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Abstract: A single polymer electrolyte fuel cell has been directly hybridized to a stack of three supercapacitors: the system formed has been investigated in operation in the fuel cell dynamic load cycle, which emulates the energy demand in transported applications. Comparison with regular, non‐hybridized fuel cell operation was analyzed in terms of hydrogen consumption in the case that the gas flow rates are directly controlled by cell current during the cycles with constant gas stoichiometric factors: the smoothening effect of the supercapacitors in the overall circuit leads to more even profiles of the cell current and voltage in the cycle, which allows safer and better hydrogen consumption management in this regime: the average H2 consumption per cycle could be reduced by 16% without change of the overall energy produced. Besides, the runs were conducted over more than 1,300 hours with evaluation of the fuel cell performance and capacity at regular intervals, with or without hybridization. A moderate positive effect of hybridization was observed in the time variations of the voltage‐current curves and the fuel crossover. However, the resistances for ohmic, charge transfer and diffusion phenomena, were not so much improved by the hybridization, in spite of less sharp voltage. [ABSTRACT FROM AUTHOR]

Abstract: This article deals with an electrical model of lithium-ion battery, based on a 1D analog representation of mass and charge transport phenomena. By using an electrical analogy to describe migration and diffusion of species and charges in electrodes and electrolyte, the model can be directly implemented in standard simulation software used in electrical engineering (such as Saber, in our case), so that it can be easily employed for the simulation of electrical systems involving lithium-ion batteries. The paper explains how the analog model is obtained from mass and charge transport equations, then it presents a comparison with results obtained by means of a finite element method. At last, some electrical power systems are simulated in order to show advantages of our modeling method. [Copyright &y& Elsevier]

Abstract: This paper deals with occurrence of lithium plating on the negative electrode of lithium-ion batteries, a significant ageing phenomenon known to damage lithium-ion battery performances. Charge transfer process, one of the two different steps of the process of Li insertion in the negative active material being the cause of this ageing, was considered here to be the limiting process. This transfer occurs at short-time scales. The second process, the diffusion of lithium in the solid insertion compound, occurring at relatively long-time scales, has not been fully examined here. The aim of this paper was to develop a new method to evaluate the maximal rate of a charge pulse solicitation to prevent this ageing phenomenon. The approach relies on the use of a fundamental model of lithium ion battery with coupled mass and charge transfer. To validate the method, 2 s microcycles have been performed on a commercial VL41M SAFT cell. Theoretical and experimental works led to the maximum current density to be applied without undesired Li deposition, depending on the state of charge (SOC). The abacus established for the cell of interest can orient further specifications for suitable use of the battery. [Copyright &y& Elsevier]

Abstract: The effect of MEA pinhole size on the aging of single (10 × 10 cm2) PEMFC was investigated. Two MEAs were perforated by two pins of different diameters (0.7 and 1.2 mm), in both cases in the H2 inlet zone. The performance losses and the degradation rates of the MEA components were compared to those exhibited by a healthy, not perforated MEA. Perforation by the smaller pin did not promote immediate cell voltage decay and the hydrogen crossover increased only slightly. Perforation by the larger pin resulted in immediate reduction in cell voltage and one decade increase of the hydrogen crossover. LSV and CV voltammograms performed for determination of the crossover and the electrode active surface were changed abruptly by the larger perforation, which confirmed the existence of an internal short circuit within the MEA. Besides, the perforation affected the time variations of the diffusion and charge transfer resistances. [Copyright &y& Elsevier]

Abstract: This article deals with a PEMFC (proton exchange membrane fuel cell) electrical model based on a 1D analog representation of mass transport phenomena, and taking into account the influence of gas supply conditions on fuel cell voltage. By using an electrical analogy to describe transport of gaseous species in GDLs (gas diffusion layers), and water distribution in the membrane, the model can be directly implemented in standard simulation softwares used in electrical engineering (such as Saber, in our case), so that it can be easily employed for the simulation of fuel cell electrical systems. The paper explains how the analog model is obtained from mass transport equations, then it presents validation tests carried out in both steady-state and transient regimes on a PEM single cell bench. [Copyright &y& Elsevier]