Ceramic MaxPhase a highly conductive, low cost, and corrosion resistant coating on metal bipolar plates for PEM fuel cells

Transcription

1 Ceramic MaxPhase a highly conductive, low cost, and corrosion resistant coating on metal bipolar plates for PEM fuel cells Henrik Ljungcrantz, Axel Flink, Christian Ulrich, Kristian Nygren Impact Coatings AB, Linköping, Sweden henrik.ljungcrantz@impactcoatings.se Fuel Cell Seminar & Energy Exposition 2015 Los Angeles, CA, USA

2 Why Impact Coatings AB? Volume production solutions for coating of fuel cell metal bipolar plates Ceramic MaxPhase Low cost and high-performance coating Exceeds US DOE requirements Turn-key PVD equipment for volume production Coating Services for prototyping

3 Bipolar plate (BPP) functions in PEM fuel cell H + O 2 H 2 BPP (Anode) H + H 2 O BPP (Cathode) Cell separation Gas distribution Current collection Structural integrity

4 Bipolar plate environment H 2 H + O 2 Acidic (H H + ), ph 2-3 Cell voltage ~0.7 V Corrosive environment H + H 2 O Elevated temperature, 80 C BPP (Anode) BPP (Cathode)

5 Graphite- or metal plates? Car industry chooses metal (stainless steel, titanium) for volume production. 1/3 of weight 1/3 of volume Lower cost Scalable production technology Metal plates require a high-performance coating for corrosion protection and low contact resistance.

6 The metal BPP coating challenge US Department of Energy (DOE) requirements Functional Chemical stability: <1 µa/cm2 Contact resistance: 20 mωcm2 Economical Production cost for coatings: $1/kW The solution must be both functional and economically viable

7 Contact resistance (GDL to BPP) correlates to fuel cell efficiently Can be up to 20% of total resistance in the fuel cell Very critical for automotive FC Contact resistance must be low and stable over time

8 Solution: Ceramic MaxPhase BPP coating MAX < 0.5 µm Low contact resistance (CR) High corrosion stability Low cost below US DOE target

9 Contact Resistance [mω] Single point Au probe contact resistance In-house test for rapid feedback in coating development Contact resistance close to Au reference coating No detectable surface oxidation Contact resistance MaxPhase on BPP Au reference Graphite 0 0,0 0,2 0,4 0,6 0,8 1,0 1,2 Contact Force [N]

10 Contact Resistance (mohms-cm2) MEA to BPP contact resistance (CR) Typical force in FC stack US DOE target Pressure (psi)

11 Ex situ corrosion resistance 24 hour corrosion test Ceramic MaxPhase on stainless steel (SS304) US DOE Target 1000 na/cm 2

12 In situ stack test: 5000 hrs Test performed by PowerCell Sweden AB S1-series short stack with Ceramic MaxPhase coated BPP Stable performance for 5000 hours PowerCell Fuel Cell S1 Reformate fuel with 25 ppm CO Galvanostatic 500 ma/cm 2 operation 70 C operating temperature 80% RH For more information visit:

13 In situ stack test comparison to Au coating The MaxPhase coated BPP provide similar performance as the gold coated BPP Performance after 1500 hours 93 % After the test the MEA was change and the performance was back at 100%

14 Post-analysis of metals in membrane The Fuel Cell membrane s 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 1500 hours

15 Coating in BPP production flow Cutting Stamping Welding Coating Packaging Low cost Highest performance Coating Cutting Stamping Welding Packaging Lowest cost Medium performance

16 Summary Automotive industry chooses metal bipolar plates over graphite for PEM fuel cell volume production (1/3 weight, 1/3 volume, lower cost, scalability) Coating requirements: Low contact resistance High corrosion stability Low cost Contact resistance (MEA to BPP) correlates to the fuel cell efficiency, i.e. low contact resistance critical for automotive FC! Ceramic MaxPhase coating exceeds US DOE requirements for PEM fuel cells both on functionality and cost In situ tested in fuel cell stack for 5000 hrs

17 THANK YOU!