Page 7 - Thesis_Oprysk_Volodymyr

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Chapter 5 investigates the influence of nano-additives on the electrochemical

characteristics of negative electrode materials for Ni-MH batteries. Particular attention is

given to nanopowders of the Ni 100-xPd x compositions (x = 0; 1; 5; 10 at.%) synthesized

via the chemical reduction method. Their phase composition, morphology, surface

chemical state (XPS), and electrochemical hydrogen-sorption properties were

determined. Additionally, the electrochemical behavior of composite electrode materials

based on the hydride-forming La 2MgNi 9 alloy with Ni 95Pd 5 and Ni 70Fe 30 nano-additives

was investigated.

The study demonstrates that nanocrystalline powders reduce charge transfer

resistance and provide a synergistic effect within "intermetallic compound – nano-

additive" composite electrode materials. The highest cycling stability was demonstrated

by the La 2MgNi 9 + Ni 95Pd 5 + Ni (carb.) (2:3:3) composite, yielding C max = 418 mAh/g

with S 30 = 76%. The highest capacity was achieved by La 2MgNi 9 + Ni 70Fe 30 (1:1),

reaching 492 mAh/g at S 30 = 59% (at a current density of 100 mA/g).

The obtained results deepen modern ideas about the regularities of the formation

of electrochemical hydrogen sorption properties of alloys depending on their phase and

elemental composition and can be used in the development of highly efficient Ni-MH

batteries electrode materials.

Keywords: hydrogen, hydrogenation, metal hydride, electrochemical properties,

cyclic stability, intermetallic compounds, Magnesium, rare-earth metals, nanomaterials,

Nickel, Nickel alloys, electrochemistry.