Prabhu Ganesan, Hector Colon, Bala Haran, R. E. White and Branko Popov Department of Chemical Engineering University of South Carolina, Columbia, SC La 0.8 Sr 0.2 CoO 3 Coated Nickel Cathodes for Molten Carbonate Fuel Cells

Presentation Outline  Objectives  Prepare a stable cathode material with lower solubility and comparable performance as NiO Coating of La 0.8 Sr 0.2 CoO 3 using sol-gel process  Characterization Studies  Polarization performance  AAS – Solubility measurements  SEM – Microstructure analysis  EIS  Full cell studies

State-of-the Art Molten Carbonate Fuel Cells Component Material / PropertiesProblem/Solution AnodeMaterialNi+10wt% Cr Pore size3 ~ 6  m Porosity 50~70% Thickness 0.5~1.5 mm Sp. Area0.1~1 m 2 /g Creep/Sintering - Ni-Al Alloy Electrolyte retaining - Coating of Oxides CathodeMaterialLithiated NiO Pore size6 ~ 9  m Porosity 80~85% as Ni Thickness 0.5~0.8 mm Sp. Area0.5 m 2 /g NiO dissolution - Stabilized NiO - LiCoO 2 cathode - Modified electrolyte Matrix Material  -LiAlO 2 Pore size0.2 ~ 0.5  m Porosity 50~60% Thickness 0.5 mm Sp. Area0.1~10 m 2 /g Sintering/Thermal Stability - Fiber or large particles Phase stability -  -LiAlO 2 Current Collector MaterialSS316 Chromium Dissolution - Nickel Cladding (Anode) - Fe-Al alloys

Cathode Materials for Molten Carbonate Fuel Cells State-of-the-art NiO(Li) Alternate Cathodes LiCoO 2, LiNiO 2 LiCoO 2 Coated Nickel Oxide Ni-Ce and Ni – La 2 O 3 Ni-Nb Surface Alloy Perovskites such as La 0.8 Sr 0.2 CoO 3 Cobalt Encapsulated Nickel Mixed Lithium Nickel Cobalt Oxides

USC Molten Carbonate Fuel Cell (Half Cell) Porous Ni Cathode Perforated SUS 304 Current Collector

USC Molten Carbonate Fuel Cell (Full Cell)

Flow chart for Ni electrode preparation Ni Powder Dispersant + Water Milling 24 h Binder Milling 12 h PlasticizerMilling 12 h Filtering Casting De-airing Drying Sintering

TGA Behavior of Ni green tape

Sintering schedule for Ni electrodes 1 O C/min RT 130 O C 1 O C/min 5 O C/min 230 O C 400 O C 800 O C 130 O C 230 O C 400 O C 800 O C RT 1 h 3 h 5 h 1 h Nitrogen Hydrogen

Flow chart for LSC Coated Ni electrode preparation La, Sr, Co-Acetates Dist. Water Stirring at 80 o C Ethylene Glycol Stirring Gel Drying in Vacuum at 90 o C Sintering at 900 o C in Air Citric Acid Ni Electrodes

XRD Patterns of La 0.8 Sr 0.2 CoO 3 at different temperatures

SEM Pictures of La 0.8 Sr 0.2 CoO 3 coated Ni electrode After Sintering at 900°C Bare Ni Electrode LSC Coated Ni Electrode Sintered at 900 o C LSC Coated Ni Electrode after immersion in molten carbonate Melt for 200 hours Magnification X 2000

Dissolution Behavior La 0.8 Sr 0.2 CoO 3 coated Ni electrode at 650 o C

Polarization Behavior of Ni

Polarization Behavior of La 0.8 Sr 0.2 CoO 3 coated Ni electrode

Comparison of Impedance Behavior of Ni

EIS response for La 0.8 Sr 0.2 CoO 3 coated Ni electrode at 650°C

EIS response for La 0.8 Sr 0.2 CoO 3 coated Ni electrode at 700°C

EIS response for La 0.8 Sr 0.2 CoO 3 coated Ni electrode at 750°C

EIS response of La 0.8 Sr 0.2 CoO 3 coated Ni electrode in Full Cell at 650°C

Conclusions  Rate of dissolution of Ni decreased significantly after La 0.8 Sr 0.2 CoO 3 coating.  The observed increase in polarization may be due to the decrease in porosity and change in surface morphology.  La 0.8 Sr 0.2 CoO 3 coated nickel oxides offer better stability in MCFC cathode environment.

Financial sponsors - Dept of Energy, National Energy Technology Laboratory Acknowledgements