Debonding at the interface between active particles and PVDF binder in Li-ion batteries

Abstract

Mechanical failure in the electrode is one of major reasons for capacity fade. In this study we focus on inter-particle fracture, specifically the debonding at the interface between the graphite particle and binder. We integrate the electrochemical-mechanical model and the cohesive zone model to investigate the interfacial debonding during lithium intercalation. We found that the mechanism of fracture at the particle/binder interface is different from that inside a particle. The debonding at the interface is caused by the expansion of the particle that is closely related to the total amount of lithium intercalation, while the fracture inside a particle is caused by the gradient of lithium concentration. As a result, debonding at the interface is more likely to occur as the particle size and C-rate decrease, which is opposite to the trend of fracture inside a particle that is more likely to occur as the particle size and C-rate increase. This understanding of debonding mechanism can provide insight into capacity fade and guide the development of more robust electrodes. (C) 2015 Elsevier Ltd. All rights reserved.