The development of advanced Li-ion battery would require innovative approaches to improve the present performances, while lowering the environmental footprint and price of their fabrication. In this scope, we are currently carrying out different projects to consider the electrode materials as well the process to make the batteries. This presentation will focus on the second aspects, which concerns the development of a solvent-free process to make composite electrodes using an owned patented process by Hutchinson [1]. Currently, most of the electrode fabrication involves the use of organic solvent (typically N-methyl-2-pyrrolidone, NMP, which is toxic). Life cycle analysis studies of the LiB manufacturing process showed that this type of electrode preparation accounts for a significant portion of their overall environmental imprint [2]. While the use of water, instead of NMP, would be preferable to minimize this impact [3], a solvent-free electrode manufacturing consumes less energy in comparison to solvent-based methods [4].

Different electrode formulations were prepared by the dry process. The mechanical, electrical and electrochemical properties in half cells were assessed and compared to composite electrodes obtained by doctor blade coating using the classical PVdF binder. The different steps of the dry process (mixing, lamination and adhesion to current collectors) were studied and optimized separately to reach the maximum loading, while ensuring good power performances. The Ragone plots for each electrode, tested in half cells, were evaluated and the best formulation was retained for the full cell manufacture. The performances of LiFePO₄/Li₄Ti₅O₁₂ batteries are comparable to our best electrodes made with PVdF. The different aspects of the process will be discussed in this presentation.

References

[1] Ph. Sonntag, D. Aymé-Perrot, B. Dufour, Arnaud Prébé, N. Garois, Patent WO2015124835A1

[2] G. Majeau-Bettez, T.R. Hawkins, A.H. Stromman, Environmental Science & Technology, 2011, 45, 4548.

[3] M. Zackrisson, L. Avellan, J. Orlenius, Journal of Cleaner Production, 2010, 18, 1519.

[4] Environmental Protection Agency “Lithium-ion batteries and nanotechnology for electric vehicles: A life cycle assessment,” EPA 744-R-12-001, 2012.