A novel method to solve the problem of distortion in commercial lithium-ion pouch cells

In this paper, a novel method to solve the problem of distortion in commercial lithium-ion pouch cells is introduced. The new approach mainly involves the application of poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) binder onto the surface of the separator in a pretreatment process. This binder enhances the strength of the adhesion between the positive electrode and the separator during the hot pressing process. The resulting lithium-ion pouch cell exhibits improved cycle performance and reduced cell thickness swelling. The relationship between the amount of binder coated onto the PP (polypropylene) substrate and the cycle performance was explored, and the optimal amount of binder coating was estimated to be 0.15 mg/cm2. Including a composite separator in commercial lithium-ion pouch cells reduces the internal stress between the electrode and the separator and can improve the stability of the jelly-roll structure during cycling, as it balances out the internal stress distribution.