Changes of adhesion properties for negative electrode and positive electrode under wet conditions and different states of charge

Abstract

Debonding often occurs in flexible batteries due to mechanical and electrochemical coupling during service. Debonding of electrode will seriously affect the capacity and life of the battery, and even cause a short circuit inside the battery, resulting in spontaneous combustion. Here, the adhesion performance between the electrode sheet and the active material are investigated under the electrolyte environment and different states of charge (SOCs). A small stretcher loading device is used to perform stripping experiments on positive electrodes and negative electrodes in a glove box filled with argon to obtain the peel strength. The binders used in the positive and negative electrodes in this paper are polyvinylidene fluoride (PVDF) and Styrene-Butadiene Rubber/Carboxymethyl Cellulose (SBR/CMC). Compared with the electrode sheet without electrolyte, the peel strength of the positive electrode and negative electrode is decreased by 89.7% and 46.3%, respectively. The significant reduction in peel strength is due to the swelling effect of the electrolyte on the binder. The scanning electron microscope observation shows that there is a large number of active material particles at the interface of the positive electrode and the negative electrode after peeling. Additionally, the peel strength of the positive electrode was increases slightly with the increase of SOC and the added value is 14.8%. But the peel strength of negative electrode decreased with the increase of SOC and the added value is 47.6%. These results play an essential role in evaluating the interface peel strength of the electrode sheet in the different environment and designing electrochemical performance for batteries.