confidentialwww.solidcell.com 1

SolidCell

Composite Interconnect for SOFC

Sergey Somov1, Olivia Graeve2, Sam Ghosh3, and Heinz Nabielek1

1 Solid Cell Inc., 771 Elmgrove Rd., Rochester NY 14624

2 Alfred University, 2 Pine St., Alfred NY 14802

3 RocCera LLC, 771 Elmgrove Rd., Rochester NY 14624

Daytona Beach, January 25, 2012

confidentialwww.solidcell.com 2

SolidCell

The Interconnect as a Key Component

Metallic-based

Advantages•High mechanical strength & plasticity •High electric conductivity•High thermal conductivity

Disadvantages•Formation of oxide scale in air•Poisoning of cathodes by chromium from stainless steel

Oxide-based

Advantages•Stability in air & fuel •Mechanical stability at high temperatures

Disadvantages•Fragile ceramic materials•Changes in dimensions from variation of oxygen activity

Traditional materials

confidentialwww.solidcell.com 3

SolidCell

Composite Interconnect

A combination of oxide and metallic materials produces a composite with high temperature stability, mechanical robustness, high electrical conductivity, and an adjustable coefficient of thermal expansion (CTE). Also, it withstands corrosion.

The general interconnect composition is:

xNi + (1 – x – y)TiOxNi + (1 – x – y)TiO22 + yNb + yNb22OO55

confidentialwww.solidcell.com 4

SolidCell

Composite Interconnect

The general interconnect composition is:

xNi + (1 – x – y)TiOxNi + (1 – x – y)TiO22 + yNb + yNb22OO55

•Oxide components provide strength and corrosion resistance

•Metallic component increases electrical conductivity and plasticity

confidentialwww.solidcell.com 5

SolidCell

Oxide Component of the Composite

Titania doped by niobium oxide has high electrical conductivity in fuel and moderate conductivity in air.

0,85 0,90 0,95 1,00 1,05

1E-3

0,01

0,1

1

10

100

I52 (5% Nb2O

5) - Air

I52 (5% Nb2O

5) - H

2

I56 (7% Nb2O

5) - H

2

I56 (7% Nb2O

5) - Air

I44 (7% Nb2O

5) - H

2, S

m*c

m-1

1000/T

confidentialwww.solidcell.com 6

SolidCell

Thermal Expansion

y = 0,00000968x - 0,00015892

y = 0,00000918x - 0,00011143

y = 0,00001017x - 0,00018005

y = 0,00000986x - 0,00009899

0

0,001

0,002

0,003

0,004

0,005

0,006

0,007

0,008

0,009

0 200 400 600 800 1000

Т, 0С

(L-L

0)/

L0

33,5%

35,3%

37,2%

YSZ

9,0

9,2

9,4

9,6

9,8

10,0

10,2

10,4

33 34 35 36 37 38

%NiC

TE*1

06 , K

-1

Influence of Ni content on thermal expansion

Dependence of CTE on Ni content at 850oC

confidentialwww.solidcell.com 7

SolidCell

Supporting High Conductivity on the Cathode Side

air

H2

Interconnect disc

YSZ tube

0

0,01

0,02

0,03

0 100 200 300 400

time, hrs

Rs,

Oh

m*c

m2

hydrogen replacement by air

Slight IC porosity provides penetration of hydrogen and keeps the composite in reduced state

confidentialwww.solidcell.com 8

SolidCellChanges of TiO2 (Nb2O5) Resistance

After Replacement of the Gas Environment

11:16 11:31 11:45 12:00 12:14 12:28 12:43 12:57 13:12

0

25

50

75

100

125

150

175

I56 H2 to Air

I44 Air to H2

I44 H2 to CO

2

R,

Ohm

t

a)

The slow change of the resistance is explained by an extremely low rate of oxygen diffusion into doped titania.

18:00 27:00 36:00 45:00 54:00 63:00

0,5

1,0

1,5

2,0

2,5

3,0 I56 H

2 to Air

I44 Air to H2

I44 H2 to CO

2

I44 CO2 to Air

R,O

hm

t

Change of gas environment from air to hydrogen and back: a) –short time; b) –long time

b)

confidentialwww.solidcell.com 9

SolidCell

Composite Interconnect in the MPC Stack

confidentialwww.solidcell.com 10

SolidCell

Composite Interconnect in the MPC Design

confidentialwww.solidcell.com 11

SolidCell

Conclusion

The novel composite interconnect consisting of nickel and titania doped by niobium oxide has high mechanical strength, and high electrical conductivity in air and fuel.

It withstands thermal cycling and oxidation by air.

The coefficient of thermal expansion may be adjusted by variation of the metallic and oxide component ratio.

Acknowledgements: This work was co-funded by NYSERDA (Project No 23644).