Polyethylene terephthalate (PET) tape is widely used by well-known lithium-ion battery manufacturers to prevent electrode stacks from unwinding during assembly. PET tape is selected since it has suitable mechanical and electrical properties, but its chemical stability has been largely overlooked. In the absence of effective electrolyte additives, PET can depolymerize into its monomer dimethyl terephthalate, which is an unwanted redox shuttle that induces substantial self-discharge in a lithium-ion cell. This study presents a chemical screening experiment to probe the PET decomposition mechanism involving in situ generated methanol and lithium methoxide from dimethyl carbonate, one of the most common electrolyte solvents in lithium-ion cells. By screening other polymers, it is found that polypropylene and polyimide (Kapton) are stable in the electrolyte. Finally, it is demonstrated that reversible self-discharge of LiFePO4–graphite cells can be virtually eliminated by replacing PET jellyroll tape with chemically stable polypropylene tape.
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This work was funded under the auspices of the NSERC/Tesla Canada Alliance Grant programme. A.A., K.T., M.D.L.G. and S.A. thank the Tamkivi Natural Sciences Foundation, the European Regional Development Fund via the Dora Plus scholarship programme, project no. TK141 (grant no. 2014-2020.4.01.15-0011), and the Estonian Research Council (grant no. PRG676), Killam Foundation, NSERC Postgraduate Scholarship programme and the Nova Scotia Graduate Scholarship programme for scholarship support. We acknowledge J. Dahn for obtaining the 402035-sized pouch cells with PP tape.
The authors declare no competing interests.
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Adamson, A., Tuul, K., Bötticher, T. et al. Improving lithium-ion cells by replacing polyethylene terephthalate jellyroll tape. Nat. Mater. 22, 1380–1386 (2023). https://doi.org/10.1038/s41563-023-01673-3