The recent growth of electric vehicles, combined with the complexity of underlying phenomena and the lack of maturity of these technologies, reveals the limitations of traditional functional safety engineering approaches, particularly for lithium-ion batteries. Indeed, these systems exhibit complex multiphysical behavior where cell swelling induces coupling between geometric variations and charge-discharge cycles, directly impacting product performance and safety. This work develops a systematic methodological framework for early identification and management of safety risks in the battery design cycle. The approach is based on three steps: (1) safety-oriented functional analysis, (2) structural and functional graph modeling and identification of functional flows (electrical, thermal, mechanical) and their interactions, (3) risk analysis combining ISO 26262 and product graph decomposition to identify failures at two scales (components and functional flow degradation). The methodology is applied to an 8-cell prismatic NMC811/Graphite module during charging, analyzing cell swelling. A particular technical function is selected. The product graph and functional flows analysis allow for identification of relevant physical fluxes and associated parameters for safety. Safety functions are then derived, providing traceability between geometric variations and safety requirements related to the specific lifecycle phases. The developed approach enables designers to systematically anticipate multiphysical failures during the architectural design phase through the identification of functional blocks and their functional flows, reducing late design modifications and improving overall product safety.
Nerestan et al. (Thu,) studied this question.