Studies on the electrochemical properties of MlNi Co Al hydride 4 . 3 2 x x 0 . 7 alloy electrodes

In this paper, the electrochemical properties of MlNi Co Al electrode alloys, including high rate dischargeability, exchange 4.32x x 0.7 current density I , limiting current density I , and diffusion coefficient of hydrogen in the hydride D by means of linear polarization, 0 L a anodic polarization, and electrochemical impedance spectroscopy were systematically studied. The results indicate that, with the increase of Co content, the cyclic stability is improved markedly, which agrees with previous investigation. However, activation becomes more difficult, and the high rate dischargeability decreases. The linear polarization and anodic polarization results suggest that the exchange 21 current density I and limiting current density I decrease from the 395 (x50) to 33 mA g (x51.3) and from 2263 (x50) to 308 mA 0 L 21 g , respectively. The electrochemical impedance spectroscopy result also reveals that the diffusion coefficient of hydrogen in the alloys decreases rapidly with the increase in Co content in MlNi Co Al hydride alloy electrodes.  1999 Elsevier Science S.A. All 4.32x x 0.7