ECCS Exam 13 7 22

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EECS – Prof. A. Casalegno – 13th July 2022 1 Standard EECS exam [duration 1 h 40 min] Students who passed TiP reduced number of questions marked with (TiP) [duration 1 h 10 min] To upload (maximum 5 single-side A4 pages – PDF file name MUST BEGIN with person code) Basic Part (4.5 points per question, minimum score 12) (TiP: 7.5 points) 1. Write the Butler-Volmer kinetics equation for hydrogen oxidation reaction (HOR) 2. Write Faraday’s law for electrolyte and reactants of an alkaline electrolyzer 3. (TiP) Write an example of electrochemical reactions occurring in a Lithium-ion battery and the typical battery voltage range Exercise (TiP) A Li-ion battery with nominal capacity of 50 Ah operates at ambient pressure and temperature, requiring 3.8 V for discharging at SoC=80% and C-rate=2 h-1. 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 charge are close to the value of (1-SoC) 4. electrolyte resistance is equal to 1.8 mΩ 5. transfer coefficients of both electrodes during discharge are equal to 0.5 During charge at C-rate=1 h-1, the voltage reaches the value of 3.8 V, estimate the achieved SoC. Intermediate Part (3 points for each question) (TiP: 5 points) 1. Show how current density equation, derived from Nernst-Plank equation, simplifies in the case of a solid electrolyte with fixed charge 2. (TiP) Depict in the chart DV=f(SoC) a typical discharge curve of a Lithium-ion battery and the curves of DV loss attributed to positive electrode, negative one and electrolyte EECS – Prof. A. Casalegno – 13th July 2022 2 Exercise (TiP) A PEM fuel cell operates at 80°C with pure H2 and air at 0.25 MPa pressure and supplies at 0.65 V a current density equal to 1.7 A/cm2 and…