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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 3 - VOLUMETRIQ (Volume Manufacturing of PEM FC Stacks for Transportation and In-line Quality Assurance)

Teaser

VOLUMETRIQ aims to develop a European supply base for automotive PEM fuel cell stacks and their key components with volume manufacturing capability and embedded quality control. Targets are 1.5 W/cm2 at single cell and stack levels.

Summary

Work performed

VOLUMETRIQ has reached its goal of developing a new, high power density automotive fuel cell stack (NM12) comprising components prepared at volume, and has achieved an exceptionally high stack power density of 5.38 W/l (excluding housing). By associating improvements in the ionomer used for the membrane, cathode catalyst construction, compression set, gas diffusion layers and by moving from baseline (NM5) to project improved (NM12) cell hardware, VOLUMETRIQ has achieved a leading single cell power density of 2.67 A/cm2 at 0.6 V (1.6 W/cm2) with catalyst coated membranes produced at volume. This exceeds the project target of 1.5 W/cm2. In parallel, and at automotive single cell level, VOLUMETRIQ has demonstrated 2700 hours of drive cycle testing, allowing reasonable expectation of 5000-6000 hours durability.
In WP2, BMW provided the stack and component specifications and defined test specifications. BMW specified stack requirements as well as automotive operating conditions that meet the system efficiency and dynamic requirements, and defined realistic geometrical dimensions for stack integration and requirements for environmental robustness. EK and JMFC broke down the requirements to component level specifications. The power density target achieved using the new cell hardware at single cell level in RP2 was reached using a short stack and in the full-size stack in RP3. This stack comprises 299 cells and provides a total power of 111 kW, which largely exceeds the original goal of 90 kW. The full stack was tested under various operating conditions, including the EU harmonised test protocol. A cost projection by EK for high volume production of a full stack, on the assumption of 50,000 units/year, led to 68 â‚¬/kW.
The objective of WP3 to demonstrate the manufacturability of a thin, low equivalent weight, nanofibre reinforced membrane using roll-to-roll high volume manufacturing processes was achieved in RP2. CNRS and JMFC collaborated to scale the electrospinning process with external industrial vendors equipped with off the shelf continuous electrospinning lines. CNRS introduced advanced grades of PBI to associate the requisite properties of feasibility of scale-up, mechanical resilience enabling its use in roll to roll processing, and compositional features compatible with its intended use. PBI electrospun roll material was then used successfully on JMFC casting line for membrane fabrication, and the scaled-up membrane was qualified for performance and durability at JMFC. Further evaluation of PBI reinforced Aquivion membranes confirmed the step changing improvement over the best ePTFE reinforced analogue containing the same ionomer and additive technology in in-cell relative humidity cycling durability assessment. Reduced rates of increase in gas crossover after the initial onset indicate subdued membrane deterioration after the onset of cracks at the anode or the cathode. In parallel, JMFC sourced ePTFE reinforcements having improved mechanical isotropy. Improved ionomer with different specifications and composition was prepared at high volume by Solvay for use in the membrane (RP1), while novel high oxygen permeability ionomers were developed in RP2 for the cathode catalyst layers that are currently undergoing final qualification, both in VOLUMETRIQ and also, by inter-project transfer, to INSPIRE.
WP4 has successfully demonstrated the manufacturing capability of an optimised high performance CCM compatible with high volume manufacturing, incorporating a low EW ionomer and both expanded PTFE and electrospun nanofibre reinforcements. For reasons of timing and relative product maturity, the CCMs produced for the NM12 stack comprise membranes reinforced with ePTFE. The CCMs developed exceed the performance milestone of 2.5 A/cm2 at 0.6 V. A CCM manufacturing process tailored to EKâ€™s stack assembly process was developed and qualified. Risks and mitigations associated with the coating and converting of membranes to CCMs were

Final results

VOLUMETRIQ has achieved an exceptionally high power density of 5.38 W/l in a novel stack hardware comprising CCM components prepared at volume. The stack power of 111 kW for 299 cells surpasses the target of >90 kW. The cost estimate, with the assumption of 50,000 units/year, of 68 â‚¬/kW is significantly below the 2014 annual working plan objective of 100 â‚¬/kW.