Assembly‐Deviation‐Induced Sealing Leakage in PEMFC Stacks: Failure Mechanisms, Prediction Models, and Process Regulation

ABSTRACT Sealing reliability is critical to the efficiency, durability, and safety of proton exchange membrane fuel cell (PEMFC) stacks for hydrogen‐energy applications. In multilayer stacks, manufacturing errors, interlayer misalignment, gasket and gas‐diffusion‐layer thickness variations, and non‐uniform clamping loads are transmitted through compliant components and modify local sealing‐interface states. This review examines the chain from assembly‐deviation sources and propagation mechanisms to contact‐pressure redistribution, micro‐gap connectivity, interfacial leakage, bulk permeation, and process regulation. Compared with previous reviews that mainly focus on PEMFC sealing materials, sealing structures, stack assembly techniques, or clamping‐load design, this review highlights the variable‐transfer pathway by which assembly deviations are converted into contact‐state degradation and leakage‐rate inputs. Recent finite‐element contact analyses, rough‐interface leakage models, and multiscale prediction methods are summarized, with emphasis on variables linking assembly quality to leakage risk, including minimum local contact pressure, real contact area, equivalent leakage‐channel height, and leakage‐path connectivity. This review establishes a reliability‐oriented framework linking assembly deviation, contact pressure degradation, micro‐gap formation, leakage‐path evolution, and leakage‐rate prediction in PEMFC stacks. It critically compares analytical, numerical, experimental, and data‐driven approaches for leakage analysis and summarizes regulation strategies for improving stack assembly quality and sealing reliability. Future directions involving intelligent assembly, online monitoring, and digital‐twin‐assisted leakage control are also discussed. Future research should integrate manufacturing‐deviation databases, assembly‐process monitoring, leakage testing, online diagnostics, and service‐degradation data to support predictive sealing‐reliability design and closed‐loop assembly regulation for PEMFC stacks.