Current Activities on Solid Oxide Cells at DLR Asif Ansar, Rmi - PowerPoint PPT Presentation

Current Activities on Solid Oxide Cells at DLR Asif Ansar, Rémi Costa, Michael Hörlein, and Günter Schiller German Aerospace Center Institute of Engineering Thermodynamics Stuttgart, Germany

Outline • Brief Introduction of DLR-ITT • Metal Supported Cell Concepts for SOC - Plasma spray concept - EVOLVE concept • SOEC activities - Hi2H2 project - Degradation study - Solar fuels • Conclusion

DLR German Aerospace Center Aeronautics Space Research Institution Transport Energy Space Agency > 7500 employees across Project Management Agency 32 institutes and facilities

Institute of Engineering Thermodynamics Prof. Dr. André Thess Administration Jörg Piskurek Electrochemical Computational Thermal Process System Analysis and Energy Technology Electrochemistry Technology Techn. Assessment Prof. A. Friedrich Prof. A. Latz Dr. A. Wörner Dr. C. Schillings / C. Hoyer-Klick (komm.) Staff: About 190 in Stuttgart, Köln, Hamburg and Ulm Yearly budget: About 18 Mio. EUR including 50% third party funding „... innovative solutions for sustainable and environmentally friendly energy storage and conversion processes ...“

Electrochemical Energy Technology R&D of efficient electrochemical energy storage and conversion 5 Fields of Research Solid Oxide Cells Realization of durable, powerful and cost effective SOFC-stacks Polymer Electrolyte Fuel Cells Improvement of longevity and reliability with regard to electric mobility and residential power supply Lithium Metal and Lithium Ion Batteries Development of mobile energy storages Modeling & Simulation Improvement of the efficiency factor, longevity and costs of fuel cells and batteries Electrochemical Systems Development of efficient and effective, multifunctional fuel cells systems for stationary and mobile applications

Generations of planar SOFCs 1 st gen. 2 nd gen. 3 rd gen. ASC MSC ESC Cathode Electrolyte Anode Limited power density High power density High power density Fuel flexibility Fuel flexibility Fuel flexibility Robustness Sulfur poisoning Sulfur poisoning Thermal cycling Thermal cycling Redox Cycling Redox Cycling Stationary Stationary Stationary Transportation Transportation Transportation

Metal Supported SOFC oxygen/air not used air Plasma Spray for Functional Layers air channel Bipolar plate Compact design with thin sheet protective coating contact layer ferritic substrates and interconnects cathode current collector cathode active layer electrolyte anode 100 cm² foot print porous metallic substrate fuel channel Counter flow stamped gas manifold Bipolar plate Welded substrate with the interconnect fuel brazing not used fuel + H O 2 (not in scale) Brazing or Glass Seal as joining of repeat units Cathode 20 µm Electrolyte 35 µm Anode 35 µm Substrate

Functional Principle of DC Plasma Substrate Particle Melting and Acceleration Plasma Gun Plasma Gases Ar H 2 Powder Jet N 2 He Coating Particle Injection Particle Impingement Splat Layering

Metal Supported SOFC - Performance MSC Cell MSC Cell with Suspension Plasma Spray Electrodes 12.5 cm² cell at 800°C; H 2 /N 2 and air Power density above 800 mW/cm² at 0.7 V 12.5 cm² cell at 800°C; H 2 /N 2 and air 1000 1,1 Power density / Cell voltage / V 750 1 -2 mW*cm 0,9 A B 500 C D 0,8 250 0,7 0,6 0 0 400 800 1200 1600 Current density / mA*cm -2 1,2 800 MSC-10-31, 800°C, 27h @ 7,0 V 10H2+10N2/ 20 Luft (SLPM) 1,1 610 mW/cm² @ 0.7V (2009- G6) P1: Kennlinie nach Aufheizen, KL1 P stack = 250 W 1,0 FU = 24,8 mol% U 0,9 600 Leistungsdichte p [mW/cm²] 0,8 Zellspannung U [V] Stromdichte@ 700mV OCV 0,7 Zelle 10: 173 mW/cm² Zelle 10: 1,019 V Zelle 9: 315 Zelle 9: 1,006 V Zelle 8: 324 Zelle 8: 1,007 V 0,6 400 Zelle 7: 325 mW/cm² Zelle 7: 1,001 V 10-Cell Stack Zelle 6: 318 Zelle 6: 1,006 V 0,5 Zelle 5: 324 mW/cm² Zelle 5: 1,016 V Zelle 4: 329 Zelle 4: 1,022 V Zelle 3: 320 mW/cm² Zelle 3: 1,005V 0,4 Zelle 2: 319 Zelle 2: 1,013V 100 cm² cells at 800°C; H 2 /N 2 ; air Zelle 1: 320 mW/cm² Zelle 1: 1,014 V 0,3 200 0,2 0,1 p 0,0 0 0 100 200 300 400 500 Stromdichte i [mA/cm²] Vortrag > Autor > Dokumentname > Datum

