Phase change material-based thermal management systems for PEM fuel cell/battery hybrid electric vehicles: A comprehensive review

Proton exchange membrane fuel cell/battery hybrid electric vehicles (FCHEVs) require efficient thermal management because multiple onboard subsystems operate over different temperature ranges while exhibiting strong thermal interactions. Phase change materials (PCMs), owing to their high latent-heat storage density and near-isothermal phase-transition behavior, have emerged as promising materials for thermal management. However, a comprehensive vehicle-level perspective linking PCM materials, subsystem integration, thermal requirements and interactions is still lacking. This review addresses this gap by providing a systematic, vehicle-level perspective on PCM-based thermal management in FCHEVs. The thermal characteristics and conventional thermal management strategies of the motor, PEMFC, hydrogen storage, cabin, and battery thermal loops are first reviewed, followed by a systematic summary of the classification, thermophysical properties, and selection criteria of PCMs and phase change slurries (PCSs). Representative PCM integration strategies for each thermal loop are then critically analyzed, demonstrating that PCM applications have evolved beyond passive thermal buffering to include transient thermal regulation, thermal retention, cold-start assistance, waste-heat utilization, and cross-loop thermal coupling. A decision-oriented PCM selection framework is further developed by linking operating temperature, thermal function, material form, selection criteria, and integration strategy across the major thermal loops. Finally, the current challenges and future research directions are discussed from the perspectives of vehicle integration, subsystem implementation, material development, and engineering application.