A Guide to Choosing Polymers for Use in Lithium-Ion Cells

Every commercial Li-ion cell contains several inactive components, most of which are composed of polymers. Many of these polymer-based inactive components, such as cell gaskets, jellyroll tapes, or even current collectors, utilize ester-based plastics. This study presents chemical screening experiments on ester-based plastics used in lithium-ion cells, specifically in the presence of alkoxides, which are common electrolyte degradation products generated in cells without effective electrolyte additives. These experiments demonstrate that ester-based polymers used in Li-ion cells can negatively impact their safety and performance as ester bonds are vulnerable to degradation by alkoxides. There is increasing interest in the battery industry to use metallized polymer current collectors, which typically consist of an ester-based polymer film coated on both sides with Cu or Al. This study demonstrates that the chemical stability of these metallized polymer current collectors in Li-ion cells is compromised when alkoxides are created. Finally, we provide recommendations for alternative polymers based on their chemical stability and market availability.