Nickel-hydrogen Battery Negative Research Of Key Technologies

The negative electrode of Ni/MH battery has the great important influence on Ni/MH battery. The key technologies of Ni/MH negative include the formula of negative, the choice of additives, the surface modification of electrode (active material), the choice of adhesive and conductive agent etc. On the basis of detailed review of research on prescription of MH electrode at home and abroad, effects of prescription of MH electrode on the performance of the negative electrode for Ni/MH battery were investigated. We researched that the performance on the AB5-type hydrogen storage alloy electrode which was added Co3O4 synthesised by solid-phase, and we explored the mechanism of its role; we also focused on the performance on the MH electrode which was modified by alkaline-duplicated treatment, different formulations of adhesive and conductive agent.The electrochemical properties of MH electrode with the addition of Co3O4 were studied. There were a few studies about Co3O4 as additive in MH electrode, we maked a detailed study. It showed that the MH electrode added Co3O4 formed a second discharge platform and the discharge capacity was improved. It also showed the addition of Co3O4 slowed down the oxidation process of alloy particles and improved the cycle stability of electrode. ICP, XRD, FTIR, and CV tests showed that Co3O4 worked by dissolution-deposition mechanism. First of all, Co3O4 dissolved in the electrolyte,and Co(OH)2 was oxidized of CoOOH which was highly conductive in the state of initial charge. We thinked that they were reversible conversion among Co3O4, Co (OH)2 and Co.The electrochemical properties of MH electrode with the alkaline-duplicated treatment were studied. Studies showed that Ni in the surface of hydrogen storage alloy after alkaline-duplicated treatment increased 3.95%, and the electrocatalytic activity of the Ni-rich layer was higher. The results of CV and EIS test indicated that the anode peak area of electrode was greater and the electrochemical reaction resistance was significantly reduced after alkaline-duplicated treatment. In short, the electro-catalytic properties of MH electrode was improved significantly by the surface treatment. The capacity, activation behavior, charge-rate efficiency and high-rate discharge performance of MH electrode were improved after alkaline-duplicated treatment; the discharge platform was higher than the untreated electrode with different discharge rate; and the discharge performance of alloy electrode at low temperature was improved significantly.The electrochemical properties of MH electrodes with different formulations of adhesive were studied. The results showed that the ability of charge fast and high-rate discharge enhanced; the performance of charge and discharge platform were better,compared D001 with D006.The charge platform of MH electrode with D006 formulation was longer, the second charge platform appeared lately, and the voltage of charge platform was lower at different discharge rate; the discharge platform was longer and the voltage of discharge platform was higher; the discharge performance of alloy electrode at low temperature was improved significantly. The combination of PTFE and CMC formed a network structure which could increase the effective surface area of electrochemical reaction, reduce the discharge current density and internal resistance and electrode polarization (electrochemical polarization and concentration polarization).But more HPMC inhibited the proliferation of H near the electrode, slowed the charging rate of the negative electrode reactions, increased the polarization of electrode.The electrochemical properties of MH electrodes with different formulations of conductive agent were studied. The results showed that the higher the amount of carbon added, the better performance of MH electrode was at a certain range. It was mainly due to the high surface area of carbon increased the real area of charge-discharge process of MH electrode,reduced the current density and polarization, improved the utilization of active material. But when the addition of carbon was fixed, the higher the amount of Ni added, the worse performance of MH electrode was.