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EECS – Prof. A. Casalegno – 12th February 2020 1 Basic Part (3 points per questions, minimum score 12) 1. Write an example of electrochemical reactions occurring in a Lithium-ion battery and the typical operating voltage range 2. Write the Nernst-Plank equation for current in a generic electrolyte 3. Draw the electrical potential in the double layer of a PEMFC for a HOR in equilibrium 4. Depict the polarization curve of a PEM electrolyzer with reasonable values Name _____________________________ Person N. __________________________ EECS – Prof. A. Casalegno – 12th February 2020 2 Exercise 1 Associate the three PEMFC i/ΔV curves to the following cathode operating conditions and explain why limiting current is changing, referring to its definition. 1. O2 feeding at 100%RH 2. Air feeding at λ=2 and 100%RH 3. Air feeding at λ=3 and 30%RH Exercise 2 A Li-ion battery with nominal capacity of 10 Ah discharges as in the figure. Assuming that: 1. Tafel kinetics is valid for both electrodes 2. ion and mass transport effects in electrodes are negligible 3. activities of reactants in discharge (or charge) are close to the value of SoC (or 1-SoC) 4. electrolyte resistance is equal to 10 mΩ 5. transfer coefficients of both electrodes during discharge are equal to 0.5 Calculate the values of C-rate A and C-rate B. !"#0% ∆% 2.75 V 4%20% 100%50% 3.55 V3.06 V 2.92 V EECS – Prof. A. Casalegno – 12th February 2020 3 Intermediate Part (3 points per questions) 1. Write Butler-Volmer and Tafel equations and represent on the same graph 2. Represent the impedance spectrum of a PEMFC operating at low current and indicate where information on membrane and catalyst layer ion conductivity can be obtained 3. Depict the effect of degradation on the discharge curve and capacity of a battery,…