Large-Scale Coating Methods for Improving Heat Transfer and Stress Management of Metal Hydrides

Abstract

Storing hydrogen in interstitial metal hydrides has several advantages. These include high volumetric capacity (50–100 kg/m3), fast kinetics, and safer conditions due to mild operating temperatures (<100 °C) and pressures (<50 bar). However, thermal management and stress development remain challenges to be overcome. There have already been promising methods to improve the performance of metal hydrides, but most are only proof of concept. They have only been investigated on a lab-scale with a few grams of sample. In this work, a commercially available AB2-metal alloy is coated with 10 wt% expanded natural graphite (ENG) and 10 wt% elastomeric binder. The focus is on methods that can easily be scaled up. Two methods (wash-coating and spray-coating) have been successfully applied to prepare hydride-forming materials on a kilogram scale. The performance of the coated material in terms of heat management, stress development, hydrogen capacity, and kinetics is evaluated to be over 50 cycles of hydrogen absorption/desorption. The results are confirmed by a larger-scale set of experiments with ≈0.5 kg of sample. The spray-coating method shows promising results, combining fast preparation, reasonable hydrogen capacity, and the potential to compensate for the bulk of the expansion stress.