Nano-Composites for Next-Generation Electrochemical Devices

Transcription

1 Nano-Composites for Next-Generation Electrochemical Devices Dr. Jason D. Nicholas Chemical Engineering & Materials Science Dept. Michigan State University, East Lansing, MI MSU EGR Noontime Lecture Series- April 6, 2010

2 A Call to Arms 50% Increase in World Energy Demand in 30 years! Today, 87% of the world s electrical energy comes from the breakup of chemical bonds. Energy Information Association, U.S. Department of Energy, (2009). 2

3 Solid Oxide Fuel Cell (SOFC) Overview Oxygen Conducting SOFCs 3

4 Solid Oxide Fuel Cell (SOFC) Overview SOFC Advantages - Precious metal H 2 dissociation catalysts are not required - Fuel Flexibility (H 2, Gasoline, Natural Gas, JP-8, Butane, etc) - Efficiencies of ~80% with Cogeneration, 60% without - Provides a Transition to the H 2 Economy - Can be made using cheap, colloidal deposition techniques SOFC Technological Challenges - Traditionally operated above 800 o C - Performance limited by electrodes, typically cathodes SOFC Cathode Reaction: 1/2O 2 (g) + 2e - + V o ** = O o 4

5 Justification for Nano- Composite SOFC Electrodes Use high performance materials Data for 800 o C in Air Make composite electrodes 10mm Colloidal Film 100nm Thin Film The imposed limits would allow for dense cathodes with a cathode R P 0.1Wcm 2, e - migration distances 1cm, and R S 0.01* R P. 5 LSC=La 0.6 Sr 0.4 CoO 3-x LSCF=La 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3-x LSFC= La 0.6 Sr 0.4 Fe 0.8 Co 0.2 O 3-x LSF=La 0.6 Sr 0.4 FeO 3-x BSCF=Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-x YSZ= Y 0.08 Zr 0.92 O 1.9 CGO=Ce 0.9 Gd 0.1 O 1.95 LSGM= La 0.9 Sr 0.1 Ga 0.8 Sr 0.2 O 3-x

6 Talk Outline Nano-Composites -Nano-Composite SOFC Cathodes -S.I.M.P.L.E. Model to Predict SOFC Cathode Performance Nicholas Group Research Overview

7 Symmetric Cell Fabrication Step 1 Produce 98%+ Dense CGO Pellets by Firing at 1450 o C for 6 hrs 7

8 Symmetric Cell Fabrication Step 2 Screen Print 20mm Thick CGO Scaffold Layers, Fire at 1100 o C for 1 hr 8

9 Symmetric Cell Fabrication Step 3 Screen Print 17.5mm Thick LSCF Current Collector Layers, Fire at 1000 o C for 1 hr 9

10 Symmetric Cell Fabrication Step 4 Infiltrate Nitrate Solutions through LSCF Current Collector into CGO Scaffold, Fire at 800 o C for 2 hrs. 10

11 Symmetric Cell Fabrication Step 5 Apply Gold Current Collection Grid and Measure Electrical Properties 11

12 Symmetric Cell Electrical Measurements Polarization Resistances for LSCF-CGO Cathodes Infiltrated Multiple Times with 1mL of 1.4M La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-d Nitrate Solution Target Shah, M., Nicholas, J. D., and Barnett, S. A., Electrochemistry Communications 11, 2 (2008). R p (W-cm 2 ) ο C 700 ο C Volume % LSCF Solid Lines = Rp of a Pure Porous LSCF Cathode from Beckel, D. et al., Solid State Ionics 178,

13 Talk Outline Next-Generation Electrochemical Devices Nano-Composites -Nano-Composite SOFC Cathodes -S.I.M.P.L.E. Model to Predict SOFC Cathode Performance Interface Engineereing Nicholas Group Overview

14 Symmetric Cell Fabrication 14

15 Symmetric Cell Fabrication LSCF Infiltrated CGO Cathode CGO Electrolyte 50µm 15

16 Symmetric Cell Fabrication LSCF Infiltrated CGO Cathode CGO Electrolyte 50µm 16

17 Symmetric Cell Characterization Images of La0.6Sr0.4Co0.2Fe0.8O3-d Infiltrated into CGO Courtesy of Megna Shah 17

18 Symmetric Cell Characterization 500nm Images of La0.6Sr0.4Co0.2Fe0.8O3-d Infiltrated into CGO Courtesy of Megna Shah 18

19 S.I.M.P.L.E. Model to Predict SOFC Cathode Performance ~~ 19

20 S.I.M.P.L.E. Model to Predict SOFC Cathode Performance Shah, M., Nicholas, J. D. & Barnett, S. A. Electrochem. Commun. 11, 2-5 (2008). R p 1 2h 1 Exp r R A r I Sc A Inf h 1 Exp h 2h 1 Exp h 1 pexp 1 Exp pr Shah, M., Nicholas, J. D., Barnett, S. A., Electrochem. Commun. 11, 2 (2008). V r 1 O, Sc p RI A A Inf Sc V V O, Sc O, Sc RI A AInf RI A A Inf Sc Sc Based in large part on the model of C.W. Tanner, K.-Z. Fung and A.V. Virkar, J. Electrochem. Soc (1997) (1), p

21 S.I.M.P.L.E. Model to Predict SOFC Cathode Performance S.I.M.P.L.E model predictions matchs both the 600 o C & 700 o C data without the use of fitting parameters! (Estimates are within 40% of Experimental Values) Ionic Resistance in CGO also limiting at high temp. E a (Rs,LSCF) ~ 1.6eV 1 E a (CGO-V O -) ~ ev 2,3 Shah, M., Nicholas, J. D. & Barnett, S. A. Electrochem. Commun. 11, F.S. Baumann et al. Journal of the Electrochemical Society 154(9)(2007) B M. Mogensen et al. Solid State Ionics 129(1-4)(2000) B.C.H. Steele et al. Solid State Ionics 129(1-4)(2000) Shah, M., Nicholas, J. D., and Barnett, S. A., Electrochemistry Communications 11, 2 (2008).

22 S.I.M.P.L.E. Model to Predict SOFC Cathode Performance SSC=Sm 0.5 Sr 0.5 CoO 3-x SDC= Sm 0.2 Ce 0.8 O 1.9 LSC= La 0.6 Sr 0.4 CoO 3-x YSZ=Y 0.08 Zr 0.92 O 1.96 (SSC-SDC) F. Zhao, Z. Wang, M. Liu, L. Zhang, C. Xia and F. Chen, J. Power Sources, 185, 13 (2008). (LSC-SDC) F. Zhao, R. Peng and C. Xia, Mat. Res. Bull., 43, 370 (2008). (LSC-YSZ) Y. Y. Huang, K. Ahn, J. M. Vohs and R. J. Gorte, J. Electrochem. Soc., 151, A1592 (2004). 22 Points=Exp. Meas. Solid Line= S.I.M.P.L.E. Model

23 Talk Outline Nano-Composites -Nano-Composite SOFC Cathodes -S.I.M.P.L.E. Model to Predict SOFC Cathode Performance Nicholas Group Research Overview

24 Nicholas Group Core Compencies Nicholas Group Core Competencies - Structure Property Relationships - Extreme Inorganic Materials Processing (Particles & Films) - Cost-Effective NanoArchitecture Processing and Optimization - Modification of Fundamental Materials Properties with Structure - Fundamental and Applied Electrochemical Property Measurements - New Materials Development 24