Investigate the changes of aged lithium iron phosphate batteries from a mechanical perspective.

Lithium-ion batteries are currently widely used in various industries. Battery aging is inevitable, and it is also a key scientific issue in battery research. However, it is still lacking a comprehensive view of the aged battery from a mechanical perspective. This article aims to provide insight into the mechanical perspectives of the aged batteries. First, the morphologies of aged batteries were observed and measured from macro-to micro-scale. Second, the relationship between mechanical properties and the SOH of components and single batteries was quantified. Third, industrial CT and computational models were used to analyze the internal deformation of aged batteries. Finally, the swelling forces of aged batteries were investigated. The typical characteristics of swelling force were analyzed for various aged batteries, and mechanisms were revealed through experimental investigation, theoretical analysis, and numerical calculation. The results will help observe and reveal the aging mechanism of lithium batteries from a mechanical perspective.