Applying wash coating techniques for swelling-induced stress reduction and thermal improvement in metal hydrides

The storage of hydrogen in metal alloys as an alternative to hydrogen storage in pressurized or liquid form has the advantage of high volumetric storage capacity and less complex storage systems due to lower pressure and moderate temperature conditions. The later leads to an improved safety and reduced cost of the storage vessel. However, when considering their utilization in hydrogen storage tanks, swelling-induced stress and heat management are challenges that still require to be addressed. Several strategies have been published in the past to address these problems, however it can be challenging to scale them up. In this work, we propose an easily scalable approach to overcome these drawbacks. The commercially available AB2 room-temperature metal alloy Hydralloy C5 was modified by applying a wash coating-like methodology. The surface of the metal alloy was coated with a mixture of a conductive material like expanded natural graphite (ENG) or aluminum and the elastomeric ethylene-vinyl acetate copolymer (EVA). The performance of this modified metal alloy was investigated by in situ measurement of hydrogen capacity, heat dissipation and swelling-induced stress during 50 hydrogenation/dehydrogenation cycles. The coated metal alloy maintained a satisfactory hydrogen capacity with slightly improved heat dissipation. The swelling-induced stress behavior of the treated material was greatly improved. Especially the addition of a mixture of 10 wt% ENG and 10 wt% EVA allowed to completely compensate for the swelling-induced stress during hydrogenation.

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