Abstract
The capacitive and kinetic parameters of hydride electrodes obtained on the basis of single-phase LaNi5-xGex alloys (x = 0.3 and 0.6) were related to their corrosive properties. The content of the article is important from the point of view of the improvement of LaNi5 type materials for hydrogen energy storage used as anodes in NiMH batteries. The presence of large amounts of germanium (10% at.) in the alloy results in much less surface degradation compared to the low-germanium alloy (5% at.), which, on the one hand, leads to an improvement in the resistance of the high-germanium LaNi4.4Ge0.6 alloy to long-term cycling, but on the other hand, contributes to lower hydrogen absorption by this material. The maximum discharge capacity of 293 mAh g−1 was obtained for the low-germanium alloy using a charge/discharge current density of 185 mA g−1. The studied electrode also shows a lower tendency to self-discharge and a clearly higher exchange current density.
Highlights
The gradual depletion of conventional fossil fuels and their negative impact on the natural environment (CO2 emissions into the atmosphere, global warming), make it necessary to seek new sources of energy
The properties of LaNi5 systems can be improved by modifying the chemical composition and selecting the appropriate alloy components for which the alloy corrosion process occurring during the discharge of the electrode is partially reversible in the charging process or, alternatively, by finding anode materials with better kinetics of charging/discharging processes
There are no clear and universal criteria for selecting atoms for substitution, but one of the most noteworthy observations from these studies is the modification of the LaNi5 material by replacing nickel or lanthanum with larger atoms [31,32]. This can lead to a larger size of interstitial voids and a higher number of interstitial void occupied by hydrogen and, as may be expected, higher hydrogen storage capacity for modified version of material as compared to basic LaNi5. Another element that could be used as a substitute for Ni that seems to have a beneficial effect on hydrogen storage properties is germanium
Summary
The gradual depletion of conventional fossil fuels and their negative impact on the natural environment (CO2 emissions into the atmosphere, global warming), make it necessary to seek new sources of energy. There are no clear and universal criteria for selecting atoms for substitution, but one of the most noteworthy observations from these studies is the modification of the LaNi5 material by replacing nickel or lanthanum with larger atoms [31,32] This can lead to a larger size of interstitial voids and a higher number of interstitial void occupied by hydrogen and, as may be expected, higher hydrogen storage capacity for modified version of material as compared to basic LaNi5. The aim of this study is to investigate the effect of partial replacement of Ni with Ge in hydride electrodes obtained on the basis of single-phase LaNi5-xGex alloys (x = 0.3, 0.6) on the values of the hydrogen capacity and the absorption/desorption kinetics in relation to the corrosion properties of the studied alloys
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