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Cell Design

Inactive Cell Component Material Optimization

Replacing PET tape with PP tape to avoid degradation Researchers at Dalhousie University analyzed the chemical stability of materials of various common tapes used in lithium ion batteries: polyethylene terephthalate (PET) and polypropylene (PP). Chemical degradation products of the tape were investigated with FTIR throughout cycling of LFP/graphite pouch cells under various conditions. PET tape exhibited significant degradation, leading to the generation of dimethyl terephthalate (DMT). This byproduct from PET decomposition was identified as a redox shuttle, contributing to substantial self-discharge within LIBs. PP tape demonstrated robust chemical stability, exhibiting negligible degradation products under similar stress conditions. The authors mention that polyimide (PI/Kapton) tape is also chemically stable, but it is of substantially higher cost than PP tape.

Capacity losses of cells using PET and PP tape formed at 70°C and stored at 40°C (where 2VC refers to 2% vinylene carbonate in EC:DMC) Transitioning from PET to PP tape in LIB assembly will help mitigate the adverse effects of PET degradation.

Academia | P. 235 Source: Adamson, A., Tuul, K., Bötticher, T. et al.

PET Tape is used to contain windings and cover aluminum in a cylindrical cell

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