016, 222, 108–115. Figure 1