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Improving lithium-ion cells by replacing polyethylene terephthalate jellyroll tape
Anu Adamson1, Kenneth Tuul2,3, Tom Bötticher2
1Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada.
Nature Materials
|September 22, 2023
Summary
Polyethylene terephthalate tape in lithium-ion batteries can depolymerize, causing self-discharge. Replacing it with stable polypropylene tape eliminates this issue in LiFePO4-graphite cells.
Area of Science:
- Materials Science
- Electrochemistry
- Chemical Engineering
Background:
- Polyethylene terephthalate (PET) tape is crucial for lithium-ion battery assembly, preventing electrode unwinding.
- PET's chemical stability in battery electrolytes is often overlooked, despite its importance.
- PET depolymerization can lead to self-discharge via redox shuttle formation.
Purpose of the Study:
- To investigate the chemical stability of PET in lithium-ion battery electrolytes.
- To identify the decomposition mechanism of PET under typical cell conditions.
- To find alternative stable polymers for battery manufacturing.
Main Methods:
- Chemical screening experiments were conducted to probe PET decomposition.
- In situ generated methanol and lithium methoxide from dimethyl carbonate were used.
- Polypropylene and polyimide (Kapton) were screened for electrolyte stability.
Main Results:
- PET depolymerizes into dimethyl terephthalate, acting as a redox shuttle.
- Methanol and lithium methoxide are key intermediates in PET decomposition.
- Polypropylene and polyimide demonstrated excellent stability in the electrolyte.
Conclusions:
- PET tape poses a risk of self-discharge in lithium-ion batteries due to chemical instability.
- Polypropylene and polyimide are viable, stable alternatives to PET tape.
- Replacing PET tape with polypropylene tape eliminates reversible self-discharge in LiFePO4-graphite cells.