Cyclability of Metal Supported Cells Thermal cycles Redox cycle 1200 400 1200 U2_start 400 MSC-02-17, 800°C MSC-02-17, 800°C U2_Redox_5 2 H 2 +2 N 2 / 4 Air (SLPM) 2 H 2 +2 N 2 / 4 Air (SLPM) U2_Redox_20 458 / 1227 h 1227 / 1517 h 350 350 p2_start 1000 1000 p2_Redox_5 U 300 300 p2_Redox_20 U power density p [mW/cm²] power density p [mW/cm²] 800 800 cell voltage U [mV] cell voltage U [mV] Redox_start U1_start 250 250 cell2: 157 mW/cm² U2_start U1_end Redox_5 U2_end 600 200 600 cell2: 177 mW/cm² 200 p1_start Redox_20 p2_start cell2: 149 mW/cm² p1_end 150 150 p2_end 400 400 Redox 5 @ 1,4 V p p 100 100 Pstack = 33,3 W FU = 16,6 mol% 200 200 Redox start @ 1,4 V Redox 20 @ 1,4 V 50 50 Pstack = 28,5 W Pstack = 26,0 W FU = 12,9 mol% FU = 14,1 mol% 0 0 0 0 0 50 100 150 200 250 300 0 50 100 150 200 250 300 current density i [mA/cm²] current density i [mA/cm²] 20 forced redox cycles performed with 50 15 thermal cycles performed, 12 down to 350 °C ml/min O 2 on the anode side per layer and 3 to ambient temperature Increase of power density after 5 cycles Degradation after thermal cycles was 10.3 % (Improving contact Ni-YSZ?) Degradation of the stack was 9.1 % after 20 redox cycles

Measurement Setup for Segmented Cells Local temperature measurements • 16 galvanically isolated segments Local fuel concentrations • Local and global i-V characteristics Flexible design: substrate-, anode-, and • Local and global impedance measurements electrolyte-supported cells Co- and counter-flow

Experimental Setup for Raman Spectroscopy Measurements

Beyond the 3 rd Gen. SOFC: Issues to be addressed for improving MSCs • Cr-poisoning at the cathode side > Protective coating required • Improve tolerance toward sulfur poisoning • Lifetime of metal substrate if stationary applications are considered • Hermetic electrolyte Which materials and architecture for the next generation SO(F)C?

Beyond the 3 rd Generation SOFC Metal substrate resistant toward oxidation Formation of an Al 2 O 3 layer as a durable protective coating Al rich alloys, on the basis of MCrAl(Y) with M being Fe, Ni, Co or a mixture

Nickel-free Hybrid Metal-Ceramic Supported SOFC Infiltration with an electronic conductor (ideally a ceramic) Dense La 0.1 Sr 0.9 TiO 3 (800°C): sintering in H 2 : σ tot ≈ 150 S/cm O. Marina et al. Solid State Ionics, 149 (2002) 21-28. S. Hashimoto et al. Journal of Alloys and Compounds, 397 (2005) 245-249. Y. Tsvetkova et al. Materials and Design, 30 (2009) 206-209. Hybrid current collector mechanically and chemically stable in both oxidant and reducing atmosphere

Beyond the 3 rd Generation SOFC Use of perovskite materials at the anode and cathode, being modified by addition of suitable catalysts High power density, sulfur resistant, fuel flexibility, thermal cycling, redox cycling Stationary applications …

Beyond the 3 rd Generation SOFC Source: Alantum Europe GmbH Metal Foam: NiCrAl Composition of the anode: Ce 1-x Gd x O 2- α / La 0,1 Sr 0,9 TiO 3- α Electrolyte: 8-YSZ / 10-GDC Cathode : La 0,4 Sr 0,6 Co 0,2 Fe 0,8 O 3- α

Beyond the 3 rd Generation SOFC Perovskite based anode Thin film electrolyte (1 µm YSZ+ 2 µm CGO) with improved hermiticity (in collaboration with Ceraco GmbH) SoA MSCs DLR 2010 2014 Manufactured in air (except PVD layer) 2015

Beyond the 3 rd Generation SOFC 50 mm x 50 mm with active surface 16 cm² P @ 0.7V and 750°C  340 mW /cm²  Redox cycles tested: 10  But… with addition of Nickel!!! AFL: LST-CGO 50:50 modified with 5 wt% Nickel Current collector: NiCrAl + LST 50vol% - Ni 50vol%  Issue with sulfur poisoning still expected Replacement of Nickel still remains challenging!

Solid Oxide Electrolysis P el Advantages: + ‐ • High temperature (600 - 900°C) Air H 2 O • Fast reaction kinetics • Low overvoltage • High efficiency & high current densities e ‐ e ‐ • No noble metals as catalysts O 2 ‐ • Fuel versatility: CO 2 electrolysis  Co-electrolysis of H 2 O/CO 2 possible  Syn-gas production  External (or internal) hydrocarbon O 2 H 2 formation Electrolyte Anode ‐ Cathode ‐ Oxygen electrode Fuel electrode

Hi2H2: I-V Curves of a VPS Cell in SOFC and SOEC Mode as a Function of Temperature 1,4 750 1,3 500 1,2 250 p(i) power density/mW cm -2 1 - 192h, 800°C 1,1 0 2 - 195h, 750°C cell voltage/V 1 -250 3 - 199h, 850°C 0,9 -500 U(i) 0,8 -750 0,7 -1000 0,6 -1250 gas flow : 40/16//160 ml min -1 cm -2 H 2 /H 2 O//air (30% steam) 0,5 -1500 -1200 -1000 -800 -600 -400 -200 0 200 400 600 800 1000 1200 current density/mA cm -2

Hi2H2: Complete Test Run of a VPS Cell in Electrolysis Mode 1,6 800 temperature 1,4 700 1,2 600 voltage/V, pH2O/atm 1 500 voltage temperature/°C 0,8 400 varied -0.3 A cm - ² electrolysis 0,6 300 electrolysis +26 mV /1000h (2,1%/1000hr) +46 mV /1000h (3,9%/1000hr) 0,4 200 H 2 O-ratio U/V 0,2 100 pH2O/bar T/°C 0 0 0 288 576 864 1152 1440 1728 2016 2304 time/hr Lit: G.Schiller et al., J. Appl. Electrochem., 39, 293-301, 2009