Modification of Hydrogenation and Corrosion Properties of Hydrogen Storage Material by Amorphous TiCrFeCoNi HEA Layer

The effect of encapsulation of LaNi4.5Co0.5 powdered hydrogen storage material with approximate to 0.5 mu m thick, magnetron-sputtered amorphous film of TiCrFeCoNi high-entropy alloy (HEA) on functional hydrogenation parameters of the hydride electrode is discussed. The multicycle galvanostatic charge/discharge tests carried out in deaerated, 6 M KOH solution allow for determining specific capacity decrease, exchange current density of the H2O/H-2 system, and high rate discharge ability (HRD) of the hydride electrodes. Concentrations of individual constituents of the HEA in the particle coating determined by EDS analysis were practically the same (approximate to 20 at.%) as in the applied TiCrFeCoNi target material. The XRD phase analysis pointed out the amorphous structure of the HEA coating. The presence of HEA coating decreases capacity by 10-15 per cent, but increases exchange current density for H2O/H-2 system. The effect of HEA on capacity fade is ambiguous: low for 10-25 cycles (most probably due to effective corrosion inhibition) and distinct at long-term cycling (most probably due to galvanic effects resulting from mechanical degradation of particle surface). The presence of HEA coating considerably improves the HRD of the electrode material: for a discharge rate of 5C, the HRD coefficient becomes 4.6 times greater for HEA modified storage material.

Automated summary

The effect of encapsulating LaNi4.5Co0.5 powdered hydrogen storage material with a 0.5μm thick amorphous film of TiCrFeCoNi high-entropy alloy (HEA) on the functional hydrogenation parameters of the hydride electrode is discussed. The presence of the HEA coating decreases the capacity but increases the exchange current density for the H2O/H-2 system. The effect on capacity fade is uncertain but the HEA coating significantly improves the high rate discharge ability (HRD) of the electrode material.