Analysis of the activation mechanism of hydrogen storage alloy negative electrodes modified by nickel particles

In the case of Ni-MH batteries using fine nickel particles-added hydrogen s torage alloy negative electrodes, the initial activation of the negative el ectrodes was promoted. From electrochemical impedance analysis of the negat ive electrodes and specific surface area and oxygen content measurement of the added fine nickel particles, the mechanism of this phenomenon was presu med to be as follows: 1) Minute rough parts on the surface of the nickel particle act as active s ites for charge/discharge reactions. Rapid hydrogen transfer takes place be tween the active sites and the hydrogen storage alloy. 2) Pulverization of the alloy occurs due to the hydrogen absorption into th e alloy, and new active sites are formed on the alloy surface. 3) Therefore, the initial activation of the negative electrode is promoted by addition of the ne nickel particles.