Internal fault diagnosis method for lithium batteries based on a failure physical model

Performance degradation of lithium-ion batteries is directly related to failure mechanisms such as loss of internal active lithium ions or active material. For in-service batteries, internal failures or degradation cannot be directly observed, and it is difficult to analyze and diagnose them through limited external characteristic measurements. To effectively diagnose lithium-ion batteries failure behaviors, an internal fault diagnosis method is proposed. Firstly, a failure physical model containing side reactions is established, aiming at studying the inherent relationship between the parameters of the failure physical model and internal faults. Then, a method of constructing parameter failure boundaries is proposed to diagnose whether aging failures including electrolyte decomposition, active particle rupture, SEI film growth, and lithium plating occur inside the battery by tracking and analyzing the evolution laws of the model parameters. Finally, abnormal batteries with faster capacity degradation in the same group are selected, and based on destructive characterization testing, the effectiveness and reliability of the proposed non-destructive internal fault diagnosis method are verified.