Protective coating for stainless steel BPPs – high ... · 1 Protective coating for stainless steel BPPs – high performance at low cost Bipolar Plates for PEM technology – coatings,

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Protective coating for stainless steel BPPs – high performance at low cost

Bipolar Plates for PEM technology – coatings, manufacturing, test methods and parameters Fronius Manufacturing and Logistic Facilities, Sattledt, Austria, May 20th 2015

Henrik Ljungcrantz,

Impact Coatings AB, Linköping, Sweden [email protected]

BYT BILDEN!!!

Why Impact Coatings? • Supplier of state-of-the-art PVD production technology

• Cost-efficient and environmentally sustainable solutions for coatings in the production flow

• Cut production cost and lead time

• Offers new coatings for energy, connector and decorative applications

About Impact Coatings AB Headquarter: Linköping, Sweden

Public company (Nasdaq-OMX Stockholm, First North)

Supplier of industrial solutions for surface treatment, based on physical vapor deposition (PVD) technology

Offering: Equipment, Process knowhow, Materials

Bipolar plates (BPP)

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BPP functions

Cell separation Gas distribution Current collection Structural integrity

Bipolar Plates Environment (PEM)

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BPP (Anode)

BPP (Cathode)

H2

H2O

O2 H+

H+

Acidic (H20 + H+), pH 2-3 Cell potential ~0.7 V Elevated temperature, 80°C

Corrosive environment

Bipolar plates Desired properties

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Graphite BPP suitable for prototyping Stainless steel BPP requires coating

Property Graphite BPP Metal BPP Chemical stability Good Poor Electrical conductivity Good Good Durability Poor Good Low volume/weight Poor Good Mass producible Difficult Easy

Steel BPP Coating Challenge US Department of Energy (DOE) BPP requirements

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Functional • Chemical stability: <1 µA/cm2

• Electrical conductivity: 20 mΩcm2

Economical • Production cost (competed plates): $3/kW

The solution must be both functional and economically viable

Coating Design Strategy

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MAX phases:

M = Early transition element A = Group A element X = C or N

Ceramic MaxPhase™ from Impact Coatings

• Ceramic alloy producible by PVD

• Corrosion resistant

• Electrically conductive

• Economic and environmentally sound

Microstructure of Ceramic MaxPhase

• Nano-composite film structure – Nano-crystalline grains

– In Amorphous Matrix

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TEM images of MaxPhase

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MaxPhase™

Substrate

Introducing MaxPhase™ coatings for stainless steel bipolar plates

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10

12

14

16

18

20

100 150 200 250 300 250 200 150 100

Con

tact

Res

ista

nce

(moh

ms-

cm2)

Pressure (psi)

Initial Contact Resistance: Average Contact Resistance With 95% Confidence Interval

Averages Averages Averages Averages

0,00

5,00

10,00

15,00

20,00

25,00

30,00

35,00

40,00

25 50 75 100 150 200 250 300 250 200 150 100 75 50 25

Con

tact

Res

ista

nce

(moh

ms-

cm2)

Pressure (psi)

Initial CR for Samples 3, 18, 25 and 36

3-1 F91 18-1 F91 25-1 F91 36-1 F91

Single Point Au Probe Contact Resistance

• In-house capabilities for rapid feedback in coating development

• Contact resistance close to Au

• No detectable surface oxidation

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0

50

100

150

200

250

300

350

400

450

500

0,0 0,2 0,4 0,6 0,8 1,0 1,2

Cont

act R

esis

tanc

e [m

Ω]

Contact Force [N]

Contact resistance

MaxPhase on BPP

Au reference

Graphite

Ceramic MaxPhase™ stack performance

MEAs replaced after 1100hrs

• No degradation attributed to coating detected

Short stack

Current density: 0.5 Acm-2

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0

0,2

0,4

0,6

0,8

1

0 200 400 600 800 1000 1200

Aver

age

cell

volta

ge [V

]

Time [hours]

New MEA

In Situ Stack test – comparison to Au coating

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• Performance after 1500 hours 93 %

• The MaxPhase coated BPP provide similar performance as the gold coated BPP

• After the test the MEA was change and the performance was back at 100%

Post-analysis of metals in membrane

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• The Fuel Cell membrane catalytic ability is degraded by steel corrosion products such as Fe and Cr

• No detectable difference in Fe or Cr content in the membrane between a fresh one and one used for 1 500 hours

ICP-AES, 6 samples, 95 cm2

In Situ Stack Test: 2000 hours

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• Test performed by PowerCell Sweden AB

• S1-series short stack with MaxPhase coated BPP

• Stable performance for 2000 hours

• Reformate fuel with 25 ppm CO • Galvanostatic 500 mA/cm2 operation • 70 °C operating temperature • 80% RH

More info on PowerCell Sweden AB www.powercell.se

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Coating of pre-formed BPP Both sides simultaneously

Production solutions

Vacuum Chamber

1: Load lock Chamber • evacuation in 10 – 20 sec

2: Etch Chamber • Nobel gas or metal ion

3: Coating Chamber • Sputtering; e.g. DC, HiPIMS • Arc evaporation

4:Coating Chamber • Sputtering; e.g. DC, HiPIMS • Arc evaporation

Etch Chamber

Coa

ting

Cha

mbe

r 1

Coating Chamber 2

Load lock C

hamber

Continuous outfeed from conveyor

and robot

Continuous feed from conveyor

and robot

Etch Chamber

Coa

ting

Cha

mbe

r 1

Coating Chamber 2

Vacuum Chamber

Load lock C

hamber

Cost calculation

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The calculation includes:

• Investment

• Personnel

• Running cost

• Service

• Consumer materials

Let’s see if we can meet the United States Department of Energy (DOE) cost target!

MaxPhase on BPP - cost

• Cost per BPP (0.1 m2) < 0.5€ • Capacety in one deposition system 1 000 000 – 2 000 000

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Ceramic MaxPhaseTM today

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Typical applications: Stationary Transportation Portable

Qualified for: • Proton exchange membrane fuel cell (PEMFC) • Direct methanol fuel cell (DMFC)

Image sources: microchp.nl h2euro.org fuelcells.org

Conclusions

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• MaxPhase™ coatings perform as good as gold coatings

• MaxPhase™ is qualified for bipolar plates (BPP) – over 5,000 hours in stack test

• MaxPhase cost on BPP, <0.5 €/kW

• Meets US Department of Energy target for 2020 !

• Impact has both deposition processes and deposition systems for lean production integration

• Impact offers coating service and turn key PVD production systems