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

• Studied debonding at the interface between particle and binder in a battery.
• Integrated electrochemical–mechanical model and cohesive zone model.
• Debonding is more likely to happen as the particle size and C-rate decrease.
• The trend of debonding is opposite to that of fracture inside a particle.
• Debonding is closely related to the total amount of lithium intercalation.

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.

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