Investigation of multilayer Ni-Mg-Ni-Mg film structures and development of a prototype of film metal-hydride hydrogen accumulator

The structural and sorption/desorption characteristics of multilayer Ni-Mg-Ni-Mg films (38/37 Ni/Mg layers with a total thickness up to 45 µm) deposited on both small-sized and extended tape (up to 40 m) polyimide substrates by magnetron sputtering have been studied. A trend was observed between the growth of hydrogen mass content in the films and the increase in the number of sorption/desorption cycles which is accompanied by the increase in MgH2 phase from 53 wt.% to 78 wt.% and Mg2NiH4 phase from 0.1 wt.% to 19.9 wt.%. Long-length samples (5 m and 40 m) of Ni-Mg-Ni-Mg film structures as metal hydride hydrogen accumulators have been tested. A reversible mass content of hydrogen they contain has exceeded 4 wt.% at an outlet pressure of 1 atm. Based on the conducted research, a prototype of film metal-hydride hydrogen accumulator was elaborated, then manufactured and tested. The design of the developed prototype and the results of its tests are presented. With stored hydrogen of 3.6 g, specific gravimetric energy capacity of the prototype accumulator was 400 Wh/kg, and specific volumetric energy capacity was 600 Wh/L.