The synthesis and properties of nanocrystalline electrode materials by mechanical alloying Original Research Article

In this work, we have experimentally studied the structure and electrochemical properties of nanocrystalline TiFe- and LaNi5-type alloys. These materials were prepared by mechanical alloying (MA) followed by annealing. The properties of hydrogen host materials can be modified substantially by alloying to obtain the desired storage characteristics. It was found that the respective replacement of Fe in TiFe by Ni and/or by Cr, Co, Mo, Zr improved not only the discharge capacity but also the cycle life of these electrodes. In the nanocrystalline TiFe0.25Ni0.75, powder discharge capacity up to 155 mA h g−1 was measured (at 40 mA g−1 discharge current). On the other hand, a partial substitution of Ni by Al or Mn in LaNi5−xMx alloy leads to an increase in discharge capacity. The alloying elements such as Al, Mn and Co greatly improved the cycle life of LaNi5 material. For example, in the nanocrystalline LaNi3.75Mn0.75Al0.25Co0.25 powder, discharge capacity up to 258 mA h g−1 was measured (at 40 mA g−1 discharge current). The studies show, that electrochemical properties of Ni–MH batteries are the function of the microstructure and the chemical composition of used electrode materials.