Mitigating corrosion in batteries

Project description

The performances of batteries generally degrade with time due to different aging phenomena. In lithium-ion batteries, one of these phenomena involves corrosion of the aluminium current collectors. In the development of high-voltage positive electrode materials and/or new electrolytes for lithium-ion batteries, this corrosion of the aluminium current collector can become a performance limiting factor. It is therefore very important to find ways to increase the corrosion resistance of the aluminium current collector in different non-aqueous electrolytes. This project, which involves Uppsala University, Gränges, Graphmatec, RISE and Chalmers, consequently, aims at new approaches to address this problem based on an improved understanding of the reactions yielding aluminium corrosion in non-aqueous electrolytes. This knowledge will facilitate the development of lithium-ion batteries with longer lifetimes.

Organisations involved in the project

Description in a picture

Current status of the project

This project (which was ended in September 2023) was aimed at the development of approaches to increase the corrosion resistance of aluminium current collectors based on an improved understanding of the processes taking place at high potentials in non-aqueous electrolytes. Such an understanding is essential, for example, when using high-voltage cathodes in lithium-ion batteries.

During 2023 we further revisited the corrosion of aluminium current collectors in commonly used carbonate electrolytes (containing different concentrations of LiPF6, LiTFSI or LiFSI) at potentials up to 5.0 V vs. Li+/Li. We also studied the corrosion resistance of carbon coated aluminium current collectors in these electrolytes as well as the performance of aluminium current collectors coated with a positive electrode material (i.e., LiFePO4). Briefly, our electrochemical, SEM and XPS results indicate that the onset of the corrosion (or anodic dissolution) of the aluminium at about 3.5 V vs. Li+/Li stems from the oxidation of the carbonate solvents. This oxidation results in a production of protons which attack the native Al2O3 layer on the aluminium resulting in a decreased thickness of the Al2O3 layer. This increases the rate of the oxidation of the aluminium underneath the Al2O3 layer. In electrolytes containing a sufficient concentration of LiPF6 this oxidation of aluminium, however, gives rise to the formation of a new protecting surface layer containing AlF6 on top of the remaining Al2O3 layer. In electrolytes containing LiTFSI or LiFSI, the oxidation of the aluminium, on the other hand, gives rise to soluble aluminium complexes with TFSI- or FSI-. The latter explains the rapid corrosion of aluminium generally seen in LiTFSI and LiFSI electrolytes. The results also indicate that no major improvement was seen when using carbon coated aluminium current collectors. This means that efforts aimed at decreasing the aluminium corrosion problem should be focused on preventing the loss of the Al2O3 layer initially present on the surfaces of the aluminium current collectors.

Publications

Published paper:

  • Leif Nyholm, Tove Ericson, Ahmed S. Etman, “Revisiting the Stability of Aluminum Current Collectors in Carbonate Electrolytes for High-Voltage Li-ion Batteries”, Chem. Engin. Sci., 282, 2023, 119346.

Manuscripts in preparation

  • Ahmed S. Etman, Leif Nyholm,  ”Revisiting the Electrochemical Performance of LiFePO4 in Carbonate Electrolytes at Potentials up to 5 V vs. Li+/Li”.
  • Ahmed S. Etman, Leif Nyholm, ”On the Electrochemical Performance of LiFePO4 in LiFSI Electrolytes at Potentials up to 5 V vs. Li+/Li”.

Conference contributions

  • S. Etman, L. Nyholm, ”High-Voltage Li-ion Batteries: Insights into the Corrosion of Aluminum Current Collectors in Carbonate Electrolytes”, oral presentation at the 32nd ISE Topical Meeting, Stockholm, June 19 – 22, 2022.
  • S. Etman, L. Nyholm, ”Revisiting the Anodic Stability of Aluminum Current Collectors in High-Voltage Li-ion batteries”, oral presentation at the 244th ECS Meeting, Gothenburg, October 8-12, 2023.

Contact person

Leif Nyholm, Uppsala University
Leif.Nyholm@kemi.uu.se

Last modified: 2024-02-01