Cost-effective novel architectures of interconnects - FCH-02-6-2018

Deadline: Apr 24, 2018  
CALL EXPIRED

Interconnects are crucial components in the upscaling of successful cell concepts to stack performance and reliability. Compared to PEM technology, this pathway is more critical for SOFCs and SOECs (SOCs, including reversible SOC), where cell-interconnect contacting is an enduring challenge. Interconnects are located between individual cells, thus being exposed to both reducing and oxidizing atmospheres at the SOC’s elevated temperatures. This leads to highly stressful conditions for the interconnects, causing significantly higher ASR values per cell in stack configuration than for a single repeating unit for SOC.
Furthermore, due to poor stability over long operating periods of the contact area of coated interconnects, Ohmic resistance increases with time – mainly on the oxygen side – affecting the electric performance of the stack. Thus, SOC interconnects are called for with robust, conductive coating, able to withstand extensive thermal cycling, with fully compatible thermal expansion coefficient, and with improved architecture and/or surface material to guarantee better as well as more durable contacting between cells and interconnect. While ceramic interconnects deliver desirable electronic and mechanical properties, the low ductility of the material challenges their contacting capabilities. Adding to the low design flexibility of ceramics, the low porosity leads to high-pressure drops, lowering the overall efficiency.

Besides maintaining excellent, long-term electrical contact through high specific-surface current collection area, it is crucial to maintain low-pressure drop in the channel distribution of the interconnect, while providing fine flow field patterns for optimal contact resistance and high-power output. Fabrication costs should be kept low and the manufacturing investment cost-effective. Uniform and impermeable gas-tight coating should be achieved to protect against chromium evaporation with high electrical conductivity material. It is recommended that outcomes of FCH 2 JU projects Scored 2.0 and Evolve are taken into account.
The interconnect solution developed in this project should include the bi-polar plate itself together with the protective coating and the contacting materials to make the junction between cells. The development should make use of novel 3D contact Materials and manufacturing solutions that are flexible in use and could be adapted to any manufacturer’s planar stack design, as well as being adaptable to mass-manufacturing processes. Designs that reduce to a minimum the required manufacturing steps is desirable in this respect: this should be proven with a representative stack production batch. The solution proposed should be operational in a temperature range of 600-750°C or 750-900°C, as these two temperature ranges will most likely lead to different material requirements. For electrolysis operation, the fuel side will pose harsher demands on the interconnect than in fuel cell mode (e.g. chromium evaporation), which should be accounted for.
The solution should provide excellent capacity for absorbing applied pressure between current collectors and interconnect, as well as compensating planarity tolerances of adjacent components, allowing 30-50-micron tolerances. It should thus ensure uniform mechanical pressure on the whole cell and maintain lightness of stack. Chemical and thermomechanical compatibility with neighbouring component materials, including sealing when relevant, and electrode materials, should be guaranteed for the targeted operating conditions. The developed interconnect should maximize gas permeability to guarantee low-pressure drops. Improved, uniform conducting throughout the operation ranges prevents hotspot formation and lifetime benefits are to be expected.
Regarding interconnect materials, critical rare-earth elements should be avoided as much as possible, in view of a strategic supply chain for Europe, and long-term stability should be guaranteed, avoiding material inter-diffusion between contacting components.
The final interconnect design(s) should be demonstrated for more than 3000 hours and 50 cycles in a 1 kW stack.
TRL at start: 3 and TRL at end: 5.
MRL at start: 4-5 and MRL at end: 7-8.
The full value chain of the proposed novel interconnect (from raw materials supply to fabrication and assembly methods, compatibility with SOC technology type and material recovery) should lead to a strategic position of established European manufacturers in the international SOC supply chain and leverage job creation opportunities in the EU. It is expected that the proposal involves a component manufacturer based in EU or H2020 Associated Countries, who should be willing to expand or significantly enlarge its current product portfolio with low-cost interconnects. Similarly, it is expected to involve at least one stack manufacturer to adopt the novel interconnect architecture and show marginal dependence of interconnection fabrication costs on SOC stack design.
Any safety-related event that may occur during execution of the project shall be reported to the European Commission's Joint Research Centre (JRC) dedicated mailbox JRC-PTT-H2SAFETY@ec.europa.eu, which manages the European hydrogen safety reference database, HIAD.
Test activities should collaborate and use the protocols developed by the JRC Harmonisation Roadmap (see section 3.2.B "Collaboration with JRC – Rolling Plan 2018"), in order to benchmark performance of components and allow for comparison across different projects.

The FCH 2 JU considers that proposals requesting a contribution of EUR 2 million would allow this specific challenge to be addressed appropriately. Nonetheless, this does not preclude submission and selection of proposals requesting other amounts.
Expected duration: 3 years.

Improved contacting, flow distribution and interface stability will lead to radically better performing interconnects, and thus SOC stack performance and durability. This should lead to a demonstrated increase in stack lifetime in representative operating conditions, allowing service that is more reliable to the end user.
Furthermore, it is expected that – by virtue of the materials chosen and their assembly – the interconnect materials system and shaping process proposed shall be global and the solution should be adaptable at low cost into any SOC manufacturer’s specific stack design, benefiting the lifetime and stackability of individual cells.
Finally, the impacts on the overall supply chain should boost European competitiveness by generating a strategic position in terms of the capability of shaping specialty materials for advanced applications, leveraging capital and excellence in European manufacturing industry, and should build on research organisations’ existing competences and ultimately stimulate competition on the International market.
Technical targets, considering both fuel cell and electrolysis operation modes:

• ASR of the interconnect as a component: <25 mOhm.cm²
• Gas pressure drop: below 30 mbar/plate across the interconnect in stack configuration
• ASR-Degradation: <5 mOhm cm² or <0.2 % (whichever the higher value) per 1000 hours or 10 cycles in a system relevant environment
• Extrapolated Costs: <5€ per unit for interconnect materials + <5€ per unit for coating and processing at a production volume of 50 MW per year.

Type of action: Research and Innovation Action
The conditions related to this topic are provided in the chapter 3.3 and in the General Annexes to the Horizon 2020 Work Programme 2018– 2020 which apply mutatis mutandis.