Resumo

PERETTI, H.A. et al. Microstructure and hydrogen absorption behavior of Zr0.9Ti0.1Mn0.66V0.46Ni1.1 under electrochemical and gaseous media conditions. Lat. Am. appl. res. [online]. 2002, vol.32, n.4, pp.299-302. ISSN 0327-0793.

Rechargeable alkaline batteries of nickel-metal hydride have been widely studied due to the interest in replacing the cadmium electrode by metal hydride electrodes of low or null environmental impact. Recent developments include Laves phases based on ZrCr2 with multiple substitutions to improve electrode performance. In this work, results are presented on the electrochemical behavior of the Zr_0.9Ti_0.1Mn_0.66V_0.46Ni_1.1, its structural and morphologic characterization and its behavior under gaseous hydrogen absorption- desorption cycles. The pressure-composition-temperature (PCT) curves show a high hydrogen storage capacity (H/M ~ 3.4, where H/M = x is the number of H atoms per alloy formula unit in the metal hydride MH_x). It is also found a steep slope in the PCT isotherms, instead of a horizontal plateau corresponding to the two-phase equilibrium. Electrode activation was studied by voltammetric cycles, while the electrochemical capacity of hydrogen absorption was determined by galvanostatic measurements. For comparison, the Zr_0.9Ti_0.1CrNi alloy was also studied. The discharge capacities found are about 330 mAh/g for both alloys, but the activation is achieved faster for Zr_0.9Ti_0.1Mn_0.66V_0.46Ni_1.1 than for Zr_0.9Ti_0.1CrNi.

Palavras-chave : Batteries; metal hydrides; hydrogen storage; electrochemistry; over-stoichiometry.

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