Revealing polarization characteristics and voltage inconsistency of fuel cells in stack via micro-current excitation method

Cell-to-cell inconsistency threatens the performance, reliability and durability of large-scale fuel cell stacks, while the lack of stack-level diagnostic tools remains a critical bottleneck in identifying its intrinsic origins. This study aims at revealing polarization characteristics, corresponding determinants and voltage inconsistency of cells via the micro-current excitation (MCE) method. Applicable throughout the entire lifecycle of fuel cell stack, MCE method enables the recognition of membrane electrode assembly (MEA) material state parameters and gas distribution characteristics. Considering variations in working conditions and pseudo-two-dimensional distribution of internal physical states, the further corrected mapping relationship between MCE-identified parameters and polarization characteristics is clarified, involving roughness factor of catalyst for activation polarization, open-circuit ohmic resistance for ohmic polarization, and gas distribution for concentration polarization and internal water states. The multi-parameter coupled performance prediction model achieves high-precision prediction of inter-cell voltage inconsistency, which gets verified across three stacks and covers a wide range of operating conditions. For unpredictable gas-water states, gas distribution characteristics and their evolution with humidity provide a reliable basis for identification of typical cells. Cells with lower flow rates face a higher risk of gas starvation, whereas cells prone to water accumulation are characterized by a pronounced flow-rate drop under high-humidity conditions. This study provides in-depth insights and a comprehensive analytical framework for elucidating cell inconsistency, identifying critical cells, and supporting consistency guarantee in fuel cell stacks.